基于改进TVGM的水–碳耦合机制研究

提高植被的水分利用效率（water use efficiency, WUE）可以在一定程度上缓解水资源短缺，如何提高WUE依赖于对生态系统水–碳循环耦合机制的深入理解. 以北京森林站为例，基于时变增益模型（times variant gain model，TVGM)耦合光合作用–气孔导度模型与双源蒸散发模型，从WUE系数及气孔导度2方面研究水–碳耦合机制. 研究结果表明:不考虑水–碳耦合关系导致模拟蒸散发偏高、模拟总初级生产力偏大，气孔导度的增加抑制水分利用效率的提高，其抑制效应随气孔导度的增加趋于平稳；日退耦系数在夏季达到最大，年平均退耦系数为0.1左右. 在北京森林站群体水平上，相对于光合速率，蒸腾速率对气孔导度的下降较为敏感，导致WUE随气孔导度的下降而降低. 对北京森林站地区水–碳耦合机制的研究，可为其生态系统管理与调控提供依据. 

Water-carbon coupling mechanism on improved TVGM - case of Beijing Forest Station

Improving the water use efficiency of vegetation can alleviate water shortage to a certain extent. To improve vegetation water use efficiency, in-depth-understanding of water-carbon cycle coupling in the ecosystem is needed. Time-varying gain model was coupled to improved photosynthesis-stomata conductance and dual source evapotranspiration models, to verify accuracy of the coupled models on daily basis, and to investigate water-carbon coupling, taking into account water utilization efficiency coefficient and stomatal conductance. Simulated evapotranspiration and total primary productivity were found to be higher when water-carbon coupling was not taken into account. Stomatal conductance showed a complete negative correlation, then remained stable with increasing stomatal conductance. Daily decoupling coefficient reached maximum in summer, annual average decoupling coefficient was found to be 0.1. At the group level at Beijing Forest Station, relative to the photosynthetic rate, transpiration rate is more sensitive to the decrease in stomatal conductance. Water and carbon coupling mechanism in the Beijing Forest Station area should prove helpful for ecosystem management and regulation.