The Study Of Forest Structure Optimization Technology Based On Stability And Near-natural

English Title: The study of Forest structure optimization technology based on Stability and near-naturalMost of the large-scale existing plantations in Haidong Qinghai Province came from the “planting trees in northwest area” that began in the 1980 s.During this period,the plantations was designed by the Timber Forest's standard.So the existing forest structure is horizontal and vertical.At the beginning of this century,the forestry management in China began to classify,large-scale plantation forests in the northwest were classified as ecological public welfare forests.These forests have been closed and managed for nearly 20 years.Although these plantation forests play a better role in soil and water conservation and landscape greening,these plantation has low ecological benefit.In this study,four different existing underground's forests in Anmentan,Targou and Yangjiazhai,Datong County,Qinghai Province were researched.Based on the survey of sample plots,use the analytic hierarchy process to build a comprehensive evaluation index system for stability.By the system to choose the best stability and the worst stability of each stand.Combine the analysis from the stand structure with the reault of selection put forward the technology of Stand transformation.The main conclusions of this study are as follows:(1)Constructed stand evaluation structure including 12 evaluation indicators in stand structure,stand expanded structure,stand resistance stability,stand functional stability.According to weight analysis,the main factors affecting the stability of the forest stand in this area are forest density(0.2134)and soil moisture(0.1990).And using forest density and soil moisture theory in Stand transformation.(2)Assess the forest stability of the three areas by GIS.According to the stability map these items can be concluded.The stability of forest that in shady slope stands is higher than that in sun slope stands.The stability of the site has the rules as follow: High shallow hilly gentle slope> Low shallow hilly gentle slope> Low shallow hilly gentle slope> Low shallow hilly steep slope.The types of forest stands with the best stability under different standing grounds are: high-level shallow hilly gentle slope-Qinghai spruce / birch mixed forest;low-level shallow hilly gentle slope-Qinghai Spruce forest;low shallow mountain-yang gentle slope-Qilianyuan Berlin.Afforestation and stand structure transformation under the same site conditions can refer to these stand types.(3)According to the result of the study,proposing structural measures suit for the stability improvement of the study area.By these measure,the neighbourhood pattern has been reduced from 0.527 to 0.517 in the qinghai spruce forest,the mingling degree has been increased from 0.019 to 0.424 in the qinghai spruce forest,the neighbourhood pattern has been reduced from 0.528 to 0.499 in the Qinghai spruce and larch mixed forest,the mingling degree has been increased from 0.462 to 0.587.After the transformation,the distribution of forest diameter step distribution changed from normal distribution to inverted "J" type distribution,while reducing competition in the forest and accelerating the formation process of heterogeneous double-layer artificial forest structure.