Effects of elevated carbon dioxide and nitrogen addition on foliar stoichiometry of nitrogen and phosphorus of five tree species in subtropical model forest ecosystems

Abstract

The effects of elevated carbon dioxide (CO2) and nitrogen (N) addition on foliar N and phosphorus (P) stoichiometry were investigated in five native tree species (four non-N2 fixers and one N2 fixer) in open-top chambers in southern China from 2005 to 2009. The high foliar N:P ratios induced by high foliar N and low foliar P indicate that plants may be more limited by P than by N. The changes in foliar N:P ratios were largely determined by P dynamics rather than N under both elevated CO2 and N addition. Foliar N:P ratios in the non-N2 fixers showed some negative responses to elevated CO2, while N addition reduced foliar N:P ratios in the N2 fixer. The results suggest that N addition would facilitate the N2 fixer rather than the non-N2 fixers to regulate the stoichiometric balance under elevated CO2.