Patterns of Species Richness at Varying Scales in Western Kenya: Planning for Agroecosystem Diversification |
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Authors: | R Kindt P Van Damme A J Simons |
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Institution: | (1) ICRAF, P.O. Box 30677-00100, Nairobi, Kenya;(2) Laboratory of Tropical and Subtropical Agriculture and Ethnobotany, Ghent University, Coupure Links 653, B-9000 Gent, Belgium |
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Abstract: | Agroforestry tree domestication research is geared at promoting diversification of on-farm tree species composition. A survey
was conducted in western Kenya with the objective of exploring possibilities for diversification for a particular agroecosystem,
involving a complete tree census, tree measurement and collection of ethnobotanical information in 201 small-scale farms.
Various approaches to landscape diversification were explored, including random distribution of trees to increase alpha richness
and species richness at higher scales in the landscape, and random distribution of species composition over villages to increase
the average richness of villages. The results showed that random distribution would result in increments of average species
richness in the landscape, without requiring increments of total and average abundance. A new, fast and exact method of calculating
site-based species accumulation curves was presented. The method yielded results that were extremely close to classical algorithms
using 10,000 randomisations. Four use-groups (beverage, fodder, charcoal and soil fertility enhancement) were identified as
use-groups with alpha richness smaller than one species, but only beverage and fodder had lowest richness at all scales (fruit
and construction wood joined the four use-groups of lowest average species richness at higher scales in the landscape). The
novel approaches used in this study could be used in future biodiversity studies on species accumulation patterns, or on spatial
distribution patterns of species richness in a landscape. |
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Keywords: | Agroecosystem Agroforestry Diversification Domestication Landscape Species accumulation curves Species distribution |
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