The soil resources of Ruma national park in Lambwe Valley, Kenya.

Abstract

Soils are important components of the environment and their understanding is essential in planning and management for environmental conservation and sustainable use of natural resources. However, reliable soil information required for longterm conservation and development planning is scarce, particularly for wildlife protected areas. A semi-detailed soil survey of Ruma National Park was conducted with the principal objectives of identifying, describing, mapping and interpreting the soil information with respect to planning and management of the environment and wildlife conservation. The survey provides information on the park's major soil types, their distribution and gives a broad estimate of soil erosion susceptibility and soil limitations to establishment of public facilities in the park. A soil map at a scale of 1:50,000 is presented, while the results of the estimated soil erosion susceptibility and soil limitations to public recreation facilities are presented in tables. The results were based on air photo interpretation, fieldwork and laboratory soil testing. The results show that the park is dominated by poorly drained, calcareous, black cracking clay soils developed on sedimentary materials derived from volcanic rocks deposited in previous basin. The distribution pattern of the soils closely parallel that of physiography. Four ma jor physiographic units containing ten soil mapping units were identified. Each mapping unit described was evaluated for susceptibility to soil erosion and soil limitations to recreational facilities. Calcareous Vertisols on the flat piedmont plains and valley bottom plains are dominant. Shallow Leptosols occur on the volcanic hills and escarpments while brown clay Cambisols occur in the footslopes. The natural soil fertility is generally high in all the soils but with very high available calcium and magnesium content. Soil erosion susceptibility was evaluated using a qualitative method based on climate, topography and soil erodibility The results predicted low erosion susceptibility for the soils of the hills and scarps, and very low susceptibility for the rest of the soils. Field evidence showed that soil erosion is currently not a serious problem in the park. This may be attributed to the predominance of flat terrain and good vegetation cover during most part of the year. Moderate erosion occur in the skeletal soils of the hills and scarps, where minor gullies are associated with primary drainage lines. However, severe erosion occur on the cultivated foots 1opes adjacent to the park, which require immediate conservation measures. The soils of the footslopes were found to be the most suitable for establishment of campsites and walking trails in the park. The evaluation was based on soil depth, drainage, erodibility, slope and soil surface stoniness. Out of 12,000 hectares of the park 13% have severe limitations, 68% have moderate and about 19% have slight limitations for campsites and walking trails. The areas with severe limitations largely consist of the hills and the scarps with shallow soils. The predominance of poorly drained, calcareous, sodic seasonally waterlogged clay soils make the park an excellent area for wildlife conservation since the area cannot be used economically for arable land use. The infancy stage of the infrastructure and facility development in the park provides a unique opportunity to utilize this soil information in the planning for sustainable use and conservation.