Climate and Fire History of the past approximately 10000 years in central Labrador based on sediments from Canoe and 'Big Beer' Lakes

Fire plays a critical ecological role in the boreal forest. The long-term history of fire and link(s) to climate change remain understudied in the eastern boreal forest of present-day Labrador. Here we provide a new data set based on short sediment cores extracted from two lakes (Canoe and “Big Beer”) in eastern Labrador in 2013. Age-depth models were constructed for each core based on corrected Accelerator Mass Spectrometry (AMS) Carbon 14 dates. Charcoal (area and counts) was used to reconstruct fire histories, and changes in climate were inferred from analysis of sediment loss-on-ignition, magnetics (susceptibility, isothermal remanent magnetization and anhysteretic remanent magnetization), stable isotopes (carbon and nitrogen) and biogenic silica. Charcoal data suggested markedly different fire histories for the two lakes. Fire appears to be largely absent in the area around Big Beer Lake except for two possible fire events prior to ~6900 Before Present (BP). Fire was more common at Canoe Lake as indicated by higher concentrations of charcoal overall and multiple distinct peaks, especially after 4000 BP.

火在北方泰加林（boreal forest）的生态系统中发挥着关键的生态作用。现今拉布拉多东部的北方泰加林内，火的长期演化历史及其与气候变化的关联仍未得到充分研究。本研究依托2013年在拉布拉多东部两个湖泊——独木舟湖（Canoe Lake）与"大比尔湖（Big Beer Lake）"——采集的短沉积岩芯，构建了一套全新数据集。我们基于校正后的加速器质谱（Accelerator Mass Spectrometry, AMS）碳十四测年数据，为每一根岩芯建立了年代-深度模型。以炭屑的面积与颗粒数作为代用指标重建火演化历史，并通过沉积物烧失量、磁学指标（磁化率、等温剩余磁化强度与非磁滞剩余磁化强度）、稳定同位素（碳与氮）以及生物硅的分析结果反演气候变化过程。炭屑数据显示，两个湖泊流域的火演化历史存在显著差异。大比尔湖周边区域几乎无火烧记录，仅在约6900年前（Before Present, BP）存在两次疑似火烧事件。独木舟湖的火烧事件则更为频繁：整体炭屑浓度更高，且存在多个清晰的炭屑峰值，尤其在距今4000年之后更为显著。