timber supply analysis technical report · tfl 52 is composed of two blocks: block a is located to...

Tree Farm Licence 52 Management Plan #5 Timber Supply Analysis Technical Report

Presented To: West Fraser

Dated: September 2018

Ecora File No.: KE-11-069

TFL 52 Management Plan # 5 – Timber Supply Analysis File No: KE-11-069 | September 2018 | Version 1

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Version Control and Revision History

Version Date Prepared By Reviewed By Notes/Revisions

Draft 10 Sept 2018 Miehm Sakakibara

1 12 Sept 2018 Miehm MFLNRO



Executive Summary

West Fraser is completing a timber supply analysis for TFL 52 in conjunction with the preparation of Management

Plan #5. This Analysis Report builds upon the data and assumptions presented in Tree Farm Licence 52

Management Plan # 5 Timber Supply Analysis Information Package (dated March 2018. That document was

advertised for public review and submitted to the Ministry of Forests, Lands and Natural Resource Operations

(MFLNRO). It was accepted by MFLNRO on March 15, 2018, for use in this timber supply analysis.

TFL 52 is composed of two blocks: Block A is located to the east of Quesnel and Block B is northwest of the city.

The total area of the TFL is 261,468 hectares. Of this, 242,688 hectares is productive forest and 174,884 hectares

is available for timber harvesting (i.e., the timber harvesting land base – or THLB). The forests of TFL 52 are

dominated by interior spruce, lodgepole pine, and Douglas-fir. The TFL has a long history of harvesting, but a

significant amount of older timber remains. Fifty-nine percent of the THLB is occupied by stands 60 years of age

or younger. Mature stands (older than 120 years) cover 26% of the THLB. The remaining 15% of THLB stands

are between 60 and 120 years old. Most stands have a site index of between 10 metres and 25 metres. The area-

weighted average site index is 16.9 metres.

This timber supply analysis was carried out using the Patchworks™ forest estate model. It is a multiple-objective,

spatially explicit goal-programming model that builds harvest schedules while balancing trade-off between

environmental, economic and operational goals. This analysis used a two hundred and fifty (250) year planning

horizon that was modeled in fifty five-year periods.

The base case presented is this document shows that a harvest level of 570,000 m3/year is possible for the next

twenty years. After twenty years the harvest level jumps to 660,000 m3/year and then climbs slowly for the next

130 years to the long-term sustainable level of 784,500 m3/year. The growing stock at the end of planning

horizon (32 million cubic metres total, with 22 million cubic metres above minimum harvest age) is sufficient to

support continued operations at the sustainable long-term harvest level presented.

The only constraints placed on the harvest level itself was that if be constant over the first four five-year periods,

and over the final 20 periods (i.e., 100 years). An additional constraint required that the growing stock be constant

by the end of the planning horizon. The charts below show the resulting harvest levels and growing stock (both

total and above minimum harvest age).

The harvest pattern found in this analysis is not surprising. The timber supply analysis for the previous

management plan (MP#4) predicted that harvest levels would have to decline once the MPB salvage program

ended. TFL 52 is now in the timber supply trough predicted by MP#4. The trough is only slightly deeper than

expected, due in large part to the land base reduction related to the creation of the Cascadia TSA and (perhaps)

because MP#4 was slightly optimistic about the proportion of dead pine that would be recoverable.



Summary statistics of the harvest profile were compiled and presented in the body of this report. Briefly:

Average harvest age falls sharply over the next thirty years and stabilizes in the long-term at an average

of 69 years;

Even in the long-term stands older than 100 years make up 10% of the harvest volume;

Harvest volume per hectare averages 315 m3 over the next fifty years. In the long-term this rises to 372

m3; and

Pine volume is in short supply now but will recover; by the end of the planning horizon, 57% of the

harvest comes from spruce-leading stands, and 24% comes from pine-leading stands.

The current and future age class

distribution on the THLB is

shown in the figure to the right.

There is a slight excess of older

age classes (older than 120

years), and this is somewhat

reduced over the course of the

planning horizon. Many of these

older stands are retained to

meet visual quality objective and

habitat values. By the end of the

planning horizon, 80% of the

THLB consists of stands

younger than 80 years of age.

Many sensitivity analysis runs were completed to understand how the harvest levels would change if the

underlying data and assumptions were varied. The table below lists these runs and the harvest level results

relative to the base case.

Sensitivity

Harvest Volume (m³/yr) Change from the Base

Case

Short

Term

Long

Term

Short

Term Long Term

Base Case 569,922 784,550 100.0% 100.0%

natural yield plus 10% 640,863 796,427 112.4% 101.5%

natural yield minus 10 % 525,106 792,291 92.1% 101.0%

managed yield plus 10% 590,980 869,245 103.7% 110.8%

managed yield minus 10 % 560,126 703,444 98.3% 89.7%

minimum harvest age plus 10% 430,483 757,910 75.5% 96.6%

minimum harvest age minus 10% 585,335 794,643 102.7% 101.3%

regen delay 0 years 588,318 792,920 103.2% 101.1%


no early seral patch targets 654,982 811,120 114.9% 103.4%

no watershed HEDA limits 587,539 794,824 103.1% 101.3%

HEDA plus 10% 585,646 794,041 102.8% 101.2%

HEDA minus 10% 561,648 776,894 98.5% 99.0%

VQO increased one category 553,574 770,392 97.1% 98.2%

VQO decreased one category 597,621 803,128 104.9% 102.4%



The sensitivity analyses around minimum harvest age shows the precarious nature of the current timber supply

situation. Lowering MHA by 10% provides only a modest increase in short-term timber supply – but increasing

MHA by 10% cuts the short-term (i.e., the next 20 years) harvest level by almost 25%. The immediate harvest

level is very closely tied to assumptions about when the oldest existing managed stands will first become

merchantable.

The current harvest level is also sensitive to disturbance constraints that protect visual quality and watersheds. If

these are relaxed, short-term harvest levels can rise slightly – by between 3% and 5%. More restrictive

disturbance constraints reduce short-term timber supply by 1.5 to 3%. While these are not trivial harvest volumes,

they clearly play a smaller role in the timber supply dynamics of the TFL than do assumptions about minimum

harvest age.

Only two of the factors examined in sensitivity analysis runs had a significant impact on long-term harvest levels:

managed stand yield assumptions and early seral patch size management. West Fraser has a comprehensive

Change monitoring inventory in place to deal with the former issue, and periodically reviews patch size distribution

as part of their operational planning to address the latter issue. It should be noted that both of these matters also

impact short term harvest levels.

In light of the issues addressed in the sensitivity analyses mentioned above – and recognizing the uncertainties

associated with managed stand yields and patch size distribution modeling in particular – the base case

presented in this document is a good foundation upon which to base and AAC decision. A harvest level of

570,000 m3/year is the recommended AAC for TFL 52 for the term of MP#5.


Kelowna | Penticton | Prince George | Vancouver | Victoria | Chilliwack | Fort St. John i

Table of Contents

1. Introduction ................................................................................................ 1

1.1 Description of TFL 52 .......................................................................................................................1

1.2 Land Base Classification ..................................................................................................................3

1.3 Land Base Statistics .........................................................................................................................4

2. Timber Supply Analysis Methods ............................................................... 6

2.1 Model Description .............................................................................................................................6

2.2 Timber Supply Modelling ..................................................................................................................6

3. Base Case Analysis ................................................................................... 6

4. Sensitivity Analyses .................................................................................. 13

4.1 Stand Yield Variation ..................................................................................................................... 14

4.2 Natural Stand Yield ........................................................................................................................ 14

4.3 Managed Stand Yield .................................................................................................................... 15

4.4 Minimum Harvest Age ................................................................................................................... 16

4.5 Regeneration Delay ....................................................................................................................... 17

4.6 Patch Size Targets ........................................................................................................................ 17

4.7 Watershed Disturbance Limits....................................................................................................... 18

4.8 Visual Quality Objectives ............................................................................................................... 19

5. Summary and Recommendations ............................................................ 20

List of Tables in Text

Table 1.1 Land Base Netdown .............................................................................................................................................. 4

Table 3.1 Early Seral Patch Size Target Ranges (%).......................................................................................................... 12

Table 4.1 Sensitivity Analyses ............................................................................................................................................. 14

Table 4.2 Visual Disturbance Limits (%) by VQO and VAC ................................................................................................. 19

List of Figures in Text

Figure 1.1 Tree Farm Licence 52 Location ............................................................................................................................. 3

Figure 1.2 TFL 52 Age Class Distribution ............................................................................................................................... 4

Figure 1.3 TFL 52 Leading Species Distribution ..................................................................................................................... 5

Figure 1.4 TFL 52 Site Index Distribution ............................................................................................................................... 5


Kelowna | Penticton | Prince George | Vancouver | Victoria | Chilliwack | Fort St. John ii

Figure 3.1 Base Case Harvest Forecast ................................................................................................................................. 8

Figure 3.2 Base Case – Growing Stock Trend – Total and Operable ..................................................................................... 8

Figure 3.3 Base Case – Area Harvested ................................................................................................................................ 9

Figure 3.4 Base Case – Average Harvest Age ....................................................................................................................... 9

Figure 3.5 Base Case – Harvest Age Class Distribution ..................................................................................................... 10

Figure 3.6 Base Case – Average Harvest Volume per Hectare ........................................................................................... 11

Figure 3.7 Base Case – Harvest Volume by Leading Species ............................................................................................. 11

Figure 3.8 Base Case – Age Class Distribution of the THLB ................................................................................................ 12

Figure 3.9 Base Case – Early Seral Patch Size Distribution ................................................................................................ 13

Figure 4.1 Harvest Level Sensitivity to Natural Stand Yield Assumptions ............................................................................ 15

Figure 4.2 Harvest Level Sensitivity to Managed Stand Yield Assumptions ......................................................................... 16

Figure 4.3 Harvest Level Sensitivity to Minimum Harvest Age Assumptions ........................................................................ 16

Figure 4.4 Harvest Level Sensitivity to Regeneration Delay Assumptions ........................................................................... 17

Figure 4.5 Harvest Level Impact of Early Seral Patch Targets ............................................................................................. 18

Figure 4.6 Harvest Level Sensitivity Watershed Disturbance Limits ..................................................................................... 19

Figure 4.7 Harvest Level Sensitivity to Varying Visual Quality Objectives ............................................................................ 20


Kelowna | Penticton | Prince George | Vancouver | Victoria | Chilliwack | Fort St. John iii

Acronyms and Abbreviations

AAC Allowable Annual Cut

BC British Columbia

BEC Biogeoclimatic Ecosystem Classification

BEO Biodiversity Emphasis Option

BGC Biogeoclimatic

CFLB Crown Forested Land base

CMAI Culmination Mean Annual Increment

CMI Change Monitoring Inventory

DBH Diameter at Breast Height

ECA Equivalent Clear-Cut Area

EVC Existing Visual Condition

FAIB Forest Analysis and Inventory Branch

FPS Forest Planning Studio

FRPA Forest Range Practices Act

FSC Forest Stewardship Council

FTEN Forest Tenure Cutblocks

LTHL Long-Term Harvest Level

MFLNRO Ministry of Forests, Lands and Natural Resource Operations

MHA Minimum Harvest Age

MP Management Plan

MPB Mountain Pine Beetle

MSYT Managed Stand Yield Tables

NDT Natural Disturbance Type

NRL Non-Recoverable Losses

NSYT Natural Stand Yield Tables

OAF Operational Adjustment Factor

OGMA Old Growth Management Area

PFT Problem Forest Type

PFLB Productive Forest Land base

SIBEC Site Index by BEC


Kelowna | Penticton | Prince George | Vancouver | Victoria | Chilliwack | Fort St. John iv

SFMP Sustainable Forest Management Plan

TEM Terrestrial Ecosystem Mapping

TFL Tree Farm License

THLB Timber Harvesting Land base

TIPSY Table Interpolation Program for Stand Yields

TSA Timber Supply Area

TSR Timber Supply Review

VDYP Variable Density Yield Prediction Growth and Yield Model

VPH Volume per hectare

VLI Visual Landscape Inventory

VQO Visual Quality Objectives

VRI Vegetation Resources Inventory


1

1. Introduction

West Fraser must complete a timber supply analysis for TFL 52 in conjunction with the Management Planning

process that is required by legislation and the terms of the licence. Section 35.2 of the Forest Act enabled the

Tree Farm Licence Management Plan Regulation (last updated November 27, 2009) which describes the

approval process, term, timing, content requirements and public review process for a Tree Farm Licence (TFL)

Management Plan (MP). The following sections present the required content for West Fraser’s TFL 52 MP#5 as

required by the Regulation.

The last timber supply analysis in support of Management Plan #4 (MP #4) for TFL 52 was completed in 2007,

followed by the AAC determination that became effective April 1st, 2009 setting the uplift AAC to 1,000,000

m3/year.

West Fraser has engaged Ecora Engineering & Resource Group Ltd. (Ecora) to assist in the preparation of

information to support a new AAC determination for TFL 52. This analysis report should be viewed in conjunction

with the recently completed Tree Farm Licence 52 Management Plan # 5 Timber Supply Analysis Information

Package (dated March 2018) which describes the input data and assumptions used in this analysis. This

Information Package was advertised for public review and submitted to the Ministry of Forests, Lands and Natural

Resource Operations (MFLNRO). It was accepted by MFLNRO in March 15, 2018, for use in this timber supply

analysis.

When approved by the Province’s Chief Forester, the Management Plan, along with other pertinent information

and input, will be used in the Chief Forester’s determination of the allowable annual cut (AAC) from Tree Farm

Licence (TFL) 52. The AAC determination will be appended to this document once it is completed.

The next step in the timber supply analysis process is the preparation of a base case timber supply forecast.

Timber supply is the quantity of timber available for harvest over time. It is dynamic, not only because trees

naturally grow and die, but also because conditions that affect tree growth, and the social and economic

environment that affect the availability of timber for harvest, change with time. Timber supply analysis is the

process of assessing and predicting the current and future supply from a management unit. This has been done

using Patchworks, a forest estate model that facilitates the preparation of data, application of management

practices and other rules, and produces outputs describing the harvest flow and the future condition of the land

base, timber profile, and other resource values. The results are presented in this document (the Analysis Report),

along with the results of many sensitivity analysis runs that examine the timber supply impacts of changes in

management assumptions and model input.

This Analysis Report will be circulated for public review in conjunction with a draft of Management Plan (MP) #5

for the TFL. The MP will include a history of the TFL and a summary of the feedback received; the final versions

of the Information Package and Analysis Report will be included as Appendices.

Once this second public review process is complete, these documents will be submitted to the Chief Forester to

assist in making an AAC determination for the TFL. This information will be used by the Chief Forester of British

Columbia in determining a permissible harvest level for TFL 52. Upon completion of that review, the AAC

Rationale document will be appended to the finalized version of Management Plan #5.

1.1 Description of TFL 52

TFL 52 is composed of two blocks. Block A is located to the east of Quesnel. Once a contiguous parcel, it has

been split into two separate parcels as a result of Instrument 6 deleting 31,752 hectares from the TFL for the

Cascadia TSA. Block B is northwest of the city. Figure 1.1 shows the general location.


2

West Fraser was granted Block A of the TFL 52 licence in January 1991. Rolling plateaus typify the land base in

the west and the Cariboo Mountains in the east. Many lakes and rivers are found within the Licence area. Block

A contains the headwaters of the Cottonwood, Bowron and Willow Rivers, which all flow directly into the Fraser

River. Highway 26 between Quesnel and Bowron Lake Provincial Park provides primary access to Block A. This

highway bisects the License into north and south components. Most forest roads into Block A originate from

Highway 26 which provides excellent year-round access for both forest management and recreational activities.

Block B of TFL 52 is located northwest of Quesnel along the Fraser River. Similar to Block A the land base is

typified by rolling plateaus but includes steep banks leading down to the Fraser River. Western Plywood Ltd.

(which later became Weldwood of Canada) was granted the former TFL 5 licence in May 1950. Primary access

to Block B is provided by Highway 97 between Quesnel and Hixon for the eastern component. The western side

of Block B can be accessed by either Blackwater Road or Tako Road. Due to the long history of forestry activities

on Block B (more than 60 years), there is excellent year-round access for both forest management and

recreational activities.

The forests of TFL 52 are dominated by interior spruce, lodgepole pine, and Douglas-fir. Other species include

subalpine fir, trembling aspen, and cottonwood. Birch, western hemlock, and western redcedar are found in

localized areas. Two biogeoclimatic ecological classification (BEC) zones dominate the land base of TFL 52:

Sub-boreal spruce (SBS), generally below 1200 metres with cool, snowy winters and warm summers;

and

Engelmann spruce-subalpine fir (ESSF), generally above 1200 metres with long, cold winters and short,

cool summers.

The interior cedar-hemlock (ICH) BEC zone is found in a tiny area near the eastern boundary of the TFL.

Several communities are associated with TFL 52. These include Quesnel, Wells, Barkerville, Bowron Lake, and

Cottonwood. Both Wells and Barkerville are located within the License area. Two popular recreational areas,

Bowron Lake Provincial Park and Troll Mountain Ski Resort, share a common boundary with TFL 52.


3

Figure 1.1 Tree Farm Licence 52 Location

1.2 Land Base Classification

Table 1.1 presents the results of the land base classification process to identify the productive forest land base

(PFLB) timber harvesting land base (THLB). The PFLB excludes non-forested areas and road area from the total

TFL area. The THLB further excludes areas that are not suitable for timber production and areas with legally

defined boundaries that are reserved for the management of other resource values.


4

Individual areas may have several classification attributes. For example, stands within riparian reserve

boundaries might also be classified as non-commercial. These areas would have been classified by this latter

attribute, before the riparian classification. Therefore, in most cases, the actual net reduction is smaller than the

total area found in the classification. The order of the entries in Table 1.1 corresponds to the sequence in which

the land base classifications were applied.

Table 1.1 Land Base Netdown

Land Base Classification Total Area (ha) Productive Area (ha)

Area Removed (ha)

Volume Removed (m3)

Total Land Base 261,468

Non-Forest 16,315 - 16,315 227,049 Roads 2,977 - 2,465 132,879 Productive Land Base 242,688 242,688 38,106,868

Non-Productive 18,497 1,539 1,539 888 Terrain 6,824 5,757 5,241 1,000,252 Inoperable 3,775 3,539 1,672 381,071 Operable Land Base 234,236 36,724,657

Riparian Reserve Zone 10,304 6,388 5,883 1,330,912 Riparian Management Zone 15,277 10,874 4,364 829,727 Critical Fish Habitat 5,507 3,973 2,539 558,156 Caribou Habitat 23,417 20,953 18,175 3,195,008 VQO Preservation 338 336 325 87,899 Recreation Features 1,215 1,033 459 83,706 OGMA 24,892 24,321 19,815 5,313,643 WTP 4,535 4,306 3,046 883,216 Low Productivity 20,817 13,218 4,507 611,451 Deciduous 985 749 239 34,328 Timber Harvesting Land Base 174,884 23,796,611

1.3 Land Base Statistics

Figure 1.2 summarizes the productive and THLB area of the TFL by 10-year age class.

Figure 1.2 TFL 52 Age Class Distribution


5

Figure 1.3 shows that spruce and pine are the most common leading species on the TFL.

Figure 1.3 TFL 52 Leading Species Distribution

Most of the timber harvesting land base has an inventory site index of between 10 metres and 25 metres as shown in Figure

1.4

Figure 1.4 TFL 52 Site Index Distribution


6

2. Timber Supply Analysis Methods

2.1 Model Description

Patchworks is a spatially explicit harvest scheduling optimization model developed by Spatial Planning Systems in

Ontario. It has been used to develop spatially explicit harvest allocations to explore the trade-off between a broad

range of different management and harvest goals. Patchworks is a multiple-objective goal-programming model

that consists of two primary components:

1. A GIS interface with map viewer and viewer functions; and

2. A harvest scheduler that runs continuously in the background - searching for improvements in the

allocation to improve the value of the objective function. The model seeks a solution that maximizes the

value of the total objective function. The objective function is made up of both the traditional

(management plan) objectives and the additional requirements and indicators. In areas of timber

management, the harvest schedule is optimized (both the current and future forecasted land base) for

timber flow requirements and to minimize the environmental risk, as measured by the established

indicators.

2.2 Timber Supply Modelling

Timber supply analysis for the full two hundred and fifty (250) year planning horizon was carried out to ensure that

short and medium term harvest targets do not compromise long-term growing stock stability. This was modeled in

fifty five-year periods. Modeled harvest levels included allowances for non-recoverable losses (NRLs). Harvest

figures reported here include this amount (2470 m3/year).

3. Base Case Analysis

The base case timber supply scenario has been run for TFL 52 using the Patchworks forest estate model. The

criteria laid out in the accepted Information Package have been met.

The base case reflects current management performance. The analysis incorporates the following:

Vegetation resource inventory (VRI) adjusted through a Phase 2 process and was updated with harvest

blocks and other disturbances that have occurred since the original inventory mapping was completed;

Recognition that a many remaining MPB-impacted pine stands have become unmerchantable and will

break up and regenerate naturally;

Site productivity estimates based on terrestrial ecosystem mapping

Ecosystem-based analysis units and silvicultural prescriptions; and

Application of current genetic gains to managed stand yields;

Adjusted yield estimates for previously fertilized stands (but no assumed future fertilization);

Maintenance of landscape-level biodiversity through the designation of OGMA’s;


7

Application of ‘mature-plus-old’ seral requirements in addition to designated OGMA’s;

Protection of deer, caribou and moose habitat as required by higher-level plans and committed to in the

FSP;

Rate-of-harvest-limitations in visually sensitive areas to until visually effective green-up has been

achieved;

Restrictions on the rate of disturbance for watersheds on the TFL; and

Early seral patch size modeling for the entire planning horizon.

The highest initial harvest level that could be sustained was 570,000 m3/year. Many preliminary iterations of the

base case scenario established that the natural harvest flow was naturally steady for the first twenty years. For

the final base case run presented here, a flow constraint requiring that the harvest level over the first four 5-year

periods not vary by more than 0.1% from one another was applied.

The only other constraint applied to the base case harvest flow was to the final 100 years of the planning horizon.

Similarly, the harvest level in each of the last twenty 5-year periods was not allowed to vary by more than 0.1%.

Between period 4 and period 30, the harvest level was allowed to float (subject to targets and weights on non-

timber objectives). Equal weights were assigned to harvesting in each five-year period (i.e., no preference or bias

towards harvesting sooner rather than later. The model attempts to maximize the volume harvested over the

entire planning horizon.

However, two (relatively small) factors would encourage earlier harvesting:

1) Deteriorating pine stands would be scheduled for harvest before more volume was lost. That is a small

issue for TFL 52 since those few remaining MPB-impacted stands that are merchantable have been

identified in West Fraser’s operations plans and scheduled in the forest estate model accordingly.

2) Since managed stands grow more quickly than natural stands, the best strategy for maximizing total

harvest volume is to convert older natural stands to better-performing managed stands as quickly as

possible. Through millions of iterations, the forest estate model reaches this conclusion without specific

harvesting priorities (i.e. ‘oldest-first’ or ‘minimize-growth-loss’) having been provided as input.

After twenty years the harvest level jumps to 660,000 m3/year and then climbs slowly for the next 130 years to the

long-term sustainable level of 784,500 m3/year. (All of these annual harvest volumes are net of 2470 m

3/year of

non-recoverable losses.) Figure 3.1 shows this harvest flow pattern.


8

Figure 3.1 Base Case Harvest Forecast

The proposed harvest levels lead to the growing stock pattern shown in Figure 3.2. Total growing stock increases

steadily over the first 100 years from 23.0 million cubic metres to 30.6 million cubic metres. A flow constraint was

applied to the final 100 years of the planning horizon to ensure that growing stock levels stabilized. The average

growing stock volume over this period is 32 million cubic metres.

Operable growing stock declines initially from 15.7 million cubic metres in period 1 to 12.8 million cubic metres in

period 3. It climbs to 20.2 million cubic metres in period 9 and then falls again to 17.1 million cubic metres in

period 14. After that, it climbs steadily, reaching 22 million cubic metres by the end of the planning horizon.

Figure 3.2 Base Case – Growing Stock Trend – Total and Operable


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In spite of the constant harvest level, average annual harvest area varies noticeably over the first four five-year

periods. It is highest in period one (1996 hectares/year) and lowest in period three (1731 hectares/year). It climbs

sharply in period five to 2127 hectares/year. After that, period-to-period variations are much more muted. The

long-term average (after 80 years) is 2110 hectares/year.

Figure 3.3 Base Case – Area Harvested

Average harvest age is high initially - 171 years in the first five-year period. It falls steadily to 75 years in the sixth

five-year period and is stable at the level for about the next fifty years. From the eighth decade until the end of

the planning horizon the average stand age at harvest is 69 years. Figure 3.3 shows this pattern.

Figure 3.4 Base Case – Average Harvest Age


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The age class distribution of the harvest is further broken down in Figure 3.5. Most of the older timber (> 120

years of age) currently on the TFL is harvested over the next twenty years. Starting in the third decade, most of

the harvest is composed of stands between 40 and 80 years of age. Some older stands are retained on the THLB

for the long term to meet other resource constraints. These are harvest slowly as regenerating stands are

recruited to meet these non-timber objectives.

Figure 3.5 Base Case – Harvest Age Class Distribution

Harvest volume per hectare (VPH) averages 355 m3/hectare over the entire planning horizon. It is lower initially

(286 m3/hectare in the first five-year period) as lower-productivity naturals stands are converted to managed

stands, and as MPB salvage blocks are cleaned up. It falls again briefly after 20 years as harvesting transitions

into younger second-growth stands. Harvest volume averages 315 m3/hectare over the first fifty years of the

planning horizon, before climbing to the steady long-term (i.e., beyond 150 years) average of 372 m3/hectare, as

shown in Figure 3.6.


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Figure 3.6 Base Case – Average Harvest Volume per Hectare

Figure 3.7 shows the base case harvest volume broken down by leading species. There is little pine available in

the short term as a result of the MPB epidemic. By the third decade, pine stands begin to form a more significant

part of the harvest. By the end of the planning horizon, 57% of the harvest comes from spruce-leading stands,

and 24% comes from pine-leading stands.

Figure 3.7 Base Case – Harvest Volume by Leading Species

Figure 3.8 shows how the age class distribution on the THLB changes over the planning horizon. There is a slight

excess of older age classes (older than 120 years), and this is somewhat reduced over the course of the planning

horizon. Many of these older stands are retained to meet visual quality objective and habitat values. By the end of

the planning horizon, 80% of the THLB consists of stands younger than 80 years of age.


12

Figure 3.8 Base Case – Age Class Distribution of the THLB

Harvest planning on TFL 52 attempts to achieve a specified early seral patch size distribution by landscape unit

and natural disturbance type. (Early seral is defined as stands younger than 20 years.) The base case has been

set up to meet those same objectives over the long term. The base case results show that, for the most part,

those patch size targets are being achieved in the long term.

Early versions of the base case applied equal weights to achieving the target patch size distribution to each

period in the planning horizon. This approach significantly reduced short-term harvest levels. After reviewing

these initial runs with Ministry staff, a negative discount rate was applied to patch size target weights so that the

required distribution would be achieved in the medium and long term without unduly limiting harvesting in the

short term.

Table 3.1 shows the patch size targets that were implemented for the base case. The objectives (minimum and

maximum percentages of area in each patch-size category) are the same for both NDT 1 and 2; NDT3 targets

vary slightly. For the two smaller categories, the limits are between 30% and 40% of the early-seral area for

NDT1/2 and between 20% and 30% for NDT3. The objective for the 80-250 hectare size class is a bit wider (20%

to 40% for NDT1/2 and 30% to 50% for NDT3). No early seral area should occur in patches larger than 250

hectares in size.

Table 3.1 Early Seral Patch Size Target Ranges (%)

NDT 0-40 ha 40-80 ha 80-250 ha > 250 ha

1 30-40 30-40 20-40 0 2 30-40 30-40 20-40 0 3 20-30 25-40 30-50 0

Figure 3.9 shows that – for the TFL taken as a whole – patch size targets are met by the end of the planning

horizon.


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Figure 3.9 Base Case – Early Seral Patch Size Distribution

4. Sensitivity Analyses

Sensitivity analysis provides a measure of the upper and lower bounds of the base case harvest forecast that

reflects the uncertainty in the data and the management assumptions made in the base case. It can provide

information on the degree to which uncertainty in the base case data and assumptions might affect the proposed

harvest level for the TFL. The magnitude of the increase and decrease in harvest level (and other forest attributes

and measures) in response to changes in the sensitivity variable being examined reflects the degree of

uncertainty surrounding that variable (or assumption) associated with that specific variable. The magnitude of the

change reflects the degree of risk associated with a particular uncertainty – a very uncertain variable that has

minimal impact on the harvest forecast represents a low risk. By developing and testing many sensitivity issues, it


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is possible to determine which variables most affect results and to provide information to guide management

decisions in light of inherent uncertainty.

Each sensitivity listed in Table 4.1 was modeled in a separate scenario to test the impact of changing a variable

from the base case. All of the harvest levels reported in this section have been reduced by 2,470 m3 to account

for non-recoverable losses. The table summarizes the short- and long-term harvest level found in each case, and

compares them to the base case scenario.

Table 4.1 Sensitivity Analyses

Sensitivity

Harvest Volume

(m³/yr)

Change from the Base

Case

Short

Term

Long

Term

Short

Term

Long

Term

Base Case 569,922 784,550 100.0% 100.0%

natural yield plus 10% 640,863 796,427 112.4% 101.5%

natural yield minus 10 % 525,106 792,291 92.1% 101.0%

managed yield plus 10% 590,980 869,245 103.7% 110.8%

managed yield minus 10 % 560,126 703,444 98.3% 89.7%

minimum harvest age plus 10% 430,483 757,910 75.5% 96.6%

minimum harvest age minus 10% 585,335 794,643 102.7% 101.3%



no early seral patch targets 654,982 811,120 114.9% 103.4%

no watershed HEDA limits 587,539 794,824 103.1% 101.3%

HEDA plus 10% 585,646 794,041 102.8% 101.2%

HEDA minus 10% 561,648 776,894 98.5% 99.0%

VQO increased one category 553,574 770,392 97.1% 98.2%

VQO decreased one category 597,621 803,128 104.9% 102.4%

4.1 Stand Yield Variation

Estimates of stand yield form the core of a timber supply analysis. Stand yield forecasts for this analysis were

developed using VDPY and TIPSY. These yields, for existing and future stands, are subject to uncertainties that

arise from inventory inputs, changing silvicultural practices, uncertain site productivity and the limitations of the

individual models. Two sets of sensitivity analyses were run to present the potential impacts on timber supply of

the uncertainty attached to estimates of individual stand yield. These are 1) Natural stand yields +/- 10%; and 2)

Managed stand yields +/- 10%;

4.2 Natural Stand Yield

Yield forecasts for natural stands were developed using VDYP7. If these yield estimates are increased and

decreased by 10%, the harvest level changes as shown in Figure 4.1. As would be expected, the impact is

highest in the short term because harvesting occurs primarily in natural stands. Reducing yields by 10% results in

a 7.9% drop in short-term harvest levels, and a 10% yield increase leads to 12.4% harvest level increase.

Adjusting natural stand yield impacts the long-term harvest level only slightly (less than 2%). The increase in the

long-term harvest level with the decrease in natural stand yield curves is challenging to explain. It may be a


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consequence of converting natural to managed stands more quickly or to the interaction of minimum harvest age

and patch size requirements.

Figure 4.1 Harvest Level Sensitivity to Natural Stand Yield Assumptions

4.3 Managed Stand Yield

Managed stand yield estimates were compiled using BatchTIPSY Version 4.3. Changes in assumptions about

managed yields (for both existing and future managed stands) have an immediate impact on harvest levels. The

oldest managed stands on Block B are (approximately 65 years of age) and now becoming harvestable. The

harvest level impact is much more pronounced in the medium and long-term when the harvest flow is comprised

almost entirely of managed stands. The long-term harvest level rises (10.8%) and falls (10.3%) in proportion to

the 10% change in managed yields. Figure 4.2 shows these changes relative to the base case harvest flow.


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Figure 4.2 Harvest Level Sensitivity to Managed Stand Yield Assumptions

4.4 Minimum Harvest Age

Minimum harvest ages were varied (plus / minus ten percent) to gauge the impact on timber supply. Decreasing

MHA does not affect harvest levels significantly. However, increasing MHA by 10 years leads to a significant and

immediate harvest shortfall of 24.6%. As a result of the mountain pine beetle epidemic, growing stock levels are

reduced, and short-term timber availability is tight. Waiting an additional 5 to 15 years before harvesting

regenerating stands means that the existing mature volume must be logged at a reduced rate. The long-term

harvest level is also reduced – but only by 3.4%. Figure 4.3 shows this pattern.

Figure 4.3 Harvest Level Sensitivity to Minimum Harvest Age Assumptions


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4.5 Regeneration Delay

The base case assumed a regeneration delay of two years for all stands. (This was not built into the managed

stand yield tables but rather was applied in the forest estate model.) Eliminating the delay means that existing

mature stands can be harvested a bit more quickly, leading to a 3.2% increase in the short-term harvest. The

long-term impact is a smaller increase of only 1.1%.

The decrease in short-term harvest levels when the regeneration delay is increased to four years is smaller than

expected in light of the MHA results in the previous section. It falls by only 1.7 percent. The long-term drop is

more significant at 4.5%. Figure 4.4 shows these trends.

Figure 4.4 Harvest Level Sensitivity to Regeneration Delay Assumptions

4.6 Patch Size Targets

Harvest planning on TFL 52 is directed to achieving a target patch size distribution. This is accomplished by

tracking and managing the distribution of early seral patches by landscape unit and natural disturbance type.

Progress towards these targets is checked operationally every year or two. The base case results show that, for

the most part, those patch size targets are being achieved in the long term.

However, timber supply planning for most other forest tenures uses an integrated resource management

constraint to distribute harvesting spatially for strategic planning purposes. For this sensitivity run, patch size

targets have been dropped and replaced with an IRM constraint. This constraint was applied by landscape unit

and BGC subzone – and only to areas of the THLB not covered by visual quality objectives. As Figure 4.5 shows,

this change increases timber supply in both the short term (by 14.9%) and the long-term (by 3.4%)


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Figure 4.5 Harvest Level Impact of Early Seral Patch Targets

4.7 Watershed Disturbance Limits

West Fraser monitors watershed condition using ‘hydrologically equivalent disturbed area’ or HEDA. Target

conditions are established for each watershed based on its underlying dynamics. These targets are listed in

Table 8.4 for of the Information Package. Three sensitivity runs were completed:

1. HEDA targets were removed;

2. The HEDA limit was increased by 10% (i.e., if the base case limit was 34%, it was increased to 44%); and

3. The HEDA limit was decreased by 10%

Decreasing the allowable limit reduced timber supply only slightly in either the short- (1.5%) or long-term (1.0%).

Increasing or removing the limit had a slightly higher impact. The short-term harvest increased by about 3% and

the long-term harvest by just over 1%. Figure 4.6 shows this pattern.


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Figure 4.6 Harvest Level Sensitivity Watershed Disturbance Limits

4.8 Visual Quality Objectives Visual quality objectives are based on operational guidelines for maintaining viewscapes. Operational standards focus on

cutblock design, harvesting methods, and public perception. Acceptable levels of disturbance are established by VQO (visual

quality objective) and VAC (visual absorption capability). Table 4.2 shows the limits that were used for the base case.

Table 4.2 Visual Disturbance Limits (%) by VQO and VAC

VQO VAC=Low VAC=Medium VAC=High

Retention 1.1 3 5 Partial Retention 5.1 10 15 Modification 15.1 20 25

For these two sensitivity runs, each distinct visual polygon was assigned first to the next highest (i.e., more restrictive)

category and then to the next lowest category. This VAC for the polygon was assumed to remain constant. In the first case,

‘Retention’ polygons that move to ‘Preservation’ became unharvestable. In the second case, ‘Modification’ polygons had no

restrictions applied.

The harvest level impact of relaxing VQO restrictions was higher than the impact of increasing them, as shown in Figure 4.7.

Harvest level increases by 4.9% and 2.4% in the short- and long-term respectively when VQO restrictions were reduced. The

corresponding reductions in timber supply when the restrictions were tightened were 2.9% and 1.8% (in the short- and long-

term)

.


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Figure 4.7 Harvest Level Sensitivity to Varying Visual Quality Objectives

5. Summary and Recommendations

The base case presented shows that a harvest level of 570,000 m3/year is possible for the next twenty years. This

is a net harvest level after the allowance for non-recoverable losses has been taken into account. A review of the

THLB growing stock trend and future age class distribution of the THLB shows that the initial harvest level is

justified.

The growing stock at the end of planning horizon (32 million cubic metres total, with 22 million cubic metres above

minimum harvest age) is sufficient to support continued operations at the sustainable long-term harvest level of

784,550 m3/year. In fact, a small increase in the harvest level would probably be possible at the end of the

planning horizon.

Summary statistics of the harvest profile were compiled and presented. Average harvest age falls sharply over

the next thirty years as existing mature and over-mature growing stock is harvested. The long-term average

harvest age is 69 years. However, a small but significant proportion of the harvest (approximately 10%) continues

to come from stands older than 100 years until the end of the planning horizon. These stands are being retained

to satisfy disturbance restrictions (i.e., visual quality objectives, water rate-of-cut) or ‘mature-plus-old’ seral

requirement. Harvesting is also delayed in some of these stands because they can’t be harvested due to the

opening size restrictions that were modeled (no openings less than five hectares), or because they must be

carried until surrounding stands mature to comply with early seral patch size distribution targets.

The average harvest volume in the first 5-year period is 286 m3/hectare is low, but this is a modeling artifact that

that can easily be managed on the ground. The average forecast harvest volume of 315 m3/hectare over the next

fifty years is not unrealistic in relative to current operational harvest volumes.

The harvest pattern found in this analysis is not surprising. The timber supply analysis for the previous

management plan indicated that more recoverable pine might remain today – but that it would be running out. It

has, in fact, run out. TFL 52 is now in the timber supply trough predicted by MP#4. The trough is only slightly


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deeper than expected, due in large part to the land base reduction related to the creation of the Cascadia TSA

and (perhaps) because MP#4 was slightly optimistic about the proportion of dead pine that would be recoverable.

The sensitivity analysis around minimum harvest age emphasizes the precarious nature of the current timber

supply situation. Lowering MHA by 10% provides only a modest increase in short-term timber supply – but

increase MHA by 10% cuts short-term (i.e., the next 20 years) by almost 25%. The immediate harvest level is

very closely tied to assumptions about when the oldest existing managed stands will first become merchantable.

The current harvest level is also sensitive to disturbance constraints that protect visual quality and watersheds. If

these are relaxed, short-term harvest levels can rise slightly – by between 3% and 5%. More restrictive

disturbance constraints reduce short-term timber supply by 1.5 to 3%. While these are not trivial harvest volumes,

they clearly play a smaller role in the timber supply dynamics of the TFL than do assumptions about minimum

harvest age.

Only two of the factors examined in sensitivity analysis runs had a significant impact on long-term harvest levels:

1. Managed stand yield assumptions (and related regen delay and MHA questions); and

2. Early seral patch size targets.

Fortunately, West Fraser has an active and comprehensive Change Monitoring Inventory (CMI) in place and can

check to see if managed stands are under- or out-performing the yield curves used for this analysis.

Uncertainty about the early seral patch size targets will be more challenging to resolve. The sensitivity run that

replaced these targets with a more traditional integrated resource management (IRM) constraint lead to harvest

level increases of 14.9% and 3.4% in the short- and long-term respectively. It is tempting to try to make a case for

the IRM modeling approach, but the fact is that working towards the mandated patch size target is an operational

reality for West Fraser’s planners. Different technical approaches to modeling future patch size distribution – such

as adjacency thresholds, tolerance for inclusion of older seral remnants and buffers within patches, and the

definition of ‘early seral’ itself – might provide some short-term harvest relief. However, it might also make the

situation worse. A full examination of this complicated issue is beyond the scope of a timber supply analysis. In

the absence of such an analysis, the early seral patch modeling completed for this analysis is reasonable – and is

an improvement on the older IRM approach.

In light of the issues addressed in the sensitivity analyses mentioned above – and recognizing the uncertainties

associated with managed stand yields and patch size distribution modeling in particular – the base case

presented in this document is a good foundation upon which to base and AAC decision. A harvest level of

570,000 m3/year is the recommended AAC for TFL 52 for the term of MP#5.


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