土壤氮循环微生物过程的分子生态学研究进展

固氮作用、硝化作用和反硝化作用是土壤微生物参与氮素循环的三个重要方面。自分子生态学方法应用于土壤学后,土壤微生物作用于氮素循环过程的机理研究取得了若干重要进展。包括:1)利用固氮菌的nifH基因作为分子标记研究有机质、氮素与固氮微生物之间的关系,发现固氮微生物的丰度和群落结构与土壤有机质含量呈正相关。然而,固氮微生物的丰度和群落结构与土壤速效N含量呈负相关,施用氮肥会抑制固氮微生物的生长,施氮土壤固氮微生物数量减少,多样性降低。2)以氨氧化微生物功能基因为探针,揭示了土壤pH与氨氧化微生物分布关系密切,碱性土壤中氨氧化细菌是硝化作用主要参与者,而酸性土壤中氨氧化古菌是硝化作用的主导者。土壤中N素的含量也影响氨氧化微生物的数量和群落结构,施入氮肥后氨氧化微生物的数量和活性增加。3)利用反硝化功能基因为分子标记研究土壤因子对反硝化细菌群落的影响,阐明了土壤可溶性有机碳、pH和土壤水分是影响反硝化细菌数量和群落结构的重要因子,并且发现土壤反硝化细菌与土壤反硝化能力和氧化亚氮释放之间存在着一定的联系,但这种联系在不同研究对象中存在差异,需要进一步确认。目前,利用分子生物学技术解析土壤氮素循环微生物生态功能取得了重要的进展,但还需进一步深入。今后,将采用包括同位素在内的示踪技术与分子生物学方法相结合共同分析氮循环不同代谢过程微生物种群间的相互关系以及氧化亚氮产生与硝化和反硝化微生物之间的关系。

Research progress of the molecular ecology on microbiological processes in soil nitrogen cycling

Nitrogen fixation, nitrification and denitrification are three important ecological processes in soil nitrogen cycling, and they are mainly driven by soil microorganisms. The recent progresses in relation to the relationships between soil nitrogen cycling and soil functional microorganisms are reviewed in this paper. Firstly, soil nitrogen-fixing bacterial communities have been studied using nifH gene molecular marker. A significantly positive correlation between soil organic matter content and the abundance and composition of the nitrogen-fixing community was observed. The abundance and diversity of the nitrogen-fixing community were declined due to the application of nitrogen fertilizers. Secondly, the corelations between soil characteristics and soil nitrifiers was intensively investigated. Results indicated that ammonia-oxidizing archaea (AOA) played a leading role in nitrification in acid soils, whereas the ammonia-oxidizing bacteria (AOB) played a key role in nitrification in cultivated and alkaline soils. Application of nitrogen fertilizer increased the copy numbers and activities of ammonia oxidizing microorganisms. Thirdly, the effect of environmental factors on soil denitrifiers was also researched, it was demonstrated that soil dissolved organic carbon, pH and soil water content were the key factors affecting the population size and community composition of soil denitrifying bacteria. It was further suggested that the composition and abundance of soil denitrifiers were closely associated with soil denitrification potential and N2O emmissions in ecosystems. In the future, as some new technologies introduced into soil microbial ecology, such as isotopic tracer, soil nitrogen cycling molecular mechanisms would be more clearly explored.