Stage response of vegetation dynamics to urbanization in megacities: A case study of Changsha City, China.

Urban vegetation affects urban microclimate and maintains biodiversity, which is vital to the social-ecological system. However, there is a lack of research on quantitatively identifying urbanization stage impact on vegetation dynamics, and the stage difference in the response of vegetation dynamics to urbanization characteristics is not clear. In this study, taking Changsha City as an example, we explored the response of vegetation dynamics to urbanization, and identified the impact stages of urbanization on vegetation dynamics as well as their social-ecological characteristics. The results showed that the vegetation dynamics in Changsha City presented spatial pattern of "increase-decrease-increase" from downtown to outside in the past 20 years. The population density, GDP density and construction land proportion firstly inhibited vegetation growth, and then promoted it, with the turning points of 141.58 million yuan/km, 1205 person/km, and 19.80 %, respectively. Then, the urbanization impact on vegetation dynamics was quantitatively divided into three stages according to the vegetation change speed, and in different stages, urbanization impacts on vegetation dynamics were compared. This study illustrated the typical stage feature of the urbanization impact on vegetation dynamics.