热带北缘雨林树木径向生长对气候变化和大气CO2浓度升高的响应

Tropical rainforest ecosystems play an important role on global carbon cycle and vegetation-climate feedback. The responses of tropical rainforest ecosystem on global climate change became a hotspot in science communities in recent years. Campared with controlled experiments (i.e. experimental warming or free air CO2 enrichment) or Permanent Sample Plots (PSP), the dendrochronology methods are able to monitor tropical tree growth history, as well as its driving forces, at a longer-term scale. Based on two tropical rainforest ecosystems with different drought stress, the tropical seasonal rainforest (wet habitat) and monsoon rainforest over limestone (dry habitat), this project aims to study growth rates and intrinsic water-use efficiency of canopy tree species growing in the tropical rainforests located at the north edge of Asian tropics. A total 10 dominant tree species shall be selected, with 5 of each habitat. Three diameter (age) classes shall be defined for sampling for each species. By combining tree-ring width and stable isotope (d13C and d18O) measurements, we will able to detect radial growth-climate response patterns of tropical rainforest tree species, as well as explore long-term trends of growth rates and tree water-use efficiency. Tree growth rates, as well as base area increment (productivity), shall be modeled using linear mixed-effects models, by taking climate factors and atmospheric CO2 concentration as fixed effects. According to the above considerations, the proposed project intend to find the unanswered physiological mechanisms that driving tree growth variability of tropical rainforests in the north edge of Asian tropics. Our results shall provide important clues on carbon balance of tropical rainforest ecosystems, as well as modeling vegetation-climate feedbacks, under future global change scenarios.

热带雨林生态系统在全球碳循环和气候反馈方面具有重要作用，研究热带雨林生态系统对全球气候变化的响应是当前的热点之一。与人工控制实验和森林长期监测样地相比，树木年轮分析能在更长时间尺度上反映热带树木的生长动态历史及其驱动因素。本项目以位于东南亚北缘的热带雨林生态系统为研究对象，选择热带季节雨林（湿性）和石灰山季雨林（干性）两种水分条件迥异的生境对比，在每个生境选择5个主要冠层树种，每个树种选择3个径级，结合树轮宽度（生长量）测定和稳定性同位素（生理过程）分析，研究热带北缘雨林树种径向生长对气候响应的模式，分析树木生长速率和长期水分利用效率的变化趋势，构建热带北缘雨林树木生长对气候因子和大气CO2浓度响应的机理模型，揭示区域气候变化和大气CO2浓度升高对热带北缘雨林树木生长趋势影响的生理驱动机制，为正确评估全球变化背景下热带北缘雨林的碳收支平衡及其对气候变化的反馈效应提供理论依据。

热带雨林生态系统在全球碳循环和气候反馈方面具有重要作用。本项目选择生长于热带季节雨林（湿性）和石灰山季雨林（干性）的热带树种进行树木年轮采样，树轮宽度测定和稳定性同位素分析，研究了热带北缘雨林树种径向生长对气候响应的模式，分析树木生长速率和长期水分利用效率的变化趋势。项目按计划展开，开展了热带树木年轮特征分析，研究了代表性树种的径向生长速率和水分利用效率变化趋势，建立了热带雨林树木生长和气候响应监测研究平台。项目共发表研究论文7篇，其中SCI论文5篇。培养了3名硕士研究生和1名博士研究生，正在培养2名博士研究生和4名硕士研究生。