湖南栎类次生林林分断面积生长模型

Basal area growth model of Oak secondary forest in Hunan province

【目的】构建湖南栎类次生林林分断面积生长模型,为其经营措施和生长收获预估提供理论依据。【方法】以湖南省6期国家连续清查数据(1989—2014年)中以栎类为优势树种或主要树种的样地为研究对象。选用7种常用的生长理论方程,以林分断面积为因变量,年龄为自变量构建基础模型。通过评价指标选出最优基础模型,构建含有地位指数、林分年龄和林分株数的混合效应模型(林分株数为随机变量)和参数化模型(林分株数为连续变量),比较基础模型、混合效应模型和参数化模型拟合效果的差异。【结果】3种模型的预估精度由高到低为:参数化模型(98.36%)、混合效应模型(97.71%)、基础模型(92.84%),最终将参数化模型作为湖南栎类次生林林分断面积生长模型。在林分年龄、林分株数及地位指数中任意两个影响因素相同时,林分断面积总生长量(林分断面积5 a的生长量)随着另外一个因素的增加而增加,且密度越大,相邻两个密度的断面积总生长量差距越小;5 a的生长量到最大值后密度越大生长量减少速度越快;其他因素相同时,林分株数越多,生长量最大值出现的越早(20 a),地位指数越大,断面积5 a的生长量越大。【结论】以林分株数为连续变量的参数化模型生成的湖南栎类次生林林分断面积总生长量曲线、5 a的生长量曲线符合林分生长规律,且预测精度较高,可以为湖南栎类次生林的经营措施提供科学理论依据。

【Objective】In order to provide theoretical basis for management measures and growth harvest estimation,a stand basal area growth model was established for the secondary Oak forest in Hunan province.【Method】The sample plots with Oak secondary forest of the dominant tree species or main tree species in the six periods of national continuous inventory data(1989-2014)in Hunan were taken as the objects.Seven kinds of common growth theory equations were used to construct the basic model with the dependent variety(Stand basal area)and independent variety(age).Comparative the evaluation indexes,chosed the best fitting effect basic model to constructed and with site index,stand age and stand number was constructed the mixed effect model(stand number was a random variable)and the parametric model(stand number was a continuous variable),and their simulation performances were accordingly evaluated.【Result】The prediction accuracy of the three models is from high to low:parameterized model(98.36%),mixed effects model(97.71%),basic model(92.84%).Finally,the parametric model was used as the basal area growth model of Oak secondary forest in Hunan province.When any two factors of stand age,stand number and site index are the same,the total growth of stand basal area(5-year periodic growth of stand basal area)increases with the increase of another factor,and the greater the density,the smaller the gap of total basal area growth between the two adjacent densities;5-year periodic growth of stand basal area reaches the maximum,the higher the density,the faster the growth decreases;Other factors were the same,the more the stand number,the earlier the maximum growth appeared at 20 years.The larger the site index is,the greater the 5-year periodic growth of stand basal area is.【Conclusion】The stand basal area growth curve and the 5-year periodic stand basal area growth curve of Oak secondary forest generated by the parametric model with the number of stand trees as the continuous variable are in line with the stand growth pattern,and the prediction accuracy is relatively high,which can provide scientific theoretical basis for the management measures of Oak secondary forest in Hunan.