Cycles of grazing and agricultural activity during the historical period and its relationship with climatic and societal changes in northern China

Abstract

AbstractThe arable‐pastoral ecotone in northern China is ecologically fragile and the region has experienced substantial climatic variability, triggering population migrations, and the alternation of subsistence strategies during the historical period. However, the lack of continuous proxy records of arable and grazing activity has hampered our understanding of shifts in subsistence strategies and their relationship with climatic and societal changes. We obtained records of Sporormiella‐type spores and crop pollen from Gonghai Lake in northern China to reconstruct changes in cultivation and grazing intensity over the past approximately 2000 years. The results show that intensive grazing and cultivation occurred during the Sui and early‐middle Tang Dynasties (581–820 CE), when there was a relatively favourable climate, harmonious ethnic relations, and strong central government control. Conversely, weakened agricultural activity in the late Tang Dynasty (820–907 CE) corresponded to a deteriorating climate and frequent wars. High temperatures during the northern Song Dynasty (960–1127 CE) promoted the expansion of arable land in mountainous areas, whereas a cold climate and societal crises during the Era of Disunity (220–580 CE) and the Ming‐Qing Dynasties (1368–1912 CE) limited the expansion of cultivated land and there was a shift to grazing as a subsistence activity. Time‐series analysis reveals that the arable farming phases had a longer periodicity than the grazing phases, possibly because of the greater resilience of the former to climate change and the attachment of agriculturalists to their land. Our findings potentially help improve our understanding of the impact of land use on soil degradation.