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 are 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, and 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 2 years. With the EC method, we were able to observe NEE fluxes on an 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 strongly than TER with respect to absolute and relative GPP changes. The annual NEE carbon (C) uptake was more than 3 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 in GPP (5 %) and NEE (35 %) C uptake. The average annual NEE-C uptake of the cushion bog (-122±76 gm-2a-1, n=2) was more than 4 times larger than the average uptake of the moss-dominated bog (-27±28 gm-2a-1, n=2).
<p>We applied the low-cost non-dispersive infrared sensor module K33 (ICB, Senseair, Sweden) for measurements of soil CO<sub>2</sub> concentration. We integrated the sensor module in a new soil probe suitable for in situ measurements of soil gas CO<sub>2</sub> concentration. Therefore, we covered the sensor module with epoxy resin. For continuous measurements, we connected our soil CO<sub>2</sub> probe to a microcontroller (MEGA 2560 Rev3, Arduino.cc, Italy) equipped with a data logging shield (Adalogger FeatherWing, Adafruit, USA). In a laboratory experiment, we evaluated the accuracy and precision of our soil CO<sub>2</sub> probe at changing temperature and humidity by comparison with the often used CO<sub>2</sub> probe GMP343 (Vaisala, Finland) as a reference. In a field experiment, we buried our soil CO<sub>2</sub> probe to test its performance under natural environmental conditions.</p><p>The result of the laboratory experiment is that our soil CO<sub>2</sub> probe compares well with the GMP343, even at maximum relative humidity. The accuracy (<0.1 % CO<sub>2</sub>) was below the accuracy given by the manufacturer. The field experiment demonstrated that our soil CO<sub>2</sub> probe provides high-quality measurements of soil CO<sub>2</sub> concentrations under in situ soil conditions. After retrieving it, it still measured with the same accuracy and precision as before.</p><p>In summary, we used the sensor module K33 for the first time to measure in situ soil CO<sub>2</sub> concentrations by integrating it into a newly developed probe. The cost-efficient availability of our CO<sub>2</sub> probe opens up the opportunity to carry out continuous soil CO<sub>2</sub> measurements over long time periods with simultaneously high spatial resolution.</p>
<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 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&#8201;%) and NEE (35&#8201;%) carbon (C) uptake. The average annual NEE-C uptake of the cushion bog (&#8722;122 &#177; 76&#8201;g&#8201;m<sup>&#8722;2</sup>&#8201;a<sup>&#8722;1</sup>, n = 2) was more than four times larger than the average uptake of the moss-dominated bog (&#8722;27 &#177; 28&#8201;g&#8201;m<sup>&#8722;2</sup>&#8201;a<sup>&#8722;1</sup>, n = 2).</p>
We tested the performance of a newly developed CO 2 probe, K33SOIL [based on the sensor module K33 (Senseair, Sweden)], under harsh temperature and humidity conditions in a laboratory experiment. The K33SOIL, competed well (RMSE = 0.032% CO 2) with the often used GMP343 (Vaisala, Finland) in precision and accuracy. A field experiment showed that the K33SOIL is also suitable for in situ applications. Thus, the K33SOIL is a valuable and cost-efficient tool for measurement of soil CO 2 concentration.
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