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This paper presents results from a survey of border hedges on farmland in western Kenya. The survey covered 160000 ha of high potential land in eastern Siaya District and Vihiga District of western Kenya. The survey attempted to widen the knowledge of the typology, the biomass and the parameters influencing the spatial distribution of hedge types. Spatial analysis was used to delimit hedge type sub-regions (using cluster analysis) and to identify the variables influencing the spatial distribution of hedge types (using discriminant analysis). It is demonstrated that a complex association of variables is influencing the subdivision of the two districts in hedge type sub-regions in which ethnicity, population density, area in woodlots and ecological variables like elevation, rainfall and soil fertility are important variables. These variables are influencing each other and are responsible for the contrasting situation in Vihiga and Siaya District. Border hedges have similar functions in both districts (demarcation of land, to prevent cattle from entering), nevertheless species composition and dimensions differ remarkably in both districts. Border hedges in Siaya District are poorly managed or not managed at all. In Vihiga District people are used to manage their hedges. Agroforestry techniques, for example techniques based on frequent pruning of border hedges, have a high chance in being successful in this district because no additional investment in labour or time is required. The spatial distribution in the amount of biomass is strongly correlated with the distribution in the per cent area ground cover of border hedges. This means that secondary data on the area in hedges derived from aerial photographs can serve as a useful indicator of the biomass present. As a result, the most difficult part of the field survey, the destructive sampling for the determination of the biomass, can be eliminated, making general surveys considerably easier. |
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