摘要：2007年，阿拉斯加冻原上的一个面积超过1000平方公里的区域被一次火灾毁掉，使1950年以来该地区累积被烧面积增加一倍以上。现在，Michelle Mack及其同事发现，在这个过程中，2.1万亿克的碳被释放出来，土壤有机质总深度的约1/3被烧掉，从而使永久冻土有可能融化。在整个燃烧过程中释放的碳的数量，相当于20世纪过去25年整个北极冻原生物群落每年的净碳汇。由于随气候变暖冻原火灾预计会增加，所以原始冻原土壤燃烧可能会构成一个正的气候反馈，其方式是：将表层土壤碳转移到大气中，加快深层永久冻土碳的融化和分解。
生物探索推荐英文论文摘要：
Nature 475, 489–492 (28 July 2011)
Doi:10.1038/nature10283
Carbon loss from an unprecedented Arctic tundra wildfire
Abstract:
Arctic tundra soils store large amounts of carbon (C) in organic soil layers hundreds to thousands of years old that insulate, and in some cases maintain, permafrost soils. Fire has been largely absent from most of this biome since the early Holocene epoch, but its frequency and extent are increasing, probably in response to climate warming. The effect of fires on the C balance of tundra landscapes, however, remains largely unknown. The Anaktuvuk River fire in 2007 burned 1,039 square kilometres of Alaska’s Arctic slope, making it the largest fire on record for the tundra biome and doubling the cumulative area burned since 1950. Here we report that tundra ecosystems lost 2,016 ± 435 g C m−2 in the fire, an amount two orders of magnitude larger than annual net C exchange in undisturbed tundra. Sixty per cent of this C loss was from soil organic matter, and radiocarbon dating of residual soil layers revealed that the maximum age of soil C lost was 50 years. Scaled to the entire burned area, the fire released approximately 2.1 teragrams of C to the atmosphere, an amount similar in magnitude to the annual net C sink for the entire Arctic tundra biome averaged over the last quarter of the twentieth century. The magnitude of ecosystem C lost by fire, relative to both ecosystem and biome-scale fluxes, demonstrates that a climate-driven increase in tundra fire disturbance may represent a positive feedback, potentially offsetting Arctic greening8 and influencing the net C balance of the tundra biome.
