Tab. S1: 14 C age dating of peat layers from each site, near-natural (NW), extensive managed grassland (GE) and intensive managed grassland (GI) site, from the Ahlen-Falkenberger peatland.Uncertainties of F14C values represent one sigma.For calibrated ages, the lower and upper boundary is given with 95% confidence.Calibrated ages are displayed as years AD/BC.
Globally, peatlands have been recognized as important carbon sinks while only covering approximately 3% of the earth’s land surface. Root exudates are known key drivers of C cycling in soils and rhizosphere priming effects have been studied extensively in terrestrial ecosystems. Their role for decomposition of peat still remains unclear, as little research about their fate and potential priming effects in peat exists. In this study, we aimed to evaluate pathways of root exudates and their short-term priming effects by daily determination of stable carbon isotope fluxes of CO2 and CH4. As the drainage of peatlands strongly alters processes of decomposition, we included measurements after drainage as well. Results revealed the immediate respiration of root exudates in peat, mainly as CO2, while CH4 release was associated with a lag time of several days. However, the largest proportion of added root exudates remained in the solid and liquid phase of peat. In conclusion, our findings suggest that no priming occurred as added substrates remained immobile in peat.
Abstract. Inclination and spatial variability in soil and litter properties influence soil greenhouse gas (GHG) fluxes and thus ongoing climate change, but their relationship in forest ecosystems is poorly understood. To elucidate this, we explored the effect of inclination, distance from a stream, soil moisture, soil temperature, and other soil and litter properties on soil–atmosphere fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) with automated static chambers in a temperate upland forest in eastern Austria. We hypothesised that soil CO2 emissions and CH4 uptake are higher in sloped locations with lower soil moisture content, whereas soil N2O emissions are higher in flat, wetter locations. During the measurement period, soil CO2 emissions were significantly higher on flat locations (p<0.05), and increased with increasing soil temperature (p<0.001) and decreasing soil moisture (p<0.001). The soil acted as a CH4 sink, and CH4 uptake was not significantly related to inclination. However, CH4 uptake was significantly higher at locations furthest away from the stream as compared to at the stream (p<0.001) and positively related to litter weight and soil C content (p<0.01). N2O fluxes were significantly higher on flat locations and further away from the stream (p<0.05) and increased with increasing soil moisture (p<0.001), soil temperature (p<0.001), and litter depth (p<0.05). Overall, this study underlines the importance of inclination and the resulting soil and litter properties in predicting GHG fluxes from forest soils and therefore their potential source-sink balance.
Microbially mediated methanogenesis is a considerable source of methane (CH4) and has a major role in the global carbon cycle. In peatlands, acetate, CO2 and methylated compounds are precursors for CH4 and different substrates are used by different microorganisms. CH4 may be produced by a) acetate disproportionation (acetoclastic/acetotrophic methanogenesis), b) reduction of carbon dioxide by dihydrogen (hydrogenotrophic methanogenesis), and c) using methylated compounds (methylotrophic methanogenesis). As different methane sources have different carbon isotopic ratios, those signatures may be used to divide emissions from different sources, although these can vary temporally and spatially. Here, we hypothesize that CH4 production pathways from Sphagnum peat with clipped vascular vegetation (Callluna Vulgaris) significantly differs from CH4 production pathways from peat cores with vascular plant cover.In order to test this hypothesis, six undisturbed peat mesocosms from Pürgschachen Moor were sampled to determine the CO2 and CH4 efflux and its 12C/13C signature for four weeks. Three control cores were left unclipped as control and in three cores, vascular vegetation was clipped to assess the significance of vascular vegetation to CH4 emissions. Ancillary parameters examined were dissolved organic carbon and acetate concentrations in peat pore water as well as hot water soluble carbon from peat.CO2 fluxes ranged in clipped cores between 2.4 to 12.2 g m-2 h-1 and in control cores between 4.13 to 14.6 g m-2 h-1. CH4 fluxes ranged from 0.058 to 0.16 g m2 h-1 in the clipped cores and from 0.046 to 0.751 g m2 h-1 in the control group. For both CO2 and CH4, treatment had a significant effect on the fluxes.  δ13C for CH4 values in the experiment group (-55.6 ± 2.45‰) were in the same range as the control group, whereas after the clipping the experiment group values slightly decreased to -54.1 ± 2.65‰. For the control group, δ13C values were -55 ± 2.2‰. δ13CO2 was -11.2 ± 0.72‰ before and -10.8 ± 0.67‰ after clipping in the experiment group. In the control group, the average was -11.2 ± 0.71‰.Taking into consideration the aforementioned results and other parameters measured throughout this study, it can be acclaimed that the presence of vascular vegetation changes the ability of the peat profile to produce and emit both CO2 and CH4. Even though no significant difference found between the control and the experiment group for δ13CH4, it can be acclaimed that in Pürgschachen Moor the hydrogenotrophic pathway is dominant, with average δ13CH4 values of -55 ± 2 ‰, although both pathways coexist.
