The Change of Larix olgensis Stem Form under Different Fertilization Treatments
This study investigates the effects of different fertilization treatments on the stem morphology of Larix olgensis planta-tions by establishing a universal tree taper equation.Based on the analyzed wood data from L.olgensis plantations in the Mengjiagang Forest Farm,Jiamusi City,Heilongjiang Province,under various fertilization treatments(application of N fer-tilizer,NP fertilizer,NPK fertilizer,and a blank control),the optimal basic model is selected from commonly used taper equation models in forestry.The model is optimized using dummy variable methods and nonlinear mixed-effects modeling to analyze the influence of different fertilization treatments on trees of varying grades.The results showed that among the basic models,the Kozak(2004)equation provides the best fit.The introduction of dummy variable models,coupled with mixed-effect models at both fertilization levels and tree levels,enhances the goodness of fit.Notably,the mixed-effect model based on nested fertilization and tree levels yields the highest prediction accuracy(R2=0.991),effectively eliminating much of the autocorrelation between observations.In simulations of trunk morphology,it is found that fertilization has the greatest impact on dominant trees(diameter at breast height(Ddh)≥18 cm),followed by average trees(11 cm≤Ddh＜18 cm)and suppressed trees(Ddh＜11 cm).The application of NP fertilizer significantly increases the diameter of the upper trunk(relative height 0.6-1.0)of dominant and average trees.The effects of N fertilizer and NPK fertilizer are similar but slightly lower than those of NP fertilizer.The highest accuracy in predicting trunk diameters at different heights is achieved using the mixed-effect model based on nested fertilization and tree levels.The impact of different fertilization treatments on the stem morphology of artificial L.olgensis is mainly concentrated in the middle and upper portions of the trunk,sugges-ting that nitrogen-phosphorus fertilizer should be applied to dominant trees,while nitrogen fertilizer should be applied to average and suppressed trees.
万方数据
维普
