SPATIOTEMPORAL CHANGE OF SPRING PHENOLOGY UNDER URBANIZATION

Urbanization is one of the major environmental challenges facing today for its ecological influence such as vegetation phenology. Urban phenology change, the study of recurring events in the plants life in urban areas, is of great importance for understanding the interaction between urban ecosystems and the changing environment. Urban phenology also has important implications for human health, such as prolonging the pollen season and increasing symptoms of pollen-related allergic diseases. Using Landsat observations of the last three decades (1984-2015), this research examined the spatiotemporal pattern of spring phenology along urban-rural gradients in major large cities in the U.S.. The start of growing season (SOS), an indicator of spring phenology, was derived from enhanced vegetation index by a self-adjusting double logistic model. The results show an advancement of SOS from rural to urban areas, with a maximum around 45 days. While a tendency of earlier SOS for the last three decades is observed in both rural and urban areas, the degree of phenology advancement shows large regional variations. This study suggests that the change in spring phenology in urban areas may have a complex interaction with the surrounding environment and human activities. An improved understanding for mechanisms of environmental factors on urban phenology is highly needed in future studies.