Mid-Holocene Climate Change vs. Anthropogenic Influence in the Evolution of Southeast China Forest Landscapes

Abstract:

The lower Yangtze region is situated on a biogeographical boundary between temperate broadleaf and sub-tropical evergreen forests, so that natural vegetation was sensitive to climatic fluctuations during the mid-late Holocene transition. Vegetation studies focused on the Yangtze Delta area reconstruct a gradual transition from sub-tropical to temperate forests beginning ca. 5500 cal BP, followed by a more abrupt shift toward cold-tolerant trees at around 4200 cal BP. Both transitions are attributed to climate change, with minimal anthropogenic influence. Here, we examine comparable high-resolution evidence for vegetation change from south of the biogeographical boundary, in subtropical evergreen forest zones of Fujian. Our data suggest climatic fluctuations, including a mid- Holocene cooling period and a climate reversal after ca. 5500 cal BP, broadly parallel to ones observed for the Yangtze Delta area. Thus, it appears the climatic transitions reconstructed from vegetation data represent regional manifestations of an evolving Asian Monsoon system that widely influenced southeast China, not only the lower Yangtze region. The development of sedentary Neolithic cultures, the emergence of early villages, and rapid population growth all occurred during the period of mid-Holocene climatic fluctuations. However, our results support the hypothesis that human impact on the regional vegetation was minimal during this era, and that anthropogenic influence did not become pronounced until around 2000 cal BP.