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

David Holl, Verónica Pancotto, Adrian Heger, Sergio Jose Camargo, Lars Kutzbach
2019 Biogeosciences Discussions  
<p><strong>Abstract.</strong> 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 (CO<sub>2</sub>) sink strength. CO<sub>2</sub> flux data from southern hemisphere peatlands is scarce in general. In this study, we present CO<sub>2</sub> net ecosystem exchange (NEE) fluxes from two Fuegian bog ecosystems with contrasting vegetation communities. One site is located in a glaciogenic valley and
more » ... 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 CO<sub>2</sub> 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&amp;thinsp;%) and NEE (35&amp;thinsp;%) carbon (C) uptake. The average annual NEE-C uptake of the cushion bog (&amp;minus;122 ± 76&amp;thinsp;g&amp;thinsp;m<sup>&amp;minus;2</sup>&amp;thinsp;a<sup>&amp;minus;1</sup>, n = 2) was more than four times larger than the average uptake of the moss-dominated bog (&amp;minus;27 ± 28&amp;thinsp;g&amp;thinsp;m<sup>&amp;minus;2</sup>&amp;thinsp;a<sup>&amp;minus;1</sup>, n = 2).</p>
doi:10.5194/bg-2019-156 fatcat:44lcp6a62zcnramt3q5zi4wb6u