中文摘要：

利用稳定同位素^13C技术，通过设置两种温度的恒温培养实验，研究了外源碳（^13C—Glucose）在土壤中的分配规律、以及土壤有机碳（SOC）、轻组有机碳（LFOC）和重组有机碳（HFOC）的分解速率．培养温度分别为15℃和25℃，培养时间为112d．结果表明：两个温度培养条件下，葡萄糖标记的^13C进入SOC、LFOC和HFOC的比例随着培养时间而呈递减趋势，培养结束时标记的^13C依然有18．9％～22．0％残留于土壤中．培养时段内，SOC的分解速率常数为4．4×10^-4～9．7×10^-4d^-1，HFOC的分解速率常数为3．4×10^-4．0×10^-4d^-1，而LFOC的分解速率常数介于1．1×10^-3～4．6×10^-3d^-1之间．总之，外源碳显著影响了人工杉木林土壤有机碳组分的分解速率．在有外源碳输入的条件下，升温加快了LFOC的分解，但抑制了HFOC的分解．因此．在供试土壤中．LFOC可能会比HFOC对全球变暖的响应更敏感．

英文摘要：

Decomposition rates of organic carbon fractions and their responses to exogenous carbon are important for forest carbon modeling. In this study, a laboratory incubation experiment was conducted to investigate the distribution of exogenous carbon （^13C-glucose） in soil fractions and the decomposition rates of organic carbon fractions using ^13C stable isotope technique. Soil collected from Chinese fir plantation, which was incubated at 15 ℃ or 25 ℃ for 112 days. The results showed that the ^13C remaining in bulk soil, light fraction and heavy fraction （as % of ^13C addition） decreased with incubation time, about 18.9% -22.0% of ^13C-labeled still remained in bulk soil after 112 days. The decomposition rates of SOC and HFOC and LFOC were estimated using first-order decay equation. The decomposition rate accounted for 4.4×10^-4～9.7×10^-4d^-1 for SOC, 3.4×10^-4.0×10^-4d^-1 for HFOC and 1.1×10^-3～4.6×10^-3d^-1 for LFOC. Exogenous car- bon significantly affected the decomposition rates of organic carbon fractions. Temperature increase stimulated the decomposition of LFOC, but suppressed the decomposition HFOC under exogenous carbon addition treatment. Therefore, the LFOC may be more sensitive to global warming than the HFOC in tested soil.