Pollen analysis and paleoecology from the Bortala River National Wetland Park, located in the Wenquan County, Xinjiang Province, Northwest China@en

Grasslands cover 41.7% of China's land surface and distribute mainly in NW China. To project future change of grassland fires, it is essential to explore paleofire dynamics. However, comparatively little is known about the patterns and driving forces of grassland fires in NW China due to the scarcity of paleorecords. Here, we present Holocene sedimentary records of grassland fire and vegetation in westerly-dominated Xinjiang (NW China) to examine fire-fuel-climate interactions. We find that grassland fire-regime is fuel-limited, consistent with other grasslands worldwide. We reveal that burning increased throughout the Holocene, due to increasing moisture, grass cover, fuel load and temperature of spring fire season. The Holocene pattern of burning coincides with several other records nearby and a global-scale grassland fire record. Our results are different from monsoonal China where fuel load is not a constraining factor and more (less) fires occurred during colder/drier (warmer/moister) periods in the Holocene.草原覆盖中国陆地总面积的41.7%，且主要分布于中国西北地区（NW China）。若要精准预测草原火灾的未来演变趋势，探究古火灾动态实为必要前提。然而，受限于古火灾记录的稀缺性，学界对中国西北地区草原火灾的发生模式与驱动机制的认知仍较为薄弱。本研究基于受西风带主导的中国西北新疆地区的全新世（Holocene）沉积物记录，探讨火灾-燃料-气候三者间的相互作用机制。研究结果表明，该区域的草原火灾制度（fire-regime）受燃料供给限制，这一结论与全球其他草原生态系统的火灾特征相符。研究还发现，全新世时期火灾发生频次整体呈上升态势，其驱动机制包括春季火险季的湿度提升、草原盖度增加、燃料载荷（fuel load）增大以及气温升高。全新世时期的火灾演变模式，与周边区域的多项古火灾记录以及全球尺度的草原火灾记录均具有一致性。本研究结果与中国季风区的火灾特征存在显著差异：季风区的草原火灾不受燃料载荷限制，且在全新世的寒冷/干旱时期火灾发生频次更高（温暖/湿润时期则更低）。