Study On Storey Identification Method Of Quercus Secondary Forests In Hunan Province

Storey identification is helpful to study the characteristics and variation of natural secondary forest stands.The nature of storey differentiation is formed by forest tree individual differentiation,which caused by forest competition,and the existing forest storey division method does not fully consider the competition among forest trees.-The impact of storey identification.As one of the most abundant natural secondary forest resource distribution area in China,Hunan is an important part of how to accurately classify the secondary forest storey of Ouercus,which is particularly important for its stand characteristics and its variation and forest management.In view of this,51 typical plots of natural secondary forests of Quercus in Hunan Province were selected as research objects.From the perspective of forest competition,a method for forestry division of natural secondary forests in Hunan was proposed,which was provided reference and theoretical basis for the management,management,protection and utilization of Quercus secondary forests.(1)Propose the forest competition division method.After completed the construction of the free tree crown model,the competitive pressure index(CSI)and the comprehensive competitive pressure index(C-CSI)of all forest trees were calculated,and the calculated values of the two competitive pressures of the forest were used as clustering factors.K-means cluster analysis,the whole forest stand was divided into two forest storeys or three forest storeys,based on which the forest competition division method was proposed.(2)Inspection of new methods of forest storey division.The national forest division standard was selected to test the forest division number and tree height variation coefficient of the forest competition division method to test the pros and cons of the two competition indicators,the diameter distribution law and the height-diameter relationship of the tree to test the forest storey of the forest competition division method.Whether the division conforms to the rule of natural differentiation.1)The results of the national forest division standard test showed that it was in line with the national forest division standard when it was divided into two storeys,and did not conform to the national forest division standard when it was divided into three forest storeys;2)The test results of tree height coefficient of variation showed that the average tree height coefficient of variation was significantly lower than that of un-storeyed forest,and the comprehensive competitive pressure index was superior to the competitive pressure index.Among them,the average tree height coefficient of variation of the whole forest was 28.04%,the average tree height coefficient of variation of the upper storey was 13.23%,which was reduced by 52.82%;the average tree height coefficient of variation of the lower storey was 19.00%,which was decreased by 32.24%.Compared with the competitive pressure index,the comprehensive competitive pressure index reduced the tree height coefficient of variation of the upper storey by 10.73%,and the tree height coefficient of variation of the lower storey remained basically unchanged;3)The test results of diameter distribution law indicate that the forest competition division method divided the forests with similar growth status in the forest into the same forest storey,which accurately reflected the natural differentiation of forest storeys in the secondary forests.Among them,the fitting results of the upper diameter distribution were consistent with the Weibull distribution,and the parameter c was between 1-3.6,showing a right-handed mountain curve.The lower-storey fitting results obey the Gamma distribution,and the parameters p are all greater than 2.The diameter distribution curve was convex first,then convex upward,and finally convex downward,while the Weibull distribution function,Gamma distribution function and normal distribution function did not effectively fit the diameter distribution of the entire axillary secondary forest.4)The test results of tree height-diameter relationship showed that the tree height and the diameter-diameter relationship of each sub-storey were more regular than the whole forest stand,which is more regular than the non-stratified forest stand.There was a significant decrease in mean absolute error(AMR)and root mean square error(RMSE)between the upper and lower storeys.Among them,the Curtis-style fitting effect was better than the Schumacher formula,and the average absolute error(AMR)is lower,the root mean square error(RMSE)and the determination coefficient(R2)were higher.(3)Comparison of new methods of forest storey division and existing methods.The research results showed that the forest competition division method was superior to the existing forest storey division method for the current stage of the identification of natural secondary forests in Hunan..Among them,the TSTRAT method was easy to draw more forest storeys,especially the number of forest storeys in the lower storey of the forest was obviously more;the interstorey spacing between the sub-storeys of the LMS method is obviously smaller,and the single-wood storeying is likely to occur in the lower forest storey.Phenomenon;the number of forest divisions of the International Union of Forests division method was fixed at 3 storeys,lacking certain flexibility and applicability;the whole tree high clustering method divides the results from the pure data to the forest storey,and it was easy to use the high breakpoint of the tree as the clustering point in clustering.The result of the division lacks certain biological interpretation.Finally,the classification results of the five forest division methods were tested by the national forest classification standard.The test results showed that the forest competition division method satisfy the test standard.