The effect of a reciprocal peat transplant between two contrasting Central European sites on C cycling and C isotope ratios.
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 delta C-13 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 delta C-13 profiles in peat agree. A high degree of within-site homogeneity in delta C-13 was found. When a specific vertical delta C-13 trend was seen in one peat core, the same trend was also seen in all the remaining peat cores from the wetland. The delta C-13 value increased downcore at both CB and VJJ. At VJJ, however, 20 cm below surface, a reversal to lower delta C-13 downcore was seen. Based on Pb-210 dating, peat at 20-cm depth at VJJ was only 15 years old. Increasing delta C-13 values in VJJ peat accumulated between 1880-1990 could not be caused by assimilation of atmospheric CO2 gradually enriched in the light isotope C-12 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.
|Main Author:||Novak, M.|
|Other Authors:||Zemanova, L., Buzek, F., Jackova, I., Adamova, M., Komarek, A., Vile, M., Wieder, R Kelman., Stepanova, M.|