期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：43
页码：13261-13266
DOI：10.1073/pnas.1500796112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceIn the western United States and other forested regions, climate change may increase both the frequency of wildfires and the amount of area burned. Studies of past climate changes and their effects on wildfires can provide constraints on potential future wildfire risks. Here, we reconstruct the history of wildfire across a representative subalpine forest landscape in northern Colorado over the past two millennia. Warming of [~]0.5 {degrees}C [~]1,000 years ago increased the percentage of our study sites burned per century by [~]260% relative to the past [~]400 y. The large increase in the number of sites burned by fires highlights the risk that large portions of individual landscapes may burn as climates continue to warm today. Many of the largest wildfires in US history burned in recent decades, and climate change explains much of the increase in area burned. The frequency of extreme wildfire weather will increase with continued warming, but many uncertainties still exist about future fire regimes, including how the risk of large fires will persist as vegetation changes. Past fire-climate relationships provide an opportunity to constrain the related uncertainties, and reveal widespread burning across large regions of western North America during past warm intervals. Whether such episodes also burned large portions of individual landscapes has been difficult to determine, however, because uncertainties with the ages of past fires and limited spatial resolution often prohibit specific estimates of past area burned. Accounting for these challenges in a subalpine landscape in Colorado, we estimated century-scale fire synchroneity across 12 lake-sediment charcoal records spanning the past 2,000 y. The percentage of sites burned only deviated from the historic range of variability during the Medieval Climate Anomaly (MCA) between 1,200 and 850 y B.P., when temperatures were similar to recent decades. Between 1,130 and 1,030 y B.P., 83% (median estimate) of our sites burned when temperatures increased [~]0.5 {degrees}C relative to the preceding centuries. Lake-based fire rotation during the MCA decreased to an estimated 120 y, representing a 260% higher rate of burning than during the period of dendroecological sampling (360 to -60 y B.P.). Increased burning, however, did not persist throughout the MCA. Burning declined abruptly before temperatures cooled, indicating possible fuel limitations to continued burning.
