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