courriel : alice.schaffhauser.1@ulaval.ca

Paleoecology and pedogeomorphology of bogs in Côte Nord (Québec, Canada)

Direction :
Serge Payette

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If the bogs (ombrotrophic peatlands) are some of the poorest ecosystems in the Earth (Damman, 1986), their ecological and paleoecological interest is not less relevant. In particular, their morphological diversity is linked with the conditions and the time of paludification of the great sedimentation basins for the concerned deltas. Some characteristics are still poorly known, such as the importance of the underground drainage in the development of bogs (Glaser, 1987; Siegel & Glaser, 1987). In the Côte Nord, the bogs are post-glacial deltas depressions between Tadoussac and Natashquan, with a mean rate of vertical accumulation from 0.13 to 1.1 mm/year (median 0.4 mm/year, Dionne 2008), which is low but comparable with the peatlands from Terre-Neuve to Manitoba. They are a part of the non forested bogs and permafrost bogs described by Payette and Rochefort (2001). The main objective of this project of research is the determination and the reconstitution of ecological conditions of the initial peatland formation processes of these bogs. The first objective aims to date with radiocarbon (Accelerator Mass Spectrometry, AMS) the first peat layers, organic and mineral soil layers in order to evaluate the time of paludification. Sampling is done along a toposequence from the forest to the bog in an exploited site (Baie-Comeau, Pointe-Lebel). A topographic profile of the surface and the base of each bog is realised, with organic and mineral samples every 100 meters. This work can be completed with other studies (Sept-Iles and Havre Saint-Pierre) according to the altitude to take into account the postglacial raising in the peatland formation process. The second objective is to evaluate the characteristics of the peatland formation process of each sampled bog, using the macroremain and pollen analysis of the peat base. Thus, we will identify the composition of the initial vegetation. The hypothesis of an initial forested vegetation leading to the accumulation of peat will be tested by comparisons with macroremain spectra. The duration of the original forested period will be estimated with wood remains. The third objective is to complete the macroremain analysis with the examination of mineral deposits on which each bog was formed. The conditions of the soil formation before peatland formation will be identified and interpreted in the postglacial geomorphological and pedological contexts. The hypothesis of the paludification from a Holocene podzol soil will be tested by the pedo-geomorphological examination of the underlying deposits. The pedogenetic characteristics of the mineral soils accumulating peat will be described, both on physicals (layers, particle size, indurations, etc.) and chemicals (organic C concentration, extracted Fe and Al with pyrophosphate, etc.) according to the procedures of the Canadian System of Soil Classification (2002). At last, the influence of paleo-fires on peatland formation process will be studied through a research program on charcoals of mineral soils in the boreal forest. This program aims to characterize the Holocene fire regime of different conifer forests.

References:

Damman, A.W.H. 1986. Hydrology, development, and biogeochemistry of ombrogenous peat bogs with special reference to nutrient relocation in a western Newfoundland bog. Canadian Journal of Botany, 64 : 384-394.

Dionne, J.C. 2008. Aperçu de l’âge et du taux d’accrétion verticale de tourbières de la Côte-Nord du Saint-Laurent d’après les datations au C14 disponibles. Bulletin de l’Association Québecoise pour l’étude du Quaternaire, 34 : 7-11.

Glaser, P.H. 1987. The ecology of patterned boreal peatlands or northern Minnesota: A community profile. U.S. Fish and Wildlife Service. Biological Report 85. Washington, D.C.

Payette, S. & Rochefort, L. 2001. Écologie des tourbières du Québec-Labrador Les Presses de l'Université Laval, Québec, 621 p. Siegel, D.I. & Glaser, P.H. 1987. Groundwater flow in a bog-fen complex, Lost River Peatland, northern Minnesota. Journal of Ecology 75:743-754.

Système canadien de classification des sols. 2002. Groupe de travail sur la classification des sols. Séries: Publication (Canada. Agriculture et agroalimentaire Canada) -- 1646/F, 3. éd., xiii, 196 p.