Home About us Contact
|
Home About us Contact | ||
|
|
||
Southwestern Nigeria (southwestern + nigeria)
Selected AbstractsAerobic Heterotrophic Bacterial and Fungal Communities in the Topsoil of Omo Biosphere Reserve in Southwestern Nigeria,BIOTROPICA, Issue 2 2000A. I. Okoh ABSTRACT As a part of the surveillance effort to monitor the ecological status of Omo Biosphere Reserve in the southwestern region of Nigeria, the aerobic heterotrophic bacterial and fungal communities of the topsoil were investigated in March 1995 and April 1996, before the onset of the rainy season. Four distinct wood-tree plantations, a core strict nature reserve (SNR) area, and a buffer zone were sampled. The topsoil samples (7.5 cm depth), including the litter, were taken with an auger (8 cm diameter) and transported to the laboratory in polyethylene bags. One-gram dry weight equivalent of sample was suspended in 10 ml sterile water, and serial dilutions from it were used for the estimation of bacterial and fungal densities. The bacterial and fungal densities ranged in the order of 106 and 103 cfu/g, respectively. Out of the 18 bacterial and 16 fungal species that were obtained, 13 and 12, respectively, were isolated from the core SNR. About 46 to 69 percent of the bacteria and 50 to 83 percent of the fungi species found in the SNR were absent in different combinations in the plantations and the buffer zone; these variations were significant among the sites monitored. The bacterial and fungal species compositions were significantly different between the SNR and each of the other sites. Proportional distributions within the sites were significant only for the bacterial communities. It would appear that plantation and human activities have caused significant changes in the distribution and species richness of the heterotrophic bacterial and fungal communities relative to the undisturbed SNR area of the Omo Biosphere Reserve. [source] The effects of edge, fragment size and degree of isolation on avian species richness in highly fragmented forest in West AfricaIBIS, Issue 2 2007S. MANU Almost nothing is known of the effects of forest fragmentation on bird diversity within the heavily degraded and fragmented forest remnants in West Africa. We examined the effects of edge, fragment size and isolation on bird species richness in southwestern Nigeria where forest fragmentation is pronounced. In total, 122 km of line transects were used to survey birds and vegetation within 45 forest patches between January 2000 and March 2002: 197 species were recorded. Avian species number and total counts in forest patches were unrelated to fragment area (within the observed range of 14,445 ha), but were negatively influenced by degree of isolation and increasing distance from the edge. As the total area of forested land within 15 km of a patch fell from 4 to 0%, so 21% of species were lost. In total, six and zero species (of 154 recorded more than once) were consistently recorded in the larger and smaller forest fragments, respectively, and four and two bird species were consistently recorded in unisolated and isolated forest fragments, respectively, suggesting that the addition of ,edge' species did not compensate for loss of species sensitive to fragmentation. Diversity index was not affected by either fragment area or degree of isolation, but decreased with distance from the edge. When individual species counts were considered, 68% of species (n = 62) showed no significant effect of distance to edge. Of those 20 species which showed an effect, 12 were less common close to the edge. Most species (65%) did not respond significantly to increasing isolation but of those 22 species that did, 20 were less common in more isolated fragments. Ninety-seven per cent of species showed no significant response to area. As avian diversity and species composition, but not species number, were apparently insensitive to forest fragmentation, our findings suggest that fragmentation reduces the probability of occurrence of a wide range of West African bird species, rather than a subset of fragmentation-sensitive species. The greater apparent sensitivity of present-day West African forest bird communities to fragmentation rather than patch size might reflect previous extinctions of area-sensitive species. Minimizing further forest fragmentation might be the most effective means of conserving avian diversity in current West African landscapes where most remaining forest patches are small (i.e. < 500 ha). [source] Land cover change and land degradation in parts of the southwest coast of NigeriaAFRICAN JOURNAL OF ECOLOGY, Issue 2009Mayowa Fasona Abstract Frequent alteration in land cover often leads to decreased stability of ecosystems which can also increase the vulnerability of rural communities to externalities of environmental change. This study carried out in parts of the coast of southwestern Nigeria utilized topographic base maps and two-time Landsat TM imageries to assess the trend in land cover changes and ecosystems degradation for the three time periods 1965, 1986 and 2001. Remote sensing, geographic information systems and landscape pattern analysis were employed for data processing and analysis. The focus of the analysis was on land cover change, land degradation, and changes in landscape pattern resulting from interplay of natural and anthropogenic drivers. The results show increased trend in human-induced land cover change with concomitant severe negative impacts on ecosystems and livelihoods. About 98,000ha (30% of the area) was seriously degraded as at 2001. About 33,000ha (10%) was under permanent saline water inundation with about 21 communities already dislocated. Loss of fragile ecosystems including marshland (from 7.7% in 1965 to 1% in 2001) and mangrove (from 14.6% in 1965 to 3.1% in 2001) was intense, while over 300 ponds/small lakes which are important for the local fishing economy have disappeared. About eighteen communities were also dislocated by erosion in a section around the southeastern parts of the coastline. Landscape metrics generated, suggested increased ecosystems perturbation and landscape fragmentation. The paper also discussed the implications of these rapid changes for ecosystems stability, food security and sustainable rural livelihoods in the area. [source] Vertical integration and cost behavior in poultry industry in Ogun and Oyo States of NigeriaAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 1 2009Olasunkanmi M. Bamiro In this article, the influence of vertical integration on cost behavior in poultry farming in southwestern Nigeria is examined. The study was based on primary data obtained in cross-section survey of 211 randomly selected poultry farms in the study area. An average farmer in the sample was 44 years old; 85% were males and 72% had tertiary education. An average poultry farm in the sample had 4,342 birds, about half of which were laying birds. A set of cost and revenue share equations estimated by Zellner's seemingly unrelated regression (SUR) method revealed that vertical integration (measured in proxy by value-added sales ratio) is feed and veterinary service using, labor saving, and output augmenting. However, the scale effect of vertical integration was found to be higher in layers production than what obtains in broilers and cock/cockerel productions. [EconLit citations: Q120, D240, R340]. © 2009 Wiley Periodicals, Inc. [source] Ecological implications of Fulbe pastoralism in southwestern NigeriaLAND DEGRADATION AND DEVELOPMENT, Issue 5 2003Akin M. Omotayo Abstract The study used a combination of ethno-social surveys and Geographical Information Systems (GIS) to assess 651 pastoral households and their land use under agropastoral production systems in Ogun State, Nigeria. Yields of arable crops on agropastoralists' fields were generally low. Livestock productivity was similar on all parameters to levels in comparable contexts elsewhere across the West African subregion, but generally below possible potentials and on-farm research findings. Pastoral households' activities presently influence between 221,km2 and 523,km2 of land in Ogun State. Pastoral grazing orbits extended beyond administrative boundaries, causing potential conflicts between local crop farmers and agropatoralists. Much of the land-cover has been altered considerably around the areas of pastoral household settlements compared with the situation 20 years ago. It was concluded that a form of intervention was needed that would guarantee sustainability of the land-use system. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||