The Impact of Water Points on Spatial Distribution of Vegetation, Range Condition and Soil Properties in Mbirikani Group Ranch, Kajiado District, Kenya
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2006-06
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Addis Ababa University
Abstract
The impact of water points on range condition, woody species density, soil properties dynamics, frequency distribution and palatability levels of shrubs and grasses was investigated around two water points. Density and frequency distribution data was collected from four transects radiating from the water points and sample plots marked at various consistent distance intervals of 0-50m, 200-250m, 400-450m and 600-650m.Whereby, 50m was used as a baseline measurement for all the transects. 20m by 20 m and 1m by 1m plots for density and frequency respectively were used. Range condition and soil properties’ data were obtained from 0.5m by 0.5 m respectively. One way analysis of variance (ANOVA) and linear regression based on Minitab version 12.22 computer software was employed to assess the relationship between the environmental variables and the distance from the water points. For the woody species, the number of individual stems per plot increased in number with respect to distance from the water point both within and between transects, however this was tested not significant for all the transect directions. Greater density of mature individuals than saplings was recorded with respect to distance from both water points. Two methods independently followed to assess the status of range condition, revealed similar results. The method by (Naylor and Herlocker, 1987) involved a range condition scoring criteria ranging from 0-3, optimal, minimal status respectively and squarely based on estimations. Method by (Baars etal., 1996) involved actual sampling and scoring criteria ranging from 0-10 optimal, minimal status respectively. The area close to the water points (0-50) m, had poor range condition. The other three concentric zones all reflected fair condition. All the five soil nutrients (K, P, Ca, Om and N), showed a decreasing trend in values as the distance increases from the water points. Nevertheless, only Phosphorous and Organic matter showed significant variations. Fourteen shrubs and grass species selected by experienced pastoralists were used to explore the distance, frequency distribution and palatability preference relationships. Highly desirable (highly palatable and intermediate) grasses had high abundance away from the water points. Shrubs closer to the water points were found to be less palatable. Generally, it was apparent that the water points have a contribution to rangeland degradation and that the condition is likely to worsen if the trend remains unchecked.
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Biology