两种温带落叶阔叶林降雨再分配格局及其影响因子

林冠对降雨的再分配是森林生态系统的重要生态水文过程,影响着生态系统生物地球化学循环。于2012年5—10月连续测定帽儿山森林生态站的两种温带天然次生林型——蒙古栎林和杂木林的林外降雨、穿透雨及树干径流,旨在量化其降雨再分配过程及其影响因素。结果表明:蒙古栎林的平均穿透雨、树干径流、林冠截留分别占同期林外降雨的76%、7%和17%;杂木林分别占85%、5%和10%。根据模型估算,当降雨量分别超过1.0mm和0.7mm时蒙古栎和杂木林开始出现穿透雨;当降雨量超过3.0mm开始出现树干径流。当降雨量超过5.6mm,树干径流体积会随着树木胸径的增加而显著增加;而当降雨量低于5.6mm则出现相反趋势。穿透雨、树干径流及林冠截留的绝对量均随降雨量的增大而显著增加,但其占降雨量的比例却表现出不同的变化趋势。穿透雨量的空间变异随降雨量和降雨强度的增大显著减小。两种林型的降雨再分配格局因受降雨量、降雨强度等降雨特征和林冠结构的影响而产生差异。

Rainfall redistribution patterns and their influencing factors of two temperate deciduous forests

Rainfall redistribution in a forest is an important ecohydrological process that influences the biogeochemical cycling of the ecosystem. The purpose of this study was to investigate rainfall redistribution patterns and its influencing factors in two temperate deciduous forests in northeastern China. The forest types were Mongolian oak (Quercus mongolica Fisch.) forest and mixed deciduous forest (i.e., no dominant tree species). We continuously measured the rainfall, throughfall and stemflow of the two stands during the growing season (from May to October of 2012). The mean rates of throughfall, stemflow, and interception to rainfall for Mongolian oak forest were 76%, 7% and 17%, respectively; while those for the mixed deciduous forest were 85%, 5% and 10%, respectively. Throughfall occurred when the rainfall exceeded 1.0 mm and 0.7 mm for the Mongolian oak and mixed deciduous stands, respectively. Stemflow occurred when the rainfall exceeded 3.0 mm for both stands. The stemflow volume increased significantly with DBH increasing when the rainfall exceeded 5.6 mm, but an opposite trend occurred when the rainfall was below this threshold. The amount of throughfall, stemflow and interception all increased significantly with rainfall increasing, while their rates to rainfall showed different trends. The spatial variability in throughfall decreased significantly with the amount and intensity of rainfall increasing. We concluded that the rainfall redistribution patterns of these two stands varied as a result of the differences in their canopy structure and responses to various rainfall characteristics (i.e., rainfall amount, rainfall intensity).