祁连山青海云杉林冠降雨再分配特征及影响因素

以祁连山排露沟小流域青海云杉林为研究对象,2015年5—9月观测了34场降雨的林外降雨量、穿透雨量和树干茎流量,并同步观测了相关的林外气象因子,分析了青海云杉林冠降雨再分配特征及影响因素。结果表明:(1)青海云杉林的总穿透雨量、树干茎流量和截留量分别为275.9,1.8,90.0mm,分别占总降雨量的75.04%,0.48%和24.48%,并在不同降雨量等级之间存在差异。(2)冠层降雨再分配各组成要素(穿透雨、树干茎流、林冠截留)与降雨量、降雨历时、10min最大雨强、空气相对湿度呈极显著的相关性。随着降雨量和降雨历时的增大,穿透雨量和树干茎流量均不断增大,而穿透雨率、树干茎流率和截留量(率)均逐渐趋于稳定。(3)青海云杉林内产生穿透雨和树干茎流的临界降雨量分别为0.8mm和9.6mm。因此,气象因素是影响冠层降雨再分配的重要因素之一。

Rainfall Canopy Partitioning and Its Influencing Factors of Picea crassifolia Forest in Qianlian Mountains

Rainfall was partitioned into three parts through the vegetable canopy: Throughfall, stemflow and interception. This process played a determining role in water balance for forest stands and in regulating processes of this mountainous region. In present study, the experiment was carried out in Pailugou watershed in Qilian Mountains, in the arid region of Northwest China. In a 96-year-old Picea crassifolia forest stand, throughfall, stemflow and canopy interception of 34 rain events were observed from May 1 to September 31, 2015. Meanwhile, the related meteorological factors, including air temperature (T), air relative humidity (Rh) and precipitation (P) were simultaneously monitored by an automatic meteorological station in the outside forest. Then, we analyzed the characteristics of rainfall canopy partitioning and their influence factors. The results showed that: (1)During the total observation period, the total throughfall, stemflow and interception of Picea crassifolia forest were 275.9, 1.8 and 90.0 mm, and accounted for 75.04%, 0.48% and 24.48% of the total atmospheric precipitation, respectively. Meanwhile, their ratios varied significantly under different rainfall grades. (2)The three parts of rainfall canopy partitioning were significantly correlated with rainfall, rainfall duration, maximum rainfall intensity in 10 minutes and relative air humidity. With the increase of rainfall and rainfall duration, throughfall and stemflow would constantly increase and their ratios would become more and more stable. (3)The critical rainfall amounts for the occurrence of throughfall and stemflow were 0.8 mm and 9.6 mm respectively. Therefore, we concluded that meteorological factors were the important factors of rainfall canopy partitioning.