黄河下游东平湖炭屑记录的近1 500年以来火演化历史

Fire history over the past 1 500 years revealed by charcoal record from the Dongping Lake in the Lower Yellow River

  • 摘要: 东平湖是黄河下游地区最大的蓄洪湖泊,其沉积物蕴藏着流域地质历史时期丰富的环境信息。本研究以东平湖沉积岩芯(DPK岩芯,161 cm)为研究对象,利用该岩芯的炭屑记录,并结合粒度、烧失量等古环境指标,重建了东平湖地区近1 500年以来的古火演化历史,探讨了火事件与气候变化、人类活动之间的关系。研究结果表明:(1)516—1254 AD,黄河下游东平湖地区为冷干转暖湿气候,火事件较频繁,但约1000 AD之后有降低趋势;(2)1254—1922 AD,气候寒冷,旱涝交替频繁,气候变化和人类活动共同影响下导致火事件较之前明显加频加剧;(3)1922—1962 AD,气候相对暖湿,受气候变化及黄河改道影响,火事件频率显著减少且趋于稳定;(4)1962年以来,在暖干气候条件及人类活动加剧扰动的背景下,火事件明显增加,尤其是>100 μm炭屑浓度急剧攀升至整个剖面的最高峰,粒度迅速粗化,表明人类活动干扰进一步加强。进一步分析认为,气候变化是促进该地区火活动的重要因素,而人类活动(如刀耕火种、毁林开荒、战争等)的加强可能是导致东平湖流域火事件频发的主因。研究结果对于未来全球变暖背景下区域森林火灾的防护与治理具有重要的科学意义,进而更好地服务于黄河流域生态保护与高质量发展国家战略。

     

    Abstract: Dongping Lake is the largest flood storage lake in the lower reaches of the Yellow River, and its sediment contains rich environmental information from the geological history of the basin. This study focuses on the sediment core (Core DPK, 161 cm) from Dongping Lake, in Dongping County, Shandong, China and utilizes the charcoal records from this core. Combined with grain size and loss on ignition (LOI), we reconstructed the paleo-fire evolution history in the Dongping Lake region over the past 1500 years to explore the relationship among fire events, climate change, and human activities. Results indicate that: (1) during 516—1254 AD, the Dongping Lake region experienced a transition from cold/dry to warm/humid climate. Fire incidents were frequent, but there was a decreasing trend after around 1000 AD; (2) during 1254—1922 AD, the climate was cold, with frequent alternations between droughts and floods. The combination of climate change and human activities led to a significant increase in the frequency and intensity of fire incidents; (3) during 1922—1962 AD, climate was relatively warm and humid. Due to climate change and the diversion of the Yellow River, the frequency of fire events significantly decreased and stabilized; (4) since 1962, under the background of a warm and dry climate and increased human activities, fire incidents have increased significantly. Particularly, the concentration of charcoal fragments (>100 μm) rose sharply to the highest peak in the entire profile, accompanied by rapid coarsening of grain size, indicating intensified human interference. Further analysis suggests that climate change is a significant factor promoting fire activity in the region, while intensified human activities (such as slash-and-burn agriculture, deforestation, wars and so on) may be the primary cause of frequent fire incidents in the Dongping Lake basin. The results have important scientific significance for the prevention and management of regional forest fires under the background of global warming, and shall contribute to better serving the national strategy of ecological conservation and high-quality development of the Yellow River basin.

     

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