How did vegetation relate to surface temperatures in the Guangzhou–Foshan metropolis?

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Many studies have observed that vegetated local climate zone (LCZ) types play an important role in reducing the surface urban heat island effect. But research examining metropolitan land surface temperature (LST) patterns using an urban–rural LCZ scheme, alongside the cooling effects of different vegetation types, has been lacking. This study focused on the Guangzhou–Foshan metropolis to investigate spatial variations in LST in subtropical cities and vegetation’s role in regulating LST changes.

The researchers used normalized difference vegetation index (NDVI) and LST data from space-borne MODIS products for 2000, 2009, and 2019, along with LCZ maps, urban–rural gradient data, and land use and land cover (LULC) maps. They compared urban and rural areas, seasons, daytime, nighttime, and day–night patterns using logarithmic regression, Pearson partial correlation, and comparison analysis.

LST was generally higher in built LCZ types than in land cover LCZ types and was positively correlated with building density and height. LST decreased logarithmically along the urban–rural gradients: it fell rapidly at first in the urban area near the start of the gradient, then leveled off farther along in suburban and rural areas. In vegetated LCZ types, NDVI was significantly negatively correlated with LST during the daytime but positively correlated with it at night. Vegetated LCZ types showed a clear cooling effect, with an average cooling amplitude of 1.92 °C across the three investigated years.

The authors concluded that urban LST changes were closely associated with LCZ types, urban–rural gradients, NDVI values, and vegetation types. Vegetation’s cooling ability varied seasonally and between day and night, with particular emphasis on the cooling effect of dense evergreen broadleaf forests. The authors suggest that comprehensively assessing vegetation’s impact on urban surface temperatures can inform urban ecological construction and management.