Effects of phosphorus addition on leaf litter decomposition in two tropical tree plantations in Thailand

Abstract

There is a widespread belief that organic matter decomposition in phosphorus (P)-poor tropical forests is limited by P shortage and stimulated by exogenous P addition. An incubation experiment was performed to test the effect of P addition on decomposition of litter layers taken from two tropical tree plantations. The result was compared with our earlier soil incubation experiment in the same region. Contrary to the traditional view, we found no significant effects of P addition on the litter layer decomposition, which was also in contrast with our previous soil incubation experiment that showed stimulatory effects of P addition on soil microbial respiration. The difference between our two experiments was attributed to the role of added P to release organic matter from the sorption sites on mineral soils, which made the adsorbed organic matter in soil accessible for microbes and easier to be decomposed. Overall, our incubation experiments did not support the P-limitation hypothesis: organic matter decomposition in P-poor tropical forests is limited by P shortage.