Preprints
https://doi.org/10.5194/bg-2020-440
https://doi.org/10.5194/bg-2020-440

  16 Dec 2020

16 Dec 2020

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

Cushion bog plant community responses to passive warming in southern Patagonia

Verónica Pancotto1,2, David Holl3, Julio Escobar1, María Florencia Castagnani1, and Lars Kutzbach3 Verónica Pancotto et al.
  • 1Centro Austral de Investigaciones Científicas (CADIC-CONICET), Ushuaia, Argentina
  • 2Universidad de Tierra del Fuego (ICPA-UNTDF), Ushuaia, Argentina
  • 3Institute of Soil Science, Center for Earth System Research and Sustainability (CEN), Universität Hamburg, Hamburg, Germany

Abstract. Vascular plant-dominated cushion bogs, which are exclusive to the southern hemisphere, are highly productive and constitute large sinks for atmospheric carbon dioxide compared to their moss-dominated counterparts around the globe. In this study, we experimentally investigated how a cushion bog plant community responded to elevated surface temperature conditions as they are predicted to occur in a future climate. We conducted the study in a cushion bog dominated by Astelia pumila on Tierra del Fuego, Argentina. We installed a year-round passive warming experiment using semicircular plastic walls that raised average near-surface air temperatures between 0.4 °C and 0.7 °C (n = 3). We focused on characterizing differences in morphological cushion plant traits and in carbon dioxide exchange dynamics using chamber gas flux measurements. We used a mechanistic modeling approach to quantify physiological plant traits and to partition the net carbon dioxide flux into its two components photosynthesis and total ecosystem respiration. We found that A. pumila reduced its photosynthetic activity under elevated temperatures. At the same time, we observed enhanced respiration which we largely attribute, due to the limited effect of our passive warming on soil temperatures, to an increase in autotrophic respiration. Passively warmed A. pumila cushions sequestered between 55 % and 85 % less carbon dioxide than untreated control cushions over the main growing season. These results suggest that future warming could decrease the carbon sink function of austral cushion bogs.

Verónica Pancotto et al.

 
Status: final response (author comments only)
Status: final response (author comments only)
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Verónica Pancotto et al.

Verónica Pancotto et al.

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Short summary
We investigated the response of a wetland plant community to elevated temperature conditions in a cushion bog on Tierra del Fuego, Argentina. We measured carbon dioxide fluxes at experimentally warmed plots and at control plots. Warmed plant communities sequestered between 55 % and 85 % less carbon dioxide than untreated control cushions over the main growing season. These results suggest that future warming could decrease the carbon sink function of austral cushion bogs.
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