Do Farm Characteristics Explain Differences in Tree Species Diversity among Western Kenyan Farms? |
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Authors: | R Kindt A J Simons P Van Damme |
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Institution: | (1) ICRAF, PO Box 30677, Nairobi, Kenya ((tel.;(2) Laboratory of Tropical and Subtropical Agriculture and Ethnobotany, Ghent University, Coupure Links 653, B-9000 Gent, Belgium |
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Abstract: | With the objective of planning diversification of on-farm tree species composition, a survey was conducted in western Kenya
involving a complete tree census (trees were defined as all woody or ligneous plants, including shrubs and lianas) and collection
of ethnobotanical information on 201 farms. Differences between farms in diversity of the 12 most frequent use-groups were
analysed by species richness, Shannon, Simpson and Berger-Parker diversity indices, and Shannon evenness and equitability.
A large range of values was detected among farms and use-groups. Multiple linear regression of diversity statistics on household
characteristics indicated significant relationships. However, these relationships generally explained low percentages of variation
(ranging 2-44%). The connection between household characteristics and use-group diversity allows targeting specific household
types with lower diversity. Farm size had a positive relationship with diversity of most use-groups. However, accumulation
curves revealed that the same area carried a larger abundance and diversity when it was composed of a greater number of smaller
farms. If the pattern of further subdivision of farmland in the survey area continues and the same differences between smaller
and larger farms prevail, then larger diversity per unit area can be expected. Because smaller farms contain smaller diversity,
however, diversification with the aim of enhancing or stabilising productivity of individual farms may become an important
priority in the survey area. The results presented allow for the identification of individual farms, use-groups, and household
types for which diversification is more relevant, and at the same time allow for impact monitoring. |
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Keywords: | Diversity indices Rényi series Domestication Diversification Species-area relationship Multiple linear regression |
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