THE DIVERSITY AND SPATIAL VARIABILITY OF WOODY SPECIES IN YABO AREA, SOKOTO STATE

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Date
2013-02
Authors
DANGULLA, Murtala
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Abstract
n Sokoto State as in most parts of Nigeria, people depend on woody species in the wild for energy sources, construction poles and other uses. Unfortunately however, the stock and diversity of such vital resources has continued to dwindle. This study assesses the diversity and spatial variability of woody species in Yabo area, Sokoto State. A total of 32Km2 around Yabo town was earmarked for the study within which, a total of 50 sample points were randomly generated using IDRISI ANDES software. On each of the sample points, a quadrat of 50m x 50m dimension was laid and all woody species thereon were identified and enumerated. The study examined the prevailing land use/land cover of the study area and also measured woody diversity parameters which include height, diameter at breast height, basal area, density, diversity and biomass. In addition, dominance at both species and family levels were determined by the Importance Value Index (IVI). Seven major land use types were identified and a total of 671 woody stems which belonged to 40 species, 35 genera and 12 families were identified and enumerated. The highest number of stems (271) was recorded in the savannah woodland and the farmland (137) whilst the lowest was recorded over the builtup area (15) and bare ground (24). Analysis of the importance value index revealed that the dominant species in the area are Azadirachta indica, Balanites aegyptiaca, Senna Sieberiana, Combretum micranthum, Guiera senegalensis, Mimosa pigra, Parkia biglobosa, and Piliostigma reticulatum which together account for about 67.2% of the species. The extrapolation of the results obtained to the entire study area revealed that overall, 171,600 (54 stands per hectare) woody stands abound in the study area. Result of ANOVA and DMR tests shows that the biomass is the most variable parameter amongst the land uses while species density is the least. The observed species and actual number of tree stands in the area are generally low and are a reflection of severe land degradation going on in the area. Drivers of woody biodiversity loss in the area are poor physical conditions in terms of soils, vegetation and inherent extreme variability of climate. These are compounded by unsustainable use of natural resources as manifested in agricultural and grazing activities, and wood extraction. The urgent need to halt the degradation trend and improve upon the state of woody species in the area was stressed.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA, IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF DEGREE OF MASTER OF SCIENCE IN ENVIRONMENTAL MANAGEMENT DEPARTMENT OF GEOGRAPHY, FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Keywords
DIVERSITY,, SPATIAL,, VARIABILITY,, WOODY SPECIES,, YABO AREA,, SOKOTO STATE
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