Regional land cover changes of the last 6,500 years in middle and southern subtropical China

Abstract

Our knowledge about the Holocene vegetation changes in southern China has been based on the inference from pollen percentages. However, the relationship between pollen percentages and vegetation is non-linear. This may lead to significant bias in real vegetation cover and limit our understanding of land cover changes and its relation to climate and human activities. Here we quantitatively reconstruct past regional land-cover changes by applying the REVEALS model to four pollen records collected from two study areas in southern and middle subtropical zones. The two study areas, representing the Pearl River Basin (PRB) and Wuyi Mountain (WYM), are located in spatial gradients, thus help to elucidate not only the climate forcing, but also the spatio-temporal spread of agriculture in this region. The REVEALS reconstruction shows a clear difference from original pollen percentages and is considered more realistic in depicting regional vegetation changes. Based on more reasonable reconstruction result by excluding wetland-associated taxa, i.e., Cyperaceae and Alnus, we found a gradual decline of forest covers since the middle Holocene which may be related to the reduced rainfall in response to the weakening East Asian Summer Monsoon. The human impact on the forest cover was identified by an abrupt increase of Poaceae cover at 3500–2700 cal yr B.P. in the PRB area, which appeared later in the WYM mountainous area. Thus, our study reveals a progressive expansion of anthropogenic activities from the coastal lowlands to mountainous areas.