Diversity and local uses of woody vegetation in mined arid and semi-arid lands of Kimwarer, Kerio Valley, Kenya

Abstract

The woody vegetation in arid and semi-arid area is of immense importance performing a myriad of ecosystem services and providing a wide array of goods. However, the woody vegetation is threatened by both natural and anthropogenic activities at global, national and local levels. In Kerio Valley, the threat is manifested in the form of overexploitation for fuel wood and land-use change due to mining activities. This study aimed to assess the effects of mining activities on the composition, diversity and local utilization of woody vegetation in Kerio valley, located in Baringo County. The composition of woody vegetation, its abundance and diversity was compared between rehabilitated mined sites and sites that had not experienced human disturbance. The study was conducted between the months of October 2014 and May 2015 and six transects were established within two blocks separated by Kerio river. Each transect contained five plots measuring 20m by 20m. In each of the plots, data was collected on woody tree growth characteristics, seedling regeneration, tree form quality and soil phyto-sociological parameters. Indigenous knowledge on usage of the woody vegetation was captured using a questionnaire. Thirteen woody vegetation species were encountered in the rehabilitated mined sites with Ficus sycomorus being the dominant (22.1%) and Teclea nobilis the least dominant species (1.0%). Twenty two species were encountered in undisturbed sites with Ficus sycomorus as the dominant (15.5%) and Euclea divinorum being the least dominant (0.7%). Woody vegetation diversity was higher in undisturbed site than in the rehabilitated mined site. However, this variability in species diversity was not significant (T-test, =D.F=1 P=0.767). Among the phyto-sociological parameters measured, there was significant difference in the mean soil temperature (F2, 7. =9.08, P=0.011), pH (F2, 7. =109.88, P<0.01), and soil nutrients (F2, 7. = P<0.05) between the three sites (rehabilitated mined, undisturbed and recently mined). Majority of the respondent identified Combretum molle as the most common woody vegetation while Balanites aegyptiaca was noted as the woody vegetation commonly used but highly threatened by mining activities. Rehabilitating mined sites can bring back species diversity, however what is not clear is whether ecosystem functions are restored. Indigenous uses of woody trees necessitate the need for reforestation of mined sites.