Effects of elevated temperature and doubling of CO_2 concentration on the soil microbial community structure in the subalpine coniferous forest of western Sichuan, China
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 CO_2 concentration (EC) on soil microbial community structure in the subalpine coniferous forest of western Sichuan, C hina. The results showed that the total PLFAs contents in EC, ET and the combined treatment (ETC) were significantly decreased by 47.8%, 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 cont rol. However, ET showed no s ignificant 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 an d mycorrhiza from that of the control plots. In summ ary, elevated temperature, doubled CO_2 concentration and their combination may change the structure of the microbial community, with the combination of elevated temperature and doubled CO_2 concentration most effective.