四川省黄葛树古树单木冠幅预测模型OA

A mixed model theory was applied to construct a crown width model for the ancient trees Ficus virens trees,with a view to providing theoretical basis and practical guidance for the prediction of the ancient Ficus virens trees.The best base model was determined from the results of fitting eight crown width models using 7 652 ancient Ficus virens trees in Sichuan Province as the study object.Single-tree and soil factors were introduced into the optimal base model to construct a generalised model and analyse the relative importance of the factors and their effects on crown width growth.Based on the constructed gener-alised model,the mixed-effects model theory was used to construct the crown width model,and the con-structed model was tested using the leave-one-out cross-validation method to compare the prediction accu-racy of each model.The results indicate that the best base model for the ancient Ficus virens is the logistic model;tree age(AGE),soil organic carbon content(SOC),and soil pH were introduced separately to bet-ter explain the growth differences of ancient Ficus virens trees in Sichuan Province;The introduction of re-gional level random effects can significantly improve the model prediction accuracy,and the mean absolute error(MAE)of its test using leave-one-out cross-validation is 2.825 3 m;Empirical best linear unbiased prediction(EBLUP)was used for model calibration,and the predictive performance of the model improved with the increase of measured sample size.