Dwarf shrub ecology in Kenya's arid zone: Indigofera spinosa as a key forage resource

Abstract

Dwarf shrubs are a very important forage resource in Northwest Kenya and probably contribute to the stability of pastoral systems in that area. In an effort to learn more about the ecology of these species we measured their density, size, morphometric traits and relations, and responses to defoliation. These studies indicate that while dwarf shrub foliage is less abundant than grass, these plants can produce a significant quantity of palatable forage (8 g/m 2 /year) for the pastoral system, and the forage is available at critical times. The most abundant species, I. spinosa was patchily distributed, but production rates within patches were high (220 g/m 2 /year). A defoliation experiment indicated that I. spinosa was tolerant of herbivory. Defoliation also had little net effect on plant size because tissue mortality during a dry period resulted in greater tissue losses from larger undefoliated plants. Tolerance of herbivory and drought, ability to respond to little rainfall and preference for sandy soils indicated substantial value as a forage species in arid tropical regions.