Differential effects of N and P additions on foliar stoichiometry between species and community levels in a subtropical forest in eastern China

The responses of foliar nitrogen (N) and phosphorus (P) stoichiometry to nutrient additions are important indicators of various ecological processes, especially under climate change. However, how nutrient additions affect foliar N and P stoichiometry from species to community levels remain unclear, especially in P-limited systems. In this study, we conducted a nutrient additions experiment with control, N addition, P addition, and NP addition treatments in a P-limited subtropical forest to examine the effects of nutrient additions on foliar N and P stoichiometry. Our results showed that nutrient additions did not significantly influence foliar N concentration in seven dominant plant species over a three-year experimental period but significantly increased foliar P concentration and decreased foliar N:P ratio in species with lower initial foliar P concentration. The interactive effects of N and P additions on foliar P concentration and N:P ratio were synergistic and antagonistic, respectively. The response ratio of foliar P concentration to nutrient addition had a significantly negative correlation with initial foliar P concentration (r = −0.644), but had a positive one with initial foliar N:P ratio (r = 0.619). These results suggest that the limiting P dominated the responses of foliar N and P stoichiometry to nutrient additions at species level. At the community level, foliar P concentration and N:P ratio for both community weighted means (CWM) and community non-weighted means (CM) showed weaker positive responses to N and P additions than those at species level and there was no differential response between CWM and CM, suggesting the control of varied species responses on community foliar P concentration and N:P ratio response. Taken together, our results highlight the differential impacts of nutrient additions on foliar N and P stoichiometry between species and community levels, which needs to be considered in models when assessing the responses of ecosystem function to nutrient enrichments.