Water Conservation Function And Individual Rainfall Distribution Characteristics Of Typical Forest Stand In Beijing Mountainous Area

Water conservation of forest vegetation is one of the most important ecological service functions.There are different conservation functions among different forest types.To explore the difference of water conservation function among different forest types,three forest types(shrubs,Quercus variabilis,Pinus tabuliformis)were selected as the research objects.Water-holding performance of litter and soil,and soil physical and chemical properties were analyzed and compared.Combined with the effective storage capacity and the maximum storage capacity,the ability of water conservation was quantitatively compared.Taking an event of rainfall as an example,the vertical distribution characteristics of rainfall among the three forest stands were analyzed by hydrogen and oxygen isotope technology.This research would provide reference basis for the ecological service function of forests in this area.The results showed as follow.(1)The litter accumulations and water holding capacities of the three stands were different.The total litter accumulations of three stands were 12.13～18.86 t/hm~2.The maximum water holding capacity,effective sequestration and maximum sequestration of three stands were 12.76～32.28 t/hm~2,11.65～53.89 t/hm~2and 13.70～63.44 t/hm~2,respectively,which showed the largest for Quercus variabilis and the smallest for shrubs.(2)The mean values of soil bulk density were 1.21 g/cm~3of Quercus variabilis,1.48g/cm~3of shrub,and 1.59 g/cm~3of Pinus tabuliformis Carrière,respectively,which were significantly different.The total porosity,natural water storage capacity,maximum water holding capacity,minimum water holding capacity,and capillary water holding capacity of soil decreased with increasment of soil depth.(3)Effective storage capacities of forest including litter layer and soil layer(0～80 cm)were 1994.45 t/hm~2,1962.14 t/hm~2,and 1389.60 t/hm~2,respectively for Quercus variabilis,Pinus tabuliformis,and shrub.Effective storage capacity of Quercus variabilis was 1.44times that of shrub.Maximum storage capacities of Quercus variabilis,shrubs,and Pinus tabuliformis were 3311.60 t/hm~2,3088.98 t/hm~2,and 2907.61 t/hm~2,respectively.Maximum storage capacity of Quercus variabilis was 1.13 times of that of Pinus tabuliformis.(4)Under an event of rainfall,the redistributions of rainfall were different among three forest stands.Total rain penetration rates of Pinus tabuliformis,Quercus variabilis,and shrub were 43%,33%,18%,respectively.Total tree stem flow rate of Quercus variabilis and Pinus tabuliformis were 16%and 2%.And total canopy interception rate of shrub,Pinus tabuliformis,and Quercus variabilis were 82%,55%,and 51%,respectively.Moreover,litter water-holdings of Quercus variabilis,Pinus tabuliformis,and shrub were22%,14%,and 6%,respectively.Soil water-holdings of Pinus tabuliformis,Quercus variabilis,and shrub were 31%,27%,and 12%,respectively.(5)Under this event of rainfall,the isotopic values of topsoil(0-10 cm)water in three forest stands were greatly affected by the event of rainfall.With the increase of soil depth,the influence of rainfall on soil water decreased.To sum up,the forest stand with the strongest water conservation capacity in the litter layer and the soil layer was Quercus variabilis,followed by Pinus tabulaeformis,and the shrub.Therefore,Quercus variabilis can be planted priority in water conservation forest construction and ecological restoration.