Presence of Eriophorum scheuchzeri enhances substrate availability and methane emission in an Arctic wetland

Abstract

Here we present results from a field experiment in an Arctic wetland situated in Zackenberg, NE Greenland. During one growing season we investigated how dominance of the sedge Eriophorum scheuchzeri affected the below-ground concentrations of low molecular weight carbon compounds (LMWOC) and the fluxes of CO 2 and CH 4 in comparison to dominance of other sedges (Carex stans and Dupontia psilosantha). Three groups of LMWOC were analysed using liquid chromatography-ionspray tandem mass spectrometry, i.e., organic acids (OAs), amino acids (AAs) and simple carbohydrates (CHs). To identify the effect of plant composition the experiments were carried out in a continuous fen area with very little between species variation in environmental conditions, e.g., water-table and active layer thickness and soil temperature. The pool of labile LMWOC compounds in this Arctic fen was dominated by OAs, constituting between 75 and 83% of the total pore water pool of OAs, CHs and AAs. The dominant OA was acetic acid, an easily available substrate for methanogens, which constituted !85% of the OA pool. We estimated that the concentration of acetic acid found in pore water would support 2 e2.5 h of CH 4 flux and an additional continuous input of acetic acid through root exudation that would support 1.3e1.5 h of CH 4 flux. Thus, the results clearly points to the importance of a continuous input for acetoclastic methanogenesis to be sustainable. Additionally, Eriophorum had a very strong effect on parts of the carbon cycle in the Arctic fen. The mean seasonal CH 4 flux was twice as high in Eriophorum dominated plots, most likely due to a 1.7 times higher concentration of OAs in these plots. Further, the ecosystem respiration was 1.3 times higher in Eriophorum dominated plots. In conclusion, the results offer further support to the importance of certain vascular plant species for the carbon cycle of wetland ecosystems.

Plant species, temperature, and bedrock affect net methane flux out of grassland and forest soils

“…Our data give a first insight in how (i) plants alter methane flux of upland soils, (ii) possible temperature changes in these environments might influence CH 4 flux depending on vegetation type and (iii) archaeal community structure differs between bulk and rhizosphere soil and between two species of grassland plants. We propose that plant-induced changes in root exudates may be responsible for the different effects of plants on CH 4 flux rates of well-aerated soils as previously shown for wetlands (Ström et al 2003;Ström et al 2012). Overall, the study is a step towards determining the influence of plants on methane flux of well-aerated soils and emphasizes -in the context of the global relevance of the greenhouse gas methane -the need to better resolve impacts of abiotic and biotic parameters on methane cycle in upland soils.…”

Plant-mediated methane and nitrous oxide fluxes from a carex meadow in Poyang Lake during drawdown periods

“…CH 4 flux depends on the balance between CH 4 production, oxidation and transport. Above-ground shoot clippings not only reduced the labile C into the soil (King and Reeburgh 2002;Ström et al 2012), but also simultaneously influenced plant mediated CH 4 transport and oxidation. For instance, increased CH 4 flux due to clipping of Carex aquatilis was attributed to the removal of the resistance to CH 4 flow within plant tissues (Schimel 1995).…”

“…Plant presence can increase soil CH 4 flux by enhancing substrate availability. There is strong evidence showing that CH 4 emission is favored by photosynthates in the form of root exudates (King and Reeburgh 2002;Dorodnikov et al 2011;Ström et al 2012). The transport of oxygen from shoots to the rhizosphere via aerenchyma can lead to the suppression of methanogenesis and oxidation of CH 4 to CO 2 .…”

Soil moisture, species composition interact to regulate CO2 and CH4 fluxes in dry meadows on the Tibetan Plateau

“…The different sensitivity to soil moisture could be caused by the different substrate availability between communities, as the decrease in substrate availability has been shown to reduce the temperature sensitivity of CH 4 emission (Boardman et al, 2013). But as we have shown earlier, the CH 4 fluxes in these sites were mainly controlled by soil moisture, which have regulated the substrate, the origin of CH 4 production (Bergman et al, 1998;Ellis et al, 2009;Ström et al, 2012), and hence the supply rates to methanogens. The higher soil BD at forb sites might be another explanation (Table 1), which led to less oxygen diffusion and consequently slower oxidation of CH 4 (Konda et al, 2010) as the SWC increased.…”