Soil heterotrophic respiration(HR)was investigated in one tract of native Castanopsis kawakamii forest(NF), a 33-year-old Castanopsis kawakamii plantation(CK)and a Cunninghamia lanceolata(Chinese fir,CF)plantation of the same age in Sanming,Fujian Province,China.Soil CO₂ efflux was measured in situ in a 2-year period with the alkali sorption technique.Respirations of root-free soils(R_RF)and litter layer(RL)were measured separately by trenching and removing litter, respectively.Both R_RF and R_L in the three forests showed a similar seasonal pattern with o ne single peak occurring during May or June and a valley during December or January.R_L averaged CO₂ 79188,44137 and 21102 mg m^-2 h^-1,and R_RF averaged CO₂ 21714,85185 and 94104 mg m^-2 h^-1 in NF,CK and CF,respectively.The model R=ae^bTW^c (R stands for soil CO₂ efflux, T for soil temperature and W for soil water content at 0~10 cm soil depth,and a,b,c for the constants)indicated that soil temperature and soil water content together could explain 82%~85% and 85%~92% of R_L and R_RF,respectively,with soil temperature being the dominating factor affecting soil respiration rate in 2002 and soil humidity in a dry year of 2003.R_L was more sensitive to variation in soil temperature and humidity than R_RF.Annual R_L averaged C 3176,2163 and 1123 t hm^-2 a^-1, and annual R_RF averaged C 3144,2179 and 1149 t hm^-2 a^-1,respectively,in the NF,CK,and CF.Differences in soil heterotrophic respiration between forests were associated with differences in quantity and quality of organic inputs,biomass and activity of roots,and content and components of soil organic carbon.R_L in CF showed higher sensitivity to drought than in CK and NF,and the sensitivity of soil organic C to drought was higher in the plantations(CK and CF)than in the native forest (NF).