Alberta Foothills Research Articles

Trust Fall

A gloomy landscape frames a worn yet charismatic stone, carried to the Alberta foothills centuries ago by receding glaciers. Around the rock is a trampled path of dirt and plants that was imprinted onto the land by bison who rubbed against the rock to shed their winter coats. Hidden off to the side is an artist, patiently gathering video footage of this rock and its material history. Thus begins a relationship between a migrant stone, a herd of prairie animals, and an artistic intuition about the importance of watching and listening to the environment around us. Rubbing Rock, 2016. Photo © Moria Whiteman A video of this stone is the centrepiece of a recent project by Maria Whiteman that examines questions of geological time and tells (or re-tells) the stories of the lands she encounters. In Whiteman’s work, the stone is juxtaposed with videos of bison, of other environmental sites, and of close shots of grass, ice and water. One might read in this another form of rubbing – not this time the desire to remove a winter coat but rather to contrast the speed of various environmental vitalities. In Whiteman's work the stone is not just a stone but a metaphor – a ‘rubbing rock’ that is also about reconsidering our tactile and kinaesthetic relationships with the landscape. At the same time, the stone is not a metaphor at all – it is actually a stone, and to put poetic elaborations aside is ultimately what grounds the very gaze the poetic intervention seeks to raise. This essay meditates on the use of the rubbing rock in and around Whiteman's work, as a method for thinking about the meeting points of artistic and environmental complexity.

Long-term responses of ground beetles (Coleoptera: Carabidae) to clear-cutting and wildfire in lodgepole pine stands of western Alberta, Canada

Abstract We studied responses of carabid beetles (Coleoptera: Carabidae) to clear-cutting and wildfire in lodgepole pine forests in the foothills of Alberta, Canada during 2013–2014 and compared the results with those from a similar study conducted in the same area during 1989–1990. Assemblages from stands regenerating 12–53 years after harvest gradually recovered towards their presumed preharvest condition represented by old pyrogenic stands. Assemblage structure in postharvest stands of similar age had also largely converged with that in stands that had burned in 1957 and 1997. Composition of ground vegetation, mineral soil cover, and basal area of trees and shrubs were significantly correlated with carabid assemblage structure, suggesting that plant successional gradients and patterns in carabid assemblages are driven by similar factors. We found that no carabid species was strictly associated with old pyrogenic stands, although assemblages in pyrogenic stands were distinctive. We predict that composition of carabid assemblages in harvested stands will recover and roughly match the variable structure of assemblages remaining in old, never-cut pyrogenic stands, given sufficient time (≥ 50 years). Nonetheless, the carabid fauna of the eastern slopes of Alberta’s Rocky Mountains appears to be changing in response to factors other than forestry. Warming climate is an explanation consistent with the changes observed.

Growth and yield of lodgepole pine stands disturbed by mountain pine beetle in the Lower Foothills of Alberta

Changes in the structure and dynamics of lodgepole pine stands following the 2006 outbreak of mountain pine beetle in western Alberta were investigated by monitoring attacked permanent sample plots over the following decade and projecting future stand development with locally validated growth models. Results suggest that a wide range in growth and yield of attacked stands is likely, with projected impacts varying from minor and inconsequential modifications to full stand replacement. Severely disturbed stands are unlikely to naturally regenerate to pine. The degree to which timber production is naturally restored in such stands will depend to a large extent on the amount and composition of non-pine advance growth and regeneration. Variation in attack severity and tree species composition will, in the absence of clearcutting following disturbance, result in increased diversity in stand and forest structure. Recommendations are made for scheduling salvage and restoration operations to ameliorate losses in timber supply.

Interaction of folding and thrusting during fold-and-thrust-belt evolution: Insights from numerical simulations and application to the Swiss Jura and the Canadian Foothills

We use two-dimensional numerical simulations to investigate the interaction of folding (buckling) and thrusting (localized shearing) during the structural evolution of fold-and-thrust belts (FTB). We model layer-parallel shortening of mechanically strong layers resting above a weaker layer, referred to as detachment. We consider a viscoplastic rheology with linear viscosity and frictional-plastic Drucker-Prager yield criterion. The detachment thickness is larger in one model half and only this geometrical thickness perturbation triggers folding and thrusting in the simulations. We conduct a systematic analysis to quantify the impact of model parameters, such as magnitude of the thickness perturbation or detachment rheology (frictional or viscous), on the FTB evolution. The magnitude of the perturbation determines whether, or not, folding is favoured over thrusting and, hence, controls the progressive interaction of folding and thrusting during FTB evolution. The asymmetry of modelled anticlines is proportional to the relative height of the initial perturbation. We also adapt the model configuration to specific mechanical stratigraphies of two regions in natural FTB, namely the Haute-Chaîne of the Jura Mountains (Switzerland) and the Foothills of Alberta (Canada). The modelled fold and thrust geometries agree with different types of observed anticlinal structures, such as symmetric detachments folds and asymmetric thrust-folds. Our results suggest that an initial stage of low-amplitude buckling likely occurred prior to the main folding and thrusting phase. We argue that folding and thrusting are equally important and interacting processes during the structural evolution of many natural FTB.

Integrating livestock management and telemetry data to assess disease transmission risk between wildlife and livestock

Overlap of cattle and wild elk ranges in southwestern Alberta foothills is an opportunity for inter-species interactions. To assess the spatio-temporal patterns of disease transmission risk between cattle and elk, several risk indexes were defined to represent different transmission routes. Risk indexes were estimated by combining elk telemetry data obtained from 168 GPS-collared elk, and cattle management information obtained by interviews conducted in 16 cow-calf operations overlapping the elk home range. We assessed the bias resulting from ignoring cattle movement related to seasonnal grazing practices, and the impact of the assessment of spatio-temporal patterns of risk.Direct transmission risk indexes peaked during winter months, due to aggregation at higher densities of both elk and cattle on winter ranges and winter pastures, respectively. However, a summer peak also was observed when risk indexes were not adjusted for pasture area, due to larger cattle summer pastures overlapping a higher number of elk telemetry locations. We identified periods when the proximity of elk to specific features (such as mineral blocks, hay land, winter-feeding areas, or water sources) may increase the risk of inter-species transmission. Indirect transmission risk indexes increased with the survival of pathogens in the environment, as the temporal constraint for cattle and elk overlap decreased. Finally, integrating pasture management information substantially influenced the magnitude and temporal patterns of transmission risk indexes, highlighting the importance of collecting detailed livestock management data in the context of assessing the risk of inter-species disease transmission.

Outcrops as guides to subsurface natural fractures: Example from the Nikanassin Formation tight-gas sandstone, Grande Cache, Alberta foothills, Canada

Abstract Outcrop studies are essential for understanding subsurface fractures, because some key attributes such as length and height distribution cannot be measured using wellbores. Discrepancies between outcrop and subsurface fracture attributes arise because loading paths due to burial, exhumation, and thermal paths differ. Consequently, even where rock type and structural setting are close matches, differences may exist in mechanical properties and fracture growth. Here we investigate petrologic criteria and disseminated arrays of quartz-filled microfractures as tools for comparing and contrasting fractures in outcrop with those as sampled by core for tight gas sandstones. Fracture cements are key diagnostic criteria for proving correspondence between outcrop and core. We offer guidelines on selecting suitable outcrop analogs that differ markedly from current practice. Our illustration uses outcrops and core samples of Late Jurassic to Early Cretaceous Nikanassin Formation, a tight gas sandstone, but aspects of the outcrop vetting procedure can be applied to other rock types. In some core and outcrops, Nikanassin Formation fractures contain quartz and ankerite cement assemblages, crack-seal and rind textures, and aperture size distributions that show that the outcrop and subsurface localities we examined share the same fracture stratigraphy and similar diagenesis. These outcrops can thus be used to measure attributes including those that are unlikely to be captured in core, such as fracture height and length distributions, relative and absolute fracture intensity with structural position, and degree of fill by synkinematic cement. In our example, absolute fracture intensity and distribution of postkinematic carbonate cements are site specific and differ between outcrop and core, but in ways that can be quantified.

The role of mechanical stratigraphy in the lateral variations of thrust development along the central Alberta Foothills, Canada

Fold-thrust belts generally exhibit significant variations in structural styles such as differences in thrust geometries and frequencies in imbrication. A natural laboratory of this pattern is preserved in the central Alberta Foothills of the Canadian Rockies, where differences in thrust geometries are represented by the existence vs. non-existence of triangle zones. To seek the factors that make this difference in these regions in terms of structural geometry, stratigraphic thickness variations and mechanical stratigraphy of the sedimentary layers, structural interpretation is conducted based on admissible cross-sections and well log interpretations. In northern region, a backthrust is detached from an incompetent layer (viz. Nomad Unit of the Wapiabi Formation), which gets thinner from the Foothills to the Plains, indicating that it is developed where the shale layers are pinched out where triangle zone is developed. Backthrust is also developed in the southern region, where mechanical strengths of strata (viz. Bearpaw Formation) increase toward the foreland. In the central region, however, only forethrusts are developed along the weak continuous decollement layers (viz. Turner Valley and Brazeau formations), forming an imbricate fan without development of the triangle zone. Incompetent layers such as the top Wapiabi (Nomad), Brazeau (Bearpaw), Coalspur and Paskapoo formations are also pinched out laterally, forming fault glide horizons in different stratigraphic levels in each region. These results indicate that, along the transport direction, triangle zone is developed in relation to the stratigraphic pinch out of the Nomad Unit in the northern region, and is formed associated with the variations in strengths of the layers constituting the Bearpaw Formation in the southern region. It is notable that all the glide horizons are developed along incompetent layers. However, triangle zones are not developed in the areas of continuous stratigraphy of the Nomad Unit, which does not serve as a glide horizon in the central region. This suggests that factors such as stratigraphic thickness changes of incompetent layers and mechanical stratigraphy of the sedimentary layers play an important role in the development of lateral variations in thrust system evolution in terms of triangle zone vs. imbricate fan in the central Alberta Foothills.

Spatial Heterogeneity of the Forest Canopy Scales with the Heterogeneity of an Understory Shrub Based on Fractal Analysis

Spatial heterogeneity of vegetation is an important landscape characteristic, but is difficult to assess due to scale-dependence. Here we examine how spatial patterns in the forest canopy affect those of understory plants, using the shrub Canada buffaloberry (Shepherdia canadensis (L.) Nutt.) as a focal species. Evergreen and deciduous forest canopy and buffaloberry shrub presence were measured with line-intercept sampling along ten 2-km transects in the Rocky Mountain foothills of west-central Alberta, Canada. Relationships between overstory canopy and understory buffaloberry presence were assessed for scales ranging from 2 m to 502 m. Fractal dimensions of both canopy and buffaloberry were estimated and then related using box-counting methods to evaluate spatial heterogeneity based on patch distribution and abundance. Effects of canopy presence on buffaloberry were scale-dependent, with shrub presence negatively related to evergreen canopy cover and positively related to deciduous cover. The effect of evergreen canopy was significant at a local scale between 2 m and 42 m, while that of deciduous canopy was significant at a meso-scale between 150 m and 358 m. Fractal analysis indicated that buffaloberry heterogeneity positively scaled with evergreen canopy heterogeneity, but was unrelated to that of deciduous canopy. This study demonstrates that evergreen canopy cover is a determinant of buffaloberry heterogeneity, highlighting the importance of spatial scale and canopy composition in understanding canopy-understory relationships.

Limited effects of non-native trout on microcrustacean zooplankton in boreal foothills lakes: comparisons of stocked, unstocked, and fishless lakes

Stocking lakes with trout can have strong effects on native communities; however, the nature of impacts is not universal across receiving ecosystems. To assess effects of non-native trout, relative to native small-bodied fish, on microcrustacean zooplankton, we compared stocked, unstocked (but fish-bearing), and fishless lakes in the boreal foothills of Alberta, Canada. Relative to unstocked lakes, stocked lakes had greater richness, but otherwise showed few additional effects on microcrustacean communities. In contrast, fishless lakes supported lower abundances of Cladocera, Calanoida, and Cyclopoida, but were dominated by larger cladoceran and calanoid taxa, compared with fish-bearing lakes (stocked and unstocked). Vertical distributions also differed significantly among lake types; microcrustaceans had far higher relative abundances at 1 m than at 2 m in fishless lakes compared with fish-bearing lakes (distributions in stocked and unstocked lakes were similar). Microcrustacean communities in fishless lakes were likely shaped by the invertebrate planktivore Chaoborus, which was abundant in these systems, whereas native fishes likely structured microcrustacean communities prior to trout introductions, with planktivory by trout causing few additional effects.

Chemical, Physical, and Biological Factors Shape Littoral Invertebrate Community Structure in Coal-Mining End-Pit Lakes.

Aquatic invertebrates form the base of the consumer food web in lakes. In coal-mining end-pit lakes, invertebrates are exposed to an environment with potentially challenging physical and chemical features. We hypothesized that the physical and chemical features of end-pit lakes reduce critical littoral habitat and thus reduce invertebrate diversity, thereby limiting the potential for these lakes to be naturalized. We used a multivariate approach using principle component analysis and redundancy analysis to study relationships between invertebrate community structure, habitat features, and water quality in five end-pit lakes and five natural lakes in the Rocky Mountain foothills of west-central Alberta, Canada. Results show a significantly different invertebrate community structure was present in end-pit lakes as compared with reference lakes in the same region, which could be accounted for by water hardness, conductivity, slope of the littoral zone, and phosphorus concentrations. Habitat diversity in end-pit lakes was also limited, cover provided by macrophytes was scarce, and basin slopes were significantly steeper in pit lakes. Although water chemistry is currently the strongest influencing factor on the invertebrate community, physical challenges of habitat homogeneity and steep slopes in the littoral zones were identified as major drivers of invertebrate community structure. The addition of floating wetlands to the littoral zone of existing pit lakes can add habitat complexity without the need for large-scale alterations to basing morphology, while impermeable capping of waste-rock and the inclusion of littoral habitat in the planning process of new pit lakes can improve the success of integrating new pit lakes into the landscape.

Fine-scale assessment of genetic diversity of trembling aspen in northwestern North America.

BackgroundIn North America, the last ice age is the most recent event with severe consequences on boreal species’ ranges. Phylogeographic patterns of range expansion in trembling aspen (Populus tremuloides) suggested that Beringia is likely to be a refugium and the “ice-free corridor” in Alberta may represent a region where small populations persisted during the last glacial maximum (LGM). The purpose of this study was to ascertain whether the origins of trembling aspen in western North America are reflected in the patterns of neutral genetic diversity and population structure. A total of 28 sites were sampled covering the northwestern part of aspen’s distribution, from Saskatchewan to Alaska. Twelve microsatellite markers were used to describe patterns of genetic diversity. The genetic structure of trembling aspen populations was assessed by using multivariate analyses, Mantel correlograms, neighbor-joining trees and Bayesian analysis.ResultsMicrosatellite markers revealed little to no neutral genetic structure of P. tremuloides populations in northwestern North America. Low differentiation among populations and small isolation by distance (IBD) were observed. The most probable number of clusters detected by STRUCTURE was K = 3 (∆K = 5.9). The individuals in the populations of the 3 clusters share a common gene pool and showed a high level of admixture. No evidence was found that either Beringia or the “ice-free corridor” were refugia. Highest allelic richness (AR) and lowest heterozygosity (Ho) were observed in Alberta foothills of the Rocky Mountains.ConclusionsContrary to our hypothesis, our results showed that microsatellite markers revealed little to no genetic structure in P. tremuloides populations. Consequently, no divergent populations were observed near supposed refugia. The lack of detectable refugia in Beringia and in the “ice-free corridor” was due to high levels of gene flow between trembling apsen populations. More favorable environmental conditions for sexual reproduction and successful trembling aspen seedling establishment may have contributed to increase allelic richness through recombination in populations from the Albertan foothills of the Rocky Mountains.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0810-1) contains supplementary material, which is available to authorized users.

Predictive modelling of ecological patterns along linear‐feature networks

Summary Ecological patterns and processes often take place within linear‐feature networks, and this has implications when analysing the spatial configuration of such patterns or processes across a landscape. One such pattern is the use of landscapes by human recreationists: an important variable in animal habitat selection and behaviour. Due to the difficulty in obtaining data, ecologists tend to use coarse metrics such as linear‐feature density, while the extent and timing of human activity are often ignored. Remote detector equipment and its increasing use in ecological studies allow for large volumes of data on human activity to be collected. However, the analysis of these data still can be challenging. Using a combination of generalised linear mixed‐effects models and network‐based ordinary kriging, we developed a method for estimating spatial and temporal variations in motorised and non‐motorised activities across a complex linear‐feature network. Trail cameras were set up between 2012 and 2014 and monitored motorised and non‐motorised activities at 238 different trail sites across a 2824 km2 region of the eastern slopes and foothills of central Alberta's Rocky Mountains. We evaluate the predictive capacity of this approach, demonstrate its application and discuss its merits and limitations. This method offers a straightforward analysis that can be applied to remotely acquired data to give a useful metric for assessing wildlife responses to human activity, and has potential application beyond the highlighted example.

Fracture system evolution within the Cardium sandstone, central Alberta Foothills folds

The natural fracture system developed in the Cardium sandstone is examined in four outcropping structures that represent different stages of fold development. At the incipient stage of folding, the fracture system is dominated by large, widely spaced hybrid fractures that have very small displacements and are aligned in the regional shortening direction (type I orientation). These fractures are naturally propped open by asperities along the fracture surfaces. A lesser number of small thrust faults (type III orientation) are also developed. Extension fractures aligned parallel to the fold axis (type II orientation) begin to develop in the early stage of folding. Through the intermediate stage of folding, there is a progressive increase in the intensity of both type I and type II orientation fractures. Incremental increases in shear displacement on new or reactivated fractures create a gouge of comminuted sandstone grains along the fracture interface. As folding progresses to an advanced stage, there is major increase in the amount of shear displacement on both type I and type II orientation fractures. Many existing fractures coalesce into connected fracture zones and small faults that have shear offsets ranging from several centimeters to several meters. A breccia can result from intense fracturing in the rock within and marginal to these shear features. Slickensides on type I orientation features consistently indicate slip in a subhorizontal direction, even as bed dip increases. Multiple slickenside patterns record reactivation of these features. Type II orientation fractures and small faults consistently undergo bed-perpendicular slip. Type I and type II features both serve to stretch the Cardium sandstone beds but in different directions. Only type III features, which are a minor component of the fracture population, result in bed thickening.

Fracture abundance and strain in folded Cardium Formation, Red Deer River anticline, Alberta Foothills, Canada

The folded and thrusted Mesozoic clastic sequence of the Canadian Rocky Mountain foothills forms important hydrocarbon reservoirs; however, the generation of fractures and their timing relative to folding and thrusting have remained unclear. Understanding the distribution and evolution of natural fractures, especially their timing of formation relative to the evolution of the fold-and-thrust system, could potentially improve exploration and development outcomes in these otherwise tight, low-permeability reservoirs. We investigated the relation between folding and fracture formation in the Upper Cretaceous Cardium Formation by combining field structural observations and kinematic modeling of the fold-and-thrust belt evolution. We evaluated the effects of structural position and strain on the formation of predominantly opening-mode fractures by analyzing fracture intensity and aperture in the backlimb, the shallow forelimb close to the crest, and the steep forelimb, away from the crest of a reservoir-scale anticline, the Red Deer River anticline. Fracture strain determined from both outcrop and microscanlines varies little across the three structural domains of the fold, although somewhat lower fracture strain was measured in the forelimb close to the crest. These fracture strain measurements are qualitatively consistent with calculated horizontal strain in the tectonic-transport direction obtained from kinematic numerical models that simulate fold development associated with slip along the underlying Burnt Timber thrust. The kinematic models predict similar magnitudes of horizontal extension in both the back and forelimbs, and somewhat lower extension in the upper forelimb during early development of the Red Deer River anticline. Predicted early fracture formation during fold development is consistent with field structural observations of shear reactivation during later stages of folding. This combined kinematic modeling and field structural study demonstrates that deforming fold-and-thrust belts can undergo a complex evolution of bed-parallel extension in both space and time, resulting in spatially variable fracture formation in structurally complex subsurface reservoirs.

"This Is My Prairie": Corb Lund and the Albertan Fossil Fuel Energy Debate

At the 2010 awards ceremony of the Canadian Country music Association, altcountry artist Corb lund closed the evening’s show with a stirring rendition of “This is my prairie” (2009), a song that addresses the impact of Alberta’s everexpanding energy industry on small and familyowned ranching operations. inspired by his mother’s fight to keep coal bed methane projects from drilling into their family’s ranch in the foothills of southern Alberta, lund’s song relays a young man’s struggle to defend his family’s ranch from development and boldly warns the fossil fuel industry that he will protect his homeland at all costs:

Quartz c-axis orientation patterns in fracture cement as a measure of fracture opening rate and a validation tool for fracture pattern models

We evaluate a published model for crystal growth patterns in quartz cement in sandstone fractures by comparing crystal fracture-spanning predictions to quartz c-axis orientation distributions measured by electron backscatter diffraction (EBSD) of spanning quartz deposits. Samples from eight subvertical opening-mode fractures in four sandstone formations, the Jurassic–Cretaceous Nikanassin Formation, northwestern Alberta Foothills (Canada), Cretaceous Mesaverde Group (USA; Cozzette Sandstone Member of the Iles Formation), Piceance Basin, Colorado (USA), and upper Jurassic–lower Cretaceous Cotton Valley Group (Taylor sandstone) and overlying Travis Peak Formation, east Texas, have similar quartzose composition and grain size but contain fractures with different temperature histories and opening rates based on fluid inclusion assemblages and burial history. Spherical statistical analysis shows that, in agreement with model predictions, bridging crystals have a preferred orientation with c-axis orientations at a high angle to fracture walls. The second form of validation is for spanning potential that depends on the size of cut substrate grains. Using measured cut substrate grain sizes and c-axis orientations of spanning bridges, we calculated the required orientation for the smallest cut grain to span the maximum gap size and the required orientation of the crystal with the least spanning potential to form overgrowths that span across maximum measured gap sizes. We find that within a 10° error all spanning crystals conform to model predictions. Using crystals with the lowest spanning potential based on crystallographic orientation (c-axis parallel to fracture wall) and a temperature range for fracture opening measured from fluid inclusion assemblages, we calculate maximum fracture opening rates that allow crystals to span. These rates are comparable to those derived independently from fracture temperature histories based on burial history and multiple sequential fluid inclusion assemblages. Results support the R. Lander and S. Laubach model, which predicts that for quartz deposited synchronously with fracture opening, spanning potential, or likelihood of quartz deposits that are thick enough to span between fracture walls, depends on temperature history, fracture opening rate, size of opening increments, and size, mineralogy, and crystallographic orientation of substrates in the fracture wall (transected grains). Results suggest that EBSD maps, which can be more rapidly acquired than measurement of tens to hundreds of fluid inclusion assemblages, can provide a useful measure of relative opening rates within populations of quartz-filled fractures formed under sedimentary basin conditions. Such data are useful for evaluating fracture pattern development models.

Assessing the vulnerability of rare plants using climate change velocity, habitat connectivity, and dispersal ability: a case study in Alberta, Canada

Climate change generally requires species to migrate northward or to higher elevation to maintain constant climate conditions, but migration requirement and migration capacity of individual species can vary greatly. Individual populations of species occupy different positions in the landscape that determine their required range shift to maintain similar climate, and likewise the migration capacity depends on habitat connectivity. Here, we demonstrate an approach to quantifying species vulnerabilities to climate change for 419 rare vascular plants in Alberta, Canada, based on a multivariate velocity of climate change metric, local habitat fragmentation, and migration capacity. Climate change velocities indicated that future migration requirements ranged from 1 to 5 km/year in topographically complex landscapes, such as the Alberta Foothills and Rocky Mountains. In contrast, migration requirements to maintain constant climate in relatively flat Boreal Plains, Parkland, and Grassland ranged from 4 to 8 km/year. Habitat fragmentation was also highest in these flat regions, particularly the Parkland Natural Region. Of the 419 rare vascular plants assessed, 36 were globally threatened (G1–G3 ranking). Three globally threatened species were ranked as extremely vulnerable and five species as highly vulnerable to the interactions among climate change velocity, habitat fragmentation, and migration capacity. Incorporating dispersal characteristics and habitat fragmentation with local patterns in climate change velocity improves the assessment of climate change threats to species and may be applied to guide monitoring efforts or conservation actions.

Short-term effects of mastication on fuel moisture and thermal regime of boreal fuel beds

Mechanical mastication is becoming a common fuel management treatment to reduce vertical fuel connectivity, as well as crown fire initiation and potential fire-line intensity, but the moisture dynamics of these novel fuel types have been largely unstudied. We recorded concurrent in situ meteorological observations with moisture and temperature profiles (at depths of 5 and 13 cm) for masticated fuel beds in three treatments in a lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) – black spruce (Picea mariana (Mill.) B.S.P.) boreal stand located in the Upper Foothills of west-central Alberta. Mulch at the 5 cm depth remained at or near 100% moisture content for a majority of the observation period within the treatment that lacked any residual canopy cover. Only during a 10-day rain-free period was substantial drying observed at a depth of 5 cm. At the interface with the underlying duff layer, mulch remained at upwards of 150% moisture content. Drying was typically <10% of potential evaporation rates, except on days after rain, when drying equal to 25%–100% of potential evaporation was observed. Thermal properties of the mulch showed approximately five times the thermal diffusivity of soils, but less than a fuel crib, suggesting that masticated fuel beds have a thermal and moisture regime more similar to soils than fuel cribs, with a diffusion-dominated regime enhanced by minor advection. Low moisture movement observed from depth to the surface promoted highly variable surface moisture that created surface mulch with temperatures far in excess of air temperatures during periods of full sun. Such excess temperatures are shown to be an efficient indicator of surface dryness and high ignition probability.

A discussion of best management practices for reforestation following harvesting of lodgepole pine in the Alberta Foothills

A group of 28 knowledgeable Alberta forest managers, silviculture practitioners and forestry specialists met in 2013 to discuss results of a collaborative field trial and related studies of lodgepole pine regeneration, and their implications for reforestation practice in the Alberta Foothills region. Several areas of practice were discussed, including site preparation, plantation establishment, vegetation management and pest management. Observations and recommendations of the group are summarized. Recommendations for best management practices represent the consensus of the group, and provide a timely assessment of considerations and options for reforestation management in a changing environment.

Uniform versus asymmetric shading mediates crown recession in conifers.

In this study we explore the impact of asymmetrical vs. uniform crown shading on the mortality and growth of upper and lower branches within tree crowns, for two conifer species: shade intolerant lodgepole pine (Pinus contorta) and shade tolerant white spruce (Picea glauca). We also explore xylem hydraulics, foliar nutrition, and carbohydrate status as drivers for growth and expansion of the lower and upper branches in various types of shading. This study was conducted over a two-year period across 10 regenerating forest sites dominated by lodgepole pine and white spruce, in the lower foothills of Alberta, Canada. Trees were assigned to one of four shading treatments: (1), complete uniform shading of the entire tree, (2) light asymmetric shading where the lower 1/4–1/3 of the tree crown was shaded, (3) heavy asymmetric shading as in (2) except with greater light reduction and (4) control in which no artificial shading occurred and most of the entire crown was exposed to full light. Asymmetrical shading of only the lower crown had a larger negative impact on the bud expansion and growth than did uniform shading, and the effect was stronger in pine relative to spruce. In addition, lower branches in pine also had lower carbon reserves, and reduced xylem-area specific conductivity compared to spruce. For both species, but particularly the pine, the needles of lower branches tended to store less C than upper branches in the asymmetric shade, which could suggest a movement of reserves away from the lower branches. The implications of these findings correspond with the inherent shade tolerance and self-pruning behavior of these conifers and supports a carbon based mechanism for branch mortality – mediated by an asymmetry in light exposure of the crown.