帽儿山阔叶混交林天然更新幼苗幼树地径-树高模型

Ground diameter-height models of naturally regenerated seedlings and saplings under broad-leaved mixed forest in Maoershan Mountains

基于黑龙江省东北林业大学帽儿山实验林场48块天然阔叶林幼苗幼树调查数据,在8个备选模型中为主要更新树种选择最佳地径(D0)-树高(H)模型作为基本模型,通过再参数化在基础模型中引入林分因子,并建立样地水平混合效应模型,最后分别对基础模型和混合效应模型进行独立样本检验.结果表明:各树种幼苗幼树的地径-树高关系存在明显的正相关,幂函数或包含幂函数的模型能较好地拟合幼苗幼树地径和树高的关系;基础模型中引入林分因子[林分优势高(HT)、林分平均胸径(Dg)、林分胸高断面积(BA)]能提高模型的拟合效果,各树种剩余均方根误差(RMSE)下降1.3%~7.4%(平均3.8%),但调整后的决定系数(Ra2)仅仅提高0.1%~1.1%(平均0.6%),赤池信息准则(AIC)下降3.2%~35.2%(平均下降11.4%).对春榆、椴树、水曲柳等10个树种建立混合效应模型,混合效应模型的Ra2比基础模型有所提高,增幅为0.5%~3.5%(平均增加2.2%);RMSE和AIC比基础模型的小,RMSE下降的幅度很大,为3.9%~20.3%,平均下降13.9%,AIC减少4.0%~44.4%(平均减少22.3%).模型检验结果显示,相对于基础模型,混合效应模型的平均绝对误差(MAE)减小0.0001~0.46 m,平均减小0.08 m;平均预测误差百分比(MPSE)降幅较大,为0.1%~6.2%,平均降幅2.0%.说明混合效应模型既能提高模型的拟合效果,又能提高模型的预测能力.本研究构建的阔叶混交林主要更新树种幼苗幼树地径-树高模型为天然阔叶林结构分析和林分生长预测提供了参考.

Based on the investigation data of seedlings and saplings from 48 plots in natural broad-leaved forest of Maoershan Experimental Forest Farm of Northeast Forestry University in Heilongjiang Province,the optimum model of ground diameter(D0)-height(H)was selected from eight alternative models as the basic model for the main regeneration tree species,and then the stand factors were parameterized,and the mixed effect model of sampling plot level was developed.The basic model and the mixed effect model were tested by independent samples.The results showed that there was a significant positive correlation between ground diameter and tree height of seedlings and saplings and that power function or model containing power function could better fit the relationship.The introduction of stand factors[dominant height of forest(HT),average diameter at breast height(Dg),basal area of forest(BA)]could improve the fitting effect of the model,with the residual root mean square error(RMSE)of each tree species decreasing by 1.3%-7.4%(average 3.8%),adjusted coefficient of determination(Ra2)only increasing by 0.1%-1.1%(average 0.6%)and Akaike info criterion(AIC)decreasing by 3.2%-35.2%(average 11.4%).Mixed effect models were developed for 10 tree species,such as Ulmus propinqua,Tilia and Fraxinus mandshurica.The Ra2 of mixed effect models was larger than that of the basic model,with an enhancement of 0.5%-3.5%(average 2.2%).RMSE and AIC decreased by 3.9%-20.3%(ave-rage 13.9%)and 4.0%-44.4%(average 22.3%)than that of the basic model.Model test results showed that,compared with the basic model,the average absolute error(MAE)of mixed effect model was reduced by 0.0001-0.46 m,with an average reduction of 0.08 m,and the average prediction error percentage(MPSE)decreased by 0.1%-6.2%,with an average reduction of 2.0%.The mixed effect model could improve the fitting effect and prediction ability of the model.The ground diameter-height model of seedlings and samplings of main regeneration species in broad-leaved mixed forest was developed in this study,which provides a reference for structure analysis and stand growth prediction of natural broad-leaved forest.