中文摘要：

土壤是陆地生态系统中最主要的碳库,土壤微生物是土壤的重要组成部分,其群落结构对全球变化十分敏感,研究气候变化背景下土壤微生物群落结构的变化对于预测陆地生态系统净碳平衡有着重要的作用.通过全自动微气候控制的＂人工模拟气候实验系统＂对川西亚高山针叶林土壤进行模拟增温（ET）、CO_2浓度加倍（EC）以及增温~＋CO_2浓度加倍（ETC）处理,采用磷脂脂肪酸法（Phospholipid fatty acids,PLFAs）研究ET、EC及ETC对土壤中微生物群落结构的影响,结果表明：（1）与对照相比,ETC、EC、ET均使总磷脂脂肪酸含量显著降低,降低幅度分别为52.8%、47.8%、31.3%.（2）ETC、EC和ET均使细菌、真菌、革兰氏阴性菌（G^-）的PLFAs含量显著降低（P〈0.01）,ETC的降幅大于EC和ET;ETC、EC显著降低了革兰氏阳性菌（G^＋）的PLFAs含量,但ET对G^＋的PLFAs含量没有显著影响.（3）ETC使G^＋/G^-比值显著升高,使真菌/细菌比值显著降低,但EC、ET对G^＋/G^-、真菌/细菌比值没有显著影响;同时,ETC、EC、ET对放线菌和菌根真菌的PLFAs含量均没有显著影响.本研究表明,ETC、EC、ET处理均能使土壤微生物群落结构发生变化,并且ETC对土壤微生物群落结构的影响大于单独的ET或EC.

英文摘要：

Soil is the major carbon pool of the terrestrial ecosystem.Soil microbes play an important role in the soil system.Moreover,the structure of microbial community is sensitive to climate change,so it is crucial to predict the net carbon balance of terrestrial ecosystem.By using a fully automated microclimate-controlled artificial climate simulation system and phospholipid fatty acids（PLFAs） method,this research studied the effects of elevated temperature（ET） and doubled CO2concentration（EC） on soil microbial community structure in the subalpine coniferous forest of western Sichuan,China.The results showed that the total PLFAs contents in EC,ET and the combined treatment（ETC） were significantly decreased by47.8%,31.3%and 52.8%,respectively.The ETC,EC and ET treatments all had significantly decreased PLFAs contents of bacteria,fungi and gram-negative,with the degree of reduction in ETC treatment greater than that in the other two treatments.The PLFAs contents of gram-positive bacteria in ETC and EC treatments were lower than in the control.However,ET showed no significant effects on gram-positive bacteria.In addition,as compared with that of the control,the ratio of gram-positive to gram-negative bacteria（G^＋/G^-） and the ratio of fungi to bacteria were decreased by ETC treatment,but not affected by EC or ET treatment.Moreover,none of the treatment groups showed significant difference in the PLFAs contents of actinomycetes and mycorrhiza from that of the control plots.In summary,elevated temperature,doubled CO2 concentration and their combination may change the structure of the microbial community,with the combination of elevated temperature and doubled CO2 concentration most effective.