Surficial geology, northeastern Cameron Hills, Northwest Territories, NTS 85-C/3, 4, 5, and 6

The northeastern Cameron Hills comprise a Cretaceous bedrock upland, rising >550 m above the regional boreal plains. It was inundated by the Laurentide Ice Sheet and includes much of a prominent 60 by 20 km southwest-oriented mega-scale glacial lineation field, formed in thick till. Subsequent ice flow on northeast Cameron Hills occurred north to south, and a series of lobate and ice-thrust moraines suggest glacial surging. Rotational bedrock slumps cover the eastern and northern flanks of Cameron Hills, and extensive alluvial fan deposits draining from these slopes blanket the surrounding topography. The Cameron River formed as a glacial spillway, draining southwest across the upland before turning north and draining into Tathlina Lake. An expansive raised delta and glaciolacustrine sediment cover extending up to ~295 m above sea level, south of Tathlina Lake, records impoundment of an ice-marginal lake between the northeastward-retreating Laurentide Ice Sheet and Cameron Hills.

Roads Impact Tree and Shrub Productivity in Adjacent Boreal Peatlands

Peatlands in the western boreal plains of Canada are important ecosystems as they store over two percent of global terrestrial carbon. However, in recent decades, many of these peatlands have been fragmented by access roads constructed for resource extraction and transportation, challenging their carbon storage potential. To investigate how roads have been impacting tree and shrub growth and productivity in these peatlands, this study was conducted in a forested bog and woody fen in Carmon Creek, Alberta, Canada. In 2017, vegetation surveys were conducted along 20 m transects that extended on both sides of the road with 4 m2 circular plots at 2, 6 and 20 m distance from the road and were followed by disc or core collection from woody stems. Within 20 m of the road at the bog site, we observed a shift towards significantly larger radial growth of trees in the downstream areas (t = 3.23, p = 0.006) where water table position was deeper, while at the fen site, radial growth of tall shrubs had little response to the road. Combining the effects of direct tree clearing and hydrology induced shifts in growth, aboveground net primary productivity (NPPag) post-road construction was reduced significantly in areas where vegetation was cleared during the road construction (i.e., upstream areas of the bog: t = 5.21, p < 0.0001 and downstream areas of the fen: t = 2.64, p = 0.07). Substantially lower NPPag around the road construction areas compared to reference areas shows tremendous loss of carbon sink potential of trees and shrubs after road construction through peatlands. Altogether, roads constructed through peatlands perpendicular to the water flow may shift long-term carbon sinks into sources of carbon, at least for the initial few years following road construction.

The give and take (but mostly take) of forested boreal plains hummocks: Are they hydrologic sources or sinks?

&lt;p&gt;A widely accepted approach in both conceptual and numerical models of groundwater flow is to assume that the water table (WT) is a subdued replica of topography, where groundwater recharges at topographic highs and discharges at topographic lows. However, WTs in low-relief, water-limited environments are generally not topographically controlled, therefore traditional paradigms where forested hummocks are sources of water to both adjacent local wetland-pond systems and catchment-scale runoff do not usually hold true. Local groundwater flow systems (flow in which the recharge area is directly adjacent to its discharge area) are necessary to link forested hummocks with adjacent peatlands or ponds. However, the development of the groundwater mounds beneath topographic highs required to generate local groundwater flow systems is both spatially and temporally infrequent in low-recharge settings like the Boreal Plains. Thus, identifying the spatiotemporal controls on groundwater mounding is crucial to understanding the climatic and geological conditions required for landscape connectivity and runoff generation at larger, regional scales. This insight is becoming increasingly important as water security, ecosystem sustainability, and environmental quality become the focus of land management and reclamation efforts.&lt;/p&gt;&lt;p&gt;The Canadian Boreal Plains are dominated by aspen mixedwood forests, shallow lakes, and peatlands, and has a sub-humid climate that causes large interannual variability in runoff generation and hydrological connectivity at the landscape scale. Through a combination of field observations and numerical modelling, this study identifies the role of aspen forested hummocks in the generation (or loss) of groundwater and hydrologic connectivity to adjacent peatlands and lakes. WT elevations and climate data (precipitation (P) and potential evapotranspiration (PET)) collected over the last 20 years at nine fine-textured forested hummocks were examined for frequency and magnitude of groundwater mounding and/or depressions relative to their adjacent peatlands. It was evident that no simple metric (e.g., annual P, multiyear cumulative P-PET, etc.) was a good predictor for WT position. Through a combination of 1D and 2D, variably saturated numerical modelling, we identify the relative spatiotemporal controls that hummock morphometry, texture, and climate have on groundwater recharge and WT position. Multiple scales of climate forcings (seasonal, interannual; P, PET), substrate texture, hummock height, and rooting parameters all affect groundwater recharge (both positive and negative). Groundwater recharge is most dependent on timing and magnitude of snow melt; however, during periods of large interannual moisture surplus, when available subsurface storage is low, large summer and fall storms can also contribute to recharge. Otherwise, the overwhelming majority of scenarios result in hummocks storing and transpiring water and receiving inputs of groundwater from neighboring peatlands, therefore acting as a net sink of water to the larger landscape.&lt;/p&gt;&lt;p&gt;We show that groundwater mounds, and therfore the development of local topographic flow systems, under forested hummocks are spatiotemporally rare in sub-humid, low-relief regions, resulting in these hummocks being net sinks of water. Not only does this study emphasize the role of peatlands in the generation of landscape-scale runoff, it encourages a reconceptualiztion of the overall hydrologic function of forestlands and peatlands in catchment hydrology.&lt;/p&gt;