氮沉降增加促进亚热带森林土壤N2O排放的微生物学机制

Nitrous oxide (N2O) is an important greenhouse gas that also disrupts ozone layer. Recent studies revealed that elevated atmospheric nitrogen (N) deposition facilitated N2O emission in subtropical forest soil. However, the microbial mechanisms regulating its emission in subtropical forest soil are still poorly understood. In this project, N gradient was applied at four levels to simulate N deposition. Using molecular biology techniques including experiments both in situ and in laboratory through qualitative and quantitative analysis of functional genes of amoA, narG, nirK, nirS, nosZ and arbuscular mycorrhizal fungi (AMF) , we choose the subtropical evergreen broad-leaf forest soil to study the response mechanisms of the abundance and structure of ammonia-oxidizing archaea (AOA) and denitrifiers to elevated N deposition and the effects of elevated N deposition on the abundance and diversity of AMF communities. At the same time, we study the generation paths and theirs proportion of soil N2O emission in subtropical broad-leaf forest soil using N, O isotopic signature technique. Results of this study will reveal the relationship between soil N2O emission and soil functional microorganisms, clarify the microbial mechanisms of elevated nitrogen deposition stimulating N2O emission in subtropical broad-leaf forest soil，and provide theory basis for the N2O emission characteristics under the context of elevated N deposition in subtropical forest soil.

氧化亚氮（N2O）是一种重要的温室气体且能破坏臭氧层。研究发现，氮沉降增加促进亚热带森林土壤N2O的排放。然而，氮沉降增加背景下N2O排放的微生物调控机制尚不明确。本项目拟以亚热带常绿阔叶林土壤为研究对象，模拟4个不同氮沉降水平进行室内培养与野外原位试验，利用分子生物学技术，通过对amoA，narG，nirK，nirS，nosZ功能基因及丛枝菌根真菌（AMF）进行定量与定性分析，研究土壤氨氧化古菌（AOA），反硝化菌丰度和群落多样性对氮沉降增加的响应；不同氮添加水平对土壤AMF丰度和多样性的影响；同时利用N，O同位素标记技术，研究土壤N2O排放的产生路径及所占比重。阐明亚热带森林土壤N2O排放与土壤功能微生物丰度和群落多样性之间的关系，揭示氮沉降增加促进亚热带森林土壤N2O排放的微生物学机制，为氮沉降增加背景下亚热带森林土壤N2O排放特征提供理论依据。

氮沉降增加促进南亚热带森林土壤氧化亚氮（N2O）的排放。然而，氮沉降增加背景下N2O排放的微生物调控机制尚不明确。本项目通过氮沉降增加对亚热带森林土壤氮素转化，功能微生物丰度的影响进行研究。发现了（1）氮沉降增加加速了土壤氮素损失（氮淋溶和N2O排放）。（2）氮沉降增加背景下N2O排放增加的原因，可能是氮添加增加了nirK功能基因丰度却降低了nosZ基因的丰度。（3）在湿季，N2O排放与微生物量碳氮，土壤水分含量，土壤有机碳和总氮呈显著正相关却与土壤铵态氮的含量呈显著负相关。研究结果将进一步解释氮沉降增加促进N2O排放的微生物学机制，为缓解N2O排放策略提供一定的理论基础。