华北油松人工林冠层穿透雨空间变异性研究

Spatial variability of throughfall in forest canopy layer of Chinese Pine(Pinus tabulaeformis) plantation in Northern China

为说明林冠截留的空间分布特征,揭示其空间异质性,采用网格状机械布设采样点测定穿透降雨量。结果表明:穿透雨的变异系数随降雨量和降雨强度的增加而减小,当冠层达到饱和后变异系数趋于一稳定值,接近林冠叶面积指数的变异系数0.18。认为冠层叶面积指数的变异系数是穿透雨量变异系数的极限值。由于油松针叶的特殊排列方式,并且下层枝干下垂引起林冠截留负值,出现林冠截留负值的穿透雨样本占总样本数的13%,其中最大超出林外降雨高达70%。

The interception of rainfall by vegetation and the subsequent evaporation of intercepted water from canopy surface play an important rule in hydrological processes, water and energy balance of forest ecosystem. Spatial variability of interception has different effects on runoff yield from watersheds located in different climatic and biome regions. In order to indicate spatial distribution characteristics of interception, rain-gauges were installed by grid-sampling method to measure throughfall. Results show that the coefficient of variation （Cv） of throughfall tends to be declined as rain intensity increases. After canopy is saturated, Cv of throughfall was remained at a constant value, which is close to the Cv of leaf area index（LAI） value 0.18. So the Cv of LAI is regarded as extreInum of that of throughfall. Because of the special characteristic of Chinese pine （ Pinus tabulaeformis）, and the lower droopy branches, negative values for interception account for 13% of the total samples, thereinto the max is above 70% of gross rainfall.