典型岩溶槽谷区氨氧化微生物丰度对隧道建设的响应——以中梁山为例

Responses of the ammonia-oxidizing microorganisms' abundance to tunnel evacuation in karst trough volley: a case study in Zhongliang Mountain, Chongqing, China

摘要:

氨氧化微生物介导土壤中铵态氮的氧化，是土壤硝化作用的第一步。【目的】在大型隧道工程影响的岩溶区，了解氨氧化微生物对土壤含水率和营养环境变化的响应对于研究隧道建设引起的生态环境改变和氮循环过程变化都有十分重要的意义。【方法】本研究以重庆市北碚区中梁山龙凤槽谷为例，对比受隧道影响的龙凤槽谷和不受隧道影响的龙车槽谷中4种土地利用方式（荒草地、竹林地、混交林以及菜园地）下的土壤中，3种氨氧化微生物（氨氧化细菌AOB、氨氧化古菌AOA、亚硝酸盐氧化细菌CMX）的丰度变化，结合土壤含水量、pH以及土壤营养元素等的变化，分析隧道建设引起的可培养氨氧化微生物数量变化及其过程机理。【结果】结果发现：①由于隧道开挖揭露了地下含水层，导致地下水位下降、土壤含水率降低、pH值升高、硝态氮含量增加、隧道影响区AOA、AOB和CMX丰度显著低于非隧道影响区，后者数量分别是前者的4.8、4.4和3.9倍；②受岩溶区碱性土壤环境和地下水以及可溶物极易漏失的影响，铵态氮等底物浓度并不是氨氧化细菌的主要影响因素，AOA丰度与土壤含水率和土壤酸碱缓冲性能呈正相关（P<0.01），CMX和AOB丰度都与土壤硝态氮含量呈极其显著的负相关（P<0.05），AOB丰度还与土壤的pH值呈负相关（P<0.05）。【结论】本研究揭示了岩溶区土壤理化性质中的含水率和pH是影响3种氨氧化微生物丰度的主要因子，隧道建设引起的地下水漏失和土壤有效水分降低是引起氨氧化微生物含量下降的主要原因，一定程度上改变了隧道建设影响区的硝化过程，但影响程度和更多微生物参与的氮循环过程改变还需要进一步详细的研究。

Abstract:

Ammonia oxidizing microorganisms mediate the oxidation of ammonium nitrogen in the soil, which is the first step of nitrification.[Objective] In the karst areas affected by large tunnel projects, understanding the response of ammonia oxidizing microorganisms to changes in soil moisture and nutrient condition has great significance for researching the changes of the ecological environment and the nitrogen cycle process caused by tunnel construction.[Methods] This study took four land uses (Grass land; bamboo land; mixed forest; vegetable land) of Longfeng trough valley, which is tunnel-affected-area and the Longche trough valley, which is non-tunnel-affected-area in Zhongliang Mountain, Beibei, Chongqing as an example, comparing the abundance of three ammonia oxidizing microorganisms (Ammonia oxidizing bacteria AOB, ammonia oxidizing archaea AOA, nitrite oxidizing bacteria CMX) and combining with the changes of soil water content, pH, and soil nutrient elements, to analyze the changes of ammonia oxidizing microorganisms caused by tunnel construction and its process mechanism.[Results] The results shows:① As the tunnel excavation exposed the underground aquifer, the level of groundwater decreased, the soil moisture content decreased, the pH and the nitrate nitrogen increased. The abundances of AOA, AOB and CMX of the tunnel-affected-area were significantly lower than the non-tunnel-affected zone, the abundances of the latter is 4.8, 4.4 and 3.9 times of the former respectively; ② Affected by the alkaline environment in soil and groundwater of karst area, as well as the vulnerability to leaking of solubles extremely easily, the concentration of substrates such as ammonium nitrogen is not the main influencing factors of ammonia oxidation microorganisms, the abundance of AOA is positively correlated with soil moisture content and soil buffering capacity (P<0.01), the abundances of CMX and AOB are both negatively correlated with soil nitrate nitrogen content (P<0.05), AOB abundance is also negatively correlated with soil pH (P<0.05).[Conclusion] This study reveals that soil physical and chemical properties like the soil moisture content and pH in karst areas are the main factors affecting the abundance of three ammonia oxidizing microorganisms. The leakage of groundwater and the decrease of soil effective moisture caused by tunnel construction are responsible for the decrease of ammonia oxidizing microorganisms abundances, which also change the nitrification process in tunnel-affected-area to some extent. However, the degree of influence and the changes of nitrogen cycle which more microorganisms involve in need to be further studied in detail.