Influence of elevation gradient and plant species composition on soil organic carbon in Mount Rungwe Forest Reserve, Tanzania

This study was conducted at Mount Rungwe Forest Reserve, Mbeya, Tanzania, East Africa to investigate the influence of elevation gradients and vegetation composition on soil organic carbon. Elevation gradients were established through three elevation grids, the higher, mid and lower elevation. We hypothesized that soil organic carbon would be richer in high plant diversity than in low plant diversity gradients. Findings from this study observed that, low elevation had high moisture content (47.72 +/- 1.49) and % soil organic carbon (4.02 +/- 0.56) with low bulk density (1.03 +/- 0.001) and soil pH (5.96 +/- 0.06). However, only moisture content, bulk density, organic matter and sand content were statistically different across elevation gradients. It was also observed the proportional decreases in diversity as elevation increases with both Shannon and Simpson index of diversity indicating higher species diversity at lower elevations (3.62 and 0.03 respectively). Results from two multiple linear regression models indicated that moisture contents, plant abundance and species diversity explained the most variation in soil organic matter across an elevation gradient with R-2 = 0.4063, F (3, 38) = 8.67, p = 0.0002 and R-2 = 0.3510, F (2, 39) = 10.55, p < 0.0001 for model 1 (tree abundance) and model 2 (tree diversity) respectively.