Abstract
Globally, large-scale land drainage has severely deteriorated the functioning and services of peatlands, making restoration plans of the utmost importance. Rewetting is essential for the restoration of drained peatlands, but the level of success including greenhouse gas (GHG) mitigation largely depends on the soil microbiome interactions under the prevailing biogeochemical conditions. Here, we investigated the effects of inundation of drained iron (Fe) -rich peat topsoils on nutrient release, surface water quality, GHG production and consumption, and on the composition and activity of the microbial community. The effect of the addition of different potential electron acceptors on methane (CH4) production and consumption were studied in incubation experiments. In response to inundation, porewater concentrations of Fe, total inorganic carbon, ammonium, and phosphorus increased. CH4 emissions increased in the control (i.e. without any additions) and Fe(III) oxide amended incubations upon inundation. This could be explained by the increase in the relative abundance of methanogens even though Fe(III) was previously hypothesized to lower methanogenic activity. In contrast, nitrite, nitrate, and sulfate-rich incubations inhibited methanogenesis. The prolonged exposure to nitrogen oxides stimulated denitrification with nitrous oxide (N2O) as the main gaseous product, together with an increase in the relative abundance of denitrifying microorganisms. Our results demonstrate that insights into the changes in microbial communities in relation to soil geochemistry explain differences in responses observed in different peat soils observed upon inundation. The increase in emissions of the potent GHGs CH4 and N2O from Fe-rich peat topsoils are a major adverse effect in the early stage of inundation.
Highlights
Widespread drainage is compromising the capacity of the world’s peatlands to serve as sinks for nutrients and carbon (C) (Lamers et al, 2015)
Samples were analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES) for Al, Ca, Fe, Mg, Mn, P, and S with a sea spray nebulizer combined with a cyclone chamber
Quantification was performed based on cali bration curves which were calculated from different volume injections of a standard gas (Linde Gas Benelux BV, The Netherlands)
Summary
Widespread drainage is compromising the capacity of the world’s peatlands to serve as sinks for nutrients and carbon (C) (Lamers et al, 2015). As a result, drained peat lands have become net C sources, with an annual global emission of approximately 2 Gt carbon dioxide (CO2). This is around 5% of all anthropogenic greenhouse gas (GHG) emissions originating from only 0.3% of the global land surface (Joosten et al, 2016). This drainage has caused severe land subsidence (2–150 mm yr− 1, depending on the region) (Leifeld et al, 2011; Syvitski et al, 2009), which may lead to high costs for infrastructure and, together with the anticipated sea-level rise, poses a severe inundation risk to often highly populated riverine areas and coastal deltas. The evolution of GHG emission patterns following rewetting can vary substantially (from years to decades) depending on previous land use, restoration methods applied, and local climate conditions (Baird et al, 2013; Beetz et al, 2013; Juottonen et al, 2012; Mohamed Abdalla et al, 2016; Samaritani et al, 2011; Strack and Zuback, 2013; Wen et al, 2018)
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