Promising agroforestry systems in Venezuela

The main agroforestry systems in Venezuela are the multispecies plant associations in integrated coffee production system and the silvopastoral system. This paper describes the functional and structural aspects of these systems. The multilayered coffee production systems are practised mainly in the premontane moist forest of the Andes region, but are also found in other areas of the country. Various tree species are used for shade and as fence in big coffee plantations, whereas in small units with traditional production pattern, coffee is planted along with many other species, often constituting a 3–4 layer canopy. Available data are presented on the production as well as some socioeconomic aspects.The silvopastoral systems are found in the tropical dry forest (savannas) and in the very dry tropical forest of the semiarid zones of the country. A large number of trees and shrubs are found in these pastoral areas where they play both productive (fodder and feed) and service (shelter) roles.Although both these systems are practised over large areas of the country, practically no research has been done to improve them. In order to strengthen national capability to undertake such research, international support of cash and as well as technical advice is needed.

---

Resumen Los principales sistemas agroforestales en Venezuela son el Sistema integrado de producción de café y el sistema silvopastoril. En el presente trabajo se describen aspectos funcionales y estructurales de esos sistemas. El sistema de producción multi-estratificado de café es practicado principalmente en el bosque húmedo premontano de la región andina, per también es frecuentemente observado en áreas del país. Diferentes especies de árboles son utilizados como sombra y como cercos vivos en las grandes plantaciones de café, mientras que en las pequenas unidades con un patrón de producción tradicional, el café es plantado junto con una gran diversidad de especies constituyendo un dosel vegetativo de 3–4 estratos.Información disponible sobre producción y algunos aspectos socio-económicos es presentada en el trabajo.Los sistemas silvopastoriles son encontrados en el bosque seco tropical (sabanas o llanos) y en el bosque muy seco tropical de las zonas semiaridas del país. Un gran número de árboles y arbustos se encuentran en esas áreas de pastoreo donde juegan un doble rol, producción (forraje ya alimento) y servicio (refugio y abrigo).Aunque ambos sistemas son practicados en grandes áreas del país, practicamente ninguna investigación se ha llevado a cabo para mejoralos. Con el objeto de fortalecer la capacidad en el país de llevar a cabo tal tipo de investigación, se hace necessario recursos economicós y asesaría técnica por parte de organizaciones internacionales.

     

Classification of agroforestry systems

Classification of agroforestry (AF) systems is necessary in order to provide a framework for evaluating systems and developing action plans for their improvement. The AF Systems Inventory (AFSI) being undertaken by ICRAF provides the background information for an approach to classification.The words system, sub-system and practice are commonly used in AF literature. An AF system refers to a type of AF land-use that extends over a locality to the extent of forming a land utilization type of the locality. Sub-system and practice are lower-order terms in the hierarchy with lesser magnitudes of role, content and complexity. In common parlance, however, these terms are used loosely, and almost synonymously.Several criteria can be used to classify and group AF systems (and practices). The most commonly used ones are the system's structure (composition and arrangement of components), its function, its socio-economic scale and level of management, and its ecological spread. Structurally, the system can be grouped as agrisilviculture (crops — including tree/shrub crops — and trees). silvopastoral (pasture/animals + trees), and agrosilvopastoral (crops + pasture/animals + trees). Other specialized AF systems such as apiculture with trees, aquaculture in mangrove areas, multipurpose tree lots, and so on, can also be specified. Arrangement of components can be in time (temporal) or space (spatial) and several terms are used to denote the various arrangements. Functional basis refers to the main output and role of components, especially the woody ones. These can be productive functions (production of basic needs such as food, fodder, fuelwood, other products, etc.) and protective roles (soilconservation, soil fertility improvement, protection offered by windbreaks and shelterbelts, and so on). On an ecological basis, systems can be grouped for any defined agro-ecological zone such as lowland humid tropics, arid and semi-arid tropics, tropical highlands, and so on. The socio-economic scale of production and level of management of the system can be used as the criteria to designate systems as commercial, intermediate, or subsistence. Each of these criteria has merits and applicability in specific situations, but they have limitations too so that no single classification scheme can be accepted as universally applicable. Classification will depend upon the purpose for which it is intended.Nevertheless since there are only three basic sets of components that are managed by man in all AF Systems, viz. woody perennials, herbaceous plants and animals, a logical first step is to classify AF systems based on their component composition, into agrisilvicultural, silvopastoral and agrosilvopastoral (or any other specialized) systems. Subsequently the systems can be grouped according to any of the purpose-oriented criteria. The resulting system name can thus have any one of the three basic categories as a prefix; for example agrisilvicultural system for soil conservation.Some of the major AF systems and practices of the tropics are grouped according to such a framework. The scheme appears a logical, simple, pragmatic and purpose-oriented approach to classification of AF systems.     

Streuobst: a traditional agroforestry system as a model for agroforestry development in temperate Europe

The development of agroforestry for industrialised countries can be furthered by an understanding of the history and present functioning of traditional systems. In temperate Europe, fruit trees were traditionally grown on agricultural land undersown with crops or managed grassland (Streuobst). The historical evolution of this agroforestry system has been driven by the interaction of technical progress, market development and intervention by public authorities. Streuobst reached its peak in the 1930s, but has since been in continuous decline due to the development of intensively managed dwarf-tree orchards. However, even today, it still occupies approximately one million hectares in 11European countries and has a strong impact on the European fruit market. The profitability of streuobst is relatively poor due to its low labour productivity, but it has advantageous ecological and socio-cultural features, particularly in terms of biological diversity and landscape aesthetics. Accordingly, it finds strong acceptance among the general public, such that subsidised eradication programs have been abandoned and, in a number of countries, streuobst is now supported by non-governmental organisations and by state conservation policies. Modern agroforestry in temperate, industrialised countries should be oriented towards the creation of similar ecological and socio-cultural benefits in order to receive public support as a land-use system. This revised version was published online in June 2006 with corrections to the Cover Date.     

Biophysical interactions in tropical agroforestry systems

The rate and extent to which biophysical resources are captured and utilized by the components of an agroforestry system are determined by the nature and intensity of interactions between the components. The net effect of these interactions is often determined by the influence of the tree component on the other component(s) and/or on the overall system, and is expressed in terms of such quantifiable responses as soil fertility changes, microclimate modification, resource (water, nutrients, and light) availability and utilization, pest and disease incidence, and allelopathy. The paper reviews such manifestations of biophysical interactions in major simultaneous (e.g., hedgerow intercropping and trees on croplands) and sequential (e.g., planted tree fallows) agroforestry systems. In hedgerow intercropping (HI), the hedge/crop interactions are dominated by soil fertility improvement and competition for growth resources. Higher crop yields in HI than in sole cropping are noted mostly in inherently fertile soils in humid and subhumid tropics, and are caused by large fertility improvement relative to the effects of competition. But, yield increases are rare in semiarid tropics and infertile acid soils because fertility improvement does not offset the large competitive effect of hedgerows with crops for water and/or nutrients. Whereas improved soil fertility and microclimate positively influence crop yields underneath the canopies of scattered trees in semiarid climates, intense shading caused by large, evergreen trees negatively affects the yields. Trees in boundary plantings compete with crops for above- and belowground resources, with belowground competition of trees often extending beyond their crown areas. The major biophysical interactions in improved planted fallows are improvement of soil nitrogen status and reduction of weeds in the fallow phase, and increased crop yields in the subsequent cropping phase. In such systems, the negative effects of competition and micro-climate modification are avoided in the absence of direct tree–crop interactions. Future research on biophysical interactions should concentrate on (1) exploiting the diversity that exists within and between species of trees, (2) determining interactions between systems at different spatial (farm and landscape) and temporal scales, (3) improving understanding of belowground interactions, (4) assessing the environmental implications of agroforestry, particularly in the humid tropics, and (5) devising management schedules for agroforestry components in order to maximize benefits. This revised version was published online in June 2006 with corrections to the Cover Date.     

Soil carbon sequestration in agroforestry systems: a meta-analysis

Agroforestry systems may play an important role in mitigating climate change, having the ability to sequester atmospheric carbon dioxide (CO₂) in plant parts and soil. A meta-analysis was carried out to investigate changes in soil organic carbon (SOC) stocks at 0–15, 0–30, 0–60, 0–100, and 0 ≥ 100 cm, after land conversion to agroforestry. Data was collected from 53 published studies. Results revealed a significant decrease in SOC stocks of 26 and 24% in the land-use change from forest to agroforestry at 0–15 and 0–30 cm respectively. The transition from agriculture to agroforestry significantly increased SOC stock of 26, 40, and 34% at 0–15, 0–30, and 0–100 cm respectively. The conversion from pasture/grassland to agroforestry produced significant SOC stock increases at 0–30 cm (9%) and 0–30 cm (10%). Switching from uncultivated/other land-uses to agroforestry increased SOC by 25% at 0–30 cm, while a decrease was observed at 0–60 cm (23%). Among agroforestry systems, significant SOC stocks increases were reported at various soil horizons and depths in the land-use change from agriculture to agrisilviculture and to silvopasture, pasture/grassland to agrosilvopastoral systems, forest to silvopasture, forest plantation to silvopasture, and uncultivated/other to agrisilviculture. On the other hand, significant decreases were observed in the transition from forest to agrisilviculture, agrosilvopastoral and silvopasture systems, and uncultivated/other to silvopasture. Overall, SOC stocks increased when land-use changed from less complex systems, such as agricultural systems. However, heterogeneity, inconsistencies in study design, lack of standardized sampling procedures, failure to report variance estimators, and lack of important explanatory variables, may have influenced the outcomes.     

Toward a rationally robust paradigm for agroforestry systems

Because people need improved agroforestry and because there are perceived limitations in a largely scientific approach to agroforestry research and development in the past, an alternative paradigm to gaining knowledge for use in this area is suggested. It is an encompassing approach to gaining knowledge which we call the rationally robust paradigm, RRP. The paradigm has 11 components: 1. Concentrating on site-specific knowledge, often in a geographic information system; 2. being aware of the limited funds to achieve agroforestry objectives; 3. de-emphasizing induction and deduction, and their replacement by or addition of other epistemological bases; 4. accepting lower confidence levels for conclusions and subsequent action; 5. using estimates of median values; 6. using knowledge of the range limits of agroforestry phenomena and factors; 7. giving attention to the system's phenomenon of equifinality and its consequences; 8. de-emphasizing time as a factor in system analysis, and replacing it with other system phenomena; 9. using statistical regression techniques but simultaneously seeking to identify and use independent factors (e.g., solar radiation) that function significantly in many models; 10. appropriately using regression techniques emphasizing the use of hypothesized, often-non-linear relationships; and 11. operating in a conceptual clinical milieu. The paradigm is proposed for use throughout agroforestry.     

An evaluation of agroforestry systems as a rural development option for the Brazilian Amazon

In the Brazilian Amazon mass deforestation has resulted from a sequenceof road building, extractive logging, and pasture development during the pastthree decades. Ranchers have consolidated small agricultural holdings, pushingfarmers to move to forest frontiers or urban fringes, prompting furtherdeforestation and social instability. In response to this conversion ofAmazonian forests, the authors sought to identify both economically viable andmore sustainable development alternatives within the Brazilian state ofPará. There, local farmers of Japanese descent have developed a varietyof agroforestry systems in which 10 to 20 hectare (ha) fields yieldincomes comparable to 400 to 1,200 ha pastures. In addition, suchcrop fields generate substantially more rural employment per hathan do pastures. Ongoing forest conversion to pasture is clearly not a productof sound economic decision making. Improved land zoning and public policiescould favor agroforestry over further pasture expansion, stabilizing ruralpopulations while helping to conserve the Amazon's remaining forests. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cajanus cajan (L.) Millsp. as a potential agroforestry component in the Eastern Province of Zambia

Farmers in the Eastern Province of Zambia are faced with problems common to other parts of the tropics: increased pressure to expand food production leading to accelerated forest clearing, decrease in traditional fallow periods, increased soil erosion, and reductions in soil fertility. Of special concern are shortages of labor during their growing season, a shortage of staple foods during January through March, pest (termite) problems, and seasonal fires. Alleycropping appears able to solve some of the farmers' problems. Both on-farm and experiment station trials were initiated to screen potential agroforestry species. Perennial pigeonpea, Cajanus cajan (L.) Millsp., a species indigenous to the Province, showed particular promise. Cultivars grew over 3 m tall and produced up to 4.8 tons/ha dry matter (in 7 months after pruning) for green manure. Farmers reacted favorably to their experience with the on-farm trials. Ease of establishment and production of food (green pod and grain) make perennial pigeonpea a special agroforestry option in the Province, deserving additional research.     

Medicinal and aromatic plants in agroforestry systems

Agroforestry Systems - A large number of people in developing countries have traditionally depended on products derived from plants, especially from forests, for curing human and livestock...     

Perennial crop-based agroforestry systems in Northeast Brazil

Land use systems in the Northeast Region of Brazil are dominated by large holdings and extensive cultivation of perennial crops such as cashew, coconut, carnauba wax palm, babaçu palm and so on. The common feature which links these crops is the silvopastoral system of livestock (chiefly cattle, sheep and donkeys) grazing under them. Agrosilvicultural systems involving cultivation of annual subsistence crops, and in some instances other perennials, in the stands of these perennial crops is also common. The paper presents the available information on the management, production, rate of growth, economic importance, etc. of these agroforestry systems involving cashew, coconut and carnauba palm. These systems are of considerable merit in the environmental, agricultural and socio-economic conditions of Northeast Brazil. However, practically no research nor even systematic data collection has been done on these so that there is an almost total lack of information on them. In order to improve the systems, they should be studied in detail and research undertaken on various components (crops, trees and livestock) individually as well as the system as a whole. Selection of suitable species of grass and other herbaceous crops, appropriate management techniques for both overstorey and understorey species in relation to the age of the overstorey species, optimal stocking rates of animals, etc. have to be determined so as to enable plantation owners and operators to realize the full potential of these systems.     

Farming systems research for agroforestry extension

Farming systems research and extension (FSRE), as used by the global Association for Farming Systems Research-Extension, applies to a family of methodologies used to generate, evaluate and disseminate agricultural technologies in association with farmer participation. FSRE shares many attributes with Diagnosis and Design as practiced in agroforestry. The history of FSRE is traced from 1965 to the present, showing the formalization of the methodology and its critical use in sustainable agricultural technology development. In on-farm research, a primary basis for FSRE, research and extension merge in practice. The definition of recommendation domains (a fundamental concept of FSRE) is based on analysis and interpretation of multi-environmental research results as evaluated by varied criteria.In this paper, we present the results of three research projects to demonstrate the nature of farmer criteria for evaluation. Modified Stability Analysis (MSA) is used to demonstrate the relationship of on-farm research to specific extension messages. Design of on-farm research to make it amenable to analysis by MSA is discussed.Florida Agricultural Experiment Station, Journal Series No. R-03113.     

Carbon storage benefits of agroforestry systems

The process of land degradation is a local phenomenon that occurs field by field. Because of the extent at which it is occurring, however, it also has a global dimension. Agroforestry represents a link between the local and global scales. From the farmer's perspective, agroforestry can be a way to increase crop yields and the diversity of products grown. An additional benefit is the creation of a carbon sink that removes carbon dioxide from the atmosphere. Successful agroforestry systems will also reduce land clearing and maintain carbon in existing vegetation. An extensive literature survey was conducted to evaluate the carbon dynamics of agroforestry practices and to assess their potential to store carbon. Data on tree growth and wood production were converted to estimates of carbon storage. Surveyed literature showed that median carbon storage by agroforestry practices was 9 tC/ha in semi-arid, 21 tC/ha in sub-humid, 50 tC/ha in humid, and 63 tC/ha in temperate ecozones. The limited survey information available substantiated the concept that implementing agroforestry practices can help reduce deforestation.The research described in this article has been funded by the US Environmental Protection Agency. This document has been prepared at the EPA Environmental Research Laboratory in Corvallis, Oregon, through contract number 68-C8-0006 to ManTech Environmental Technology, Inc. It has been subjected to the Agency's peer and administrative review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.     

Chilling imbibition improves the germination tolerance of the Andean tree Alnus acuminata to arsenic

New Forests - Arsenic (As) is a toxic metalloid common in coal mining soils. We evaluated a stratification treatment of 48 h of chilling imbibition (3 °C) versus control...     

Do socio-psychological factors matter in agroforestry planning? Lessons from smallholder traditional agroforestry systems

Most of the well planned rural development forestry programs of the 1970s, and agroforestry in particular, were either not adopted by the intended beneficiaries or failed to meet the needs and aspirations of the rural people, particularly in the developing countries. The reasons for non-adoption in some cases appear to be technical, bio-physical, social and economic (termed as rational reasons by the planners), but in other situations the reasons are not so easily recognisable and comprehended (termed irrational reasons). These irrational reasons are the perceptions and attitude of the farmer towards farm practices, and their role in agroforestry planning has remained almost completely neglected. The present study is based on a household survey of the farmers in traditional agroforestry systems of Western Himalaya and investigates the importance of perceptional and attitudinal aspects of the farmers with regard to agroforestry adoption and extension. In the present study, farmers’ perceptions of restrictions on felling of trees from their own land and attitudes towards agroforestry were the most important sociopsychological factors which influenced tree growing. This study implies a need to take into account the socio-psychological factors of the farmers for planning socially acceptable agroforestry programs. The importance of study of various de jure rules and regulations controlling the use of on-farm tree resources and related exemptions and their association with farmers’ perceptions and tree growing is highlighted to develop policies to encourage tree growing in agroforestry.     

Valuation of fuelwood from agroforestry systems: a methodological perspective

Agroforestry Systems - This article presents a methodology for the valuation of agroforestry with respect to fuelwood supply for cooking and its opportunity cost. The share of fuelwood consumption...     

CT-measured macropores as affected by agroforestry and grass buffers for grazed pasture systems

Agroforestry and grass buffers have been proposed for improving water quality in watersheds. Soil porosity can be significantly influenced by buffer vegetation which affects water transport and water quality. The objective of the study was to compare differences in computed tomography (CT)-measured macroporosity (>1,000-μm diam.) and coarse mesoporosity (200- to 1,000-μm diam.) parameters for agroforestry and grass buffer systems associated with rotationally grazed and continuously grazed pasture systems. Soils at the site were Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalf). Six replicate intact soil cores, 76.2 mm diam. by 76.2 mm long, were collected using a core sampler from the four treatments at five soil depths (0–50 cm at 10-cm intervals). Images were acquired using a hospital CT scanner and subsequently soil bulk density and saturated hydraulic conductivity (K _sat) were measured after scanning the cores. Image-J software was used to analyze five equally spaced images from each core. Bulk density was 5.9% higher and saturated hydraulic conductivity (K _sat) values were five times lower for pasture treatments relative to buffer treatments. For the 0–10 cm soil depth, CT-measured soil macroporosity (>1,000 μm diam.) was 13 times higher for the buffer treatments compared to the pasture treatments. Buffer treatments had greater macroporosity (0.020 m³ m⁻³) compared to pasture (0.0045 m³ m⁻³) treatments. CT-measured pore parameters were positively correlated with K _sat. The project illustrates benefits of agroforestry and grass buffers for maintaining soil porosity critical for soil water and nutrient transport.     

The pejibaye palm (Bactris gasipaes H.B.K.) as an agroforestry component

The pejibaye palm was domesticated by the Amerindians as part of their indigenous agroforestry systems. The multiple uses of its fruit make it an attractive food species, while high production makes it an attractive economic proposition. Its growth habit is ideal for a canopy strata in some types of agroforestry schemes and, by controlling the number of stems to be maintained, may be modified to fit different species mixes. Several Brazilian mixed cropping experiments are mentioned, although results are not yet available. The Costa Rican experience with pejibaye * coffee mixed cropping is examined, with special reference to Tucurrique, Cartago. Two hectares of pejibaye, with coffee and banana are shown to lucrative. Research needs are discussed, with special emphasis on the question of multiple versus single stemmed plantings and modifications of the pejibaye ideotype for use in multi-stemmed, multi-species plantations. The pejibaye has significant potential for the small farmer and a greater potential if improved for both agroforestry and monoculture.Earlier versions of parts of this paper were presented at the 2nd Reunion IUFRO Working Group 51.07.07 and at the Seminar on Advances in Agroforestry Research, both in Turrialba, Costa Rica.     

Planning optimal economic strategies for agroforestry systems

Design of agroforestry systems requires a land management planning process that clearly specifies wants, needs and objectives along with the land's suitability for potential agroforestry practices. Within this planning process economic analysis can be used to analyze agroforestry alternatives to help determine the proper system to apply. Specifically, production economics coupled with capital theory and valuation techniques can provide measures of economic performance in terms of present net values, benefit-cost ratios and internal rates of return. These economic performance measures can be used to determine the best joint production level for a particular agroforestry practice. Once these best combinations have been defined, linear programming can be applied using these best joint production combinations as decision variables along with considering a wide range of additional constraints and requirements. A hypothetical example is used to illustrate the planning process and how these economic tools can be combined as a package to help determine optimal agroforestry strategies.     

Nutrient cycling in two traditional Central American agroforestry systems

A preliminary nutrient cycling study quantified total and temporal nutrient inputs via litterfall and pruning residues in two agroforestry systems: (1) Coffea arabica (perennial crop)-Erythrina poeppigiana (leguminous shade tree); and (2) C. arabica-E. poeppigiana-Cordia alliodora with emphasis on the effect of the timber tree C. alliodora. The total annual input of litterfall plus pruning residues was similar in both associations. Total annual input from E. poeppigiana was less than half in the association with C. alliodora than without, but the litterfall from this latter species compensated for the loss. Large differences in the total annual nutrient input of K, Ca and Mg was found between associations, but not for N or P. The amount of nutrients recycled by the associated trees reached the recommended level of fertilizer required for coffee production. The inclusion of C. alliodora within the C. arabica-E. poeppigiana association resulted in a more evenly distributed annual nutrient input.     

Supporting and regulating ecosystem services in cacao agroforestry systems

Cacao agroforestry systems (CAFS) can provide supporting services such as optimum light conditions for cacao growth, water and nutrient cycling and regulating services such as pest and disease control and climate regulation. This review considers recent literature on the manifestation of these services in CAFS around the world to provide an overview of scientific knowledge. Crown structures of associated trees can facilitate optimum light conditions for cacao growth, and provide water through vertical root segregation. Leaf litter fall and roots from associated species contribute to nutrient cycling. Both nitrogen-fixing and non-nitrogen-fixing species can provide nutrients to the cacao plant, though competition from certain species may limit phosphorus and potassium uptake. Pest and disease regulating services can arise through careful shade management to create a microclimate which reduces susceptibility of cacao to fungal diseases and sun-loving pests. All CAFS store carbon to varying degrees; those resembling original forest much more than simple two-species systems from which shade trees are removed after maturity of the cacao stand. CAFS also promotes biodiversity conservation depending on structure, management, and landscape arrangement, though not to the extent of natural forests. Research opportunities to increase provision of these services include optimal spatial arrangement for nutrient cycling and functional diversity as well as landscape connectivity for biodiversity conservation. Trade-offs between carbon storage, biodiversity, cacao yield and socio-economic resilience are presented, indicating that optimization of ecosystem services in CAFS requires consideration of interactions between all services, including socio-cultural and economic ones.