Middle-late Holocene environment change induced by climate and human based on multi-proxy records from the middle and lower reaches of Yangtze River, eastern China

Our knowledge about the interaction between human activities and the environment in the middle-late Holocene remains incomplete. Core C1 in Lake Chaohu from the middle and lower reaches of Yangtze River (MLYR), eastern China, provides an opportunity to investigate vegetation and climate changes, human activities, and East Asian summer monsoon (EASM) evolution since 5100 cal. yr BP. These variables are assessed based on radiocarbon dating, pollen and charcoal records, and magnetic susceptibility (& chi;(lf)), median grain size and TP. Results reveal a hiatus in sedimentation between 2080 and 730 cal. yr BP in the western part of Lake Chaohu, which is common in most lakes in the MLYR. Evergreen and deciduous broadleaved mixed forest retreated gradually after 3650 cal. yr BP, and was replaced by secondary Pinus forest after at least 730 cal. yr BP. Intense agricultural activities and vegetation clearance are first detected at 2520 cal. yr BP. Human settlements expanded from the lake front wetlands (during the period 2520-2080 cal. yr BP) to remote high-altitude areas (2080-100 cal. yr BP), and then returned to the lake front to reclaim the wetlands and lake (after 400 cal. yr BP). A gradual trend of recessional EASM strength from 4300 cal. yr BP and centennial-scale variations of EASM during the period 5100-3650 cal. yr BP are revealed. The reduction of summer insolation, southward shift of the ITCZ, and El Nino Southern Oscillation may control the intensity of EASM and climate on a large regional scale.