The Study Of Dynamic Predicting Model Of Height To Crown Base For Mongolian Pine Plantation In Heilongjiang Province

Taken Mongolian Pine(Pinus sylvestris L.var.mongolica Litv.)plantations as the object,the research applied two methods(i.e.indirect method and direct method)to evaluate the prediction of the height to crown base dynamic.Based on the simultaneous equation theory and measured data of 22 permanent sample plots in Mongolian Pine plantations from Maoershan Experimental Forest Farm,Hengtoushan Forest Farm,Mengjiagang Forest Farm in Heilongjiang Province,the height to crown base dynamic models were developed by using the method of parameterization and all subset regression.With the help of model parameters and drawing corresponding curves,the influence of stand variables on the height,height to the crown,height increment and height to the crown increment was analyzed.And the respective advantages and disadvantages of indirect method and direct method are compared.The indirect method is based on the height growth and static height to crown base model to establish the process of height to crown base growth.The direct method is to directly develop height to crown base dynamic model.The results are followed:1.Compared with the model without the stand conditions,the adjusted coefficient determination(Ra2)increased 5.56%,the evaluation prediction increased 1.01%in height growth models and the adjusted coefficient determination(Ra2)increased 8%,the evaluation prediction(P%)increased 1.01%in height to crown base model.What's more,the root-mean-square error(RMSE),mean error(ME)and mean absolute error(MAE)had a certain degree of reduction.The results showed that the fitting effect of models were improved after adding stand factors,which could well predict height and height to crown base in different stand conditions.2.Select the height growth model based on logistic form difference equation and height to crown base model with DBH,G,HD simulated as the optimal simultaneous equation.The adjusted coefficient determination(Ra2)was 0.9543,the root-mean-square error(RMSE)was 1.08m,the evaluation prediction(P%)was 99.14%in height growth model and the adjusted coefficient determination(Ra2)was 0.9302,the root-mean-square error(RMSE)was 1.12m,the evaluation prediction(P%)was 98.53%in height to crown base model.3.Select the height increment model based on logistic form difference equation and height to crown base increment model with CR,HDR,HD simulated as the optimal simultaneous equation.The adjusted coefficient determination {Ra1)was 0.2846,the root-mean-square error(RMSE)was 1.32m,the evaluation prediction(P%)was 71.80%in height increment model and the adjusted coefficient determination(Ra2)was 0.3598,the root-mean-square error(RMSE)was 1.24m,the evaluation prediction(P%)was 73.73%in height to crown base increment model.4.From the model fitting result,indirect method fitting effect is better than the direct method.The reason is that models used in indirect method had good theoretical bases.And from the model calculation process,the direct method of calculation was more simple than the indirect method because the direct method could directly calculated the height to crown base increment.The specific application of the two methods should be based on actual situation.