Degradation changes stable carbon isotope depth profiles in palsa peatlands

[摘要] Palsa peatlands are a significant carbon pool in the global carbon cycle andare projected to change by global warming due to accelerated permafrost thaw.Our aim was to use stable carbon isotopes as indicators of palsa degradation.Depth profiles of stable carbon isotopes generally reflect organic matterdynamics in soils with an increase of δ¹³C values during aerobicdecomposition and stable or decreasing δ¹³C values with depthduring anaerobic decomposition. Stable carbon isotope depth profiles ofundisturbed and degraded sites of hummocks as well as hollows at three palsapeatlands in northern Sweden were used to investigate the degradationprocesses. The depth patterns of stable isotopes clearly differ betweenintact and degraded hummocks at all sites. Erosion and cryoturbation at thedegraded sites significantly changes the stable carbon isotope depthprofiles. At the intact hummocks the uplifting of peat material by permafrostis indicated by a turning in the δ¹³C depth trend, and thisassessment is supported by a change in the C / N ratios. For hollowsisotope patterns were less clear, but some hollows and degraded hollows inthe palsa peatlands show differences in their stable carbon isotope depthprofiles indicating enhanced degradation rates. We conclude that thedegradation of palsa peatlands by accelerated permafrost thawing can beidentified with stable carbon isotope depth profiles. At intact hummocksδ¹³C depth patterns display the uplifting of peat material by achange in peat decomposition processes.

[学科分类] 地球化学与岩石