Advances in Canadian Peatland Hydrology, 2003-2007

Abstract

Abstract:Peatlands represent over 90% of Canadian wetlands and are the focus of considerable hydrological and biogeochemical research. Research on evapotranspiration (ET) has shown that it can exceed annual precipitation (P) where there are replenishing flood events. Evaporation from open water ponds in boreal peatlands exceeds ET from vegetated riparian zones by about two times, but surrounding forests can shelter small ponds by reducing turbulence. In an open bog, evaporation was modelled by separating the surface into vascular vegetation, hummock moss and hollow moss surfaces, and showed that vascular plants contribute 60-80% of ET, mosses making up the remainder with hummock mosses dominant over hollows. Runoff from peatlands is enhanced by features ranging from headwater swamps, ice-cored peat plateaus, patchy arctic wetlands and even sections of riverine peatlands. Groundwater fluxes can be quite erratic, and depend on transient properties of the peat that depend on moisture content (e.g., unsaturated hydraulic conductivity) to unsteady saturated hydraulic properties (e.g., hydraulic conductivity, specific yield) caused by peat compression and dilation associated with water storage changes. Surface elevation adjustments can result in a more stable depth to water table, increase evaporation losses, increase methane emission, and attenuate pore-water concentration of contaminants. Research on Canadian peatlands has also made significant methodological advances, including measurement of hydraulic properties of living mosses and peat pore-water and pore dimension characteristics. A considerable multi-annual effort has also been made in evaluating carbon dynamics from Canadian peatlands. Summer moisture availability is important to determining carbon fluxes with some peatlands experiencing enhanced productivity following drought (water table drawdown). Sudden changes in water table elevation promote DOC production and export. Methane bubbles confound hydraulic gradients and flows by creating local pockets of pressure, which are then released episodically when the entrapped gas reaches a threshold content. Canadian peatland hydrology continues to be actively researched in lab, field and modelling studies.

Airborne Hyperspectral Evaluation of Maximum Gross Photosynthesis, Gravimetric Water Content, and CO2 Uptake Efficiency of the Mer Bleue Ombrotrophic Peatland

“…Ombrotrophic peatlands are acidic, nutrient-poor ecosystems that receive incoming water and nutrients from precipitation and deposition rather than telluric sources [28]. Vegetation at Mer Bleue has been extensively described in terms of species composition and structural characteristics [29][30][31].…”

Improving Hydrological Predictions in Peatlands

“…The contribution of various peatland vegetation types to evapotranspiration needs to be better understood. Some progress has been made in recent years in understanding ET processes associated with different vegetation and microtopography in peatlands (Waddington et al, 2009).They conclude, for example, that vascular plants can contribute up to 80% of ET in bogs, in spite of the fact that they are dominated by mosses. However, the effect that Sphagnum has on movement of water to the atmosphere needs to be better resolved.…”

“…This paper focuses on hydrological prediction, but we draw attention to other overviews of peatland landforms, hydrology, and ecology, including the review of recent progress in Canadian peatland research (Waddington et al, 2009), the detailed descriptions of peatlands in Canada by the National Wetlands Working Group (NWWG, 1988), the description of the biology of peatlands by Rydin and Jeglum (2006), and the short summaries of research on the dynamics and carbon budget of northern peatlands provided by Yu et al (2002). Detailed description of the functioning of temperate bogs in Ireland are given in the compilation of peatland studies edited by Schouten (2002) and the recent review of climate change effects on peatland edited by Strack (2008).…”

Espèces végétales indicatrices des échanges d’eau entre tourbière et aquifère

“…Des études récentes ont en effet montré que les tourbières peuvent être connectées aux aquifères, malgré la faible conductivité hydraulique de la tourbe (p. ex. : Devito et collab., 1997 ;Bleuten et collab., 2006 ;Waddington et Quinton, 2009).…”