CAS Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100101, China.
CAS Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100101, China.
Sci Total Environ. 2021 Apr 10;764:142848. doi: 10.1016/j.scitotenv.2020.142848. Epub 2020 Oct 9.
High amounts of deposited nitrogen (N) dramatically influence the stability and functions of alpine ecosystems by changing soil microbial community functions, but the mechanism is still unclear. To investigate the impacts of increased N deposition on microbial community functions, a 2-year multilevel N addition (0, 10, 20, 40, 80 and 160 kg N ha year) field experiment was set up in an alpine steppe on the Tibetan Plateau. Soil microbial functional genes (GeoChip 4.6), together with soil enzyme activity, soil organic compounds and environmental variables, were used to explore the response of microbial community functions to N additions. The results showed that the N addition rate of 40 kg N ha year was the critical value for soil microbial functional genes in this alpine steppe. A small amount of added N (≤40 kg N ha year) had no significant effects on the abundance of microbial functional genes, while high amounts of added N (>40 kg N ha year) significantly increased the abundance of soil organic carbon degradation genes. Additionally, the abundance of microbial functional genes associated with NH, including ammonification, N fixation and assimilatory nitrate reduction pathways, was significantly increased under high N additions. Further, high N additions also increased soil organic phosphorus utilization, which was indicated by the increase in the abundance of phytase genes and alkaline phosphatase activity. Plant richness, soil NO/NH and WSOC/WSON were significantly correlated with the abundance of microbial functional genes, which drove the changes in microbial community functions under N additions. These findings help us to predict that increased N deposition in the future may alter soil microbial functional structure, which will lead to changes in microbially-mediated biogeochemical dynamics in alpine steppes on the Tibetan Plateau and will have extraordinary impacts on microbial C, N and P cycles.
大量氮（N）的沉积通过改变土壤微生物群落功能，显著影响高寒生态系统的稳定性和功能，但其中的机制尚不清楚。为了研究增加氮沉降对微生物群落功能的影响，在青藏高原高寒草原上进行了一项为期 2 年的多水平氮添加（0、10、20、40、80 和 160 kg N ha year）野外实验。利用土壤微生物功能基因（GeoChip 4.6）、土壤酶活性、土壤有机化合物和环境变量，探讨了微生物群落功能对氮添加的响应。结果表明，40 kg N ha year 的氮添加率是该高寒草原土壤微生物功能基因的临界点。少量添加氮（≤40 kg N ha year）对微生物功能基因丰度没有显著影响，而大量添加氮（>40 kg N ha year）显著增加了土壤有机碳降解基因的丰度。此外，与 NH 相关的微生物功能基因（包括氨化、固氮和同化硝酸盐还原途径）的丰度在高氮添加下显著增加。进一步，高氮添加还增加了土壤有机磷的利用，这表现为植酸酶基因丰度和碱性磷酸酶活性的增加。植物丰富度、土壤 NO/NH 和 WSOC/WSON 与微生物功能基因的丰度显著相关，这驱动了氮添加下微生物群落功能的变化。这些发现有助于预测，未来增加的氮沉降可能会改变土壤微生物功能结构，这将导致青藏高原高寒草原微生物介导的生物地球化学动力学发生变化，并对微生物 C、N 和 P 循环产生巨大影响。
