Edward Mengich

PhD project


Responses of common semi-arid savanna tree and shrub species to soil water status and their potential as criteria for species selection in Makueni district of Kenya (funded by DAAD)

Recent increases in semi-arid savanna zone human populations have led to increased pressure on land productivity and resources, and disrupted the ecological balance that has evolved over a long period of time. Deforestation, soil erosion, loss of biodiversity and land degradation have occurred, threatening the resource base for both current and future generations. In order to reverse the adverse effects of these changes, the government of Kenya has, among other strategies, implemented forestry research and development programmes. However, little success has so far been achieved due to use of mainly exotic tree and shrub species, which are poorly adapted to the water stress conditions of these areas. Naturally occurring tree and shrub species possess survival traits that have enabled them to adapt to these conditions. Unfortunately, their potential cannot be fully exploited for purposes of improving species selection and tree planting because their eco-physiological responses to moisture stress have not been studied and documented adequately, and are not well understood. Through multi-site and seasonal studies, the proposed study will document the responses of plant water relations and photosynthesis in selected tree and shrub species to soil water status in the semi-arid savanna south east of Nairobi in Makueni district. Using vegetation and agro-ecological maps and Landsat imageries, the study sites will be identified in each of the 3 agro-ecological zones of the district. With the help of complementary field surveys, commonly occurring evergreen tree and shrub species of both indigenous and exotic origin will be identified according to these sites and agro-ecological zones. Physiological and growth data will be collected for a period of 1 year. With the help of Excel and M-stat software, the data collected will be used to compute various descriptive statistics and statistical inferences for purposes of predicting adaptive characteristics, vegetation structure and dynamic processes. The study will document well-adapted tree and shrub species, highlight their characteristic responses to varying moisture conditions, propose strategies for improved species selection, and make recommendations for future tree planting in savanna and rangeland areas. The findings of the proposed study will benefit farmers, pastoralists, research and academic institutions, and development agencies working under similar circumstances both in Kenya and abroad.


Advisors

Dr. Daniel K. Too (Department of Natural Resources, Egerton University, Kenya)
Prof. Joseph M. Macharia (Department of Botany, Egerton University, Kenya)
Prof. Dr. R. Mitlöhner (Institute of Silviculture/Dept. of Tropical Silviculture, University of Göttingen)