Interactions between warming and wildfires in the last decade in Siberia

西伯利亚野火有两种燃烧类型：一种是林分替代火，烧毁森林地面和树冠；另一种是地面火，只烧毁森林地面。在燃烧过程中，替代林火的平均二氧化碳释放量约为23tC/ha，地面火的平均二氧化碳释放量约为2.3tC/ha。然而，通过卫星图像对这两种不同的火灾类型进行解释之前几乎没有研究。对于估计燃烧和森林恢复过程中的二氧化碳排放量，有必要对林分更替和地面火灾进行分析。在此基础上，建立了利用中分辨率成像光谱仪(MODIS)估算退耕还林和地面火灾等土地覆盖面积的算法。MODIS分辨率为1公里，观测周期为1天。其次，根据MODIS对每m…土地类别的地理分布进行了估算2002-2010年5月至9月的较多月份。根据每月的土地类别面积数据，估计了每月发生的林分火灾和地面火灾的地理分布。通过与从Landsat TM数据估算的土地类别的部分面积进行比较，对该估计进行了评估。陆地卫星TM的分辨率为30m，观测周期为16天。由于云层污染，实际观察期超过两个月，陆地卫星TM数据本身不能用于每月的火灾发生分析。通过将估计的火灾发生次数与温度、降水等气象资料进行比较，分析了西伯利亚地区火灾发生与气候的关系。结果表明，林分更替和地表火灾均与降水量呈正相关。特别是，在降水量极小的年份，林分更替和地面火灾的烧毁面积都很显著。较少

Siberian wildfires have two burn types : one is stand-replacing fire that burns both forest floor and crown, and the other is surface fire that burns only forest floor. The average carbon-dioxide release during combustion is about 23tC/ha for the stand-replacing fire and 2.3tC/ha for the surface fire. However, the interpretation of these two different fire types through satellite images were hardly studied before. The analyses with the separation of the stand-replacing and surface fires are necessary for estimating carbon-dioxide releases during the combustion and in the forest recovery process. Based on these backgrounds, the algorithm for estimating the fractional land cover areas of the stand-replacing and surface fires and other land categories from the Moderate Resolution Imaging Spectroradiometer (MODIS) was built. The resolution of MODIS is 1km and the observation period is one day. Next, The geographical distributions of the land categories were estimated from MODIS for every m … More onth from May to September in 2002-2010. From the monthly land-category fractional area data, the geographical distributions of the monthly occurrences of stand-replacing fire and surface fire were estimated. The estimation was evaluated by comparing with the fractional areas of the land categories estimated from Landsat TM data. The resolution of Landsat TM is 30m and the observation period is 16 days. The Landsat TM data itself cannot be used for the monthly fire occurrence analysis since the actual observation period is more than two months due to the cloud contamination. By comparing the estimated fire occurrences with meteorological data such as temperature and precipitation, the relationship between the fire occurrence and the climate was analyzed in Siberia. As a result, both the stand-replacing and surface fires have positive correlations with the precipitation. Especially, in the year the areas burnt by both stand-replacing and surface fires were remarkable in the year when the precipitation is remarkably small. Less