The environmental basis of agroforestry

The physical environment affects and interacts with agroforestry systems through tree and crop growth, animal performance, management operations and interactions between the tree/shrub and non-tree components (abbreviated to tree/crop interactions). Interactions take place mainly through the media of microclimate, soil moisture and soil. They may have beneficial or adverse effects, for tree and for crop. Where the ecological interactions are on balance adverse, agroforestry designs with a large tree/crop interface, such as alley cropping should be avoided. Agroforestry has a particular potential to help check or reverse degradation of soil, forest and pasture resources. An environmental basis for agroforestry requires detailed information on climate, soils and, for sylvipastoral systems, vegetation, together with important basic, but less detailed, information on landforms, hydrology and fauna. Environmental information in five ICRAF data bases is compared. An environ-mental classification is presented, based on climatic regions combined with distinctive sit-uations of landforms and soils. Agroforestry systems could be designed to suit virtually any set of environmental conditions in the tropics and subtropics. The greatest potential con-tribution that agroforestry can make is in densely-populated steep lands

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