Enhanced warming due to afforestation and deforestation driven by both radiative and non-radiative effects in the mid-latitude Greater and Lesser Khingan mountains ecoregion of China

Temperate forests are vital for maintaining ecological security and regulating the global climate. Despite considerable controversy surrounding the biophysical impacts of temperate forests on mid-latitude temperatures, we analyzed the effects of forest cover change on local temperature using the Weather Research and Forecasting (WRF) model from 2010 to 2020 in the Greater and Lesser Khingan Mountains (GLKM), Northeastern China, and explored the related driving factors. The conversions between forest and open lands (i.e., cropland and grassland) were predominant. During the growing season, the conversion of cropland and grassland to forest resulted in warming (0.38 ​± ​0.10 and 0.41 ​± ​0.09 ​℃, respectively) in air temperature (Ta), while the reverse conversion caused cooling (−0.31 ​± ​0.08 and −0.24 ​± ​0.07 ​℃, respectively), which was less than the changes observed in land surface temperature (LST). Conversion of forest to impervious land caused warming (1.16 ​± ​0.11 ​℃), and the opposite conversion resulted in cooling (−0.88 ​± ​0.17 ​℃). These results indicate that radiative effects like albedo and net radiation drive the significant net warming effect from afforestation on open lands within the temperate forest ecoregion. Conversely, conversion to impervious land produced the most substantial net warming impacts, driven by non-radiative effects like sensible heat, latent heat, and ground heat flux (GH). In these conversions, temperature can indirectly influence precipitation (Pre) through vapor pressure deficit (VPD), and Pre can also indirectly affect temperature via evapotranspiration (ET). This study highlights the need to thoroughly understand the impacts of afforestation in temperate forests while avoiding deforestation to regulate the climate effectively.