Cooling effect of wetlands weakens and reverses to a warming effect with increasing latitude in the Amur River Basin

Abstract

Wetland changes can alter diurnal land surface temperature (LST) through biophysical processes and contribute to adapting to global warming. However, studies focusing on the impacts of land cover changes on LST have neglected the feedback of wetland canopy structural changes, such as leaf area index (LAI), on temperature. In this study, based on long-term remote sensing observations, the effects of wetland area and LAI changes on local diurnal LST in the Amur River Basin (ARB) from 2000 to 2020 were comprehensively analyzed at multiple spatial scales. The results indicated that increases in wetland area in the ARB exhibited a cooling effect during the daytime but a warming effect at night, contributing to the exacerbation of diurnal temperature asymmetry in mid- to high-latitude regions. The temperature effect of wetland changes showed latitude dependence: the daytime cooling effect caused by changes in wetland area and vegetation LAI significantly weakened with increasing latitude in summer. In addition, the cooling effect during both day and night caused by changes in wetland LAI reversed to a warming effect from 50°N to the northward. The cooling effect in summer and the warming effect in spring, autumn, and winter caused by changes in wetland vegetation LAI highlighted the importance of considering the seasonal climatic regulatory role of wetlands in mid- to high-latitude regions. These complex effects suggest that, in the sustainable protection and management of wetlands, the feedback of wetland changes on surface temperature at multiple scales should be fully considered.