不同林龄杨树气孔导度斜率变异性及其对于干旱的响应

The regulatory role of stomata in carbon and water cycles is the most critical process in simulating ecosystem performances in terrestrial ecosystems. Compared with instant measurements, the changes in stomatal slope with plant’s biophysical environment provide a simple but synthetic framework for studying climate-change related carbon and water cycling, because of its sensitivity to CO2, vapor pressure deficient, and photosynthesis, as well as its crucial information about climate change effects on photosynthesis and water use efficiency. How stomatal slope of poplar trees varies among different tree ages and at drought conditions requires further study. In this project, we will focus on one Populous tree variety and investigate the variability of stomatal slope acclimates to drought conditions at multiple ages, through field measurements and modeling. We will modify the widely-used stomatal conductance model in order to develop suitable models for predicting stomatal conductance under various drought conditions. The outcomes of this project will: (1) improve the understanding of the regulatory role of stomates; (2) reduce the uncertainty of ecosystem models in simulating and predicting carbon and water fluxes; (3) help understanding the strategy of plants adapting to climate change and directing the species-selecting policy and water management strategy.

气孔调节功能是陆地生态系统碳-水耦合过程中最重要的环节。与即时的气孔导度测量相比，气孔导度斜率能有效反应气孔导度对于[CO2]、饱和水汽压亏缺和光合作用的敏感性，包含了环境因子对光合作用和水分利用效率等的综合影响，为研究全球变化下陆地生态系统碳-水耦合关系提供了一个简明且综合的框架。杨树在不同年龄阶段，尤其是在水分限制的情况下，气孔导度斜率的变化规律及其影响因素还有待于深入探讨。本项目以同一品种杨树为研究对象，通过测量和模型模拟，揭示不同林龄杨树气孔导度斜率的变化和生理生化原因及其对干旱的响应规律，从而提高气孔导度模型在干旱条件下预测气孔导度的准确性。本项目将加强对气孔导度调节规律的认识；减小生态系统模型预测碳水通量的不确定性；有助于理解特定区域植被对环境的适应机制从而指导适应特定区域的物种或者品种选择和水分管理策略。

本项目以同一品种杨树为研究对象，通过测量和模型模拟，揭示不同林龄杨树气孔导度斜率的变化和生理生化机制，从而提高气孔导度模型模拟气孔导度的准确性。实验结果显示气孔导度斜率(m)不因树龄变化而改变。Farquhar模型模拟的杨树净光合速率与实测净光合速率数据吻合良好。气孔导度斜率反映植物气孔的调节策略，我们用单一的气孔导度斜率参数，模拟叶片气孔导度，模拟结果与实测数据吻合较好，而使用特定的不同林龄的气孔导度斜率并没有提高模型的准确性。依据实测数据参数化的BioCro模型可以显著提高生态系统模型模拟杨树生长的准确性。本项目加强了对气孔导度调节规律的认识并且有助于理解特定区域植被对环境的适应机制从而指导适应特定区域的物种或者品种选择和水分管理策略。本研究结果对于杨树人工林的可持续发展、引导未来相关研究、政策和管理方案的制定都将做出贡献。