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 during 2001–2014. Globally, aerosols increase GPP by 8.9 Pg C yr-1 at clear skies but only 0.95 Pg C yr-1 at all skies. 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 at all (clear) skies, followed by the ratio of 18% (22%) by organic carbon aerosols from natural sources. In contrast to other species, black carbon aerosols decrease global GPP by 0.28 (0.12) Pg C yr-1 at all (clear) skies. Long-term simulations show that aerosol DFE is increasing 2.9% yr-1 at all skies 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, 2021b;Zhou et al, 2021c)

  • We explore the impacts of natural and anthropogenic aerosol diffuse fertilization effects (DFEs) on global gross primary productivity (GPP) during 2001-2014 using both multi-source observations and a series of wellvalidated models

  • The Yale Interactive terrestrial Biosphere (YIBs) model simulates reasonable spatial pattern of GPP compared to observations (Figure S1) with a high correlation coefficient (R) of 0.88 (p

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Summary

Introduction

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, 2021b;Zhou et al, 2021c). The cause for such difference is that diffuse light can penetrate into the deep canopy and enhance light use efficiency (LUE=GPP/PAR, gross primary production per photosynthetically active radiation) of shaded leaves (Roderick et al, 2001;Gu et al, 2003;Rap et al, 2015). Atmospheric aerosols can alter the quality of sunlight reaching Earth’s surface by absorbing and scattering solar insolation (Zhou et al, 2021a).

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