4. Pollen Evidence for Human-Induced Landscape Change Reveals the History of Agricultural Development in Southeastern China

The development of anthropogenic landscapes, as documented by palynological records, is significant for understanding the history of agricultural development in southeastern China. Pollen cores collected from delta to mountain sites reveal three main phases in human-related ecosystem changes. Before 3000 BP, pollen assemblages show evidence of dense subtropical evergreen broadleaved forests (dominated by Quercus-evergreen and Castanopsis) with very few signs of human activities such as deforestation and agriculture. Rice cultivation was limited in South China during this time. Landscape changes after 3000 BP include the abrupt onset of deforestation, sharp increases in pioneer taxa such as Dicranopteris, Pinus and Artemisia and an overwhelming rise in the frequency of Poaceae caused in part by the spread of cultivated rice and the onset of large-scale agricultural development. The development of rice agriculture in southeastern China was influenced by changing sea level, as well as social and cultural factors. The rapid formation of deltaic plains, starting around 3000 BP, created extensive freshwater marshes suitable for paddy fields. However, agriculture was limited to lowland areas during that time. Pollen records from hinterland and mountainous areas in South China show evidence for the onset of profound anthropogenic influence on subtropical mountain forests around 1.0 cal ka BP. This environmental transformation coincides with the timing of large-scale immigrations of war refugees from the north during the Tang and Song Dynasties.