微生物作为生态系统功能的主要参与者，对降水变化引起的土壤水分变化的响应是科学评估气候变化对半干旱生态系统
影响的一个非常重要的方面． 为研究降水变化对土壤微生物群落结构多样性的影响，在黄土高原进行了为期 2 a 的原位模拟降
雨变化实验，设置了5 种降水梯度，即减少自然降雨的80%和40%、自然降雨和增加自然降雨的 40%和 80%(编号为 D80、D40、
NP、I40 和 I80)． 结果表明: ① 减雨或增雨 80% 处理中 C/N 较低，而增雨 40% (I40)时最大，0 ～20 cm 土层的均值为 10. 76;
MBC/MBN 在减雨80%(D80)和增雨80%(I80)处理中随土层变化显著，D80 时最大值为 14. 15． ② 黄土高原天然草地土壤中，
主要的优势菌门为放线菌门(Actinobacteria)、变形菌门(Proteobacteria)、绿弯菌门(Chloroflexi)、酸杆菌门(Acidobacteria)，主要的
优势菌纲为放线菌纲(Actinobacteria)、酸杆菌纲(Acidobacteria)、α-变形杆菌纲(α-Proteobacteria)和热微菌纲(Thermomicrobia)．
③ ＲDA 分析显示，在降水处理条件下，土壤溶解性有机碳、可溶性有机氮、电导率、pH 值的变化是影响该研究区土壤细菌分布的
主要因素． 总之，干旱或极端降水对黄土高原区土壤活性有机质含量和土壤细菌种群多样性及丰度影响显著．
其他摘要
As the main participants of ecosystem functions，the response of microorganisms to variations in soil moisture caused by the
changes in precipitation amounts should be quantified to evaluate the impact of climate change on semi-arid ecosystems． For this
purpose，a two-year simulation of the changes in the rainfall patterns was conducted on the Loess Plateau，and five precipitation
treatments (80% and 40% decrease in precipitation，D80，D40; natural precipitation，NP; 40% and 80% increase in precipitation，
I40，I80) were set up． The results showed that: ① Compared with NP，the carbon-to-nitrogen ratio (C/N) was lower in DP80 or
IP80，while it reached the maximum value in I40． The mean C/N value of the 0-20 cm soil layer was 10. 76． The microbial biomass
carbon to microbial biomass nitrogen ratio (MBC/MBN) varied significantly with the soil layer in the treatments of D80 and I80，and
the maximum value was 14. 15 in D80． ② In the grassland soil naturally growing on the Loess Plateau，at the phylum level，the
dominant phyla were Actinobacteria， Proteobacteria， Chloroflexi， and Acidobacteria． At the class level， Actinobacteria，
Acidobacteria，α-Proteobacteria，and Thermomicrobia were predominant． ③ ＲDA analysis showed that changes in soil dissolve organic
carbon (DOC)，dissolved organic nitrogen (DON)，elemental carbon (EC)，and pH values were the main factors affecting the
distribution of soil bacteria under the five precipitation treatments in the study area． Overall，80% increase or decrease in precipitation
has a significant impact on soil active organic carbon content and bacterial abundance，especially D80． In conclusion，drought or
extreme precipitation may considerably change the active organic matter content and bacterial community diversity and abundance in the
soils of the Loess Plateau．
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