Silvopastoral Systems

RESEARCH, RE VIEWS, PRACTICES, POLICY AND TECHNOLOGY

Agrosilvopastoral Systems: A Practical Approach Toward Sustainable Agriculture Ricardo 0. Russo

ABSTRACT. The practical objective of agrosilvopastoral (ASPS) systems, in areas fundamentally devoted to cattle production, is to produce goods, traditionally forestry goods such as fuelwood, poles, and timber. These goods are used to solve immediate domestic needs, to provide for local needs and also to alleviate the pressure on natural forests. By definition, ASPS is a collective name for land-use systems, implying the combination or deliberate association of a woody component (trees or shrubs) with cattle in the same site. Essentially, these systems are a model of production and conservation based on silvicultural practices complementary to pre-existing agricultural activities. From this point of view, these practices may be applied in a wide range of ecological and productive conditions. Based on this framework, several activities to achieve ASPS are proposed. [Article copies available jiwm The Haworlh Document Delivery Service: 1-800-342-9678. E-mail address: [email protected]]

Ricardo 0.Russo is affiliated with Escuela de Agricultura de la Region Tropical Humeda (E.A.R.T.H.) University, P.O.Box 650990 Miami, FL 33265. Journal of Sustainable Agriculture, Vol. 7(4) 1996 O 1996 by The Haworth Press, Inc. All rights reserved.

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KEYWORDS. Agrosilvopastoral systems, trees

INTRODUCTION Agroforestry systems (AFS), which include agrosilvopastoral combinations, are not a new thing in Central America, Mexico, or the Caribbean. Thcir roots are in Mayan civilization, where farmers practiced "roza-tumba-quema" or cutting the forest to cultivate corn from one to three years, after which the abandoned cropped area was allowed to regenerate naturally (Kellogg, 1963; Parsons, 1976; Reyes-Rodriguez, 1979). Mayan farmers also cultivated multispecific gardens with more than 20 multipurpose species in their "milpas" (Gomez-Pompa ct al., 1987). Agroforestry practices continued into the Spanish colonial times. In Mexico, they were practiced in the state of Tabasco (Arias, Lau, and Sepulveda, 1987), where cocoa was cultivated under shade in natural forest. Today in the Mexican humid tropics, more than five millon hectares are under the "roza-tumba-quema" system, where the cultivated areas are used to produce food, while the fallow areas are utilized for forest, wildlife, and animal production purposes (Hernandez X. et al., 1987).

DEFINITIONS Under the name of agrosilvopastoral systems (ASPS), there exists a set of land-use techniques implying the combination or deliberate association of a woody component (tree or shrub) with husbandry and/or crops in the same site (Combe and Budowski, 1979; Nair, 1985, 1989). Such systems contain significant ecological and/or economic interactions (Kapp, 1989) or just biological interactions (Somamba, 1990). These combinations may be simultaneous or alternate in time and space, and aim to achieve sustainable production. If only tree and animal components are prescnt, they are referred as to silvopastoral systems (SPS). ASPS also may be considcred as a set of silvicultural practices complementary to other activities (agricultural or cattle) alrcady established in a farm or in a region. From a sustainable agriculture viewpoint, ASPS should be considered as a biological strategy in search of sustainability.

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INTERACTIONS AMONG SYSTEM COMPONENTS Multiple interactions occur among components of ASPS (Borel, 1987; Bronstein, 1983). The flow diagram (Figure I), redrawn from Bronstein (1983), allows a quick and clear view of inputs, outputs, and relationships among components. Some of these interactions, as summarized by scveral authors (Borel, 1987; Bronstein, 1983, Montagnini, 1992; Torres, 1985), are as follows: 1. Trees supply organic matter to the soil through the periodic decay of leaves, flowers, fruits, branches, and dead roots. In addition, roots absorb elements from deeper soil laycrs and bring them to the surface, making them more available to the pasture. In the case of nitrogen fixing trees (NFT), soil nitrogen levels are increased. 2. Trees create a microclimate favorable for animals (shade and lower temperature). Shade intensity depends on tree density, crown diarneter, and crown structure. Shade protects animals from excessive heating from direct radiation and reduces internal temperature stress. Changes in animal thermal balance, that is, lower air temperature than body temperature, leads to lower food consumption (De Alba, 1959). Whether or not this contributes to higher animal productivity is a point of controversy. 3. Trees may compete with pasture for water, nutrients, light, and space. Competition effects will be stronger if the requirements of both are similar. Natural leaf fall and pruning help to increase the availability of water, light, and nutrients to system components. Appropriate selection of species and the selective prunings (in season and intervals) help to ameliorate competition. 4. High numbers of animals or trees arranged in groups can lead to animals crowding together looking for shade. Trampling may result and can affect plant cover and cause soil erosion and soil compaction. These conditions can deter tree growth. 5. Feed preferences of animals can affect forest composition. Over time, those species rejected by cattle can dominate. 6 . Animal component changes can accelerate some aspects of nutriment cycling by returning manures and urine to the soil. 7. Animals can spread seeds, or scarify them, which favors germination. 8. Generally, grass species growing beneath the tree canopy yield more, have a lower root:shoot ratio, and are of a different composition than those outside the canopy (Pinney, 1989).

FIGURE 1. Simplified Flow Diagram of an Agrosilvopastoral System. Redrawn from Bronstein (1 983).

ds, fertilizers, herbicides,

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ADVANTAGES AND DISADVANTAGES OF AGROSZLVOPASTORAL SYSTEMS Several authors have analyzed advantages and disadvantages of ASPS (Borel, 1987; Bronstein, 1983; Ruiz, 1983; Torres, 1985). According to Ruiz (1983), some of the factors that favor cattle components in ASPS are: Diversification of production activities within the farm reduces risk of economic disasters. Small farmers, with land limitations, may use the forest to produce food from animal origin (milk, meat) without sacrificing areas dedicated to crops. In addition to direct advantages, farmers may also obtain economic benefits from fuelwood, timber, posts, and forage, which are used eventually on the farm for cattle management. Cattle keep pastures and weeds from competing with young trees. In the case of fruit trees or palms, grazing also facilitates the harvest of fruits. Grazing of cover vegetation reduces fire risks. In the case of associations of cattle with crops, the principal advantage is that between 60 and 70% of plant biomass can be used as feed for cattle without causing competition problems with crops for human consumption. In the particular case of cattle associated with nitrogen-fixing trees, it is logical to assume that these species will contribute to soil fertility, in addition to being a protein supplement when their edible parts are utilized as forage. It is important to realize also that disadvantages exist (Ruiz, 1983). Most important are: Compaction effects on the soil are harmful but could be compensated for by the effect tree roots have on soil porosity, infiltration capacity, and soil aeration. However, this topic requires more research. Velocity and size of water drops from tree crowns to plants or crops under them can cause damage to flowers and fruits. Cultural practices, such as mechanized harvest of crops, "henificacion," or "ensilado," are interfered with by the trees. Planning with sufficient space is necessary. Sometimes ASPS has been considered a subsistence practice. This negative connotation may prevent wider acceptance. Furthermore, effects to improve these systems can be interpreted as a means to maintain the poverty status of the subsistence small farmer.

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The low levcl of knowledge on agrosilvopastoral techniques and the lack of trained personnel makes systems improvement difficult. Also, formal experimentation with these combinations is complex, not only from a practical point of view, but biometrically. They also require a long term commitment which not too many institutions are willing to assume. Where young timber trees are planted in pasture lands, problems occur due to trampling and browsing by grazing animals (Heuveldop, -19871. -- .

An obvious bottleneck for small farmers in rural areas is the lack of availability of suitable plant material (Heuveldop, 1987). IMPORTANCE OF AGROSILVOPASTORAL SYSTEMS IN COSTA RICA It is difficult to talk about ASPS without referring to husbandry in Costa Rica. The cattle census of 1988 accounted for 2.19 millon head: 64% for meat, 22% double-purpose and 14% for milk (MAGISEPSA, 1990). These activities occupied an area of 2.4 millon hectares of grasslands. However, in many farms the presence of forest fallows is common, especially when cattle activities are discontinued because of low market prices for meat. It is estimated that around 400,000 hectares of abandoned pasture lands are under fallows of different ages (Miiller et al., 1992). Although these statistics exist, it is unknown at the farm level what area percentage is managed under ASPS or has a forest component. A one-year follow-up study of 38 farms showed that 84% had forest or forest species as livinifences, shade, or for forage in pastures. In terms of forest utilization, only 69% of farmers used the forest for production and 3 1 % said they only have patches of forest because of lack of time or resources to convert it to crops or pastures (Avila et al., 1979). In 1978, the Tropical Agriculture Center for Research and Training (CATIE) established an agroforestry project and started studies of ASPS. Almost ten years later, a Silvopastoral Systems Project was established in the lowlands of the Atlantic Region of Costa Rica to develop low-risk, low-cost ASPS (CATIE, 1991). At the government level, the National Program for Development of Meat Cattle, started in 1990 (MAG-SEPSA, 1990), opened an avenue of opportunity to deepen the knowledge on ASPS. A research component on natural resources with emphasis in forests, soil, and water was added. Silvopastoral systems found most frequently in Costa Rica are: (a) trees in pastures, including grazing in secondary forests and fallows; (b) grazing

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in forest and fruit plantations; (c) living fences; (d) perimeter shelterwoods; and (e) crop and utilization of forage trees and shrubs. An example of the first c a s d e e s in pastures-has been evaluated in the grasslands of the College of Agriculture of the Humid Tropical Region (known as EARTH in Spanish), Las Mercedes de Guacimo, Costa Rica, where 29 different tree species have been identified within an area of approximately 400 hectares (Table 1). Other examples of successful ASPS that have remained throughout time are: (a) One developed in the highland areas of Costa Rica, on volcanic soils, where alder (Ainus acuminata) is planted with pastures of kikuyo grass (Pennisetum clandestinunz) and green forage such as elephant grass (fi purpureum). The alder trees, selected for their fast growth (in 15-20 year rotations trees reach 35-40 cm diameter), provide timber, fuelwood, and also have the added advantage of being an actinorhizal tree (it is host to the nitrogen-feg actinomycete Frankia in nodules of their root tissue); and (b) Another one developed in the Atlantic lowlands, where laurel (Cordia alliodora) is frequently found in pastures. During pasture maintenance, farmers favor its natural regeneration, leaving it to grow. The tree is currently a valuable timber cash crop and it is said that it contributes to the maintenance of soil structure and pasture productivity.

FIGURE 2. Trees in Pasture Lands at E.A.R.T.H. Colleae in the Atlantic Lowlands of Costa Rica. -

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TABLE 1. Tree species identified i n pasture lands at E.A.R.T.H. College, in Costa Rica.

the Atlantic lowlands of Latin name

Local name

Family

Bursera simaruba Castilla elastica Cecmpia spp. Cedrellaodorata Ceibapentandra Cordiaalliodora Dipteyxpanamensis Ficus werkleana Goethalsia meiantha Guareaspp. Hieronymsalchorneodes Hura crepitans lnga edulis Jacaranda copaia Lueheaseemani Ochmmapyramidale Pentaclethrarnacroloba Pithecelobiumlongifolium Pithecelobiurnsaman Psidiumguajaba Pterocarpushayesii Raphiataedigera Sirnaruba amara Spondias mombin Sterculiaapetala Striphnodendronexcelsum Terrninaliaamazonia Virola koschnyi Zanthoxylonmayanun

indio desnudo hule guarurno cedm amargo ceiba laurel almendm chilamate guacirno blanw ocora pil6n jabillo guaba gallinazo guecimo colorado balsa gavilan sota caballo Cenizaro guayaba sangrillo caminadora aceituno job0 panama vainillo guayabon fwta dorada lagarlillo

Burseraceae Moraceae Moraceae Meliaceae Bombacaceae Boraginaceae Fabaceae Moraceae Tiliaceae Meliaceae Euphorbiaceae Euphorbiaceae Fabaceae Bignoniaceae Tiliaceae Bombacaceae Mimosaceae Mimosaceae Mimosaceae Mirtaceae Fabaceae Palmae Simarubaceae Anacardiaceae Sterculiaceae Mimosaceae Combretaceae Myristicacae Rutaceae

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GENERAL CONSZDERATIONS WITHIN A FRAMEWORK OF SUSTAINABILITY First o f all, natural resources and environmental degradation can n o t b e isolated f r o m economic processes. The importance o f economics in environmental studies and production has lead various researchers to integrate

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the social and natural systems (Forrester, 1973; Lonergan, 1981, 1988; Lakshmanan and Ratick, 1980). These integrated economic-ecological models, although constrained by their positivist approach (Harvey, 1974), in which physical models are used to simulate economic behavior (Lonergan, 1988), have been useful. They improve the understanding of natural resources problems, the environment, and the production process. On other hand, the worldwide drastic reduction of forest areas, concurrent, with the increased demand for forest products, leads to a paradigm: production and supply of forest products. Because most of the farmers in the humid tropics live on and farm small parcels, it is financially too risky for them to experiment with small plantations of trees. Even a plantation of 2 or 3 hectares would replace other uses. This represents a large financial decision. Farmers have to see that the planting of trees is both technically and economically feasible. Within this framework, AFS should be considered as a palliate for the domestic and community supply of woody resources in an ecological, economical, and social framework: Ecological, because of its multispecific and sometimes multistratified structure. AFS increases the efficiency of radiation capture and utilization of horizontal and vertical space of the agroecosystem. Economic, because of its production, not only of food, protein, and fiber of the agricultural component, but also the production of the woody component such as fuelwood, timber, forage, poles, shade, and the contribution of organic matter to the soil, which saves fertilizer. Social, because the trees (in particular timber trees) represent a reserve of standing capital which is a stability factor contributing to internal security for the socio-economic component of the system-the rural family. Also, because of its external projection, AFS could ameliorate the needs of timber supply at the community level. Agroecosystem sustainability means profitable production without damaging the environment. So, the minimum requirement to achieve this goal must encompass the productive, environmental, and economic issues. Still, it would be incomplete if no consideration is given to the social, political, and cultural issues as well. However, one has to be aware that ASPS is not a total solution to tropical problems. It is rather an appropriate alternative that in certain cases will solve some of the problems caused by the disappearance of the forest resource, but only on a farm scale. It is not logical to think that trees integrating ASPS can replace forest plantations for pulp and paper production, but they can ameliorate local needs of timber and fuelwood.

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The 20th FA0 Regional Conference for Latin America and the Caribbean, held in Recife, Brazil October 2-8, 1988 had as its central topic "Agroforestry for Improvement of Agriculture". In this meeting, the biological-productive importance of AFS was recognized, and strong support was given to a series of recommendations leading to promote the active participation of rural communities in the preparation and application of the most appropriate AFS for each given situation. The conditions to further ASPS applications are nearly ideal: (a) forest legislation in effect in almost all tropical countries gives importance to forest plantations; (b) there is an alternative in motivating the active participation of rural communities through incentives to use the timber from forest plantations that result from agroforestry practices; (c) there exists the need for looking at adequate and practical solutions that promote a productive, ecological, and social equilibrium; (d) the Tropical Forestry Action Plan (TFAP) of the FA0 exists to implement programs of restoration, reforestation, and conservation within a prioritized productive framework; (e) there exists an actual experience in AFS in many countries, in addition to the willingness and the opportunity of planting trees by many of the farmers, and, finally; (f) there exists an organization structure in different countries. Therefore, it is proposed: a. To capitalize on the valuable experience of existent people through a diagnostic and evaluation process of all those current practices that can be considered successful agroforestry; b. To identify the most relevant practiccs with the idea of extending them to othcr situations where they can be applied; c. To establish research networks among higher education institutions and research centers that are already working with ASPS, to set regional and local ASPS data bases; d. To motivate interest and participation of the rural community in order to achieve community involvement in conservation; e. To reforest or to intercultivate rows of valuable timber trees (VTT) with annual or perennial crops everywhere possible; f. To intercultivate VTT in perennial crops already established or in the establishing process, replacing to a degree the traditional shade trees; g. To evaluate the foragc from existing living fences and to promote the establishment of live fence posts where they are still not familiar to the farmers; h. To establish VTT in pastures;

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i. To evaluate the alternative of using ASPS a s buffer zones in the boundaries of conservation areas;

j. To teach and to train o n AFS and ASPS at elementary school level; k. To d o extension activities and a planned follow-up o f agroforestry activities; 1. To integrate a network o f demonstration plots and validation, including existing multipurpose modules; m. To permit alleys o f natural regeneration in areas where cattle raising has been discontinued, a s a way to restore deforested areas, and to enrich them with VTT using all available promotional benefits; n. To increase the use of agricultural technology and to take advantage o f the technical services given by the national governments and international organizations.. Finally, the current challenge is t o produce and concurrently preserve natural resources. These objectives seem t o be divergcnt, but with the appropriate use o f known agroforestry practices, it may be possible to accomplish both production and conservation goals.

REFERENCES Avila, M., Ruiz, M.E., Peso, D., y Ruiz, A. 1979. La importancia del componente forestal en pequeiias fincas ganaderas de Costa Rica. In G. de las Salas (ed.), Taller Sistemas Agroforestales en America Latina. Actas Turrialba, Costa Rica, CATIE. pp. 175-182. Barrera, A, G6rnezl~om~a, A,, y Vazquez-YaRez, C. 1977. El manejo de las selvas por 10s Mayas: sus implicaciones silvicolas y agricolas. Biotica 2(2):47-51. Berner, P.O.1989. Investigacion en manejo forestal y agroforestal: el enfoque cientifico en el context0 de una carrera contra el reloj. El Chasqui (Costa Rica) 2 1:4-5. Borel, R. 1987. interactions in agroforestry systems: man-tree-crop-animal. In J. Beer, H.W.Fasbender, and J. Heuveldop (eds.). Advances in Agroforestry Rsearch, Preceedings. Turrialba, Costa Rica, CATIE. pp. 105-138. Bronstein, G. 1983. Los arboles en la production de pastos. h~L. Babbar (comp.), Curso Corto lntensivo Priicticas Agroforestales con enfasis en la Medicion y Evaluaci6n de Parametros Biologicos y Socio-Economicos. Turrialba, Costa Rica, CATIE. Mimeo, p.d. Centro Agronomico Tropical de Investigacion y EnseRanza. 1991. Sistemas Silvopastoriles para el Tropico H~imedoBajo. I1 lnforme Anual. Fase 11. Proyecto CATVMAG/IDA/CIID. Turrialba, Costa Rica, CATIE. 149 pp. Combe, J. and Budowski, G. 1979. Classification of agroforestry techniques: a literature review. In: G. de las Salas (cd.), Workshop Agrofor Systems Latin Amer. UNUICATIE, Turrialba, Costa Rica. pp. 17-47.

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De Alba, J. 1959. lnfluencia del clima y la calidad de 10s forrajes en su consumo. Turrialba (Costa Rica) 9(3):79-84. FA0 (1988). Plan de Acci6n Forestal para America Latina y el Caribe. Resumen ejecutivo. Roma, FAO. 22 p. Forrester, J.W. 1973. World dynamics. Wright-Allen, Cambridge, 144 pp. Gomez-Pompa, A,, Flores, J.S., and Sosa,V. 1987. The "PetKot," a man-made tropical forest of the Maya. Interciencia 12(1):10-15. Harvey, D. 1974. Population, resources, and the ideology of sciencc. Econ. Geogr. 50:256-277. Hernandez, X.E., Levi, T.S., y Arias, R.L. 1987. Hacia una evaluation de 10s recursos naturalcs renovables bajo el sistema roza-tumba-quema en Mexico. In: Lund, H.G., Caballero-Deloya, M., and Villareal-Canton, R. (eds.), Land and Resource Evaluation for Natural Planning in the Tropics: Proceedings of the International Conference and Workshop, Jan 25-31, 1987, Chetumal, Mexico. Washington, D.C., USDA Forest Service. pp. 330-340. Heuveldop, J. 1987. Silvicultural concepts in agroforestry. In Beer, J., Fasbender, H.W., and Heuveldop, J. (eds.), Advances in Agroforestry Research, Proceedings. Tunialba, Costa Rica, CATIE. pp. 50-66. Kapp, G.B. 1989. La agroforesteria como altemativa de reforestacion en la zona Atlantica de Costa Rica. El Chasqui (Costa Rica) 2 1:6-17. Kellogg, C.E. 1963. Shifting cultivation. Soil Science 95:221-230. Lakshmanan, T.R. and Ratick, S. 1980. Integrated models for economic-energyenvironmental impact analysis. In: Lakshmanan, T.R. and Nijkamp, P., Economic-Environment-Energy Interactions. Nijhoff, The Hague. 180 pp. Lonergan, S.C. I98 1. A methodological framework for solving economic/ecological problems. Pap. Reg. Sci. Assoc. 48:117-133. Lonergan, S.C. 1988. Theory and measurement of unequal exchange; a comparison between a Marxist approach and an energy theory of value. Ecol. Modelling 41:127-145. MAGISEPSA. 1990. Programa Nacional de Desarrollo de la Ganaderia Bovina de Came. San Jose, SEPSA. 52 pp. Montagnini, F. 1992. Sistemas agroforestales: principios y aplicaciones en 10s tropicos. 2 ed. San Jos6, C.R., Organizacion para Estudios Tropicales. 622 pp. Miiller, E., Guillen, L., Fedlmeier C., y Cartin, F. 1992. Bosque secundario: una reforestacion natural. San Jose, Proyecto COSEFORMA. s.p. (folleto de extension). Nair, P.K.R. 1985. Classification of agroforestry systems. Working paper no. 28. Nairobi, Kenya, ICRAF. 52 pp. Nair, P.K.R. 1989. Classification of agroforestry systems. In P.K.R. Nair (ed.), Agroforestry systems in the tropics. Dordretch, The Netherlands. Klwer Academic PresslICRAF. pp. 39-52. Parsons, J.J. 1976. Forest to pasture: Development or destruction? Rev. de Biologia Tropical 24(supl. 1):121-138. Neugebauer, 6. 1982. Los sistemas forestales: posibilidades y limites como alier-

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nativa en el uso del suelo. In: Altemativas para el uso del suelo en areas forestales del tropic0 h~imedo.T.V. INIF, MBxico DF. pp. 127-137. Pinney, A. 1989. Studying the single tree. Agroforestry Today 1(3):4-6. Reyes-Rodriguez, J.J. 1979. Algunas experiencias agro-silvicolas en Mexico. SARH, Subsecretaria Forestal y de Pesca. 42 pp. Ruiz, M.E. 1983. Avances en la investigacion de sistemas silvo-pastoriles. In L. Babbar (comp.), Curso Corto Intensivo Practicas Agroforestales con enfasis en la Medicion y Evaluacion de Parametros Biologicos y Socio-Economicos. Turrialba, Costa Rica, CATIE. Mimeo, p.d. Russo, R.O. 1984. Arboles con pasto: justification y descripcih de un estudio de caso en Costa Rica. In J.W.Beer y E. Somarriba (eds.), Investigation de tecnicas agroforestales tradicionales. Ejemplo de Organization de Cursos Cortos.Turrialba, Costa Rica, CATIE. pp. 20-27. Russo, R.O. 1990. Evaluating Alnus acun~inalaas a component in agroforestry systems. Agroforestry Systems 10:241-252. Somarriba, E. 1990. ~ Q u es e agroforesteria? El Chasqui (Costa Rica) 24:5-13. Torres, F. 1985. El papel de las leiiosas perennes en 10s sistemas agrosilvopastoriles. Turrialba, Costa Rica, CATIE. Mimeo. 46 pp. TambiBn en Agroforestry Systems 1:131-168. RECEIVED: 06/09/94 REVISED: 0813 1194 ACCEPTED: 09/07/94