Crown diameter model of Hunan Quercus natural forest based on competition and site effect
[Objective]This study was carried out to analyze the effects of site factors and competition factors on the crown width growth,construct a crown width model of Hunan Quercus natural forests with the mixed effects of site types and competition factor.It provides a theoretical basis for scientific management decision of Quercus natural forests.[Method]With 1 429 Quercus trees in 51 natural forest plots of Hunan province as the research object,the factors that had significant influence on crown extent were screened,and the factors were classified and combined according to the standard to form site types and competition types.The optimal basic model was selected from 10 basic models.k-means clustering was used to cluster the initial competition types into competition type groups.The competition type group and the site type group were added into the optimal basic model as random effects,and the mixed effects model including the site type and the competition type group was constructed.[Result]The factors that significantly affected crown width included altitude,slope,slope position,slope direction,soil type,relative fault area(RS),simple competition index(CLH),and greater than the sum of the object wood fault area(BAL).The significance order of site factors was altitude＞slope＞slope direction＞slope position＞soil type,and Rs was positively correlated with crown width among competition factors.CLH and BAL were negatively correlated with crown width.The optimal basic model was allometric growth model(with intercept),R2 was 0.534 8.The three competition factors were classified and combined according to the standard to form the competition type,and the mixed effect model with competition type was added to the basic model,and the R2 increased to 0.583 5.k-means clustering was applied to cluster the initial competition types into 17 competition type groups,which were added to the basic model as random effects,and R2 increased to 0.749 2.The combined site types were added to the model as random effects,and the crown width model based on the mixed effects of competition and site was constructed.The R2 of the model increased to 0.841 6,which was 57.36%higher than that of the basic model.[Conclusion]The natural forest canopy model of Hunan Quercus with competition factor and site factor has better fitting effect and prediction accuracy.Therefore,the canopy width model constructed in this study can well predict the canopy width of natural Quercus forest in Hunan,and provide support for the study of the growth and management of natural Quercus forest and the update of forest resource survey database.
NETL
NSTL
万方数据
