The Study On Growth Characteristics And Close-to-nature Management Techniques For Larix Principis-rupprechtii Artificial Forests In Intermediate Section Of Qinling Mountains

18－48years Larix principis-rupprechtii artificial forests in intermediate section ofQinling Mountains(xunyangba forest range of ningdong forestry bureau in shaanxi provinceand huoditang forest farm of Northwest A＆F university) as the research object, by set27typical sample plots and cut81sample trees，to study the growth process，biomass andproductivity by stem form and stand biomass respectively.and combined with communitysuccession to explore management strategies for Larix principis-rupprechtii artificial forestsin intermediate section of Qinling Mountains and compiled homologous close-to-naturemanagement techniques，to effectively improve stand quality and increase forest growth forLarix principis-rupprechtii artificial forests in intermediate section of Qinling Mountains.theresults show that:(1) Optimized Richards curve as growth forecast model of diameter at breast height、tree height and volume for Larix principis-rupprechtii artificial forests in intermediate sectionof Qinling Mountains. Appropriate equations respectively as follows:Annual increment of diameter at breast height formed a peak in10th year（0.864cm），average increment of diameter at breast height formed a peak in15th yea（r0.374cm），annualincrement equal to the average increment (about0.76cm) in17th year. At10years, theannual increment of tree height and average annual growth have reached growth peak (0.919cm,0.874cm);13years, the tree height year after year and equal to the average annualgrowth (about0.82m), annual increment of tree height equal to average increment (about0.76cm) in17th year. annual increment of Volume formed a peak(0.0133m3) in25th year,average increment formed a peak(0.0091m3)in40th years,at the same time, annualincrement of volume equal to average increment (about0.0091m3) in40th year and reached quantitative maturity.Diameter at breast height, tree height and volume at low elevation areais superior to the high altitude; Low altitude area, quantitative mature age is44years;andquantitative mature age is39years in high altitude area.(2) Accorded to biomass measurement data of sample trees for Larixprincipis—rupprechtii artificial forests, to discuss organ biomass distribution of individualtree, selected both W=aDb�'�W=a(D2H)bcommon growth model respectively to establishbiomass prediction model. The biomass of Larix principis—rupprechtii Artificial forests inorder of size of the components are: trunk＞root＞leaf＞branch＞bark. Withdifferent age of Larix principis—rupprechtii artificial forests, stand density is low. Volumeand biomass as the stand ages increased steadily. Biomass of arbor layer of Larixprincipis—rupprechtii artificial forests had the highest proportion,98%of the communitybiomass, proportion of biomass in shrub layer and herb layer is very small.the order ofbiomass accumulation for the net productivity of different organs of Larixprincipis—rupprechtii was trunk、leaves、root、 branches, bark.In all different stages offorest age, the average proportion of the net productivity of different organs of the totalproductivity: trunk (57.56%)> leaves (23.62%)> root (8.45%)> branches (6.26%)>bark (4.11%). with stand age increasing，total net productivity of different age Larixprincipis—rupprechtii community presented a tendency to increase after drop.(3) By analyzed the succession tendency of Larix principis—rupprechtii Artificial forestsin mid-low elevation and med-high elevation districts respectively to study the homologousmanagement strategies. The results showed that: The tendency of Larix principis—rupprechtiiArtificial forests in mid-low elevation district will be the pure artificial forests of Larixprincipis—rupprechtii�'mixed broadleaf-conifer forests of Larix principis—rupprechtii+Quercus aliena var. acuteserrata+Acer davidii+Juglans cathayensis+Toxicodendromverniciflua�'mixed broadleaf-conifer climax communities of Quercus aliena var.acuteserrata+Juglans cathayensis+Toxicodendrom verniciflua. Its management strategy toeconomic benefit as the premise,using close-to-nature forest management techniques to buildthe different age, stratified mixed forests of Larix principis—rupprechtii is dominant speciesand Quercus aliena var. acuteserrata+Juglans cathayensis+Toxicodendrom verniciflua areassociated species. The tendency of Larix principis—rupprechtii Artificial forests in mid-highelevation district will be the pure artificial forests of Larix principis—rupprechtii�'mixedbroadleaf-conifer forests of Larix principis—rupprechtii+Pinus armandi+Betulaalbo-sienensis�'mixed broadleaf-conifer forests of Pinus armandi+Betula albo-sienensis+Pinus asperata(Picea wilsoni) or Abies fargesii�'climax communities of Pinusasperata(Picea wilsoni) or Abies fargesii, Its management strategy is Replace tree species, Through the intervention to speed up its succession process to climax communities of Pinusasperata(Picea wilsoni) or Abies fargesii follow the natural succession trend.(4) By combined with the growth rule of tree height and DBH for Larixprincipis—rupprechtii Artificial forests, the growth stage of Larix principis—rupprechtiiArtificial forests was divided into five section based on the theory and techniques ofclose-to-nature forest management，constructive stage (DBH≤4cm，H≤5cm)、competitivegrowth stage (4＜DBH≤12cm,5＜H≤13m)、quality selection stage (12＜DBH≤21cm,13＜H≤21m)、close-to-nature forest stage (21＜DBH≤40cm,21＜H≤26m) and constantrenewal forest stage (DBH＞40cm， H＞26cm). Homologous close-to-nature forestmanagement measures of both Larix principis—rupprechtii artificial pure forests and Larixprincipis—rupprechtii mixed coniferal leaf forests was put forward based on the standcharacteristics of different stages，and formed close-to-nature management techniquesultimately for Larix principis-rupprechtii artificial forests in intermediate section of QinlingMountains.