Biodegradability of Vegetation-Derived Dissolved Organic Carbon in a Cool Temperate Ombrotrophic Bog
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Dissolved organic carbon (DOC) plays a key role in the peatland carbon balance and serves numerous ecological and chemical functions including acting as a microbial substrate. In this study, we quantify the concentration, biodegradability, and intrinsic properties of DOC obtained from peat, fresh material, and litter from nine species of ombrotrophic bog vegetation. Potential biodegradability was assessed by incubating vegetation extracts for 28 days in the dark and measuring percent DOC loss as the fraction of biodegradable DOC (%BDOC) while DOC properties were characterized using UV–Vis absorbance and fluorescence measurements. The mean initial DOC concentration extracted differed significantly among species (P < 0.05) and was significantly higher in fresh material, 217 ± 259 mg DOC l−1, than either litter or peat extracts with mean concentrations of 82.1 ± 117 mg DOC l−1 and 12.7 ± 1.0 mg DOC l−1, respectively (P < 0.05). %BDOC also differed significantly among species (P < 0.05) and ranged from 52 to 73% in fresh cuttings with the greatest fraction observed in S. magellanicum; 22–46% in litter; and 24% in peat. The majority of variability (82.5%) in BDOC was explained by initial absorbance at 254 nm and total dissolved nitrogen concentration which was further resolved into significant non-linear relationships between %BDOC and both humic-like and protein-like DOC fractions (P < 0.05). Our results highlight the extremely heterogeneous nature of the surface vegetation-derived DOC input in peatlands and stress the importance of vegetation species in peatland ecosystem function.
KeywordsDOC biodegradability peatlands vegetation litter nutrients PARAFAC SUVA C:N
We thank the two anonymous reviewers for their valuable input in improving this manuscript and gratefully acknowledge the field and laboratory assistance of Gavin Martin, Chaocheng Liu, Christina Puzzolo, Hicham Benslim, Mike Dalva, and Katherine Velghe. We thank Meng Wang for providing vegetation data on Mer Bleue. A.J.P. was awarded both an Alexander Graham Bell Canada Graduate Scholarship by the Natural Sciences and Engineering Research Council of Canada and a Graduate Stipend Award by the Global Environmental and Climate Change Centre (GEC3) and this research was funded by a Natural Sciences and Engineering Research Council Discovery Grant to T.R.M. We thank the National Capital Commission for access to Mer Bleue.
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