Individual Tree Diameter Increment Model For Natural Betula Platyphylla Forests Based On Meteorological Factors

In order to reflect the effects of climate change on tree growth in large-scale regions,the individual tree increment model based on meteorological factors and growth model with regional effects were constructed.The data set used in this study came from the 212 re-measured permanent sample plots for natural Betula platyphylla forests in Daxing,an Mountains and Xiaoxing,an Mountains and 30 meteorological stations data which covered the research area.The individual tree factor,competition factor,site condition and climatic variables that affect the growth of B.were constructed,and do the correlation analysis.The differences of stand and meteorological factors between Daxing'an Mountains and Xiaoxing'an Mountains were analyzed and the diameter increment model including the meteorological factors was developed by dummy variable approach.The results showed that effect of competitive factor growth in two areas is the ratio of basal area of larger trees to target tree diameter?BAL/D?and total stand basal area?BAS?;individual tree factor is the logarithmic diameter?lnD?and square diameter?D²?.Site factors such as elevation,also significantly affected the growth.Because of the colinearity problem in the simulation process,it was not included in the model.The minimum temperature(T_gmin)and mean precipitation(P_gm)in growing season were the main meteorological factors which affected the diameter increment.T_gmin and P_gm were positively correlated with the diameter increment,but the influence strength of T_gmin was obviously different between the two research areas.The adjusted coefficient of determination R_a² of the diameter increment model with meteorological factors was 0.56 and had an 11%increase compared to the one without meteorological factors.It is concluded that meteorological factors can well explain the diameter increment of B.The adjusted coefficient of determination R_a²of the model with regional effects was 0.59,and increased by 18%compared to the one without regional effects,and effectively solved the incompatible problem of parameters between two research areas.The validation results showed that the individual tree diameter growth model with meteorological factors and regional effect had the best prediction accuracy in estimating the diameter increment of B.The mean error?ME?,mean absolute error?MAE?,mean relative error?MRE?and mean relative absolute error?MRAE?were0.0086,0.4476,5.8%and 20.0%,respectively.Overall,dummy variable model of individual tree diameter increment based on meteorological factors can well describe the diameter increment process of natural B.in Daxing,an Mountains and Xiaoxing,an Mountains.Furthermore,it will provides detailed forest growth information for the intensive management and production decision of natural B.Forest in this area,and has certain theoretical and practical value.