The effect of vascular plants on carbon turnover and methane emissions from a tundra wetland

Abstract

This paper investigates how vascular plants affect carbon flow and the formation and emission of the greenhouse gas methane (CH4) in an arctic wet tundra ecosystem in NE Greenland. We present a field experiment where we studied, in particular, how species‐specific root exudation patterns affect the availability of acetate, a hypothesized precursor of CH4 formation. We found significantly higher acetate formation rates in the root vicinity of Eriophorum scheuchzeri compared with another dominating sedge in the wetland, i.e. Dupontia psilosantha. Furthermore a shading treatment, which reduced net photosynthesis, resulted in significantly decreased formation rates of acetate. We also found that the potential CH4 production of the peat profile was highly positively correlated to the concentration of acetate at the respective depths, whereas it was negatively correlated to the concentration of total dissolved organic carbon. This suggests that acetate is a substrate of importance to the methanogens in the studied ecosystem and that acetate concentration in this case can serve as a predictor of substrate quality. To further investigate the importance of acetate as a predecessor to CH4, we brought an intact peat‐plant monolith system collected at the field site in NE Greenland to the laboratory, sealed it hermetically and studied the decomposition of 14C‐labelled acetate injected at the depth of methanogenic activity. After 4 h, 14CH4 emission from the monolith could be observed. In conclusion, allocation of recently fixed carbon to the roots of certain species of vascular plants affects substrate quality and influence CH4 formation.

Summer fluxes of methane and carbon dioxide from a pond and floating mat in a continental Canadian peatland

“…Also recently fixed substrates may have played a role for high CH 4 emissions from the floating mat. Several studies have found a positive correlation between the rate of photosynthesis and CH 4 emissions (Joabsson and Christensen, 2001;Ström et al, 2003), which has been explained by the quick allocation of assimilated labile carbon to the roots and subsequent exudation to the anaerobic rhizosphere (Dorodnikov et al, 2011). These recent photosynthates serve as a preferential source of CH 4 compared to older more recalcitrant organic matter (Chanton et al, 1995).…”

Root oxygen loss from Raphia taedigera palms mediates greenhouse gas emissions in lowland neotropical peatlands

“…For example, the photosynthetic activity of trees is correlated strongly with soil respiration in temperate savannah and temperate peatlands (Mikkelä et al 1995;Tang et al 2005; Thomas et al 1996). The release of photosynthates through the rhizosphere provide labile substrate for decomposer organisms (Silvola et al 1996;Ström et al 2003;Wright et al 2011), influencing the diurnal pattern of CO 2 and CH 4 emissions in both temperate and tropical ecosystems (Bahn et al 2009;Wright et al 2013b). Therefore, it is important to measure greenhouse gas fluxes on a diurnal basis, as this allows investigation of biotic and abiotic controls on the temporal variation of greenhouse gas emissions (Armstrong 1971;Ström et al 2003;Wang and Han 2005).…”

“…The release of photosynthates through the rhizosphere provide labile substrate for decomposer organisms (Silvola et al 1996;Ström et al 2003;Wright et al 2011), influencing the diurnal pattern of CO 2 and CH 4 emissions in both temperate and tropical ecosystems (Bahn et al 2009;Wright et al 2013b). Therefore, it is important to measure greenhouse gas fluxes on a diurnal basis, as this allows investigation of biotic and abiotic controls on the temporal variation of greenhouse gas emissions (Armstrong 1971;Ström et al 2003;Wang and Han 2005). Importantly, it allows for the separation of long-term drivers which can strongly vary seasonally, e.g., temperature, humidity, and precipitation.…”

Spatial and temporal variability in CH4 and N2O fluxes from a Scottish ombrotrophic peatland: Implications for modelling and up-scaling

“…The preferential colonisation of hummocks or hollows by distinct plant communities reinforces differences due to topography alone by influencing the quantity and quality of soil organic substrate, and altering the aerobic capacity of the peat by transporting O 2 to the rhizosphere. Plants containing aerenchymous tissue can also provide a direct pathway for many GHGs to the atmosphere, bypassing the aerobic peat horizon, and greatly increasing soilatmosphere fluxes (Whiting and Chanton, 1996;Ström et al, 2003;Minkkinen and Laine, 2006). A clear understanding of the major sources of variation within a site is essential both during the set-up of a study, when choosing where to place individual chambers, and during the up-scaling process so that individual chamber fluxes can be correctly weighted in the final estimate.…”