Interface of biodiversity and ecosystem services: Does soil organic carbon correlate with the diversity of carabid beetles (Coleoptera: Carabidae) in the Uzungwa Scarp Nature Reserve, Tanzania?

Tropical forest soils have potential to mitigate climate change and support biodiversity. Human activities in these forests threaten biodiversity and alter the ability of the soil to sequester carbon. Many tropical countries experience rampant anthropogenic activities in the forests, yet the extent to which these activities affect biodiversity and soil organic carbon and the relationship between the two is not well studied. In this study, the correlation of soil organic carbon (SOC) and ground beetles was assessed in both control and disturbed sites in Uzungwa Scarp Nature Reserve (USNR). Disturbance activities included logging for timber, tool handles and building poles; fire, hunting, footpaths, collection of fuel wood, and clearing for agriculture. Pitfall trapping, active searching during the day, and active night searching were methods used to collect the ground beetles. Soil samples were collected at three depths 0-15, 15-30 and 30-45 cm in twelve plots: six in disturbed and six in control sites. A total of 890 ground beetles comprising 30 species were collected. The species richness of carabid beetles was high in the control sites (26 species) and low in disturbed site (16 species), with the respective Shannon-Wiener being Hꞌ= 2.103 and Hꞌ = 1.327. The difference in species diversity was statistically significant. Abundance of carabid beetles was also significantly higher in control sites compared to disturbed sites. Mean SOC was low in disturbed sites and high in control sites at all three depths. In disturbed sites, the correlation between SOC and species richness was weakly negative but not significant, and positively correlated with abundance, though it was not statistically significant. In control sites, there was a significant positive correlation between SOC and carabid abundance, but not with species richness of carabid beetles. To conclude, protection of natural forests is prerequisite for biodiversity and ecosystem services. We recommend that management improvement is urgently required, because ongoing human activities seem to contribute to diminished SOC stock.   Key words: Soil organic carbon, disturbance, ground beetles, correlation.