果树冠层水分利用效率分布模型构建

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

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(Tr)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2.61 mmol·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2.82 mmol·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。

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.