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| Titel |
Holocene paleohydrology and carbon accumulation in the ombrotrophic peatlands of the North Shore of the Gulf of Saint-Lawrence, Northeastern Canada |
| VerfasserIn |
Gabriel Magnan, Michelle Garneau |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052583
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| Zusammenfassung |
| The peatlands cover about 12% of the land area in Canada. The amount of carbon (C) stored
in these ecosystems is the equivalent of one third of the C content in soils (i.e. ± 135 Gt).
Ombrotrophic peatlands (bogs) are very abundant on the North Shore of the Gulf of
St-Lawrence in Northeastern Canada. These peatlands have developed in two main
geomorphologic contexts: over the deltaic formations from 7500 yr cal. BP and above the
marine sediments after a marine transgression from 4200 yr cal. BP. This study
provides the first detailed reconstruction of the past hydroclimatic conditions and
related carbon dynamics in these peatlands during the Holocene. We present the
long-term rates of C accumulation (LORCA) of 8 coastal bogs along a climatic gradient
from the St-Lawrence estuary to the Gulf of St-Lawrence. A paleohydrological
reconstruction (depth to water table) based on testate ameobae analysis have been
conducted on 3 peat profiles covering the past 7500 years. We show the influence of
paleohydroclimatic conditions and vegetation successions on the long-term variations of
carbon accumulation. The LORCA values range from 22.14 to 67.38 g C m-2 yr-1 with a
mean value of 42.9 g C m-2 yr-1. The mean LORCA were higher in the bogs
that initially developed in a marine environment (55.15 g C m-2 yr-1) compared
to 30.8 g C m-2 yr-1 for those that developed over the well-drained sites on the
deltaic formations. The mean LORCA were significantly higher in the southwest part
of the study area (Baie-Comeau) (60.6 g C m-2 yr-1) compared to 32 g C m-2
yr-1in the northeastern area (Havre St-Pierre). This difference in the LORCA values
could be explained by the contrasting paleohydrological conditions throughout the
Holocene. In the southwestern peatlands, carbon accumulation has been favored by
the maintenance of near-surface water tables throughout the Holocene whereas
the northeastern peatlands were characterized by prolonged periods of dry surface
conditions that slowed down peat accumulation. It seems to reflect a pervasive
climatic influence on carbon accumulation along this south-north gradient. Our results
suggest that the paleohydrological conditions and the related vegetation successions
have played a major role on the long-term carbon dynamics in these peatlands. |
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