| With the increasing emphasis on ecological environment in China,Pinus massoniana,as one of the native and timber tree species in Fujian Province,has realistic and long-term significance in improving the quality of natural forest and rational management of Pinus massoniana.The research object is Pinus massoniana natural forest.The basic data are 138 temporary sample plots,319 fixed sample plots,564 sample trees and 960 sample timber data collected in the natural forest distribution area of Pinus massoniana in Fujian Province.The volume table,diameter-grade timber yield model,total stand growth and harvest model and individual tree model of Pinus massoniana natural forest were established.The application of selective cutting income method in evaluation of Pinus massoniana natural forest was discussed by combining the total stand growth and harvest model with timber yield model.(1)By collecting the sample data and timber data of Pinus massoniana,the volume table of natural Pinus massoniana forest and the output rate model of diameter grade timber species were established.The fitting results are as follows: the prediction accuracy P > 97%,T-test p > 0.05,which shows that the established volume table and output rate table have high accuracy and applicability and can be used in forestry production.(2)Firstly,the five alternative equations Korf,Richards,Gompertz,Logistics and Mitscherlich are screened in this paper.By comparing the correlation coefficient(R2)and root mean square error(RMSE),the results show that Richards equation is the most suitable one for constructing the status index model of Pinus massoniana natural forest.When constructing the model,the three parameters of the status index SCI and Richards equation show power function,exponential function and linear function relations respectively,and finally a six-parameter polymorphic status index model is constructed.The fitting results are R2=0.975,P=99.5%,p > 0.05,which shows that the six-parameter polymorphic status index model has good fitting effect and high precision.(3)The variable density harvesting table of Pinus massoniana natural forest was compiled by comprehensive application of the polymorphic site index model,the dynamic prediction model of stand density index,the model of stand cross-section area and the prediction model of stand volume.(4)The DBH of dominant trees was used as a competitive index for individual trees.Potential growth function,correction function and tree height curve were established based on the dominant tree data of analytic trees.The correlation coefficients are all above 0.9,and the prediction accuracy is more than 99%,the significant p value is more than 0.05.Through the potential growth function and potential growth correction function,the DBH of individual tree at different ages and sites can be calculated,and the height of individual tree can be obtained from the height curve.Finally,the volume of individual tree can be calculated according to the binary volume table.(5)Combining the growth and harvesting model of the whole stand of Pinus massoniana natural forest with the timber yield model of diameter-grade timber species,the natural forest of Pinus massoniana was evaluated by the selective cutting income method.By establishing Z_t model of stand restoration stock,the selective cutting period was determined,the selective cutting income method was optimized,and the influence of different selective cutting intensity and interest rate on forest evaluation value was analyzed.The results show that when the interest rate remains unchanged,the value of forest evaluation increases with the increase of selective cutting intensity,and decreases with the increase of interest rate when the selective cutting intensity and corresponding selective cutting period remain unchanged. |
