Abstract: To understand the effects of nitrogen (N) and phosphate (P) fertilization on different fractions of labile soil organic carbon (SOC) in mid-subtropical forests, an experiment was conducted in Cunninghamia lanceolata plantations with treatments of N (200 kg N·hm^-2·a^-1),P (50 kg P·hm^-2·a^-1), NP (200 kg N·hm^-2·a^-1 plus 50 kg P·hm^-2·a^-1) and the control without fertilization (CK). Different fractions of labile SOC were measured after five years of fertilization. Fertilization had no significant effects on SOC concentration. In comparison with CK, the microbial biomass carbon was decreased by 34.6% and 45.8% in N and NP treatments respectively. Nitrogen fertilization decreased the WSOC concentration. Furthermore, the HWC concentration was significantly increased by 31.5% in N treatment. MBC/SOC decreased by 48.4% in NP treatment. The POC/SOC significantly increased by 24.3% in NP fertilized plots compared with N fertilized plots. HWC was significantly positively correlated to nitrate and available P concentrations.

Key words: exogenous 6-BA, yield, shading, rice stubble wheat