Abundance and δ13C of sedimentary black carbon indicate rising wildfire and C4 plants in Northeast China during the early Holocene

Abstract

Abstract Global warming and human activity are thought to be the primary drivers of the globally rising occurrences of forest fires. Due to the importance of local to regional environmental drivers in mediating fire frequencies, reconstructing fire histories of representative geographic regions is important to understand fire regimes and predict future changes. The present study aims to establish a relatively high-resolution fire record of boreal forests in northeastern (NE) China and identify the primary environmental drivers. We analyzed the concentration and stable carbon isotopic composition of black carbon (BC and δ13CBC) of a 34,000\xa0cal\xa0yr BP sedimentary sequence from a crater lake (Tianchi). The results show that fire events and C4 plants were scarce during the late Last Glacial but increased since the deglaciation. Both fire and the abundance of combusted C4 plants reached their maxima during the early Holocene, which may be attributed to rising temperatures due to intensified solar radiation and summer monsoons. During mid-to-late Holocene, fire events remained relatively stable and were primary associated with C3 plants burning. Fire was particularly infrequent and C3 trees were abundant during the periods of 5500–3100\xa0cal\xa0yr BP and 1500–150\xa0cal\xa0yr BP, which can be attributed to a wet climate. Fires exhibited evident increases from 150\xa0cal\xa0yr BP to the present, suggesting a substantial role of human activities. Both BC and δ13CBC during the Holocene show a significant correlation with pollen-based temperatures but not with precipitation, suggesting that temperature rises played a primary role in stimulating forest fires via mediating effective moisture. Collectively, these findings suggest that forest fires and C4 plants would likely increase in NE China in response to global warming and increasingly intensive anthropogenic disturbance, highlighting the importance of establishing a long-term understanding of fire regimes to create more sustainable, science-based fire management strategies.