果树冠层水分利用效率分布模型构建

为模拟树冠内叶片瞬时水分利用效率（WUEI）的三维分布，构建了三维树冠净光合速率（Pn）和蒸腾速率fir）的耦合模型。该模型利用c3植物叶片光合生化模型和Penman—Monteith公式计算Pn和Tr，而WUEI是根据Pn和Tr比值求出。以22年生开心形“富士”苹果树（Malus domestica Borkh．cv．Fuji）为试材，通过实测确定三维树冠内叶片和辐射分布，并据2007—2008年测定数据拟合相关模型参数。模拟结果表明，从苹果树冠顶部到底部WUEI从3．96mmol·mol^-1降到2．61mmol·mol^-1，只下降了34％，树冠两侧和内膛的差异不到5％。在一天当中苹果冠层WUEI整体呈双峰曲线，晴天的WUEI比阴天高28％，约为2．82mmol·mol^-1研究表明，该模型可模拟出苹果冠层WUEI的三维分布和日变化。

The Model of Efficiency on Using Water in Canopy of Fruit Tree

A coupling model of photosynthetic rate （Pn） and transpiration rate （Tr） was developed to simulate the three-dimensional distribution of leaf instantaneous efficiency of using water （WUEI） in apple canopy. The leaves Pn and Tr were calculated by the C3 photosynthesis model and Penman-Monteith equation. For convenience, WUEI is expressed as the ratio of net Pn to Tr. The experiment was conducted in a ＇ Fuji＇ apple （Malus domestica Borkh. cv. ＇Fuji＇ ） orchard during the 2007-2008 growing seasons. When canopy height decreased from upper to bottom canopy, WUEI decreased by 34% from 3.96 mmol·mol^-1 to 2.61 mmol·mol^-1 with no more than 5% difference between the sides and the inner part. The diurnal course of WUEI in the canopy showed a double-peak curve on clear day. The average WUEI on clear days was 2.82 mmol·mol^-1 which was about 28% higher than cloudy days. The study indicated that the sensitivity of WUEI to microclimatic factors and can be systemically assessed by the coupling model.