塞罕坝华北落叶松—白桦针阔混交林胸径年生长量预测

Prediction of the Diameter Annual Radial Growth of Larix principis-rupprechtii and Betula platyphylla Mixed Forest in Saihanba

以河北省塞罕坝国家森林公园华北落叶松—白桦针阔混交林为研究对象,基于87块标准地(20m×30m)的348株解析木数据,建立包含样地间及样地内随机效应的胸径—年龄非线性混合效应模型,并在混合效应模型中加入哑变量来解决样地内不同树种带来的差异。结果表明,华北落叶松单木胸径非线性混合效应模型确定系数(R2)、-2log Likelihood值、信息准则(Alcaikes information criterion,AIC)值、贝叶斯信息(Bayesion informatian criterion,BIC)值分别为0.85、898.1、880.2、855.4;白桦单木胸径非线性混合效应模型确定系数(R2)、-2log Likelihood值、AIC值、BIC值分别为:0.81、500.9、482.6、465.7。白桦和华北落叶松最大年生长量分别为0.44cm和0.41cm,年龄和竞争指数与胸径生长量呈负相关关系,胸径和林分优势高与胸径生长量呈正相关关系,其中林分优势高与华北落叶松—白桦混交林径向生长量相关性较低。包含哑变量的混合效应生长模型解决了混交林中样地间及样地内树种对胸径生长的影响,提高了模型精度及适用性,为该地区针阔混交林经营水平及经营效果的提高提供依据。

A total of 87 temporary plots （20 m×30 m） were established in Larix principis-rupprechtii and Betula platyphylla mixed forest of Saihanba National Forest Park,Hebei Province,China.We investigated a total of 348 analytic trees.Nonlinear mixed-effects model of diameter was established including random-effects of plots.We also added dummy variables to the mixed-effects models in order to solve intra-plot variability resulting from species difference.The results indicated that for L.principis-rupprechtii and B.platyphylla,nonlinear mixed-effect models were established respectively.Both models had the best fits with the fit statistics values （R2=0.85;-2 log Likelihood=898.1;AIC=880.2;BIC=855.4） for L.principis-rupprechtii and values （R2=0.81;-2 log Likelihood=500.9;AIC=482.6;BIC=465.7） for B.platyphylla.The maximum annual growth of B.platyphylla and L.principis-rupprechtii were 0.44 cm and 0.41 cm,respectively.The age and competition index had a negative correlation with diameter annual radial growth.The DBH and dominant height of stand had a positive correlation with diameter annual radial growth.Dominant height of stand had a lower correlation with annual radial growth in L.principis-rupprechtii and B.platyphylla mixed forest.The mixed-effect models with dummy variables solved the negative effects of species differences between plots and within plot on diameter relationships in mixed forests.The results would povide better model fitting,more applicability and more precise estimations than the basic generalized model.