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固定二氧化碳和火灾后植被恢复的影响。在萨哈共和国首府雅库茨克附近的一片成熟落叶松林中进行了人工地面火灾。在2002年严重烧毁的两个落叶松林中，观察到植被的恢复。人工地面火燃烧的有机物总量是对照场地的48%，估计为低强度或中等强度的地面火。最高地表温度为485℃。5 cm土层土壤温度高达116℃，持续3小时保持在50℃以上。火烧后落叶松树冠的光合作用下降率在下午较对照显著降低。这一现象被认为是落叶松可以利用地表火烧毁的林地植被所消耗的土壤水分。植被恢复受林火强度和土壤水分条件的影响。湿地植被覆盖比旱地快，但旱地落叶松生长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场地生长。这些落叶松幼林的碳释放量估计为34~37tC/ha。估计这种人工表面火灾的影响需要几年时间，因为据报道，表面火灾后落叶松会枯死好几年。

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.