Quantitative reconstruction of the vegetation of the Qinhuangdao area, western coast of Bohai Sea, North China, during the Little Ice Age

Abstract

It is widely recognized that the climate of the Little Ice Age (LIA) was generally cold. However, there are differences in the climate response of the vegetation in different regions during the LIA, and high-resolution quantitative research is lacking. Here, we present a high-resolution pollen analysis and the Landscape Reconstruction Algorithm (LRA) based on relative pollen productivity, combined with AMS 14C dating, to quantitatively reconstruct the vegetation response to climate and sea level change on the western coast of Bohai Sea. The main findings are as follows: (1) The coverage of the main plant taxa reconstructed using estimates of relative pollen productivity was closer to the actual vegetation conditions than that based on pollen percentages. (2) Since ∼1250 A.D., the study area was occupied by temperate deciduous broadleaved forest, dominated by Quercus, with a smaller proportion of Pinus forest. The regional vegetation types did not change significantly, but the forest cover decreased gradually from ∼60% in the Middle Warm Period (MWP, 1250–1310 A.D.) to ∼40% in the LIA (1310–1610 A.D.), due to the combined influences of climate and human activities. (3) The composition of herbaceous plants changed substantially during the LIA. In the early LIA (1310–1450 A.D.), the climate became cold and dry and the sea level began to fall, resulting in a substantial increase in the proportion of Poaceae (∼10%). In the middle of the LIA (1450–1610 A.D.), the climate became colder and drier, the sea level fell further, and the lagoon shrank. In response, there was an increase in drought and salt-tolerant Chenopodiaceae (∼10%) and Artemisia (∼5%), a substantial increase in Selaginella sinensis supplied by fluvial processes.