A Study on Rainfall Regulation and Holding Capacity of Forest Land in Jiulong Mountain, Beijing

The rainfall regulation and holding capacity of the forest canopy,litter andsoil in Jiulong Mountain were studied. The results showed that:mean annual rainfall interception rate of forest canopy in 25-year-old artificial plantation of Pinus tabulaeformis Carr.and Platycladus orientalis(L.)Franco is about 22%～32%; the mean interception rateof heavy rain storm 7%～10%,The effective amoun of retention by litter 0.46～2.42 mm.The capacity of regulation and rainfall holding of soil horizon could be classified into 3 categories:fast,slow and changed regulation.Among them,the fast regulation amount is between 35～48 mm,the slow regulation amount 54～48 mm,and the changed regulation amount 28～52 mm.The sum of the three is called as the effective amount of regulation and holding,which is between 103～141 mm,It is clear that the soil horizon posseses the greatestcapacity.Although the annual amount of rainfall regulation of the forest canopy is ratherlarge,its regulation amount to heavy rainstorm accounts for only 10% of the total.