Building Mixed Effects Model of Stand Volume of Nature Pinus densata Forest in Shangri La

In this paper, we took natural Pinus densata forest of ShangriLa City of Yunnan Province as the research object to establish a mixed effects model stand volume. At the same time, we construct the mixed effects models of stand volume which contain the environment factors, including stand factors and elevation etc. All models were estimated by indexes of fitting and Independent Samples Test. The results showed that compared with general regression model, the result of mixed effects model was better in stand volume fitting; The mixed effect model which introduced environment factors was better than the model which did not. And the best model was that used the stand factors. In view of the independence test of model, the prediction precision of general fixed effects model was the highest, its absolute mean relative error was least. The sum relative error and mean relative error decreased by introducing environment factors, and the one that stand factors introduced was the best. General regression model was bad at error and precision aspect compared with mixed effects model.