Site Index Model for Regional Cunninghamia lanceolata Plantations Based on Nonlinear Mixed Effect
A regional nonlinear mixed site index model of Cunninghamia lanceolata plantations with site factors was established to provide a reference for predicting the height of Cunninghamia lanceolata in the region.This study is based on data from the analysis of 307 disc groups from 45 dominant trees across 4 provinces,selecting five common tree height-age growth equations.Using quantitative theory I,nonlinear mixed model and other methods,the mixed model of nonlinear site index with initial site type was constructed by using random effects.Finally,the mixed model of nonlinear site index with site type group was further developed by K-means clustering.The results showed that altitude,soil type,aspect,and slope position were the site factors that significantly affected the tree height.The Gompertz model was selected as the basic model,showing the best fitting effect,with an R2 of 0.653.Compared with the basic model,the accuracy of the nonlinear site index model with the initial site type is improved by 28.02％.Compared with the basic model,the R2 of the nonlinear site index mixed model with site type group was increased by 37.21％.After cross testing of the model,the accuracy of the model was high based on the initial site type and clustering,which confirmed the practicability of the model.The establishment of a nonlinear site index mixed model provides a feasibility for the site quality evaluation and compilation of site index tables for Cunninghamia lanceolata plantations at the regional scale.
Cunninghamia lanceolatap lantationssite indexnonlinear mixed modelquality of site evaluation
NETL
NSTL
万方数据
