Species Diversity Has a Positive Interrelationship with Aboveground Biomass and a Mismatch with Productivity in a Subtropical Broadleaf Forest on the Wuyi Mountains, China

The Wuyi Mountains in China are one of the largest and most complete subtropical forest ecosystems at the same latitude in the world. However, our limited understanding of the function of this distinctive ecosystem means that the interrelationship between species diversity and ecosystem functioning needs to be investigated if evergreen broadleaf forests (EBLFs) are to be protected. Here, we calculated species richness, the Shannon–Wiener index, and the Pielou index in large-, medium-, and small-scale (20 m × 20 m, 10 m × 10 m, and 5 m × 5 m) forest dynamics plots (FDPs). We also investigated the interrelationships between species diversity and aboveground biomass (AGB)/productivity in FDPs at the different scales using the generalized linear regression model. The results showed that species diversity and AGB positively interrelated with each other, whereas there was no species diversity-productivity interrelationship in the subtropical BLF on the Wuyi Mountains. The structural equation model (SEM) showed that elevation was a key factor directly affecting AGB. These findings lead to the conclusion that productivity is not solely correlated with species diversity and that abiotic factors probably mediate the positive interrelationship between species diversity and ecosystem functioning. This study provides theoretical basis that can be used to protect EBLFs in subtropical areas and the results can be used to improve the construction of artificial forest communities and vegetation restoration at the same latitude.