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https://doi.org/10.5194/bg-2019-498
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-498
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 07 Feb 2020

Submitted as: research article | 07 Feb 2020

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This preprint is currently under review for the journal BG.

Plant trait response of tundra shrubs to permafrost thaw and nutrient addition

Maitane Iturrate-Garcia1, Monique M. P. D. Heijmans2, J. Hans C. Cornelissen3, Fritz H. Schweingruber4, Pascal A. Niklaus1, and Gabriela Schaepman-Strub1 Maitane Iturrate-Garcia et al.
  • 1Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, 8057, Switzerland
  • 2Plant Ecology and Nature Conservation, Wageningen University & Research, Wageningen, 6700 AA, the Netherlands
  • 3Systems Ecology, Department of Ecological Sciences, Vrije Universiteit Amsterdam, Amsterdam, 1081 HV, the Netherlands
  • 4Swiss Federal Research Institute WSL, Birmensdorf, 8903, Switzerland

Abstract. Plant traits reflect growth strategies and trade-offs in response to environmental conditions. Because of climate warming, plant traits might adapt, altering ecosystem functions and vegetation–climate interactions. Despite important feedbacks of plant trait changes in tundra ecosystems with regional climate, with a key role for shrubs, information on responses of shrub functional traits is limited.

Here, we investigate the effects of experimentally increased permafrost thaw depth and (possibly thaw-associated) soil nutrient availability on plant functional traits and strategies of arctic shrubs in northeastern Siberia. We hypothesize that shrubs will generally shift their strategy from efficient conservation to faster acquisition of resources through adaptation of leaf and stem traits in a coordinated whole-plant fashion. Thereto we ran a 4-year permafrost thaw and nutrient fertilization experiment with a fully factorial block design and six treatment combinations – permafrost thaw (control, unheated cable, heated cable) x fertilization (no-nutrient addition, nutrient addition). We measured ten leaf and stem traits related to growth, defence and the resource economics spectrum in four shrub species, which were sampled in the experimental plots. The plant trait data were statistically analysed using linear mixed-effect models and principal component analysis (PCA).

The response to increased permafrost thaw was not significant for most shrub traits. However, all shrubs responded to the fertilization treatment, despite decreased thaw depth and soil temperature in fertilized plots. Shrubs tended to grow taller, but did not increase their stem density or bark thickness. We found a similar coordinated trait response for all four species at leaf and plant level, i.e. they shifted from a conservative towards a more acquisitive resource economy strategy upon fertilization. In accordance, results point towards a lower investment into defence mechanisms, and hence increased shrub vulnerability to herbivory and climate extremes.

Compared to biomass and height only, detailed data involving individual plant organ traits such as leaf area and nutrient contents or stem water content can contribute to a better mechanistic understanding of feedbacks between shrub growth strategies, permafrost thaw and carbon and energy fluxes. In combination with observational data, these experimental tundra trait data allow for a more realistic representation of tundra shrubs in dynamic vegetation models and robust prediction of ecosystem functions and related climate-vegetation-permafrost feedbacks.

Maitane Iturrate-Garcia et al.

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Maitane Iturrate-Garcia et al.

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Short summary
Changes on plant traits associated to climate warming might alter vegetation-climate interactions. We investigated experimentally the effects of enhanced permafrost thaw and soil nutrients on a wide set of tundra shrub traits. We found a coordinated trait response to some of the treatments, which suggests a shift in shrub resource, growth and defence strategies. This shift might feed back into permafrost thaw − through mechanisms associated with water demand – and into carbon and energy fluxes.
Changes on plant traits associated to climate warming might alter vegetation-climate...
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