增温对南亚热带山地常绿阔叶林氮循环的影响

气候变暖会改变森林生态系统氮素转化、储存与去向特征，但气候变暖情景下热带、亚热带森林生态系统的氮循环规律及其潜在机制并不完全清楚。目前增温对森林氮循环的研究工作主要集中在高纬度和高海拔地区，然而气候变暖对高氮沉降的热带、亚热带地区的森林氮循环可能影响更大，因此亟需在该气候区开展相关研究工作。本项目拟利用前期修建好的增温研究平台，选择南亚热带山地常绿阔叶林生态系统为研究对象，利用15N同位素示踪法和质量平衡法，分析不同树种在增温影响下氮素吸收、固定与分配的差异，明确增温影响下土壤氮素转化、储存与去向及其微生物调节机制，从而系统地研究南亚热带山地常绿阔叶林生态系统氮循环对气温上升的响应机制与适应规律，进一步阐明增温背景下该森林类型在植物个体和生态系统水平上氮素利用、储存与生产力之间的关系，为该地区森林生态系统管理及相关政策的制定提供理论指导。

Climate warming will change plant nitrogen (N) fixation, soil N transformation as well as soil nitrous oxide emissions in forest ecosystems. However, we still lack the information about the effects of warming on N cycles and the underlying mechanisms in tropical and subtropical forests where N deposition is very high. The experiments concerning the effects of climate warming on N cycles in forests were mostly carried out in high-latitude and high-altitude areas. However, tropical forests are perceived to have more deleterious consequences compared to other regions under climate warming. It is imperative to do the warming experiments in tropical areas. Basing on the long-term experiment of rising air temperature at Dinghushan Forest Ecosystem Research Station, by using 15N isotopic tracer method and mass balance approach, this project aims to study the effects of rising air temperature on N cycles in mountain evergreen broad-leaved forest. The N concentrations in the plants, soil and soil water in response to rising air temperature will be analyzed as well as soil microbes and enzymes. N2O release from soil will also be measured. The mechanisms of the N cycle in mountain evergreen broad-leaved forest affected by warming will be revealed. Implement of this project would provide scientific basis for the sustainable management of forest ecosystems.