Late-Holocene fire regimes under climate and vegetation change in the Sanjiang plain, northeastern China

School of Geographic and Environmental Sciences, Tianjin Normal University, Tianjin 300387, China

^* rayyin206@gmail.com

Abstract

Understanding historical fire regimes and their driving mechanisms provides valuable insights for future hazard prediction. Here, we reconstructed the fire and vegetation histories of the Sanjiang Plain over the last 5000 years based on microscopic (<125) charcoal content and morphology of sedimentary coring in the coastal marshes of the middle reaches of the Ussuri River, respectively. The results of the study indicate that four high fire frequency phases were identified in the last 5000 years, at 4.3-4.0 ka BP, 2.8-2. ka BP, 1.4-1.2 ka BP, and 0.5 ka BP to date. These intervals coincide with the weakening phase of the East Asian summer monsoon (EASM) during the late Holocene and are generally consistent with the decreasing trend of precipitation in the region. Thus, we suggest that the EASM circulation, and especially its accompanying precipitation, played a key role in the evolution of fire regimes in the Sanjiang Plain during the Late Holocene. In addition to climate change, regional vegetation conditions are also significant factors driving fire occurrence. In contrast, the gradual increase in fire frequency over the last 500 years has been caused mainly by human activities rather than climate and vegetation.