Natural Resources Canada

Accurate prediction of solubility of polymers in solvents a priori is highly desirable in practice. To this end, the Flory-Huggins interaction parameter χ is commonly used and molecular dynamics simulation, a powerful computational tool, has been used for such a purpose. To calculate χ, there exist three possible strategies using molecular dynamics simulation. One is through the calculation of Hildebrand solubility parameters of the pure components while the other two are to calculate the enthalpy of solvation and Gibbs free energy of solvation for the solution, respectively. This study evaluated these three strategies using binary solutions containing a hydrophobic or hydrophilic polymer (polyisobutylene, polystyrene, cis and trans polybutadiene, cis and trans polyisoprene, poly(ethylene oxide), and polyacrylamide) and an aliphatic solvent-cyclohexane. We found that χ determined via solubility parameters predicted the solubility trend but deviated significantly from experimental values. On the other hand, the enthalpy of solvation approach provided the most accurate χ values, compared to experiment, at a reasonable computational demand, especially for hydrocarbon polymers, while the Gibbs free energy of solvation approach, though more computationally intensive, did not significantly improve χ from the enthalpy of solvation approach. In particular, the Gibbs free energy of solvation approach overestimated χ for non-polar polymers. A conformational analysis of the solvated polymers revealed that all polymers collapsed in cyclohexane with polyethylene oxide and polyacrylamide collapsed the most as expected. For the two polar polymers used, the collapse was evidenced by abrupt changes in radius of gyration (Rg) and solvent accessible surface area (SASA) in the early stage of molecular dynamics simulation trajectories, and plateauing at much lower final values. Conversely, the hydrocarbon polymers exhibited minimal deviation from the expected Rg and barely any change in SASA with time. Our findings demonstrated that there exist differences in the accuracy and computational resources used when different molecular dynamics simulation strategies are used in the determination of χ.

Indigenous peoples are widely affected by natural hazards and their history and knowledge can directly inform on past events and mitigation strategies. Here we show how effective co-creation of resources and bi-lateral knowledge exchange between natural hazard researchers and local Indigenous communities provides an effective, equitable, and sustainable way to conduct research.

Freshwater drum Aplodinotus grunniens are a unique and ubiquitous freshwater species of the family Sciaenidae. Despite the species’ wide distribution and unique biogeography, life history, and behavior, surprisingly little is known about freshwater drum movement ecology. In this study, we use passive acoustic telemetry tags and a broad-scale gridded receiver array to track the interannual and seasonal movement of freshwater drum tagged in tributaries of the North and South Basins of Lake Winnipeg (Manitoba, Canada). First, tagged freshwater drum had lower survival in the south basin where higher fishing pressure is thought to be a cause of mortality. We found that freshwater drum in Lake Winnipeg are remarkably mobile, with mean monthly movement rates among the highest on record for any freshwater fish. In the spring, fish entered rivers prior to spawning. A few weeks later, most individuals moved into lake habitat where they made extensive lateral movements. Home range and hotspot analysis revealed seasonal and population-specific patterns of occupancy, with elevated densities in lake habitat during the ice-on period and dispersed distributions during open water. Both populations remained almost exclusively in their respective rivers and basins. Homing and site fidelity were apparent, with nearly all fish returning to their original tagging river during each successive spawning season. The results bolster the existing information on freshwater drum movement ecology and may help enhance conservation and management strategies, particularly toward addressing commercial bycatch.

The Canadian Arctic is a large and diverse geographic area that encompasses a wide variety of environmental conditions and ecosystems. Over recent decades, marine transportation has increased across the Arctic and, as a result, so has the likelihood of an oil spill. The study of oil spills in the Arctic presents unique challenges compared to temperate marine environments, due to remoteness, cold temperatures and the presence of snow and ice throughout much of the year. This review summarizes and discusses the fate of oil in the Canadian Arctic. A brief introduction to the Canadian Arctic and sources of potential petroleum spills is provided, followed by discussions of the behaviour of oil in ice and freezing temperatures, oil-sediment interactions, and the weathering and natural remediation of oil under Arctic conditions. A summary of perspectives concludes the review, with emphasis on possible areas of future work to address research gaps.

Diamond exploration on the Melville Peninsula has uncovered a slew of Neoproterozoic to Cambrian aged kimberlites and related magmas. Drilling by North Arrow Minerals Inc. in 2018 at the Mel property, located 100 km southwest of Hal Beach, Nunavut, Canada, delineated dikes and sills, logged as kimberlite. Phlogopite, ilmenite, and spinel compositions and whole-rock major and trace element abundances indicate that the Mel dikes are archetypal kimberlites. A Rb-Sr isochron for phlogopite yielded 555.6 ± 2.7 Ma, interpreted as the age of emplacement of the Mel kimberlites, with an initial ⁸⁷Sr/⁸⁶Srinitial ratio of 0.7044. This age is similar to other Neoproterozoic to Cambrian kimberlites and related magmas, interpreted to be related to the latter stages of the breakup of Rodinia and the opening of the Iapetus Ocean. Whole-rock Mel kimberlites have ⁸⁷Sr/⁸⁶Srinitial (0.7054 to 0.7069), εNdinitial (2.4 to 3.0), and εHfinitial (− 15.4 to -1.1) ratios, with the isotopic characteristics of the least contaminated rocks being similar to those of Eoarchean to Cambrian kimberlites in eastern Canada. The compositions of most of the garnets separated from the Mel kimberlites are consistent with a lherzolitic paragenesis, with a subordinate portion having an eclogitic paragenesis. Ni-thermometry results for the lherzolitic garnets record mantle temperatures of 800 °C to 1325 °C. Extrapolation of these temperatures to the West Central Rae geotherm indicates that the lherzolite garnets were derived from depths between 105 and 185 km, with 86% of all investigated garnet grains having an origin within the diamond stability field.

In conservation strategies, getting precise and repeatable information on the species’ diet and health without relying on invasive or laborious methods is challenging. Here, we developed an efficient and non-invasive workflow for the sequencing and analysis of four taxonomic markers from fecal DNA to characterize the gut microbiota, parasites, and plants and lichens composing the winter diet of caribou (Rangifer tarandus), Canada’s most iconic endangered species. Sequencing of the 18S rRNA gene of eukaryotes from seven locations in Manitoba and Saskatchewan, Canada, allowed for the detection of five genera of parasites in caribou feces (including Nematodirella and Parelaphostrongylus) with variable frequency of occurrence depending on sampling location and sex. Our workflow also revealed a rich winter plant and lichen diet in caribou, with respectively 29 and 18 genera identified across all samples through plant and fungal ITS2 sequencing. Relationships between the gut microbiota and both the diet and parasite richness were also identified. Of note, the Central Saskatchewan sampling location was characterized by a clearly distinct gut microbiota which could be linked to an epiphytic lichen-rich diet. Overall, our results showed the potential of this multi-marker DNA metabarcoding workflow as an efficient tool to provide insights into the species biology and ecology.

Differentially mapping snow depth in mountain watersheds from airborne laser altimetry is a valuable hydrologic technique that has seen an expanded use in recent years. Additionally, lidar systems also record the strength of the returned light pulse (i.e. intensity), which can be used to characterize snow surface properties. For near-infrared lidar systems, return intensity is relatively high over snow and inversely related to the effective grain size, a primary control on snow albedo. Raw intensity is also sensitive to laser range and incidence angle, however, and requires a correction for snow property retrieval that is especially pertinent in mountainous terrain. Here, we describe a workflow to correct the intensity using the plane trajectory, lidar scan angle, and lidar-derived topography. As a proof of concept for snow retrievals, we apply the workflow to an airborne 1064 nm lidar flight over a snow-covered mountain basin in the Colorado Rockies. Corrected intensity was empirically related to reflectance before delineating snow extent and retrieving grain size. Relative to the traditional snow classification derived from optical imagery, the lidar-derived snow extent covered 5.4% more area due to the fine resolution point cloud and absence of shadows common in optical imagery. The lidar-derived grain size retrievals had a MAE of 32 µm compared to those from field spectroscopy, which translated to a 1% error in snow albedo. We found high incidence angles yielded an overcorrection in intensity that introduced a high bias in the grain size distribution and, therefore, suggest using an incidence angle threshold (40°). Developing methods specifically for quantitative snow surface property retrievals from lidar intensity is timely and relevant as aerial lidar is increasingly being used to map snow depth for hydrologic and cryospheric studies.

Water‐use efficiency (WUE) is affected by multiple leaf traits, including stomatal morphology. However, the impact of stomatal morphology on WUE across different ontogenetic stages of tree species is not well‐documented. Here, we investigated the relationship between stomatal morphology, intrinsic water‐use efficiency (iWUE) and leaf carbon isotope ratio (δ ¹³ C). We sampled 190 individuals, including juvenile and mature trees belonging to 18 temperate broadleaved tree species and 9 genera. We measured guard cell length (GCL), stomatal density (SD), specific leaf area (SLA), iWUE and bulk leaf δ ¹³ C as a proxy for long‐term WUE. Leaf δ ¹³ C correlated positively with iWUE across species in both juvenile and mature trees, while GCL showed a negative and SD a positive effect on iWUE and leaf δ ¹³ C. Within species, however, only GCL was significantly associated with iWUE and leaf δ ¹³ C. SLA had a minor negative influence on iWUE and leaf δ ¹³ C, but this effect was inconsistent between juvenile and mature trees. We conclude that GCL and SD can be considered functional morphological traits related to the iWUE and leaf δ ¹³ C of trees, highlighting their potential for rapid phenotyping approaches in ecological studies.

Background tree mortality can be defined as the death of trees that naturally occurs as stands develop, in the absence of major or sudden stand disturbances. The phenomenon is often linked to ontogeny and competition and generally affects individual trees, unlike catastrophic mortality, which affects most trees in the stand. To forecast stand characteristics and to estimate how stand development could change in response to changing climate, it is necessary to quantify background mortality and to identify the most important factors involved. Using data from 10,045 permanent sample plots, we modeled background tree mortality for the 9 most abundant tree species of the eastern Canadian boreal forest. We used explanatory variables related to stand and tree ontogeny, competition, site characteristics and climate to calibrate the models. We found that an increase in age, competition and the presence of partial cut increased the mortality risk. However, the effect of DBH and site-related variables varied among species. We also found that higher temperatures, less precipitation, and higher aridity index values increased background tree mortality. According to mortality simulations under different future climate scenarios, background tree mortality could increase in the next decades for 6 of the 9 tree species studied.

This article summarizes a ten-year plan for forest carbon science that was developed in a collaborative effort with the forest carbon science and policy community in Canada. Building on the research progress since the first plan, the updated Blueprint outlines key priorities, goals, and visions for forest carbon research over the next decade. Here we describe the five essential research areas, namely: A) understanding human impacts on forest carbon; B) exploring foundational forest carbon dynamics; C) assessing climate change mitigation strategies; D) promoting reconciliation and including Indigenous Knowledges in meaningful and authentic ways; and E) contextualizing carbon within the broad range of forest values. The Blueprint serves as a guide for the development of research supporting policies that continue to foster sustainable forest management and maintain and enhance collaborative carbon research in Canada.

The invisible-gold deposits known as Carlin-type are becoming more important as easier to find deposits are progressively depleted. The combination of the invisible nature of the Au in these deposits, as well as the limited surface indicators of these deposits, makes exploration to find new Carlin-type deposits extremely difficult. Comprehensive mineralization models are essential to find new Carlin-type deposits in similar geologic settings. The Nadaleen Trend of Yukon, Canada, is one such district where an improved understanding of this deposit type has led to new discoveries. Previous studies compared and contrasted the tectonic setting, host rock depositional setting, structural preparation, and mineralization style of the Nadaleen Trend with those in Carlin-type localities, Nevada. However, the comparisons at an atomic scale, between Carlin-type Au deposits in the Nadaleen Trend and those in Nevada, has yet to be investigated. This study fills this knowledge gap by combining high resolution microanalytical techniques with atom probe tomography to examine the distribution of Au and other trace elements in the Nadaleen Trend, compare them to a representative Carlin-type deposit in Nevada (Turquoise Ridge), and determine how widespread the mineralization model is. Our findings show that in the Nadaleen Trend, as in Nevada, Au is generally directly linked with As at the macro to atomic scale, and is incorporated into As/Au rich overgrowths on sedimentary/diagenetic pyrite. Gold-rich pyrite rims in the Nadaleen Trend are generally smaller than those found in Nevada (0.5–2 µm vs > 10 µm), although the ore grades appear comparable. We find that the Au in the pyrite of the Nadaleen Trend is homogenously distributed (i.e. lattice bound) at the atomic scale, but that there is a notable enrichment of As surrounding individual Au atoms. These findings are in agreement with those from previous work on a representative deposit in Nevada, and support the assertation that As is the key ingredient in facilitating the incorporation of Au into the pyrite lattice. Arsenic as an essential component in the trapping mechanisms of Au in CTG deposits, is something that has been as to yet underappreciated in the current models of CTG deposit formation.

Globally, managing wildland fire is increasing in complexity. Satellite Earth Observation (EO) data, specifically active fire ‘hotspot’ data, is often used to inform wildland fire management. This study explores hotspot data usage via web traffic data (‘user counts’) for the FIRMS, GWIS and EFFIS web portals between September 2019 and April 2023. Global active fire data use is characterized by multi-month periods of relatively low, stable user counts, interspersed with periodic spikes (4.1x median monthly activity) of activity broadly aligned with the North American / European fire season (late summer-fall). Users from the Americas (45%) and Europe (36%) dominate web traffic. We also examined correlative relationships between web page user counts and environmental and social variables at multiple spatial scales. Globally, the strongest relationships were found between user counts and the total number of fires, total burned area, number of fire disaster events; country population levels and internet proliferation. Notably, at a country level, the strongest (and weakest) relationships between weekly user counts and fire activity were found in a diverse range of countries suggesting that a variety of hotspot data use situations exist and further investigation is needed to better understand EO active fire data usage.

With ongoing global warming, increasing water deficits promote physiological stress on forest ecosystems with negative impacts on tree growth, vitality, and survival. How individual tree species will react to increased drought stress is therefore a key research question to address for carbon accounting and the development of climate change mitigation strategies. Recent tree‐ring studies have shown that trees at higher latitudes will benefit from warmer temperatures, yet this is likely highly species‐dependent and less well‐known for more temperate tree species. Using a unique pan‐European tree‐ring network of 26,430 European beech ( Fagus sylvatica L. ) trees from 2118 sites, we applied a linear mixed‐effects modeling framework to (i) explain variation in climate‐dependent growth and (ii) project growth for the near future (2021–2050) across the entire distribution of beech. We modeled the spatial pattern of radial growth responses to annually varying climate as a function of mean climate conditions (mean annual temperature, mean annual climatic water balance, and continentality). Over the calibration period (1952–2011), the model yielded high regional explanatory power ( R ² = 0.38–0.72). Considering a moderate climate change scenario (CMIP6 SSP2‐4.5), beech growth is projected to decrease in the future across most of its distribution range. In particular, projected growth decreases by 12%–18% (interquartile range) in northwestern Central Europe and by 11%–21% in the Mediterranean region. In contrast, climate‐driven growth increases are limited to around 13% of the current occurrence, where the historical mean annual temperature was below ~6°C. More specifically, the model predicts a 3%–24% growth increase in the high‐elevation clusters of the Alps and Carpathian Arc. Notably, we find little potential for future growth increases (−10 to +2%) at the poleward leading edge in southern Scandinavia. Because in this region beech growth is found to be primarily water‐limited, a northward shift in its distributional range will be constrained by water availability.

Melampsora medusae f. sp. tremuloidae is a quarantine organism for the EU. In North America, this fungus causes rust disease on Populus tremuloides. In Europe, Populus tremula, an aspen closely related to P. tremuloides, is widespread and plays an important ecological role. Introduction of M. medusae f. sp. tremuloidae into Europe could be a major risk if this forma specialis could evolve and become virulent on P. tremula. To date no PCR-based assay exists to specifically detect M. medusae f. sp. tremuloidae. In this study, a sensitive and specific real-time PCR assay has been developed based on the 28S rDNA. The assay proved to be reliable using many real-time PCR kits and platforms. It can be used to monitor the introduction and the spread of M. medusae f. sp. tremuloidae in the context of phytosanitary regulations.