Abstract: The first generation introduction of Mongolian scots pine (Pinus sylvestris var.mongolica) plantations on sandy land has been implemented in Zhanggutai in northwest Liaoning Province,China,and the final felling regeneration stage has been reached after the plantations grow for more than 50 years.In this study,the tree height growth of the first generation of Mongolian scots pine plantations on sandy land was summarized,and a theoretical basis was provided for further studying and analyzing the impact of plant diseases and insect pests on the tree height growth.The 14 candidate models were selected to fit the tree height-age relationship based on the data from 31 temporary sample plots of Mongolian scots pine plantations on sandy land located in Zhanggutai in northwest Liaoning Province,China.The models were evaluated and tested to identify the best model for the growth of Mongolian scots pine plantations on sandy land.Furthermore,the best model and the data of analytic trees suffered from plant diseases and insect pests were used to fit the individual tree height growth process.The annual growth and average growth of the plantations suffered from plant diseases and insect pests and those of the initially-protected mature plantations were calculated to provide some references for further studying and analyzing the impact of plant diseases and insect pests on tree height growth.The results indicated that the Richards model was adopted to develop the models for the tree height growth of Mongolian scots pine plantations on sandy land.A best fitting of the Richards model was achieved among the 14 candidate models to predict the tree height of Mongolian scots pine plantations on sandy land,which provided the most accurate of predicting the tree height growth with the lowest mean absolute error (MAE),residual sum of squares (SSE) ,root mean square error (RMSE) and the highest coefficient of determination (R²).Moreover,the Richards model could also be used to make an efficient fitting to the tree height growth of the plantations suffered from plant diseases and insect pests.After compared the predicted curves of tree height growth of the healthy plantations and the plantations suffered from plant diseases and insect pests,it was found that the Mongolian scots pine plantations about 16 years old on sandy land in the study area began to suffer from plant diseases and insect pests.The disturbance of plant diseases and insect pests could reduce 30.57% average maximum of tree height of Mongolian scots pine plantations on sandy land compared with the healthy plantations.As a result the maturity of initially-protected plantations could advance for 6 years,and the tree height of the plantations suffered from plant diseases and insect pests was decreased by 27.92%.However,the impact of plant diseases and insect pests on the maximums of annual growth and of average growth of the 16-year-old Mongolian scots pine plantations was not so significant in Zhanggutai.

Key words: Pinus sylvestris var.mongolica, sand-fixation forest, tree height, insect pests, growth model, growth