CO 2 and CH 4 budgets and global warming potential modifications in Sphagnum -dominated peat mesocosms invaded by Molinia caerulea

<p>Plant communities play a key role in regulating greenhouse gas (GHG) emissions in peatland ecosystems and therefore in their ability to act as carbon (C) sinks. However, in response to global change, a shift from <i>Sphagnum</i>-dominated to vascular-plant-dominated peatlands may occur, with a potential alteration in their C-sink function. To investigate how the main GHG fluxes (<span class="inline-formula">CO₂</span> and <span class="inline-formula">CH₄</span>) are affected by a plant community change (shift from dominance of <i>Sphagnum</i> mosses to vascular plants, i.e., <i>Molinia caerulea</i>), a mesocosm experiment was set up. Gross primary production (GPP), ecosystem respiration (ER) and <span class="inline-formula">CH₄</span> emission models were used to estimate the annual C balance and global warming potential under both vegetation covers. While the ER and <span class="inline-formula">CH₄</span> emission models estimated an output of, respectively, <span class="inline-formula">376±108</span> and <span class="inline-formula">7±4</span>&thinsp;g&thinsp;C&thinsp;m<span class="inline-formula">⁻²</span>&thinsp;yr<span class="inline-formula">⁻¹</span> in <i>Sphagnum</i> mesocosms, this reached <span class="inline-formula">1018±362</span> and <span class="inline-formula">33±8</span>&thinsp;g&thinsp;C&thinsp;m<span class="inline-formula">⁻²</span>&thinsp;yr<span class="inline-formula">⁻¹</span> in mesocosms with <i>Sphagnum rubellum</i> and <i>Molinia caerulea</i>. Annual modeled GPP was estimated at <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">414</mn><mo>±</mo><mn mathvariant="normal">122</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="14d1803f298fe53752c40f4ece37456f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-16-4085-2019-ie00001.svg" width="58pt" height="10pt" src="bg-16-4085-2019-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">1273</mn><mo>±</mo><mn mathvariant="normal">482</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="c8ceebb5d8841b6e14106cdd57900ea3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-16-4085-2019-ie00002.svg" width="64pt" height="10pt" src="bg-16-4085-2019-ie00002.png"/></svg:svg></span></span>&thinsp;g&thinsp;C&thinsp;m<span class="inline-formula">⁻²</span>&thinsp;yr<span class="inline-formula">⁻¹</span> in <i>Sphagnum</i> and <i>Sphagnum</i> + <i>Molinia</i> plots, respectively, leading to an annual <span class="inline-formula">CO₂</span> and <span class="inline-formula">CH₄</span> budget of <span class="inline-formula">−</span>30&thinsp;g&thinsp;C&thinsp;m<span class="inline-formula">⁻²</span>&thinsp;yr<span class="inline-formula">⁻¹</span> in <i>Sphagnum</i> plots and of <span class="inline-formula">−</span>223&thinsp;g&thinsp;C&thinsp;m<span class="inline-formula">⁻²</span>&thinsp;yr<span class="inline-formula">⁻¹</span> in <i>Sphagnum</i> + <i>Molinia</i> ones (i.e., a C sink). Even if <span class="inline-formula">CH₄</span> emissions accounted for a small part of the gaseous C efflux (ca. 3&thinsp;%), their global warming potential value makes both plant communities have a climate warming effect. The shift of vegetation from <i>Sphagnum</i> mosses to <i>Molinia caerulea</i> seems beneficial for C sequestration at a gaseous level. However, roots and litter of <i>Molinia caerulea</i> could provide substrates for C emissions that were not taken into account in the short measurement period studied here.</p>

Abstract licence: CC BY

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