Rocks, lichens, and woody litter influenced the soil invertebrate density in upland tundra heath.

Soil invertebrates are an integral part of Arctic ecosystems through their roles in the breakdown of litter, soil formation, and nutrient cycling. However, studies examining soil invertebrates in the Arctic are limited and our understanding of the abiotic and biotic drivers of these invertebrate communities remains understudied. We examined differences in soil invertebrate taxa (mites, collembolans, enchytraeids) among several undisturbed upland tundra heath sites in Nunavut Canada and identified the drivers (vegetation and substrate cover, soil nutrients and pH) of the soil invertebrate community across these sites. Soil invertebrate densities were similar to that of other Arctic studies. While invertebrate communities were relatively consistent between our sites, cover of rocks, woody litter, and the lichen Alectoria nigricans had significant, positive influences on the density of all invertebrates studied. Mites and collembolans were more closely associated with cover of lichens, whereas enchytraeids were more closely associated with woody litter and rocks. Our results suggest that anthropogenic (e.g., resource exploration and extraction) and/or natural (e.g., climate change) disturbances that result in changes to the vegetation community and woody litter inputs will likely impact soil invertebrates and the ecosystem services they provide.

Agroecosystem edge effects on vegetation, soil properties, and the soil microbial community in the Canadian prairie.

Edge effects resulting from adjacent land uses are poorly understood in agroecosystems yet understanding above and belowground edge effects is crucial for maintaining ecosystem function. The aim of our study was to examine impacts of land management on aboveground and belowground edge effects, measured by changes in plant community, soil properties, and soil microbial communities across agroecosystem edges. We measured plant composition and biomass, soil properties (total carbon, total nitrogen, pH, nitrate, and ammonium), and soil fungal and bacterial community composition across perennial grassland-annual cropland edges. Edge effects due to land management were detected both aboveground and belowground. The plant community at the edge was distinct from the adjacent land uses, where annual, non-native, plant species were abundant. Soil total nitrogen and carbon significantly decreased across the edge (P < 0.001), with the highest values in the perennial grasslands. Both bacterial and fungal communities were different across the edge with clear changes in fungal communities driven directly and indirectly by land management. A higher abundance of pathogens in the more heavily managed land uses (i.e. crop and edge) was detected. Changes in plant community composition, along with soil carbon and nitrogen also influenced the soil fungal community across these agroecosystems edges. Characterizing edge effects in agroecosystem, especially those associated with soil microbial communities, is an important first step in ensuring soil health and resilience in these managed landscapes.

Environmental Impact of Triclopyr on Habitat Quality in Boreal Rights-of-Way.

The indirect effects of herbicides on habitat quality in boreal ecoregions remain poorly understood. Herbicides are commonly applied on boreal rights-of-way to control vegetation below power lines, where they can indirectly enter the soil ecosystem after leaf abscission. Key soil processes such as litter decomposition and soil nutrient cycling can be influenced by altering litter chemistry and/or impacting decomposer species. Disruption of these soil processes could lead to changes in ecosystem health of boreal systems. The indirect impacts of triclopyr on habitat quality of treated boreal rights-of-way were examined through litter mass loss and quality (carbon-to-nitrogen ratios) and the response of boreal invertebrates (Folsomia candida and Oppia nitens) in microcosms and avoidance tests. Litter breakdown rates were not significantly different within a year of treatment. However, we did observe nitrogen profile differences between field-treated and untreated samples, which likely resulted from triclopyr-induced repression of natural leaf senescence processes. At field application rates, there were no differences in survival and reproduction rates of F. candida, which is key in litter breakdown. The triclopyr concentrations that caused 50% of tested F. candida and O. nitens to avoid treated litter were above field application rates. Therefore, field application rates of triclopyr are not expected to impair habitat quality and ecosystem services of boreal ecoregions based on the parameters we evaluated. Our study improves understanding of the effects of herbicide application on habitat quality and is critical for responsible herbicide use on boreal rights-of-way. Environ Toxicol Chem 2022;41:2955-2967. © 2022 SETAC.

Indigenous community participation in resource development decision-making: Practitioner perceptions of legal and voluntary arrangements.

Indigenous nations worldwide are working with and lobbying private and public resource developers to ensure meaningful engagement in decisions tied to resource development in their territories. The diversity of approaches for engagement can be framed along a continuum, with voluntary practices at one end and legal responsibilities at the other. Given this continuum, the roles and responsibilities of various actors involved have become blurred, which leads to poor practice. In an effort to bring clarity, the aim of this research was to understand the distinctions between voluntary practices and legal responsibilities among key actors, identify how key actors understood their different roles and responsibilities, and explain the implications of these differences. In partnership with a First Nation and a public power utility in Northern Saskatchewan, Canada, we employed semi-structured interviews and group workshops with Indigenous, industry, and government actors who participate in environmental management and resource development decisions. We found that actors had distinct motivations for interacting with one another, that perceptions of voluntary practices and legal responsibilities aligned among some participants but not among others, and that participants were indeed confused about their roles and responsibilities in relation to legal requirements and voluntary engagement activities. Furthermore, we learned that clarifying the intended roles of those involved in resource development decisions would be insufficient for improving practice. This is because improved clarity may not address underlying mistrust of government by Indigenous people, or may not be possible where rights and interests are intertwined under a broad conception of Indigenous rights. Findings also suggest the need for government and industry to work with Indigenous nations as self-determining entities, rather than imposing unilateral processes upon them. Consequently, more serious scrutiny, understanding and action is needed by government and industry when employing and assessing voluntary actions and legal measures for Indigenous inclusion in resource development decision-making processes.

Drift, dissipation and risk to wildlife following targeted herbicide applications on boreal transmission rights-of-way.

Herbicide use on boreal transmission line rights-of-way has been relatively limited compared to more temperate regions and therefore challenges exist in estimating and communicating the associated risks. Herbicides directly enter the ecosystem through deposition on vegetation and soils and can be a vector of contamination to browsing herbivores. Triclopyr drift and foliage concentrations were quantified following basal bark (Garlon RTU) and low-volume foliar (Garlon XRT) field treatments to aspen (Populus tremuloides) saplings and willow (Salix bebbiana) shrubs, respectively. Greater drift concentrations localized at the stem base were observed following basal bark treatments. Conversely, concentrations in foliage following the low-volume foliar treatment (DT50 = 5.7 days and DT90 = 34.6 days) were much higher than following basal bark treatment, which also required two days to translocate into the leaves. However, dissipation was rapid from both application methods and triclopyr in foliage was less than 20 µg g-1 a year following application. A risk assessment revealed an acceptable level of risk for acute toxicity to wildlife browsing on contaminated leaves from the residues detected in this study; however, an unacceptable level of risk for chronic toxicity to long-term browsing moose. Site-specific data regarding browsing behaviour on herbicide treated rights-of-ways and species-specific reference values are needed to improve confidence in the tier-two risk assessment. Basal bark application is ideal when stem density is lower and toxic effects for herbivores is of concern and low-volume foliar applications are best suited in areas with higher stem density when off-target herbicide deposition is less acceptable.

The Charosphere Promotes Mineralization of 13C-Phenanthrene by Psychrotrophic Microorganisms in Greenland Soils.

When soil is frozen, biochar promotes petroleum hydrocarbon (PHC) degradation, yet we still do not understand why. To investigate microbial biodegradation activity under frozen conditions, we placed 60-µm mesh bags containing 6% (v/v) biochar created from fishmeal, bonemeal, bone chip, or wood into PHC-contaminated soil, which was then frozen to -5°C. This created three soil niches: biochar particles, the charosphere (biochar-contiguous soil), and bulk soil outside of the bags. After 90 d, C-phenanthrene mineralization reached 55% in bonemeal biochar and 84% in bone chip biochar charosphere soil, compared with only 43% in bulk soil and 13% in bone chip biochar particles. Soil pH remained near neutral in bone chip and bonemeal biochar treatments, unlike wood biochar, which increased alkalinity and likely made phosphate unavailable for microorganisms. Generally, charosphere soil had higher aromatic degradative gene abundances than bulk soil, but gene abundance was not directly linked to C-phenanthrene mineralization. In bone chip biochar-amended soils, phosphate successfully predicted microbial community composition, and abundances of and increased in charosphere soil. Biochar effects on charosphere soil were dependent on feedstock material and suggest that optimizing the charosphere in bone-derived biochars may increase remediation success in northern regions.

Effects of chemical speciation on the bioaccessibility of zinc in spiked and smelter-affected soils.

Previous studies have suggested that understanding soil metal speciation, rather than relying solely on total metal content, can improve the accuracy and utility of contaminated site risk assessments. Because soil properties and reaction time can alter metal speciation, speciation should influence metal bioaccessibility. For example, under gastrointestinal conditions, it is expected that metal species will differ in bioaccessibility depending on their stability in acidic pH environments. We studied the links between metal speciation and bioaccessibility. A combination of synchrotron-based X-ray diffraction and X-ray absorption near edge structure (XANES) was used to identify the zinc (Zn) speciation in spiked and smelter-affected soils. After conducting in vitro digestion tests on the soil samples, XANES and linear combination fitting were carried out on the residual pellets to identify the species of Zn that remained after digesting the soils in the simulated gastric and duodenal fluids. The metal species that were not present in the residual pellets were inferred to have been dissolved and, thus, more bioaccessible. Sphalerite (ZnS), ZnO, and outer-sphere Zn contributed more to Zn bioaccessibility than franklinite (ZnFe2 O4 ) and Zn incorporated into a hydroxy interlayer mineral (Zn-HIM). The bioaccessibility of Zn-aluminum layered double hydroxides (Zn-Al-LDH) was found to be inversely proportional to its residence time in soil. It was also observed that the relatively high pH of the duodenum favors metal reprecipitation and readsorption, leading to a reduction in bioaccessible metal concentration. These results imply that metal speciation mainly controls metal bioaccessibility. Environ Toxicol Chem 2019;38:448-459. © 2018 SETAC.

Linking Herbicide Dissipation to Soil Ecological Risk along Transmission Rights-of-Way in the Yukon Territory, Canada.

In the Yukon Territory, transmission rights-of-way (ROWs) are managed using brushing and mowing techniques alone. When cut, target species such as Michx. and spp. grow rapidly shortening maintenance cycles. Long-term vegetation control may be improved by integrating herbicide application. However, prior to implementation, the dissipation and toxicity of herbicides in northern latitudes needed to be assessed. The dissipation of Garlon XRT (triclopyr) and Arsenal Powerline (imazapyr) in soils was assessed at five ROW locations representative of the main ecoregion types where ROWs occur within the Yukon Territory. Soils from four sites were collected at 1, 30, and 365 d after treatment to determine persistence of herbicides for each of three application methods (backpack spraying, cut stump, and point injection). Increased sampling intervals were added to better determine the dissipation rate of each herbicide in Yukon Territory soils. Soil dissipation data were linked to a series of standardized toxicity tests, including three soil invertebrates (, , and ). Additionally, the dissipation of both herbicides from the target species L. was assessed at one site. Herbicide residues persisted in soils for longer than 365 d after treatment and longer than 30 d after treatment in . However, concentrations were below the concentration that would affect 25% of the invertebrate species tested. Weight of evidence and toxic exposure ratios were used to characterize the risks associated with herbicide application in northern latitudes and provided both qualitative and quantitative means to communicate the results to the public.

Application Method and Biochar Type Affect Petroleum Hydrocarbon Degradation in Northern Landfarms.

To integrate biochar as a practical and successful remedial amendment at northern landfarms, components of its formulation and application must be optimized for site-specific environmental conditions. Different biochar amendments were applied to petroleum hydrocarbon (PHC)-contaminated soil at two northern field sites (Iqaluit and Whitehorse) and in a laboratory study at -5°C to determine the effects of application method (injection or incorporation) and biochar type (wood, fishmeal, bonemeal, and/or compost) on PHC degradation and associated soil properties. Incorporation decreased F2 (equivalent C-C) and F3 (equivalent C-C) PHC concentrations in soil after 31 d, whereas injection did not decrease PHC concentrations until Day 334. Bonemeal-derived biochar selectively stimulated F3-PHC degradation in frozen soil over 90 d under controlled laboratory conditions. In the field, there was little difference in PHC degradation between biochar types and the fertilizer control. Incorporation also increased NO availability, and in field trials, all biochars increased NO availability relative to the fertilizer control, whereas the effects of biochars on NH and PO were variable. Aromatic functional gene abundance was enhanced when treatments were incorporated, compared with when injected. In field trials, 6% Zakus wood plus fertilizer inhibited aliphatic and aromatic gene abundance. Liquid water content increased in incorporated treatments, specifically those amended with fishmeal biochar. Incorporation was the most successful application method for these northern soils, and although biochar amendments are not clearly effective in reducing PHC concentrations, there is evidence to suggest it can beneficially influence soil properties and PHC degradation under specific environmental conditions.

Herbicide Toxicity Testing with Non-Target Boreal Plants: The Sensitivity of Achillea millefolium L. and Chamerion angustifolium L. to Triclopyr and Imazapyr.

Terrestrial plant toxicity tests were conducted to determine the sensitivity of two boreal plants, yarrow (Achillea millefolium L.) and fireweed (Chamerion angustifolium L.), to the herbicides imazapyr and triclopyr. Both plants are common non-target species on northern powerline rights-of-way where the impacts of proposed herbicide applications are of concern. In the vegetative vigour test, triclopyr foliar spray caused extensive damage to A. millefolium at <50% of the maximum field application rate (inhibition concentration (IC)50 = 1443.8 g a.i. ha-1) and was lethal to C. angustifolium at the lowest dose tested (1210.9 g a.i. ha-1). Both species demonstrated extremely high sensitivity to imazapyr foliar spray: IC50s = 8.29 g a.i. ha-1 and 4.82 g a.i. ha-1 (<1.5% of the maximum field rate). The seedling emergence and seedling growth tests were conducted in the organic horizon of five boreal soils. Few differences in herbicide bioavailability between soils were detected. Triclopyr limited growth of A. millefolium, C. angustifolium and standard test species Calamagrostis canadensis at low levels (most IC50 estimates between 2-20 µg g-1). For imazapyr, IC50 estimates could not be calculated as there was >75% inhibition of endpoints at the lowest doses of ~2 µg g-1. A foliar application of triclopyr or imazapyr for woody species control would likely cause significant damage to boreal non-target plants. The high sensitivity of both species to herbicide residues in soil indicates long term impacts are dependent on herbicide degradation rates in northern conditions. A. millefolium performed well and is recommended for use in toxicity testing relevant to boreal regions.

Petroleum hydrocarbon remediation in frozen soil using a meat and bonemeal biochar plus fertilizer.

Petroleum hydrocarbon (PHC) degradation slows significantly during the winter which substantially increases the time it takes to remediate soil in Arctic landfarms. The aim of this laboratory trial was to assess the potential of a meat and bonemeal (MBM) biochar to stimulate PHC degradation in contaminated soil collected from Iqaluit, Canada. Over 90 days, 3% (w/w) MBM biochar significantly increased F3- (equivalent nC16-C34) PHC degradation rate constants (k) in frozen soils when compared to the fertilizer (urea and monoammonium phosphate) control. Taking into consideration extensive variability within treatments and negative k values, this difference may not reflect significant remediation. Decreasing C17/Pr and C18/Ph ratios in the frozen soil suggest that this reduction is a result of microbial degradation rather than volatilization. Amendment type and application rate affected the immediate abiotic losses of F2 and F3-PHC in sterile soils, with the greatest losses occurring in compost-amended treatments in the first 24 h. In frozen soils, MBM biochar was found to increase liquid water content (θliquid) but not nutrient supply rates. Under frozen but not thawed conditions, genes for aromatic (C2,3O and nahAc) but not aliphatic (alkB) PHC degradation increased over time in both biochar-amended and control treatments but total viable PHC-degrading populations only increased in biochar-amended soils. Based on these results, it is possible that PHC degradation in biochar-amended soils is active and even enhanced under frozen conditions, but further investigation is required.

Bryophyte responses to microclimatic edge effects across riparian buffers.

Although riparian buffers are an important aspect of forest management in the boreal forest of Canada, little is known about the habitat conditions within buffers, due in part to complex edge effects in response to both the upland clearcut and the stream. We investigated microclimatic conditions and bryophyte growth and vitality in seven locations between the stream edge and 60 m into the upland undisturbed conifer forests and at the clearcut sites with riparian buffer 30 km northwest of Thunder Bay, Ontario, Canada. We hypothesized that the growth and vitality of a pleurocarpous moss, Hylocomium splendens, and an acrocarpous moss, Polytrichum commune, would be directly related to the microclimatic gradients detected. We further hypothesized that sensitivity of the bryophytes to environmental factors will vary depending on their life form type, i.e., pleurocarpous moss will respond differently than the acrocarpous moss. Both bryophyte species were transplanted in pots and placed at 10-m intervals along 60-m transects perpendicular to the stream across the buffer and undisturbed sites. Bryophyte growth, cover, and vitality, as well as microclimatic parameters and plant cover, were measured over the summer in 2003. The riparian buffers were simultaneously affected by microclimatic gradients extending from both the clearcut edge and the riparian-upland ecotonal edge. Both bryophyte species responded to changes in the microclimatic conditions. However, vapor pressure deficit (VPD) was the most important factor influencing the growth of H. splendens, whereas for P. commune growth soil moisture was most important. Our study confirms earlier findings that interior forest bryophytes such as H. splendens can be used as indicators to monitor edge effects and biodiversity recovery following forest harvesting. We demonstrate that growth and vitality of these bryophytes reflect the prevailing near-ground microclimatic conditions at the forest edges. Abundance estimates of such bryophytes can be used to determine the depth of edge effects across both ecotonal edges (e.g., riparian-upland forest edge) and anthropogenically created edges (e.g., clearcut edge). Forest management practices must consider depth of edge in determining the appropriate width of riparian buffers that would be necessary to sustain biodiversity and associated values at the land/water interface.