Effects Of Quercus Aliena Var.acuteserrata, Pinus Tabulaefoemis And Pinus Armandii On Rainwater Quality In The Southern Slope Of Qinling Mountain Range

The southern slope of Qingling Mountain Range where the condition of water quality has important effects on diversion water quality and water diversion project is the main water source for the Middle Route Project of South-to-North Water Diversion. Forest has the ability to conservate water and regulate, purify and steady to the water quality. The forest area of the southern slope of Qingling Mountain Range accounts for 40% of the total area, whose effects on the water quality are that people are concerning with. The Huoditang forest area is situated in the center of the middle southern slope of Qingling Mountain, where forest vegetation is a good representation. Therefore, we choose this forest region to conduct some integrated research on forest water quality. Based on the main forest stands in Qinling Mountain Range, according to the spatial sequence of rainwater through forest ecosystem , Quercus aliena var.acuteserrata, Pinus tabulaeformis and Pinus armandii in Huoditang forest region were collected to study these effects and mechanisms on rainwater quality with methods of comparative analysis and comprehensive evaluation. The results showed that:(1) The canopies, litter layers and soil layers of Quercus aliena var.acuteserrata, Pinus tabulaeformis and Pinus armandii all played a role in reducing rainwater acidity. The key layer of Pinus tabulaeformis was the soil , the key layer of Quercus aliena var.acuteserrata and Pinus armandii was the litter. The whole sequence was Pinus tabulaeformis>Pinus armandii>Quercus aliena var.acuteserrata.(2) The key layer of Quercus aliena var.acuteserrata, Pinus tabulaeformis and Pinus armandii of absorbing and fixing SO₄^2-,NO₃^-,NH₄⁺,PO₄^3- in rainwater was soil . As far as the effect of soil layer, Pinus tabulaeformis was the best in three forests. As to fixing NO₃^-,NH₄⁺ in rainwater, Pinus armandii had the best effect, as for fixing PO₄^3- in rainfall, Pinus tabulaeformis had a better effect.(3) Both Quercus aliena var.acuteserrata and Pinus armandii had better effect on absorbing Cu in rainwater. Quercus aliena var.acuteserrata had the best effect on reducing the concentration of Zn in rainwater, its canopy, litter and soil layer all had intensive effect on sorbting and intercepting Zn in rainwater.(4) The key layer of intercepting and purifing Pb,Cd,Cr in rainwater was canopy. The canopies of Quercus aliena var.acuteserrata, Pinus tabulaeformis and Pinus armandii had the effect, the three litters and the soil of Quercus aliena var.acuteserrata played an important role in sorbting and fixing Cr, the litter of Pinus tabulaeformis and the deep soil of Pinus armandii could absorb Pb strongly, the litter of Quercus aliena var.acuteserrata and the soil layer of Pinus tabulaeformis could absorb Cd stronger.(5) The canopies and litters of three forests all had effect on desorbing Al, but the deep soil of Quercus aliena var.acuteserrata had effect on absorbing and intercepting Al.(6) The water quality of rainwater was the worst, in three inner precipitations, the water quality of Pinus tabulaeformis was the best, in the litterthroughs, the water quality of Quercus aliena var.acuteserrata was the best. The water quality of interflows in the A layer soils, Pinus tabulaeformis was the best. The interflows in the B layer soils, the water quality of Quercus aliena var.acuteserrata was the best. Quercus aliena var.acuteserrata had the optimum effect on improving water quality.(7) The main monitoring indexs of forest water in the southern slope of Qingling Mountain Range should be pH,SO₄^2-,NH₄⁺,Pb,Al,Cd,Zn.