苹果三维树冠光能利用效率分布模拟

Simulation of Three-dimensional Distribution of Light Use Efficiency in Apple Canopy

为了模拟树冠内叶片光能利用效率(LUE)三维分布,构建了三维树冠净光合速率(Pn)和LUE耦合模型,LUE由Pn和光合有效辐射(PAR)比值求出。以27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PAR分布,并据2011—2012年测定数据拟合相关模型参数。模拟结果表明,当光合有效辐射低于约750μmol/(m2·s)时,树冠整体LUE随PAR的增加而增加,超过750μmol/(m2·s)后,LUE随PAR的增加而略有降低;LUE随空气CO2浓度和湿度的增加而增加。光照充足时[PAR=1500μmol/(m2·s)],从树冠底部到顶部,树冠整体LUE从0.02481mol/mol降低为0.01250mol/mol,降低了50%,树冠两侧和内膛的差异不到10%。在一天当中苹果树冠LUE整体呈双峰曲线,晴天的LUE比阴天高22.7%,约为0.01148mol/mol。研究显示,该模型可模拟出不同环境条件下苹果三维树冠LUE的三维分布和日变化。

A coupled model of photosynthetic rate （P n ） and light use efficiency （LUE） were developed to simulate the three-dimensional distribution of LUE in apple canopy. For convenience, LUE was expressed as the ratio of net P n to photosynthetically active radiation （PAR）. The experiment was conducted in a ‘ Fuji ’ apple （Malus domestica Borkh. cv. ‘ Fuji ’ ） orchard during the 2011-2012 growing seasons. The simulation was shown that： LUE increased rapidly with increasing CO 2 concentration and humidity. LUE consistently increased with the increase of PAR when PAR was below 750 μmol/（m 2 · s）. And it decreased with the increase of PAR when PAR excessed 750 μmol/（m 2 · s）. When canopy height increased from bottom to upper canopy, LUE decreased by 50% from 0.02481 mol/mol to 0.01250 mol/mol with no more than 10% difference between the sides and the inner part. The diurnal course of LUE in the canopy showed a double-peak curve on clear day. The average LUE on clear days were 0.01148 mol/mol which were about 22.7% higher than cloudy days. The study indicated that： the sensitivity of LUE to microclimatic factors could be systemically assessed by the coupled model.