Spatiotemporal Pattern of Urban-rural Aradient Land Cover Changes and Their Impact on Urban Heat Island in Xi′an City Since the 21st Century

Rapid urban expansion had a significant impact in land use/cover change along urban-rural gradient, and the increase of impervious construction land and the reduction of vegetation cover had induced and aggravated the urban heat island effect. Studying the impact of urban-rural gradient land cover change on urban heat island effect was significant for urban planning and construction, improving the comfort of human settlements and enhancing the function of urban ecological services. The surface temperature of Xi'an city was retrieved by mono-window algorithm based on Landsat images, and the thermal field intensity map was obtained by calculating the thermal field variation index, and the gradient land cover changes in urban and rural areas were analyzed with land use data. The results showed that: ①The urban heat island effect in Xi'an showed a trend of first increasing and then decreasing from 2000 to 2015. In 2000, the extremely strong heat island effect area accounted for 10.58% of the research area, and gradually increased to 16.14% in 2011, and then decreased to 9.00% in 2015. ②From 2000 to 2015, the area of construction land increased 412.76 km² and the intensity of extremely strong heat island expanded year by year with the expansion of urban built-up areas. ③About 70% of the non-heat island effect areas were located on farmland and forest land, and the proportion of water area in the non-heat island effect was increasing year by year from 31% to 47%, which showed that the increase of vegetation and water area could effectively alleviate the urban heat island effect.