Abstract
Abstract. Aerosols can enhance ecosystem productivity by increasing diffuse radiation. Such diffuse fertilization effects (DFEs) vary among different aerosol compositions and sky conditions. Here, we apply a suite of chemical, radiation, and vegetation models in combination with ground- and satellite-based measurements to assess the impacts of natural and anthropogenic aerosol species on gross primary productivity (GPP) through DFE from 2001–2014. Globally, aerosols enhance GPP by 8.9 Pg C yr−1 under clear-sky conditions but only 0.95 Pg C yr−1 under all-sky conditions. Anthropogenic aerosols account for 41 % of the total GPP enhancement, though they contribute only 25 % to the increment of diffuse radiation. Sulfate/nitrate aerosols from anthropogenic sources make dominant contributions of 33 % (36 %) to aerosol DFE under all-sky (clear-sky) conditions, followed by the fraction of 18 % (22 %) by organic carbon aerosols from natural sources. In contrast to other species, black carbon aerosols reduce global GPP by 0.28 (0.12) Pg C yr−1 under all-sky (clear-sky) conditions. Long-term simulations show that aerosol DFE increases 2.9 % yr−1 under all-sky conditions mainly because of a downward trend in cloud amount. This study suggests that the impacts of aerosols and cloud should be considered in projecting future changes of ecosystem productivity under varied emission scenarios.
Highlights
Diffuse light enhances plant photosynthesis more efficiently than direct light (Gu et al, 2002; Alton et al, 2007; Mercado et al, 2009; Jing et al, 2010; Cirino et al, 2014; Zhou et al, 2021a, c)
We further explore the interannual variations in gross primary productivity (GPP) changes caused by aerosol diffuse fertilization effects (DFEs) from natural and anthropogenic sources (Fig. 7)
We quantified the impacts of sky conditions, emission sources, and aerosol species on terrestrial ecosystem productivity through aerosol DFE
Summary
Diffuse light enhances plant photosynthesis more efficiently than direct light (Gu et al, 2002; Alton et al, 2007; Mercado et al, 2009; Jing et al, 2010; Cirino et al, 2014; Zhou et al, 2021a, c). The cause for such a difference is that diffuse light can penetrate into the deep canopy and enhance photosynthesis of more shaded leaves with higher light use efficiency (LUE = GPP / PAR, gross primary productivity per photosynthetically active radiation) (Roderick et al, 2001; Gu et al, 2003; Rap et al, 2015). Zhou et al.: Distinguishing the impacts of natural and anthropogenic aerosols on global GPP
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