Prediction model system with dummy variables for carbon storage of larch plantation in Heilongjiang Province, China

Based on monitoring data from fixed plots of larch plantation in Heilongjiang Province obtained in 2005 and 2010, we analyzed the relationship among stand variables of larch plantation in Heilongjiang Province and established site class index curve model and stand density index model. A two-stage least square method was used to establish a simultaneous equations system for predicting average basal area and carbon storage of stands. Together, they were called prediction model system for carbon storage of larch plantation in Heilongjiang Province. The system included two dummy variables of age group and region. Results showed that the determination coefficients of those models were all greater than 0.98, and the root mean square errors were less than 4, except for the site class index curve model. The model with dummy variables increased the determination coefficient, and the root mean square error was less than 3, indicating that the model had good stability with accutrate estimated parameters. The average relative error of all models was less than 2%, the absolute value of the average relative error of most models was less than 15%, and the accuracy of all models was above 95%, indicating that the models could be used to accurately predict the carbon storage of larch plantations in different regions and age groups in Heilongjiang Pro-vince. According to the analysis of the site class index curve model and the estimated parameters of the simultaneous equations, the greater stand age, the larger stand average height, average basal area and carbon storage when the survey plots were located in the same area, which fitted natural growth rules. Under the same stand but different regions, the stand average height decreased in the order of plain area, southern slope area of Xiao-xing'anling, eastern slope area of Zhangguangcai-ling, Wandashan area, western slope area of Zhangguangcailing, and northern slope area of Xiao-xing'anling, while the order of stand basal area and carbon storage was eastern slope area of Zhangguangcailing, northern slope area of Xiaoxing'anling, western slope area of Zhangguangcailing, southern slope area of Xiaoxing'anling, Wandashan area, and plain area.