中国北方树木秋季物候的过程模拟及其区域分异归因

揭示温带落叶树木秋季物候的发生机理对提高生态系统固碳量和植被生产力的预估精度具有重要意义。该研究利用低温和光周期乘积模型模拟了1981-2014年中国北方温带90余个站点6个树种的叶始变色期和落叶末期, 并对逐站点-物种的最优模型进行了模拟精度评价, 分析了最优模型模拟精度的时空差异及其随水分梯度的空间变化。主要结果如下: (1)在诱导叶片衰老方面, 光周期缩短的影响通常大于温度降低的影响。据此建立的叶始变色期和落叶末期最优模型模拟的平均均方根误差分别为6.9 d和6.0 d, 模拟与观测时间序列呈显著正相关关系的比例分别为71.4%和83.6%; (2)最优模型对区域平均和多年平均叶始变色期和落叶末期模拟的绝对误差小于2.4 d, 但模拟日期的时空变幅通常小于观测日期, 这与秋季物候发生日期的高度时间变异性密切相关; (3)水分条件在一定程度上影响叶片衰老诱导途径的选择, 表现为光周期缩短诱导叶片衰老的叶始变色期最优模型所占比例在干旱和半干旱区大于湿润和半湿润区, 而最优模型的模拟精度在湿润和半湿润区高于干旱和半干旱区。该研究验证了低温和光周期乘积模型在中国温带地区的适用性, 并揭示了水分条件对秋季物候发生机理和模拟精度的影响。

Process-based simulation of autumn phenology of trees and the regional differentiation attribution in northern China

Aims Revealing occurrence mechanisms of autumn phenology in temperate deciduous trees is of vital importance for improving estimation accuracies of ecosystem carbon sequestration and vegetation productivity. This study aimed to uncover the mechanisms of leaf senescence in response to environmental changes and simulation accuracies of autumn phenology through process-based models, and further investigate impacts of water conditions on leaf senescence mechanisms and simulation accuracy of autumn phenology.