Studies On Influence And Distribution Of Precipitation By Different Karst Forest Types In Guizhou Provincial Center

Through the method of "investigation of the field tree vegetation types plots and location research of the fixed tree vegetation types plots" and "investigation in the open country and analysis in the room",based on the elementary theory of Ecology, Environmental Engineering and Forestry, the research about precipitation being assigned and influenced by different forest types in karst mountainous area in Guizhou Province center has been completed to indicate:Max water holding capacity of soil-forest system ranges from 71.253mm to 616.230mm,and the extreme value range is 27.044～757.972mm,and the average value is 214.661mm and soil layer accounts for 96.38%.Change tendency of max water holding capacity is that in litter layer > that in tree layer > that in grass layer > that in shrub layer aboveground forest.The average value of max water holding capacity accounts for 20.57% of the annual precipitation.The annual average runoff value is 11.108mm and ranges from 1.765 to 22.934mm,and the change model in different soil-forest system types is that in newly young forest > that in coniferous forest > that in needle and broadleaved mixed forest > that in broadleaf forest,and the relative variables values are 22.934mm, 17.236mm,10.770mm,8.876mm.The monthly runoff depth accounts for 0.514～2.079% of the monthly precipitation.Annual total precipitation models in horizontal level is total precipitation in openland > that out karst forest >that in karst forest > that under layer of shrub and grass, and the relative variables values are 1043.67mm,964.68～996,43mm,898.75～989.22mm,445.99～603.81mm.Interception models in vertical level is Evapotranspiration and other > interception in shrub and grass layer>canopy interception>runoff at ground and from soil,and the corresponding ratios with precipitation in open area are 40.95～56.73%,36.93～46.58%,4.27～10.36%,2.07～2.11%.Except canopy interception,annual change models of other interception and precipitation parts are high in summer and low in winter.Monthly change models of the density of NO₃^-,NH₄⁺,K⁺,Ca²⁺,Mg²⁺,SO₄^2-,Na⁺,and Cl^- along with precipitation mobile,are low in summer and high in winter. Along the route as precipitation out karst forest→precipitation in karst forest→runoff at ground→runoff from soil→ streamflow,ions used by density indicator in water analyzed in this project are divided into 3 types:â‘ Sustainable collecting types, the ion density is sustainable increasing from precipitation out karst forest to streamflow,include Ca²⁺,Mg²⁺;â‘¡Collecting at ground types,the ion density is increasing from precipitation out karst forest to ground and decreasing from ground to streamflow, include K⁺,Na⁺,Cl^-,NO₃^-,and NH₄⁺; (3) Another types, the ion density is changing irregularly, include SO₄^2-.The annual input quantity of N along with precipitation is 9.479～12.692 kg/hm².a,and the losses along with runoff at ground and from Ocm to 90cm soil is 0.452～0.727kg/hm².a,and the net increased value is 9.027～11.965kg/hm².a,and accounts for 0.08～0.10% of the total quantity of forest-soil system.The relative variables values of K are 12.749～19.557kg/hm².a,1.701～4.670kg/hm².a,8.071～17.856kg/hm².a,0.01%.The relative variables values of Ca are 50.800～84.064kg/hm².a,10.103～12.939kg/hm².a,40.697～71.125kg/hm².a,0.39～1.29%.The relative variables values of Mg are 9.712～16.287kg/hm².a,1.590～3.439kg/hm².a,8.122～12.848kg/hm².a,0.00～0.03%. The annual input quantity of N,K,Ca,Mg,and so on along with precipitation is a small value of the total quantity of forest-soil system, high efficiency and Fluidity,and has an important ecology significance to forest growth and nutrient circulation of forest land.