Effect of surface fires on the fixation of carbon dioxide by eastern Siberian taiga

本项目的目的是评估地表火灾对东西伯利亚针叶林对二氧化碳的固定和火灾后植被恢复的影响。在萨哈共和国首都雅库茨克附近的一处成熟的落叶松森林进行了人工地面火灾。在2002年发生严重火灾的两处落叶松林中，植被恢复。人工地表火燃烧的有机质总量为对照点的48%，估计为中低强度地表火。土壤表面最高温度为485℃。5cm深度土壤温度达到116℃，保持温度在50℃以上3小时。火灾后下午落叶松树冠光合速率的下降与对照区相比显著降低。这种现象是假设地表火灾燃烧的森林地面植被所利用的土壤水分可以被落叶松所利用。植被恢复受火灾强度和土壤水分条件的影响。湿地植被覆盖发育速度快于干地，但干地落叶松幼苗数为2.2株/m^2。落叶松幼苗几乎不生长，但许多桦树幼苗在潮湿的地方生长。这些幼龄浓密落叶松林的碳释放量估计为34 ~ 37tC/ha。由于据报道，地表火灾后落叶松的枯死会持续数年，因此对这种人工地表火灾影响的估计需要数年时间。

The object of this project is to estimate the effects of surface fires on the fixation of carbon dioxide by eastern Siberian taiga and vegetation recovery after a fire. Artificial surface fire was carried out at a mature larch forest near Yakutsk, the capital city of Sakha Republic. Vegetation recovery was observed in two larch forests which burned severely in 2002. The total amount of organic matters burned by the artificial surface fire was 48% of a control site and was estimated low or middle intensity of surface fire. Maximum soil surface temperature was 485℃. Soil temperature at 5cm depth reached 116℃ and kept more than 50℃ for 3 hours. Depression of photosynthesis rate of larch crown in the afternoon decreased significantly compared with the control site just after fire. This phenomenon is assumed that soil water which is used by burned forest floor vegetation by the surface fire could be used by larch trees. Vegetation recovery was influenced by the intensity of fire and soil moisture conditions. Vegetation cover developed faster in a wet site than in a dry site, but 2.2 seedlings/m^2 of larch grew in the dry site. Larch seedlings hardly grew but many birch seedlings grew in wet site. Carbon release of these young and dense larch forests was estimated 34〜37tC/ha. The estimation of the effects of this artificial surface fire needs several years because dieback of larch trees after surface fire was reported to occur for several years.