内蒙古大兴安岭林区白桦天然林单木胸径生长模型构建

Construction of individual tree DBH growth models for natural Betula platyphylla forests in Daxing’an Mountains,Inner Mongolia of northern China

【目的】为准确预测内蒙古大兴安岭林区的白桦天然林单木生长并制定适应性经营管理措施,构建包含气候因子和林木大小多样性因子的白桦单木胸径生长混合效应模型。【方法】数据来源于内蒙古大兴安岭林区第8和9次森林资源清查数据,共筛选出符合要求的固定样地97块,白桦样木4785株。基于筛选的数据,运用逐步回归法,构建传统单木胸径生长模型,并在此模型的基础上,引入样地随机效应,构建白桦单木胸径生长混合效应模型。利用十折交叉验证法分别对已构建的基础模型和混合效应模型进行检验。【结果】期初胸径的对数、大于对象木的断面积和、样地内胸径标准差、生长积温和年平均降雨量对白桦单木胸径生长量存在显著影响。与基础模型相比,混合效应模型的调整决定系数提高了0.1206,均方根误差降低了0.0971 cm2,模型的预测精度显著提高。十折交叉验证的结果表明混合效应模型同样表现出较好的拟合结果。【结论】包含气候因子和林木大小多样性因子的白桦单木胸径生长混合效应模型能精准预测白桦单木胸径的生长动态,可以为内蒙古大兴安岭林区的白桦天然林的科学经营提供支持。

[Objective]In order to accurately predict growth and formulate adaptive management measures for natural Betula platyphylla forests in Daxing’an Mountains,Inner Mongolia of northern China,a mixedeffects individual-tree DBH growth model of Betula platyphylla,including climatic factors and tree size diversity factors,was developed.[Method]The data were derived from the 8th and 9th national forest inventory in Daxing’an Mountains of Inner Mongolia,including a total of 97 fixed sample plots and 4785 sample tree observations of Betula platyphylla.Based on the selected data,the traditional growth model of individual-tree DBH was constructed by stepwise regression method.Then,sample plot effects were added to construct individual-tree mixed-effects model of Betula platyphylla.Finally,we validated the basic model and the mixed-effects model by 10-fold cross-validation method.[Result]The logarithm of initial DBH,basal area of trees larger than the subject tree,standard deviation of DBHs,growth accumulation temperature and mean annual precipitation had significant effects on individual-tree DBH growth of Betula platyphylla.Compared with basic model,of final mixed-effects model increased by 0.1206,and the root mean square error decreased by 0.0971 cm2,respectively.The prediction accuracy of the mixed-effects model improved significantly.The results of 10-fold cross-validation indicated that the mixed-effects model also showed a better fitting result.[Conclusion]The individual-tree DBH growth mixed-effects model of Betula platyphylla including climatic factors and tree size diversity factors can accurately predict the DBH growth of individual trees,which can provide support for scientific management of natural Betula platyphylla forests in Daxing’an Mountains,Inner Mongolia of northern China.