Photosynthesis of subtropical forest species from different successional status in relation to foliar nutrients and phosphorus fractions

The ecophysiological linkages of leaf nutrients to photosynthesis in subtropical forests along succession remain elusive. We measured photosynthetic parameters (A(max), V-cmax, J(max), PPUE), leaf phosphorus (P) and nitrogen (N), foliar P fractions and LMA from 24 species (pioneer, generalist, and climax). A(max) was significantly related to N and P for the pooled data, while significant relationship between A(max) and P was only found in climax species. The mixed-effect model including variables (N, P, and SLA or LMA) for predicting V-cmax and J(max) best fitted but varied remarkably across succession. Climax species had higher N: P ratios, indicating an increasing P limitation at later succession stage; photosynthesis, however, did not show stronger P than N limitations across all species. Nevertheless, climax species appeared to increase nucleic acid P allocation and residual P utilization for growth, thereby reducing the overall demand for P. Our results indicate that the scaling of photosynthesis with other functional traits could not be uniform across succession, growth variables (e.g. photosynthesis) and species trait identity (e.g. successional strategy) should be considered in combination with N: P ratio when we investigate P limitation in subtropical forests, and variations in P allocation state further influencing photosynthetic rates and P-use efficiency.