fits from the tree products (timber, fuelwood, leaf mulches, etc.), and from their ecological effects, for example, nutrient recycling, or attracting birds and other ...
38 Selecting Tree Species for Plantation Florencia Montagnini
Key Points to Retain Plantations are a useful tool for restoration especially in areas where degradation is advanced, for instance in conditions of severe soil compaction, invasion by grasses, and advanced fragmentation. In many cases information is lacking on local tree species that can be used for plantations: site adaptability, seed sources, germination and nursery requirements, and need for fertilisation. Techniques for planting and tending of species are important to consider: need for fertilisers, mycorrhizae, irrigation, etc. It is always preferable to use native species instead of exotic species, if a native species is available and grows well in the region.
1. Background and Explanation of the Issue Tree plantations are sometimes the only alternative in restoring forest landscapes, at least in the short term, especially on very badly degraded soils. Low soil fertility, soil compaction after abandonment from cattle grazing,
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and invasion by grasses and other aggressive vegetation can be serious obstacles to natural forest regeneration. As the area of degraded lands expands, there is a greater need for tree species that can grow in such conditions and yield useful products (timber, fuelwood, and others) as well as environmental benefits (recovery of ecosystem biodiversity, soil conservation, watershed protection, carbon sequestration). Tree species chosen for a plantation in the context of forest restoration can provide benefits from the tree products (timber, fuelwood, leaf mulches, etc.), and from their ecological effects, for example, nutrient recycling, or attracting birds and other wildlife to the landscape. The choice of a tree species depends on whether both productive and ecological advantages can be achieved in the same system, and in some cases one function, either productive or environmental, may be desired. Within a forest landscape, the preferred choice for restoration would be natural regeneration. Planting would only be a secondary option, to be used in cases where natural regeneration cannot proceed due to the obstacles mentioned above (poor soil conditions, long distances to seed sources, isolation, invasion by aggressive grasses). Within a landscape context, there should be a balance of socioeconomic goals (e.g., productivity) and biodiversity objectives for restoration. The following factors influence species’ choice for plantations:
38. Selecting Tree Species for Plantation
1.1. Goals 1.1.1. Target Ecosystem Productivity and Biodiversity Fast-growing, native pioneer species with high productivity are recommended for the initial stages of restoration of degraded lands. These species can help in facilitating the environment for later successional, longer-lived species whose end products are more valuable (better timber quality).
1.1.2. Saving Endangered Local Species Preference should always be given to local species, especially those that are endangered. Fast-growing exotic species such as eucalypts, acacias, or pines should be used only when there are no available seeds of native species, or when environmental conditions are too harsh for any native species to survive. Exotic tree species predominate both in industrial and rural development plantations worldwide; however, native trees are more appropriate than exotics, because (1) they are often better adapted to local environmental conditions, (2) seeds may be more generally available, and (3) farmers are usually familiar with them and their uses. Besides, the use of indigenous trees helps preserve genetic diversity and serves as habitat for the local fauna. Disadvantages of the use of native species are (1) uncertainty regarding growth rates and adaptability to soil conditions; (2) general lack of guidelines for management; (3) large variability in performance and lack of genetic improvement; (4) seeds of native tree species are often not commercially available and have to be collected; (5) high incidence of pests and diseases (e.g., the attack of the shoot borer Hypsipyla grandella to species of mahoganies and cedars); and (6) lack of established markets for many species. One of the strongest arguments for the use of native tree species in plantations is the high value of the wood and its increasing scarcity in commercial forests. Many native tree species of valuable timber grow well in open plantations, with rates of growth com-
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parable or superior to those of exotic species in the same sites.332,333
1.1.3. End Use of Products Most plantations whose purpose is to restore forest landscapes also have a productive purpose. Globally, half of forest plantations are for industrial use (timber and fibre), one quarter are for nonindustrial use (home or farm construction, local consumption of fuelwood and charcoal, poles), and one quarter are for nonspecified uses.334 Among the nonspecified uses there are small-scale fuelwood plantations, plantations for wood to dry tobacco, etc. Therefore, species’ choices reflect the end use of each plantation, while considering the purpose of forest restoration. For example, the native Araucaria angustifolia is used to replant deforested regions in Misiones, in North East Argentina, with the purpose of selling highquality timber in a 40 to 45-year rotation. Araucaria thinnings are also a good fibre source. As they are native trees these plantations also hold local flora and fauna.
1.2. Issues Related to Use of Native Species 1.2.1. Genetic Selection For several native species in developing countries there may not be enough genetic selection for the desired traits (fast growth, soil recovery, or other). Much research has been conducted by local institutions, universities, and ministries of agriculture and forestry. For example in Central America, Centro Agronómico Tropical de Investigación y Enseñanza (CATIE) has done genetic selection of local species such as Cordia alliodora, Vochysia guatemalensis, and other native species.335
332 333 334 335
Piotto et al., 2003a,b. Montagnini et al., 2002. FAO, 2000. CATIE: www.catie.ac.cr.
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1.2.2. Seed Availability For many native species, studies on the phenology of trees may be needed (i.e., timing of flowering, fruiting, seed production, and seed collection). In addition, there must be enough seed storage capacity, which in some cases may require refrigeration, desiccation, and other procedures to accommodate seeds of tree species from mature forest. In the case of seeds from pioneer species, these are generally smaller, drier, and easier to store. At CATIE in Turrialba, Costa Rica, the seed bank has facilities suited to several native and exotic species that can be used in forest restoration, and this seed bank serves countries throughout Latin America. When the information is not known, specific tests have to be developed to understand the germination requirements and characteristics of each seed. Finally, growing requirements in the nursery must also be known, including need for fertiliser, inoculation with mycorrhizae, and time when they can be transplanted to the field conditions.
1.2.3. Preference by Local Farmers Farmers most often prefer species whose silvicultural characteristics are well known, and species that have well-defined end uses and good markets. In many cases they also prefer native over exotic species. Seed or seedling availability in local nurseries is also an important factor defining farmers’ preferences.
2. Examples 2.1. Plantations of Native Species for Restoration of Mine Spoils in Southeastern United States In the Appalachian region of the southeastern United States, surface mining for coal has been extensive, coal being the main source of energy for power plants that generate electricity. Concern about the use of exotic species for mine soil reclamation has directed efforts toward native species, but the choices are narrowed considerably by the need for plant
materials that can be established readily on adverse sites. For example, the Tennessee Valley Authority has planted sycamore (Platanus occidentalis) and sweet gum (Liquidambar styraciflua), which had performed the best in greenhouse studies in terms of growth, drought tolerance, and commercial value of products.336 Surface coal mine lands are covered with grasses and other herbaceous species. The lands are reclaimed by returning mine spoil to the mined-out areas, grading when necessary, and planting with aggressive cover plants that will aid in preventing soil erosion as the trees mature. Drip irrigation is used in the initial establishment phases of the tree plantations. Replanting is done as needed one year after initial planting. These systems are successful in recovering mine spoil lands; however, substantial investments are needed to ensure tree establishment and growth. For example, sweet birch (Betula lenta) has also been used in mine reclamation because of its ability to grow on substrates that vary widely in tilth, concentrations of toxic metals, and fertility.337 Inoculation with ectomycorrizhae (Pisolithus tinctorius) resulted in higher seedling biomass and better nutrient and water uptake. Inoculation with mycorrhizae is thus recommended to allow this species to flourish on surface mine spoils without heavy application of chemical fertilisers.
2.2. Mixed Plantations with Native Species for Restoration of Degraded Pastures at La Selva Biological Station, Costa Rica Twelve native tree species were planted in mixed and pure plantations on degraded pasturelands at La Selva Biological Station in the Caribbean lowlands of Costa Rica, with the objectives of recovering soils and ecosystem biodiversity. There were three plantations, each with four species: Plantation 1: Jacaranda copaia, Vochysia guatemalensis, Calophyllum brasiliense, and Stryphnodendrom microstachyum; Plantation 2: Terminalia amazonia, Dipteryx panamensis, Virola koschnyi, and 336 337
Brodie et al., 2004. Walker et al., 2004.
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Paraserianthes sp., Plantation 3: Hieronyma alchorneoides, Vochysia ferruginea, Balizia elegans, and Genipa americana. In each plantation there was one nitrogen-fixing species, a relatively fast-growing species, and a slowergrowing species. The criteria for species’ selection were growth rate and economic value, potential impacts on soils and nutrient cycling, and seedling availability.338 At 2 to 4 years of age, mixed plantations had greater growth and lower pest damage than pure stands for three of the 12 species tested, and there was no damage or no differences between pure and mixed conditions for the other species. The costs of plantation establishment were lower for the slower-growing species in mixed than in pure stands. When plantations were 9 to 10 years old, most species had better growth in mixed than in pure plantations. However, the slower-growing species grew better in pure than in mixed stands. Mixed plantations (combinations of three to four species) ranked among the most productive in terms of volume.339 Mixed plantations had a more balanced nutrient stock in the soil: 4 years after planting, decreases in soil nutrients were apparent in pure plots of some of the fastest growing species, while beneficial effects such as increases in soil organic matter and cations were noted under other species. The mixed plots showed intermediate values for the nutrients examined, and sometimes improved soil conditions such as higher organic matter. The mixtures ranked high in terms of carbon sequestration in comparison with the pure plots of faster-growing species.340,341 The mixtures of four species gave higher biomass per hectare than that obtained by the sum of a quarter hectare of each species in pure plots.342
2.3. Examples from Temperate Europe During the last decade there have been increasing afforestation activities in several European 338 339 340 341 342
Montagnini et al., 1995. Piotto et al., 2003b. Montagnini and Porras, 1998. Shepherd and Montagnini 2001. Montagnini, 2000.
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countries. In Denmark, afforestation of former arable land with oak (Quercus robur) and Norway spruce (Picea abies) has been done extensively. An evaluation of soils under these plantations with ages ranging from 1 to 29 years, and a mixed plantation with both species (200 years of age) showed considerable accumulation of organic matter in the tree biomass and in the soil, especially in the older stands.343 In the southwestern Alps in France, the forest service has attempted forest restoration of badlands for erosion control since 1860, with the exotic Pinus nigra (Austrian black pine). The pines were expected to serve as nurse for the native broadleaved vegetation. A study done 120 years following reforestation showed that pines were too dense to allow for enough natural regeneration under their canopy: thinning and enrichment planting would be needed to accelerate regeneration of native species. The reestablishment of indigenous tree species was not inhibited by lack of nearby seed sources or by soil fertility. Thinning would facilitate the dissemination of seeds of the native species. Patches of native trees planted in enrichment could serve as additional seed sources of native species.344
3. Outline of Tools 3.1. Genetic Selection Both tree breeding and silviculture have improved growth rates of several industrial species of eucalypts and pines. Good examples are Eucalyptus grandis and E. urophylla in Brazil. Much genetic improvement has been done by private companies, especially for the most frequently used species of pines and eucalypts. Research on other species, including indigenous trees, is underway at universities and other research institutions. For some native species, genetic improvement has advanced with trials of seed origin and progenies, the first step in the domestication of a species. For example, for Cordia alliodora, Vochysia 343 344
Vesterdal et al., 2002. Vallauri et al., 2002.
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guatemalensis, and other native species in Central America, CATIE in Costa Rica has determined what are the best provenances (specific origin of the seed in a region or locality in a given country) that suit most planting conditions. In addition, progeny studies have helped to find what are the best sources of seed for Acacia mangium, Eucalyptus grandis, and other species.
3.2. Plant Ecology Information on the following ecological characteristics of tree species will be useful in helping to select them for plantation purposes: light requirements, growth under different soil fertility conditions, resistance to drought, tolerance to low or high pH, tolerance to high concentrations of toxic metals, resistance against pest and disease, ability to sprout and to respond to pruning and coppicing, seed production, germination characteristics, need for inoculation with mycorrhizae, need for fertilisers, wood characteristics, and uses. In most cases basic ecological information on tree species can be found at universities, ministries of agriculture, or departments of forestry. Local information can also be obtained from nurseries, agricultural or forestry cooperatives, and from conversations with local producers. However, sometimes native species are poorly known, yet another reason for people’s tendency to use exotics, which have been better studied.
3.3. Choosing Species, Designs, and Management to Stabilise Degraded Soils
matter, total nitrogen, calcium, and phosphorus were found under Vochysia ferruginea, a species common in forests in the region. In Bahia, Brazil, values of at least five soil parameters under 15 out of the 20 species of the plantations were similar to or higher than those found under forest. Several species contributed to increased carbon and nitrogen, including Inga affinis, Parapiptadenia pterosperma, Plathymenia foliolosa (leguminous, N-fixing species), Caesalpinia echinata, Copaifera lucens (leguminous, non–N-fixing), Eschweilera ovata, Pradosia lactescens (of other families). Others increased soil pH and/or some cations, such as Copaifera lucens, Eschweilera ovata, Lecythis pisonis, and Licania hypoleuca. In Misiones, in North Eastern Argentina, the greatest differences in soil carbon and nitrogen levels under tree species and grass were found under Bastardiopsis densiflora, where they were twice those in areas beyond the canopy influence. The pH was higher under Bastardiopsis densiflora and Cordia trichotoma, while the sum of bases (calcium + magnesium + potassium) was highest under Cordia trichotoma, Bastardiopsis densiflora, and Enterolobium contortisiliquum. Most of the species identified in this research for their positive influence on soil properties are used in restoration projects, commercial plantations and agroforestry in each region.
3.4. Plantation Design—Pure or Mixed-Species Plantations
Recent research in Costa Rica, Brazil, and Argentina investigated plantation tree species that could serve to ameliorate soil properties in degraded lands.345 In Costa Rica, in just 3 years soil conditions improved in the tree plantations compared to abandoned pasture. In the top 15 cm, soil nitrogen and organic matter were higher under the trees than in pasture, with values close to those found in 20-year-old forests. The highest values for soil organic
Mixed species’ plantations have been established at several locations with varying results. However, results from a number of field experiments suggest that mixed designs can be more productive than monospecific systems.346 In addition, mixed plantations yield more diverse forest products than pure stands, thereby helping to diminish farmers’ risks in unstable markets. Farmers may prefer mixed plantations to diversify their investment and as a potential protection against pest and diseases, in spite of the technical difficulties of establishing and managing mixed plantations. Mixed stands may
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Wormald, 1992.
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also favour wildlife and contribute to higher landscape diversity. As seen from the example presented above, mixed plantations can have many productive and environmental advantages over conventional monocultures. However, their main disadvantage lies in their more complicated design and management. Mixed plantations thus are often restricted to relatively small areas, or to situations when diversifying production is a great advantage, such as for small farmers of limited resources.
4. Future Needs For forest landscape restoration, only native species should be used in plantations, except if, as in some of the cases mentioned earlier, there are good specific arguments for the use of exotics. Therefore, increased knowledge of characteristics and silviculture of native tree species is needed to assist in this objective. In particular, more information is needed on the performance of indigenous species in plantation conditions. In addition, silvicultural guidelines for plantations with indigenous species are needed to increase their adoption by local farmers. Market values are also an important factor influencing the adoption of native species by local farmers. A key question in species’ choices with the dual purpose of restoration and production is how to balance economic objectives with biodiversity ones. Finally, there are some trade-off issues: Is it best to have smaller areas of exotic plantations or larger areas of native plantations? Again a balance between the two objectives— restoration and production—should give insights into the answer.
References Brodie, G.A., Bock, B.R., Fisher, L.S., et al. 2004. Carbon Capture and Water Emissions Treatment System (CCWESTRS) at fossil-fueled electric generating plants. Third annual technical report 40930R03 (October 1, 2002–September 30, 2003) for U.S. Department of Energy/National Energy Technology Laboratory Award Number
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DE-FC26–00NT40930. Tennessee Valley Authority/Public Power Institute, Muscle Shoals, AL, in partnership with the Electric Power Research Institute, Palo Alto, CA. FAO. 2000. Global Forest Resources Assessment 2000. Main report. http:/www/fao.org/forestry/fo/fra/main. Montagnini, F. 2000. Accumulation in aboveground biomass and soil storage of mineral nutrients in pure and mixed plantations in a humid tropical lowland. Forest Ecology and Management 134:257–270. Montagnini, F. 2002. Tropical plantations with native trees: their function in ecosystem restoration. In: Reddy, M.V., ed. Management of Tropical Plantation-Forests and Their Soil Litter System. Litter, Biota and Soil-Nutrient Dynamics. Science Publishers, Enfield (NH) USA, Plymouth, UK, pp. 73–94. Montagnini, F, Campos, J.J., Cornelius, J., et al. 2002. Environmentally-friendly forestry systems in Central America. Bois et Forêts des Tropiques 272(2):33–44. Montagnini, F., González, E., Rheingans, R., and Porras, C. 1995. Mixed and pure forest plantations in the humid neotropics: a comparison of early growth, pest damage and establishment costs. Commonwealth Forestry Review 74(4):306–314. Montagnini, F., and Porras, C. 1998. Evaluating the role of plantations as carbon sinks: an example of an integrative approach from the humid tropics. Environmental Management 22(3):459–470. Piotto, D., Montagnini, F., Ugalde, L., and Kanninen, M. 2003a. Performance of forest plantations in small and medium sized farms in the Atlantic lowlands of Costa Rica. Forest Ecology and Management 175:195–204. Piotto, D., Montagnini, F., Ugalde, L., and Kanninen, M. 2003b. Growth and effects of thinning of mixed and pure plantations with native trees in humid tropical Costa Rica. Forest Ecology and Management 177:427–439. Shepherd, D., and Montagnini, F. 2001. Carbon sequestration potential in mixed and pure tree plantations in the humid tropics. Journal of Tropical Forest Science 13(3):450–459. Vallauri, D., Aronson, J., and Barbero, M. 2002. An analysis of forest restoration 120 years after reforestation of badlands in the south-western Alps. Restoration Ecology 10(1):16–26. Vesterdal, L., Ritter, E., and Gundersen, P. 2002. Changes in soil organic carbon following afforestation of former arable land. Forest Ecology and Management 169:137–147.
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Walker R.F., Mc Laughlin, S.B., and West, D.C. 2004. Establishment of sweet birch on surface mine spoil as influenced by mycorrhizal inoculation and fertility. Restoration Ecology 12(1):8–19. Wormald, T.J. 1992. Mixed and pure forest plantations in the tropics and subtropics. FAO Forestry Paper 103, Rome.
Additional Reading Carnus, J.-M., Parrotta, J., Brockerhoff, E.G., et al. 2003. Planted forests and biodiversity. An IUFRO contribution to the UNFF Intersessional Expert Meeting on the Role of Planted Forests in Sustainable Forest Management: “Maximising planted forests’ contribution to SFM,” Wellington, New Zealand, 24–30 March 2003. In: Buck, A., Parrotta, J., and Wolfrum, G., eds. Science and Technology—Building the Future for the World’s Forests and Planted Forests and Biodiversity. IUFRO Occasional Paper No. 15. International Union of Forest Research Organisations, Vienna. Evans, J. 1999. Planted forests of the wet and dry tropics: their variety, nature, and significance. New Forestry 17:25–36. Montagnini, F., and Jordan, C.F. 2005. Plantations and Agroforestry Systems. In: Montagnini, F., and Jordan, C.F. 2005. Tropical Forest Ecology. The Basis for Conservation and Management. SpringerVerlag, Berlin–New York. Parrotta, J.A. 2002. Restoration and management of degraded tropical forest landscapes. In: Ambasht, R.S., and Ambasht, N.K., eds. Modern Trends in Applied Terrestrial Ecology. Kluwer Academic/ Plenum Press, New York, pp. 135–148. Parrotta, J.A., and Turnbull, J.T., eds. 1997. Catalyzing native forest regeneration on degraded tropical lands. Forest Ecology and Management (Special Issue) 99(1–2):1–290. Wadsworth, F.H. 1997. Forest production for tropical America. USDA Forest Service.
General Guidelines on Plantations Cossalter, C., Pye-Smith, C. 2003. Fast-Wood Forestry. Myths and realities. Forest Perspectives.
Center for International Forestry Research (CIFOR), Jakarta, Indonesia. www.cifor.cgiar.org/. Contains information on controversial issues regarding plantations such as social relevance, economic aspects, environmental effects. Evans J. 1992. Plantation Forestry in the Tropics. Oxford University Press, Oxford, England. One of the most complete textbooks on plantation forestry for tropical countries. FAO. 2000. Global Forest Resources Assessment 2000. Main report. http:/www/fao.org/forestry/ fo/fra/main. The Food and Agriculture Organisation of the United Nations (FAO) publishes periodically statistics and information on plantations worldwide, area covered, uses, land-use changes, species, and other relevant information. Forest Stewardship Council guidelines. www.fscus. org/. Contains materials related to certification of forest plantations; a full section on plantation forestry, principles, and criteria for sustainable management of plantation forestry. International Tropical Timber Organisation (ITTO). 2002. Guidelines for the restoration, management and rehabilitation of degraded and secondary tropical forest. ITTO Policy development series no. 13. www.itto.or.jp. Gives detailed guidelines for how to assess a situation of forest degradation and to decide what is the best alternative for restoration. Siyag, P.R. 1998. The Afforestation Manual. Technology and Management.TreeCraft Communications, Jaipur, India. Focusses on semi-arid regions. The book has a technical manual, explaining nursery techniques, site selection and preparation, fencing, soil and water conservation strategies, planting, care and maintenance of the plantations; a management manual, dealing with organisational aspects of afforestation, activity planning, monitoring, quality control and productivity, and record keeping; a section containing technical charts and tables to be used as models and reference; a section on management of charts and tables, and a tree planting guide. WWF Web site on forest landscape restoration. www.panda.org/forests/restoration. Provides concepts, information on forest restoration projects in Africa, Asia/Pacific, Europe, and Latin America.
