华北落叶松人工林差分地位指数模型构建

Construction of Difference Site Index Model for Larix Principis-rupprechtii Plantation

以阴山山地苏木山林场华北落叶松人工林为研究对象,利用43株解析木数据,基于Richards方程构建差分地位指数模型。结果表明:差分模型拟合结果明显优于基础模型,R^(2)均在0.96以上,RMSE在0.86~0.96之间,MAE在0.42以下。ADA法推导的模型,以b或c为自由参数拟合结果要好于以a为自由参数;GADA法推导的模型,假设自由参数c与变量X_(0)成线性关系更合理。通过统计分析、残差分析和地位指数曲线簇比较,采用GADA法,假设自由参数a=e^(X_(0)),c=c_(1)+c_(2)X_(0)所推导的差分模型为最佳模型,满足生物学和统计学两方面的要求。地位指数越大,优势木树高及其连年生长量的极值也越大,到达拐点的时间也越早。研究结果可为华北落叶松人工林立地质量科学评价提供依据。

In the paper,the Larix principis-rupprechtii plantation in Sumu Mountain forest farm of Yin Mountain was taken as the research object.Based on the data of 43 analytic trees,the difference site index models were constructed based on Richards equation.The results showed that the difference model fitting results were significantly better than the basic model,with R^(2) above 0.96,RMSE between 0.86 and 0.96,and MAE below 0.42.The model derived by ADA method,the fitting result with b or c as free parameter is better than that with a as free parameter.In the model derived by GADA method,it is more reasonable to assume a linear relationship between the free a parameter and the variable X_(0).Through such methods as statistical analysis,residual analysis and site index curve cluster comparison,by applying GADA method,the difference model derived by free parameters a=e^(X_(0)),c=c_(1)+c_(2)X_(0) is the best model,which meets the requirements of biology and statistics.Higher site index has the greater extreme value of tree height and annual growth of dominant trees,and the earlier the curve reaches the inflection point.The results can provide basis for the scientific evaluation of site quality of Larix principis-rupprechtii plantation.