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Accueil du site → Doctorat → Canada → Distribution and biomass production of Acacia tortilis in a semi-arid savanna woodland, Baringo District, Kenya

University of Toronto Canada (1993)

Distribution and biomass production of Acacia tortilis in a semi-arid savanna woodland, Baringo District, Kenya

Kiyiapi, James Legilisho

Titre : Distribution and biomass production of Acacia tortilis in a semi-arid savanna woodland, Baringo District, Kenya

Auteur : Kiyiapi, James Legilisho

Université de soutenance : University of Toronto

Grade : Doctor of Philosophy (Ph.D.) 1993

Résumé
Despite the important role trees play in semi-arid areas, growth and biomass yield data for trees are generally absent in much of the published literature on these ecosystems. Therefore the study focused on Acacia tortilis (forsk) hayne, one of the most dominant tree species in semi-arid woodlands of East Africa. The study was carried out in semi-arid areas of Baringo District, Kenya. The species population structure, growth characteristics and biomass production in relation to site were examined. Field survey was accomplished by area stratification to ensure representation of all sites. Data were obtained from temporary sample plots installed along randomly established line transects. Age estimates were made by regressing number of ’annual growth rings’ against tree Diameter Breast Height (DBH). Analysis of the woodland structure revealed tree size distributions characteristic of even-aged stands. Possible age cohorts (with all sampled plots being $>$10 years in age) were observed in each of six blocks surveyed. Tree heights were more uniform within stands than breast height diameters. No significant total aboveground biomass differences were found among sites on ephemeral rivers and those found in drainage outwash areas. However, differences in stand basal area (which was highly correlated to total biomass production) were distinct when these were compared to non-riverine sites. Some evidence of self-thinning of the acacia stands was obtained for riverine and drainage sites but it was virtually non-existent in non-riverine sites. Basic allometric relations were employed to develop tree and stand biomass prediction equations and the potential use of the relationships for biomass estimation of semi-arid woodlands in general is discussed. Diameter breast height d$/sp2$ and crown dimensions were key variables in predicting component and total tree biomass. Basal area was the single most important stand parameter for stand biomass prediction although inclusion of stand height improved model precision significantly. Basal areas growth curves and a set of anamorphic site index curves were developed, to be used to make crude future biomass projections. Growth projection was hampered by lack of remeasurement data, and this leaves much room for model refinement in future.

Mots Clés : BIOMASS ENERGY ENERGY CONVERSION TREES SEMIARID ZONE KENYA AGRIPRODUCT PROCESSING DISTRIBUTION PRODUCTION RESEARCH RESULTS

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