Interactions between warming and wildfires in the last decade in Siberia

西伯利亚野火有两种燃烧类型：一种是林分替换火，燃烧森林地面和树冠，另一种是只燃烧森林地面的地表火。换林火燃烧过程中平均释放的二氧化碳约为23tC/ha，地表火燃烧过程中平均释放的二氧化碳约为2.3tC/ha。然而，通过卫星图像解释这两种不同类型的火灾，以前几乎没有研究过。在估算燃烧过程和森林恢复过程中二氧化碳的释放时，必须对林分替换和地表火灾进行分离分析。在此背景下，建立了利用中分辨率成像光谱仪（MODIS）估算林分、地表火灾等土地类型土地覆盖面积的算法。MODIS分辨率为1km，观测周期为1天。其次，利用MODIS估算2002-2010年5 - 9月每m月的土地类型地理分布。利用月土地分类分数面积数据，估算了林分置换火灾和地表火灾月发生量的地理分布。通过与Landsat TM数据估算的土地类别的分数面积进行比较，对估算结果进行了评估。Landsat TM分辨率为30m，观测周期为16 d。由于受云层污染的影响，实际观测周期超过两个月，因此Landsat TM数据本身无法用于每月的火灾发生分析。通过与气温、降水等气象资料的比较，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与降水均呈正相关。特别是在降水量非常少的年份，林分置换和地表火灾的燃烧面积都非常显著。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