rehabilitation of degraded lands in misiones, argentina

B O I S E T F O R Ê T S D E S T R O P I Q U E S , 2 0 0 6 , N ° 2 8 8 ( 2 ) 51RÉHABILITATION DE SOLS / LE POINT SUR…

Florencia Montagnini1

Beatriz Eibl2

Roberto Fernández3

1 Yale University School of Forestryand Environmental Studies370 Prospect StreetNew Haven, CT 06511USA

2 Facultad de Ciencias ForestalesUniversidad Nacional de Misiones(3382) Eldorado, MisionesArgentina

3 INTA EEA Monte Carlo(3384) Monte Carlo, MisionesArgentina

Rehabilitation of degradedlands in Misiones,

Argentina

This article reports onthe status of plantation forestryin Misiones (North-EastArgentina) and describes resultsfrom recent experiences on landrestoration projects usingindigenous tree species. Thefindings of this research arealready being used in communityforestry projects in the region,which include open mixed andsingle-species plantations andenrichment planting in degradedsecondary forests.

Balfourodendron riedelianum (Rutaceae, “guatambú blanco”), 13 year-old, grew best on site 3, the most fertile, in a private property near the town of Santiago de Liniers, in comparison withgrowth in the most degraded site. The growth of this species was better at this site than in othertrials in the region where B. riedelianum has been tested in enrichment plantings.Photo F. Montagnini.

RÉSUMÉ

RÉHABILITATION DE SOLS DÉGRADÉSÀ MISIONES, ARGENTINE

Misiones, province d’Argentine, couvremoins de 1 % de la superficie du paysmais abrite 40 % de sa biodiversité etproduit 70 % de son bois. Suite audéfrichage des forêts, de nouvelles uti-lisations des terres s’imposaient. Nousprésentons les résultats de projets deréhabilitation des terres intégrant desessences indigènes. Des essais (1990-1991) ont permis de tester Ilex para-guariensis en plantations mixtes et enagroforesterie. La meilleure croissancesur sol pauvre était obtenue avecEnterolobium contortisiliquum et Astro-nium balansae. Les résultats pourBalfourodendron riedelianum, très pri-sée dans la région, étaient excellentsen sol fertile, sous réserve d’une bonnegestion. L’association de ces essencesavec I. paraguariensis semble appro-priée, puisque les récoltes d’I. para-guariensis permettent une rentabilisa-tion rapide des investissements. Desessais d’enrichissement (1988-1990)dans des zones forestières surexploi-tées ont donné, sept ans après la plan-tation, les meilleurs résultats avecBastardiopsis densiflora, E. contortisili-quum, Nectandra lanceolata, Ocoteapuberula et Peltophorum dubium.Dans la réserve Guaraní, les meilleuresessences au bout de treize ans étaientO. puberula, B. densiflora et Cordia tri-chotoma. Ces essences ont égalementdes effets bénéfiques pour le sol, etpeuvent améliorer les forêts dégra-dées. L’intégration d’essences à rota-tion plus courte (palmier Euterpe edu-lis) accélère la rentabilisation. Cesrésultats sont utilisés pour encouragerla plantation d’arbres dans le cadre deprojets de sylviculture communautaire.Les chercheurs fournissent conseils etassistance ainsi que des plants et unsuivi de la plantation et de l’entretien.Les premiers résultats sont promet-teurs et d’autres municipalités rejoi-gnent les projets.

Mots-clés : sol dégradé, plantationd’enrichissement, essence autoch-tone, plantation, bois, Ilex paragua-riensis, Misiones, Argentine.

ABSTRACT

REHABILITATION OF DEGRADEDLANDS IN MISIONES, ARGENTINA

Misiones Province, in Argentina, cov-ers less than 1% of the total area ofthe country but harbors almost 40%of its biodiversity and produces over70% of its timber. Forest clearing hascaused substantial changes, andalternative land uses have becomenecessary due to soil degradationand land abandonment. This articlepresents the results of land rehabili-tation projects using indigenous treespecies. In 1990-1991, trials beganto test mixed plantations and agro-forestry with Ilex paraguariensis.Enterolobium contortisiliquum andAstronium balansae showed the bestgrowth on poor soils. Balfouroden-dron riedelianum, a valued tree inthis region, had excellent perform-ance on fertile soils and with ade-quate management. The associationof trees with I. paraguariensisappeared appropriate, since I. para-guariensis harvests bring short-termreturns on investments. Enrichmenttrials were established in 1988-1990in overexploited forests. Seven yearsafter planting, the best species wereBastardiopsis densiflora, E. contor-tisiliquum, Nectandra lanceolata,Ocotea puberula, and Peltophorumdubium. In the Guaraní Reserve, thebest species at thirteen years wereO. puberula, B. densiflora, and Cor-dia trichotoma. These species alsohave beneficial effects on soils, andcan thus improve the condition ofdegraded forests. Incorporatingspecies with a shorter harvest age(Euterpe edulis palm) can accelerateinvestment returns. These results arebeing used to promote tree plantingin community forestry projects.Researchers provide tree seedlings,help planting and advise on estab-lishment and caring. Initial resultsare promising, and other municipali-ties are joining the projects.

Keywords: degraded land, enrich-ment planting, native species, plan-tation, timber, Ilex paraguariensis,Misiones, Argentina.

RESUMEN

RESTAURACIÓN DE SUELOSDEGRADADOS EN MISIONES,ARGENTINA

La provincia de Misiones representamenos del 1% de la superficie deArgentina, pero alberga casi el 40% dela biodiversidad y produce más del70% de la madera. Misiones ha tenidocambios de uso de la tierra substancia-les debido al corte de bosques, y sonnecesarios usos alternativos debido ala degradación de suelos y al abandonode tierras. Se presentan resultados deproyectos de restauración de tierras uti-lizando especies arbóreas nativas. En1990-1991 se ensayó una serie deplantaciones mixtas y sistemas agrofo-restales con Ilex paraguariensis. Entero-lobium contortisiliquum y Astroniumbalansae tuvieron el mejor crecimientoen suelos pobres. Balfourodendron rie-delianum, una especie valiosa en laregión, tuvo un comportamiento exce-lente en suelos fértiles y con manejoadecuado. La asociación de árbolescon I. paraguariensis fue aparente-mente apropiada, ya que las cosechasde I. paraguariensis representan unretorno de la inversión a corto plazo. En1988-1990 se establecieron experi-mentos de enriquecimiento de bos-ques sobreexplotados. A los siete años,las mejores especies fueron Bastar-diopsis densiflora, E. contortisiliquum,Nectandra lanceolata, Ocotea puberulay Peltophorum dubium. En la ReservaGuaraní, a los trece años las mejoresespecies fueron O. puberula, B. densi-flora, y Cordia trichotoma. Estas espe-cies también tienen efectos beneficio-sos sobre los suelos, mejorando lascondiciones de los bosques degrada-dos. La incorporación de especies concosecha más temprana (palma Euterpeedulis) puede acelerar el retorno de lainversión. Estos resultados se están uti-lizando para estimular la plantación deárboles en proyectos comunitarios. Losinvestigadores proveen los arbolitos,ayudan a mantener los árboles y aseso-ran sobre el establecimiento y cuidado.Los resultados iniciales son promiso-rios, y otras municipalidades se estánincorporando a estos proyectos.

Palabras clave: tierra degradada,enriquecimiento, especie nativa,plantación, madera, Ilex paragua-riensis, Misiones, Argentina.

52 B O I S E T F O R Ê T S D E S T R O P I Q U E S , 2 0 0 6 , N ° 2 8 8 ( 2 )

FOCUS / REHABILITATION OF LANDSFlorencia Montagnini, Beatriz Eibl,Roberto Fernández

Introduction

The Province of Misiones innorth-eastern Argentina (25-28°S, 53-56°W, elevation 100-800 m)(Figure 1) covers an area of approxi-mately 30 000 km2, less than 1% ofthe total area of the country. However,the Province of Misiones harborsalmost 40% of Argentina’s biodiver-sity and produces over 70% of its tim-ber (Gobierno de la Provincia DeMisiones, 2003). In recent years, theprovince of Misiones, which has tradi-tionally supplied timber products tothe rest of the country and for export,has been applying the “multiple use”approach to its forest resources, toinclude the use of non-timber forestproducts and to develop environmen-tal and recreational forest services.

However, alternatives for landuse are clearly necessary to supportcurrent economic and ecologicalneeds: inappropriate land uses andmanagement, such as the prolifera-tion of shifting agriculture or inade-quate soil techniques in plantationmanagement, have often led to soildegradation and subsequent aban-donment of lands in the region(Montagnini, Jordan, 2005).

In 1989, the Yale School ofForestry and Environmental Studies(FES) signed an agreement with theSchool of Forestry at the NationalUniversity of Misiones (UNaM) tocarry out collaborative studies inreforestation and agroforestry.Experimental single-species andmixed plantations, agroforestry sys-tems on degraded land and enrich-ment trials in degraded forests wereestablished using native trees of eco-nomic value (Fernández et al., 1997;Montagnini et al., 1998; Eibl et al.,2000). This article reports on the sta-tus of plantation forestry in Misionesand advances results of recent expe-riences on land restoration projectsusing indigenous tree species in theregion.

Misiones forests,past and present

The Köppen system (Köppen,1918) classifies the climate ofMisiones as Cfa, where C stands for amesothermic climate, f for lack of awell-defined dry season, and a forsubtropical. Annual precipitationranges from 1700 to 2400 mm.Means temperatures over a 17-yearperiod (1985-2002) are 25°C with amaximum of 39°C for the hottestmonth (January), and 14°C with aminimum of -6°C for the coldestmonth (July) .

The Paranaense forest, a typicalforest formation in Misiones, is oneof the most diverse ecosystems inboth Argentina and Paraguay. In its

mature form, the Misiones forest con-tains an average of about 100 treespecies per hectare. Species compo-sition varies with geographical loca-tion: for example, the presence ofAraucaria angustifolia (Bert.) O. Ktze.(“pino Paraná”) in association withtree ferns is restricted to higher ele-vations in the north-eastern part ofthe province, while Aspidospermapolyneuron Müll. Arg. (“palo rosa”) inassociation with the “palmito” palm(Euterpe edulis Mart.) only occurs inthe North. The complex forest struc-ture includes trees reaching heightsof up to 40 m, with no single speciesreaching “importance values” greaterthan 8%. Importance values are gen-erally calculated as the average ofthe relative abundance and relativefrequency of each species in forest


Figure 1. Map of South America showing the location of the Province of Misiones (in red)in north-eastern Argentina, on the border with Paraguay and Brazil.

Argen

tina

Misi

ones

inventories, where individuals ofeach species are counted in sampleplots. Importance values below 10-15% are typical of very diverseforests where no single species isdominant, leaving room for otherspecies (Odum, 1983). In theMisiones forests there is also a denseunderstorey of lianas, tree ferns,palms and bamboos, small shrubsand herbaceous plants.

In Misiones, about 200 local pro-ducers own forest lands subjectto Forest Management Plans, bringingthe total area of managed forest toalmost 500 000 hectares (Gobiernode la Provincia De Misiones, 2003).Timber extraction is subject to mini-mum diameter regulations (Monta-gnini et al., 1998 and 2001). Underthe Minimum Diameter cutting methodthat prevails in Argentina, commercialspecies may only be extracted if they

have a minimum stipulated diameterat breast height (dbh) of 40 to 55 cm,depending on the species.

Natural protected areas cover atotal of 481 000 hectares (almost16% of the provincial territory). The 53Protected Areas of different categoriesinclude national parks and reserves,17 provincial parks, 16 private parksand wildlife refuges, one biospherereserve, and one conservation andsustainable development area knownas the Green Biological Corridor(“Corredor Verde”). Protected areasare found throughout the province ofMisiones, although the largest tractsare in the North-East where the IguazúNational Park and the Corredor Verdeare located. In general, all ecosystemsin the Paranaense forest are being pre-served in these protected areas(Gobierno de la Provincia De Misio-nes, 2003).

The establishmentof industrialplantations

A forest inventory revealed thatthe total area of natural forests inMisiones amounted to 2 600 millionhectares in 1850, but as a result of log-ging and clearing to establish planta-tions and agriculture, only 1 222 mil-lion hectares remained by 1977(Gobierno de la Provincia De Misio-nes, 2003). This was largely the conse-quence of government incentives forcommercial plantations of pulpwood(principally Pinus elliotii E. and Pinustaeda L.), and cash crops such as soy-beans, “yerba mate” (South Americanholly, Ilex paraguariensis Saint Hilaire,Aquifoliaceae) and tea.

The first tree plantations wereestablished in the 1920s with thenative species Araucaria angustifo-lia. Pines, which were first planted in1948, and now dominate the land-scape in Misiones, especially in theWest of the Province along the Paranáriver. The first cellulose and paperplant was installed in the 1950s nearthe town of Eldorado on the Paranáriver. The cellulose and paper indus-try soon consumed all natural andplanted supplies from araucarias,and had to rely on plantations ofpines and eucalypts to meet theirneeds for fiber. By the mid-1980s,there were already over 150 000hectares of forest plantations, and asa result, forest cover in the province,including plantations, had increasedto 67% by 1985.

Due to the relatively low pricespaid by the cellulose industries forplantation pulpwood, sawmills har-vesting timber for boards began toproliferate, especially in the northernpart of the province, later spreadingto the rest of the province. The advan-tages for the development of the pulpand timber industry in Misioneswere: i) the high yields and relativelyshort rotation times of plantationspecies; ii) availability of high qualitylabor; and iii) highly diversified natu-ral forest resources.

Mixed plantation of native tree species: Enterolobium contortisiliquum(Fabaceae, “timbó colorado”), Lonchocarpus muehlbergianum (Fabaceae, “rabomolle”), Astronium balansae (Anacardiaceae, “urunday”), and Peltophorumdubium (Fabaceae, “caña fístula”), 8 to 13 year-old depending on the species.Site 1, the most degraded of the experimental sites, is located on land aroundthe Escuela Agrotécnica, owned by the National University of Misiones. Photo F. Montagnini.


FOCUS / REHABILITATION OF LANDS

Today, Misiones has about330 000 hectares of planted forest.In 2003, total production of round-wood from plantations in Misioneswas about 5 million m3, or 70% oftotal production, with the remaindersupplied from natural forests.

Most plantations consist ofexotic species such as Pinus spp.(P. elliotii, P. taeda, and others),Melia azedarach L. var gigantea(“paraíso”), Eucalyptus spp., Paulow-

nia spp., Toona ciliata M. Roem., Gre-villea robusta A. Cunn., and thenative Araucaria angustifolia. InMisiones, the area planted withnative tree species (Araucaria angus-tifolia and a few others) covers lessthan 10% of the total area of forestplantations. This situation is partlydue to insufficient informationregarding suitable silvicultural meth-ods for establishing and managingplantations of native species.

Alternative landuse systems

for ecosystemrestoration in Misiones

A number of initiatives werestarted in 1980-1990 as part of theYale School of Forestry andEnvironmental Studies (FES) collabo-rative agreement with the School ofForestry at the National University ofMisiones (UNaM). The trials focusedon finding alternatives to restoredegraded forests and lands that hadbeen abandoned by agriculture orother land uses. The trials includedmixed and single-species planta-tions, agroforestry systems and for-est enrichment planting. All trialsused indigenous species of eco-nomic value, building on local knowl-edge and previous research on eco-logical characteristics of the species.

Plantations andagroforestry systems using

indigenous tree species

In view of the difficult economicand social situation currently prevail-ing in the province, practical solu-tions are urgently needed to increaseproductivity and lessen the negativeimpacts of land use on existingresources. Local farmers are willing totry new alternatives for ecosystemrestoration, including agroforestrycombinations with the most commoncash crops. In order to suggest pro-ductive alternatives for restoringdegraded soils, experiments to testthe adaptability of native tree speciesto three sites with different degreesof soil degradation were started in1990-1991. These trials includedmixed plantations and agroforestrysystems with yerba mate (Ilexparaguariensis), the most commoncash crop in the province.

At all three sites used in thisresearch, the terrain is gently undu-lating, with slopes of less than 6%.The soil, of the Great Group Kandiu-


Balfourodendron riedelianum (Rutaceae, “guatambú blanco”), 13 year-old,growing on moderately degraded soils in site 2, in a private property near thetown of Eldorado. After surviving the critical establishment stage, this valuabletimber species grew well on low-fertility soils. Notice yerba mate (Ilexparaguariensis, Aquifoliaceae) bushes growing in the understorey.Photo F. Montagnini.

dults type according to the US SoilTaxonomy classification (Fernándezet al., 1997), is reddish, deep, well tomoderately well drained, with claythroughout the profile. These soilshave low fertility and are poor inorganic matter, nitrogen, phospho-rus, and other nutrients (Table I). Dueto their degraded condition, the suit-ability of these soils for tree planta-tions is poor to moderate.

The most degraded site (site 1)had been used for agriculture for over40 years. In contrast, site 2, with mod-erate degradation, was an abandonedfield that had been used for agriculturefor about 20 years and was subse-quently invaded by grasses (Andro-pogum spp., Pennisetum spp.). Site 3was the least degraded, and had sus-tained a plantation of tung (Aleuritisfordii Forst.) for about 20 years.

Although the soils at the threesites belonged to the same GreatGroup of classification, the differentuse histories mentioned above hasproduced very different soil degrada-tion situations at each site. Site 1 hadthe highest degree of physical degra-dation, as shown by its structuralcharacteristics and high bulk density,with the resulting aeration problemsand restrictions on plant root growth.In contrast, site 3 had the fewestsymptoms of physical degradation.The same patterns appear in thechemical quality of soils at each site.Nutrient content in site 3 was 2-3times higher than in site 1, and site 2had intermediate values for theparameters examined (Table I).

The native tree species testedwere: Enterolobium contortisiliquum(Vellozo) Morong (Fabaceae, “timbócolorado”, Lonchocarpus muehlber-gianum Hassler (Fabaceae, “rabomolle”), Astronium balansae Engl.(Anacardiaceae, “urunday”), Pel-tophorum dubium (Sprengler) Taubert(Fabaceae, “caña fístola”), Balfouro-dendron riedelianum (Engler) Engler(Rutaceae, “guatambú blanco”) andTabebuia heptaphylla (Vellozo) Toledo(Bignoniaceae, “lapacho negro”).

These species were selected fortheir ability to grow in full sunlight andfor their potential positive effects onsoils, as indicated in previous experi-ments, as well as for their timber value(Eibl et al., 2003). In Misiones, sev-eral private companies have plantedsome of these species as part of theirown research, and the UNaMresearchers had visited these trials.UNaM researchers have also con-ducted several studies on the ecologyof the most common tree species ofthe Misiones forest, with the objectiveof determining their potential for tim-ber production and other alternativeuses. It was expected that the legumi-nous species would contribute tohigher nitrogen availability in soils, assuggested by results of studies byUNaM researchers. In addition, stud-ies of the effects of some of the treespecies on soils have been conductedby Yale FES and UNaM researchers, tocompare soils under the tree canopywith grass-covered soils in adjacentareas (Fernandez et al., 1997).

Growth results of the native treespecies are shown in Tables II-IV. Inthe most degraded site (site 1),Enterolobium contortisiliquum hadthe best growth, suggesting its use torestore poor soils (Table II). In otherexperiments within the same region,E. contortisiliquum showed good per-formance when grown under 18 year-old pine plantations (P. elliottii ) witha density of 300 trees per ha. Whenplanted under pine, E. contortisili-quum trees grew about one meter inheight per year and by one cm dbhper year at four years of age, whiletheir growth in the open was affectedby attacks of Epicauta adspersa(“bicho moro”), a beetle that consu-mes the foliage (Crechi et al., 2002).Epicauta adspersa had also initiallyaffected the survival and growth ofthis species at site 3, but the treeslater recovered from the attacks.Enterolobium contortisiliquum alsogrew well in enrichment planting trialsin the Guaraní Forest Reserve inMisiones (Montagnini et al., 1997).In addition, concomitant researchresults suggest the ability of thisspecies to improve soil nitrogen andbase cation concentration (Fernan-dez et al., 1997), an excellent advan-tage when growing this species in thenutrient-poor conditions of highlydegraded sites.

Astronuim balansae was alsoobserved to be well suited to thedegraded soil conditions of site 1, con-trary to Lonchocarpus muehlber-gianum, Balfourodendron riedelianum



Table I. Chemical characteristics of soils before planting for the three sites under study.

Site Soil Organic Total Extractable pH Ca2+ Mg2+ K+ Sum of CECdepth matter nitrogen P in H2O bases(cm) (%) (%) (ppm) (cmol+/kg) (cmol+/kg) (cmol+/kg)

Site 1 0-10 2.1 0.09 1.5 5.2 4.3 1.1 0.20 5.6 7.710-30 0.9 0.07 1.0 5.1 3.6 1.0 0.09 4.7 7.0

Site 2 0-10 2.6 0.24 3.2 5.2 5.8 1.5 0.29 7.6 10.710-30 1.4 0.12 1.3 4.7 4.2 0.9 0.11 5.2 8.7

Site 3 0-10 3.9 0.31 5.4 5.4 8.6 2.3 0.41 11.3 19.610-30 2.3 0.20 4.4 4.6 6.4 1.3 0.21 7.9 12.8

Analyses of organic matter, total nitrogen, pH, CEC, extractable Ca2+, Mg2+, K, and P were performed following standard procedures for tropical soils (Anderson, Ingram, 1989; Fernandez et al., 1997).

Table II. Growth in diameter at breast height, total height and survival of four native tree speciesin single-species and mixed plantations in site 1.

Species Diameter (cm) Height (m) Survival (%)(Standard deviation) (Standard deviation)

Enterolobium contortisiliquum single- 25.4 (5.88) a 11.82 (2.36) a 46 cspecies Planted August 1990 max. 41 max. 15.8

min. 13,2 min. 6.3

Enterolobium contortisiliquum mixed 25.3 (4.67) a 10.57 (1.60) a 70 aPlanted August 1990 max. 34.3 max. 14

min. 14.9 min. 9

Peltophorum dubium single-species 8.45 (3.00 ) c 6.57 (1.67) d 78 aPlanted August 1995 max. 18 max. 15

min. 3 min. 2.3

Peltophorum dubium mixed 10.24 (2.36) b 9.18 (1.69) b 56 bPlanted August 1995 max. 18.2 max. 11.5

min. 5 min. 5.4

Astronium balansae single-species 10.18 (2.14) b 6.78 (4.2) d 59 bPlanted August 1993 max. 18.7 max. 13.6

min. 4 min. 4.7

Astronium balansae mixed 10.91 (2.04) b 8.23 (1.22) c 78 aPlanted August 1993 max. 13.7 max. 10.6

min. 7.4 min. 4.8

Lonchocarpus muehlbergianum single- 7.4 (1.19) d 4.4 (0.93) e 48 cspecies Planted August 1990 max. 9 max. 6

min. 4 min. 2.4

Lonchocarpus muehlbergianum mixed 2.8 (1.43) e 2.75 (0.56) f 28 dPlanted August 1990 max. 3.8 max. 3.6

min. 2.5 min. 1.5

Measurements done in December 2004.The experimental design consisted of randomized blocks with four replicates. Statistical analyses were performed using Variance Analysis (ANOVA) and the Duncan test for means, with p<0.05.Different letters indicate significant differences among groups.

Table III. Growth in diameter at breast height, total height and survival of three native tree speciesin agroforestry systems in site 2.


Enterolobium contortisiliquum 19.3 (4.18) a 7.92 (1.27) a 46 bPlanted August 1991 max. 28.6 max. 10

min. 10 min. 4.15

Balfourodendron riedelianum 9.85 (2,09) c 8.16 (1.72) a 92 aPlanted August 1991 max. 15.5 max. 12.9

min. 7 min. 5.8

Tabebuia heptaphylla 14.87 (3.67) b 7.97 (0.94) a 90 aPlanted August 1993 max. 25 max. 10

min. 6 min. 4,9

Measurements done in December 2004.The experimental design consisted of randomized blocks with four replicates. Statistical analyses were done using Variance Analysis (ANOVA) and the Duncan test for means, with p<0.05.Different letters indicate significant differences among groups.


and Bastardiopsis densiflora, whichdid not grow well on highly degradedsites. Although it may be too early todraw conclusions on P. dubium’sadaptability to degraded sites, thisspecies seemed to have low nutrientrequirements and to be sensitive tosoil compaction problems, thereforerequiring good soil preparation includ-ing subsoiling down to 60 cm in depth.

On site 1, the mixed plantationsgrew well in comparison with single-species stands, with the exception ofLonchocarpus muehlbergianum(Table II). The advantage of mixed E.contortisiliquum and A. balansaeplantations was a higher survival ratethan in single-species stands, whileP. dubium planted in a mixture withLonchocarpus muehlbergianum,E. contortisiliquum and A. balansae

grew higher and to a larger diameterthan in single-species stands. Onmedium fertility soils at site 2, thebest species were E. contortisiliquumand T. heptaphylla (Table III).

Balfourodendron riedelianumdemonstrated better growth on sites1 and 2, with higher fertility and lesssoil compaction than site 1 (Table IV).Overall, the best growth performancevalues were recorded for B. riede-lianum, one of the most prized treespecies locally. In contrast to E. con-tortisiliquum and A. balansae, whichappeared to be well suited to themost degraded sites, B. riedelianumgrows well in fertile soils and withadequate silvicultural management,as observed by tree heights of11 meters and 15.7 cm dbh reachedafter 13 years at site 3, Santiago de

Liniers (Table IV). The growth levelsfound at site 3 (Table IV) exceededthose found in other trials in theregion where B. riedelianum hadbeen tested in enrichment plantings,where soil conditions are generallygood (Montagnini et al., 1997).However, B riedelianum is apparentlyvery sensitive to degraded soil condi-tions, as in the case of site 1 (Table II),where it could not be established dueto high mortality or very slow growth.On site 2 (Table III) B. riedelianumgrew poorly during the first couple ofyears, possibly due to the low soil fer-tility. However, once it survived thecritical stage of establishment, thisspecies grew well in low-fertility soils,to 8.16 meters in height and 9.85 cmdbh after 13 years (Table III).

Table IV. Growth in diameter at breast height, total height and survival of two native tree speciesin agroforestry systems in site 3.


Enterolobium contortisiliquum 16.9 (5.3) a 7.7 (1.6) b 62 bPlanted August 1991 max. 25.7 max. 11.3

min. 5 min. 4.6

Balfourodendron riedelianum 15.7 (3.7) b 11.3 (2.3) a 75 aPlanted August 1991 max. 26 max. 16

min. 7.2 min. 5.3

Measurements done in December 2004.The experimental design consisted of randomized blocks with four replicates. Statistical analyses were done using Variance Analysis (ANOVA) and the Duncan test for means, with p<0.05. Different letters indicate significant differences among groups.

Commercial pulpwood plantations (principally Pinus elliotii and P. taeda) dominate the lowland landscape in Misiones. Note the natural forest cover on the top of the hill. Photo F. Montagnini.



In these trials, the association oftimber trees with yerba mate seemedappropriate, since yerba mate pro-duced good harvests yielding a short-term return on investment. Severalcrops such as cassava, maize,peanuts, peppers, sweet potatoes,beans, sweet peas, onions, watermelons, and cucumbers were inter-cropped with the trees at site 2.Production from the associated sub-sistence crops at site 2 covered thefarmer’s annual needs (Eibl et al.,2000). This plus the long-term returnsfrom timber make the systems pro-posed here an interesting alternativefor small farmers in the region. Otheragroforestry systems including nativeand exotic species are common in theregion. In particular, agrosilvopas-toral systems with improved cattlebreeds are helping many farmers toaccelerate returns on plantations,especially from araucarias and pines.

The results of this research arecurrently being used to stimulate treeplanting in community forestry proj-ects in municipalities near Eldorado,the town where the School of ForestSciences of the National University ofMisiones is located. The universityresearchers provide tree seedlings,help with tree planting and advise onspecies establishment and care.Local people with limited economicresources help to take care of theseplantations, which are expected toprovide forest products and improvethe environmental conditions (soil,water quality) of the watershed.Initial growth results among nativetrees for timber, fuelwood and fruit indegraded areas are promising at oneof the sites, the arroyo Pomar water-shed, and other municipalities intendto join and initiate similar tree plant-ing projects.

Enr ichment planting in degraded

and secondary forests

Line enrichment trials usingnative species of commercial valuewere established in 1988-1990 inoverexploited forests in Misiones,on public and private lands. Two ofthe trials were conducted on theproperty of Celulosa Argentina S.A.,located in the North-East ofthe province in Paraje Gramado,Department of San Pedro (26° 38’ S,54° 08’ W, 530 m in elevation). TheCelulosa Company owns about7 500 ha of native forest whereselective thinning is carried outusing the conventional minimumdiameter method. This forest waslogged in 1986 and the remainingbasal area (trees >10 cm dbh) afterharvest was less than 10 m2/ha(Montagnini et al., 1997).


A forest area showing recent selective cutting in accordance with the minimumdiameter system, in the Guaraní Forest Reserve, administered by the NationalUniversity of Misiones. The remaining basal area after harvest was about 10 m2/ha.Enrichment trials were established in these residual forests in 1990.Photo F. Montagnini.

Another trial was conducted inthe Guaraní Forest Reserve,Department of Guaraní (26° 15’ S, 26°56’ W, 267-574 m in elevation), alsolocated in the North-East of theprovince, approximately 150 km fromSan Pedro. This 5 340 ha reserve wasestablished in 1975 and is managedby the Department of Forest Science atthe National University of Misiones.Guaraní is part of the Yabotí ForestReserve covering 250 000 hectares,which was integrated into the UNESCOBiosphere Reserve Program in 1994.

The floristic composition andphysical characteristics of the forestreserve are typical of most nativeforests in the province. Most of thereserve remains pristine; only 1 000hectares, i.e. 20% of the total area,have been allocated for research use.Trials were conducted in an areawhere the undisturbed forest hadbeen harvested in 1990, and theremaining basal area after harvestwas about 10 m2/ha.

The overall aim of enrichmentwas to improve forest composition interms of both quantity and quality ofcommercially important species, soas to allow harvests from short andmedium cutting cycles (15 to 40

years). In the Misiones forests, about40 m3/ha of commercial trees areusually extracted using the minimumdiameter method, and the tree basalarea of the residual forests rangesfrom 10 to 15 m2/ha (Montagnini etal. 1998 and 2001). In the region,residual forests with <15 m2/ha areconsidered to be overexploited, withrelatively slow natural regeneration,and enrichment planting is recom-mended to accelerate their recovery.

Ten timber species were tested,as well as the palm Euterpe edulisMart. (“palmito”) which can be har-vested after 10-12 years for its palmheart. The enrichment trials involvedcutting lines running east to west inthe forest to provide more light forplanted seedlings. All lines were ini-tially 2 m wide and were widened to 4or 6 m in the second or third year afterplanting to increase light incidence foreach species. This was done based ongeneral information on the species’light requirements gathered fromother trials in the region. Seedlingswere one year-old, 40-50 cm tall nurs-ery specimens raised in pots.Seedlings that died were replaced upto the third year. The enrichment lineswere weeded 2-3 times per year dur-



Table V. Growth in diameter at breast height, total height and survival of four native tree speciesin forest enrichment experiments trials at the Guaraní Reserve.


Ocotea puberula 19.08 (6.9)a 9.9 (2.9)a 75 amax. 28.6 max. 14.8min. 3.5 min. 3.5

Balfourodendron riedelianum 4.3 (2.4)c 5.87 (2.4)c 55 cmax. 10 max. 9.9min. 1.0 min. 2.4

Bastardiopsis densiflora 13.3 (5.6)b 10.4 (2.7) a 65 bmax. 20.8 max. 14

min. 5 min. 5.5

Cordia trichotoma 10.9 (4.6)b 8.6 (2.2) b 75 amax. 23 max. 12.3min. 4.7 min. 4.3

Measurements made in November 2004. Tree species were planted in 1991.The experimental design consisted of randomized blocks with four replicates. Statistical analyses were done using Variance Analysis (ANOVA) and the Duncan test for means, with p<0.05. Different letters indicate significant differences among groups.

Enterolobium contortisiliquum(Fabaceae, “timbó Colorado”),13 year-old, growing onmoderately degraded soils insite 2, in a private property nearthe town of Eldorado. This nativenitrogen-fixing tree performed bestin the most degraded sites. Photo F. Montagnini.

ing the first three years and once ortwice per year thereafter as needed.

At the San Pedro site, sevenyears after planting, the timberspecies with the greatest mean heightand dbh were Bastardiopsis densi-flora (Hook et Arn.) Hassl. (Malvaceae,“loro blanco”, Enterolobium contor-tisiliquum, Nectandra lanceolata Neeset Mart ex Nees (Lauraceae, “laurelamarillo”), Ocotea puberula (Nees etMart.) Nees (Laureaceae, “laurelguaicá”, and Peltophorum dubium(Montagnini et al., 1997). Two highlyvalued timber species, Cordia tri-chotoma (Vell.) Johnst. (Boraginaceae,“peteribí”, “loro negro”), and Bal-fourodendron riedelianum, could alsobe recommended for enrichmentdespite their relatively slow growth.

At the Guaraní Forest Reserve,from measurements taken inDecember 2004, the timber specieswith greatest mean height and dbh13 years after planting were Ocoteapuberula, Bastardiopsis densiflora,and Cordia trichotoma (Table V).Ocotea puberula, a prized timberspecies, had suffered severe attacksfrom a stem borer beetle, Oncideresgutturator Fabr. (Cerambycidae),locally known as “quiritó”, “cortapa-los” or “taladro podador”, an insectthat cuts the lateral and terminalbranches of several important timberspecies in the Misiones forest(Vizcarra, 1990). After severeOncideres gutturator attacks, theOcotea puberula trees in the enrich-ment trial re-sprouted vigorously,producing the largest stem growth ofthe four species tested.

Bastardiopsis densiflora andCordia trichotoma were next in termsof height growth (Table V). Bastar-diopsis densiflora, a prized timberspecies, grows well in secondaryforests forming dense, single-speciesspecies stands. Previous experi-ments on the effects on soils ofnative tree plantations establishedthat the greatest differences in C andN soil concentrations were foundunder Bastardiopsis densiflora,where they were twice as high as

those in areas beyond the influenceof the canopy (Fernández et al.,1997). The pH was also observed tobe better under Bastardiopsis densi-flora and Cordia trichotoma com-pared to adjacent areas with no trees,while the sum of bases (Ca++, Mg++

and K+) was highest under Cordia tri-chotoma, Bastardiopsis densifloraand Enterolobium contortisiliquum.Thus, these species which performwell in enrichment planting may alsobe beneficial by improving soil char-acteristics of degraded forest areas.

Feasibil ity of enr ichmentplanting

Because of the relative complex-ity of enrichment planting manage-ment, some authors consider it eco-nomically viable only for small ormedium scales (Ramos, Del Amo,1992). The high cost of establishingand maintaining plantings in the earlyyears has been cited as one disadvan-tage of enrichment techniques.However, including species ofmedium and shorter harvest agecould improve the economics of thistechnique, and enrichment plantingcould play an important role in therecovery of degraded forests (Weaver,1987; Montagnini et al., 1997).

Tabebuia heptaphylla(Bignoniaceae, “lapacho negro”),11 year-old, growing onmoderately degraded soils in site2, in a private property near thetown of Eldorado. Together withEnterolobium contortisiliquum,this species performed best underlow and medium soil fertilityconditions, in comparison with theother species in this trial which didnot adapt to degraded soils.Photo F. Montagnini.

The association of timber trees with yerba mate shrubs appears to be anappropriate agroforestry combination, with a short-term return on investmentfrom the yerba mate leaf harvests, and production from corn and othersubsistence crops. Photo F. Montagnini.


An alternative to compensatefor the high labor costs of enrichmentis to plant species that grow quicklyand/or yield highly valued products.In Indonesia, enrichment of depleteddipterocarp forests has become aneconomically attractive alternativedue to increasing lumber prices (Kor-pelainen et al., 1995). In anotherexample, sensitivity analysis ofenrichment plantings in Kalimantan,Indonesia, showed that enrichmentof secondary forest with fruit trees,such as Dialium spp., Garcinia spp.,

and Willughbeia spp., was an eco-nomically and ecologically viablealternative (Schulze et al., 1994).Another option is to combine timbertrees with species that produce anearlier profitable harvest, such as thepalm E. edulis, to accelerate returnson investment and to make this tech-nique more economically attractive.

Management of enrichmentplantings should be complemented bytending of natural regeneration withinthe lines. The weeding necessary forinitial establishment and maintenanceof the enrichment lines also tends tofavor natural regeneration. Therefore,silvicultural treatments should bedesigned to encourage the establish-ment and growth of line plantings andat the same time favor natural regener-ation, especially of commerciallyimportant species (Sips, 1993). Oncethe seedlings are established, thewhole forest should be tendedthroughout, not just along the enrich-ment lines (Dawkins, 1961). If regener-ation in the enrichment lines is consid-ered together with planted trees,enrichment planting may become amore economically attractive alterna-tive. However, the need for trained per-

sonnel and the costs associated withtending may limit the widespreadapplicability of this approach, espe-cially at large scale.

In other trials in private proper-ties in Misiones using some of thesame species as in this article, theeconomic profitability of enrichmentplanting was calculated (Sánchez etal., 1993). For a 25-year rotation, andusing expected prices for timber fromnative species, these authors calcu-lated a 11.2% rate of return on theinvestment. Although this was high, itwas lower than the returns expectedfrom other investment alternatives atthe time. However, the growth ratesestimated by these authors were low,being based on the density of about180 to 200 trees per ha generally usedfor enrichment in the region. As dis-cussed above, other trees from natu-ral regeneration that are tended andfavored while practicing enrichmentplanting should be added in the esti-mation of final yields. In addition, theauthors pointed out that enrichmentplanting is a low-risk investment incomparison to other alternatives inthe region, so that a relatively lowerrate of return could be acceptable.



Bamboos tend to dominate,competing with naturalregeneration from woody speciesin gaps and openings with a largeamount of light as a result ofselective cutting. In this situation,enrichment planting can be analternative to accelerate forestrecovery.Photo F. Montagnini.

Bastardiopsis densiflora Hassl. (Malvaceae, “loro blanco”), one of the fastestgrowing species in the San Pedro and Guaraní enrichment trials. This speciesforms dense stands in secondary forest areas of the region and is a prizedtimber tree.Photo F. Montagnini.

They also suggested that other indi-rect benefits, such as environmentalprotection and ecotourism, ought tobe considered in evaluating the prof-itability of enrichment practices.However, these environmental bene-fits may not be directly perceived bythe local farmers, and initial govern-ment subsidies would therefore beneeded to bring this practice intomore widespread use in the region.

In Argentina, the 1999 NationalLaw (n° 25080) for the Promotion ofCultivated Forests subsidizes planta-tions with native species as well aswith non-traditional exotic species,both in enrichment planting and inopen plantation. For enrichment plant-ing, there is a restriction on the num-ber of trees that can be planted perhectare. In order to obtain the legalsubsidies, there must be enoughinformation on growth of the pro-posed species, and sometimes thenative species are not approved forsubsidies due to lack of information.This is where the results of the presentresearch become important as back-ground information that can be usedto promote enrichment planting ofnative species of the Misiones forest.

In Misiones, UnaM researchersare working on proposals to obtain sub-sidies for enrichment plantings of sev-eral native species in secondary forest.This project would benefit small farm-ers who are interested in producingorganic honey in community forestryprojects. The project includes enrich-ment planting using some of the nativetimber species tested in this study. Inthe same areas, small trees and shrubsthat grow naturally in open, degraded

areas and are used by honey bees suchas Solanum granuloso leprosum Dun.(Solanaceae, “fumo bravo”), Tremamicrantha (L.) Blume (Ulmaceae, “palopólvora”, and Brassica spp., amongothers, are tended and encouraged.The combination of species that regen-erate naturally and timber species thatare planted for enrichment results in amixed forest that lessens the risk ofonly planting species for which there islittle background information ongrowth. In addition, the species areexpected to protect the soil and offsetthe adverse environmental conditionsthat are often found in degraded sec-ondary forests, locally called“capueras”.

Enrichment adds value to previ-ously logged, low-volume forests byincreasing the expected harvestablevolume. This added value may preventtheir conversion to plantations orother prevailing uses. With increasesin the area of secondary and overex-ploited forest across the globe(Achard et al., 2002), forest recoverywill require techniques such as enrich-ment. In the province of Misiones,local farmers are seeking guidelineson species choice and managementfor the enrichment of overexploitedand secondary forests. Though long-term results are required to documentpotential growth and production qual-ity for each species, results from thetrials described in this article can pro-vide insights into the use of thesespecies for enrichment planting inoverexploited and secondary forestsin the Yabotí Biosphere Reserve andother areas in the region exposed tosimilar conditions.

Conclusions

Despite the fact that in Argentina,the National Forestry Law does notexclude native species for subsidizingopen plantations or enrichment plant-ing, few farmers are interested inplanting native species. This is mainlydue to the lack of guarantees regardingthe returns that can be expected fromnative species. For open plantations,subsidies are given only for singlespecies planted in blocks. The resultsof this study have increased the bodyof information on the growth and prof-itability of native species used foropen plantations and enrichmentplanting in Misiones, and can thushelp to encourage more farmers in theregion to plant native species.

The findings from this study arealready being used in small commu-nity forestry projects in Misiones thatinclude open mixed and single-species plantations, and enrichmentplanting of degraded secondaryforests or “capueras”. It is expectedthat more farmers in the region willjoin these projects and that the posi-tive results in terms of growth andenvironmental benefits will encour-age more widespread planting ofnative tree species.

Forestry development in theprovince of Misiones has helped toincrease productivity and to diversifythe economy of the province, whilerespecting environmental con-straints. Plantations for pulp and tim-ber are expanding continually, butthey are generally established on rel-atively flat land whereas the upperelevations of watersheds and ripar-ian areas in the province are stilllargely covered by natural forests.The relatively large proportion of for-est under protected status ensuresconservation of the diverse ecosys-tems of the region. Their use in eco-tourism is also helping to diversifythe economy of the province. Thechallenge is to ensure that forestmanagement complies with manage-ment plans, prevents illegal logging

Partial view of the arroyo Pomar watershed, where university researchers arecollaborating with resource-poor local people in tree planting projects. Earlyresults for the growth of native trees for timber, fuelwood and fruit are promising,and other municipalities are intending to join and initiate similar projects.Photo F. Montagnini.


and controls the encroachment ofpeople in the forest, especially fromthe poorly protected borders withBrazil and Paraguay. In addition,implementation of forest restorationprojects such as those described inthe present article can help toincrease ecosystem productivity andpreserve native resources.

AcknowledgementsThe trials were initially establishedwith funds from the Yale UniversityCenter for International and AreaStudies (YCIAS), the Latin AmericanStudies Center of YCIAS, and a grantfrom the A.W. Mellon Foundation(USA).

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Euterpe edulis Mart. (“palmito”) in an enrichment trial at the Guaraní Reserve.Planting this species can accelerate returns on investment, since palm hearts canbe harvested after 10-12 years. This palm does not grow well in open plantations,and is considered an endangered species in both Argentina and Brazil.Photo F. Montagnini.

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rehabilitation of degraded lands in misiones, argentina

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