History of human disturbance to vegetation in the Southeast Hills of China over the last 2900 years: Evidence from a high resolution pollen record

Abstract

The lower reaches of the Yangtze River have a long history of human occupation and rice cultivation, but our understanding of human activities in the mountainous region south of the lower Yangtze is still limited. In this study, we present a high-resolution vegetation record spanning the past 2900 years from the Southeast Hills of China by analyzing loss-on-ignition, pollen, charcoal, and non-pollen-palynomorphs from a lake sediment core. Combining our data with historical records, results suggest the study region was covered by dense broadleaved forests dominated by evergreen Cyclobalanopsis/Quercus from the start of the pollen record at 890 BCE until 850 CE. During this early period, colonization of the mountainous region was limited by rugged relief, closed forests, and lack of suitable land for farming. Later between 850 CE and 1180 CE, a slight decrease of evergreen trees, small rises in cereals and the ruderal herb Artemisia, and more frequent fire events point to the development of small-scale agricultural practices related to increased population. This change may reflect the shift of the economic center of China towards the lower Yangtze reaches, which happened during the Tang Dynasty (618–907 CE) and the influx of war refugees from the north especially during the Song Dynasty (960–1279 CE). From 1180 CE, a sharp decline of evergreen broadleaved trees and a peak in fire frequency was closely linked to a wave of deforestation resulting from the abrupt expansion of cereal cultivation. These changes were accompanied by the remarkable spread of pioneer secondary plants such as Pinus, Artemisia, and Dicranopteris-type ferns, which are typical indicators of human-induced deforestation in the region. It is probable that the population boom spread to the mountains and intensive agricultural activities took place involving terraced fields. Additionally, the coeval mining, smelting, and porcelain production in the mountains enlarged the scale of deforestation. Our study provides valuable information for landscape management and biodiversity conservation in the mountainous hinterland of subtropical southeast China.