Effects of Aerosols on Gross Primary Production from Ecosystems to the Globe

Aerosols affect the gross primary productivity (GPP) of plants by absorbing and scattering solar radiation. However, it is still an open question whether and to what extent the effects of aerosol on the diffuse fraction (D-f) can enhance GPP globally. We quantified the aerosol diffuse fertilization effect (DFE) and incorporated it into a light use efficiency (LUE) model, EC-LUE. The new model is driven by aerosol optical depth (AOD) data and is referred to as AOD-LUE. The eddy correlation variance (EC) of the FLUXNET2015 dataset was used to calibrate and validate the model. The results showed that the newly developed AOD-LUE model improved the performance in simulating GPP across all ecosystem types (R-2 from 0.6 to 0.68), with the highest performance for mixed forest (average R-2 from 0.71 to 0.77) and evergreen broadleaf forest (average R-2 from 0.34 to 0.45). The maximum LUE of diffuse photosynthetic active radiation (PAR) (3.61 g C m(-2) MJ(-1)) was larger than that of direct PAR (1.68 g C m(-2) MJ(-1)) through parameter optimization, indicating that the aerosol DFE seriously affects the estimation of GPP, and the separation of diffuse PAR and direct PAR in the GPP model is necessary. In addition, we used AOD-LUE to quantify the impact of aerosol on GPP. Specifically, aerosols impaired GPP in closed shrub (CSH) by 6.45% but enhanced the GPP of grassland (GRA) and deciduous broadleaf forest (DBF) by 3.19% and 2.63%, respectively. Our study stresses the importance of understanding aerosol-radiation interactions and incorporating aerosol effects into regional and global GPP models.

Automated summary

Aerosols have an impact on the gross primary productivity (GPP) of plants. This study quantifies the aerosol diffuse fertilization effect (DFE) and incorporates it into a light use efficiency model. The results show that the new model improves the performance in simulating GPP and emphasizes the importance of understanding aerosol-radiation interactions and incorporating aerosol effects into GPP models.