中梁山岩溶槽谷区荒草地土壤微生物群落对隧道建设的响应

隧道工程建设给地方交通和经济发展带来便利的同时，也造成地下水漏失和地下水文流场改变，可能引起土壤微环境和土壤微生物群落的改变，进而严重影响上覆区域生态系统平衡。以重庆市中梁山岩溶槽谷为例，选取隧道影响区和无隧道影响区典型荒草地，通过16S rDNA高通量测序对比微生物群落结构差异，研究微生物群落多样性对土壤pH、含水率和土壤养分变化的响应。结果表明：隧道影响区Alpha多样性反映的土壤微生物总丰度和多样性大于无隧道影响区，Beta多样性反映的土壤微生物群落结构存在显著差异；Wilcoxon检验说明norank_o__iii1-15、norank_c__Gemmatimonadetes、norank_o__MND1是隧道影响区土壤中显著增加的微生物物种，其相对丰度为无隧道影响区土壤的2倍以上；RDA分析表明土壤pH和含水率是驱动土壤微生物群落结构变化的主要因素。隧道建设使其影响区内土壤水分垂直漏失比无隧道影响区更严重，土壤含水率下降，导致pH上升、土壤养分下降，利于土壤中norank_o__iii1-15、norank_c__Gemmatimonadetes、norank_o__MND1等适应低含水率、高pH、贫营养环境的优势菌群生长繁殖。

Response of soil microbial community in grassland to tunnel construction in the karst trough valley, Zhongliang Mountain, Chongqing

The tunnel constructions were beneficial to local traffic transportation and economic development, but may cause underground water leakage and result in changes in the hydrological flow. The change in the groundwater characteristics would lead to soil micro-environmental and microbial community variations, ultimately influencing the balance of the overlying ecosystem. In this study, samples were collected from grasslands affected and unaffected by tunneling in a typical karst trough valley located at Zhongliang Mountain, Chongqing. We analyzed the soil pH, water content, and nutrient, as well as the 16S rDNA sequencing of DNA extracted from the soil. According to the comparison of the soil microbial communities between the grasslands affected and unaffected by tunneling, the dominant microorganisms at areas affected by tunneling were identified, with which the relationship between the soil pH, water content, and soil organic matter content was determined. The results showed that the total abundance and diversity of soil microorganisms, reflected by the Alpha diversity in the valley affected by tunneling, were greater than those in the valley unaffected by tunneling. The Beta diversity indicated that the microbial species in grasslands affected and unaffected by tunneling were significantly different. The Wilcoxon test identified that norank_o__iii1-15, norank_c__Gemmatimonadetes, and norank_o__MND1 were the dominant microorganisms in the grassland soils affected by tunneling and the relative abundance of the above three microbial species was more than twice of that in grassland soils unaffected by tunneling. The redundancy analysis (RDA) revealed that the soil pH and water content were the dominant environmental factors influencing the soil microbial community composition. At the areas affected by tunneling, the tunnel construction resulted in intensive groundwater leakage and a decrease in the soil water content, which led to an increase in the pH and a decrease in the soil nutrients, resulting in the increasing development of the genus norank_o__iii1-15, norank_c__Gemmatimonadetes, and norank_o__MND1, which are acclimatized to the drought-ridden, high pH, and oligotrophic soil environment in the valley affected by tunneling.