Holocene vegetation and climate history at Haligu on the Jade Dragon Snow Mountain, Yunnan, SW China

Abstract

This paper uses pollen analysis to investigate and document the changing climate and vegetation during the Holocene based on a 400 cm core in depth obtained at a wetland site at Haligu (3,277 m a. s. l.) on the Jade Dragon Snow Mountain in Yunnan, China. By applying the Coexistence Approach to pollen data from this core, a quantitative reconstruction of climate over the last 9,300 years was made based on each pollen zone and individual core sample, which reveals the temperature and precipitation change frequently during that time. The qualitative analyses show that from 9300 to 8700 cal. yr BP, the vegetation was dominated by needle-leaved forest (mainly Pinus and Abies), indicating a slightly cool and moderately humid climate. Between 8700 and 7000 cal. yr BP, evergreen broad-leaved forest, dominated by Quercus, became the predominant vegetation type, replacing needle-leaved forest at this elevation, implying a warmer and more humid climate. During the period 7000 to 4000 cal. yr BP, the vegetation changed to mixed needle-leaved and evergreen broad-leaved forest, indicating a warm and moderately humid climate, but somewhat cooler than the preceding stage. From 4000 to 2400 cal. yr BP, the vegetation was again dominated by evergreen broad-leaved forest, but coniferous trees (mainly Pinus) began to increase, especially relative to a decline in Quercus. This implies that the climate remained warm and humid but slight drier than previously. The evergreen Quercus phase (8700–2400 yr BP) was designated as the Holocene climatic optimum in the Haligu core sediments. It is correlated with a markedly greater abundance and diversity of pteridophytes spores than was recorded before or after this period. From 2400 cal. yr BP to present, the vegetation was dominated by needle-leaved forest, of which Pinus formed the predominant component, accompanied by Abies and Tsuga. This reflects a slightly cooler, humid climate but also correlates with a period of increasing human settlement on the lower slopes of the mountain. At this elevated site, several hundred metres above the highest present day settlements, direct palynological evidence of anthropogenic activity is uncertain but we discuss ways in which the marked decline in Quercus pollen during this period may reflect the impact of ways in which natural resources of the mountain have been utilised.