不同林分密度指标在杉木林分蓄积量模型的应用研究

Develop Annual Stand Volume Growth Model of Chinese fir Including Different Stand Density Indices

[目的]林分密度是反映单木林分中林木株树和竞争的一个重要指标,构建林分生长与收获模型的一个重要变量。选择合适的林分密度指标来构建杉木林分蓄积量模型,提高林分预测精度。[方法]以福建邵武杉木(Cunninghamia lanceolata)人工林密度长期试验林28 a连续观测数据为依据,基于可变生长率法,建立了含5种林分密度指标的杉木林分蓄积年生长模型。[结果]模型决定系数R^(2)均在0.979以上,精度高于不含密度指标的对照组模型。在包含密度指标的模型中,精度最高的为每公顷株数N密度模型,其次是相对植距RS密度模型,但是这两个模型参数估计不显著而被舍弃。所有模型的R^(2)数值由高到低顺序为:每公顷株数N林分蓄积量模型(0.9799)、相对植距模型(0.9799)、林分密度指数SDI模型(0.9794)、优势高营养面积比Z模型(0.9793)、Nilson密度指数模型(0.9790)以及不含密度指标模型(0.9728)。[结论]除去N指标和RS指标模型,杉木林分蓄积量模型中表现最好的是以林分密度指数SDI为密度指标的模型。其次,还发现在低造林密度(1667~3333株·hm-2)林分,蓄积生长量要大于中高造林密度(5000~10000株·hm-2)的林分。

[Objective]Stand density is an important index to reflect the number and competition in a stand.It plays a critical role in stand growth models.It is of great significance to analyze the application value of stand density index in stand volume growth model for accurate prediction.[Method]Based on the 28 years continuous observation data of the spacing trials of Chinese fir(Cunninghamia lanceolata)plantation in Shaowu,Fujian Province,the annual growth model of stand volume of Chinese fir including five different density indices respectively were developed based on the variable rate method,as well as the model without stand density index.[Result]The R^(2)values of the models including density indices were all larger than 0.979,and the model performance was higher than that of the model without density index.Among the five models including stand density indices,the model including living number of trees per ha(N)had the largest value of R^(2),followed by the model with RS density.However,the two models are not feasible because of the parameter estimates of stand density index were not significant.The R^(2)values of all models from high to low were:stand volume model including N(0.9799),relative spacing RS(0.9799),stand density index SDI(0.9794),dominant high nutrient area ratio Z(0.9793),Nilson density index model(0.9790)and without density index(0.9728).[Conclusion]Accounting for significance of the parameter estimate,the model with stand density index SDI performed the best in the stand volume model of Chinese fir.In addition,stand volume in stands of planting density(1667~3333 trees·hm)was larger than the denser stands(5000~10000 trees·hm).