Browsing by Author "Soka, G. E."

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Land use and vegetation cover dynamics in and around Kagoma Forest Reserve in Tanzania
(Selectedworks, 2013) Nzunda, N. G.; Munishi, P.K.T.; Kashaigil, J. J.; Soka, G. E.; Monjare, J. F.
Kagoma Forest Reserve (KFR) is found in Kagera Region, Tanzania and is comprised of a large area of Miombo woodland. The extent of land use and vegetation cover changes in and around Kagoma Forest Reserve was investigated. Remote sensing and GIS techniques were used to analyze land use and vegetation cover changes over the past 23 years which revealed the occurrence of significant land use and vegetation cover transformation from one land use class to another. During the first period of 12 years under observations (1988-1999), woodlands increased by 5.8%, cultivated lands increased by 5.9%, settlements increased by 0.52% and forests decreased by 5.64%. During the next 11 years period under observations (1999-2010), woodlands decreased by 22.97%, cultivated lands increased by 6.07%, settlements increased by 9.14% when year 1999 was used as a common baseline data year for both periods and forests which decreased by 2.5%. There was a slight increase in settlements from 1998 to 1999 but there was a rapid increase thereafter. It was estimated that vegetation cover was decreasing at the rate of 45.08 ha (0.27%) per year. The study concludes that, there have been significant changes in land use pattern and forest cover in and around KFR in Tanzania which require concerted actions to reverse the changes. The establishment and enforcement of different laws and regulations relating to natural resources and land use planning could improve land tenure and resource use in villages bordering the forest.
Modeling black rhinoceros (Diceros bicornis) population performance in East Africa: the case of Lake Nakuru National Park, Kenya
(2014-03-06) Rija, A. A.; Soka, G. E.; Owino, A.
The black rhinoceros have declined across Africa both in numbers and range distribution, making long-term population persistence of this iconic species uncertain. We conducted simulation models to predict population performance of black rhinoceros in Lake Nakuru National Park under different scenarios of environmental variation and translocation regimes. A decade-long (1987-1997) demographic data were used to construct stochastic simulation models using VORTEX computer program. In addition, we assessed extinction risks and patterns of heterozygosity among the modelled populations (reported every five years) to characterize the dynamics of this population over a hundred years. The population of black rhinoceros showed varying patterns of fluctuations under different scenarios. The best-case scenario showed a considerable increase in the modelled population with the population attaining the highest growth (population growth (λ)= 1.04) after 40 years. The mean final population size for the successful cases was 70.85±2.0 animals, which was relatively close to the carrying capacity used in the simulation. The expected heterozygosity was 0.912±0.02 suggesting that the remaining population may be genetically viable. Further, environmental variation of 1-2% magnitude across the various age categories, and without translocation, had no significant effect on the deterministic growth rate of the population. Maintaining the translocation of 2 males and 2 females on yearly basis would significantly boost and sustain the population of black rhinoceros in the study area.
Relationship between root and shoot growth traits during the plant crop and first ratoon in banana and plantain (Musa spp.) and its implications for perennial cultivation on degraded Ultisols in south-eastern Nigeria
(Journal of Applied Biosciences, 2008) Blomme, G.; Swennen, R.; Soka, G. E.; Turyagyenda, F. L.; Tenkouano, A.
Objective: This study assessed the relationships of root and shoot growth within and across two consecutive crop cycles in 32 widely differing Musa spp. genotypes. Methodology and results: A reduction in leaf area, corm weight, root dry weight, cord root number and length occurred during the reproductive stage of both the plant crop and the first ratoon cycle. Most leaves died off during the reproductive stage, while the decay of the outer leaf sheets resulted in a reduction of the pseudostem circumference. The corm fresh weight was reduced by 20 and 13 % during the reproductive stage of the first and the second cycle, respectively. A reduction in cord root number of 8 and 12 % was observed during the reproductive stage in the first and second cycle, respectively. Cord root length was reduced by 40 % during the reproductive phase of both cycles. The effect of crop cycle was significant on the different corm traits and the cord root diameter. The corm of the first ratoon plants was bigger and taller than the corm of the plant crop, resulting in a slight increase in number and diameter of cord roots. In contrast, cord root length of the first ratoon was less than that of the plant crop. Number of suckers decreased from 16 to 12, while height of the tallest sucker was 120 cm and 68 cm at flower emergence of the plant crop and the first ratoon crop, respectively. Significant positive correlations were observed between mother plant (plant crop) and sucker growth characteristics, mostly within but not across genotypes. Conclusion and application of findings: While fast-growing plants may also have better developed suckers, it is not apparent that breeding for genotypes with a larger root system would lead to better suckering. The observed reduction in sucker vigour during the reproductive phase of the ratoon crop may be attributed to the observed high mat and possible soil degradation. This would affect plant anchorage and stability, and limit possibilities for perennial production of bananas and plantains under mono-cropping conditions on degraded Ultisols.