Study On High Prediction Mixed Effect Model Of Quercus Variabilis

Tree height model research is an important frontier topic in the field of forestry resources.Establishing a highly applicable tree height-diameter model is of great significance for carrying out forest resource surveys,forest structure adjustments,and forest growth studies.Tree height and DBH are two important tree-building factors in the survey of forest resources,it’s the data foundation for identifying the total amount,type,distribution,and growth of resources.In view of the relatively difficult problem of tree height measurement,this article takes 94 cork oaks from Xixi Town,Yongkang City,Jinhua City as the research object,and compares the fitting effects of10 tree height curve models commonly used in forestry,improved the traditional tree height curve model-Gompertz model,proposed and constructed a Gompertz mixed effect prediction model with site factors.Experiments show that:（1）When fitting the Gompertz mixed effect model,the model fits best when the random parameters b₁ and b₃ are introduced;when fitting the Gompertz mixed effect model containing site factors,the model fits best when the random parameters b₁ and b₄ are introduced.（2）The Gompertz mixed effect improvement model constructed in this paper has a coefficient of determination of 0.779,the Gompertz mixed effect model has a coefficient of determination of 0.553,and the Gompertz model has a coefficient of determination of 0.542.That is to say,building the model only by the mixed effect method is not obvious for improving the accuracy of the prediction model,the construction of the mixed effect model based on the improved model greatly improves the prediction accuracy of the model.（3）Experiments show that the Gompertz mixed effect improvement model constructed in this paper greatly improves the prediction accuracy of the height of Quercus variabilis,and provides a new method for studying the relationship between tree height and diameter at breast height of tree species.The tree height model itself does not have a general form.This paper innovatively constructs a site-driven tree height growth model for all cork oak trees in Xixi Town,Yongkang City,Jinhua City.It provides a theoretical basis for the high prediction of Quercus variabilis in this region,and has important reference value for building tree height models in other regions.