Vegetation response in subtropical southwest China to rapid climate change during the Younger Dryas

Investigations of past biotic responses to rapid climate shifts are useful for developing biological scenarios that may result from future climate change. In this context, the Younger Dryas (YD) cold climatic reversal (~12,800–11,500 cal yr BP), and the resulting vegetation response, is of considerable interest. In this study, we conducted pollen and grain-size analyses of a section spanning the interval of 17,600–8500 cal yr BP in a sediment core from Xingyun Lake, in Yunnan Province, southwest China. At the same time, the other 44 paleovegetation sites from Yunnan Plateau and elsewhere in China were reviewed. Our aims were to investigate the vegetation responses to climate changes during the YD and to integrate them with climate simulation results. During the YD climatic reversal, mean annual temperatures in Yunnan were ~1.5–2.4 °C colder than today. The vegetation response to the cooling during the YD was characterized by downward shifts in the elevation of vegetation zones. Notably, only a relatively small proportion of taxa, i.e., Abies, Picea, Pinus, Quercus (E), Quercus and Poaceae, were climatically sensitive during the YD, and changes in spring temperature were a major factor on the vegetation dynamics. In addition, there was a time lag in the vegetation response to the YD event in the Yunnan Plateau. Consistent with other records from China, the YD climatic reversal only caused a change in vegetation composition rather than vegetation type succession. Notably, there was a latitudinal gradient in the magnitude of the YD cold event in China and in the resulting vegetation response. Changes in both temperature and precipitation were responsible for the vegetation changes at mid-to-high-latitudes, whereas the vegetation dynamics at low latitudes were determined largely by changes in spring temperature.