The central component of our research is an evolving regional network of four micrometeorological towers across the Taiga Plains, Northwest Territories (Figure 1), to measure vertical flux densities of carbon dioxide, methane, water and heat between the land surface and the atmosphere at ecosystem scale using the eddy covariance technique (Baldocchi et al., 1988; Goulden et al., 2006).
The Taiga Plains ecoclimatic region covers 550,000 km2 and occupies roughly 48% of the Northwest Territories. The regional network spans a ~1,000km latitudinal climate and permafrost gradient from 61° 18’ N in the south near Fort Simpson (mean annual temperature: -3.2°C, total annual precipitation: 300 400mm) to 68° 44’ N in the north near Inuvik (mean annual temperature: -9.3°C, total annual precipitation: 200-300mm). Measurements started at three research sites in April 2013: Scotty Creek (boreal forest-peatland landscape with sporadic permafrost; Quinton et al., 2009) near Fort Simpson, and Havikpak Creek (boreal forest with continuous permafrost; Eaton et al., 2001) and Trail Valley Creek (tundra with continuous permafrost) near Inuvik. Another micrometeorological tower will be constructed and instrumented approximately 30km southeast of Wrigley on the eastern side of the Mackenzie River (scientific name needs to be determined; boreal forest-peatland landscape with discontinuous permafrost) in May 2015.
Three of our four research sites are south of the treeline (Scotty Creek, Wrigley, Havikpak Creek) with characteristic boreal forest vegetation dominated by black spruce (Picea mariana) trees over different shrub species (e.g., Ledum sp., Kalmia sp.), and lichen and mosses (Sphagnum sp.) with interspersed lakes (due to both, geomorphological setting and permafrost degradation resulting in shallow thaw lakes) and peatlands including treeless bogs with different Sphagnum mosses and fens dominated by short canopies of sedges (Carex sp.) and sometimes tamarack (Larix laricina) trees. From south to north, permafrost-supported boreal forest coverage is increasing (Scotty Creek < Wrigley < Havikpak Creek) while mean annual temperature, active-layer thickness, soil organic layer thickness and the number and size of permafrost-free thaw lakes and peatlands are decreasing (Scotty Creek > Wrigley > Havikpak Creek). Since previous studies focusing mostly on tundra sites with continuous permafrost (e.g., Humphreys and Lafleur, 2011), Trail Valley Creek, characterized by mostly short grasses, lichens and Sphagnum mosses is considered to be a representative tundra reference site toward.
The eddy covariance measurements made through this regional network are complemented by repeated surveys and measurements of ground surface and frost table topography, vegetation, and micrometeorological and environmental conditions, respectively, to understand the influence of spatial and temporal permafrost dynamics on vegetation composition, structure and functioning, and by remote sensing-based footprint analysis to characterize landscape heterogeneity.
References: Baldocchi D.D. et al. (1988), Ecology, 69, 1331-1340; Eaton A.K. et al. (2001), Journal of Climate, 14, 3692-3703; Goulden M. et al. (2006), Global Change Biology, 12, 2146-2162; Humphreys E. and Lafleur P. (2011), Geophysical Research Letters, 38, L09703; Quinton W. et al. (2009), Canadian Water Resources Journal, 34, 311-328.
We acknowledge generous funding through various Canada Foundation for Innovation, Natural Sciences and Engineering Research Council, Canada Research Chair, Fonds de recherche du Québec – Nature et technologies, Polar Continental Shelf and Environment Canada programs.