石漠化地区AM真菌促进桑树根系摄取土壤氮的调控机制

石漠化地区植被恢复受N限制，AM真菌促进桑树吸收N，但调控机制不明晰。本项目研究接种处理下土壤团聚体粒级及有机N初级矿化速率差异特征，探讨各粒级酶活性、微生物量碳氮变化对有机N矿化贡献率，揭示AM真菌提高供氮潜力促进氮吸收的团聚体调控机制；借助根系监测系统和非损伤微测技术观测根系分布及其对NO3-和NH4+吸收变化，分析根系N代谢关键限速酶活性与N吸收速率关系，探讨AM真菌通过改变根系分布比例及N代谢酶活性对根系获取N的调控机制；基于15N同位素示踪技术分析AM真菌对根系15NO3-和15NH4+吸收影响，利用宏基因组测序分析根内外微生物群落变化，并预测分析根系微生物功能，厘清与N代谢之间关系，揭示AM真菌诱导“选择招募”氮代谢微生物提高吸收利用N的调控机制。研究成果将深化和丰富石漠化环境中有限N资源高效利用理论知识，为研发高效植被恢复菌根技术提供支撑，具有较高理论研究价值和现实意义。

Vegetation restoration is restricted by N in rocky desertification areas. Arbuscular mycorrhizal fungi promote mulberry trees to absorb N, but the regulatory mechanism is unclear. This project studied the difference characteristics of soil aggregate and primary mineralization rate of organic N under inoculation treatment,and discussed the contribution rate of enzyme activity of soil aggregate and the change of carbon and nitrogen of microbial biomass to the mineralization of organic N, and revealed the regulation mechanism of the aggregate by AM fungi to improve nitrogen supply potential and promote nitrogen absorption.Then,the root distribution and its absorption of NO3- and NH4+ were observed with the help of root monitoring system and non-invasive micro-test technology. The relationship between the activity of key rate-limiting enzyme of N metabolism and the absorption rate of N was analyzed.Last,the effects of arbuscular mycorrhizal fungi on root 15 no3 - and nh4 + absorption are analyzed by 15 N isotope tracer technique, and the changes of root microbial community and function are analyzed by macro genome sequencing,and the relationship between N metabolism and root microbial community are clarified.To increase the absorption of N,arbuscular mycorrhizal fungi induce root to recruit microbes of nitrogen metabolism. The research results will deepen and enrich the theoretical knowledge of efficient utilization of finite N resources in rocky desertification environment, and provide support for the research and development of efficient mycorrhizal technology for vegetation restoration, which has high theoretical research value and practical significance.