Last deglacial and Holocene vegetation evolution and climate variability in the subalpine western Nanling Mountains in South China

Abstract

Pollen analysis of a 236-cm-long core at Daping Swamp, a subalpine swamp in the western Nanling Mountains, provided a history of vegetation evolution that was related to climate changes in the last 15,400 years. Generally, pollen data revealed a subtropical climate in the past 15,400 years. In the last deglacial period (15,400–10,900 cal yr BP), the study region was characterized by evergreen and deciduous broadleaved forests. A marked warm and wet period from 15,400 to 13,200 cal yr BP, which was characterized by high frequencies of arboreal pollen, corresponded to the Bølling–Allerød event. Significant shrinkage of evergreen–deciduous broadleaved forests and expansion of grassland from 13,200 to 10,900 cal yr BP suggested evidently cool and dry conditions that were the reflection of the Younger Dryas event. In the early Holocene (10,900–8200 cal yr BP), the glacier boundary effect might cause less warm and humid conditions relative to the middle Holocene. From 8200 to 4600 cal yr BP, pollen data reflected a marked expansion of evergreen and deciduous broadleaved forests and shrinkage of grassland, suggesting the thermal maximum that could be considered as the Holocene Optimum. From 4600 to 1500 cal yr BP, grassland exhibited expansion. Between 1500 and 600 cal yr BP, the evergreen and deciduous broadleaved forests expanded, whereas the grassland shrunk, implying a short wetter and warmer interval. After 600 cal yr BP, the grassland displayed expansion again. Broad regional correlation reflected that multiple factors including the summer monsoon, variation of sea level, ocean sea surface temperature (SST), and solar insolation may have played a role in climate changes that influenced vegetation evolution in the study area. Our results also reflected that in South China, the subalpine regions exhibited a different climate variation from that of regions with low latitude and elevation.