Environmental, structural, and taxonomic diversity factors drive aboveground carbon stocks in semi-deciduous tropical rainforest strata in Cameroon

Summary

Forest stratification plays a crucial role in the interception of light and plants' photosynthetic activities. However, there is still a lack of information on the contribution of tropical forest stratification to its functioning, despite the increasing number of studies. Here, we analysed from a perspective of the whole tree community (WTC) and forest strata (i.e., large trees, understory trees, and small stems), the relationship between abiotic, biotic factors and aboveground Carbon (AGC). The abiotic factors-AGC relationships were positive for all strata and WTC. However, soil factors-AGC relationship was stronger for small stems and understorey, while topography factor-AGC relationship was stronger for large trees and WTC. Tree size inequality-AGC relationship was positive and much stronger for WTC, large trees and small stems. In addition, a species diversity-AGC relationship was found positive only for large trees and WTC. These results highlight the niche complementarity effect for driving positive relationships of species diversity and individual tree size variation with aboveground biomass at large tree strata and WTC. The lack of positive effect of species diversity on AGC for understorey and small stems strata might be attributable to the selection effect or resource complementarity among species.