Preprints
https://doi.org/10.5194/bg-2020-483
https://doi.org/10.5194/bg-2020-483

  24 Feb 2021

24 Feb 2021

Review status: this preprint is currently under review for the journal BG.

A novel representation of biological nitrogen fixation and competitive dynamics between nitrogen-fixing and non-fixing plants in a land model (GFDL LM4.1-BNF)

Sian Kou-Giesbrecht1, Sergey Malyshev2, Isabel Martínez Cano3, Stephen W. Pacala3, Elena Shevliakova2, Thomas A. Bytnerowicz4, and Duncan N. L. Menge1 Sian Kou-Giesbrecht et al.
  • 1Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, 10027, USA
  • 2Geophysical Fluid Dynamics Laboratory (GFDL), National Oceanic and Atmospheric Administration (NOAA), Princeton, 08540, USA
  • 3Department of Ecology and Evolutionary Biology, Princeton University, Princeton, 08544, USA
  • 4Department of Integrative Biology, The University of Texas, Austin, 78712, USA

Abstract. Representing biological nitrogen fixation (BNF) is an important challenge in the incorporation of nitrogen (N) cycling in land models. Initial representations of BNF in land models applied simplified phenomenological relationships. More recent representations of BNF are mechanistic and include the dynamic response of BNF to N limitation of plant growth. However, they generally do not include the competitive dynamics between N-fixing and non-fixing plants, which is a key ecological mechanism that determines ecosystem-scale symbiotic BNF. Furthermore, asymbiotic BNF is generally not included in land models. Here, we present LM4.1-BNF, a novel representation of BNF (asymbiotic and symbiotic) and an updated representation of N cycling in the Geophysical Fluid Dynamics Laboratory Land Model 4.1 (LM4.1). LM4.1-BNF incorporates a mechanistic representation of asymbiotic BNF by soil microbes, a representation of the competitive dynamics between N-fixing and non-fixing plants, and distinct asymbiotic and symbiotic BNF temperature responses derived from corresponding observations. LM4.1-BNF makes reasonable estimations of major carbon (C) and N pools and fluxes and their temporal dynamics, in comparison to the previous version of LM4.1 with N cycling (LM3-SNAP) and to previous representations of BNF in land models generally (phenomenological representations and those without competitive dynamics between N-fixing and non-fixing plants and/or asymbiotic BNF). LM4.1-BNF can be applied to project the dynamic response of vegetation to N limitation of plant growth and the degree to which this will constrain the terrestrial C sink under elevated atmospheric CO2 concentration and other global change factors.

Sian Kou-Giesbrecht et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2020-483', Anonymous Referee #1, 19 Mar 2021
  • RC2: 'Comment on bg-2020-483', Anonymous Referee #2, 29 Mar 2021

Sian Kou-Giesbrecht et al.

Sian Kou-Giesbrecht et al.

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Short summary
Representing biological nitrogen fixation (BNF) is an important challenge for land models. We present a novel representation of BNF and updated nitrogen cycling in a land model. It includes a representation of asymbiotic BNF by soil microbes and the competitive dynamics between nitrogen-fixing and non-fixing plants. It improves estimations of major carbon and nitrogen pools and fluxes and their temporal dynamics in comparison to previous representations of BNF in land models.
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