Climate-sensitive Dynamic Prediction Model Of Diameter Distribution Of Cunninghamia Lanceolata Plantation

Under the background of climate warming,forests,as an important carrier of ecosystems,are undergoing severe tests.Stand diameter distribution is the most significant and foundamental stand structure,which can be served as an crucial foundation for formulating forest management measures.Therefore,it is of great significance to explore the influence of climate on the diameter distribution of Cunninghamia lanceolata plantation,to scientifically carry out the management decision of Cunninghamia lanceolata plantation under the background of climate change,and to improve the forest quality of Cunninghamia lanceolata plantation.Based on the three-period survey data of 40 Cunninghamia lanceolata plantation plots in Chongyi County,Ganzhou City,Jiangxi Province,this study analyzed the diameter distribution of 40 Cunninghamia lanceolata plantation plots based on Weibull distribution.The regression models of Weibull distribution parameters b and c with stand,site and climate factors were established by using parameter prediction models.The model parameters were estimated by seemingly unrelated regression to analyze the influence of climate on the diameter distribution of Cunninghamia lanceolata plantation.The results show that:(1)Weibull distribution was used to fit the three-period data of 40 plots one by one,and Kolmogorov-Smirnov test was used to test the distribution.The P values of all plots were greater than 0.05,that is,all the three-period data of 40 plots passed the test.(2)The regression model of scale parameter b and shape parameter c with stand,site and climate factors was constructed by using the parameter prediction model,and the model was evaluated by 3-fold cross validation.The R_a~2 value of scale parameter b was 0.7569,RMSE was 1.9732,MAE was 1.5433,and the R_a~2 value of shape parameter c model was 0.6815,RMSE was 0.5125,MAE was 0.4301.The average DBH and site index of the stand were significantly correlated with the scale parameter b.The stand age,average DBH,site index,slope and annual precipitation were significantly correlated with the shape parameter c.(3)Based on the constructed parameter prediction model,the influence of precipitation change on the diameter distribution of Cunninghamia lanceolata plantation was simulated.With the increase of precipitation,the number of small-diameter trees will gradually increase,and this trend will not change with the change of density and stand.