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结合遥感和林分因子的森林地上碳储量动态估测模型构建
Establishment of Forest Dynamic Aboveground Carbon Stock Estimation Model Combining Remote Sensing Factors and Forest Stand Factors
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摘要: 以香格里拉市高山松为研究对象,基于1987—2017年国家森林资源清查数据和Landsat时间序列数据,计算30 a期间碳储量、遥感因子和林分因子的5、10 a定期变化量、年平均变化量;通过相关性分析提取与高山松地上碳储量相关性较高的遥感和林分因子,采用随机森林方法构建地上碳储量估测模型,在遥感因子变化量建模的基础上结合郁闭度、平均年龄两2个林分因子,以期提高森林地上碳储量估测的精度。结果表明:遥感因子结合平均年龄10 a变化量建模效果最好,其R2为0.882、RMSE为0.398 t/(hm2∙a)、P为0.755;采用3类变化量构建森林地上碳储量动态估测模型,基于10 a定期变化量的模型拟合效果和预测精度最优;遥感因子结合平均年龄的建模效果要优于结合郁闭度建模,其5、10 a、年均变化量建模R2提升效果分别为5.16%、2.86%、1.39%。本研究表明纹理因子能够有效反映森林地上碳储量的变化,遥感因子结合林分因子变化量构建的碳储量估测模型能够有效提高森林地上碳储量动态估测的精度。Abstract: Taking the Pinus densata in Shangri-La City as the research object, based on the 1987-2017 national forest inventory data and Landsat time-series data, we calculated the 5-year and 10-year periodical changes and annual average changes of carbon stock, remote sensing factor and stand factor over a period of 30 years, and extracted remote sensing factor and stand factor that had higher correlation with the aboveground carbon stock of Pinus densata through correlation analysis, with the aim of improving the accuracy of forest aboveground carbon stock estimation. Through correlation analysis, we extracted remote sensing factors and stand factors with higher correlation with aboveground carbon stock of alpine pine, and constructed an aboveground carbon stock estimation model by using the random forest method, and combined the stand factors with the modeling of changes in remote sensing factors, in order to improve the accuracy of aboveground carbon stock estimation in two forests of canopy density and mean age. The results showed that the modeling effect of remote sensing factor combined with 10 year change in mean age was the best, with R2 of 0.882, RMSE of 0.398 t/(hm2∙a), and P of 0.755. Three types of changes were used to construct a model for estimating the dynamics of aboveground forest carbon stock, and the model based on 10 year regular change had the best fitting effect and prediction accuracy. The modeling effect of remote sensing factor combined with average age was better than that combined with depression, and its R2 enhancement effect was 5.16%, 2.86%, and 1.39% for the modeling of 5year, 10 year, and annual average amount of change, respectively. This study shows that the texture factor can effectively reflect the changes of aboveground carbon stock in forests, and the carbon stock estimation model constructed by combining the remote sensing factor with the changes of stand factor can effectively improve the accuracy of the dynamic estimation of aboveground carbon stock in forests.