Climate and Sea Level Controls on the Spatial Heterogeneity of Mid-Holocene Vegetation in the North China Plain

Understanding the response of regional vegetation succession to climate changes and human activities in the Middle Holocene can help predict the trajectory of future vegetation changes. The North China Plain, modulated by the East Asian monsoon, is sensitive to global climate changes. However, its vegetation type and distribution during the Middle Holocene are still unclear. Based on the comprehensive analysis of 155 samples for pollen and grain sizes as well as other environmental proxies from the LD03 drill core, vegetation was reconstructed quantitatively using the REVEALS model during the period of 8.4-5.5 cal ka BP. (1) Compared to the pollen percentage, the coverage of Pinus (13.5%) decreased most significantly, while the coverage of Quercus increased significantly (51.3%). The proportion of Ephedra (11.9%) increased. A large area of temperate deciduous broad-leaved forests mainly with deciduous Quercus developed in the eastern coastal plain of Hebei from 8.0 ka BP to 5.5 ka BP. (2) During 7.4-7.1 ka BP, the proportion of broadleaved trees decreased significantly, while herbaceous plants such as Chenopodiaceae and Poaceae increased. Vegetation components such as Quercus and Pinus and Chenopodiaceae and Poaceae were sensitive to marine transgression. (3) The vegetation distribution during the Middle Holocene in the eastern and western regions of Hebei was mainly as follows: There was a large area of Pinus in the Taihang Mountains in western Hebei, whereas grasslands mainly composed of Asteraceae and Poaceae (reeds) developed in the floodplain of central Hebei. Coniferous and broad-leaved mixed forests or temperate deciduous broad-leaved forests developed in the eastern coastal plain of Hebei. The possible mechanisms of vegetation heterogeneity are sea level rise and the enhanced monsoon precipitation.