NANJING -- A new study has revealed vegetation changes in South China over the past 20,000 years, which can help scientists better understand the impact of climate change and human activities on vegetation.

The study, led by researchers from Nanjing Institute of Geology and Palaeontology under the Chinese Academy of Sciences, found that climate has gradually warmed up in south China since the "Last Glacial Maximum," 20,000 years ago.

Climate change was the main factor affecting vegetation distribution, while the impact of human activity became more remarkable in the later period, according to the study.

Researchers spent five years conducting a pollen study. They drilled core samples in 20 sites in regions to the south of the Yangtze River and selected data from 14 of the locations.

They detailed vegetation zoning maps around 18,000 years ago, 9,000 years ago and 6,000 years ago respectively, and described the distribution characteristics of plants in each zone/subzone.

The study noted south China was colder around 18,000 years ago, but the climate became warmer 9,000 years ago. Human farming activity had little influence on vegetation and the environment about 6,000 years ago, but the impact became more obvious 4,000 years ago as traces of forests burned by fire increased and large areas of broad-leaved forests disappeared.

The vegetation in the study area was also affected by the evolution and development of a monsoon climate, according to Chen Wei, a researcher from the institute.

"The study shows how the climate change and human activities affected vegetation, which can provide valuable references for the current studies on environment," said Wang Weiming, who led the research. "In the future, we will reveal environmental changes of ancient time in a more comprehensive and systematic way."

The findings were recently published in the journal Science China: Earth Sciences.