同龄纯林自然稀疏过程的经验模型研究

应用-3/2法则及广义Schumacher生长方程导出同龄纯林自然稀疏过程中密度随时间变化规律新模型,采用遗传算法对非线性模型参数进行最优估计.以山杨、云南松、杉木等树种同龄纯林自疏过程中密度随时间变化资料对新模型进行了验证,并与前人提出的主要森林自疏过程密度随时间变化规律模型进行了对比.结果表明,所提出的同龄纯林自疏规律模型能很好地拟合实际观测资料,具有良好的使用价值;新模型拟合效果较前人提出的自疏规律模型效果均更佳,说明新模型是一个描述同龄纯林自疏过程密度随时间变化规律的理想经验模型,可在森林自疏规律研究中应用.杉木林自疏过程密度变化规律的研究可为南方林区杉木林经营管理提供参考.

Experience model for self-thinning process of even-aged pure stands

Based on the famous-3/2 power rule and generalized Schumacher growth equation,a mathematical model for the density change of even-aged pure stands with time during self-thinning process was presented,and the genetic algorithms was used to fit this nonlinear model.With the collected data from Populus tremula var.davidiana,Pinus yunnanensis and Cunninghamia lanceolata even-aged pure stands,the new model was verified and compared with other models.The results showed that the new model could fit observed data very well,and was very useful in practice.The surplus square,mean relative error,mean absolute error and surplus standard deviation of the new model were all smaller than those of other models,indicating its good qualification in describing stand density change during self-thinning process and its useness in studying forest self-thinning rules.The study also showed that genetic algorithms could give a better global convergence,and be used to estimate the parameters of nonlinear models in ecology,biology and forestry.