苹果三维树冠光能利用效率分布模拟

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750 μmol/(m2?s)时，树冠整体LUE随PAR的增加而增加，超过750 μmol/(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=1500 μmol/(m2?s)]，从树冠底部到顶部，树冠整体LUE从0.02481 mol/mol降低为0.01250 mol/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0.01148 mol/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。

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

A coupled model of photosynthetic rate (Pn) 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 Pn 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 CO2 concentration and humidity. LUE consistently increased with the increase of PAR when PAR was below 750 μmol/(m2?s). And it decreased with the increase of PAR when PAR excessed 750 μmol/(m2?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.