The effect of a reciprocal peat transplant between two contrasting Central European sites on C cycling and C isotope ratios

Abstract

Abstract. An 18-month reciprocal peat transplant experiment was conducted between two peatlands in the Czech Republic. Both sites were 100% Sphagnum-covered, with no vascular plants, and no hummocks and hollows. Atmospheric depositions of sulfur were up to 10 times higher at the northern site Velke jerabi jezero (VJJ), compared to the southern site Cervene blato (CB). Forty-cm deep peat cores, 10-cm in diameter, were used as transplants and controls in five replicates. Our objective was to evaluate whether CO2 and CH4 emissions from Sphagnum peat bogs are governed mainly by organic matter quality in the substrate, or by environmental conditions. Emission rates and δ13C values of CO2 and CH4 were measured in the laboratory at time t=18 months. All measured parameters converged to those of the host site, indicating that, at least in the short-term perspective, environmental conditions were a more important control of greenhouse gas emissions than organic carbon quality in the substrate. Since sulfate reducers outcompete methanogens, we hypothesized that the S-polluted site VJJ should have lower methane emissions than CB. In fact, the opposite was true, with significantly (p<0.01) higher methane emissions from VJJ. Additionally, as a first step in an effort to link C isotope composition of emitted gases and residual peat substrate, we determined whether multiple vertical δ13C profiles in peat agree. A high degree of within-site homogeneity in δ13C was found. When a specific vertical δ13C trend was seen in one peat core, the same trend was also seen in all the remaining peat cores from the wetland. The δ13C value increased downcore at both CB and VJJ. At VJJ, however, 20 cm below surface, a reversal to lower δ13C downcore was seen. Based on 210Pb dating, peat at 20-cm depth at VJJ was only 15 years old. Increasing δ13C values in VJJ peat accumulated between 1880–1990 could not be caused by assimilation of atmospheric CO2 gradually enriched in the light isotope 12C due to fossil fuel burning. Rather they were a result of a combination of isotope fractionations accompanying assimilation and mineralization of Sphagnum C. These isotope fractionations may record information about past changes in C storage in wetlands.

Experimental Evidence for Mobility/Immobility of Metals in Peat

“…For the peat transplant experiment described here, we have reported data on carbon translocations. 39 Soon after the peat monoliths were transplanted to their host site, the imported peat moisture was flushed out and replaced by advecting bogwater of the host site. Terminal C mineralization was governed by pore water rather than by solids.…”

Assessing DOC export from a Sphagnum‐dominated peatland using δ13C and δ18O–H2O stable isotopes

“…Several previous studies (Broder, Blodau, Biester, & Knorr, ; Knorr, Glaser, & Blodau, ; Novak et al, ) have reported a shift to isotopically heavier C from the living moss to the shallowest peat sections, similar to that in Figure b. This C isotope shift in waterlogged soils has been interpreted as a result of degradation of young, labile organic molecules, with preferential removal of isotopically light C in a gaseous or liquid form (cf.…”

“…Joint interpretation of peaks in δ 13 C peat values, C/N ratios, δ 18 O H2O values, and DOC concentrations in Brumiste porewater profiles must be done with caution: These peaks were not found at the same depth. We note, however, that 210 Pb dating of vertical peat profiles at mountain‐top Sphagnum ‐dominated sites in the Czech Republic, similar to Brumiste, has shown a considerable scatter in ages of peat layers, even within a single site (Novak et al, ; ; Novak, Erel, Zemanova, Bottrell, & Adamova , ; Vile, Wieder, & Novak, ).…”

Stable carbon isotope analysis of fluvial sediment fluxes over two contrasting C4‐C3 semi‐arid vegetation transitions

“…leaf samples. This suggests possible input from low‐abundance C 3 plants unaccounted for in the sampling strategy, that 12 C is lost preferentially during decomposition, selective decomposition of C 4 plant litter, or selective preservation of naturally 13 C‐depleted components of plant litter, i.e. lipids …”