regional code of practice of west and central africa

REGIONAL CODE OF PRACTICEFOR REDUCED-IMPACT FOREST HARVESTING

IN TROPICAL MOIST FORESTSOF WEST AND CENTRAL AFRICA

A

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© FAO 2004

FOREWORD

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M. Wulf KillmannDirector

Forest Products and Economics DivisionForestry Department

FOREWORD

The United Nations Conference on Environment and Development, held in Rio in June 1992, raisedawareness amongst many countries of the importance of forests to their economic, social andenvironmental development.

Since the last World Summit on Sustainable Development, convened in Johannesburg in 2002,several initiatives have been taken to reinforce forest institutions and modify legislation in order toprovide a regulatory framework for forest harvesting.

At the same time, the conservation and rational utilization of West and Central Africa's forestresources have been under increasing international scrutiny.

The promotion of environmentally sound forest harvesting practices has encouraged manycompanies to embrace the concept of reduced-impact harvesting, although implementation has beenlimited. One of the reasons for this was the lack of guidelines on reduced impact harvesting adaptedto regional and sub-regional conditions.

To fill this gap, a component of the project: «Sustainable Forest Management in African ACPCountries», conducted by the FAO Forestry Department in partnership with the European Communityfrom 2000 to 2003, has focused on timber harvesting in tropical forests.

The result is this publication, Regional Code of Practice for Reduced-Impact Forest Harvesting inTropical Moist Forests of West and Central Africa. The study is directed at forest authorities of membercountries, practitioners on the ground and all partners who have joined forces to promote sustainableforest management in the region. This regional code is intended to set guidelines for theimplementation of reduced-impact harvesting concepts in the region and to serve as a source ofreference for member countries as they shape their own national regulations.

We hope that this code will contribute to implementing improved forest harvesting practices in theRegion and will advance the cause of sustainable forest resource management.

ACKNOWLEDGEMENTS

This publication was prepared under the Sustainable Forest Management in African ACP Countriesproject of the FAO-EC Partnership Programme. It is the fruit of collaboration involving manyorganizations associated with tropical forestry and forest management in Africa. After noting theirconvergent interests and activities in forest management in the region, FAO’s Forest Products andEconomics Division and ADIE agreed in 2001 to combine efforts and prepare a regional code onforest harvesting. Its conception and formulation were directed by a steering committee chaired byFAO and made up of representatives of ADIE, ATIBT, TFF and WWF (members) and of ATO, Cirad-Forêt, FORAFRI, ITTO, IUCN, USDA (advisers). Our sincerest thanks must first go, therefore, to theseinstitutions and to their delegates who were so keen to share their expertise and enthusiasm with us.

The preliminary version of this Code was drafted by Jean Estève who set the general guidelines forthe body of technical material relating to forest harvesting in the region. The chapters on wildlifemanagement and relations with local communities were provided by ADIE (FORM). The finalizationprocess benefited from changes decided by the drafting committee chaired by FAO and by commentsand suggestions received from many guest reviewers. Henning Fath edited the text and gave theillustrations an ordered structure and a content that reflects current practices, their damaging impactand improved practices. Sinclair Gibbs translated the original French text. Ivan Grifi saw to theuniformity of illustrations and the coherence of graphic design. Joachim Lorbach of FAO’s ForestProducts and Economics Division coordinated all activities of the Development and Promotion ofImproved Harvesting and Economic Practices component of the project.

Pilot studies of current harvesting practices were carried out in four countries of the region, withFAO recruiting national experts in most cases: Messrs Dipapoundji and Boute-Mbamba in the CentralAfrican Republic; Boundzanga, Bouta and Matingou in the Republic of Congo; and Oddom inGhana. Their work accomplished under difficult field conditions was greatly appreciated, all the moregiven the usefulness of its results.

We are grateful for the support received from the services of the region’s national forest authoritieswho helped us recruiting the experts. We should also like to thank those forest companies thatcooperated with FAO and allowed us to conduct our pilot studies on their concessions.

This undertaking involved many people of different cultural and professional backgrounds. It wastheir shared determination to bring about improved practices and reduce the negative impact of forestharvesting that inspired them to seek consensus whenever differences arose. Our special thanks goto these people whose collaborative effort transcended all cultural and corporate boundaries.

ACKNOWLEDGEMENTS

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TABLE OF CONTENTS

FOREWORD III

ACKNOWLEDGEMENTS V

ABBREVIATIONS XI

PREFACE XIII

1 INTRODUCTION 11.1 Purpose 21.2 Approach 21.3 Scope 21.4 Role of partners 31.5 Design and structure of the Code 41.6 Impact of harvesting in a regional context 4

1.6.1 Potentially damaging practices 51.6.2 Environmental and social impacts 6

2 SUSTAINABLE MANAGEMENT OF PRODUCTION FORESTS 102.1 Forests and their multiple functions 122.2 International context 122.3 Planning sustainable management and forest harvesting 14

2.3.1 Strategic (long-term) management plan 142.3.2 Tactical (mid-term) management plan 162.3.3 Annual plan of operation or coupe 17

3 PRE-HARVEST PLANNING 183.1 Mapping tools 203.2 Geographic Information System - a management tool 213.3 Harvest survey 22

3.3.1 Survey criteria 223.3.2 Description of the pocket inventory 223.3.3 Description of the inventory by systematic survey lot 243.3.4 Impact of survey activities on the forest 26

3.4 Non-harvest areas 263.4.1 Delimitation 263.4.2 Special precautions 26

3.5 Tree spotting and marking – planning and optimizing the extraction layout 273.5.1 Layout of the secondary road network 273.5.2 Preparing the harvesting block – planning and layout of skid trails and landings 28

3.6 Producing the operational harvesting map 29

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4 PLANNING AND CONSTRUCTION OF ROAD NETWORK, 30DRAINAGE STRUCTURES AND WATER CROSSINGS

4.1 Road classification 314.2 Characteristics of the road network 324.3 Road characteristics 32

4.3.1 Cross section 334.3.2 Horizontal alignment 334.3.3 Longitudinal profile 34

4.4 Road construction 354.4.1 General rules 354.4.2 Layout 364.4.3 Clearing 364.4.4 Blading (earthwork) 364.4.5 Sunlight exposure 374.4.6 Roadway compaction and improvement 37

4.5 Drainage: drains, outlets, culverts and box drains 374.5.1 Avoiding water penetration 384.5.2 Evacuation of rainwater runoff: side drains, outlets and culverts 384.5.3 Drainage of roadway structure 39

4.6 Crossing watercourses: drifts and bridges 404.6.1 Drifts 404.6.2 Bridges 40

4.7 Road maintenance 434.7.1 Regular maintenance 434.7.2 Resurfacing 434.7.3 Other maintenance operations 43

4.8 Impact of road construction 444.9 Recommendations 44

5 IMPLEMENTING HARVEST OPERATIONS 465.1 Controlled felling 50

5.1.1 Preparation 505.1.2 Controlled felling techniques 515.1.3 Felling safety 545.1.4 Felling impact 565.1.5 Recommendations 56

5.2 Topping and butt trimming 575.2.1 Topping 585.2.2 Butt trimming 585.2.3 Recommendations 58

5.3 Extraction 605.3.1 Extraction techniques 605.3.2 Characteristics of skid trails 625.3.3 Construction of skid trails and landings 625.3.4 Extraction impact 655.3.5 Recommendations 65

5.4 Cross-cutting, marking and preserving 675.4.1 Cross-cutting 67

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5.4.2 Log marking 695.4.3 Log preservation 69

5.5 Loading and transport 715.5.1 Loading 725.5.2 Transport and unloading 73

5.5.2.1 Road transport 735.5.2.2 Water transport 74

6 POST-HARVEST OPERATIONS 766.1 Rehabilitation of skid trails and landings 786.2 Road closure 786.3 Cleaning of watercourses 78

7 WILDLIFE MANAGEMENT 807.1 Practical recommendations – the wildlife management committee 837.2 Identification and development of alternative resources 857.3 Pilot projects 86

8 LAYOUT, CONSTRUCTION AND HYGIENE OF CAMP FACILITIES 88

9 EMPLOYMENT, QUALIFICATION AND TRAINING OF PERSONNEL 92

10 SAFETY MEASURES 9410.1 General principles 9810.2 Obligations and responsibilities 9810.3 General safety measures 9910.4 Safety rules for harvesting operations 99

10.4.1 Felling with chainsaw 9910.4.2 Cross-cutting with chainsaw 10010.4.3 Extraction by skidder 10110.4.4 Loading and transport 101

10.5 Safety rules for chemicals and petroleum products 102

11 HARVEST CONTROL, MONITORING AND ASSESSMENT 10411.1 Control and monitoring of harvesting 10611.2 Internal and external assessment 106

12 MAINTENANCE AND REPAIR OF EQUIPMENT 10812.1 Workshop and garage 11012.2 Storage of fuel and lubricants 11012.3 On-site servicing 11012.4 Harvesting waste 110

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TABLE OF CONTENTS

CHAPTER 1

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13 RELATIONS WITH LOCAL COMMUNITIES 11213.1 Present situation 114

13.1.1 Institutional framework 11413.1.2 Expectations of local communities 114

13.2. Practical recommendations 11413.2.1 Steps for developing social aspects of sustainable forest management 11413.2.2 Prerequisites 11513.2.3 Key factors for successful collaboration 11513.2.4 Consultation of the local community: social study 11613.2.5 Coordinating committee 11613.2.6 Proposed rights and obligations 117

GLOSSARY 118

BIBLIOGRAPHY 125

SOURCE LIST 134

TABLE OF CONTENTS

ATIBTInternational Technical Tropical Timber Association

ATOAfrican Timber Organization

CEFDHACConference of the Central African Tropical Moist Forest Ecosystems

CIFORCentre for International Forestry Research

CIRAD-ForêtForestry Department of the International Cooperation Centre on Agrarian Research for Development

COMIFACConference of Ministers in Charge of Forests in Central Africa

CTFTTechnical Tropical Forestry Centre (previous name of CIRAD-Forêt)

FAOFood and Agriculture Organization of the United Nations

FORAFRIAfrican Forests Project of the French Ministry of Foreign Affairs

GISGeographic Information System

GPSGlobal Positioning System

ILOInternational Labour Office

ITTOInternational Tropical Timber Organization

IUCNWorld Conservation Union

NGONon-governmental organization

RILReduced Impact Logging

TFFTropical Forest Foundation

USDAUnited States Department of Agriculture

ABBREVIATIONS

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PREFACE

For many countries of tropical and equatorialAfrica, the harvesting of forest products in theirclosed tropical moist forests, especially timber, isan activity that has ecological, sociological andeconomic significance:• ecological because penetration of forest areas for

harvesting purposes is generally the only or themain form of forest intervention, apart fromdisruption by natural events;

• sociological because forest enterprises are the mainsource of private sector employment in the interiorof these countries and help retain local populationswithin the provinces, thus curbing ruraloutmigration;

• economic because timber often ranks second ascontributor to the balance of trade and exports.

Forestry activity is no longer restricted to theproduction of timber; there is now widespreadrecognition of the paramount role of forests inmaintaining biodiversity, in providing non-woodproducts, in safeguarding cultural values, insequestering carbon and in mitigating climatechange.

This further complicates harvesting operationswhich now need to take the many differentfunctions of the forest into account – operationsthat are already inherently complex as they aredependent on an array of factors: availability oftree stocks, terrain, climate, soil, laws andregulations, productivity and costs, availabilityand competence of workforce and danger offorest work. The way for forest harvesting to meetthe requirements of sustainable management, toaddress the multi-functionality of forest land andto ensure commercial profitability is to applymethods of reduced-impact logging (RIL).

Contrary to popular belief, this concern for«soft» harvesting and minimized negative impacton the environment is not recent. Back in 1947,Gaston Grandclément was already calling for achange in the way the equatorial forest wasbeing harvested, pointing out that the practice ofselectively harvesting precious timber specieswithout order, method or concept of sustainedyield could no longer persist. The time when alogging operator worked without a pre-established plan or detailed survey and restrictedhis efforts to the more accessible parts of aconcession had to end. The annual cut needed tobe commensurate with sustained yield in theharvesting area, which called for a careful pre-harvest survey of available timber stocks. Suchan inventory by the concessionaire would givethe forest authorities a precise idea of theeconomic value of existing forest formations.

Grandclément's ideas were graduallyintroduced into Africa’s forests over the following40 years, with many enterprises planning theiroperations in a rational manner. Then, forreasons unknown, these good practicesvanished, to be replaced by «the woodcuttersand landclearers».

More recently, we have heard urgent calls toput into practice «all that is known but so seldomapplied« (Bruijnzeel and Critchley, 1994). Suchis the aim of this Regional Code: to provide theinformation needed to implement forestharvesting practices that are bothenvironmentally sensitive and economicallyviable.

PREFACE

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CHAPTER 1

«Its overall purpose is to promoteharvesting practices that will improvestandards of utilization, reduceenvironmental impacts, help ensure thatforests are sustained for futuregenerations and improve the economicand social contributions of forestry as acomponent of sustainable development.»(FAO Model Code of Forest HarvestingPractice, 1996).

INTRODUCTION

1.1 Purpose

1.2 Approach

1.3 Scope

1.4 Role of partners

1.5 Design and structure of the Code

1.6 Impact of harvesting in a regional context1.6.1 Potentially damaging practices1.6.2 Environmental and social impacts

INTRODUCTION

1.1 PURPOSE

This model Regional Code of Practice forReduced-Impact Forest Harvesting is intendedprimarily to serve as a reference document fortropical African countries engaged in or aspiringto the sustainable management of their closedmoist forests. It seeks to provide a range ofstandards, guidelines and rules that will helppublic- and private-sector foresters to adoptappropriate practices. Its aim is thus to functionas:• an interim working paper that can be easily

amended or adapted to specific country conditionsuntil respective national codes have been drafted;

• an effective instrument for the implementation ofsustainable management of closed moist forests;

• a compendium of guidelines that will facilitate forestactivities compatible with international directivesand principles, regional criteria and indicators, andprocedures of certification;

• a series of guidelines that will help conservebiological diversity, forest regeneration and wildlifeprotection;

• a tool for promoting enhanced productivity,sustainability and economic viability of forestharvesting;

• a tool for promoting improved living conditions andsafety of the workforce;

• a tool for promoting improved relations betweenlogging companies and local communities.

The Code concentrates more on «what needsto be done» than on «how this needs to bedone», and will not be directly applicable to allsituations and all countries, given their numberand variety. The guidelines presented willtherefore need to be adapted to individualsituations, but the Code does nevertheless laydown important general principles forenvironmentally sound forest harvesting.

It is not designed as a source of reference onforestry techniques as such, nor as a manual onthe use of harvesting tools and equipment.

1.2 APPROACH

This Code draws upon the FAO Model Code ofForest Harvesting Practice of 1996 and is drivenby the fundamental principle «that it is possible toconduct forest harvesting operations in ways thatare consistent with the needs of sustainability»(FAO, 1996) and that significantly reducenegative impact.

«A necessary condition for the sustainablemanagement of forests is that utilization, and theactivities associated with it, must not compromisethe potential of forests to regenerate properlyand to provide products and services that areessential for the well-being of both current andfuture generations. This condition can be met byfollowing good harvesting practices, althoughdoing so may not be easy» (FAO, 1996).

Compliance with this fundamental principlerequires:• comprehensive, accurate and detailed planning of

harvest-related operations;• effective conduct, control and monitoring of

harvesting operations by experienced personnel;• post-harvest assessment to identify necessary

improvements in methods and techniques;• a trained, competent and motivated workforce;• the personal commitment of all company

employees.

This document will examine each of theseconditions in detail in order to enable readers tofind solutions to their specific constraints.

1.3 SCOPE

As its name suggests, the Regional Code ofPractice for Reduced-Impact Forest Harvesting inTropical Moist Forests of West and Central Africafocuses primarily on:• the African «region» in a broad sense,

encompassing the tropical countries of West andCentral Africa and their specific characteristics;

• timber harvesting because of its potential damageto the environment. Some guidelines on silvicultureand wildlife protection are also included;

• closed natural production moist forests, althoughsome of the guidelines also apply to protection andplantation forests.

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1.4 ROLE OF PARTNERS

Each of the main actors of sustainablemanagement and reduced-impact harvesting hasspecific responsibilities and functions. Theirconcerted involvement is central to the successfulapplication of the Code.

Government and forest administration• Formulate forest policy, legislation and regulation;

provide education and training; furnish appropriatenumber of competent supervisory staff, thusproviding for the sustainable management and useof forest resources for the benefit of the entirenational community;

• help small forest enterprises and local communitiesimplement sustainable forest management and RILat their respective levels;

• evaluate and approve management andoperational plans;

• supervise and monitor in the field the effectiveimplementation of regulations, contract terms andplans, together with training activities;

• Ensure that all operators are treated equally andpenalize any failure to observe legal andregulatory obligations.

Logging companies• Prepare and draw up annual operational

harvesting plans in accordance with the guidelinesof the management plan and RIL;

• minimize impact on the environment and residualstand by applying RIL practices;

• supervise and assess conformity of harvestingactivities with guidelines;

• optimize harvesting and thus reduce pressure on theforest and the annual felling area (by using morecommercial species and increasing recovery levelat harvesting and processing);

• train or facilitate the ongoing training of theworkforce in RIL techniques;

• improve safety at work.

Local communities• Participate actively in raising the awareness and

understanding of local populations of thesustainable management of natural resources, witha special focus on the younger members of thecommunity;

• distribute equitably forest resources and benefitsderived from their utilization;

• respect legislation and regulations related tohunting;

• use forest products sustainably, in particular non-wood forest products and wildlife;

• use community forests sustainably in accordancewith management plans and RIL guidelines;

• limit slash-and-burn cultivation.

Non-governmental organizations• Sensitize actors and local communities to

sustainable resource management, RIL guidelinesand the promotion of this Code, and provide orassist in related training;

• help local communities draw up and implementplans for the use and management of communityforests;

• finance and conduct pilot activities or field researchon the improvement of harvesting techniques thatare compatible with sustainable forestmanagement.

Training and research institutes• Conduct research and projects aimed at improving

RIL techniques and tools;• conduct research and projects aimed at facilitating

implementation of RIL;• train or help train all actors and sensitize them to

sustainable management and RIL;• participate in the improvement, promotion and

dissemination of standards, criteria and indicatorsrelated to sustainable management and RIL.

Donors• Sensitize governments and assist them in adopting

a forest policy and code that facilitate sustainablemanagement and RIL;

• help logging companies finance sustainablepractices, especially proper management planningand RIL;

• subsidize or encourage the subsidization ofactivities for the protection of biodiversity andwildlife not under the moral or financialresponsibility of the logging companies;

• finance or help finance training and researchinstitutes.

INTRODUCTION

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1.5 DESIGN AND STRUCTURE OFTHE CODE

The Regional Code is tailored after the FAOModel Code of Forest Harvesting Practice to thespecific characteristics and conditions of theclosed tropical moist forests of Africa. The latteris therefore a primary source of reflection andreference. It also draws widely upon a variety ofpublications, including (in random order) the RILGuidelines and Code of Logging Practice ofVanuatu (Forest Service Vanuatu, 1998), theCode of Practice for Forest Harvesting in Asia-Pacific (FCAP, 1999), and the PracticalManagement Plan for Natural African ProductionForests (ATIBT, 2001).

The Regional Code also takes into account theresults of field-driven initiatives, case studies andtrials conducted in West and Central Africa.

The Code comprises 13 chapters:The first chapter – the introduction – states the

objectives, approach and scope of thedocument, outlines the respective roles of thedifferent actors in forest harvesting, explains howthe contents are thematically structured, anddescribes the impact of forest harvesting in aregional context.

The second recalls the overriding principles ofsustainable management of production forests,the various functions of the forest, the criteria forits sustainability, the international contextsurrounding it and the manner in whichsustainable management translates into short-,medium- and long-term management planning.

The following two chapters deal with thepreparation of harvesting activities (pre-harvestplanning, including planning of non-harvestareas), and planning and construction of roads,drainage structures and watercourse crossings.

The fifth chapter deals with the actualharvesting operations: felling, topping, skidding,cross-cutting, loading and transport.

The sixth looks at post-harvest activities aimedat mitigating damage caused to skid trails, roadsand watercourses, and at preventing subsequentdeterioration.

The following chapter looks at conditions formanaging wildlife on and around loggingconcessions.

Then several chapters provide guidelines onthe planning and hygiene of logging camps, theservicing and repair of equipment, workforcequalification and training, and safety measures.

The document also features an importantchapter on the principles of control, monitoringand evaluation of harvesting, which serve toexamine the extent to which planning and RILguidelines have been observed duringoperations.

Finally the Code identifies relations betweenforest harvesting and local communities, beforeconcluding with a glossary, bibliography andsource list.

1.6 IMPACT OF HARVESTING IN AREGIONAL CONTEXT

Like any industrial activity, forest harvestingimpacts on the natural and social environment.The creation of infrastructure, felling and thepenetration of machinery all damage the forest tovarying degrees, depending on intensity andpractice. Intercontinental comparison (cf. Table1) suggests that the low intensity of highlyselective harvesting in Africa causes minimaldamage. However, inappropriate practices – stillfairly widespread because of lack of know-how,regulation and control – can be most detrimentalto the well-being of the workforce and localpopulation, to environmental sustainability (foreststructure, remaining stand and soil) and toefficiency.

Table 2 presents selected results from a pilotstudy in Gabon which shows that specificimpacts can reach alarming proportions, evenwith moderate absolute values.

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Africa America S-E Asia

No. of stems extracted/ha

1-3 2-5 6-20

Commercial volume extracted (m 3/ha)

5-30 10-50 50-150

Damaged stand (%) 10-15 25-40 50-60Table 1. Estimated average impact of harvesting on stands

1.6.1 Potentially damaging practices

Hyperselective harvesting («skimming»)Premium grade roundwood of the most sought-afterspecies is transported over very large distances,generating costs only rendered viable by the highprices paid on the international market. In contrast,species and grades that are not exportable, butnevertheless with commercial value, are usually leftin place. The sawing of lower quality logs producesa very high proportion of discarded wood, asproduction costs can only be offset by exportingpremium quality sawnwood. If there is no localprocessing plant, then only premium species arefelled and only one quality trunk recovered fromeach tree, to be further cut during conversion.

Such hyperselective harvesting of a handful ofspecies (Karsenty, 2002) can jeopardize thesustainability of polycyclic systems. Theextraction of a lower volume of timber thanplanned, means that new harvest areas areconstantly sought and higher market demand fornew species induces foresters to repeatedly re-enter already harvested blocks without regard tofelling cycle. In terms of cubic metre of recoveredtimber, skimming affects a large surface areaand incurs high costs for road construction,extraction infrastructure and productionoperations. In many countries of the regionexcessive cutting cycles have already degradedforest structure and impoverished biodiversity.

The pressure that this practice applies to theregion's forest resources justifies demanding thatoperators intensify (within the limits of cuttingpotential) and diversify their initial harvesting inorder to curb frequent re-entry, and apply thereduced-impact harvesting practices that are setout in this Code.

Failure to implement the harvesting plan on thegroundThe forest industry is increasingly integratingsurveying (harvest layout, tree inventory andmarking) into its planning system in order torecord trees to be harvested and those to beprotected and to establish a spatial structurefacilitating extraction. However, specifications arenot fully applied in the field, either because notproperly conveyed to felling and extraction crewsor because the workforce has not been correctlytrained in RIL practices. Field crews need to begiven explanatory maps and clear instructions toensure safe, careful and efficient harvestingpractices, if disparity between operationalplanning and actual delivery is to be removed.

Inadequacies in road planning and constructionForest roads sometimes cross rugged terrain,where earthcut, earthfill and culvert works takeup too much space and are not sufficientlystabilized. Steep roads are sometimes withoutdrains or culverts to evacuate rainwater, causingrapid erosion of roadway that can only beremedied by costly repair.

Forest roads on clayey soil are amply clearedfor sunlight exposure and, although thisconsiderably reduces the time needed for theroad to dry off and become useable, the clearedwidth could often be narrowed by installing moreand better drainage structures.

The construction of low density road networksusually results in skidding over long distances alongtrails resembling secondary roads not designed orbuilt to meet adequate technical standards withrespect to their accessibility. The planning andbuilding these roads in advance should be aprerequisite for reduced-impact harvesting in orderto provide an effective spatial configuration thatcan be maintained throughout operations.

Uncontrolled felling and wasteful topping andbutt trimmingEven companies that apply RIL principles whenplanning their operations have not yettransmitted these principles to their felling crews.This often results in uncontrolled felling with noundercut or backcut, and the inefficient timberrecovery during topping and butt trimming. Treesfall in the wrong direction, rendering pre-felling

INTRODUCTION

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Damage to stand – felling and extraction

Volume of trees (number of trees)

Number of trees felled 2.75 trees/ha

Volume of timber removed 18 m3/ha

Volume of timber extracted 10 m3/ha

Damage per hectare 13 m3 (5.5)

Damage per felled tree 5 m3 (2.0)

Damage per m 3 wood in boles 0.70 m3

Damage per m 3 of wood in logs 1.30 m3

Table 2. Damage to stands caused by felling and extraction

preparations worthless and obstructing extractionas marked trails are partly blocked by felledtrees. The resulting damage to the felled tree,remaining stand and soil is considerable andtimber recovery relatively low.

Excessive crawler pre-skidding and skiddingCrawler tractor operators often fail to understandthat their role is to help the extraction process.Instead they operate in a forest area as thoughthere were no forest, opening trails that wheeledtractors could just as easily open and not onlyextracting trunks by levelling a whole vicinity butthen proceeding to haul them all the way to thelanding, causing serious damage to remainingstand and soil.

Sometimes pre-cleared skid trails no longerprovide access, as trees have fallen in the wrongdirection. Crawler operators then open new trailswhich, coupled with to the pre-marked network,affect an excessive surface area and underminethe efficiency of extraction.

Wasteful conversion at the landingTrunks are converted into logs at landings, thennumbered and recorded. Depending oncompany or purchaser requirements, the butt of atrunk with buttresses is often removed, leading tohigh loss of timber and serious implications fortimber recovery.

Landings are often located near watercoursesor on steep terrain, causing serious erosion andwatercourse sedimentation. These negativeconsequences are compounded when debris fromlandings is cleared towards the earthfill slope.

Lack of monitoring, control and impactassessmentHarvest planning systems, which are beingapplied by an increasing number of companies,provide the wherewithal to track timber flowthroughout production, from felling to landing.Overlooked trees or stems are spotted and lost ordamaged trunks are noted, which providescomprehensive feedback on harvesting efficiencyin terms of timber recovery. However, fewcompanies regularly evaluate the efficiency oftheir extraction process or the damage caused byfelling and extraction in terms of cleared surfacearea and harm to remaining stand and soil.

1.6.2 Environmental and social impacts

The following structural/environmental and socialindicators are used to measure and assess impacts:

Structural and environmental impactsWhatever methods and machinery are used,harvesting operations will inevitably affect theforest structure and disrupt its vegetation and soil:total deforestation to clear for roads, landingsand logging camps, and disruption during fellingand extraction according to number of treesfelled and practices employed.

The following informative figures regardingsurface area affected by harvesting, are derived

from five pilot studies in the region:By way of comparison, the area affected in

Guyana and Brazil for extraction of 10 stems/hawas 32 and 35 percent respectively (Karsenty et

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Impact criteria (and subjects)

Sustainability (structure, remaining stand, soil)

Well-being (workforce)

Well-being (communities)

Area cleared for roads, trails and landings

Remuneration Unsustainable secondary uses

Number of trees and extracted volume Canopy opening

Training and instruction

Synergy/conflict with subsistence or remunerative activities

Timber recovery SafetyLodging

Damage to remaining stand and soil

Nutrition and transport

Table 3. Matrix of impact indicators

Rep.of Congo 1997

Rep.of

Congo 2003

Cameroon Gabon Central African Republic

Volume extracted (m3/ha)

6 7 5 10 50

Road network

1.7 4.0* 1.5 1.6 2.0

Landings 0.2 0.1 0.3 - 1.5

Skid trails 2.7 - 3.1 6.8 7.4

Canopy opening

3.8 0.6 2.0 9.5 13.0

TOTAL 8.4 % 4.7 % 6.9 % 17.9 % 23.9 %

* Including skid trails.

Table 4. Surface area affected by infrastructure and harvestingas percentage of worksite or cutting unit area

Maître, 1994). This incremental damage to thestand has led many foresters to call for alimitation of harvest intensity as a prerequisite forsustainable management.

Stand damage concerns in particular smalltrees with a DBH of 10 to 20 cm, which have thehighest mortality. Damage during felling is fromcrown breakage for larger trees and generaldebranching for smaller trees. The damage isproportionate to the number of trees felled, thesize of their crowns and the felling methods used.

Extraction causes injury to trunks and roots oflarge stems but does not generally uproot smalltrees. On the other hand, it can seriously affectthe structure of the forest cover, depending on themethod of extraction used.

Major soil damage caused by repeatedpassage of machinery takes the form ofcompaction, rutting and scalping with the removalof topsoil. The direct consequences are erosionand leaching from rainwater, and more or lesscomplete and rapid sterilization which slows orprevents forest regeneration.

Impact on the retention and absorption of waterMuch rainfall hits the canopy before reaching thesoil and filtering through the forest litter. Forestharvesting however creates openings which allowmore water to reach the soil since less will beintercepted by the canopy. This results in highersoil moisture levels in forest clearings despitehigher ground temperature and evaporation(Bruinjzeel and Critchley, 1994). This is not amajor problem if soil absorption capacity isretained, but where the forest litter has beenremoved or the soil compacted by the constructionand use of skid trails and landings, the absorptioncapacity becomes insufficient, triggering runoff,erosion and leaching. Flat sandy terrain is clearlyless vulnerable than steep clayey terrain.

Impact on erosion and sedimentationSurface erosion in an untouched forest, protectedby litter and root cover, has one of the lowestlevels for tropical soils, but erosion andsedimentation increase after forest harvesting(Bruinjzeel and Critchley, 1994). As rainsplashes onto exposed soil, particles becomedetached and displaced, especially on steep,

compact ground, and can cause significant build-up of sediment that obstructs natural or man-made waterflow.

At the same time, erosion rills form alongroadways and side drains when erosion andspeed of runoff reach a certain level. These canthen widen and deepen into full-fledged gullies,especially on sandy soils, along skid trails, onpoorly drained spur roads or on approaches tobridges where the erodible subsurface has beenexposed by earthworks. Too high a sediment loadcan also change the composition of a river's fishpopulation, impacting on the food supply of localpopulations (Bruinjzeel and Critchley, 1994).

Impact on wildlifeForest harvesting can also impact on wildlife:• increased pressure on local wildlife, either directly

because of the increase in population associatedwith the logging camp or forest industry, orindirectly because easier access to forest land andtransportation encourage commercial huntingand/or poaching;

• disruption and sometimes fragmentation of wildlifepopulations with roads acting as barriers to themovement of small game;

• loss or deterioration of habitat because of changesin habitat and food supply.

Improvements from RILFew large-scale studies seem to have beenconducted to provide an accurate assessment ofthe positive impact of RIL and existingdocumented data are generally incomplete.However, an example from Sarawak (thus underdifferent conditions to those of Africa) relating tothe harvesting of 25 to 50 m3/ha provides amore comprehensive picture of improvementsthat can be attributed to RIL.

INTRODUCTION

7

Impact indicators Impact reduction from RIL

Density of skid trail - 57 %

Length of trail per m 3 harvested - 20 %

Average gradient of trail - 16 %

Soil area exposed - 49 %

Area affected - 38 %

Trees damaged - 29 %Table 5. Improvements from RIL

Social impactThe forests of West and Central Africa shelterpopulations of different cultures who dependdirectly on them for their food resources,construction materials and medicinal products.They also play an important spiritual functionand role in cultural identity. Their harvesting is ofdirect concern to company workers and theinhabitants of villages in and near the harvestingarea.

Most causes of forest destruction are social inorigin, the prime culprit probably being poverty.If the objective of sustainable forest managementis to be achieved, forest use needs to benefit notonly the harvesting company and the State asowner, but also the company workers and localcommunities.

PersonnelEfficient and sustainable production requires wellplanned and well organized interaction betweencompany personnel at all levels. The workforcerepresents the frontline for the implementation ofreduced-impact practices and thus needs to beproperly instructed, trained and paid to achievethe objectives of sustainable harvesting.However, this is not always the case. Workersare often poorly qualified to carry out theirassigned duties, insufficiently paid, trained or

motivated to work effectively, with obviousrepercussions on the quality and safety of theirwork. In many cases they are also not providedwith adequate housing. As a result, the work isnot done carefully, safely and efficiently.Managers, supervisors and workers need toshare the same objectives if production is tobenefit all partners equitably. The concessionaireholds primary responsibility for providing theworking conditions needed for applyingreduced-impact harvesting practices.

Local communitiesAt present, local communities have no or fewrights of ownership over the forest on which theydepend. Harvesting activities very often fail totake their interests into account, for example theuse of forest products around their villages or inareas where the forest has traditionally beenused for nutritional, cultural or religiouspurposes. The local population is very oftensidelined from forest management. An innovativeapproach is therefore needed to ensure that thefruits and efforts of forest management areshared by all stakeholders, with particularimportance attached to dialogue betweenforester and local community.

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CHAPTER 2

«Far too many harvesting operations arecarried out without the benefit of any kindof formal, written plan. Such operationsare difficult to coordinate, impossible tocontrol adequately and in their effectsoften more closely resemble miningoperations than harvesting operationsdesigned for the sustainable utilization offorest products.» (FAO Model Code ofForest Harvesting Practice, 1996).

SUSTAINABLE MANAGEMENT OFPRODUCTION FORESTS

2.1 Forests and their multiple functions

2.2 International context

2.3 Planning sustainable management andforest harvesting

2.3.1 Strategic (long-term) management plan 2.3.2 Tactical (mid-term) management plan2.3.3 Annual plan of operation or coupe

SUSTAINABLE MANAGEMENT OFPRODUCTION FORESTS

2.1 FORESTS AND THEIR MULTIPLEFUNCTIONS

Forests perform a number of functions that areimportant to our planet and to the survival ofhuman communities and of many otherorganisms whose continued existence is in ourinterest. These functions are essentiallyecological, socio-economic and socio-cultural.

Ecological functionsThe forest environment has multiple attributes byvirtue of its biodiversity:• living environment for humans and the complex of

animal and plant species;• reservoir of genetic information;• producer of biomass, fuel and minerals;• regulator and stabilizer of the biosphere.

The need to conserve biodiversity and itsattributes means that forest harvesting should notsignificantly change the different ecosystemsencountered. Measures need to be taken toconserve and protect threatened species.Hunting and the extraction of forest productsneed to comply with legislation and internationalagreements.

Socio-economic functionsThe continuity of a forest's socio-economicfunctions can be assured if it maintains its woodand non-wood product potential and if the scaleof utilization is thus strictly adapted to sustainableyield and regeneration capacity. Damage to theremaining stand and future crop trees must bekept to a minimum.

Another important key to success is involvinglocal communities in the sustainablemanagement process and in decision-making.They need to have a share in the revenue, toretain their land tenure rights and to see animprovement in their living conditions.

Socio-cultural functionsThe socio-cultural functions of the forest need tobe maintained, particularly those associated with

the cultural identity of local populations (e.g.sacred or initiation trees, forests or sites). Thenegative consequences of forest harvesting needto be limited and mitigated by applying reduced-impact harvesting practices.

2.2 INTERNATIONAL CONTEXT

Reduced-impact harvesting is integral tosustainable forest management. It is in fact a vitalelement as forest harvesting can have manynegative consequences that partly affect forestregeneration and thus the potential volume ofsubsequent cutting cycles.

Furthermore, harvesting operations areactivities which can be controlled most directlyand easily by logging companies striving forsustainable management. We should perhapsbriefly recall the context of international reflectionthat led to the concept of sustainable forestmanagement which can be defined as «theprocess of managing permanent forest land toachieve one or more clearly specified objectivesof management with regard to the production ofa continuous flow of desired forest products andservices without undue reduction of its inherentvalues and future productivity and without undueundesirable effects on the physical and socialenvironment» (ITTO, 1992).

Back in 1990, the ITTO published itsguidelines for the sustainable management ofnatural tropical forests, some relating directly tofelling operations, access roads, extraction andthe post-harvest management of forest stands.

However, the concept of sustainable forestmanagement was formally enshrined at theConference of Rio, in June 1992, where this formof management emerged as an attractive way ofreconciling forest development to meet socio-economic needs and conservation to protect forestresources as well as the rights of future generations.

The main forest-related outcomes of the EarthSummit of Rio were cast into the non-legallybinding authoritative statement of principles for aglobal consensus on the management,conservation and sustainable development of alltypes of forests (the «Forest Principles») with clearreferences to the concepts of sustainablemanagement and RIL.

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Among the 40 chapters of Agenda 21, theoperational platform dealing with the variousspheres of environment and development,Chapter XI «Combating deforestation» lists fourprogramme areas:• sustaining the multiple roles and functions of all

types of forest, forest land and woodland;• enhancing the protection, sustainable management

and conservation of all forests, and the greening ofdegraded areas, through rehabilitation,afforestation, reforestation and other rehabilitativemeans;

• promoting efficient utilization and assessment torecover the full value of goods and servicesprovided by forests, forest lands and woodlands;

• establishing and/or strengthening capacities for theplanning, assessment and systematic observation offorests and related programmes, projects andactivities, including commercial trade andprocesses.

The Agenda’s key proposals include thepolitical will to associate local populations moreclosely in forest management, the importancegiven to management tools (databanks,inventories), the important multiple roles andfunctions of forests, the promotion of cross-sectoral approaches and capacity building.

The United Nations Framework Convention onClimate Change aimed at stabilizing greenhousegases at a level that will not disrupt the globalclimate.Forests are explicitly referred to on twooccasions:• with regard to the conservation of sinks and

reservoirs of greenhouse gases; and• with regard to specific aid to developing countries

with forested areas and areas liable to forestdepletion.

The United Nations Framework Convention onBiological Diversity.This Convention is aimed at drawing upstrategies and plans of action for theconservation and utilization of biologicaldiversity and the integration of these objectivesinto sectoral policy. Forests are never actuallycited as such.

The United Nations Convention to CombatDesertification in countries seriously affected bydrought and/or desertification.All the African countries targeted by this RegionalCode have signed and ratified these threeConventions and have turned to the Rio Summitwhen updating or reworking their recent orongoing national forest policy and legislation.

At the regional level, countries with forestsectors have worked towards the sustainablemanagement of production forests and thecertification of timber by defining a package ofmanagement principles, criteria, indicators andbenchmarks, within the framework of the AfricanTimber Organization (ATO).

This package is the culmination of a series oftests conducted from 1995 to 1998 with CIFORin West Africa (Côte d'Ivoire) and Central Africa(Cameroon, Central African Republic andGabon). Comprising 4 principles, 15 criteriaand 51 indicators (PCIs), this package wasendorsed in October 2000 at an ordinaryministerial conference of the 14 ATO membercountries in Brazzaville. Four principles and 10criteria relate more specifically to RIL.

The ATO has also urged its member countriesto set up national working parties to exploremanagement and certification at national leveland to come up with proposals for a morespecific and appropriate set of principles, criteriaand indicators. These efforts have so farculminated in a set of PCIs issued jointly by ATOand ITTO for the sustainable forest managementof African natural tropical forests, both at thenational and the forest-management-unit level, aharmonized document which refines the ATO’sPCIs and makes them consistent with the ITTO’scriteria and indicators (ATO & ITTO, 2003).

Actions by the Conference of Central AfricanMoist Forest Ecosystems (CEFDHAC) orBrazzaville Process and by the Conference ofMinisters in Charge of Forests in Central Africa(COMIFAC) have reflected the overall objectiveof getting Central African countries to managetheir forest ecosystems sustainably, by sharingthe same vision to achieve coherence of forestpolicy and legislation as well as managementprinciples, instruments and practices.

SUSTAINABLE MANAGEMENT OF PRODUCTION FORESTS

13

2.3 PLANNING SUSTAINABLEMANAGEMENT AND FORESTHARVESTING

The Annual Programme or Plan of Operations,also referred to as the Annual Coupe, is the lastand most immediate level (1-2 years) ofoperational planning in the sustainablemanagement of a forest area or concession.

This is the phase that involves the planning,design and implementation of all RIL harvestingactivities. However, this plan and its operationscan only be successful if the sustainablemanagement of the forest area has beenrationally pre-determined by the concessionholder or logging company, eschewing apredatory approach and opting forentrepreneurial behaviour that is more respectfulof the ecosystem and of the social and economicenvironment of the forest.

After all, the key objective of managingproduction forests is to secure a balanced, regularand sustainable harvest of forest products bydeploying reduced-impact practices that are well-planned and prepared within a permanent forestarea, while at the same time ensuring maximumconservation of forest resources and safeguardingtheir social and ecological functions.

Furthermore forest management should:• provide social, technical and financial benefits to

all actors and should therefore be agreed to by allstakeholders: forest owner, logging company andlocal communities;

• help decision-making by shaping practical, realisticand feasible programmes of action;

• take into account the multi-functionality of forests.

Forest utilization should also respond to:• national legal and regulatory obligations;• the ecological constraints of sustainable ecosystem

management, notably the optimal protection andconservation of diversity of flora and fauna;

• the socio-economic requirements of the areasconcerned;

• the constraints of commercial profitability in thecontext of international trade.

At company level, forest utilization shouldensure the continuity of forest resources and

sustained supply of raw material, and shouldenable a company’s internal and externalstrategy and management to shift gradually froma short-term to a long-term perspective.

However, given existing political, social andeconomic conditions in forest-rich countries ofAfrica and our limited understanding of thedynamics of tropical ecosystems, the design andapplication of forest utilization can only beguided initially by simple, but realistic, principlesand rules.

Finally, while planning is normally theprerogative of forest owners, many countrieshave opted to delegate some or this entire task tothe concession holders, thereby granting themvirtually full responsibility for the proper orimproper management of production forests.

Detailed management planning produces threedocuments of differing duration and strategicimportance, whose general characteristics aregiven in Table 6:• the strategic management plan: the long-term

document covering 20-40 years and reviewableevery 5-10 years, where decisions adopted by thepublic authorities and the logging company willshape the forest policy of these two principal actors.

• the tactical management plan: the medium-termdocument covering successive 5-7 year periods,with indications for the utilization of concessionssubdivided into management units;

• the annual plan of operation or coupe throughwhich the management plan is programmed,implemented and monitored annually. This is thetool for the everyday management of harvesting,with all interventions recorded in the forest register

2.3.1 Strategic (long-term) management plan

The plan begins by describing the forest areaand gives an outline of the logging company andits human and technical resources. It then coversthe following main stages:

Examination of the forest and its socio-economicenvironmentThe first section deals with the natural setting,topography, hydrography, climate, forest andother formations which are examined usingexisting maps and documents.

Analysis of the socio-economic environment is

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central to the management plan, as it will identifyopportunities and constraints for companyintegration into the existing socio-economiccontext. Appraisal of expectations for education,health, and better living conditions will provide ananalytical socio-economic profile that will be usefulfor directing actions to involve local communitiesinto a collaborative management strategy and tofacilitate social consultation and negotiation overland tenure and planned social structures.

The analysis should also look at employmentopportunities for villagers and young qualifiedworkers and enhance their skills through furthertraining. The final part looks at the present stateof the forest and examines previous interventionsthat might have modified the forest environmentor in some way affected its evolution.

Identifying the resourceTwo key chapters deal with mapping, photo-interpretation and forest stratification.

Mapping is generally conducted on three levels:• an overall view of the forest stand and its general

characteristics, where a scale of 1:200 000 isusually required. This work draws on existingdocuments, base maps at this scale, satelliteimagery and radar images;

• a forest and topographical stratification of the areausing aerial photographs, base maps and thematicmaps, with a working scale of 1:50 000 or even1:20 000 for aerial photographs;

• contour maps of 1:50 000 as the basic work toolfor concession managers. These can be enlarged to1:5 000 or 1:10 000 for a closer look at the terrainand can be supplemented with further details (rockoutcrops, impenetrable wetlands, cliffs) coming tolight during the harvest survey.

Mapping prior to ground work is based onremote sensing in the form of aerial photographsand satellite and radar images, which make itpossible to: • map or update the mapping of the land cover;• accurately delimit the forest area to be surveyed;• stratify the forest area by major type of stand and

natural formation. The description of strata is basedon straightforward criteria used to identify anddelimit main types of terrain (firm soil, floodland,marshland or steep slopes) and forest cover (typeand density of plant cover).The stratification process will also detect and

map topographical conditions relevant to theplanning of infrastructure, especially roads:• unharvestable areas – limits have to be set

regarding slope, frequency of rock, type of soil,above which an area becomes unharvestable;

• wetlands and flood-prone areas;• obligatory or impossible points of passage (e.g.

cliffs, deep valley lines).

Mapping and stratification will have to bebased on all available documents. Existingconventional aerial coverage at 1:50 000, orbetter 1:20 000, is strongly recommended asstereoscopic interpretation is still the only way ofgaining a precise picture of the terrain.

Aerial coverage can often be supplemented orreplaced by SPOT or LANDSAT satellite images.Maps at 1:50 000 should be used for drawingup the survey sampling plan but such coverage isby no means comprehensive, so 1:200 000maps will sometimes have to be enlarged.


15

STRATEGIC MANAGEMENT PLANLong term > 15 years

formulation of the strategy of sustainable management of forest areaglobal and thematic mapping at 1:200 000, 1:50 000 and/or 1:20 000analysis of the forest and its socio -economic environment quantitative and qualitative assessment of forest resources and wildlifemanagement decisions:

- determining the harvesting cycle- minimum diameters for harvesting and management- sustainable yield and annual allowable cut

TACTICAL MANAGEMENT PLANMedium term: 5 t o 7 years

mapping at 1:50 000, 1:20 000 and /or 1:10 000delimitation and demarcation of boundariesestablishing harvesting areas: sectioning into management units and annual cutting blockspre-determination of harvest activities in space and time establishing modalities for survey methods and harvesting (equipment and workforce)harvesting programme: characteristics of units and blocks, strata sizesplanning of primary road network

OPERATIONAL PLANShort term: 1 year

planning of harvesting operations a t the level of the annual allowable cutharvesting map at 1:10 000 or 1:5 000complete harvest inventoryidentification and marking of treeslayout of secondary forest roads, skid trails and landingstraining of staff, worker safetymonitoring, control and evaluation of harvesting

Table 6. Planning documents.

Management inventoryThe general inventory of the forest area – themanagement inventory – is the centralmanagement tool as it provides basic data todetermine the general framework for themanagement of a concession, indicatingimmediately harvestable timber potential andmedium-term crop tree potential. The purposes ofthis inventory can be summarized as follows:• to refine the stratification obtained from remote

sensing;• to locate and quantify stand types in order design

appropriate patterns of silvicultural treatment, toschedule the advance of cutting cycles over spaceand time and to calculate work volumes;

• to provide an accurate quantitative and qualitativeestimate of first-rotation harvests per species and tomake projections for second and third cutting cycles.

The management inventory, focusing onharvestable areas only (i.e. within productionzones), will be a statistical survey based onsystematic sampling at one degree. Sample plotsare laid out contiguously along parallel samplingalignments with maximum intervals of 2 to 2.5km for a generally accepted average samplingratio of 1 percent. This may in fact vary between0.5 and 1.5 percent, depending on the level ofaccuracy required and uniformity of forest area.

For estimating the number and volume ofharvestable and potential crop trees of thespecies currently identified as merchantable withsufficient statistical reliability, this samplingmethod requires a relative error of not more than15 percent. Counting is done in 10cm diameterclasses of all trees of identifiable species with adiameter of more than 20 cm.

Although requiring additional expenditure, it ismost advisable to seize the opportunity of plotsampling and forest inventory on the ground tocompile ecological and/or wildlife inventoriesand if possible, to conduct the field surveys at thesame time.

The inventory report should provide: • a set of maps and tables collating all available

information on the entire forest area to facilitate thedemarcation of series and management units duringthe conception of the management plan;

• a set of more concise tables on available commercial

volume, its spatial distribution and its accessibility,which will later form the basis for harvest planningand scheduling of the cutting cycle.

Long-term management decisions and proposalsThe inventory concludes the field work needed

to formulate decisions on resource utilization andproposed management strategy. Examination ofall factors influencing the regenerative capacityof forest and tree species after harvesting: • average annual growth in tree diameter;• natural mortality rate of tree species, and • potential damage from felling and skidding, will

help calculate the interval required between twocutting cycles, i.e. the rotation.

The pattern of diameter distribution and thegrowth and mortality of the main commercialspecies will indicate their minimum managementdiameter (MMD). Subsequently, the rotationperiod and MMDs will serve to calculate theoverall sustainable yield from the forest and theannual allowable cut.

2.3.2 Tactical (medium-term) managementplanThe tactical management plan expresses thestrategic management plan at the medium-termlevel. It restates the main objectives of forestutilization, describes its stratification andsummarizes the inventory results.

The main chapter reports the managementprescriptions:• rotation period, annual allowable cut and diameter

limits;• location, area and map of management series:

production, protection, agriculture, etc.;• establishment of concession plan, i.e. dividing the

production cycle into management units, then intoannual harvest blocks or coupes.

This division can be done:• either by dividing the total harvestable area by the

rotation, which produces annual coupes of equal size(rotation by area) but sometimes very unequal volume;

• or by dividing the total commercial volume by therotation, giving similar harvest volumes (rotation byvolume) but coupes of variable size.

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A combination of the two is often applied. Theharvestable area is first divided intomanagement units with equal volumescorresponding to 5-7 years of harvesting and aretherefore of unequal size. Each of these units isthen divided into annual coupes of equal size.

Other ways of dividing and organizing theconcession can be imposed by the authorities.

The harvesting cycle is the sequence ofharvesting in space and time for bothmanagement units and annual coupes. Theharvesting of a new block – generally for aperiod of two years – cannot be initiated beforeclosure of the previous coupe, and any return forharvesting (re-entry) is forbidden until thefollowing rotation.

Management rules mainly concern concessionboundaries, harvesting and harvest surveymodalities:• delimitation of concession perimeter: the ground-

marking of concession boundaries with cleardemarcation points and the clearing of boundarylines or their marking with paint;

• definition of harvesting rules: prescribed practicesand equipment, constraints (slope, rainfall, etc.),safety regulations;

• planning and training of workforce.

Harvest survey modalitiesAlthough the two main methods of conducting

harvest surveys are explained in Chapter 3, thegeneral characteristics and purpose of suchsurvey are described below.

The survey will indicate the number, qualityand location of harvestable and potential croptrees of all commercial species, starting from aminimum diameter, in addition to type of soil andavailability of road-improving materials. It willalso provide a detailed topographic survey of theterrain. This is the only way of: • truly gauging harvestable volumes by species and

quality, and pinpointing their location with sufficientaccuracy to harvest them without loss – thussignificantly increasing the extracted volume perhectare and reducing the land area to be harvested;

• organizing, planning, rationalizing and optimizingthe coordination of harvest activities;

• optimizing the layout of secondary roads, skid trailsand landings;

• reducing harvesting damage to the environment;• significantly raising productivity and thus reducing

production costs.

The last part of the management plan looks atthe harvesting programme and describes themanagement units and harvesting blocks: limits,area and strata characteristics, harvestablespecies and volumes by quality and diameterclass, harvesting period and mapping.

2.3.3 Annual plan of operation or coupe

The planning of operations on the areaauthorized for harvesting in one year (annualharvesting block) focuses mainly on:• conducting the harvest survey and evaluating results

relevant for operational planning;• spotting and marking (by tape or paint) harvestable

trees, future crop trees, seed trees and trees ofspecial importance (heritage trees);

• pinpointing, from 1:5 000 or 1:10 000 scalemaps, harvestable trees, identifying micro-topographical features and constraints of terrain,and laying out secondary roads, skid trails andlandings;

• designing training programmes, arranging thepurchase and maintenance of equipment andmachinery, and prescribing safety regulations;

• conducting internal monitoring, control andassessment of harvesting operations.

Applying the full array of planning tools forsustainable management will clearly be limited tolarge and medium-size companies holding long-term concessions. However, this should notexclude or hamper the dissemination and total orpartial deployment of RIL techniques amongsmaller logging companies and among short-term licence or permit holders.


17

CHAPTER 3

«Many logging operators believe thatenvironmental protection can only beachieved through costly measures thatwill drive them to the brink of bankruptcy.This is simply not true. The experience ofoperators who develop thorough harvestplans and then carry out the operationsas specified in these plans hasdemonstrated clearly that theseprocedures not only improve operationalcontrol and reduce environmentalimpacts, but can also reduce costs andsubstantially increase profits.» (FAOModel Code of Harvesting Practice,1996)

PRE-HARVEST PLANNING

3.1 Mapping tools

3.2 Geographic Information System- a management tool

3.3 Harvest survey3.3.1 Survey criteria3.3.2 Description of the pocket inventory3.3.3 Description of the inventory by

systematic survey lot3.3.4 Impacts of survey activities on the forest

3.4 Non-harvest areas 3.4.1 Delimitation3.4.2 Special precautions

3.5 Tree spotting and marking - planning and optimizing the extraction structure 3.5.1 Layout of the secondary road network3.5.2 Preparing the harvesting block - planning

and layout of skid trails and landings

3.6 Producing the operational harvesting map


Objectives:• to reduce harvesting damage for enhanced

protection of the environment; • to permit efficient and competitive forest harvesting;• to plan harvesting operations on an annual level;• to compile and analyse all biological,

topographical, hydrographical and socio-economicdata required for the preparation of harvestingoperations.

Pre-harvest planning is an essential componentof RIL. It involves annual harvest estimates basedon stand potential in designated harvest areas. Itfollows the harvest cycle and can cover one ormore harvesting blocks. The planning is normally1 to 2 years before harvesting (Table 7) andgenerally produces a document on scheduledoperations, actions to be taken, means to beemployed and a detailed map (1:5 000 or 1:10 000) of the areas to be harvested.

3.1 MAPPING TOOLSThe management plan provides the operationsmanager with all the mapping and survey dataneeded to draw up detailed harvesting maps.The mapping documents vary from one countryto another, but generally include:

General documents• 1:200 000 quad maps with or without contour lines

(40 m intervals);• 1:200 000 thematic maps: hydrography, geology,

pedology, morphology, vegetation;• 1:50 000 quad maps with contour lines (20 m

intervals);• 1:50 000 LANDSAT or SPOT satellite imagery;• 1:200 000 radar imagery;• old and recent aerial photo coverage at a scale of

1:20 000 to 1:50 000.

Documents produced by the management plana) Base map: essentially a 1:50 000topographical map with contour lines at 20 mintervals. It displays location and layout of thefollowing elements:• contour lines and peaks;• river system and permanent waterbodies;• main and secondary roads, railways, airstrips;• towns, villages and large logging camps;• administrative boundaries of provinces,

departments and districts;• boundaries of forest concession.

b) Map of forest strata: this 1:50 000 mapshould indicate the different types of plantformation, using conventional colours andcodification and distinguishing in particular:• primary forests;• secondary forests;• forests on steep slopes;• riparian formations and gallery forests;• marshland forest types;• savannahs;• crops and fallows.

The map is based on the interpretation of thepreviously mentioned documents (aerialphotographs, SPOT images, radar images) andis completed with the examination of existingthematic maps.

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2 years in advance:Demarcation of area to be harvestedAnnual allocation for allowable harvesting volumeHarvest survey: volume, quality, location, detailed topographyDelimitation and demarcation of non -harvest areasHarvesting map at 1:5 000 or 1:10 000Planning of secondary forest roads

1 year in advance:Survey and zoning of harvesting area; counting, recording and preliminary marking of harvestable trees

4-6 months:Construction of secondary roads

1-3 months:Tree spotting and markingLocating and ma rking of skid trails and landingsMarking of trees next to skid trails and around harvestable trees

Harvesting:Clearing of skid trails and landingsFelling, topping and butt trimmingWinching and skiddingCross-cutting, scaling, marking and treatment of logs at roadside landingslandingsTransportControl, monitoring and post -harvest assessment

Table 7. Diagram for the planning and implementation ofharvesting operations

c) Consolidated forest map: this map at 1:100 000 or 1:50 000 is obtained bygeneralizing the contours of the forest strata map(after any necessary aggregation) andoverlaying important topographical information.A table summarizing aggregated strata areasaccompanies this map. Like all cartographicdatabases, it can be digitally converted and fedinto a Geographic Information System (GIS).

3.2 GEOGRAPHIC INFORMATIONSYSTEM – A MANAGEMENTTOOL

A Geographic Information System is a computer-based system which, drawing from a variety ofsources to compile, collate, process, analyse,combine, elaborate and display geographicallyrelated information, can effectively contribute tothe management of landscapes and naturalresources.

A GIS permits four types of activity: digitalcapture of geographical coordinates, navigation,thematic handling of data, spatial analysis, andestablishment of maps.

Maps produced from remote-sensing, all othergeo-referenced data and data from themanagement inventories and harvest surveys aredigitized and logged into the GIS. These datacan be:• thematic maps (land cover, geological,

pedological, etc.) or existing topographical maps;• the inventory sample plot system;• forest mensuration, flora, fauna and environment

data gathered from sample plots and surveyedharvesting blocks;

• ground observations.

All information fed into and processed by theGIS enhances the utility of an inventory as itpermits the integration of a variety of attributes andconstraints of terrain (topography, non-accessibleareas, etc.). It can also help identify representativeareas for the conduct of a pre-inventory.

The field data are then also fed into the GISand can be plotted as distribution maps for thedifferent inventoried variables:• distribution of species,• volume by species, diameter class, hectare.

These distribution maps are immensely usefulfor determining management prescriptions. TheGIS also ensures that documents are up-to-date(e.g. by integrating harvest survey results) andreflect the dynamic evolution of the forest undermanagement. The progress of harvestingoperations can be monitored and schedulesforecast through the regular examination ofongoing activities.

The sophistication and complexity of GISsoftware and performance will depend oncompany requirements. It can be combined withmanagement and logistics software in order toprovide computerized operational data that willenable a company to monitor all activitiesrelating to:• the harvest areas and annual coupes, the road and

trail network, marketing and the processingstructures;

• the management of machinery, equipment andconsumables;

• the workforce.

This tool gives the company an interfacebetween financial accounting and costaccounting, enabling it to ensure that its fieldoperations and its management are sound.Linkage between these databases and the GISmeans that timber can be tracked from standingtree to point of sale or processing site, renderingforest products traceable throughout theproduction chain.

N.B.With regard to the use of computer equipment

(computers, GIS, database software, etc.) andadvanced hardware (GPS, etc.) requiringconsiderable investment, it is important to notethat all planning techniques required for RILpractices (compilation and analysis ofinventories/surveys, planning and layout ofextraction network, mapping, etc.) can also becarried out using simple conventional means(manual compilation, pocket calculator,compass, clinometer).


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3.3 HARVEST SURVEY

The harvest survey, or inventory, is an intrinsicprerequisite of RIL. It has been made mandatoryfor concession holders by all recent forestlegislation.

Objectives:• to quantify and qualify available volumes by

species, to identify trees in the annual harvestingunit and the felling block without error or loss;

• to organize and optimize the coordination ofharvesting activities and the utilization of industrialproduction and marketing capacity and to improvecontrol over operations;

• to optimize the layout of the secondary roadnetwork, skid trails and landings;

• to facilitate reduced-impact harvesting and thus limitdamage to the environment;

• to facilitate the production of a detailed mapindicating the precise location of trees to beharvested and trees to be protected, species andvolumes, topographic and hydrographic detailsand non-harvest areas.

Because of their intrinsic diversity, tropicalforests have to be comprehensively searched toidentify each harvestable tree, requiring a full or100 percent inventory coupled withgeographical and topographical surveys.

The two survey methods currently employed inAfrica are:• the pocket inventory, where the harvest unit is

divided into blocks and pockets of varying sizedemarcated by natural boundaries, normally thearea between two watercourses. These naturalboundaries are then connected by transects to closethe pocket. This method reduces the need to clearsurvey lines but requires topographical maps of atleast 1:50 000 and highly trained, experiencedcrews to avoid errors in coverage of terrain andcounting of trees;

• the systematic parcelling inventory, which uses East-West and North-South transects to demarcatesurvey units of equal size (usually 20 to 100 ha,depending on the spacing between survey lines).More survey lines need to be cleared with thismethod, but unit layout is clear and without risk oferror.

Before describing these two methods, we needto look briefly at criteria for identifying andrecording the species to be inventoried.

3.3.1 Survey criteria

These include:a) A list of species to be inventoried: in principle the

commercial species to be harvested which are oftendetermined by the authorities, plus othermerchantable or potentially merchantable speciesdetermined by the logging companies anddesignated by their commercial name.

b) The status of trees and species:• harvestable trees of targeted species with a

diameter above the MMD;• potential crop trees of the same species but with a

diameter below MMD. Such trees are generallyrecorded as having a diameter of MMD minus 20cm or a general diameter applicable to all species(e.g. 50 cm). Their registration is not obligatory inall countries;

• protected trees or species: rare species, outstandingtrees (very big diameters exceeding 2 m) orheritage trees (nutritional, cultural, religious or othervalue);

• seed trees in apparent good health, withremarkable phenotype and existing in sufficientnumbers to foster natural regeneration.

c) Inventory quality grades:• Quality 1: very well shaped export trees with at

least one long log;• Quality 2: trees for export or sawnwood with limited

defects and at least one log shorter than 6 m;• Quality 3: trees destined for processing for local

consumption and sale;• Quality 4: rejected trees.

3.3.2 Description of the pocket inventory

Using a 1:50 000 scale map with contour lines,the coupe or the annual harvesting unit isstructured into blocks equating to 3-4 monthlogging targets. This division is based on naturaltopographical boundaries. The blocks are then -manually or using a GIS - subdivided into pocketsof 10-60 ha, depending on existing naturalboundaries.

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A main survey line following the ridge crest(s)is identified on the map by letter and number. Itshorizontal length and compass bearing arerecorded on a data sheet consigned to the leaderof the inventory crew. Using a GIS, the pocketboundaries and survey line are then plotted on a1:5 000 map with contour lines. The main surveyline starts from the roadside and is tentativelyplotted on the basis of maximum skiddingdistance, harvestable timber stock, terraincharacteristics and occurrence of non-harvestareas.

The main survey line, with minor groundmodifications, and any necessary secondarysurvey lines, will constitute the skid trail layout.

Each pocket is flagged at the roadside entry ofthe main survey line by indicating the pocket andmain survey line number on a tree. The pocketinventory is generally carried out by a crew of 9-10 people, including a crew leader, a compasssurveyor, 2 slashers and 5-6 tree counters. Thealignment with a maximum width of one metre iscleared by machete. The operation begins with a

preliminary reconnaissance of the pocket,localizing the ridge crest and the main surveyline and if necessary modifying its alignment. Thecompass surveyor indicates the line of directionand the slashers proceed to clear the requiredwidth. The survey line is staked every 100 metreswith a picket recording its number (with paint ortape) and distance from starting point.

Tree counting is conducted in successivecruises determined by terrain and pocket layoutand decided by the team leader, who makes surethe entire pocket is covered. Secondary linesdivide the pocket into subpockets to facilitatecounting. The tree counting crew has 5 countersand a crew leader. Each enumerator has adiameter gauge, a marker and a marking device(e.g. tape, tag or plaque).

At the start of a cruise, the team leader placeshimself on the main survey line from where he cancontrol survey progress with the help of the 100-metre pickets. The counters advance in parallel at30-metre intervals from each other, counting thetrees to their right. Each counter is assigned a set of


23

Figure 1 Division into blocks and pockets Figure 2 Survey map from pocket inventory

numbers in units of 100 (1 to 100, 101 to 200,etc.) at the start of each block.

For each counted tree, the enumerator calls outhis name, the number he is about to give the treeand its characteristics (species, diameter, gradeand status). The crew leader registers the treeand number on the survey map and enters detailson the enumeration sheet. The tree number andother details are also noted on plastic tapeattached to the tree trunk or to a wooden picketplanted next to the tree.

The status of the tree is also marked on its trunkby paint or machete, for example:• harvestable tree: a blaze (axed gouge) or cross• seed tree: S• heritage tree (food tree, tree with cultural, religious

or other significance): H The tree counters also note terrain features:

small waterbodies and their flow, passes,elephant tracks, steep slopes, swamps, rocks,inaccessible areas, occurrence of laterite andgravel.

Each crew is equipped with a GPS which canpinpoint a location to within 10 m. Thisinexpensive instrument will become increasinglyessential for determining location in a forest, forverifying the layout of a survey pocket and forestablishing the exact position of a tree.

Observations:Tree counting without systematic cruise patternsdetermined by the shape of the pocket and thejudgement of the crew leader always leavesdoubt as to whether the whole pocket has in factbeen covered and every tree counted. Therecould also be discrepancies between the positionof pockets on a map and on the ground.

It is up to survey crews to determine whichtechniques they will use to identify and counttrees. The means suggested above are by way ofexample only.

Striped tape and wooden pickets are useful butcan often be removed by monkeys, causingconfusion during final tree spotting and markingprior to felling.

3.3.3 Description of the inventory by systematic survey lot

Starting from a baseline (e.g. a road, an existingskid trail or a former survey line) serving astopographical axis of reference and access, theharvesting unit is covered with a grid of surveylines:• Primary survey lines along magnetic East-West and

North-South at intervals of 500-1000 m, sometimesmore, producing quadrilateral lots measuring 50,100 ha, etc. The length is measured, with or withoutslope correction, by cord and calibrated cable, andregularly checked. Hardwood pickets are plantedat 50-100 m intervals or a tree is tagged orpainted. The survey lines are cleared by machete,axe or chainsaw to a width of 1-2 m. They have toremain visible for 1-2 years as points of referencefor final tree spotting prior to felling and for thecontrol and monitoring of harvesting activities.

• Secondary survey lines generally running North-South and spaced at 200, 250 or even 500 mintervals. These have a width of about 1 m. Theyare roughly cleared by machete, are not signalledby picket or tag, and can deviate significantly indirection, although always remaining within theblock.

• These primary and secondary survey lines thereforedemarcate 20, 25 or 50 ha lots that constitute thesurvey units. They may not always be rectangularas the secondary survey lines can deviate, but thisis unimportant in practice so long as the points ofdeparture and arrival on the baseline are properlyrecorded. However, the survey map shouldaccurately reflect the layout of survey lines as foundon the ground and not as expected in theory

A survey-line clearing crew may comprise acrew leader, a compass surveyor, a rod man and5 or 6 labourers, making a total of 8 to 9 people.

Typically a clearing crew can open up 2 km ofsurvey line each day, depending on itscompetence, the terrain and the density ofundergrowth. Primary alignments can bedesignated by letter and secondary alignmentsby number to facilitate the use of surveydocuments. The crew leader makes a note ofwork done and topographical featuresencountered and sketches the forest along the

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survey line, indicating the position of pickets.This sketch will be used to draw the map.

The trees are then counted. Each cruise coversa width of 200-250 metres, so one return cruisewill normally be enough for each lot.

The crew of one tallyman and six tree countersadvances in line. The counter at one extremityremains on the survey line while the counter atthe other extremity marks the line of passage forthe return cruise. The crew periodically stops toget back in line. The trees are counted in thesame way as for the pocket inventory.

A team of 7 people can cover about 50 ha eachday depending on their expertise and training and

on the number of trees to be counted. The tallymannotes the location of each stem on a tally sheettogether with relevant information on the terrain,especially ridge crests that would be suitable asbaselines for log extraction.

Under both inventory methods, the survey andenumeration sheets and the duly completed mapsare delivered each day to the management unitfor computer entry and processing.

These documents are digitized by scanner andtransferred to the GIS. A database is thencreated containing datasets for each countedtree (number, location, species, diameter, quality,status).

Harvesting blocks representing a company’smonthly production target are then defined,either by grouping inventory pockets, or byreferring to natural boundaries and roads,depending on the inventory method used. Alarge scale (1:5 000 or 1: 10 000) survey mapis then produced to facilitate the proper planningof the road and skid trail configuration. Thesurvey map indicates:

Topography• Terrain with contour lines;• natural and artificial boundaries of the harvesting

block;• watercourses;• swamps;• pre-existing roads and trails, villages;• steep slopes and rugged terrain;• crests;• impenetrable areas.

Forest resources• Harvestable trees with their survey number and

species symbol or code: OK: Okoumé; MA:Mahogany; PDK: Padouk, etc.;

• seed trees with their species code;• potential crop trees with their number (if numbered)

and species code;• protected trees with their code.

The harvest survey should ideally be startedtwo years before harvesting so that the mappingcan be completed one year in advance.


25

Figure 3 Inventory by systematic survey lot

Figure 4 Organizing the survey

3.3.4 Impact of survey activities on the forest

The inventory impacts marginally on the forest.The visible results are the 1-2 metre wide surveylines that are generally cleared by machete only,the wooden pickets and the marking of trees withpaint or tape. These signs of intrusion rapidlydisappear. On the other hand, the survey lines:• allow survey workers to locate and poach game

more easily;• facilitate access to external poachers and possibly

to illegal loggers.

3.4 NON-HARVEST AREAS

Objectives:• to identify and protect areas to be excluded from

harvesting;• to reduce negative impact on local populations,

resources and the ecosystem.

3.4.1 Delimitation

Full reconnaissance of the annual harvesting unitduring inventory makes it possible to locate anddemarcate areas to be excluded. These need tobe clearly marked on the survey map and should,of course, be distinguished from areas that arealready eliminated on regulatory grounds (e.g.roadside areas restricted to community use) orbecause of stratification in the management plan(protection series).

Non-harvest areas are: • unharvestable areas: swamps, very steep slopes

(normally above 45 percent for tractor skidding),rock outcrops;

• sites of cultural or religious value: sacred trees andforests (these need to be identified with the localpopulation);

• areas of ecological, scientific or touristicimportance: areas with extensive diversity ofwildlife, habitat of endemic species, unique andfragile habitats, etc.;

• environmentally sensitive areas, i.e. adjacent topermanent watercourses and backwaters or aroundswamps. The designation ‘environmentally sensitivearea’ protects banks from erosion and excessivesedimentation. Such areas can also function assmall biodiversity reserves and points of refuge foranimals during harvesting.

Recommended widths for environmentallysensitive areas vary according to practitioner butthe following average figures would seem to beacceptable:

If necessary, exclusion areas and theirstewardship may be negotiated among partners.

3.4.2 Special precautions

Non-harvest zones and their environmentallysensitive areas need to be protected as follows:• no tree to be felled within these areas, and trees

located in the immediate vicinity should, if possible,be felled away from the area and fromwatercourses;

• if a tree is inadvertently felled into a watercourse,all its debris should be removed causing as littledisturbance as possible to the river bed and banks;

• machinery is banned from these areas, exceptunder special circumstances in which case thecrossing distance should be as short as possible tominimize disruption;

• temporary log crossings may be authorized ifmachinery needs to cross a watercourse, forexample to build drainage structures;

• when absolutely necessary, watercourses may becrossed on rock or gravel beds;

• no earth movement or grading work is allowed inthese areas;

• no harvesting debris should be introduced intoprotected or environmentally sensitive areas.

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Watercourses: Width of sensitive area

Width < 10 m 10 m on each bank



Gully 10 m on each side

Creek or backwater 5 m on each side

Swamp 10 m from edge

Table 8. Width of sensitive areas

3.5 TREE SPOTTING AND MARKING– PLANNING AND OPTIMIZINGTHE EXTRACTION LAYOUT

Objectives:• to limit impact on remaining stand, soil and

watercourses;• to limit areas deforested and disturbed by roads,

skid trails and landings;• to enhance stand and harvesting productivity by

ensuring no harvestable tree is omitted;• to enhance productivity of harvesting operations

and thus reduce costs.

The harvest inventory provides all the informationrequired for:• optimizing the layout of the secondary road network;

• identifying and marking trees consideredharvestable because of species and quality;

• planning the skid trail and landing network andoptimizing realization on the ground;

• establishing corporate commercial policy: speciesto be harvested, volumes, quality grades andharvesting schedule.

These operations are carried out byspecialized teams, other than the inventory team.

3.5.1 Layout of the secondary road network

The layout and realization of access and mainroad networks are carried out on the basis ofinformation provided by the mid-termmanagement plan. However, planning the


27

Figure 5 Watercourses and sensitive areas

secondary road network within a harvesting unitneeds to be based on the findings of the harvestinventory and is carried out one year beforeharvesting.

The secondary road network has to ensure thatthe harvesting unit is properly accessible, whilemaintaining a balance between skiddingdistance and network intensity. Layout will bedetermined by:• relative abundance (distribution, volume and

quality of species);• topography and hydrography;• terrain characteristics.

These three features will determine theharvesting period (i.e. dry or rainy season) andthus the characteristics of the roads to be built.

The road network will avoid areas with fewharvestable trees and areas with serioustopographical and terrain constraints (steepslopes, swamps). It will also seek to safeguardpotential crop trees and heritage trees.

Tracing the road network will be entrusted to aspecialist or the technical chief of operations. Theprovisional layout will be based on the surveymap and additional ground inspections.

3.5.2 Preparing the harvesting block –planning and layout of skid trails and landings

The harvesting blocks have to be prepared a fewweeks or (at most) months before harvesting.Preparation involves: • identifying, from the map, the blocks demarcated

by natural boundaries, which generally correspondto the area between two watercourses crossed by aridgeline leading to a spur or secondary road;

• clearing a track by machete along the ridgelinewhich will essentially serve as the main skid trail.

(N.B. In the case of a pocket inventory, thesetwo operations were already done at the time ofthe inventory.)

Spotting and final marking of trees to beharvested or protected– The spotting crew examines each treeidentified as harvestable for the inventory andaccepts or rejects its harvestability according to

market criteria (species, diameter and quality).A rejected tree has its tag removed or numbererased. An accepted tree is formally identifiedwith a new number (harvesting number), anadditional marking (cross, blaze) or a set ofplaques. Many loggers use the plaque methodto ensure that all harvestable timber has beenextracted. Three metal plaques bearing thenumber of the tree, the number of the harvestingblock, the species and quality are nailed to thetrunk. The first will be removed by the feller, thesecond by the choker-setter and the third by theharvest enumerator, and all will be sent to theoperations chief’s office for verification. A treedisregarded or rejected by the inventory teambut subsequently judged acceptable is given aharvesting number and identified on the surveymap. Potential crop trees or trees to beprotected, whether identified or numberedduring the inventory or not, and trees to besafeguarded during felling and skidding (e.g.adjacent to a tree to be felled or beside a skidtrail) are signalled by striped tape. All thisinformation is noted on a tally sheet linkingsurvey operations, especially numbering, withactual harvesting.

Layout of skid trails and landingsAs the harvestable trees are given their finalmarking, the spotting crew optimizes the skidtrail layout by tracing, with machete or tape, thetrajectory of each log from stump to the main skidtrail. The gradient of a trail without earthworkshould be no more than 30 percent; above whichcut-and-fill profiles are required. Gradients ofmore than 45 percent, the operating threshold ofground-based skidding equipment, should neverbe used in order to avoid accidents and preventerosion.

The layout of these trails should avoiddamaging potential crop trees and, as far aspossible, penetrating environmentally sensitivezones or crossing watercourses. Where asecondary trail joins a main trail, the number oftrees to be felled is notched onto a picket,sometimes with details of species.

Where the main skid trail joins the roadsidelanding or the road directly, the final picket will

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indicate the total number of trees to be felledwithin the harvesting block.

Logs extracted along a main skid trail aregenerally taken to a roadside landing but, if fewin number, may be left directly at the roadside,without a landing site being cleared. Two mainskid trails can lead to the same landing. Thelocation of a landing is decided when laying outthe main skid trail. Its size has to beproportionate to the volume of timber to behandled but should always be kept to aminimum.

The best layout for skid trails and landings canbe tentatively determined in the office and notedon the survey map using the GIS. The tentativelayout can then be verified on the ground andamended as necessary.

3.6 PRODUCING THE OPERATIONALHARVESTING MAP

The harvesting map is nothing more than thesurvey map at a scale of 1:5 000 or 1:10 000supplemented with information from the treemarking and the harvesting block preparation. Itshows the boundaries and numbering for eachharvesting block, and the roads, skid trails andlandings. Non-harvest trees are normallyremoved from the map for purposes of clarity. Ittherefore only shows the trees to be harvested,their harvesting number and their species codeand includes a boxed summary of the number oftrees per species to be harvested within theblock. The harvesting crews are then given themap and briefed on all its indications, forreference during felling and extraction.


29

Figure 6 Specimen harvesting map

CHAPTER 4

«Road engineering involves thespecification of design standards and theactual engineering design, field layout,construction and maintenance of forestroads and subsidiary structures such asbridges and culverts.» (FAO Model Codeof Forest Harvesting Practice, 1996)

PLANNING AND CONSTRUCTION OF ROADNETWORK, DRAINAGE STRUCTURES AND

WATER CROSSINGS

4.1 Road classification

4.2 Characteristics of the road network

4.3 Road characteristics4.3.1 Cross section4.3.2 Horizontal alignment4.3.3 Longitudinal profile

4.4 Road construction4.4.1 General rules4.4.2 Layout4.4.3 Clearing4.4.4 Blading4.4.5 Sunlight exposure4.4.6 Roadway compaction and improvement

4.5 Drainage: drains, outlets, culverts and box drains4.5.1 Avoiding water penetration4.5.2 Evacuation of rainwater runoff: side

drains, outlets and culverts4.5.3 Drainage of roadway structure

4.6 Crossing watercourses: drifts and bridges4.6.1 Drifts4.6.2 Bridges

4.7 Road maintenance4.7.1 Regular maintenance4.7.2 Resurfacing 4.7.3 Other maintenance operations

4.8 Impact of road construction

4.9 Recommendations

PLANNING AND CONSTRUCTIONOF ROAD NETWORK, DRAINAGESTRUCTURES AND WATERCROSSINGS

Objectives:• to ensure efficient access to the forest under best

possible conditions;• to limit the area cleared for the road network to

minimize the impact on soil erosion, forest andharvesting costs;

• to convey harvested products to point of sale orprocessing;

• to provide efficient and safe transportation ofpersonnel;

• to reduce maintenance costs of haulage equipment;• to meet obligations laid down in the logging

contract.

4.1 ROAD CLASSIFICATION

Forest roads can be classified into four categories:• Access roads that connect the boundaries of a

concession with a public road, waterway orrailroad network. These roads have to carry the fullload of timber harvested during the entire durationof a permit and must therefore be permanentlytraversable. They carry tens to several hundreds ofthousands of tonnes each year.

• Main roads within the harvesting permit that giveaccess to part or all of the concession area andoften branch from a trunk axis running virtually thelength of the permit area. This transit road and allroads connecting a management unit, a village or apublic facility must be permanent. The others needto be traversable for at least one year, sometimesseveral years. They must be kept in good conditionand serviceable throughout the year.

• Secondary roads or feeder roads that lead to eachharvesting block. Their life span is limited to a fewweeks or months at most, so they often require littlemaintenance. The landings are usually locatedalong these roads.

• Spur roads that are short roughly graded tracksused on gentle terrain in the dry season to connectremote landings with secondary roads.

4.2 CHARACTERISTICS OF THE ROADNETWORK

The harvesting road network usually has featuresthat distinguish it from the public road network: • the roads are generally private; their characteristics

are often determined solely by the demands of theconcessionaire who is free to choose the size ofhaulage equipment to be used and to adapt theroad infrastructure accordingly;

• the purpose of these roads is to collect goods ratherthan connect locations. Vehicles do not thereforeneed to travel fast and roads can be wind aroundterrain contours, requiring less earthwork;

• the volume of traffic is limited to the extraction offorest products and related activities. A main roadwill carry an average of 30 to 40 vehicles a day;

• roads serving as main axes of a permit area willhave to be kept open all year for the regular supplyof timber to log yards and mills and for logistics tocamp facilities and harvesting units;

• the direction of transport is mainly forest to log yardor mill, with vehicles returning unladen able tohandle steeper slopes than outgoing vehiclestravelling laden;

• most of the roads are built for a limited life span,especially secondary roads which will serve toremove timber and then be closed until the nextrotation some 25 to 40 years later. Constructionstandards and resilience can therefore be lowerthan for public roads;

• some areas with difficult access are only harvestedduring dry weather, so secondary roads servicingthese areas will be of lower standard than all-weather roads.

In some countries, forestry main roads tend tobecome rapidly absorbed into the public roadnetwork and therefore have to meet the officialstandards set by the road authorities.

4.3 ROAD CHARACTERISTICS

Each road is defined by three elements:• its profile or cross section;• its horizontal or bird's-eye layout;• its longitudinal section (projection along the vertical

axis).

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4.3.1 Cross section

The most common widths are: right-of-way 30 to 45 m maximumforest clearing 15 to 30 mlevelling subgrade 7 to 12 mgrading of roadbed (ditch bed to ditch bed) 6 to 9 msunlight exposure on gentle terrain 10 to 17 msunlight exposure on hilly terrain 5 to 30 m

On hilly terrain, width clearing is alwaysbroader on upslope side and an East-West roadrequires less width clearing than a North-Southroad as it has longer sunlight exposure.

Width of the roadbed (between inner ditch edges)Measurements most commonly encountered are:Access roads 10 -12 mMain roads 8 -10 mSecondary roads 5 - 7 m

Profile of road surface and shouldersThe road surface or roadway should always becambered to facilitate lateral rainwater runoff.The most effective slope that also avoids washoutis 3 to 5 percent.

Side drainsThe ditches channel runoff water to outlets. Theyare triangular when dug by grader. Their upperwidth is 1-1.5 m and their slope generally 2/1internally and ½ externally.

4.3.2 Horizontal alignment

Each alignment is unique but follows certainprinciples:• on gentle terrain, roads are built along or adjacent

to ridgelines, thus limiting earthwork, facilitatingdrainage and avoiding flooding during the rainyseason;

• in areas without continuous ridges, roads lead fromone elevation to the next, along slopes between twoobligatory points of passage;

PLANNING AND CONSTRUCTION OF ROAD NETWORK,DRAINAGE STRUCTURES AND WATER CROSSINGS

33

Figure 7 Cross section of road on flat terrain

Figure 8 Cross section of a standard cut-and-fill hillside road

Figure 9 Standard side drain profile

• on steep terrain, roads run along valleys and crosssmall waterbodies as far from the mouth aspossible.

CurvesMinimum curve radius is determined by externalturning lock of vehicle. Timber trucks require 15-20 m but far greater radii are generally adopted.

Curve wideningArticulated vehicles deflect around tight curveswith the rear trailer wheels following a differenttrajectory to the tractor wheels. Added width istherefore needed which then tapers back to astraight line at curve entry and exit.

Two successive curves in opposed directionshave to be separated, as far as possible, by astraight line of 40 to 50 metres on gentle terrainand at least 10 metres on steep terrain. Forreasons of safety a curve should never be placedimmediately before a bridge; straight approachand exit lines of at least 50 m are required.

Visibility in curvesVisibility in curves is also an essential safetyrequirement. The minimum visible distanceshould be twice the braking distance for a givenspeed.

To enhance visibility on hilly terrain, a ledgecan be cut into the hillside at the height of the

driver's line of vision, about 1-1.25 m abovethe surface of the roadway.

4.3.3 Longitudinal profile

The longitudinal profile of the road should:• permit water runoff without surface washout. A

minimum slope of 1 percent, for example, is alwayspreferable to a flat section, but damage fromwashout can soar when a slope exceeds 5 percent,entailing costly repair;

• avoid steep updrive and downdrive gradients. Thefollowing maximum road grades should beobserved:

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Minimum radius Recommended radius

Gentle terrain 40 m 100 m

Steep terrain 20 m 40 m Table 9. Curve radius

Radius of curve Widening Adjustment length

20 m 2.5 m 20 m

50 m 1.0 m 30 m

100 m 0.5 m 30 m

Table 10. Widening and adjustment of curve

Speed (km/h) Braking distance (m) Visibility distance (m)

30 20 m 40 m

50 45 m 90 m

60 60 m 120m

Table 11. Visibility distance

Figure 11 Visibility ledge

Figure 10 Widening and adjustment of curve

Travelling laden Travelling unladen

Gentle terrain 4 % 8 %

Steep terrain 8 % 12 %

A steeper grade is acceptable, if unavoidable,but only for a very short section. It is important tonote that:• the gradient on curves should be less than on

straight stretches;• gradients should be zero on hairpin bends;• level or gently sloped intersections should be built

into long ramps;• slopes in the direction of generally unladen travel

should not be too steep to prevent the occasionaltraffic of laden trucks towards the forest and loggingcamps (e.g. trucks carrying equipment, tank trucks).

4.4 ROAD CONSTRUCTION

4.4.1 General rules

Because of their nature, forest roads requirespecial construction rules:• roadlines need to follow terrain contours for reasons

of economy, thus forest roads are winding. Earth isusually moved sideward during blading, withlengthwise movement restricted to short sectionsand special purposes, such as creatingembankments or bridge ramps;

• gradients should be as gentle as possible becauseof the predominance of timber truck traffic.Maximum road grades towards the forest (unladentravel) can be higher than from the forest (ladentravel);

• roadways are made of compacted natural soil withthe addition, where possible, of a thin layer ofaggregate, usually laterite. Bearing capacitystandards are not the same as for public highways,so meteorological constraints (wet-weather barrierregime) need to be observed, with haulageprohibited during and immediately after rainfall.

4.4.2 Layout

Road layout is the result of a series ofcomplementary studies, starting with provisionaldesk alignment using the GIS or existing maps andproceeding to reconnaissance on the ground.

The provisional layout is determined bylandscape and natural elements, identifyingvalley lines and main ridgelines and sketchingbasic macro-relief features. The requisite roadalignment is then explored step-by-step,

determining points of obligatory passage andtentative connecting lines, avoiding pointsconsidered impassable. Generally, roads shouldbe located:• along ridgelines on gentle terrain for minimal

earthwork, easier drainage and preferable uphillskidding;

• along slope flanks to connect one elevation to thenext, where ridgelines are not continuous;

• along valley bottoms on steep terrain where theseare sufficiently broad.

Finally, roads should preferably be laid in flat,timber-rich areas and in savannahs or oldplantation areas that are easy to cross.Provisional roadlines have to be compared withthe reality of terrain by means of on-foot surveys,best done in the rainy season to get a true pictureof soil characteristics, swamp limits andmaximum width and depth of watercourses.

Certain rules apply when plotting final roadlayout:• on rugged terrain, only main roads run from one

valley to the next; secondary roads only accesssecondary valleys and do not cross ridgelines;

• roads along hillsides should be laid on ground withmoderate slopes;

• roads along hillsides that have steep flanks requireblading to cut a profile for stronger roadbed andeasier drainage. Cutting into a hillside also permitsrainy season work as the road subgrade remainsuntouched.

Watercourses in broad flat valleys aregenerally not crossed next to points of confluence

35

Figure 12 Hillside profile


in order to reduce the number of bridges. The final layout is a 1-metre wide line staked at

regular intervals to indicate the exact horizontalalignment. The roadline must avoid protectedareas and where possible, environmentallysensitive areas as well as future crop andheritage trees.

4.4.3 Clearing

Vegetation and top soil are cleared from thesubgrade, which is always done by crawlertractor. For reasons of safety, large trees arefelled by chainsaw and their stumps are thenremoved by tractor.

4.4.4 Blading (earthwork)

The road subgrade is bladed immediately afterclearing, generally using the same crawlertractor to move material, build earthfills andinstall side drains and outlets. The volume ofmaterial moved should be limited to the extent acrawler tractor can economically sustain.Longitudinal movement is kept to a minimum(earthfill for valley lines, embankments andapproaches to bridges).

Although not very common in Africa, trackedexcavators offer several advantages whenconstructing hillside cut-and-fill roads over steepterrain:• tree stumps, crowns and earthcut debris can be

easily extracted and placed at the foot of theearthfill to form a filtration litter, preventing sedimentfrom reaching a watercourse. This also keeps plantdebris separate from earthfill and thus avoids therisk of subsidence from plant decay;

• earthcut can be reduced by 20 to 30 percent ascompared to bulldozer blading;

• earthfill can be in successive 30-50 cm layers thatare easier to form and better compacted. Whereterrain permits, earthfill can be laid on a foundationof stones, rocks or resistant trunks put in place byhydraulic excavator shovel;

• the cutslope profile can better match the naturalslope, thus lessening the risk of erosion andlandslide;

• the fillslope profile can be shaped, corrected andcovered with branches, thus reducing unprotected

surfaces and facilitating plant regeneration on theslope.

Cut-and-fill roads should never have a lateralearth berm that could block downslope waterrunoff.

On flat ground, lateral berms or heaps ofstump, crown and clearing debris should be keptto a minimum and openings cleared every 100metres for the passage of small game.

All trees of harvestable species, size andquality that are felled for road constructionshould be recovered, processed and marketed.

4.4.5 Sunlight exposure

Surface evaporation depends directly on theexposure of the roadway to sunlight andaeration. Crowns of large trees growing besidethe subgrade, prevent sunrays from reaching theground and the road from drying. Their removallengthens sunshine exposure and improvesaeration.

Clearing for sunlight exposure or laterallighting of a roadway is done by chainsaw.

CHAPTER 4

36

Figure 13 Road construction with excavator and bulldozer

Felling is not directional and trees are moved bytractor to the sides of the right-of-way. A fellingcrew can clear 1 000 to 1 500 metres ofroadside per month along a 10 to 30 m stripwithout undergrowth.

It is important to remember that:• clearing for sunlight exposure should always be

much broader upslope than downslope;• an East-West road near the Equator receives the

necessary sunlight exposure from a narrowerclearing than that needed for a North-South road;

• a roadway with clayey soil will need broaderclearing than one of sandy soil;

• a main road must always be more broadly clearedthan a secondary road.

In areas that are relatively safe from erosion orwhere the road does not need drying afterrainfall, canopy bridges should be maintained atregular intervals as these provide uninterruptedplant cover and thus aerial passage for certainmonkey species. It is worth mentioning that whileregular openings in roadside berms and heapsof debris and canopy bridges facilitate themovement of wildlife, they also provide hunterswith ideal vantage points to shoot and snaregame.

4.4.6 Roadway compaction and improvement

Forest roads are usually made of natural soil,compacted and where possible, upgraded with alayer of aggregate. Once the topsoil has beenremoved and the earth bladed, the natural soil isusually sufficient to serve as roadbed. Manytypes of soil are suitable provided that they arecompactable and relatively stable when wet.

In favourable circumstances, the natural soilcan serve as both carrying layer and surfacecourse, as in the case of laterite soils that have ahigh percentage of gravel. Natural soils ofmediocre bearing capacity because of high claycontent will require an extra thick layer ofaggregate, especially on vulnerable stretches.

In tropical areas, the aggregate is usually all-purpose laterite from local quarries containing amix of fine clay particles and coarser materials.Good distribution of particle size facilitatesstabilization after compaction. Gravel larger

than 30 to 40 mm should be avoided to facilitategrading, to prevent surface scouring and toenhance vehicle stability and safety. Theaggregate layer should have a thickness of 10 to25 cm before compaction.

Any natural soil used as roadbase must first bestabilized. Its bearing capacity needs to bestrengthened to make it operable under wetconditions, which can be done either throughcompaction alone or by adjusting thegranulometric range (adding required fractions,then compacting).

Straightforward compaction from rainfall andthe passage of earthwork machinery, trucks andcompactors is the usual form of stabilization offorest roads. Once the earthwork is complete, thenatural soil profile is shaped by grader and itssurface compacted. The road is then leftuntouched for a period of natural compactionfrom rainfall. Finally, before use, the base courseis re-graded, wearing-layer aggregate addedand the roadway compacted by roller. Any wellmanaged logging company will therefore haveits roads in place at least one year beforeharvesting.

The action of light rollers – whether vibratingrollers, sheep foot rollers or rubber-tyred rollers –is limited to packing the soil by making two tofour runs to obtain a surface course of about 10cm. This will consolidate the wearing layer andseal the surface to allow rainwater run-off. Whilecompaction reduces soil porosity and facilitateswater evacuation, some soils, especially clayeysoils, also need to be properly drained to keepsoil humidity well below the plasticity threshold ofclay fractions.

4.5 DRAINAGE: DRAINS, OUTLETS,CULVERTS AND BOX DRAINS

Protecting unpaved roadways against water-caused deterioration of bearing capacity, is aconstant concern of concession holders. Trafficon a roadway with impaired bearing capacitycauses surface distortion, ruts and potholes thatcannot be repaired until the end of the rainyseason, incurring major operational constraintand added cost. However, with appropriatestructures, water can be rapidly evacuated and

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roadways only superficially soaked and thusable to dry off within hours and sustain loggingtraffic. Penetration of water subsequent tomaximum compaction must therefore beprevented. Road degradation is usually causedby reduced stability of terrain or roadway fromthe action of water. Measures should be taken to:• avoid rainwater penetration of roadway and

capillary absorption;• ensure rainwater is evacuated by runoff;• ensure the different roadway layers are sufficiently

drained;• facilitate surface aeration.

4.5.1 Avoiding water penetration

Rainwater penetration is limited by reducedpermeability of upper road layers aftercompaction. The compactness and camberedshape of the roadway reduces surfaceabsorption, as water flows immediately to theside drains before being able to soak into thesubstrate. The roadway is cambered by graderafter earthwork. Maintenance at regular intervalsrestores the cambered profile and avoids waterpuddling. The cross-slope of the roadway has tobe a trade-off between a sufficiently steepgradient to permit rapid water evacuation and asufficiently gentle gradient to avoid washout andthus gully formation, and to ensure vehicle safety.The most effective crossfall gradient is thought tobe 3 to 5 percent.

4.5.2 Evacuation of rainwater runoff: side drains, outlets and culverts

Rainwater evacuation by drains should be asswift as possible. The side drains serve to collectroadway water and take it to outlets from whereit can be discharged without damaging the road.The bottom of the drain should be at least 60 cmbelow the road surface to avoid infiltration intothe roadway. A drain full of water permeates theroadway and seriously impairs its resistance. Thisis easily spotted from the deposits of mud or sandsediment.

Deposits blocking a drain and erosionthreatening roadbed stability need to beavoided. A light longitudinal gradient prevents

drain deposits, staying within 5 percent to avoidwashout. When draining steep roads, smallwaterbars can be laid to check waterflow andrestrain gullying, and to hold back sediment.

When a road is built in a cutting or on cut-and-fill sloping ground, it is often advisable to dig acatch drain above the cutslope to prevent runoffreaching the road. The catch drain has to beplaced sufficiently far from the top of the cutslope(4 to 5 m) to prevent infiltration that coulddestabilize the slope.

Side drains are generally traced by graderafter the earthwork, but can sometimes be dug oropened manually.

Outlets evacuate side-drain waters towardsnatural valley lines. Their number and spacingwill be based on direct ground observation.However, high outlet frequency is needed where:• side drains have a low gradient (below 3 percent)

and therefore slow water flow;• side drains have a steep gradient (above 5 percent)

and thus rapid water flow and an attendant risk ofgully formation.

The drainage outlets, opened by bulldozerduring earthworks at the same time as the sidedrains, follow the natural slope draining theroadside area. Their construction must meetcertain requirements:• they must actually discharge onto lower terrain (a

requirement often ignored, producing the oppositeeffect of outlets retaining water);

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Figure 14 Road drainage on flat terrain

• their width and depth must be at least the same asthose of the side drain they are servicing so thatwaterflow is equal or faster than that of the sidedrain;

• their slope must be the same or if possible greaterthan that of the side drain;

• they must lead off from the side drain at a relativelygentle angle of less than 30o to permit maximumwaterflow;

• they must be positioned at least 50 m fromwatercourses to prevent the intrusion of sediment.

On cut-and-fill sections of road where outletscannot be inserted into the cutslope, the sidedrain can only be discharged by means ofculverts that take the water across the roadway.If a road is to be in service for more than a year,a culvert has to be placed at each low pointalong the longitudinal profile. In the case of ahillside road, a culvert is required at eachthalweg.

Road class, expected life span and availableresources will determine the materials used.Using three logs to form a chute should beavoided as such a channel easily becomesobstructed.

Hollow trees: large-diameter hollow trees canbe used, always placing the narrower openingupstream to avoid obstruction.

Planks: a trench is dug across the road and 50x 50 cm or 60 x 60 cm wooden frames areplaced at 1.50 to 2 m intervals. The frames serveas stanchions for the plank casing. The trench isthen filled with earth and compacted.

Cement or metal culvert pipes with a diameterof more than 60 cm and as much as 2 m (it isbetter to install one single 1 m culvert than twoparallel 60 cm culverts). Soldered end-to-end,200-litre drums may be converted to inexpensivemetal culvert pipes.

Cement culverts can be made locally usingplank or sheet metal casts. They should becovered with at least 60 cm of earth and shouldrest on a carefully levelled bed of light concrete.Earth has to be carefully packed around theculvert to avoid crushing and water infiltration.Installing metal culverts requires specialprecautions:• a foundation of natural soil with good bearing

capacity. If the soil is loose, additional foundation isrequired, using non-scourable materials that arecarefully compacted. A flexible culvert pipe shouldnever rest on a hard rock or concrete base;

• a culvert will stay in place if the surrounding earthis firm and uniformly compacted in successive 25cm layers;

• a proportionate layer of earth should be placedabove the culvert: (50 cm of earth for a 60 cmculvert and 70 cm for a 200 cm culvert).

Culverts should have a cross-gradient of 1 to 3percent to facilitate waterflow, but no steeper toavoid scouring at outlet. If necessary, protectionworks (riprap, masonry or gabions) can be usedon highly erodible terrain to limit erosion atculvert point of entry and exit.

4.5.3 Drainage of roadway structure

Permanent drainage is required when a roadwayis infiltrated with water from precipitation, fromflooded side drains or from upward capillarityfrom deep water tables:• side drains should be built in such a way that their

base lies at least 60 cm below roadway level, thus

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Figure 15 Positioning a culvert


preventing prolonged water seepage to the lowerroad strata even with stagnant water in the drain;

• on terrain where the water table is close to theroadway surface, a thin, draining and highlypermeable layer should be inserted between thesubgrade and the roadbed to block capillary riseand evacuate water from the roadbed. A 10 cmlayer of sand and gravel usually works well. A layerof geotextile fabric is also suitable and should belaid on a fascine or sapling bed to avoid contact ormixing with subjacent soil.

4.6 CROSSING WATERCOURSES:DRIFTS AND BRIDGES

Watercourses can be crossed by drift or bridge,the latter being far more common in the region.

Temporary crossings for the passage ofconstruction machinery can be made by placinghardwood logs on the river bed in the directionof waterflow:• the width of passage should be limited to 4 m;• passage should follow the line of the road or

structure to be built;• disruption to vegetation in the buffer zone, on river

banks and along the river channel should be kept toa minimum;

• logs and accumulated debris should be removed assoon as passage is no longer needed.

4.6.1 Crossing by drift

A watercourse can be crossed by drift when:its banks are lower than one metre;the approach gradient is less than 10 percent;river depth above the drift is less than 0.5 metre; the river bed is solid gravel or rock.

Any intervention to improve the crossingentails:• minimal movement of materials, earthwork and

impact on river bed;• protection against scouring upstream and

downstream from the drift;• easy removal (e.g. of gravel used for reinforcement)

once the crossing is no longer needed.

4.6.2 Bridges

Forest bridges are usually built of hardwood withlong natural durability. They do not needchemical protection and, if built properly, canlast 10 years or more. They are generallydesigned for one-lane traffic of 50-tonne, five-axle timber trucks.

Choice of bridge site Choosing the site of a bridge requires knowledgeof watercourse regime as:• the bridge needs to be passable in all seasons, so

its deck should be at least one metre above thehighest water level ever recorded to permit passageof trunks and debris in floodwater;

• floodwater level will indicate the maximum width ofriver bed and thus the length of the bridge;

• the bridge should be as short as possible to avoidinserting intermediary supports (piers);

• it should be positioned at right angles to waterflow;• its approach should be in a straight line of at least

50 metres for safety reasons. A bridge should neverbe built on a curve;

• the bridge should be placed where the current is asregular as possible;

• it should be built on solid foundations, on a firm,non-scourable bed (e.g. rocks), if necessary at theexpense of minimal length;

• the positioning of the bridge determines roadalignment, not vice-versa.

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Figure 16 Correct siting of a bridge

Choice of bridge typeThis will depend on several factors:• available workforce, materials and equipment;• type of traffic projected: weight, length and width of

vehicles;• density of traffic;• physical location (steep banks and terrain relief

may impose a type of bridge);• size of watercourse, floodwater regime and volume

of debris carried by the current.

The bridge will have a single span if itsfloodwater width does not exceed 17 m.Intermediary supports may be envisaged in thecase of stagnant waters as these will not obstructwaterflow.

The substructure: abutments and piers The abutments support and anchor the bridgedeck.

a) Abutments made of log stacks

Bank abutmentA simple bank abutment is made of one or two70 to 100 cm diameter head (sill) logs placedacross an earthfill and laid flat on firm levelledground to support the stringers. This type ofabutment is used where the bank is sufficientlystable to preclude rockfall or subsidence. If theterrain is not sufficiently firm, the head logs areplaced on a crib of round or squared logs, thusdispersing the load and reducing the pressure onthe soil to an acceptable level.

Canadian log crib abutmentWhere necessary, to raise the bridge deck to ahigher level or to improve the anchorage of theabutment, the logs are stacked in right-angledlayers (cribbings) and bound together. Most arecovered by the backfill providing access to thebridge. This type of abutment, of which there aremany variations, is known as a bridge pier orCanadian log crib.

b) Concrete or masonry abutmentFor larger structures the abutments can be built ofstone or concrete. They also serve as retainingwalls and have to be stabilized against lateralearth pressure. This may be done by giving theabutment wall a stepped profile, creatingsuccessive setbacks in the wall so that the weightof earthfill on each step helps stabilize it. Anotherway of increasing abutment stability is to give thewall face a 1/10 slant. The width at the top ofthe wall should never be less than 1.5 m.

41

Figure 18 Bridge pier or Canadian log crib abutment

Figure 17 Bank abutment


c) Intermediary supports or piersIntermediary supports or piers are requiredwhere the watercourse is too wide for a singlespan. These are similar and require the sametypes of foundation as the abutments.

They can be built on dry ground (e.g. rockbed) for easier construction, or in the water. Piersdo not have to be placed on the main river bed;on the contrary, it is usually better to leave theriver flood bed clear.

Superstructure: stringers, trusses and deckinga) StringersStringers are support beams made of whole, sap-cleared or squared trunks. Since the bridges areconstructed for one-way traffic, four beams (twoon each side) are sufficient to form a 3.5 mroadway if placed under the vehicle wheeltracks. The respective stringer diameters ofLetestua durissima-Congotali (high tensilestrength) and Nauclea trillesii-Bilinga (lowertensile strength) to support 50-tonne five-axlevehicle traffic are:

*An additional diameter of 4 cm for 1 m extraspan is required for spans over 17 m.

b) DecksPlanks are the best and lightest material forbuilding decks. There are usually two types ofsuperimposed, cross-aligned deck, each servinga particular purpose:• the trusses (weight distribution deck), which are laid

at right-angles to the stringers, spread the carryingload equally among the superstructure. They are notconnected so as to facilitate rainwater runoff;

• the wearing deck, also referred to as the flooring, isintended to withstand the constant wear of heavyvehicle passage and is ideally made up of halfplanks laid at 45o to the bridge axis.

Laterite decking: where stringers cover the entirewidth of a bridge, 2 to 3 cm diameter saplingscan be laid in the gaps between the stringers;then the deck is formed by covering the wholestructure with a layer of laterite. Ideally, the litterof saplings and the layer of laterite should beseparated by geotextile fabric. Although thistechnique has the advantage of being simple, italso has certain drawbacks:the laterite adds an extra 3 to 5 tonnes per linear

metre;

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Span between stringers*

10 m 12 m 14 m 16 m 17 m

Congotali 58 cm 66 cm 74 cm 81 cm 85 cm

Bilinga 63 cm 71 cm 79 cm 86 cm 90 cm

Table 12. Diameter of stringers

Figure 19 Specimen forest bridge

• it retains moisture which is conducive to wooddecay;

• it is more difficult to spot the transition from road tobridge and to check the condition of the bridge atnight, which has implications for traffic safety.Laterite decking is however frequently used.

4.7 ROAD MAINTENANCE

Vehicular traffic and bad weather causedeterioration of roadway and drainage structureswhich has to be controlled by means of regularmaintenance and timely repair.

4.7.1 Regular maintenance

Reshaping road surfaceThis is necessary to counter the impact of traffic:• road wear and washboarding in the dry season;• rut formation and washout in the rainy season.

The constant passage of vehicles tends toproduce greater compaction along the wheeltrack than the rest of the roadway. Truck wheelsshear off gravel from the surface course and castit outwards. Together, these two actions produceruts and ridges that block lateral runoff ofrainwater to the side drains.

Maintenance involves early intervention toeliminate pre-rut surface scouring. Ejectedmaterials are replaced on the road and the roadprofile is restored, preferably by grader. Themost effective strategy is to repair roaddeterioration promptly in order to pre-emptserious, permanent distortion. The blade shouldonly be used to remove rippling ridges andshoulder berms, and should never cut into firmand stable roadway layers. Care must also betaken to avoid leaving sidecast along theroadside.

It is very important to choose an appropriateday for reshaping a road surface as the soilneeds to have optimal moisture content (whichwill depend on its clay composition) forcompaction after grading. Soil with too muchmoisture tends to become plastic and thusunsuitable for reshaping or compaction.

Filling potholesPotholes should be removed on sight, first dryingthem, then filling them with laterite. Filling withoutdrying is ineffective as the water will soak intosubjacent road layers and undermine bearingcapacity. Using laterite stones or pebbles to fill apothole is also ineffective as these will be pusheddown into the soft layers, leaving the problemunresolved.

Water runoff and drainage structuresThe road maintenance crew should also keepconstant watch over the state and function ofrunoff structures: drains, outlets and culverts.Inlets and outlets should be kept free of debris sothat water can run freely.

This also applies to bridge abutments andpiers. Any wood or debris likely to narrow theriver bed or restrict waterflow needs to beremoved. Bridge support beams need to bechecked regularly, as does the state of thewearing and distribution decks, renailing orchanging planks as necessary.

4.7.2 Resurfacing

Despite regular maintenance, a road canbecome worn from loss of materials. Newmaterials may therefore eventually be needed toreinforce and restore the roadway. Theoreticallythe only roads that require resurfacing are thosein permanent use, which means adding laterite atregular intervals. This will however bedetermined by traffic intensity, quality of roadmaterials, weather conditions and quality ofregular maintenance.

4.7.3 Other maintenance operations

Certain sections of road will not be very stable,with regrading required in cut areas withfrequent rockfall or landslip. This has to becleared quickly, preferably by excavator or front-end loader, and the side drain restored. A slopecan be considered sufficiently stable when loosesoil stops falling. It is less expensive to clearfallen rock or soil than to embark on expensiveearthworks during road construction, to obtain agentler sideslope gradient.

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4.8 IMPACT OF ROADCONSTRUCTION

There are two main types of impact:

a) The environmental impact on the forest, withroad construction clearing all vegetation andtopsoil from the roadbed. It takes several yearsafter road closure for nature to recover andrepair the damage; the road will gradually coverover, first with herbaceous vegetation (grass,climbers, etc.) then with shrubs (shoots,seedlings, etc.) and finally with trees.

b) The social impact, which may either bepositive or negative:

Positive:• access of local populations to resources (wood and

non-wood forest products) and relief from economicand social isolation;

• emergence of petty trade, markets and artisanalactivity along the roadside;

• improved living conditions for local populations(education, health).

Negative:• easier forest access for poachers and illegal

loggers;• disruption of social structure.

4.9 RECOMMENDATIONS

Reduced-impact practices in road construction:• plan the road network with due attention to

protected areas, avoiding as far as possibleenvironmentally sensitive areas and heritage trees;

• seek to align roads along ridgelines on gentle tomoderate terrain to facilitate drainage and uphillskidding;

• opt for an excavator rather than a crawler tractorfor cut-and-fill profiles to reduce volume of earthcutand the risk of erosion and landslip;

• avoid moving earth into watercourses;• keep sunlight exposure to the minimum necessary,

according to class of road, topography and type ofsoil of subgrade and base layers;

• retain canopy bridges and intersperse lateralearthwork with openings for the passage of certainspecies of monkey and game;

• construct and maintain appropriate drainagestructures for the collection and evacuation of water,avoiding any deterioration of roadway substrata,erosion of side slope and influx of sediment intowatercourses;

• avoid disruption to vegetation near watercourses, inbuffer zones and on river banks and beds duringconstruction works;

• remove all plant debris from buffer zones for burialin pits or earthfills.

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CHAPTER 5

«The intention of preparing this documentwas to concentrate on harvesting since itis the component of industrial forestry thatis most often subject to complaintsrelating to environmental damageassociated with forestry operations,especially in developing countries.» (FAOModel Code of Forest HarvestingPractice, 1996)

IMPLEMENTING HARVEST OPERATIONS

5.1 Controlled felling5.1.1 Preparation5.1.2 Controlled felling techniques5.1.3 Felling safety5.1.4 Felling impact5.1.5 Recommendations

5.2 Topping and butt trimming5.2.1 Topping5.2.2 Butt trimming5.2.3 Recommendations

5.3 Extraction5.3.1 Extraction techniques5.3.2 Characteristics of skid trails5.3.3 Construction of skid trails and landings5.3.4 Extraction impact 5.3.5 Recommendations

5.4 Cross-cutting, marking and preserving 5.4.1 Cross-cutting5.4.2 Log marking5.4.3 Log preservation

5.5 Loading and transport5.5.1 Loading5.5.2 Transport and unloading

5.5.2.1 Road transport5.5.2.2 Water transport

IMPLEMENTING HARVESTOPERATIONS

This chapter deals with actual harvestingpractices, from tree felling to loading andtransport of logs.

Objectives of the Code• to minimize detrimental impact on remaining stand,

soil and water; • to optimize harvesting efficiency, in particular

recovery level;• to safeguard forest yield and regeneration

capacity;• to promote stand increment in volume and value; • to employ competent and experienced personnel at

all levels; • to adopt and apply appropriate safety standards.

Merchantable trees in the tropical forests ofCentral and West Africa are irregularlydistributed and are limited in number andvolume. Preliminary planning is thereforeparamount to facilitate harvest operations;«facilitate» in the sense of minimizing negativeimpact and making operations safer and moreefficient. However, planning is meaningless if notapplied. A plan must therefore be intelligible toground crews so that they can apply it withoutdifficulty and operate in consonance withreduced-impact logging principles.

Interlinking planning with operations involvestwo actions:• general and constant use of the harvesting map that

provides an overall picture of the area to beharvested and shows the approximate position ofeach tree to be harvested, as well as significantfeatures of terrain (rivers, gullies, swamps, rocks). Italso indicates roads, landings, bridges and skidtrails.

• on-site briefing and instructions: the map serves asa point of reference for felling and extraction crews,enabling them to operate according to rules andregulations. Each crew should receive a copy of theharvesting map, together with clear instructions onoperational details and necessary precautions.

Unless supervisors make sure that groundcrews fully adopt the planning provisions shownin the harvesting map and actually put them intopractice, this planning document risks being nomore than an other useless, costly piece of paper.

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Figure 20 Harvesting map

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SECTION 5.1Objectives:• tto limit damage to the remaining

stand, especially to potential crop trees, heritage trees and regeneration;

• tto minimize timber loss during felling and optimize quantity and quality of timber harvested per tree;

• tto facilitate extraction by placing the log into a favourable position;

• tto maximize safety by applying appropriate standards, devices and equipment.

5.1 CONTROLLED FELLING

Felling is one of the activities that can causeserious damage to the remaining stand. Thecorrect working technique has to be applied inorder to recover the most precious parts of atrunk. At present, trees are often felled without aproper undercut or hinge, causing them to fall atrandom with resulting damage to the treesthemselves and to the remaining stand.Chainsaw operators often fell trees at chestheight without first removing buttresses, evenwhere the trunk has merchantable timber at itsbase. Such technically inadequate and poorlyplanned practices result in low timber recoveryand impact negatively on the remaining stand, inspite of the low harvesting intensity of tropicalmoist forests of West and Central Africa.

Felling is physically demanding, especiallywhen making the backcut, with the weight, heat,vibrations and noise of the chainsaw causinghigh physiological workload. Operators oftenhave to use chainsaws without any safety deviceand are not provided with personal safetyequipment. It is therefore imperative that loggingpersonnel be trained in correct workingtechniques in order to ensure maximum safety.

5.1.1 Preparing controlled felling

Using the harvesting map, the felling supervisorinspects the area to be harvested and assignseach feller a number of trees to be cut in a dayor week. Fellers working at the same time needto work in areas sufficiently apart to avoiddanger. After reaching a tree and checking andrecording its harvest number marked on the trunkor attached tag, the feller has to carry out certainobservations and actions regarding the tree andits immediate vicinity in order to:

a) Decide whether to fellAny dead or hollow tree has to be discarded.Trees showing signs of decay at their base needto be probed by machete or chainsaw. Thedecision to fell and the selection of fellingdirection are up to the feller who cannot beobliged to fell a tree that he considersdangerous. The feller has to identify potential

crop and heritage trees reported by the spottingcrew and decide how to avoid damaging them.Where this is not possible, and unless harvestingis taking place in a stand with an abundance ofcrop trees, the feller should desist.

b) Determine the direction of tree fallBefore making this decision, the feller examines:• the verticality of the trunk;• the estimated gravity centre of the crown (weight

distribution within the crown in relation to trunkaxis);

• the position of heavy branches;• the risk of lodging onto adjacent trees;• the risk of crashing onto a ground obstacle (rock,

gully bed) or against a large tree in the line of fall;• any attachment to the crown of a neighbouring tree

by liana, where visible;• wind direction and speed.

Where the preferred direction of fall deviatessignificantly from the natural lean of a tree, allthese factors imply that directional felling withoutauxiliary means is extremely difficult, if notimpossible in practice.

Felling can be considered «controlled» ifconducted by experienced, well-trained crews.Controlled felling means that the tree has to beharvested:• in the safest possible manner for the crew;• for the efficient recovery of the felled trunk; • without damage to the remaining stand and soil;• for greatest ease of subsequent log extraction.

The feller determines the direction of fall on thebasis of the most likely line of natural falldetermined by weight distribution between stemand crown, and the direction of fall required tominimize damage and facilitate extraction.

Where these two directions are different, thefeller has to note the natural lean of the tree and,where possible, manipulate the fall by applyingappropriate techniques. The extent to which atree can be felled in a direction other than itsnatural lean depends on the degree of lean, theweight of the tree and its species (mechanicalwood properties). A range of 30 degrees eachside of the imaginary line of natural fall is

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generally considered feasible. Beyond this,felling «against the lean» is consideredimpracticable and dangerous to crew safety.Using a tractor and winch as auxiliary means ismade difficult by the density and poor

visibility of tropical moist forests.

c) Prepare the tree for felling The feller and his assistant have to carefully:• clear the area around the tree of all obstructions

(low branches, brush) in order to create acomfortable working space;

• scrape off the bark at the butt of the trunk bymachete to remove pebbles or other objects thatcould damage the chainsaw;

• if necessary, cut all visible and accessible climbersaround and next to the tree.Several authors (Dykstra, Heinrich, Sist et al.)

advocate liana cutting at least six months beforefelling, especially in Asia. In Africa, however, itis often difficult to spot lianas in the forest canopybecause of the abundance of species and thevertical structure. Very few studies have beencarried out on this subject in Africa, and the onlysignificant ones question the utility of thepractice.

Further research is therefore required. Thiscostly activity should only be undertaken whenthere is a clearly visible dense web of lianasconnecting the crowns of harvestable trees toadjacent trees.

d) Ensure the safety of the felling crewThe feller should:• check for the presence of dead and potentially

dangerous branches;• check for the nearby presence of dead trees that

could shatter under the impact of the felled tree;• prepare two escape routes, cleared over a sufficient

distance and designed to enable rapid withdrawalduring tree fall. These routes should be at an angleof 135o to the supposed line of fall as a felled treecan sometimes slide back on its stump along theaxis of fall. The felling crew should only start towithdraw when they can clearly see the direction offall.

5.1.2 Techniques for controlled felling

The objectives of controlled felling are:• to avoid damage to potential crop trees,

regeneration and soil;• to ensure maximum safety for the felling crew;• to use as much of the felled tree as possible;• to facilitate favourable log position for ease of

extraction.

Controlled felling involves:• making an undercut and a backcut to create a

hinge and predetermine direction of fall to within30° of either side of natural lean and thusguarantee a low-impact, efficient and safe fall;

• applying an undercut (scarf) and a backcut (mainfelling cut) as close to the ground as possible toobtain maximum volume of the most valuable partof the bole;

• removing buttresses and thus reducing the basalarea of the trunk in order to proceed more quicklywith the felling cut and avoid wood wastage (tornfibres from premature fall).

The tool most commonly used for commerciallogging in Africa is the chainsaw. Currentlyemployed models have a power rating of 7 to 9HP and a guide bar length of 70 to 90 cm. Theactual felling operation consists of foursuccessive phases:

CONTROLLED FELLING

51

Figure 21 Escape routes and clearing around tree base

a) Determining felling heightTrees should be cut as close as to the ground aspossible. Trees with few or no buttresses can befelled 30 cm above the ground. Otherwise thebuttresses have to be removed for easier cuttingat a height permitting maximum timber recoveryat the base of the trunk.

Trees whose basal area does not havesufficient hinge wood to guide the tree during itsfall (rotten wood or species with a conical baseand pronounced plank buttresses) should befelled at a height where the stem has enoughhealthy wood in the central cylinder to form asufficiently strong hinge. Whatever technique isapplied, the operator should be able to keepboth feet firmly on the ground and maintain astable working position throughout the fellingprocess.

b) Removing buttressesMany tropical tree species have buttresses thatshould, whenever possible, be removed to obtaina cylindrical bole shape, reduce the basal areaand enable the backcut to be completed beforethe tree starts to fall.

The complete removal of buttresses before

felling presents a number of advantages:• the cylindrical base of the bole makes it easier to

apply the undercut and backcut as close to theground as possible;

• the direction of fall is easier to control as theundercut can be placed in the central area of axialfibres;

• there is less risk of fibre splitting, since the backcutcan be conducted more quickly;

• it permits the recovery of timber at the base of thestem that would otherwise be left on the stump.

With regard to its implications for fellingpractices, we distinguish three differentsituations:• trees with cylindrical base and moderate buttresses (i);• very large trees with cylindrical base and

pronounced buttresses (ii);• trees with conical base and buttresses in the form of

high thick planks (iii).

(i) Moderate buttresses are removed in such away that the base of the tree becomes acylindrical bole by applying a horizontal and avertical cut that join in a straight line. Thehorizontal cut should never exceed the cuttingplane of the vertical cut.

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Figure 22 Trunk cylinder (1), basal area (2), cuttingheight (3) and conical part (4) of a trunk with plankbuttresses.

Figure 23 Removing buttresses

(ii) In the case of trees with a very largediameter and a cylindrical base, it may benecessary not only to remove the buttresses butalso to reduce the diameter of the trunk in orderto apply the felling cuts. The trunk is trimmed withtwo 45o cuts or, if necessary, three cuts leavingmore room to manoeuvre the chainsaw. Anotheroption is to raise the felling height to a levelwhere the trunk size is easier to handle for thechainsaw operator, although this impliesconsiderable loss of timber.

(iii) The buttresses are not removed wherethey exist as high thick planks and where theconical base cannot provide enough hinge woodto hold the weight of the tree. Since the effortrequired in such cases to remove the buttresses isnot justified by better timber recovery or workingsafety, the felling cuts are made with thebuttresses in place (see Figure 24).

c) Making the undercutThe undercut or felling notch forms one part ofthe pivotal hinge around which the tree will tiltand fall to the ground. This hinge has twopurposes: it determines the direction of fall andbreaks the last uncut fibres by free flexion. Thefelling notch performs this dual role through itsorientation and angle of aperture.

The felling notch has to have the followingspecifications:• a depth of 1/5 to 1/3 of stem diameter;• An angle between top cut and bottom cut of 30° to

45°, with the lower cut horizontal;• a straight chord (without overlapping cuts), its

perpendicular indicating the direction of fall.

The direction of fall is determined by theorientation of the felling notch. Because of theparticular size characteristics of tropical trees,the undercut can only manipulate tree fall towithin 30 degrees either side of natural lean.

The undercut comprises two cuts, onehorizontal and the other at an angle of between30 and 45 degrees. The first is appliedhorizontally into the side of the fall to a depth ofone-fifth to one-third of the diameter of the stembase. The second cut is slanted at an angle of 30to 45 degrees with the horizontal cut which itshould meet along a straight line (chord)perpendicular to the direction of fall.

The line where the top and bottom cut meet (thechord or hinge edge) must be perfectly straightand perpendicular to the line of fall. The top andbottom cut forming the edge of the hinge shouldnot extend beyond their intersection, if the hingeis to function properly. If the base of the undercutis not horizontal, the bending stress causessignificant tension which can lead to fibre tearing.

With fragile species (Okoumé, Mahogany,Limba), any buttress in the line of fall should beremoved to prevent it from acting as a wedgeagainst the stem base and causing it to burst.

The greater the lean of tree, the deeper theundercut has to be to reduce the risk of splittingin the butt end. The straighter and more balanceda tree, the more the undercut can be restricted toone-fifth of the apparent diameter.

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Figure 24 Configuration and sequence of cuts whenfelling trees with buttresses and conical base, (1) withand (2) without wedge.

d) Making the main felling cut or backcutThe main felling cut or backcut has to be higherthan the undercut. During its fall, the stem has tobe able to rest on the rear of the stump so that thefeller working behind the tree can operate incomplete safety.

The best results are obtained when there is a 15to 30 cm difference in height between the bottomof the felling notch and the backcut. In the case ofspecies with sapwood tending to split, a shallowcut should be made on either side of the hinge.

The backcut should proceed in such a way thatthe hinge (the uncut wood between the chord ofthe felling notch and the line of the backcut)remains symmetrical to the direction of fall. Byguiding the chainsaw from one side of the stem tothe other, the feller tries to cut parallel to the notchchord in order to achieve the necessary symmetry.

There are different backcut techniques fordifferent trunk diameters:

(i) If the diameter is bigger than the length ofthe guide bar, the cut begins on the right side(looking towards the direction of fall) and thenmoves in various stages around the trunk towardsthe left. There are two opportunities to check thatthe back of the hinge forms a straight line: afterstarting the backcut and when reaching theopposite side.

If the trunk is equal to or more than twice thelength of the guide bar, a plunge cut is requiredfrom the side of the felling notch in order to severthe centre of the trunk. The fanlike felling cutexplained above is then applied.

5.1.3 Felling safety

Felling in closed tropical forests is verydangerous for the operator, as the density ofundergrowth obstructs visibility and retreatduring tree-fall. Torn or dead branches falling offthe crown as well as decaying or rotten trees areanother potential cause of serious accident.

Risks when felling in tropical forests wheretrees are intertwined and their crowns interlacedwith lianas are:• falling trees often bring other trees down;• branches of falling or adjacent trees break and fall

or kick backwards; • lianas are torn and cause whiplash.

Important rules for preventing accidents duringtree felling:

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Figure 25 Diagram of the principle of chainsaw felling Figure 26 Fanlike felling cut (trunk diameter biggerthan length of guide bar)

• felling should only be done by skilled, trained andhealthy workers who use chainsaws fitted with allsafety devices (including anti-vibration systems andchain brakes activated manually and automaticallyin the case of kickback), the shortest possible guidebar and personal safety equipment;

• never move around with the saw chain in motion;• a properly sharpened chain makes work easier and

raises productivity and safety. Mechanical

sharpening of chains at the camp workshop isrecommended, with the feller depositing the usedset of chains in the evening and picking up a newset of sharpened chains for the next day. The chainsare better and more quickly sharpened this waythan having the chainsaw operator sharpen themhimself at the felling site;

• workers should dispose of and wear appropriatesafety equipment:• a safety helmet and protective footwear are

essential, although some fellers still prefer to workbarefoot;

• face shields (visors) and ear muffs are alsoessential, although uncomfortable in a tropicalclimate;

• safety trousers in fluorescent colours arerecommended;

• just as dead branches and large lianas have to bespotted before felling, care is also needed overcrowns or branches broken by the falling tree,whether from the felled tree or from adjacent trees;

• the feller should always give a warning shoutbefore starting the backcut and should only proceedon hearing no response;

• once the felling of a tree has been started, it mustbe completed;

• lodged or hung-up trees must always be brought tothe ground by skidding tractor winch and cable.Never cut adjacent trees or the tree holding thelodged tree to make it fall. Never work below ahung-up tree and never buck the stem nor climb onit to bring it to the ground.

• tree felling should be suspended under windyconditions as the wind can affect the direction of fall.

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Figure 28 Configuration and sequence of cuts for fellingtrees with a (1) forward and (2) sideward lean

Figure 27 Plunge backcut (trunk diameter equal to or morethan twice the length of guide bar)

5.1.4 Felling impact

Poorly conducted or controlled felling can havethe following negative impact:• extensive damage to the remaining stand (broken

branches, topped or uprooted trees);• financial implications as damage (ring shakes,

splits, cracks) incurs significant loss of timber; • risk to life and health of workers.

5.1.5 Recommendations

Reduced-impact harvesting practices in felling:Controlled felling techniques are used to have

trees brought down into already existing gaps,along skid trails or onto the crown of an alreadyfelled tree to break its fall and avoid damage tothe remaining stand.

Where possible, tree-fall should be at an angleof 30° to 60° to the skid trail to facilitateextraction.

The felling of a exploitable tree could break ordamage several close future crop trees becauseof its direction of lean. In such cases, the head ofthe spotting crew should inform the harvestingsupervisor who decides whether the stem inquestion should be felled or not.

Trees should not be felled downwards on hillyterrain, unless this is unavoidable. Felling inparallel to contour lines reduces the risk ofbreakage to felled and adjacent trees.

Felling should cause minimum damage to soiland watercourses, and particular care should betaken to avoid bringing trees down acrosswatercourses. Where this occurs, trees should beextracted carefully, causing the least possibledamage to banks and debris should be removedfrom sensitive zones.

Trees beside a sensitive zone should be felledoutwards from the zone.

Crowns and branches should not be moved orextracted from the forest, but left to decomposeon site.

Controlled felling reduces timber loss andharmful impact, raises productivity and safety,and facilitates all subsequent operations. It istherefore essential to give felling crewsspecialized basic training in controlled fellingpractices, followed by periodic refreshertraining.

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SECTION 5.2Objectives:

• to ensure maximum safety byapplying recommended cuttingtechniques;

• to maximize timber recovery fromfelled tree;

• to trim the log for more efficient andcareful extraction.

5.2.1 Topping

The crown is always separated from the trunk atthe felling site. Crown removal or topping isnormally done under the first large limb. It can bedone by the feller himself immediately after felling,by a special crew operating a few days or severalweeks after felling, as dictated by the species(many loggers prefer this practice which allows thetree to settle before extraction, to release sappressure and thus to eliminate or reduce theinternal tensions that can trigger splitting) or at thetime of extraction by a chainsaw operator workingalongside the skidding crew.

In the case of fragile species, the work has tobe done quickly to provide freshly felled timberand to reduce the risk of insect or fungal attackand thus avoid chemical treatment.

5.2.2 Butt trimming

The stem base is trimmed whenever its weight orshape could hamper extraction. Butt trimmingtakes place at the same time as topping. It is notnecessary if the buttresses have been corneredbefore felling or when the operator removes thembefore skidding to facilitate movement andrecover an extra section of timber.


Topping and butt trimming are done in the forestunder difficult conditions of work and visibility(the trees often lie in awkward positions, cuttingsites are not very accessible, the distribution oftensions is difficult to gauge), so experiencedcrews trained in RIL techniques and safetymeasures are required.

Reduced-impact harvesting techniques fortopping and butt trimming:• create conditions for the marketing of hitherto

abandoned grades and dimensions (timber from theflexuous parts of the bole and the large limbs);

• give clear instructions to felling crews on requiredgrades, lengths and diameters;

• top beyond the first large branch, to the extentpossible;

• again to the extent possible, recover trunk butts withbuttresses by cutting lengthways to obtain acylindrical shape.

It may be useful to do the topping and butttrimming at the same time as the extraction, ascombining these activities helps recover morewood and enhances safety for the chainsawoperator, as it clears the cutting site that mayotherwise be obstructed by tangled branches.

On the other hand, it means the crawler tractorhas to enter the clearing, which causes moreserious damage than if it were only to winch thepre-topped trunk or position it for extraction.

This method should therefore only be adoptedwhere a tractor is absolutely vital to ensure safeand efficient topping, and to avoid wastage oftimber. Before engaging in heavy extraction entry,all other necessary measures should be taken toensure maximum safety and recovery, training ofcrews in cross-cutting techniques (cf. 5.4.1) andencouragement of routine implementation throughmonetary incentive (see Chapter 9).

The choice of best topping and butt trimmingpractice, and the decision whether to extract thetimber in trunk or log form (see 5.3.5) will dependon local conditions (size and tensions of tree to betopped, accessibility of crown and topography ofterrain). In any case, the action chosen will haveto meet the three RIL operating criteria: maximumrecovery of timber, maximum safety and minimumimpacts throughout production (felling, conversionand extraction).

Wood hitherto left in the forest should be usedto maximize returns from the resource and easepressure on the forest. Tree waste at the felling siteshould be recovered, although this does facilitatepoaching and illegal logging. Conversion offcutsshould be regularly collected from landings andtaken to processing plants outside the forest orprocessed on-site in mobile sawmills.

Cross-cutting techniques applying to toppingand butt trimming are explained and illustrated indetail in Section 5.4.

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SECTION 5.3Objectives:

• to minimize damage to remainingstands, soil and watercourses;

• to minimize disturbed areabetween skid trail and roadnetworks;

• to reduce soil compaction by usingappropriate technology and low-pressure tyres;

• to optimize extraction productivityand safety.

5.3 EXTRACTION

Extraction is the first stage in the transport of logsfrom stump to sawmill log yard. Since it involvesmoving logs from felling site to roadside landingby means of heavy equipment, it can cause severeimpact on the environment in a variety of ways.

First, the tractor clears a track to the logs to beextracted, uprooting and toppling trees along theway. The tractor blade is sometimes used tograde the soil for easier skidding.

The logs are then dragged along the ground,disturbing the soil (erosion and sedimentation ofstreams) and damaging trees next to the skidtrail. Watercourses crossed can be contaminatedby debris and leaking fuel or lubricant.

Because of their versatility crawler tractors areused much too often for skidding, causing farmore damage to the remaining stand and soilthan wheeled skidders.

With increasing terrain slope skidding damageincreases dramatically (vast areas are clearedand disturbed by crawler tractor for levelling andpre-skidding).

Timber extraction is in two stages:a) Pre-skiddingDuring pre-skidding, logs are moved up to 30metres from the felling site to the nearest point ofaccess of the wheeled skidder. This should, as faras possible, be done by winch and cable.Approaching a trunk by crawler tractor shouldbe the exception, resorted to for instance, whenthe trunk has become stuck during winching anda tractor blade is required, or when a tree hasfallen into a difficult position for skidding onrugged terrain.

Using a tractor blade should also be theexception. The direction of tree-fall shouldnormally be the angle best suited for winching tothe skid trail without the need for repositioning byblade. The cable on the crawler tractor winchshould be at least 30 m long.

b) SkiddingThe logs are then dragged along the skid trail tothe landing for subsequent loading. Skidding isin one or two phases covering some hundreds orthousands of metres, beyond which it is moreeconomical to build a secondary or feeder road

to haul logs on trucks rather than drag themalong the ground.

5.3.1 Extraction techniques

The only technique actually used in the denseproduction forests of tropical Africa, once monthlyproduction exceeds 1 000 m3, is skidding bycrawler tractor and/or articulated wheeledskidder equipped with winch and cable. Othermethods involving draught animals, cableyarding, balloons or helicopters are not employed.

The decision on the type of machinery to usewill depend on:• the size of the logs;• the harvested timber volume per hectare;• the topography and soil conditions;• the appropriate road network density.

Crawler tractors have greater tractive powerthan wheeled tractors for the same weight andengine size, which is why they are preferred forskidding large logs, where high tractive power ismore important than high speed of travel.

Crawler tractors:Two main types are used: the 215 HP class andthe 175 HP class.

Wheeled tractors: Nowadays almost all models of articulatedtractor are in the 190 HP class .

All machines should be equipped with askidding winch attached to the rear. The choiceof tractor model will depend on the size of logs,topography and terrain:• in the case of rugged terrain with medium-size trees,

a lighter crawler tractor with greater manoeuvrabilitywill be preferred to a more powerful but heaviermachine.

• wherever possible, wheeled tractors should be usedas these are more mobile, easier to manoeuvre andless detrimental to the soil and remaining stand.

Crawler tractors cause extensive damage tothe soil and their use should be restricted to thepre-skidding of logs that are too heavy to bewinched by wheeled tractors under difficult

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conditions. Crawler tractors should always stayon the skid trail and haul logs by winch. Movinga log with the blade should only be permittedunder exceptional circumstances.

On gentle terrain (gradient below 20 percent),a wheeled logging arch can be hooked to thecrawler tractor. This device, which consists of aprojecting arm mounted on a wheeled chassis,lifts the log at one end and thus eases the weighton the tractor. The head of the arch is fitted withfour rollers that guide the winch cable to anelevated position. The advantage of using alogging arch is that it reduces ground friction andthus log resistance. It also reduces soil scouringand enhances tractive power. However, it makesthe tractor more difficult to handle and can easilycause it to tilt over when lateral traction is toostrong.

There are two possible extraction procedures,depending on terrain conditions, exploitabletimber volume and size of trees: single-stageskidding directly from stump to roadside landing;

and twin-stage skidding with conveyanceinterrupted at an intermediate landing halfwaybetween stump and roadside landing.

Single-stage extraction is employed:• on easy terrain that permits a high-density network of

comparably inexpensive roads, conjugated with shortskidding distances of a few hundred metres at most;

• in a forest with medium-to-high intensity timberextraction where investment in road constructioncan be easily recovered.

Single-stage extraction is usually by crawlertractor, sometimes wheeled skidder. Crawlertractors operate alone, while wheeled skiddersgenerally operate in tandem with crawlertractors, the latter extracting the larger trunks, theformer the smaller and lighter stems along pre-opened trails.

Twin-stage extraction applies:• on difficult terrain where increased skidding

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Figure 29 Methods of tractor extraction

distance is the necessary consequence of low roaddensity. The respective roles of the crawler tractorand the wheeled skidder are then clearly defined.The crawler tractor travels to the vicinity of the trunkas it alone can operate on very steep and ruggedterrain, blading its own trail if necessary and italone has the capacity to extract trunks from difficultpositions. The wheeled skidder is then used to movethe cross-cut logs along the skid trail;

• in a forest with low extraction intensity, where two-stage skidding is an appropriate method ofextracting timber with minimum investment in aroad network.

Two-stage extraction comprises:• primary skidding by crawler tractor along a few

hundred metres from stump to intermediary landingwhere the logs are cross-cut;

• secondary skidding along 500 to 2 000 metresfrom intermediary to roadside landing by wheeledskidder on trails opened and, if necessary, levelledby bulldozer.

A skid trail carrying a large number ofskidding cycles can in fact be equated with asecondary road.

Although crawler tractors are often used for thefirst stage of extraction (which in this casecorresponds to extended pre-skidding), their useshould be restricted to initial winching during pre-skidding, leaving most of the distance to becovered by wheeled skidder to lessen thedetrimental impact of extraction.

Skidding should be upwards towards theridgeline where possible, since:• runoff waters flow towards adjacent vegetation and

not onto the main trail;• the number of watercourses to be crossed is

generally lower;• it is easier for the driver to control load and tractor,

particularly on wet soil;• it is easier for the helper to carry the log cable

downwards;• there is greater operational safety for workers and

equipment.

5.3.2 Characteristics of skid trails

There are two types of skid trail:• Main trails designed to withstand more than 10

skidding cycles. These are generally laid out alongridgelines to facilitate upward skidding and may bebladed.

• Secondary trails used for one or a few cycles whoseclearing does not involve blading, except ondifficult terrain.

Shrubs and small stems cut while clearing thetrail should be left on the trail bed as a protectivelitter against compaction and erosion.

5.3.3 Construction of skid trails and landings

Objectives of this Code:• to minimize the size of landings and thus reduce the

cleared productive area;• to build landings and trails in such a way that

watercourses are safeguarded;• to reduce damage to the soil;• to minimize gradients and keep them within 20

percent if possible;• to promote skidding towards ridgelines and restrict

the crossing of watercourses;• to optimize efficiency, productivity and safety of

operations.

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Figure 30 Trail network for skidding towards ridgeline

The landing and skid trail layout was alreadyplanned and ground-marked by machete or tapewhen preparing the harvesting area (cf. 3.5.2).

Roadside landings are generally prepared atthe same time as the secondary roads. However,where the extraction process involvesintermediate landings in the forest, these arecleared at the same time as the main skid trail.As a general rule, main skid trails are establishedbefore felling, while secondary trails can quiteeasily be laid out afterwards, provided they havebeen marked beforehand.

Landings

LocationThe location of landings should be indicated onthe harvesting map. They should be:outside protected and environmentally sensitive areas;• at least 30 metres from environmentally sensitive

areas;• on dry, well-drained or easy-to-drain terrain,

preferably along a ridgeline or on a gentle slope tominimize cut-and-fill earthwork;

• on a site where mud, debris from cross-cutting andother waste cannot reach watercourses;

• at the entrance of one or several skid trails.

The number of landings should be kept to aminimum to reduce the area cleared forinfrastructure. A landing is not needed if a trailonly evacuates a few logs which can be buckedand loaded at the roadside.

However, a landing should never be placed onthe side of the road opposite to that of the skid

trail and tractors should not be allowed to crossa road while skidding a log, as buttress wingscan cause severe harm to the roadway, and thecompacted surface course can suffer damagethat even prompt filling and grader resurfacingcannot repair. The result would be a road sectionvulnerable to potholes and infiltration ofrainwater.

Size of landings The average roadside landing covers 600 to 1200 m². In-forest intermediary landings aregenerally smaller because they only serve astransit points and not as repositories of bufferstock, which is sometimes a function of roadsidelandings. Ideally, landings should not cover morethan 1 000 m².

Construction and use of landingsLandings are levelled with the equipment used forroad construction. Their utility is by naturetemporary, as limited to the duration of timberevacuation. Grading should be designed tofacilitate the drainage of rainwater. Earthworkberms, bucking waste, bark and sawdust shouldbe disposed of in such a way as not to impededrainage.

Where possible, the humus layer removedduring grading should be stored separately forre-laying after the completion of operations.

Levelling a landing site by tractor blade shouldbe avoided during the rainy season to keep itoperational.

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Figure 31 Location of a landing

Skid trails

Any skidding in protected areas is of courseprohibited. Skid trails should be located:• at some distance from watercourses and unstable

terrain;• away from environmentally sensitive areas close to

river banks (any authorized felling in these areasshould always be away from the stream and thetrees extracted by winch and cable);

• on ridgelines to facilitate drainage;• with due care for future crop or heritage trees.

Waterway and gully crossings should be keptto a minimum and should always be less than 4m in width. Where unavoidable, crossingsshould run at right angles to the bank on a rockor gravel bed. Otherwise, the bed should beprotected by logs (bolts) laid parallel towaterflow, subsequently removed after skiddingto restore the water regime.

ConstructionSkid trails can be opened by machete, chainsaw(low cut) or tractor.

a) The low cut is recommended for secondarytrails that will only be used for one or a limitednumber of skidding cycles. Cut material can beleft where it is to protect the soil. This is theenvironmentally soundest practice as crews openthe trail along a marked course and clear nomore than tractor width, while their dailyproduction target is measured in length of skidtrail cleared.

b) Skid trails can also be opened by wheeledskidder clearing its own trail as it moves alongthe path indicated by the marking crew, or bycrawler tractor working for one or severalwheeled tractors. Main skid trails are clearedwell before extraction.

The wheeled tractor is only used for easyterrain and sparse undergrowth as it is not suitedto this work, its blade being too weak and poorlypositioned to clear, and much less grade a trail.

Certain operational rules need to be observed:• no grading should be allowed on trails with a

gradient of less than 20 percent;• maximum gradients should be 25 percent for main

trails and 45 percent for secondary trails;

• the maximum gradient for laying a cut-and-fill trail is45 percent;

• cut-and-fill grading should be forbidden onsecondary trails and avoided on main trails;

• cut-and-fill trails should have a cross-slope of 2 to 5percent for water runoff;

• the maximum width should be 4 m, i.e. the width ofa tractor blade;

• trails should be as straight as possible, avoidingtight curves that could damage trees beside thetrail.

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Figure 32 Provisional crossing of a watercourse using bolts

5.3.4 Impact of extraction

The following impact is always extremelynegative:• soil damage caused by the clearing of trails and

landings and the passage of heavy machinery andlogs: various degrees of soil compaction, rutting,leaching and scalping;

• log-caused damage to vegetation and bark woundson trees beside the skid trail.

Precautions to reduce this impact:• the least blading possible; clearing by machete and

laying branches on the ground as protective litter;• trails as straight and narrow as feasible;• optimal log length according to terrain and

sinuosity of skid trail;• butted logs (without buttress wings).


Reduced impact logging practices for skidding:Opening of trails and extraction by crawlertractor should be limited to terrain with amaximum gradient of 45 percent (20 degrees),above which either other extraction techniquesshould be used or the area should be classifiedas non-harvest.

The tractor operator should stick to the flaggedroute and avoid opening new trails.

Trails should be as straight as possible,avoiding excessively tight curves that coulddamage trailside trees during skidding.

Equipment should be appropriate to terrainand load (low-pressure tyres).

Whenever possible, extraction should be bywheeled tractor, winch and cable.

With or without load, tractors should alwaystravel with their blades raised. The driver shouldonly lower the blade when needing groundsupport, as for winching.

The tractor is generally not allowed to leave thetrail, particularly during pre-skidding. The trunkshould be moved away from the stump by winchaction and not by pushing it with the blade,which is still the general practice because driversand helpers are inadequately trained.

The tractor should never shovel itself into theground for winching; it is better to lock againstan unprotected tree, which can then be sacrificedif necessary.

The choker-setter should know how to place thecable so the log rolls into a better position forwinching.

The tractor should always winch in a straightline, i.e. the tree, cable and winch should formone line and never be at an angle.

The driver should always reel in the winchcable to the top to wedge the log under thewinch and raise it as high as possible off theground.

Workers should never stand between the winchand tree during winching. Whiplash from abroken cable can be fatal.

When skidding downhill, a driver should neverallow a log to pass the rear of the tractor, muchless slide along the side of the tractor.

Although maximum timber recovery requiresthat the whole stem be extracted for optimalbucking at the landing, a log may sometimeshave to be cross-cut at the felling site to reduceextraction damage. The best course of action willhave to be determined on the basis of the localsituation (length and weight of log, terrain andtractive power of machinery).

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