Preprints
https://doi.org/10.5194/bg-2020-443
https://doi.org/10.5194/bg-2020-443

  10 Dec 2020

10 Dec 2020

Review status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Competing effects of nitrogen deposition and ozone exposure on Northern hemispheric terrestrial carbon uptake and storage, 1850–2099

Martina Franz1,2 and Sönke Zaehle1,3 Martina Franz and Sönke Zaehle
  • 1Biogeochemical Signals Department, Max Planck Institute for Biogeochemistry, Jena, Germany
  • 2International Max Planck Research School (IMPRS) for Global Biogeochemical Cycles, Jena, Germany
  • 3Michael Stifel Center Jena for Data-driven and Simulation Science, Jena, Germany

Abstract. Tropospheric ozone and nitrogen deposition affect vegetation growth and thus the ability of the land biosphere to store carbon. However, the magnitude of this effect on the contemporary and future terrestrial carbon balance is insufficiently understood. Here, we apply an extended version of the O-CN terrestrial biosphere model that simulates the atmosphere to canopy transport of O3, its surface and stomatal uptake, as well as the ozone-induced leaf injury. We use this model to simulate past and future impacts of air pollution (ozone and nitrogen deposition) against a background of concurrent changes in climate and carbon dioxide concentrations (CO2) for two contrasting representative concentration pathways (RCP) scenarios (RCP2.6 and RCP8.5).

The simulations show that O3-related damage considerably reduced Northern hemispheric gross primary production (GPP) and long-term carbon storage between 1850 and the 2010s. The ozone effect on GPP in the Northern hemisphere peaks at the end of the 20th century with reductions of 4 %, causing a reduction in the Northern hemispheric carbon sink of 0.4 Pg C yr−1. During the 21st century, ozone-induced reductions in GPP and carbon storage is projected to decline through a combination of air pollution control methods that reduce tropospheric O3 and the indirect effects of rising atmospheric CO2, which reduces stomatal uptake of ozone concurrent with increases of leaf-level water-use efficiency.

However, in hotspot regions such as East Asia, the model simulations suggest a sustained decrease of GPP by more than 8 % during the 21st century. Regionally, ozone exposure reduces carbon storage at the end of the 21st century by up to 15 % in parts of Europe, the US and East Asia. These estimates are lower compared to previous studies, which partially results from the explicit representation of non-stomatal ozone destruction, which considerably reduces simulated ozone uptake by leaves and incurred injury.

Our simulations suggest that ozone damage largely offsets the growth stimulating effect induced by nitrogen deposition in the Northern hemisphere until the 2050s. Thus, accounting for the stimulating effects of nitrogen deposition but omitting the detrimental effect of O3 might lead to an over estimation of carbon uptake and storage.

Martina Franz and Sönke Zaehle

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Martina Franz and Sönke Zaehle

Martina Franz and Sönke Zaehle

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Short summary
The combined effects of ozone and nitrogen deposition on the terrestrial carbon uptake and storage has been unclear. Our simulations from 1850 to 2099 show that ozone related damage considerably reduced gross primary production and carbon storage in the past. The growth stimulating effect induced by nitrogen deposition is offset until the 2050s. Accounting for nitrogen deposition without considering ozone effects might lead to an over estimation of terrestrial carbon uptake and storage.
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