Plant diversity and species turnover co-regulate soil nitrogen and phosphorus availability in Dinghushan forests, southern China

The interaction between plants and soil is an important internal driver of ecosystem evolution. Many studies have reported the unidirectional effects of soil nutrients on plant diversity and species turnover. However, there are still many gaps in our knowledge about how plant diversity and species turnover feedback to soil nutrients. In the present study, three forest plots with different species composition and diversity were created through artificial disturbance in the same stand origin forest, and their long-term dynamics were observed. We identified underlying mechanisms of how plant diversity (Shannon-Wiener index) and species turnover (Bray-Curtis dissimilarity) affect soil total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), and available phosphorus (AP). Plant diversity was associated with soil TN, TP, AN, and AP concentrations (P < 0.01). Species turnover was negatively correlated with the log-response ratio of TP (LRR TP) (P < 0.001), but not correlated with LRR AP. Species turnover had significant positive correlations with LRR TN and LRR AN (P < 0.001). The structural equation model supports hypotheses that plant diversity and species turnover influenced soil N and P availability by affecting forest community growth (total tree basal area, TBA), litter quantity and quality, and soil physical and chemical properties (soil organic carbon, SOC; soil exchangeable base cations). Collectively, our results highlighted the co-regulation of plant diversity and species turnover on soil N and P availability by “complementary” and “mass” effects during the long-term dynamics of forest ecosystems.