Deposition of atmospheric N and P and enrichment of CO2 concentration may increase soil nutrient availability and C input through litterfall and roots.We performed an experiment in which Pinus massoniana and Michelia macclurei litter labeled by 13C and inorganic nutrients were added individually or together to soil collected from a forest in tropical China.The aim of the experiment was to investigate the effect of C addition and nutrient availability on the decomposition of native SOC.The production of CO2 was measured continuously over the succeeding 120 days during laboratory incubation.P.massoniana and M.macclurei litter additions dramatically increased total CO2 production and caused a significant positive priming effect of 7.4%and 22.4%,respectively.Inorganic N and P additions suppressed soil respiration by 6.6%and 7.1%,respectively,when added individually.After the 120-d incubation period,inorganic N addition resulted in a higher decrease in the priming effect induced by P.massoniana and M.macclurei litter compared with P addition.These results suggest that mcreases in soil nutrient availability from atmospheric N and P deposition can reduce the decomposition of SOC and increase soil C deposits in subtropical forests potentially the most vulnerable.