Submitted as: development and technical paper
20 Jul 2022
Submitted as: development and technical paper | 20 Jul 2022
Status: this preprint is currently under review for the journal GMD.

Inclusion of a cold hardening scheme to represent frost tolerance is essential to model realistic plant hydraulics in the Arctic-Boreal Zone in CLM5.0-FATES-Hydro

Marius S. A. Lambert1, Hui Tang2,3, Kjetil S. Aas2, Frode Stordal2, Rosie A. Fisher4, Yilin Fang5, Junyan Ding5, and Frans-Jan W. Parmentier1,6 Marius S. A. Lambert et al.
  • 1Centre for Biogeochemistry in the Anthropocene, Department of Geosciences, University of Oslo, 0315 Oslo, Norway
  • 2Department of Geosciences, University of Oslo, 0315 Oslo, Norway
  • 3Geo-Ecology Research Group, Natural History Museum, University of Oslo, 0562 Oslo, Norway
  • 4CICERO - Center for International Climate Research, 0318 Oslo, Norway
  • 5Pacific Northwest National Laboratory, Richland, WA, USA
  • 6Department of Physical Geography and Ecosystem Science, Lund University, 223 62 Lund, Sweden

Abstract. As temperatures decrease in autumn, vegetation of temperate and boreal ecosystems increases its tolerance to freezing. This process, known as hardening, results in a set of physiological changes at the molecular level that initiate modifications of cell membrane composition and the synthesis of anti-freeze proteins. Together with the freezing of extracellular water, anti-freeze proteins reduce plant water potentials and xylem conductivity. To represent the responses of vegetation to climate change, land surface schemes increasingly employ ‘hydrodynamic’ models that represent the explicit fluxes of water from soil and through plants. The functioning of such schemes under frozen soil conditions, however, is poorly understood. Nonetheless, hydraulic processes are of major importance in the dynamics of these systems, which can suffer from e.g. winter ‘frost drought’ events.

In this study, we implement a scheme that represents hardening into CLM5.0-FATES-Hydro. FATES-Hydro is a plant hydrodynamics module in FATES, a cohort model of vegetation physiology, growth and dynamics hosted in CLM5.0. We find that, in frozen systems, it is necessary to introduce reductions in plant water loss associated with hardening to prevent winter desiccation. This work makes it possible to use CLM5.0-FATES-Hydro to model realistic impacts from frost droughts on vegetation growth and photosynthesis, leading to more reliable projections of how northern ecosystems respond to climate change.

Marius S. A. Lambert et al.

Status: open (until 14 Sep 2022)

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Marius S. A. Lambert et al.

Marius S. A. Lambert et al.


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Short summary
In this study, we implemented a hardening mortality scheme into CTSM5.0-FATES-Hydro, and evaluate how it impacts plant hydraulics and vegetation growth. Our work shows that the hydraulic modifications prescribed by the hardening scheme are necessary to model realistic vegetation growth in cold climates, in contrast to the default model that simulates almost nonexistent and declining vegetation due to abnormally large water loss through the roots.