生物土壤结皮及结皮下土壤微生物和线虫对模拟增温和降水改变的响应

As important features of the global climate change，climate warming and precipitation variation, have become an indisputable fact. Biological soil crusts (biocrusts) act as the important part of organisms in desert ecosystems. How to responses of biocrusts and soil under biocrusts to global climate change is one of common concerns at domestic and abroad in recent years. Soil microbes and nematodes could be used as significant bioindicators of soil quality and evaluated soil health in desert areas. However, so far little has been known on the responses of biocrusts and soil under biocrusts to simulated warming and variation in precipitation in desert areas at present. Biocrusts and sand dune soil under biocrusts in revegetated areas at the southeastern edge of the Tengger Desert were taken as objects of this study. The effects of simulated warming and precipitation variation on biocrusts and soil microbial community diversity, microbial biomass , soil enzyme activities， soil basal respiration and nematode communities under biocrusts were studied in the region. The result could explore the influences of simulated warming and precipitation variation to biocrusts and soil microbes and nematodes under biocrusts and further estimate of the impacts of global climate change on soil quality and the desert ecosystems. The research would provide the scientific basis for the construction of ecological engineering in arid areas and the management of degraded ecosystems in China.

以气候变暖和降水格局变化为重要特征的全球气候变化已成为一个不争的事实。生物土壤结皮作为荒漠生态系统的主要生物组分，结皮及其覆盖下的土壤如何应对全球气候变化，是近年来国内外广泛关注的焦点问题之一。土壤微生物和线虫能敏感指示土壤质量的变化，是衡量荒漠区土壤健康程度的重要生物学指标，而目前有关荒漠区生物土壤结皮及结皮下土壤微生物和线虫对增温和降水改变响应的研究知之甚少。本项目以腾格里沙漠东南缘植被固沙区的生物土壤结皮及结皮下的沙丘土壤为研究对象，研究模拟增温和降水改变对生物土壤结皮及结皮下土壤微生物群落多样性、微生物量、土壤酶活性、土壤基础呼吸和线虫群落的影响，揭示增温和降水改变对生物土壤结皮及结皮下土壤微生物和线虫的影响，进而评析全球气候变化对荒漠区土壤质量及荒漠生态系统的影响，为我国干旱沙区生态工程建设和退化生态系统管理提供科学依据。

以气候变暖和降水格局改变为重要特征的全球气候变化已成为一个不争的事实。生物土壤结皮作为荒漠生态系统的主要生物组分，结皮及其覆盖下的土壤如何应对全球气候变化，成为全球广泛关注的焦点问题。土壤微生物是衡量土壤进程的重要生物学指标，而目前有关土壤微生物对荒漠区增温和降水改变响应的研究知之甚少。本项目以腾格里沙漠植被固沙区生物土壤结皮及结皮下的沙丘土壤为研究对象，结合现代的宏基因组测序法和常规的研究方法测定其土壤微生物群落多样性、微生物量碳、氮和磷、基础呼吸及脲酶、蔗糖酶、脱氢酶、碱性磷酸酶和蛋白酶的活性，明确气候变化对上述土壤微生物指标的影响，进而评析全球气候变化对荒漠生态过程的影响。研究表明：（1）短期增温可提高研究区生物土壤结皮及结皮下土壤细菌数量和多样性，而降低土壤真菌数量和多样性，且依据微生物菌群类型的变化，增温对荒漠区土壤产生胁迫。此外，短期增温可提高生物土壤结皮下表层土壤的微生物量、基础呼吸和土壤酶的活性，指示短期增温可加速土壤营养的转化率。（2）减雨50%可降低研究区的土壤细菌和真菌群落的数量和多样性，明显改变土壤微生物群落的组成，且依据菌群类型的变化，减雨对荒漠区土壤产生胁迫。此外，增雨50%和减雨50%可显著提高生物土壤结皮下表层的土壤微生物量、基础呼吸和土壤酶的活性（p<0.05），指示降水变化可加速土壤营养的转化率。（3）增雨50%+增温和减雨50%+增温可提高研究区的土壤细菌数量和多样性，而降低土壤真菌的数量和多样性，明显改变土壤微生物群落的组成，且依据菌群类型的变化，增温+降水变化对荒漠区土壤产生胁迫。此外，增温+降水改变互作可提高生物土壤结皮下表层的土壤微生物量、基础呼吸和土壤酶活性，指示增温+降水改变互作可增加土壤易利用的养分库和加速土壤营养的消耗，促进土壤退化。因此，全球气候变暖对荒漠区土壤质量及荒漠生态系统会产生负面的影响，其可能导致荒漠土壤及荒漠生态系统的退化。