基于混合效应的湖北杉木冠长率模型

为研究冠长率与林分因子之间的生长关系,分析不同因素对冠长率的影响,对湖北全省杉木栽植区域进行标准地调查,利用181块调查样地的715株优势木和平均木数据建立冠长率模型.从树木及立地因子中选出与冠长率相关性显著的树高、胸径、高径比、每公顷株数和大于对象木断面积5个因子作为变量,利用Logistics方程构建冠长率基础模型...

A Crown Ratio Model for Cunninghamia lanceolata Plantations Based on Mixed Effect in Hubei

The paper aims to study the relationship between crown ratio and stand factors, and analyze the effects of different factors on crown ratio. 715 dominant trees and average trees in 181 sample plots were established in Chinese fir planting areas in Hubei Province. Tree height, diameter at breast height, height to diameter ratio, stand density and basal area per hectare for trees larger than the subject tree closely associated with crown ratio were selected among tree and site factors. The basic model of crown ratio was constructed by adding correlation factors as variables in the form of logistic equation, and the single-level mixed effect model of sample plot was further established. By comparing the AIC, BIC and likelihood ratio test, the mixed model with random parameters a and f has the best fitting effect compared with the model without random parameters. The results of independent sample test show that the root mean square errors and average error of the mixed model are reduced, respectively -0.0095 and 0.1175, and the residual range is smaller. Compared with the basic model, R² of the mixed model increased from 0.3231 to 0.5417, but RMSE and Bias decreased. Based on the goodness of fit and test index of the model, the mixed model can significantly improve the fitting accuracy of the model, and can be used to predict the crown length.