Deforestation and technical innovation have changed the natural fire regimes, topography and carbon reservoirs during the history of human evolution. Recognition of the timing, scope, and magnitude of wildfire events in large river basins such as the Changjiang (Yangtze River) is essential for understanding the impacts of climate forcing and human perturbation on Earth surface processes. Here, we present a multi-proxy study based on the pollen and black carbon (BC) abundance in sediments of Core CM97 taken from the Changjiang Delta, aiming to reconstruct the paleo-fire history in the Changjiang River Basin and further disentangle anthropogenic and climatic influences on fire regimes during the Holocene. Our results show that the average BC abundance increased from 0.88 ‰ at 12–8 cal kyr BP to 1.17 ‰ at 8–5 cal kyr BP, well corresponding to the evolution of the Asian Summer Monsoon (ASM). This suggests the wildfire occurrences were dominated by hydroclimatic conditions during 12–5 cal kyr BP. After the early Bronze Age (∼5 cal kyr BP), the sustained high anomaly of BC abundance (average 1.30 ‰), however, was decoupled from the weakened monsoon climate. We propose that this might be associated with anthropogenic destruction of natural forests through fire-assisted agriculture and bronze smelting. Especially, with the prosperity of the Han Dynasty (202 BCE − 220 CE), a rapid increase in population promoted the transition of ecosystem (vegetation type) from forests to permanent farmlands in the drainage basin. Human intervention has overwhelmed the long-term climate control over wildfire, plant diversity, soil erosion, and sediment source-to-sink processes, suggesting the dominance of anthropogenic activities on nature over the last 2 kyrs. Our study provides deep insight on the enhancing perturbation of human activities on Earth's surface at a continental scale and provides more constraints on the Anthropocene epoch.

中文翻译：

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人类活动增强导致长江流域全新世野火格局变化

在人类进化史上，森林砍伐和技术创新改变了自然火灾状况、地形和碳库。认识长江等大河流域野火事件的时间、范围和强度对于了解气候强迫和人类扰动对地球表面过程的影响至关重要。在这里，我们提出了一项基于长江三角洲核心CM97沉积物中花粉和黑碳（BC）丰度的多代理研究，旨在重建长江流域的古火灾历史，并进一步理清人为和气候的关系。全新世期间对火灾状况的影响。我们的结果表明，BC的平均丰度从12-8cal kyr BP时的0.88‰增加到8-5cal kyr BP时的1.17‰，与亚洲夏季风（ASM）的演变非常对应。这表明 12-5 cal kyr BP 期间野火的发生主要受水文气候条件的影响。然而，在青铜时代早期（∼5 cal kyr BP）之后，BC丰度持续偏高（平均1.30‰）与季风气候减弱脱钩。我们认为，这可能与火助农业和青铜冶炼对天然森林的人为破坏有关。特别是，随着汉代（公元前202年-公元220年）的繁荣，人口的快速增长促进了流域生态系统（植被类型）从森林向永久性农田的转变。人类干预已经压倒了对野火、植物多样性、土壤侵蚀和沉积物从源到汇过程的长期气候控制，这表明过去 2 年内人类活动对自然的主导作用。我们的研究提供了关于大陆尺度上地球表面人类活动扰动增强的深刻见解，并为人类世时代提供了更多限制。