Trade-offs between rubber production and maintenance of diversity: the structure of rubber gardens in West Kalimantan, Indonesia

The goal of this study was to assess the potential of small-holder rubber cultivation in agroforestry gardens to fulfill simultaneously the goals of conservation and sustainable rural development. I examined the structure and species composition of trees in 11 rubber gardens in West Kalimantan, Indonesia, using a single 0.10 ha plot per garden. Although 41 distinct morphotypes were encountered, rubber (Hevea brasiliensis) dominated the sample of 370 trees. Richness within plots varied (3–15 morphotypes), as did the predominance of rubber (24–97% of all basal area, 24–91% of all individuals). The importance of rubber within a garden was significantly negatively correlated with the number of morphotypes present. This result suggests that tree diversity may limit potential productivity of rubber gardens. Thus, small-holders may not be willing to maintain diversity at the scale of a single garden. Although species-accumulation curves indicate that substantial tree diversity may exist across all rubber holdings, diversity is likely to be lost from the system if individual owners reduce species richness in their gardens. Rubber agroforestry as currently practiced in West Kalimantan is not an ideal model for matching rural development needs with the achievement of conservation goals. Other models, such as tengkawang- and durian-based fruit gardens, do exist in Kalimantan and elsewhere, and should be evaluated for incorporation into policy and development strategies.     

Adoption potential of fruit-tree-based agroforestry on small farms in the subtropical highlands

Worldwide, fruit-tree-based agroforestry systems have been only modestly studied, although they are common on smallholder farms. Such systems based on apple (Malus spp.), peach (Prunus spp.), and pear (Pyrus spp.) are common in northwest Guatemala as low intensity homegardens and are known to increase total farm productivity in communities where farm size is a limiting factor. This study investigated the potential for adoption of fruit-tree-based agroforestry by resource-limited farmers using ethnographic investigation and linear programming simulations of farm activities at the household level. Two communities with differing demographics, infrastructure, and access to regional markets were selected based on the presence of extensive fruit-tree-based agroforestry. The influences of family size, land holdings, and tree and crop yields on the optimal adoption levels of fruit trees were evaluated through a comparative study of the varying social and physical infrastructure present in the two communities. Fruit-tree-based agroforestry was potentially more attractive to relatively prosperous families or those with larger land holdings. Improvements in fruit-tree productivity and interspecies competition were of greater importance where family land holdings were smaller. The inability of families to produce sufficient food to meet annual needs, poor fruit quality, and lack of market infrastructure were identified as constraints that limit adoption. The complementarity of production with the dominant maize (Zea mays) crop, home consumption of fruit, and the potential to generate additional cash on limited land holdings were identified as factors promoting adoption of fruit-tree-based agroforestry.     

Agroforestry potential of Dacryodes edulis in the oil palm-cassava belt of southeastern Nigeria

Between June 1993 and June 1994, 112 farmers in the oil palm (Elaeis guineensis)-cassava (Manihot esclentus) belt of southeastern Nigeria were interviewed to determine the status and agroforestry potential of Dacryodes edulis. Between 50% and 100% of respondents in different states within the belt owned D. edulis trees. On average, a farmer owned 9.3 trees, the largest number being 16, by farmers in Imo State. Twenty percent of farmers in the system rated D. edulis their best farm tree. It was present in all the farm niches: homegardens (51.4%), tree crop plots (20.7%) food crop plots (11.4%), secondary forest/fallow (14.2%) and virgin forest (2.5%). The tree is planted primarily for home consumption and sale to generate cash. At the current densities, on-farm D. edulis trees generally did not decrease yield of companion crops or trees. Except for ring weeding around the stem, D. edulis trees received little or no management attention. More than 50% of the trees produced 33 to 50 kg of fruit tree⁻¹ annually. This is valued at US $0.4 to 0.8 kg⁻¹. Farmers were willing to plant more D. edulis trees provided trees with traits such as less height for easy harvesting of fruits, larger fruit, more fruits, sweeter fruits and year round production of fruits were available. Possible agroforestry technologies into which D. edulis may fit include live fences, scattered trees in food crop fields, shade trees in tree crop plots and contour bund or hedgerow planting. Research is required to determine best tree accessions, canopy management strategies, optimum tree population and improved methods on post- harvest handling of fruits. This revised version was published online in June 2006 with corrections to the Cover Date.     

Agroforestry Tree Seed Production and Supply Systems in Malawi

A sustainable agroforestry tree germplasm supply system is vital to resource-constrained smallholder farmers who depend on agroforestry to improve the productivity of their farm enterprises. Successful adoption of agroforestry hinges on the development of a sustainable agroforestry tree germplasm supply system. This paper reviews the agroforestry tree seed supply system in Malawi, with a view to determining its sustainability and quality. Currently, more than 90% of the documented agroforestry tree seed distributed to farmers is produced by smallholder farmers collected mainly from scattered farmland trees, the remainder being produced from seed orchards and seed stands owned or controlled by research organizations. Three organizations—namely the Land Resources Centre (LRC), National Tree Seed Centre (NTSC) of the Forestry Research Institute of Malawi (FRIM) and the World Agroforestry Centre (ICRAF)—were identified as major procurers of agroforestry tree seed produced by smallholder farmers. Agroforestry germplasm is distributed to farmers by non-governmental organizations (NGOs) and government agricultural and forestry extension departments. The procurement and distribution of germplasm to farmers is in general effective. The major challenge to sustainability of agroforestry tree germplasm distribution in Malawi is dependence on donor funding. The agroforestry tree seed system is, to some extent, sustainable with regards to production, although the genetic quality of the germplasm is low. Germplasm storage facilities at national level are available and possibly adequate, but knowledge and information on effective low-cost tree germplasm storage systems at household level are limited. Sustainability could be enhanced by strengthening of grass-root organizations involved in tree seed production to institutionalize the distribution through farmer–farmer exchange. There is also a need to support the development, promotion and adoption of low-cost tree germplasm storage facilities by smallholder farmers.     

Process studies in aPinus radiata-pasture agroforestry system in a subhumid temperature environment. II. Analysis of dry matter yields in the third year

In this paper we analyzed the dry matter yields (DM) produced in an agroforestry trial consisting of pine trees grown over (1) Control (bare ground), (2) ryegrass/clovers (Lolium perene/Trifolium spp.), (3) ryegrass only, and (4) lucerne (Medicago sativa) during the third growing season between 1992 and 1993. In addition these pastures were grown alone in separate plots in the open. The results show that:

Traditional tree crop based agroforestry in coffee producing areas of Harerge,Eastern Ethiopia

A preliminary survey of seven coffee producing Awrajas (Provinces) in eastern Ethiopia revealed that there is a traditional tree crop based agroforestry system being practised by the farmers. Coffee (C. arabica) was found to grow under the shade of several trees, 16 species, usually intercropped by one or several, a total of 15, important grain, fruit, vegetable, stimulant, oil-seed and spice crops. The majority of the trees, 69%, is leguminous and Ficus spp. The system is characterized by the integration of crops, livestock and sometimes apiculture. Recommendations are made for future studies.     

A comparison of alley cropping and block planting systems in sub-humid Bénin

Alley cropping would be acceptable to farmers in West Africa, if the amount of tree-crop competition could be reduced and crop yields increased and stabilized. The importance of overall tree-crop competition in alley cropping was therefore quantified at three locations in the Republic of Bénin, by comparing the performance of a maize-cassava intercrop and mixed hedges of Gliricidia sepium and Flemingia macrophylla in an alley cropping system, where the tree-crop interaction was high, and in a cut and carry system with block plantings, where the interface was restricted to one face. The establishment and productivity of trees in both agroforestry systems depended strongly on the natural soil fertility of the site, K and Ca being critical for both species. Alley hedges produced progressively more cut dry matter with higher leaf proportions than tree blocks and hence yielded significantly higher nutrient masses. Overall, the cut dry matter from five cuttings per cropping season ranged among locations from 855 to 1651 kg ha^–1 yr^–1 for alley hedges and from 777 to 869 kg ha^–1 yr^–1 for tree blocks. Differences in yields of maize and cassava between both systems were insignificant in all three environments and all cropping years under observation. The results of this study suggest that the overall effect of tree-crop competition was unimportant, but that tree-tree competition was the decisive factor in determining the total system productivity.     

Selection of native trees for intercropping with coffee in the Atlantic Rainforest biome

A challenge in establishing agroforestry systems is ensuring that farmers are interested in the tree species, and are aware of how to adequately manage these species. This challenge was tackled in the Atlantic Rainforest biome (Brazil), where a participatory trial with agroforestry coffee systems was carried out, followed by a participatory systematisation of the farmers experiences. Our objective was to identify the main tree species used by farmers as well as their criteria for selecting or rejecting tree species. Furthermore, we aimed to present a specific inventory of trees of the Leguminosae family. In order to collect the data, we reviewed the bibliography of the participatory trial, visited and interviewed the farmers and organised workshops with them. The main farmers’ criteria for selecting tree species were compatibility with coffee, amount of biomass, production and the labour needed for tree management. The farmers listed 85 tree species; we recorded 28 tree species of the Leguminosae family. Most trees were either native to the biome or exotic fruit trees. In order to design and manage complex agroforestry systems, family farmers need sufficient knowledge and autonomy, which can be reinforced when a participatory methodology is used for developing on-farm agroforestry systems. In the case presented, the farmers learned how to manage, reclaim and conserve their land. The diversification of production, especially with fruit, contributes to food security and to a low cost/benefit ratio of agroforestry systems. The investigated agroforestry systems showed potential to restore the degraded landscape of the Atlantic Rainforest biome.     

Assessing farmers’ interest in agroforestry in two contrasting agro-ecological zones of Rwanda

Uptake and management of agroforestry technologies differs among farms in Rwanda and needs to be documented as a basis for shaping future research and development programs. The objective of this study was to investigate current agroforestry practices, farmers’ preferences, tree management and perspectives for agroforestry technologies. The study consisted of a combination of a formal survey, a participatory tree testing, farmer evaluation and focus group discussions in the Central Plateau (moderate altitude) and the Buberuka (high altitude) agro-ecological zones. A survey and a tree testing exercise with a range of species: (timber species—Eucalyptus urophyla, Grevillea robusta; legume shrubs - Calliandra calothyrsus, Tephrosia vogelii; and fruit species—Persea americana and Citrus sinensis) were carried out in Simbi (Central Plateau) and Kageyo (Buberuka) with farmers from different wealth status who received tree seedlings for planting, managing, and evaluating. Simbi had more tree species farm^?1 (4.5) than Kageyo (2.9). Fruit trees occurred most frequently in Simbi. Grevillea robusta, Calliandra calothyrsus and Tephrosia vogelii were mostly established along contours, fruit trees in homefields and Eucalyptus urophyla trees in woodlots. Survival was better on contours for Grevillea robusta (58–100 %) and Calliandra calothyrsus (50–72 %). Tree growth was strongly correlated with the total tree lop biomass in Eucalyptus urophyla (R ² = 0.69). Grevillea robusta was most preferred in Simbi and Eucalyptus urophyla and Calliandra calothyrsus in Kageyo. The study provided information useful for revising the national agroforestry research and extension agenda and has important implications for other countries in the highlands of Africa.     

Agroforestry adoption in Haiti: the importance of household and farm characteristics

Most agroforestry-adoption studies are based on surveys of "non-adopters." An understanding of the circumstances that have led to a change of attitude of the adopters will be valuable in our efforts to enhance adoption rates. This study was undertaken to provide such knowledge based on a large agroforestry extension project involving 200,000 farm families and covering 25% of all rural households in Haiti. A questionnaire-based survey of the project participants was conducted covering 1,540 households and 2,295 fields in four regions of Haiti. Information was recorded about each farm and family member through interviews with farmers and visits to their farms. The results confirmed that farmers make decisions about tree culture based on household- and field characteristics. Different farmers consider trees differently depending upon how they fit into their farm-family strategy. In general, farmers installed tree hedgerows on fields of less secure tenure, of lesser fertility, and steeper slope, while on closer, more fertile fields of greater tenure security, tree seedlings and fruit trees were more common and there was a greater density of mature trees (>10 cm DBH). More money was realized from sale of tree products on actively cropped fields in more secure tenure and having more fertile soil. Older farmers managed a greater density of trees, especially when the land was in secure tenure status. This broad-based study shows that agroforestry implementation strategies in poor countries such as Haiti should be based on a thorough knowledge of how farmers use household and field characteristics to make adoption decisions. It also suggests that agroforestry-adoption studies should account for the dynamic changes occurring during extended time periods.This revised version was published online in November 2005 with corrections to the Cover Date.     

Agroforestry Systems as Alternative Land-Use Options in the Arid Zone of Thal,Pakistan

Agroforestry offers unique opportunities for increasing biodiversity, preventing land degradation, and alleviating poverty, particularly in developing countries, but factors explaining the adoption by farmers are not well understood. A survey of 524 farm households was conducted in Bhakkar district of Punjab, Pakistan to study factors that determine the adoption of agroforestry on the sand dunes in the resource-deficient region of Thal. Two types of agroforestry systems were studied: intercropping and border cropping (also known as boundary or perimeter planting). Both agroforestry systems included irrigated cultivation of the timber trees Eucalyptus camaldulensis (local name: sufeda) and Tamarix aphylla (local name: sars) with wheat, chickpeas (Cicer arietinum) (local name: chana) or cluster beans (Cyamous tetragocalobe) (local name: guars). The majority of the farmers was in favour of intercropping and border cropping. Most farmers reported the protection of nearby crops from dust storms as the most important positive perception about both agroforestry systems. Age, education, and farm to market distance were significant determinants of agroforestry adoption. Older and less-educated farmers, with farms closer to markets were less likely to adopt tree planting or border cropping in Thal. In general, the agroforestry systems examined were more likely to be adopted by farmers who can wait 3–4 years for harvesting crop outputs, but not by poorer farmers who are totally dependent on subsistence agriculture and cannot afford the high initial cost of agroforestry establishment, nor can they wait for crop output for extended periods. Furthermore, the adoption of both agroforestry systems was more likely in remote marginal areas than in areas close to markets. To increase agroforestry adoption rates, government policies should strengthen farmers’ knowledge of every stage of agroforestry through extension services, focusing particularly among the prime prospects, i.e. farmers who will be most likely to adopt agroforestry. Once the prime prospects have adopted it, the older, less-educated, and poor farmers of the rural population can be also focused on to motivate adoption.     

Traditional agroforestry practices in Zimbabwe

Traditional agroforestry systems in the communal areas of Zimbabwe are described. There are systems centered on main fields, on home gardens, on homesites and on grazing areas. In the main fields, the major tree-related management practice is the conservation of preferred indigenous fruit trees. Fruit trees are also the focus of forestry activities around the gardens and the homesite; but here it is the planting of exotic species. In a localized area of Zimbabwe Acacia albida is important in fields. There is almost no use of tree fallows in Zimbabwe. Trees in grazing areas have numerous roles, but at present there is little knowledge about traditional management practices in these areas. In the development of agroforestry systems in Zimbabwe it is suggested that those systems designed to improve fodder production will make a significant contribution to farm productivity because of the importance of cattle in the farming system and the present fodder shortage. Interventions involving the planting of fruit trees are likely to be very successful, as there is much interest in such planting. Another area that needs to be developed is that of tree plantings to improve soil fertility.     

Development of utility and location indices for classifying agroforestry species: the case of Rwanda

In a study of farmer knowledge and experimentation of trees and tree cultivation, two categories of farmer consultants were identified, tree experts (n = 44) and control farmers (n = 70), via a two stage process of knowledge ranking and community interviews conducted in three communes in southern Rwanda in 1992. A detailed inventory of tree species was conducted revealing two key characteristics for on-farm trees: multiple utility and high locational flexibility. In order to logically organize the species inventory, two indices, a utility index (UI) and a locational flexibility index (LFI), were developed. The two indices were calculated for each species and then plotted as the axes on a bivariate grid. While few species had both high utility and flexibility indices, the majority that did were indigenous species long used in agroforestry systems (e.g., Euphorbia tirucalli, Vernonia amygdalina, Erythrina abyssinica, etc.). A few naturalized exotics introduced in the 1930s (e.g., Grevillea robusta, Eucalyptus camaldulensis, E. saligna, E. maideni, Cupressus lusitanica and Persea gratissima) were also appreciated for their multiple utility and locational flexibility. Farm sizes varied, averaging 1.27 ha among tree experts and 0.18 ha in the control group. The mean number of species cultivated was significantly higher on tree expert farms (P < 0.01). However, tree density was much lower on tree expert farms (731 trees · ha^–1) than on control farms (1,689 trees · ha^–1). Competitive species were found primarily on larger farms, whereas smaller farms were associated with species of greater UI and LFI. Farmers demonstrated deliberate and rational choices about which trees to plant in accordance with each species utility and flexibility in relation to land availability.     

Afforestation of savannah with cocoa agroforestry systems: a small-farmer innovation in central Cameroon

Cocoa cultivation is generally considered to foster deforestation. Contrary to this view, in the forest–savannah interface area in Cameroon, farmers have planted cocoa agroforestry systems on Imperata cylindrica grasslands, a soil-climate zone generally considered unsuitable for cocoa cultivation. We undertook a survey to understand the agricultural and ecological bases of this innovation. Age, cropping history and marketable cocoa yield were assessed in a sample of 157 cocoa plantations established on grasslands and 182 cocoa plantations established in gallery forests. In a sub-sample of 47 grassland cocoa plantations, we inventoried tree species associated with cocoa trees and measured soil organic matter levels. Marketable cocoa yields were similar for the two types of cocoa plantations, regardless of their age: 321?kg?ha^?1 in cocoa plantations on grasslands and 354?kg?ha^?1 in cocoa plantations in gallery forests. Two strategies were used by farmers to eliminate I. cylindrica prior to the establishment of cocoa plantations, i.e., cropping oil palms in dense stands and planting annual crops. Farmers then planted cocoa trees and fruit tree species, while preserving specific forest trees. The fruit tree and forest tree densities respectively averaged 223 and 68 trees?ha^?1 in plantations under 10?years old, and 44 and 27 trees?ha^?1 in plantations over 40?years old, whereas the cocoa tree density remained stable at 1,315 trees?ha^?1. The Shannon–Weaver index increased from 1.97 to 2.26 over the same period although the difference was not statistically significant. The soil organic matter level was 3.13?% in old cocoa plantations, as compared to 1.7?% in grasslands. In conclusion, our results show that the occupation of grasslands by cocoa agroforestry systems is both an important example of ecological intensification and a significant farmer innovation in the history of cocoa growing.     

Understanding patterns of tree adoption on farms in semi-arid and sub-humid Ethiopia

Trees on farms are a widespread feature of landscapes across a large part of Ethiopia with an important role in enhancing the resilience of smallholder livelihoods through the provision of ecosystem services. Despite their importance, little is known about what trees are planted or retained from natural regeneration by different types of farmers that results in the pattern of tree cover found in the region. We address this knowledge gap through analysis of household survey data from semi-arid and sub humid areas of Oromia regional state. A set of composite variables that represent distinctive patterns of tree cover on farms were derived from principal component analysis and Pearson correlation analysis. This revealed two major tree adoption strategies: farmer managed natural regeneration (FMNR) of trees to meet subsistence needs as well as contributing to other ecosystem services; and, high value agroforestry (HVAF) involving planted trees used largely to produce fruits, timber and fodder. Regression analysis further identified fine-scale variation in ecological and socio-economic factors that affect which of these two broad strategies are adopted by farmers. Favorable climatic conditions coupled with institutional arrangements to control free grazing were pre-conditions for HVAF, whereas poor biophysical potential and sloping land provided a positive incentive for farmers to adopt FMNR. Farmers with preferences for tree species with multiple utilities and locational flexibility favored FMNR while adoption of HVAF was more asset-driven. Our findings reveal that farmers integrate many native and exotic tree species on their farms to meet their variable farm conditions, needs and asset profiles in stark contrast to most tree promotion efforts that focus on a few, usually exotic, tree species. We recommend that future agroforestry promotion should embrace a diversity of tree species appropriate to matching the fine scale variation in ecological conditions and farmer circumstances encountered in the field.     

Biomass and production of fine and coarse roots of trees under agrisilvicultural practices in north-east India

An understanding of the rooting pattern of tree species used in agroforestry systems is essential for the development and management of systems involving them. Seasonal variation, depth wise and lateral distribution of biomass in roots of different diameter classes and their annual production were studied using sequential core sampling. The investigations were carried out in four tree species under tree only and tree+crop situations at ICAR Research Farm, Barapani (Meghalya), India. The tree species were mandarin (Citrus reticulata), alder (Alnus nepalensis), cherry (Prunus cerasoides) and albizia (Paraserianthes falcataria). The contribution of fine roots to the total root biomass ranged from 87% in albizia to 77% in mandarin. The bulk of the fine roots (38% to 47%) in the four tree species was concentrated in the upper 10 cm soil layer, but the coarse roots were concentrated in 10–20 cm soil depth in alder (46%) and albizia (51%) and at 0–10 cm in cherry (41%) and mandarin (48%). In all the four tree species, biomass of both fine- and coarse-roots followed a unimodal growth curve by showing a gradual increase from spring (pre-rainy) season to autumn (post rainy) season. Biomass to necromass ratio varied between 2 to 3 in the four tree species. The maximum (3.2) ratio was observed during spring and the minimum (2) in the rainy season. In alder and albizia, the fine roots were distributed only up to 1 m distance from the tree trunk but in the other two species they were found at a distance up to 1.5 m from the tree trunk. The annual fine root production varied from 3.6 Mg ha^–1 to 6.2 Mg ha^–1 and total production from 4.2 to 8.4 Mg ha^–1 in albizia to mandarin, respectively. Cherry and mandarin had a large number of woody roots in the surface layers which pose physical hindrance during soil working and intercultural operations under agroforestry. But the high biomass of roots of these two species may be advantageous for sequential or spatially separated agroforestry systems. However, alder and albizia have the most desirable rooting characteristics for agroforestry systems.This revised version was published online in November 2005 with corrections to the Cover Date.     

Domestication of Irvingia gabonensis: 3. Phenotypic variation of fruits andkernels in a Nigerian village

Domestication of Irvingia gabonensis, a fruit tree grown in agroforestry systems in West and Central Africa, offers considerable scope for enhancing the nutritional and economic security of subsistence farmers in the region. Assessments of phenotypic variation in ten fruit, nut and kernel traits were made on twenty-four ripe fruits from 100 Irvingia gabonensis trees in Ugwuaji village in southeast Nigeria, a center of genetic diversity for this species. There were important differences between the young planted trees of this study and the older unplanted trees of a similar study in Cameroon. Significant and continuous tree-to-tree variation was found in fruit mass(69.0–419.8 g), flesh mass (59.5–388.8 g), nut mass (9.5–40.6 g), shell mass (4.9–30.9 g) and kernel mass (0.41–7.58 g); fruit length (49.2–89.3 mm) and width (46.2–100.5 mm) and flesh depth (12.9–31.4 mm), as well as considerable variation in flesh colour, skin colour, fruit taste and fibrosity. Some fruits were considerably bigger than those found in Cameroon. These quantitative results will help in the development of cultivars within participatory approaches to agroforestry tree domestication, and so promote poverty alleviation and sustainable agriculture. This revised version was published online in June 2006 with corrections to the Cover Date.     

Indigenous agroforestry of Pohnpei

Plant species and cultivars of the indigenous agroforestry system of Pohnpei were surveyed in transects through 54 randomly-selected farms. The agroforestry system was characterized by extensive cultivation of yams (Dioscorea), aroids (Alocasia), and Piper methysticum under a permanent overstory of breadfruit, coconut, and forest remnant trees and a middle canopy of Hibiscus tiliaceus, Musa spp., and Morinda citrifolia. In the 10 ha of survey plots, 161 species were found, of which 102 were trees, shrubs, and crops and 59 were uncultivated herbaceous plants. Numbers of tree, shrub, and crop species per farm ranged from 16 to 37 with an average of 26. Twenty-eight breadfruit and 38 yam cultivars were found in the survey plots, showing that cultivar diversity is an important component of the biological diversity maintained and utilized in Pohnpeian agroforests.     

Farmer perspectives on agroforestry opportunities and constraints in cape verde

In the água de Gato Watershed on the island of Santiago, Cape Verde Islands, 51 farmers were surveyed regarding their attitudes and knowledge of agroforestry. The farmers identified eight constraints to agroforestry implementation, with virtually all indicating that a source of loan funds was the major concern. Space or land constraints and availability of tree seedlings were identified as constraints by 94% and 88%, respectively. Despite these concerns, 92% of the farmers expressed a willingness to adopt or improve agroforestry practices in the watershed, with 73% expressing a willingness to establish fruit trees, 53% willing to establish trees or shrubs for fuelwood, and 16% willing to plant trees for shade.     

Tree domestication for agroforestry: present status and future directions

Seven different activities constitute tree domestication: (1) manipulation of tree populations by silvicultural practices; (2) enhancement of site productivity; (3) control of destructive agents; (4) evolution of trees under natural selection; (5) semi-natural selection for survival in the socio-agricultural circumstances in which trees are grown; (6) conscious human selection for desired characteristics; and (7) correlated response to selection (which usually involves reduction of those plant parts that are not desired). Each of these activities is discussed, and its contribution to the present makeup of tree populations used for agroforestry is considered.Although tree domestication has been practiced by farmers for many centuries, selection and breeding programs for multipurpose agroforestry trees have existed for only the past thirty years. Some of the problems faced by existing tree improvement programs are discussed; these include: multiplicity of usable species, great demand for multipurpose trees (MPTs), existence of improvement programs with few species, difficulty of combining desired traits in a multipurpose ideotype, high cost and slow progress with present methods, and the fate of improved material introduced on farms. Among the solutions considered is more involvement of farmers in the process of selection, testing, and propagation of MPTs. The possible use of species mixtures also holds promise.