植物碳源输入调控南亚热带森林土壤氮素迁移转化过程的微生物学机制

全球变化正深刻影响着森林植被光合能力，进而改变植物向土壤输送有机碳的过程。植物作为森林土壤有机碳的主要来源，可通过地上凋落物分解与地下根系活动的方式影响土壤氮素迁移转化。然而，目前尚不清楚植物碳源输入改变如何影响森林土壤氮素转化过程及其微生物机制。本项目以南亚热带季风常绿阔叶林为研究对象，基于野外控制试验采用添加/去除凋落物以及断根的方法来改变植物地上、地下部分碳输入，利用15N和18O同位素示踪技术和分子生物学技术手段，量化氮素初级转化速率和区分硝化与反硝化途径对N2O排放的贡献，旨在解析不同碳源输入情景下南亚热带森林土壤无机氮的转化路径和N2O的来源途径；并从氮循环微生物功能群落及其代谢功能的角度揭示其微生物机制。项目开展将有助于揭示全球变化背景下森林土壤氮素迁移与保持机理，为准确评估该区域森林储氮能力和氮氧化物排放潜势并预测其未来变化趋势提供科学依据。

Global changes are profoundly affecting the photosynthetic capacity of forest vegetations, which can alter the transport of organic carbon from plants to soils. As the main sources of forest soil organic carbon, plants can alter soil nitrogen (N) translocation and transformation via aboveground litter decomposition and belowground root activity. However, it remains unclear how plant carbon source inputs affect soil N transformation processes and its microbial mechanism in forest ecosystems. This project aims to identify the pathways of inorganic N transformation and nitrous oxide (N2O) emission under different carbon source inputs and to explore the underlying mechanisms in subtropical forests. To achieve this, a field manipulation experiment has been conducted in a monsoon evergreen broadleaf forest in South China. Several treatments including litter addition, litter removal and root exclusion have been applied to manipulate aboveground and belowground carbon inputs. The gross N transformation rates and contributions of nitrification and denitrification to N2O emission will be quantified using a 15N isotope tracer technique. To further clarify the underlying microbial mechanisms, soil N-cycling microbial communities and their metabolic functions will be analyzed using molecular biology techniques and 18O isotope tracer techniques. This project will allow to clarify the mechanisms of soil N translocation and retention in forest ecosystems under global changes, providing a scientific basis for accurately assessing N storage capacities and NOx emission potentials and predicting the future trends in subtropical forest ecosystems.