Bo Cheng, Jennifer K Adams, JianHui Chen, Aifeng Zhou, Qing Zhang, Anson W. Mackay

During the latter stages of the Holocene, and prior to anthropogenic global warming, the Earth underwent a period of cooling called the neoglacial. The neoglacial was associated with declining summer insolation and changes to Earth surface albedo. Although impacts varied globally, in China the neoglacial was generally associated with cooler, more arid climate, which led to renewed permafrost formation, and shifts in vegetation composition. Few studies in central China, however, have explored the impact of neoglacial cooling on freshwater diversity, especially in remote alpine regions. Here we take a palaeolimnological approach to characterise multidecadal variability in diatom community composition, beta-diversity, and flux-inferred productivity over the past 3,500 years in the Qinling Mountains, biodiversity hotspot. We investigate the impact of long-term cooling on primary producers in an alpine lake, which are fundamental to overall aquatic ecosystem function. We show that trends in beta-diversity and shifts in ecological guilds likely reflect changing lake-catchment resource availability, linked to both long-term attenuation of the Asian summer monsoon, and abrupt cool events, linked to a strengthened Siberian High. Important diatom community and productivity responses to the Medieval Climatic Optimum and the Little Ice Age are all apparent in our record, although impact from previous centennial-scale, cool-events are less evident.