Abstract: We investigated the thermal environment characteristics of Beijing First Green Belt (BFGB) area, which is defined as the sub-districts intersected with the belt, and identified the cooling effect of greenery. Land surface temperature (LST) was retrieved and greenery land cover was interpreted by Landsat 8 image data in 2015, and thermal environment characteristics and cooling effect of greenery were analyzed by GIS spatial analysis, moving window landscape pattern indices, and statistical analysis methods. Heat island intensity in the study area showed a pattern of “south high and north low” and “east high and west low”. BFGB inner zone had higher proportion of strong heat island area than the outer zone, suggesting that governance in the belt was not sufficient to effectively regulate the thermal environment. At sub-district level, 55.74% of sub-districts had net contribution to strong heat island. Greenery ratio was negatively correlated with the proportion of heat island area and positively correlated with the proportion of cool island area, suggesting that high greenery ratio in sub-districts could effectively mitigate heat island. At grid sampling point level, sampling points with net contribution to strong heat island accounted for 51.69%. Buffer zone with a 500 m radius was generated by every sampling point. The regression model showed that the impact radius of greenery on mitigating heat island effect was between 150-200 m, and that 1% enhancement of greenery within 50-100 m and 100-150 m circles can result in 0.023 and 0.013 ℃ decrease of LST. From the greenery spatial pattern, the larger the patch area, the simpler the shape, the more aggregated the spatial distribution, the stronger the cooling effect is; while the higher the patch density, the more complex the shape, the more dispersed the spatial distribution, the weaker the cooling effect is.

Key words: simulated warming, DOC, DON, altitude gradient, alpine forest.