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Urban Soil Health and Tree Performance: A Diagnostic Framework and Biochar–Inactivated Yeast Case Study from Toronto
Full text linkUrban trees are a cornerstone of ecosystem service delivery in cities, supporting key functions such as cooling, carbon sequestration, stormwater regulation, and habitat provision. Yet their establishment and long-term persistence face substantial challenges, among which degraded urban soils and the resulting site limitations are often a primary cause of poor growth and low survival. To clarify the mechanistic chain linking “soil constraints–tree health–canopy targets and functional outcomes,” this study addresses two central questions: how urban soil health can be diagnosed more effectively, and which amendment strategies are more likely to sustain robust urban tree performance. We develop a soil-health indicator framework tailored to urban forestry management that integrates conventional physicochemical metrics with microbial and process-based indicators, highlighting the latter’s critical roles in nutrient cycling and stress responses. We then conduct a greenhouse experiment using American elm (Ulmus americana) under a three-factor design (Biochar × Inactivated Yeast × De-icing Salt), measuring soil pH, electrical conductivity (EC), soil organic matter, and microbial functional activity characterized by Biolog EcoPlate (e.g., AWCD), alongside seedling growth and multiple physiological traits. Results show that biochar significantly increased soil organic matter (by 85% and 103% relative to the control under non-saline and saline conditions, respectively). In contrast, microbial functional activity was more sensitive to amendment combinations: compared with the control, biochar alone increased AWCD by 43%, whereas inactivated yeast and its co-application with biochar elevated AWCD by 79%–174%, with differences among yeast types and combinations. On the plant side, several growth and physiological indicators improved under selected amendments, including under salt stress. Importantly, correlations based on treatment means revealed more consistent covariation between microbial functional metrics and tree performance, underscoring that biological dimensions, particularly microbial functional indicators, are essential for understanding the coupling between urban soil health and tree outcomes and should be incorporated into routine diagnosis and monitoring. More broadly, soil management and intervention strategies should be implemented within a continuous monitoring and adaptive management loop to enhance the transferability and long-term effectiveness of amendment prescriptions across urban contexts
Caledon’s Natural Heritage System and Urban Development: How Policy Impacts Fragmentation
Full text linkCaledon does not yet have a comprehensive municipal NHS in place. Although Caledon has large tracts of natural cover, both its locations and ownerships are
fragmented. Given Caledon's expected significant expansion of its built environment by 2051, as per both the Future Caledon OP and the Region’s OP, Caledon must identify a municipal NHS to protect and preserve it in the future. Given that Caledon is the least developed of the three municipalities in the Region of Peel, urban expansion does not need to be an inherent threat to Caledon’s natural systems and green identity. Instead, it is an opportunity. With so much natural cover and relatively sporadic development, Caledon has everything required to create a robust NHS. However, time is running out for Caledon to delineate and preserve its NHS. With the new Future Caledon Plan, the new SABE areas risk fragmenting the NHS so much within southern Caledon that it may lose connectivity with natural features located in both Brampton and northern Caledon
Incretin Mimetics as Potential Therapeutics for Concussion and Traumatic Brain Injury: A Narrative Review
Full text linkTraumatic brain injury (TBI) represents a significant health concern, with an estimated 70 million annual cases worldwide. Mild brain trauma (concussions) is the most common TBI (81%), followed by moderate (11%) and severe (8%). Cytokine release and neuroinflammation after TBI may cause blood–brain barrier and tissue damage, triggering unfavorable outcomes, including disabilities and mortality. Current TBI treatments, focused on preventing secondary injury, are limited and insufficient. Therefore, new therapeutic approaches are necessary. A growing body of recent literature supports the potential use of incretins: glucagon-like peptide-1, glucose-dependent insulinotropic peptide, and glucagon receptor agonists, as potent neurotrophic/neuroprotective agents. Experiments performed in cellular and animal models, and a limited number of clinical studies, provide evidence that incretins might be a novel and effective treatment for TBI. Incretin-based compounds have already been shown to be safe and efficacious for the treatment of type 2 diabetes mellitus in humans. Therefore, incretins are ideal candidates for rapid evaluation in clinical trials of TBI and might become a novel therapeutic tool for a condition that has very few disease modifying treatments available. Well-designed human clinical trials are urgently needed to determine optimal dosing, timing, and patient selection for effective incretin use in concussion and TBI
Power and Purpose: The Quiet Evolution of Canadian Municipal Law
Full text linkThis paper is part of the IMFG Papers on Municipal Finance and Governance series. For a full list of papers, please visit http://bit.ly/2ylAa2D.Local government is a vital part of Canada’s multi-level democracy. It provides a voice for the needs, desires, and aspirations of local communities and shapes the environments in which we live. Amidst growing calls for greater local autonomy and expanded local powers and resources, this paper contributes a comparative overview of municipal law in Canada’s ten provinces and three territories. We find that Canadian municipal law has experienced a quiet evolution over the past 40 years. The scope of municipal legal authority has expanded considerably as provinces and territories have revised their general municipal acts and adopted special laws for major cities. While the overall trend has been toward more permissive authority and the recognition of municipalities as democratic, accountable, and responsible governments, there are significant variations, both in law and in practice, among and within provinces and territories. We conclude that the practical potential of this wave of legislative reform is not fully known and may be unrealized, and requires further research.Institute on Municipal Finance and Governanc
Mid-Rotation Thinning Strategies in Lodgepole Pine Under Varying Stand Density Conditions: A TASS Simulation Study
Full text linkStand density is a primary driver of structure, growth, and productivity in even-aged lodgepole pine (Pinus contorta var. latifolia) stands. This study evaluated responses across three mid-rotation lodgepole pine blocks using stand-level metrics and TASS growth modeling. Species-level analyses showed that lodgepole pine dominated all blocks, accounting for 74–95% of stand composition and exhibiting low variability across basal area, diameter, and stem density (CV ≤ 20%). In contrast, spruce, balsam fir, and deciduous species displayed high coefficients of variation (57–118%) which shows little contribution to stand structure or dynamics. Low Shannon diversity and evenness values further confirmed the monoculture nature of these stands. This supported the exclusion of minor species from growth modeling and the treatment of each block as a lodgepole pine monoculture in TASS simulations.
When modeling thinning scenarios, the responses differed greatly depending on initial stocking level. In the overstocked block, thinning reduced early density driven mortality, increased diameter growth, and improved total volume by capturing stems otherwise lost to self-thinning. In the moderately stocked block, thinning increased individual tree size but reduced total yield. This showed that thinning timing is more critical than thinning intensity. In the understocked block, thinning provided minimal structural benefit and resulted in substantial volume loss. Results suggested that thinning is counterproductive when stands are below the Zone of Imminent Mortality (ZIM).
Overall, results indicate that optimal management of lodgepole pine stands depends on maintaining mid-rotation stem densities near 900–1200 stems per hectare. This allows for the highest productivity by to minimizing mortality and maximize yield. Thinning is most beneficial in overstocked stands, due to competition induced mortality. Moderately stocked stands require delayed thinnings to fully take advantage of the treatment. While thinning is not recommended in understocked stands. This study emphasizes the importance of early density management and site-specific silvicultural prescriptions to optimize long-term stand productivity
Optimized Global Resolvent Analysis to Improve Plasma Actuator Control over the Airfoil Surface
Full text linkThis article appears in AIAA Journal and may be found at the following link: https://arc.aiaa.org/doi/10.2514/1.J065249This study explores the impact of a single dielectric-barrier discharge (SDBD) plasma actuator on the flow characteristics over a NACA0015 airfoil, focusing on the effects of varying forcing heights and frequencies. Using large-eddy simulation (LES) validated against experimental data, global resolvent analysis was integrated with spectral proper orthogonal decomposition (SPOD) to optimize the alignment between LES snapshots and resolvent response modes. Findings reveal that plasma actuator excitation below the response mode peak enhances trailing vortex structures, improving flow control. The study demonstrates that lower forcing frequencies and optimal plasma heights significantly enhance aerodynamic performance by reducing flow separation and improving lift-to-drag ratios. These insights contribute to developing more efficient active flow control strategies for applications in aircraft and wind turbine performance enhancement.This work was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC). NSERC did not contribute to the design of the study, data collection, analysis, interpretation, or writing of the manuscript. This work was supported by the Natural Science and Engineering Research Council of Canada and the Niagara Cluster Computing Platform. Computations were performed on the Niagara CPU cluster at the SciNet High-Performance Computing consortium, which included support from the Canada Foundation for Innovation under the auspices of Compute Canada, the Government of Ontario, the Ontario Research Fund–Research Excellence, and the University of Toronto
Explaining and Reducing Urban Heat Islands Through Machine Learning: Evidence from New York City
Full text linkUrban heat islands (UHIs) have intensified in rapidly urbanizing regions like New York, exacerbating thermal discomfort, public health risks, and energy consumption. While previous research has highlighted various environmental and socioeconomic contributors, most existing studies lack interpretable, fine-scale models capable of quantifying the effects of specific drivers&mdash;limiting their utility for targeted planning. To address this challenge, we develop an interpretable machine learning framework using Random Forest and XGBOOST to predict land surface temperature across 1800+ census tracts in the New York metropolitan area, incorporating vegetation indices, water proximity, urban morphology, and socioeconomic factors. Both models performed strongly (mean R<sup>2</sup> &asymp; 0.90), with vegetation coverage and water proximity emerging as the most influential cooling factors, while built form features played supporting roles. Socioeconomic vulnerability indicators showed weak correlations with temperature, suggesting a relatively equitable thermal landscape. Optimization simulations further revealed that increasing vegetation to a threshold level could lower average surface temperatures by up to 6.38 &deg;C, with additional but smaller gains achievable through adjustments to water access and urban form. These findings provide evidence-based guidance for climate-adaptive urban design and green infrastructure planning. More broadly, the study illustrates the potential of explainable machine learning to support data-driven environmental interventions in complex urban systems
Assessing Glyphosate Impacts on Fire Occurrence in Alberta’s Foothills and Boreal Forests
Full text linkThe use of herbicides in forestry operations is a contentious topic which has raised public concern regarding its impacts on waterways, traditional food sources and wildlife, prompting widespread protests throughout Canada. Wildfire frequency and severity have been showing increasing trends throughout the country, with Alberta’s unprecedented 2023 fire season burning 2.2 million hectares. The relationship between intensive herbicide spraying in forestry and wildfires has been brought to media attention in recent years, but current research on the topic has been limited. This study assessed the relationship between fire occurrence and glyphosate-based herbicide treatment at the block-level over the last 27 years across an area of over 250,000 ha in North-West Central Alberta. Using Pearson’s chi-squared tests and logistic regressions, glyphosate sprayed blocks showed fewer fire presences while unsprayed blocks showed more fire presence than expected values at several different geographic scales. Time since spray was not shown to be a significant factor contributing to fire occurrence in this analysis. These results call into question the impacts of intensive silviculture and harvesting on fuel loadings, best management practices for mitigating wildfire risk, and directions for future research
Cultivating Curiosity and Metacognition Through SDG-Focused Problem-Based Learning in a Global Classroom
Full text linkCommunication and writing skills are critical for employability and leadership in sustainability and STEM fields, but few studies examine how interdisciplinary, problem-based learning (PBL) environments foster these competencies amongst undergraduates. This three-year study examined how human resource management (HRM) and Chemistry students collaborated on Sustainable Development Goal (SDG)-themed projects within a Global Classroom model. We used LIWC-22, a validated text analysis tool to assess students&rsquo; written reflections about their discipline-specific PBL exercises (e.g., debates about UBI) and their SDG-focused inter-disciplinary group projects (e.g., vaccine access). We found that the HRM students (<i>n</i> = 84) demonstrated increased use of curiosity and cognition language during in-person and synchronous collaboration contexts. Chemistry students collaborating synchronously with their HRM teammates exhibited enhanced curiosity in their writing, though findings for this group are tentative due to the small sample size. Our findings suggest that both discipline-specific and SDG-focused interdisciplinary PBL activities can improve undergraduates&rsquo; metacognitive skills and their curiosity, which are critical for addressing sustainability challenges. Our Global Classroom offers a scalable model of how SDG-focused PBL activities can be used to create collaborations between STEM and management undergraduates and enable them to develop context-specific solutions for global sustainability challenges while improving their communication and writing
Improving Urban Tree Health through Biochar and Biofertilizer to Support Toronto’s 2050 Canopy Cover Goal
Full text linkStreet trees are extremely important to the urban forest but they face higher than average
mortality rates due to difficult growing conditions. Soil amendments can be an effective way of
improving tree health. Biochar has been shown to improve nutrient and water retention and assist
in mitigating soil compaction. One caveat of biochar as a soil amendment is its tendency to
immobilize nitrogen in the short term. That is why we are testing biochar in combination with
inactivated yeast (IY) which is a typical waste product of breweries and an important source of
nitrogen in our experiment. Our four month greenhouse experiment located in Toronto, ON,
showed the combination of biochar and IY had promising results in terms of improving biomass
and physiological tree health metrics. These soil amendment applications can be scaled to the
City of Toronto’s urban forest in order to assist in their 2050 canopy cover goal of 40%