Effects of nitrogen and phosphorus addition on leaf nutrient characteristics in a subtropical forest

Abstract

P deposition can alleviate P limitation in subtropical forests and P deposited in conjunction with high quantities of N does not enhance P limitation. Increasing nitrogen (N) and phosphorus (P) deposition could influence plant growth and survival to varying extents. N and P deposition is essential for subtropical forests where plant growth is limited by lower soil P availability in highly weathered soils. However, whether N and P deposition can increase leaf P concentration and alleviate P limitation is unclear. We investigated changes in N and P concentrations, N:P ratios, and resorption for six dominant species (two tree species and four understory species), following 2 years of N and P additions in a subtropical forest in southern China. P addition either alone or together with the addition of N increased green leaf P concentrations (except in Schima superba) and senesced leaf P and decreased N:P ratios (except in Pinus massoniana), but had no influence on P resorption. N addition had no apparent influence on leaf N concentrations, N:P ratios, or N resorption in all species. The considerable influence of P addition can be explained by rising soil P availability. Our results suggest that subtropical forests are P limited and that increasing P deposition can moderately alleviate the limitation of P. Furthermore, P deposited in conjunction with high quantities of N does not enhance P limitation, as it is insensitive to elevated N input.