华北落叶松冠层平均气孔导度模拟及其对环境因子的响应

冠层气孔导度是生态水文学研究中的一个重要参数,研究其对环境因子的响应,能为建立机理性的森林蒸腾模型提供理论依据.本文利用热扩散探针,于2005年5-9月,测定了六盘山叠叠沟小流域华北落叶松人工林树干液流及其同步的环境因子,计算了林分冠层平均气孔导度(gc)并构建了Jarvis形式的冠层平均气孔导度模型,分析了gc对光合有效辐射(PAR)、空气水汽压亏缺(DVP)和土壤相对有效含水率(REW)的响应.结果表明:该模型能有效地计算gc的日变化特征,计算与观测的gc决定系数R2为0.76 (n=952).gc对各环境因子有不同响应关系,并表现为非线性特征.其中PAR是gc的驱动因子,当PAR＜0.35 mmol·m-2·s-1时驱动作用明显,大于此值则驱动作用变小；DVP是gc的限制因子,随着DVP的增加gc降低；REW=41%是gc对土壤水分响应的一个关键阈值,当REW＞41%时,土壤水分对gc的影响较小,当REW＜41%时,土壤水分则成为gc的限制因子.

Simulations of Larix principis-rupprechtii stand mean canopy stomatal conductance and its responses to environmental factors.

Canopy stomatal conductance is an important parameter in eco-hydrological studies.To understand its responses to environmental factors can offer theoretical basis for developing mechanism-based models of forest transpiration.In this paper,Granier's probe was adopted to measure the sap flow of a Larix princips-rupprechtii stand in a small watershed of Diediegou in northern part of Liupan Mountains from May to September 2005,and the related environmental factors were simultaneously observed.The canopy transpi...