Abstract: Xishuangbanna tropical rain forest (XTRF) is the most intact, typical and largest area of tropical rainforest ecosystem in China. We examined the effects of phosphorus addition on the concentration and stoichiometry of soil carbon (C), nitrogen (N), and phosphorus (P) in XTRF in four sites. The results showed that soil N and P in XTRF were more susceptible to exogenousP input. There were significant differences in C∶P and N∶P between the forest in Botanical〖JP〗 Garden and those forests in Yaoquxiang, Shangyong and Naban River region. Under P addition, soil nutrients and ecological stoichiometry varied greatly across the four sites due to differences in altitude, hydrothermal and climatic conditions, and microbial activity. Under exogenous P input, soil available P and vegetation’s ability to absorb P  increased in low altitude sites, resulting in elevated N∶P in soil, implying P limitation in ecosystems. However, N absorption and P release of plants, litters and microorganisms increased in high altitude sites, with decreased N∶P in soil, indicating that ecosystems may change into N limitation.

Key words: phosphorus addition, tropical rainforest, ecological stoichiometry, Xishuangbanna.