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.

ABSTRACT  

In State as in parts of Nigeria, people depend on species in the for energy sources, poles, and other uses. Unfortunately, however, the stock and diversity of such vital resources have continued to dwindle.

This study assesses the diversity and spatial variability of woody species in the Yabo area, Sokoto State. A total of 32Km2 around Yabo town was earmarked for the study within which, a total of 50 sample points was 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 was 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 built-up 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. 

BACKGROUND TO THE STUDY  

The importance of woody species to man cannot be overemphasized. Beyond their economic value, shrubs and trees act as biological filters by helping to cleanse the environment of pollutants such as oxides of carbon, toxic gases, and heavy metals (Chakraverty and Jain, 1984).

Woody species also play a stabilizing role in landform and soils and maintaining the cycling of oxygen and other elements essential for life. Much erosion has been caused by clearing woody plants from steep slopes or from the banks of creeks and rivers.

Many wildlife species depend upon woody plants to provide essential components of their habitats. Despite the important role played by woody species in the environment, the recent assessment shows a continued and steady overall decline in wild species’ population and diversity.

Although species extinction is the most conspicuous result of biodiversity loss, it was estimated that distinct subpopulations are becoming extinct some three orders of magnitude faster than species (Rands, et al, 2010).

In most developing countries, the rate of forest clearing and tree felling is so rapid that it is feared more species may be lost eventually. It is estimated that by the year 2025, the world population will be about 8.5 billion.

The increase in population will demand higher exploitation of the natural resources for the production of food, fiber, and forests. On the other hand, the state of the world’s natural resources, especially those associated with agricultural production, appears to be declining in many areas at far higher rates.

Moreover, there is concern that the capacity of the natural resources to play their broader environmental role might be threatened. These situations imply the need for more attention for the management of natural resources and for the development of sustainable production options (ISC, 1995).

The key pressures driving biodiversity loss are overexploitation of species, invasive alien species, pollution, climate change, and especially the degradation, fragmentation, and destruction of habitats (Rands, et al, 2010).  

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StudentsandScholarship Team.