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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 3
Biogeosciences, 14, 511-527, 2017
https://doi.org/10.5194/bg-14-511-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 14, 511-527, 2017
https://doi.org/10.5194/bg-14-511-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 Feb 2017

Research article | 02 Feb 2017

Environmental conditions for alternative tree-cover states in high latitudes

Beniamino Abis1,2 and Victor Brovkin2 Beniamino Abis and Victor Brovkin
  • 1International Max Planck Research School on Earth System Modelling, Hamburg, Germany
  • 2The Land in the Earth System, Max Planck Institute for Meteorology, Hamburg, Germany

Abstract. Previous analysis of the vegetation cover from remote sensing revealed the existence of three alternative modes in the frequency distribution of boreal tree cover: a sparsely vegetated treeless state, an open woodland state, and a forest state. Identifying which are the regions subject to multimodality, and assessing which are the main factors underlying their existence, is important to project future change of natural vegetation cover and its effect on climate.

We study the link between the tree-cover fraction distribution and eight globally observed environmental factors: mean annual rainfall, mean minimum temperature, growing degree days above 0°C, permafrost distribution, mean spring soil moisture, wildfire occurrence frequency, soil texture, and mean thawing depth. Through the use of generalised additive models, conditional histograms, and phase-space analysis, we find that environmental conditions exert a strong control over the tree-cover distribution, uniquely determining its state among the three dominant modes in  ∼ 95% of the cases. Additionally, we find that the link between individual environmental variables and tree cover is different within the four boreal regions considered here, namely eastern North Eurasia, western North Eurasia, eastern North America, and western North America. Furthermore, using a classification based on rainfall, minimum temperatures, permafrost distribution, soil moisture, wildfire frequency, and soil texture, we show the location of areas with potentially alternative tree-cover states under the same environmental conditions in the boreal region. These areas, although encompassing a minor fraction of the boreal area ( ∼ 5%), correspond to possible transition zones with a reduced resilience to disturbances. Hence, they are of interest for a more detailed analysis of land–atmosphere interactions.

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We study the link between the boreal tree-cover fraction distribution and eight globally observed environmental factors. We find that they exert a strong control over the tree-cover distribution, generally uniquely determining its state. Furthermore, we show the location of areas with potentially alternative tree-cover states under the same environmental conditions. These areas represent transition zones with reduced resilience, where the forest can shift between different vegetation states.
We study the link between the boreal tree-cover fraction distribution and eight globally...
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