Temporal and Spatial Distribution Patterns of Throughfall Under Eucommia ulmoides Forest

Throughfall under Eucommia ulmoides forest was measured from July 2004 to June 2005 at the Ecological Benefit Monitoring Station for Yangtze River Protection Forests.Over the whole measurement period,the volume of throughfall accounted for 72.5% of gross rainfall.Its maximum amount occurred in July 2004 and its maximum percentage relative to rainfall appeared in December 2004.Significant spatial variation in throughfall was observed below the canopy of E.ulmoides forest.The throughfall among different sampling sites differed significantly (p0.05) and its CV decreased with the increase of rainfall amount and intensity.The throughfall under canopy had an evident effect as an influx,for the throughfall at 50% of the sampling sites and 28.8% of the total rainfall took on a throughfall percentage bigger than 100%.In addition,the canopy characteristics influenced the spatial distribution of throughfall.There was a significantly negative correlation among canopy height,coverage and throughfall percentage.However,there was a significantly positive correlation between the throughfall percentage,and the distance from the sampling site to the nearest tree trunk and the branches' angle inclination.