哀牢山常绿阔叶林林冠的截留特征

为了评估亚热带常绿阔叶林的水源涵养服务功能，选择哀牢山典型的原始常绿阔叶林，定位监测了林冠层对1a中共144次降雨的截留分配效应。观测期间降水总量为1707．8mm，穿透雨量、茎流量和林冠截留量分别是1421．8，15．4和270．6mm，穿透雨率、茎流率和截留率分别为83．3％，0．9％和15．8％。总降雨量大于3．7mm时才观测到林内牙透雨和树干茎流，“漏斗”状的林冠结构和持续的降雨，均可造成穿透雨量大于林外大气总降水量，而树木较大分枝角度和较多附生物，可能使有些胸径和冠幅较大树木的树干茎流量反而更小：穿透雨量和茎流量、林冠截留量与降水量均呈显著的线性正相关（P〈0．01），而林冠截留率随降水量增大而减少；降雨特征和林分特征是影响林冠截留的主要因素。

Interception capability in an evergreen broad-leaved forest of Ailaoshan, Yunnan Province

An experiment was conducted in the evergreen broad-leaved forest （the primitive tree species were Coatanopsis wattii and Lithocarpus xylocarpus） of Ailaoshan, Yunnan Province to evaluate its water interception capability and accumulate basic data for forest hydrology. A total of 144 precipitation events from May 2005 to May 2006 were monitored, and a correlation analysis was used to determine the redistribution and interception effects of the tree canopy on precipitation. The total of 1 707.8 mm of precipitation, consisted of throughfall, 1 421.8 mm （83.3%）; stemflow, 15.4 mm （0.9%）; and canopy interception, 270.6 mm （15.8%）. However, throughfall and stemflow could only be recorded when precipitation was over 3.7 ram. A “funnel” shaped canopy structure and duration of rainfall sometimes caused recorded rainfall to be greater than real precipitation; meanwhile a low stemflow of tree with greater diameter at breast height and crowns sometimes resulted from large branch angles and lots of epigrowth. Total throughfall, stemtlow, and canopy interception were positively correlated （P 〈 0.01） with precipitation, whereas the canopy interception rate was negatively correlated （P 〈 0.01） with precipitation. Thus, precipitation and forest structure mainly determined interception capability.