Harvesting distance effect on tree species diversity in traditional agroforestry landscape: a case of Vhembe Biosphere Reserve in South Africa

Abstract

Traditional agroforestry has been recognised to contribute to biodiversity conservation; however, biodiversity strategies often lack information about drivers of tree species diversity loss, which is crucial for decision-making. Anthropogenic disturbance has positive and negative effects on tree species richness and diversity. This study was conducted in Vhembe Biosphere Reserve, Limpopo Province, and used distance from the nucleus of the community to the forest as a parameter to assess tree species richness and diversity. Vegetation data were collected using three transects of 150 m in each distance level and sampled a total area of 1000 m2 by sampling five rectangular plots of 20 m2 × 10 m2 (200 m2). Data analysis was conducted using Chao1, PERMANOVA, nMDS, PERMDISP, DISTLIM, dbRDA and SIMPER. The findings are in consonant with distance decay of community similarity hypotheses, with estimated tree species richness of 76, 93 and 95 species in an immediate distance, intermediate distance and far distance, respectively. Moreover, the highest species variation was observed at an intermediate distance, which indicates that there is greater species composition at an intermediate distance compared to immediate and far distances. The results confirm that the distance and associated factors have major detrimental effects on tree species richness and biodiversity in traditional agroforestry landscapes. Harvesting of provisioning ecosystem services is found and known to be extremely high in the study area. Effective interventions such as planting indigenous trees and conserving the existing vegetation must be implemented to reduce and halt overexploitation.