Arid land agroforestry practices: their role in resource conservation and management in the Daua valley, Mandera District, Kenya

Abstract

Agroforestry is a traditional practice in the Daua Valley, Mandera District and yet very little effort has been made to document it. This problem has contributed to a significant gap in knowledge resulting in retarded development of improved agroforestry technologies for the area. Consequently, little is known of the useful woody components of the Valley and their habitats which is of crucial importance as increase in livestock and human population combined with change in the way of life is causing their erosion. Furthermore, the indigenous knowledge of the farmers and pastoralists have recieved little attention in the planning process and development of land use strategies by development agencies. The implication of the above constraints is that the use of this valley's land and vegetation resources without adequate knowledge may subject their continued use to abuse by the indigenous population, refugees as well as development agencies. One of the strategies for vegetation conservation in the area lies with the documentation of the knowledge of the user groups in retaining or/and planting useful trees and shrubs in farms and pastures. The study was conducted to understand the relationship between the existing agroforestry practices and vegetation conservation and how the resources vary with landscape characteristics in order to develop resource data base for the Daua Valley. The study was undertaken by carrying out reconnaissance and farm surveys and line transects (5 km each in a 75 km2 area) in Rhamu/Ashabito and Central/Khalaliyo Divisions, respectively. The bio-physical and socio-economic parameters (soil, gradient, vegetation species and their distribution and land use practices) were taken in the field. Soil samples were collected for further analysis for physical and chemical properties. The distribution of woedy vegetation was compared to landscape characteristics (using multiple regression) and the agroforestry practices. The study also examined the general condition of the vegetation using normalized difference vegetation index and the method of important value index was employed to determine the dominant indigenous species. Further details regarding the utilization of the local species were obtained from parata;xonomists (local experts), farmers and pastoralists. The vegetation distribution trend is strongly influenced by topography The uplands, midlands and lowlands were mainly covered by deciduous vegetation except for evergreen riparian woodlands along the river. The study further :1oted that 13 agroforestry practices were dominant in the valley. Generally silvopastoral practices of agroforestry were common. However in the area immediately bordering the river, multipurpose trees and shrubs for river bank stabilization and horticultural trees in farmlands were popular. The study also established that traditional agroforestry practices had more ~ies diversity and better vegetation cover than the introduced ones. Over 100 species identified provided productive and protective uses and their distribution within the vaHey was affected by the combined factors of human influence and landscape characteristics of slope gradient and soil physical and chemical properties. The ecologically and economically important species within the valley were mainly Thespesia danis, Hyphaene compressa, Lawsonia inermis, Mangifera indica, Psidillm gllajava and Acacia seyal in the lowlands; Acacia refeciens, Cordia qllercifolia and Boswellia neglecta in the midlands and uplands. Finally, this study would like to emphasize the importance of involving the local people and utilizing their knowledge particularly in the process of developing improved land use practices through the use of agroforestry technologies for soiL water and vegetation conservation.