生物质炭输入对毛竹林土壤硝化和反硝化过程的影响及其微生物机理研究

Under an intensive mode of management and production, Moso bamboo forest has become one of the important sources of N2O emission mainly due to over-fertilization of nitrogen. It has been well documented that biochar has a great potential in mitigating the emission of N2O, an important greenhouse gas, from soil through affecting the microbe-driven nitrification and denitrification processes. However, most of studies focused on the effect of biochar application on N2O emission in agricultural soils. There exists an information gap concerning the nitrification and denitrification in Moso bamboo forest soil. In addition, the influence of biochar application on inhibiting N2O emission and related microbial mechanism have been poorly understood. Therefore, the primary objective of this study is to investigate the effects of two biochars, which are made of bamboo residue and rice straw respectively, on N2O emission from Moso bamboo forest soil through laboratory and field experiments in combination with 15N isotope tracer technology. The intervention of biochar in nitrification and denitrification processes related to N2O emission will be critically evaluated. In addition, the responses of microbial community concerning nitrogen cycle to biochar application will be also elucidated through microbiological molecular biotechnologies such as Q-PCR and metagenomic analytical methods. It is hoped that the outcomes from this project will not only provide with a better understanding in the mechanisms in relation to the inhibitory effects of biochar on N2O emission from Moso bamboo forest, but also enlighten an innovative approach in coping with mitigating greenhouse gas emissions coupled valid utilization of forestry and agricultural wastes in China.

由于毛竹林现多采用高度集约化经营方式，氮肥的过量施用导致毛竹林成为我国森林生态系统N2O的重要排放源之一。大量研究表明，生物质炭具有影响由微生物主导的土壤硝化和反硝化过程，缓解土壤N2O排放的巨大潜力。然而，现有的研究大多局限于生物质炭对于农田土壤N2O排放的抑制作用。目前，有关毛竹林土壤硝化和反硝化过程研究较为薄弱，生物质炭对竹林土壤N2O减排效应及其微生物机理研究也鲜有报道。因此，本项目拟采用15N同位素示踪技术，通过野外林地和温室培养实验，研究竹炭和秸秆炭输入对土壤硝化和反硝化过程的影响与降低N2O释放通量的贡献及其内在关联；并借助定量PCR和宏基因组等分子生物学新兴技术，阐明与毛竹林系统氮素循环密切相关的微生物对生物质炭输入的响应，揭示生物质炭输入对毛竹林土壤N2O形成和释放的作用机制，为我国农林废弃物的资源化利用和森林生态系统温室气体减排的耦合研究提供新的思路。

氮肥的过量施用导致毛竹林成为我国森林生态系统N2O的重要排放源之一。生物质炭具有影响由微生物主导的土壤硝化和反硝化过程，缓解土壤N2O排放的巨大潜力。因此，本项目采用15N同位素示踪技术，通过野外林地和温室培养实验，研究竹炭和秸秆炭输入对土壤硝化和反硝化过程的影响及其与土壤N2O排放的内在关联。主要结果如下：1、竹炭和秸秆炭的添加均可以显著降低毛竹林N2O排放量，但是两种生物质炭之间没有显著性的差异。2、生物质炭的添加有助于增加氨氧化过程Nitrosospira、亚硝酸氧化过程Nitrospira和反硝化过程Pseudomonas微生物的百分含量，促进土壤AOA和norZ基因丰度，对AOB、nirS 和nirK基因没有显著性的影响。相关性分析表明，生物质炭添加对毛竹林土壤N2O的抑制作用，很大程度上来源于对毛竹林土壤norZ功能基因的促进作用。3、15N同位素标记实验表明，生物质炭对N2O排放的抑制作用主要是通过影响土壤反硝化过程和异养硝化过程产生的。该研究揭示了土壤氮素循环微生物对生物质炭输入的响应，阐明了土壤N2O形成和释放的机制，为我国农林废弃物的资源化利用和森林生态系统温室气体减排的提供了新的思路。