Water level, vegetation composition and plant productivity explain greenhouse gas fluxes in temperate cutover fens after inundation

Abstract

Abstract. Rewetting of temperate continental cutover peatlands generally implies the creation of flooded areas, which are – dependent on water depth – colonized by helophytes such as Eriophorum angustifolium, Carex spp., Typha latifolia or Phragmites australis. Reeds of Typha and Phragmites are reported to be large sources of methane, but data on net CO2 uptake are contradictory for Typha and rare for Phragmites. This paper describes the effect of vegetation, water level and nutrient conditions on greenhouse gas (GHG) emissions for representative vegetation types along water level gradients at two rewetted cutover fens (mesotrophic and eutrophic) in Belarus. Greenhouse emissions were measured with manual chambers in weekly to few – weekly intervals over a two years period and interpolated by modelling. All sites had negligible nitrous oxide exchange rates. Most sites were carbon sinks and small GHG sources. Methane emissions were generally associated with net ecosystem CO2 uptake. Small sedges were minor methane emitters and net CO2 sinks, while Phragmites australis sites released large amounts of methane and sequestered very much CO2. Variability of both fluxes increased with site productivity. Floating mats composed of Carex tussocks and Typha latifolia were a source for both methane and CO2. We conclude that shallow, stable flooding is a better measure to arrive at low GHG emissions than deep flooding, and that the risk of high GHG emissions consequent on rewetting is larger for eutrophic than for mesotrophic peatlands.

High net CO<sub>2</sub> and CH<sub>4</sub> release at a eutrophic shallow lake on a formerly drained fen

“…The lower CH 4 emissions of the surface type emergent vegetation might be the result of increased CH 4 oxidation in the soil, as plants with aerenchymatous tissue release oxygen into the rhizosphere, in reverse to the emission of CH 4 into the atmosphere (Bhullar et al, 2013). Minke et al (2015) highlight the difference in net CH 4 release for typical helophyte stands with moderate emissions for Typha dominated sites. Besides the effect of the gas transport within plants, lower water and sediment temperatures due to shading by the emergent vegetation might yield lower CH 4 production than for open water.…”

“…The site was an effective C and GHG source, accounting for 173.4 ± 1.7 g C m −2 a −1 and 1658.5 ± 11.2 g CO 2 - Table 2. Gap-filling model performance was estimated according to Moffat et al (2007) with several measures (n CO 2 = 6193, n CH 4 = 3386, fluxes of best quality QC 0): the adjusted coefficient of determination R 2 adj for phase correlation (significant in all cases, p value < 2.2 × 10 −16 ), the absolute root mean square index (RMSE abs ) and the mean absolute error (MAE) for the magnitude and distribution of individual errors, as well as the bias error (BE) for the bias of the annual sums. Eq m −2 a −1 for the EC source area (see Fig.…”

“…Comparisons might be misleading in case the fractional coverages of the main surface types are not considered. Furthermore, as shown by Wilson et al (2007Wilson et al ( , 2008 and Minke et al (2015) vegetation composition has a remarkable effect on GHG emissions of rewetted peatlands and should be considered within inter-site comparisons.…”

High net CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; release at a eutrophic shallow lake on a formerly drained fen

“…Minke et al (2015) highlight the difference in net CH 4 release for typical helophyte stands with moderate emissions for Typha dominated sites. Besides the effect of the gas transport within plants, lower water and sediment temperatures due to shading by the emergent vegetation might yield lower CH 4 production than for open water.…”

“…Comparisons might be misleading in case the fractional coverages of the main surface types are not considered. Furthermore, as shown by Wilson et al (2007Wilson et al ( , 2008 and Minke et al (2015) vegetation composition has a remarkable effect on GHG emissions of rewetted peatlands and should be considered within inter-site comparisons.…”