Fixing a snag in carbon emissions estimates from wildfires
Fixing a snag in carbon emissions estimates from wildfires
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DOI：
10.1111/gcb.14716
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发表时间：
2019-07
影响因子：
11.6
通讯作者：
J. Stenzel;K. Bartowitz;M. Hartman;J. Lutz;C. Kolden;A. Smith;B. Law;M. Swanson;A. Larson;W. Parton;T. Hudiburg
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作者：
J. Stenzel;K. Bartowitz;M. Hartman;J. Lutz;C. Kolden;A. Smith;B. Law;M. Swanson;A. Larson;W. Parton;T. Hudiburg
野火是一个重要的地球系统过程，影响生态系统过程和碳循环。森林火灾正变得越来越频繁和严重，但在植被和碳动力学上的火灾模型存在差距。减少野火二氧化碳（CO2）排放的策略包括增加树木收获，这在很大程度上是基于公众的假设，即火灾会将活森林夷为平地，尽管观察表明实际消耗的成熟树木生物量不到5%。这种误解也反映在模型中过度燃烧活树。在这里，我们表明，区域排放量估计使用广泛实施的燃烧系数是59%-83%的排放量的基础上，实地观察。使用独特的现场数据集之前和之后的野火和改进的生态系统模型，我们提供了强有力的证据表明，这些大的高估可以通过使用现实的生物量燃烧因子，并通过准确地量化生物量在火灾后几十年到几个世纪的分解站死树（“障碍”）。大多数模型的开发侧重于燃烧面积，我们的研究结果表明，准确地表示燃烧也是必不可少的量化火灾对生态系统的影响。使用我们的改进，我们发现美国西部森林火灾在过去17年中排放了851 ± 228 Tg CO2（约为替代估计的一半），与整个地区化石燃料的16，200 Tg CO2相比，这是微不足道的。
Wildfire is an essential earth‐system process, impacting ecosystem processes and the carbon cycle. Forest fires are becoming more frequent and severe, yet gaps exist in the modeling of fire on vegetation and carbon dynamics. Strategies for reducing carbon dioxide (CO2) emissions from wildfires include increasing tree harvest, largely based on the public assumption that fires burn live forests to the ground, despite observations indicating that less than 5% of mature tree biomass is actually consumed. This misconception is also reflected though excessive combustion of live trees in models. Here, we show that regional emissions estimates using widely implemented combustion coefficients are 59%–83% higher than emissions based on field observations. Using unique field datasets from before and after wildfires and an improved ecosystem model, we provide strong evidence that these large overestimates can be reduced by using realistic biomass combustion factors and by accurately quantifying biomass in standing dead trees that decompose over decades to centuries after fire (“snags”). Most model development focuses on area burned; our results reveal that accurately representing combustion is also essential for quantifying fire impacts on ecosystems. Using our improvements, we find that western US forest fires have emitted 851 ± 228 Tg CO2 (~half of alternative estimates) over the last 17 years, which is minor compared to 16,200 Tg CO2 from fossil fuels across the region.