Wet tropical forests play a critical role in global ecosystem carbon (C) cycle, but C allocation and the response of different C pools to nutrient addition in these forests remain poorly understood. We measured soil organic carbon (SOC), litterfall, root biomass, microbial biomass and soil physical and chemical properties in a wet tropical forest from May 1996 to July 1997 following a 7-year continuous fertilization. We found that although there was no significant difference in total SOC in the top 0–10cm of the soils between the fertilization plots (5.42
0.18 kgm2) and the control plots (5.27
0.22 kgm2), the proportion of the heavy-fraction organic C in the total SOC was significantly higher in the fertilized plots (59%) than in the control plots (46%) (Po0.05). The annual decomposition rate of fertilized leaf litter was 13% higher than that of the control leaf litter.We also found that fertilization significantly increased microbial biomass (fungi1bacteria) with 952
48mgkg1soil in the fertilized plots and 755
37mgkg1soil in the control plots. Our results suggest that fertilization in tropical forests may enhance long-term C sequestration in the soils of tropical wet forests.