Impacts Of Aerosol Direct Radiative Forcing On Terrestrial Ecosystem Respiration In China From 2001 To 2014

Aerosol direct radiative forcing (ADRF) has complex effects on vegetation and ecosystems by altering environmental conditions. Based on the Fu-Liou radiation transfer model and Community Land Model (CLM4.5), this study simulated the ecosystem processes under scenarios with and without ADRF in China from 2001 to 2014, analysed the respiration changes in different ecosystems, and evaluated the relationship between the ADRFinduced changes in soil hydrothermal conditions and respiration changes in the vegetation growing season (Jun-Jul-Aug). During the study period, ADRF changed the total ecosystem respiration (ER) in the farm, forest and grass ecosystems by 25.14, -6.84 and 5.03 g C m- 2 yr-1, respectively, and this difference was related to the canopy structure and aerosol loadings in the three ecosystems. Moreover, ADRF had the greatest impact on ecosystem respiration in summer. In addition, ADRF had significant promoting effects on autotrophic respiration (AR) and significant inhibitory effects on heterotrophic respiration (HR) by reducing the soil temperature at 10 cm below the surface (TS). ADRF-induced changes in soil hydrothermal conditions further affected the nitrogen content in plants, especially N in fine roots and leaves. N is closely related to proteins associated with respiration; thus, changes in N had a nonnegligible impact on respiration. The increased soil volume water content (HS) alleviated the drought stress in the north of China, which may be the reason for the increased HR there. In addition, changes in CO2 fixation and CH4 and N2O emissions were also observed, and the results showed that ADRF had a greater influence on carbonaceous greenhouse gases (GHGs). In China, ADRF aggravated the greenhouse effects in the farm, forest and grass ecosystems, of which the GWPs were 1.22*1010, 7.27*1010 and 2.42*1010 kg CO2 equivalent yr-1, respectively. Our study highlights the serious effects of aerosol-induced radiation perturbations on biogeochemical processes, especially respiration, in terrestrial ecosystems, which ultimately have feedback effects on the climate.