Study On Site Quality Evaluation Of Larix Principis-rupprechtii Mayr Plantation In Saihanba

Site quality is an important indicator to determine the degree of adaptation and use value of forest growing tree species to site conditions.Site quality evaluation is of great significance in forestry production practices such as forestation planning,tending and management.The research took the Larix principis-rupprechtii Mayr plantation in Saihanba as the main research object,using the second-category inventory data and the temporary survey sample plot data of 90 Larix principis-rupprechtii Mayr plantations under different site conditions and analytical wood data,In order to provide some theoretical guidance and suggestions for afforestation planning,production and management of Larix principis-rupprechtii Mayr plantation in Saihanba area,the research on site quality evaluation of Larix principis-rupprechtii Mayr plantation in Saihanba area was carried out by using site index method,multiple site index method and DBH site class method.The main findings of this study are as follows:（1）Use the data of 90 temporary sample plots,three tabulation methods were adopted:the high relative advantage method,the standard deviation adjustment method and the coefficient of variation adjustment method to compile the position index table of the Saihanba Larix principis-rupprechtii Mayr plantation.Point test,chi-square test,residual standard deviation method logarithmic table test.Among them,the order of the accuracy of the drop point test is:the coefficient of variation adjustment method>the standard deviation adjustment method>the high relative advantage method;the accuracy of the chi-square test is in order:the standard deviation adjustment method>the coefficient of variation adjustment method>the high relative advantage method;The order of accuracy of the residual standard deviation method is:standard deviation adjustment method>variation coefficient adjustment method>relative advantage high method.It can be seen that the accuracy of the position index table compiled by the high relative advantage method is relatively lower than that of the position index table compiled by the standard deviation adjustment method and the coefficient of variation adjustment method.Combining the three inspection methods,it can be seen that the standard deviation adjustment method is most suitable for the compilation of the Saihanba Larch plantation status index table.The site quality grades of Larix principis-rupprechtii Mayr plantation in Saihanba is mostly at the medium level according to the standard deviation adjustment method.According to the survey data of temporary sample plots,using the curve estimation function of SPSS26.0 statistical software,the regression equation of the average height of the dominant trees and the average height of the forest was fitted,and the average height of the dominant trees was changed to the average height of the forest.The regression equation of the fitted average height of forest stand-the average height of dominant trees is:H=1.357+0.585H_优+0.010H_优²+0.0002H_优³,the coefficient of determination of the regression equation is 0.947.According to the compiled status index table and the relationship between the average height of dominant trees and the average stand height,the average stand height status compiled by the three tabulation methods of relative advantage height method,standard deviation adjustment method and variation coefficient adjustment method is formed Index table to facilitate site quality evaluation directly based on the second-category data survey data.（2）Using the method of quantification theoryⅠ,determine the contribution rate of each site factor to the high dominance of Larix principis-rupprechtii Mayr based on the relationship of the partial correlation coefficient obtained from the analysis.The research results show that the contribution rate（importance）of the six site factors to the site quality is:forest age>elevation>soil texture>slope>slope direction>soil layer thickness.Using the quantitative theory I method combined with the least squares method to obtain 6 prediction equations with different numbers of factors,according to the prediction equations,a quantitative site quality score table and a quantitative site quality evaluation table were compiled.When using the score sheet or evaluation sheet,the 1～6 factors of the compiled sheet can be used to evaluate the site quality.The more factors used,the more accurate the site quality evaluation of Larix principis-rupprechtii Mayr plantation.According to the score value of each site factor in the prediction equation,the site quality of Larix principis-rupprechtii Mayr plantation in Saihanba area are divided into four levels:excellent,good,medium,and poor.According to the score statistics of the second-category survey data,it can be seen that the site quality grades of Larix principis-rupprechtii Mayr plantation in Saihanba are mostly at the medium or above level.（3）The DBH site class method was used to compile the DBH site class table of Larix principis-rupprechtii Mayr plantation.According to the test,the precision of the drop point test is97.59%,and the value of the model T test is-3.17,which is less than the value of T_0.05（455）in the lookup table.The average relative error R is-0.25%,the relative total error Q is 11.89%,and the precision is 98.64%,indicating that the model has high precision and good applicability.The site quality of Larix principis-rupprechtii Mayr plantation in Saihanba is 87.23%above the medium level.