Habitat Conditions in a Continuously Grazed Wildlife Sanctuary in Kenya

Abstract

Changes in structure and composition of herbaceous vegetation in rangelands often result from effects of continuous grazing by large herbivores. The structure and composition of herbaceous vegetation were assessed in various vegetation types in Kimana Wildlife Sanctuary. Data were collected using Stratified sampling method, Line transect method, Quadrat method, Disc Pasture Meter method and Descending Step Point method. The study recorded a total of eight grass species belonging to three ecological categories, namely; decreaser, increaser I and increaser II. Frequency distribution of the ecological categories of grasses differed significantly across the vegetation types, with the exception of Sporobolus fimbriatus grassland and Acacia xanthophloea woodland, which were exclusively dominated by S. fimbriatus Nees ex Trin grass. Increaser II species; Cynodon dactylon L., S. fimbriatus Nees ex Trin and Harpachne schimperi Hoschst dominated in all the vegetation types, except for wooded grassland, which was dominated by Pennisetum stramineum Peter, an increaser I species. Cenchrus ciliaris L. occurred at low frequencies (< 50%) in wooded grassland and C. ciliaris grassland. Grass standing crop, grass basal cover, grass height and inter-tuft distance between grass swards also varied across the vegetation types. All the vegetation types, except wooded grassland indicated conditions of over-utilization. Wooded grassland indicated conditions of under-utilization. We suggested restoration of vegetation types dominated by increaser species through reseeding using increaser species such as Cenchrus ciliaris L., Themada triandra and Penicum maximum. We also suggested monitoring of occurrences and distribution of Cenchrus ciliaris L. species and other native decreaser species in Amboseli ecosystem and in similar ecosystems in Kenya.

Keywords: Continuous grazing, Grass species, Ecological categories, Vegetation types, Kenya