Management And Rehabilitation Mechanism Of Natural Forest In Huanglong Region On Loess Plateau

Huanglong mountains,a typical wooded regions,located in southeast Yah'an city,Shannxi province,China,and played important part in soil and water conservation,ecologicalenvironment,agriculture and industry on Loess Plateau.This wooded regions belonged toconiferous and broad-leafed forest vegetation containing some important species such as Pinustabulaeformis,Quercus wutaishanica and Betula platyphylla.Since 1998,the projection ofNatural forest protection and artificial forests by grain for green had been administed in China.Becouse of forbidding to cut all kinds of stands,the forest management was influenced,andthese policies leaded to a series of bad result such as outbreaks of diseases and insect pests.Thegoverment and scholars in growing numbes were beginning to complain the forest recourceswas wasted and not been utilized rationally.People had been disputing the result of forbiddingto cut forest although it's purpose was to protect forest.According to the principles of soil and water conversation,ecological and economicbenefit priority,on the basis of the current situation of forest resources and management,usedthe thoeries of population,community and the model of forest assessment,this paperanalysised the effect of the forest management in past 50 years on Loess Plateau.These resultsofreseach were as follows:1.The community of natural forest can be divided into three layers,such as tree,shrub andherb.The result showed that the interspecific association of these three layers were positive ingeneral,but the species in herb layer did not show a significant positive association.Thedominant populations existed independently in tree layer,but the interapecific associatin was atno siginificant level,and x² values implied that seven pairs of pecies such as Quercuswutaishanica and Pinus tabulaefomis,Pinus tabulaefomis and Acer ginnal,Acer ginnal andBetula platyphylla,Pyrus betulaefolia and Quercus wutaishanica,Pinus tabulaefomis,Acerginnal,Betula platyphylla had close relationship.The several indicators used together was aeffective way to measure the interspecific association.2.Using the method of gray relational analysis,we can carry out the estimation of theforest nature closeness,and resolve the key problems of applicatin of the thoery ofclose-to-nature forest mangement in China.This studies demonstrated that the different forestcommunity had the fifferent nature closeness,and evry forest community showed thesignificant diffirance in natral state and characteristics of community.these gray correlationdegree were separately 1.143 for P.tabulaefomis,1.085 for Q.wutaishanica,0.849 for B. platyphylla,0.893 for P.orientalis,0.789 for P.davidiana.It was estimated that P.tabulaefomis and Q.wutaishanica was the best forest types which had the higher graycorrelation degree and belonged to the climax community in Huanglong forest region,on thecontrary,P.davidiana was not stable.The others was developing to the climax community.3.The model of forest quality evaluation and the index system of assessment for forestquality was setted up.The research believed that the forest quality can be appraised byecological functions,the tendency of forest succession of community,the productivity ofwoodland,jamming,et al.The results indicated that the stand quality ofP.tabulaefomis was thebest,Q.wutaishannica and B.platyphylla were the better,and their mixed forest were theworst.4.The stocking volumn,biomass of shrub and herb in the undergrowth can be used toexpress the produtivity of forest.Stocking volumn of these xis types of forest were respectively113.09,51.07,61.08,92.72,104.37,and 40.24 m³Â·hm².The stocking volumn of p.tabulaeformis and it's mixed stand was the biggest,and there were significant fifferancebetween these six types of forest.The shrub occursed wildly and evenly in the stands of all kind of forest.The biomass ofshrub of 4.987t·hm^-2 was far outweigh the herb of 0.755t·hm^-2.The bimass of shrub wasdistributed in the plant organs such as trunks,branches,leaves and roots.5.Comparsing of the different forest operation programes in the past 50 yeas,the studyindicated that the effect of thinning was the best for p,tabulaeformis,all cutting was the worst.That fenced off for afforestation was the best for Q.wutaishannic and B.platyphylla.Thequality of forest fenced off for afforestation had been improving gradually.6.Four demonstration stands,40hm²,containing the thoery of closed-to-nature forest,were established in Huanglong forest region.In two yaers later,these stands that interferencetrees were cut were stable,the structure of these stands were reasonable than before,theproportion of domination tree and the content of rapidly available P in the soil of 0～20cm wasbeing increasing.Although the site of forest changed,diversity did not vary wildly.In brief,theeffect of application of close-to-nature forest management was obvious,and it illustrated agood prospect of application and extension of this thoery.This research was a systematized study on natural forest on Loess Plateau.Its findingsprovided a scientific foundation for natural forest protection,vegetation recovery and rationalutilization of land.