A tree for all reasons: the introduction and evaluation of multipurpose trees for agroforestry

This book provides guidance for the introduction and evaluation of woody peren-nials for use in agroforestry. By woody perennials we include not only trees, shrubs and bushes, but also palms, woody grasses, such as bamboos, and climbing plants, such as rattans. Throughout the book all these are referred to as MPTs—multi-purpose trees. Many plants of this kind are already well known in agriculture, horticulture and forestry, but others are little known outside quite restricted areas. This book is primarily concerned with guideUnes for evaluating these less well known species for introduction into agroforestry systems. In this context, introduction means taking a species to an environment where it is not well known or established. Evaluation refers to the process of determining the suitability of a particular species, either for use in an agroforestry system or for further research in combination with other plant or animal components. The evaluation process seeks, first, to determine the adaptation of the species to the site, as demonstrated by its survival and early growth, and, second, to study its phenology and morphology as a guide to its suitability for a specific agroforestry production system. Agroforestry is defined here as 'all practices that involve a close association of trees with crops, animals and/or pasture. This association is both ecological and economic. Agroforestry may involve a combination of practices in the same place at the same time (intercropping and related practices), or practices in the same place but at different times (rotational practices). The "place" may be as small as a single garden or cropland plot or as extensive as a small watershed or a vast stretch of communal grazing land' (Rocheleau et al., 1988). In some instances, it may be possible to include MPTs in prototype trials of agroforestry systems, without a prior stage of MPT species evaluation. The objec-tive of such trials is to evaluate the performance of an agroforestry system as a whole. However, there is some danger of wasting research effort if mixtures of woody and non-woody plants are tested together before enough is known about the suitability of each to the site under study. Thus, before prototype systems trials are conducted, research is often required on the MPT species. It may be possible to save time by testing a species in light of the requirements of a particular agroforestry technology—for example, a species that is to be used for hedgerow intercropping could be tested from the start as lopped hedges.

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