Response of Nitrifier and Denitrifier Abundance and Microbial Community Structure to Experimental Warming in an Agricultural Ecosystem

Soil microbial community plays an important role in terrestrial carbon and nitrogen cycling. However, the response of the soil nitrifier and denitrifier communities to climate warming is poorly understood. A long-term field warming experiment has been conducted for 8 years at Luancheng Experimental Farm Station on the North China Plain; we used this field to examine how soil microbial community structure, nitrifier, and denitrifier abundance respond to warming under regular irrigation (RI) and high irrigation(HI) at different soil depths (0–5, 5–10, and 10–20 cm). Nitrifier, denitrifier, and the total bacterial abundance were assessed by quantitative polymerase chain reaction of the functional genes and 16S rRNA gene, respectively. Bacterial community structure was studied through high throughput sequencing of the 16S rRNA gene. Under RI, warming significantly (P < 0.05) increased the potential nitrification rate and nitrate concentration and decreased the soil moisture. In most of the samples, warming increased the ammonia-oxidizing bacteria abundance but decreased the ammonia-oxidizing archaea (AOA) and denitrifier (nirK, nirS, and nosZ genes) abundance.

土壤微生物群落在陆地碳氮循环中扮演着关键角色。然而，土壤硝化菌与反硝化菌群落对气候变暖的响应机制仍不明确。华北平原栾城实验农场站开展了一项为期8年的长期野外增温试验，本研究利用该试验平台，探究了常规灌溉（RI）与高灌溉（HI）条件下，不同土层深度（0–5 cm、5–10 cm、10–20 cm）的土壤微生物群落结构、硝化菌及反硝化菌丰度对增温的响应特征。硝化菌、反硝化菌及总细菌的丰度分别通过功能基因与16S rRNA基因的定量聚合酶链式反应（quantitative polymerase chain reaction）进行评估；细菌群落结构则通过16S rRNA基因的高通量测序（high throughput sequencing）分析获得。在常规灌溉条件下，增温显著（P < 0.05）提升了潜在硝化速率与硝酸盐浓度，并降低了土壤含水量。在多数样本中，增温增加了氨氧化细菌的丰度，但降低了氨氧化古菌（ammonia-oxidizing archaea，AOA）及反硝化菌（nirK、nirS、nosZ基因）的丰度。