Study On Site Quality Evaluation Of The Adiessibirica Ledeb Secondary Forest

In this study,Adiessibirica Ledeb secondary forest of Wangqing Forestry Bureau,Jilin Province are set as research object which is site type classified using the data of 172 in-place inventory,178 reset sample plot and 96 anatomical tree.7 most representative main site types are picked to fit the DBH,height growth model of dominant Adiessibirica Ledeb.Guiding curve single site index table and site type polymorphic site index table of Adiessibirica Ledeb secondary forest are worked out respectively according to the average height of dominant trees at standard age and the accuracy comparison of the two site index table is carried out.Site quality evaluation of the Adiessibirica Ledeb secondary forest in the research area is conducted according to the growth status of the Adiessibirica Ledeb secondary forest of different site types.Specific research conditions are as follows:(1)Site factors(climate,altitude,soil type,soil thickness,topography and geomorphology,etc.)are analyzed and 5 site factors including altitude,slope,slope direction,slope position and soil layer thickness are selected.It is concluded that the dominant factors of the site classification is the altitude,the soil layer thickness,the slope and the slope direction using the Quantitative Theory 1 and that the importance ranking of the site factors influencing the growth of the Adiessibirica Ledeb secondary forest is:the altitude>the soil layer thickness>the slope>the slope direction.The research area is divided into 36 site types thus establishing the site type table of Adiessibirica Ledeb secondary forest of Wangqing Forestry Bureau.(2)The DBH and the height growth of the dominant Adiessibirica Ledeb of 7 typical site types are analyzed to determine the basal age of Adiessibirica Ledeb to be 60 years as well as the DBH and the height theoretical optimal growth model of the dominant Adiessibirica Ledeb of different site types.In the site of high altitude,thick soil layer,small and shady slope,the DBH and height of the Adiessibirica Ledeb grows at a higher speed at their early and middle age.The curve intersection between average increment current annual increment of DBH and height is about 60 years.While in the site of low altitude,thin soil layer,big and sunny slope,the DBH and height of the Adiessibirica Ledeb grows at a lower speed at their early and middle age.And the curve intersection between average increment current annual increment of DBH and height is over 60 years.(3)Fit the height growth data of the dominant Adiessibirica Ledeb to get:Optimal guiding curve equation:H=29.7175 e-4.3076e-0.0297,Polymorphic site index model equation:The accuracy tests of these two site index models are carried out respectively using the standard deviation method,index range method and impact testing method and it turns out that the site type polymorphic site index model is better than the guiding curve single site index model.(4)According to the actual situation of the site types of sample sites,the stand unit area accumulation of the site types which takes Adiessibirica Ledeb as dominants trees is estimated and the site quality comprehensive evaluation system of the Adiessibirica Ledeb secondary forest of Wangqing district is established.Based on the site classification results,the height of dominant Adiessibirica Ledeb at the basal age,and the stand unit area accumulation,the site quality is classified into three grades:good(?),medium(?)and poor(?).The site with good quality(?)has relatively high altitude,thick soil layer,gentle slope most of which are shade slopes,good forest form,complete structure and high comprehensive benefit.The medium(II)quality site is the key point of tending and management to keep the stability of the stand and to promote progressive succession.The poor(?)quality site has lower altitude,thinner soil layer,bigger slope most of which are sunny slopes,bad and complicated forest form for which differential measures can be taken based on the site evaluation results during the course of forest management.