Effects of Rainfall Size Class and Intensity on Canopy Interception of Pinus tabulaeformis Forest in the Qinling Mountains,China

The objective of this study was to understand how rainfall size class and rainfall intensity affect the canopy rainfall interception of Pinus tabulaeformis forest. Pinus tabulaeformis is the dominant tree species of a naturally generated secondary coniferous forest in mid-mountain zones in Qinling Mountains,China. Using the long-term observation methods,the precipitation,canopy interception,rainfall intensity,and meteorology were measured during the growingseason of each year from 2006 to 2008. The result showed that there was a discrete separation of wet and dry season,with the wet season lasting from May to October. Low-intensity rainfall events were frequent,but they accounted for a small amount of the total rainfall. Heavy storms occurred occasionally in this region. Mean annual rainfall interception ratio was 32. 9%,33. 0%and 33. 6% for 2006,2007 and 2008,respectively. On event basis,the minimum( maximum)interception ratio was 11. 0%( 64. 4%),11. 4%( 72. 5%),and 7. 8%( 74. 6%) for 2006,2007,and 2008,respectively. Canopy interception was a dynamic process,interception rates exist obvious variances under different rainfall class and rainfall intensity. Interception ratio decreased when the rainfall size class or rainfall intensity increased. For rainfall events with similar intensity,interception ratios decreased with rainfall increased under the same rainfall intensity,however canopy interception velocity increased with rainfall intensity increased under the same rainfall. The higher the mean interception velocities,the shorter the time of canopy come to saturate,when the rainfall was enough. The function of canopy interception will turn to weaken,accordingly with the interception loss close to saturated state gradually.