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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-156
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-156
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 08 May 2019

Research article | 08 May 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Cushion bogs are stronger carbon dioxide net sinks than moss-dominated bogs as revealed by eddy covariance measurements on Tierra del Fuego, Argentina

David Holl1, Verónica Pancotto2,3, Adrian Heger1, Sergio Jose Camargo3,4, and Lars Kutzbach1 David Holl et al.
  • 1Institute of Soil Science, Center for Earth System Research and Sustainability (CEN), Universität Hamburg, Hamburg, Germany
  • 2Centro Austral de Investigaciones Científicas (CADIC-CONICET), Ushuaia, Argentina
  • 3Universidad de Tierra del Fuego (ICPA-UNTDF), Ushuaia, Argentina
  • 4Dirección de Cambio Climático (DCC), Secretaría de Estado de Ambiente, Desarrollo Sostenible y Cambio Climático (SADSyCC), Ushuaia, Argentina

Abstract. The near-pristine bog ecosystems of Tierra del Fuego in southernmost Patagonia have so far not been studied in terms of their current carbon dioxide (CO2) sink strength. CO2 flux data from southern hemisphere peatlands is scarce in general. In this study, we present CO2 net ecosystem exchange (NEE) fluxes from two Fuegian bog ecosystems with contrasting vegetation communities. One site is located in a glaciogenic valley and developed as a peat moss-dominated raised bog, the other site is a vascular plant-dominated cushion bog located at the coast of the Beagle Channel. We measured NEE fluxes with two identical eddy covariance (EC) setups at both sites for more than two years. With the EC method, we were able to observe NEE fluxes on ecosystem level and at high temporal resolution. Using a mechanistic modeling approach, we estimated daily NEE models to gap-fill and partition the half-hourly net CO2 fluxes into components related to photosynthetic uptake (gross primary production, GPP) and to total ecosystem respiration (TER). We found a larger relative variability of annual NEE sums between both years at the moss-dominated site. A warm and dry first year led to comparably high TER sums. Photosynthesis was also promoted by warmer conditions but less strong than TER with respect to absolute and relative GPP changes. The annual NEE-C uptake was more than three times smaller in the warm year. Close to the sea at the cushion bog site, the mean temperature difference between both observed years was less pronounced, and TER stayed on similar levels. A higher amount of available radiation in the second observed year led to an increase of GPP (5 %) and NEE (35 %) carbon (C) uptake. The average annual NEE-C uptake of the cushion bog (−122 ± 76 g m−2 a−1, n = 2) was more than four times larger than the average uptake of the moss-dominated bog (−27 ± 28 g m−2 a−1, n = 2).

David Holl et al.
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Status: final response (author comments only)
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David Holl et al.
David Holl et al.
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Short summary
We present two years of eddy covariance carbon dioxide flux data from two southern hemisphere peatlands on Tierra del Fuego. One of the investigated sites is a type of bog exclusive to the southern hemisphere that is dominated by vascular, cushion-forming plants and is particularily understudied. One result of this study is that these cushion bogs apparently are highly productive in comparison to northern and southern hemisphere moss-dominated bogs.
We present two years of eddy covariance carbon dioxide flux data from two southern hemisphere...
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