Effects Of Forest Soil And Thinning On Water Quality Of Pinus Armandii And Pinus Tabuliformis On South Slop In Qinling Mountains

The South-to-North Water Diversion Project is a major strategic project to solve thenorthern water shortage in China (including the eastern, central and western route). Themiddle line of the Project will take water from Danjinagkou Reservoir, and the water sourcearea are the South slope of Qinling Mountain which mostly covered by forests. Forestvegetation in the area is mainly natural forests or plantations that recovered after harvesting orvandalism in the sixties and seventies of the20th century. After fifty years of natural growth,forest growth is limited and regeneration was slow down, so the forest needed thinning. ButQingling forest is mainly the water-sourse forest, and effects of thinning on runoff waterquality is unclear. There is a certain acid rain phenomenon at the same time in Qinling region,and abundant reserves of Pb and Zn. The pollution of Heavy metals in Pb and Zn Mining haveserious threat to water quality, and the soil is the most important level that have influence onwater quality effects of forest ecological system, so the effects of forest soil and thinningintensity on water quality is urgent which needs to study in medium-altitude mountains region.Therefore, the study not only has important theoretical significance on the effective quality ofthe water in correct evaluation of forest ecological system, but also has important practicalvalue to South-to-North Water Diversion Project forest management and construction.This study investigates the effect of soil on water quality in mixed pine-oak, Pinusarmandii, Pinus tabuliformis and Quercus aliena var. Acuteserrata by simulating the rainfallwith different pH and different concentration of heavy metals leaching soil column indoors,which obtaines two kinds of forest types that relatively good for water quality. According tothe atmospheric precipitation and forest ecosystem interaction space order, adopting themethod of comparison and analysis on water quality change in different thinning intensityPinus armandii and Pinus tabulaeformis forest canopy and litter layer, which deterMines thepurification effect of the best tree species and the thinning intensity. Research mainly drawthe following conclusion:1) The heavy metal of rainfall through the pine oak forest, Pinus armandii, Pinustabuliformis and Quercus aliena var. Acuteserrata shows as follows: With different massconcentration of heavy metals in rainfall, the soil both had desorption and adsorption role for Cd, Pb and Zn in rainfall. The mass concentration of heavy metal in rainfall is low, thereappears main soil desorption effect; While at high mass concentration of heavy metals inrainfall, soil is mainly for adsorption.In four Forests soil, Pinus armandii and Pinustabuliformis forest soil purification of heavy metals in rainfall is relatively stronger.2) Pinus armandii and Pinus tabuliformis forest canopy and litter layer has raise effect onpH of rainwater, and all levels tending to increase pH of rainwater with the intensity decreases.The raised effect of Canopy on pH is Pinus armandii> Pinus tabuliformis and litter layer isPinus armandii <Pinus tabuliformis.3) Pinus armandii forest canopy are adsorption on NO3-and NH4+from rainfall, andreduce with increased of thinning intensity. Leaching PO43-in rainfall, and also reduce. Pinustabuliformis forest canopy was adsorption on NO3-, NH4+and PO43-from rainfall, and reducewith increased of thinning intensity. Pinus armandii and Pinus tabuliformis forest canopy andlitter layer on NO3-, NH4+and PO43-were leaching. Net leaching amount of NO3-, NH4+andPO43-is Minimum on the10%of thinning intensity litter layer.4) Pinus armandii and Pinus tabuliformis forest canopy have effect of leaching on K andMg and adsorption on Na and Ca. With the increasing of thinning intensity, leaching amountof K first decrease and then increase, and is Minimum in10%thinning intensity. Leachingamount of Mg first increase and then decrease, and is Maximum in5%thinning intensity.Adsorption amount of Na and Ca decreased after increasing, and Na is Minimum in5%thinning intensity, Ca is Maximum in5%of Pinus armandii and10%of Pinus tabuliformis.Pinus armandii litter layer is leaching on K, Ca and Mg, while Na has some adsorption. Withincreasing of thinning intensity, net leaching amount of K, Ca and Mg reduction. Netadsorption amount of Na in litter layer first decrease and then increase, and Minimum in10%thinning intensity. Pinus tabuliformis litter layer are leaching on K, Na, Ca and Mg. Withincrease of thinning intensity, the net leaching amount of K and Na first increase and thendecrease, and is Minimum in15%, while the net leaching amount of K and Na decrease.5) Pinus armandii and Pinus tabuliformis forest canopy have effect of leaching on Cu, As,Pb and Cr, and adsorption on Cd. With the increase of thinning intensity, leaching amount ofCu and As first increase and then decrease, and is Maximum in10%thinning intensity.Leaching amount of Pb and Cr first increased and then decrease and then increase, and isMaximum in5%thinning intensity while Minimum in15%. Adsorption amount of Cd firstincrease and then decrease, and is Maximum in10%thinning intensity. Pinus armandii andPinus tabuliformis litter layer is leaching on Cu, As, Pb, Cr and Cd. With the increase ofthinning intensity, net leaching amount of Cu decreased. With the increase of thinningintensity, net leaching amount of As from Pinus armandii increase, while first decrease and then increase from Pinus tabuliformis and is Minimum in15%. Net leaching amount of Pbfrom Pinus armandii decrease, while first increasing and then decreasing from Pinustabuliformis and is Maximum in15%. Net leaching amount of Cr and Cd first increase andthen decrease from Pinus armandii and is Maximum in10%, while first decrease and thenincrease from Pinus tabuliformis and is Minimum in15%.6) Pinus armandii and Pinus tabuliformis forest canopy has leaching effect on Al and Zn.With the increase of thinning intensity, net leaching amount of Al and Zn first increase andthen decrease. Net leaching amount of Al is Minimum in10%, and Zn is Minimum in15%.Pinus armandii and Pinus tabuliformis litter layer was leaching on Al and Zn. With theincrease of thinning intensity, net leaching amount of Al was not clear in Pinus armandiiwhile increasing in Pinus tabuliformis, and net leaching amount of Zn increased in Pinusarmandii and Pinus tabuliformis.7) The water quality effect of Al and Zn are the best without cutting, and the role of Al isbetter than that of Zn.