Research on evaluation indicator and method of stand quality

In order to scientifically judge the quality status and management effect of stand, the multi-indicator comprehensive evaluation method of stand quality was studied. Based on the principles of comprehensiveness, scientificity and operability, this research selected nine evaluation contents from two aspects of stand structure and stand vitality, including vertical structure, horizontal structure, age structure, tree species composition, stand density, stand growth, stand regeneration, large-diameter tree and tree health. Firstly, the specific evaluation indicators were given to each content to form the stand quality evaluation system, and then a bran-new stand quality comprehensive evaluation index (FQ) was constructed based on the unit circle method. By comparing the stand quality of typical forest types in 27 plots of 7 regions in China, the validity, scientificity and accuracy of the index were demonstrated. The results were as follows: (1) The stand quality of natural mixed forests was significantly better than that of natural pure forests, and the stand quality of artificial mixed forests was generally better than that of artificial pure forests; (2) The stand quality grades of natural mixed forests were all ≥ grade II, among which the stand quality grades of some natural mixed forests were grade I; (3) The stand quality grades of artificial mixed forests mainly were grade III, the stand quality of natural mixed forests was significantly better than that of artificial mixed forests; (4) In pure forests, only part of the natural pure forest stand quality grades were grade III, the quality grades of other pure forests were grade IV, especially the quality grades of artificial pure forests were grade IV. In comparison, the stand quality of artificial pure forests was the worst. The evaluation results obtained by the index constructed in this research were intuitive and reliable, which were in line with the objective reality and universal law of the actual stands. It could be seen that the multi-indicator comprehensive evaluation method of stand quality proposed in this research could scientifically and fairly evaluate the stand quality of different forest types in different regions. At the same time, it also provided an important theoretical basis and analysis tool for the problem diagnosis of stand quality, the accurate improvement of stand quality and the decision-making of forest management.