Analysis Of Influence Factors Of Height Growth Of Pinus Sylvestris Var.mongolica In Zhanggutai In Liaoning Province

Competition,disturbance and climate change are the main factors affecting tree growth and stand change,the effects of these factors on tree height growth need to be further studied.Based on a combination of multiple dataset including tree height measured in pure Mongolian pine(Pinus sylvestris var.mongolica)stands with different age and different densities,measurements of analyze stems with and without insect pest,as well as the climate data of Zhanggutai,we conducted a work to reveal the growth patterns of tree height growth of Mongolian pine under different conditions.First,the height growth along the competition gradient were analyzed.Second,we analyzed the difference between insect-infected and healthy individuals.Additionally,a dynamic height model incorporating climate factors and random parameters was developed to realize the dynamic height prediction under future climate change.It is suitable to maintain the stand density around 1425 plants per hectare before closing and self-thinning.Both individual tree height and average stand height were the fastest in stand with the density of 1425 plants per hectare.In mature stands,it is more advantageous for tree growth and stand accumulation to maintain the stand density at about 750 plants per hectare through appropriate thinning.The Richards model was adopted to develop tree height models of Mongolian pine plantations on sandy land.By comparing the predicted tree height growth curves of health and disturbed by diseases insect pests,we found that Mongolian pine plantations are disturbed by diseases and insect pests around 16 a in Zhanggutai.When compared with healthy trees,diseases and insect pests disturbance meanly reduced 30.57% on average maximum of tree height of Mongolian pine plantations on sandy land,as a result of the initial protective maturity age advanced by 6 years and tree height decreased by 27.92% when growing to the initial protective maturity age.Therefore,diseases and insect pests disturbance can greatly shorten the growth process of Mongolian pine.In addition,maximum of current annual increment and maximum of average increment were not affected significantly when this species is disturbed by diseases and insect pests around 16 a in Zhanggutai.The Richards model with the mean temperature of the May(MTM),precipitation from October of year to April of year(PNP),precipitation in the previous year during growing season(PGP)has significantly improved the accuracy of the model.When estimate the tree height by the model,tree height increased with the increase of MTM and PNP,and decreased with the increase of PGP.In summary,Mongolian pine needs higher density to promote growth in young stage,whilehigher density in mature stage will inhibit tree growth.Although diseases and insect pests disturbance did not reduce the maximum growth increment,it would reduce the maximum of tree height and shorten the protective time of Mongolian pine forest.The mixed effect generalized model with climate factors can well realize the dynamic prediction of tree height.