中文摘要：

选择亚热带地区3种典型稻田和旱地土壤，应用碳同位素14C-CO2标记示踪技术结合室内模拟培养试验，研究自养微生物同化碳（“新碳”）在土壤碳库中的矿化和转化特征．结果表明：在100d的培养期内，“新碳”的矿化经历了先上升、10d后缓慢下降、最后渐趋稳定的3个阶段．“新碳”的矿化比例为8．0％～26．9％，矿化速率为0．01～0．22μg 14C·g^-1·d^-1，其中，稻田土壤为0．01～0．22μg 14C·g^-1·d^-1，旱地土壤为0．01～0．08μg 14C·g^-1·d^-1，而原有有机碳的矿化比例为1．6％～5．7％，矿化速率为1．3—25．66μg C·g^-1·d^-1．土壤活性碳库[可溶性有机碳（DOC）、微生物生物量碳（MBC）]中，14C-DOC在培养初期（0—10d）先上升，升高幅度达0．3mg·kg^-1，10～30d又迅速下降，下降幅度达0．42mg·kg^-1，至30d后缓慢下降．14C—MBC的波动与 14C—DOC不同，在培养初期（0～10d）先迅速下降，10～30d又迅速上升，至40d后缓慢下降并趋于稳定．水稻土 14C—DOC／DOC的转化更新速率明显大于旱地，而旱地 14C—MBC／MBC的转化更新速率大于水稻土．

英文摘要：

In this study, the mineralization and decomposition of autotrophic microbe assimilated carbon （new carbon） and native organic carbon in three upland and three paddy soils in subtropical China were measured using the 14C-labelled tracer technique. The results showed that, during the 100-d incubation, the mineralization of the ‘ new carbon＇ displayed three stages ： a rise in the first 0.01 to 0.22 μg 14C · g^-1 · d^-1（0.01-0.22 μg 14C· g^-1 · d^-1 in paddy soils and 0.01-0.08 μg 14C · g^-1 · d^-1 in upland soils）. However, the mineralization ratio and rate for native SOC were 1.55%-5.74% and 1.3-25.66 μg C · g^-1 ·d^-1, respectively. In the soil active C pools, the 14C-dissolved organic carbon （DOC） first rose by as much as 0.3 mg· kg^-1 in the early stages of incubation （0-10 d）, decreased rapidly by 0.42 mg · kg^-1 from 10-30 d, and then declined grad- ually. The fluctuation of the 14C-microbial biomass carbon （ MBC ） differed from that of the 14C- DOC. At the beginning stage of the incubation （0-10 d）, the 14C-MBC decreased rapidly, and then rapidly increased from 10 to 30 d, and the rate of increase reduced and was gradually stabi- lized after 40 d. The 14C-DOC/DOC renewal rate in the paddy soil was significantly higher than inthe upland soil while the 14C-MBC/MBC renewal rate in the upland soil was significantly greater than in the paddy soil.