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Examining the Effects of Traits on Early-Establishment Tree Communities Under Different Soil Water Conditions
(University of Waterloo, 2025-11-12) Galarneau, Magalie
Studies have demonstrated the existence of a positive relationship between species richness and productivity in forests around the world. This positive relationship is thought to be explained by two mechanisms: complementarity effects and selection effects. Both mechanisms rely on species’ traits, whereby the diversity of traits (under complementarity effects) or the presence of specific trait values (under selection effects) can increase productivity. However, while it has been clearly established that species richness increases productivity, few studies have tested the implicit assumption that traits underpin the established species richness-productivity relationship. To address this gap, this study examined which traits are responsible for the species-productivity relationship in temperate tree communities during the early stages of stand development, and whether they act via complementarity effects or selection effects. In addition, this study aims to determine how the observed relationship and its underlying traits change in environments with different water availabilities by assessing which traits are associated with productivity in each environment. These questions were answered using an experimental plantation of temperate tree communities in the early stages of stand development, in which water exclusion treatments were implemented. Six temperate tree species were planted in this experiment, either in a monoculture or in a three-species mixed community. To separate the effects of species and trait diversity, the mixed tree communities had a fixed species richness but varied in trait diversity. The species compositions of the mixes were selected to create a trait diversity gradient. Leaf area, leaf mass per area, stomatal density, chlorophyll concentration, specific root length, root tissue density, and root diameter were measured in each community. Community productivity was measured both as aboveground biomass and as belowground biomass. The most consistent pattern of selection in the press treatment was for leaf area, as it was under selection in combination with leaf mass per area and with stomatal density. Pairs of traits including specific root length were also under selection in the pulse and the control treatments. Selection for these traits resulted in three to fivefold increases in aboveground biomass. These results demonstrate that selection effects are the driving force of community productivity during stand establishment. Here, selection acted upon traits related to tree architecture, thermoregulation, photosynthetic rate, and water use, which illustrate the mechanisms by which selection effects drive increases in the productivity of early-establishment communities across varying soil water conditions.
An Investigation of Campuses' Sustainability Practices in Nigerian Higher Education Institutions
(Emerald, 2025-09-04) Bamidele Jimoh, Ibrahim; Clarke, Amelia; ElAlfy, Amr; Weber, Olaf
Purpose: This study aims to dive into the unique context of Nigerian universities, exploring their roles in terms of campus sustainability practices and the challenges they face while implementing sustainability initiatives. Design/methodology/approach: This study investigates sustainability practices through in-depth interviews with higher education institutions (HEIs) in developing countries. Experts from eight different government-owned universities in the Southwestern region of Nigeria participated in this study through a purposive sampling technique. The study leveraged the Sustainability Tracking and Rating System framework to determine potential sustainability management indicators tailored to the Nigerian context. Findings: The findings reveal a limited degree of engagement and implementation and show that HEIs adopt a wide range of sustainability approaches. Hence, underlying the necessity for concerted efforts to enhance sustainability initiatives in Nigerian HEIs. Originality/value: To the best of the authors’ knowledge, no previous studies have investigated Campuses’ Sustainability Practices in Nigerian HEIs. This study contributes to the body of literature by clarifying the challenges faced by Nigerian HEIs as their comprehension of sustainability practices widens, which has gotten little attention in previous literature.
Integration of Borehole Geophysical Logging with Hydraulic Tomography Analysis for Improved Groundwater Flow and Transport Predictions
(University of Waterloo, 2025-11-11) Wang, Chenxi
Hydraulic Tomography (HT) has been demonstrated to be a robust approach to characterize the subsurface heterogeneity, which employs the inversion of head data collected from multiple pumping tests to estimate the spatial distribution of hydraulic properties (e.g., hydraulic conductivity (K) and specific storage (Ss)). However, the resolution of K and Ss tomograms is reduced when the number of pumping tests and observation density gradually decrease. Another issue is that HT’s ability to predict solute/heat tracer transport behavior has not been rigorously examined for complex aquifer systems. Previous studies showed that different types of data (e.g., geological, geophysical, and other hydraulic testing data) carrying non-redundant information can be integrated with HT analysis to improve the mapping of K heterogeneity. This thesis evaluates the effectiveness of integrating geophysical logging data with HT analysis for improved imaging of K distributions. Furthermore, a heat tracer test was conducted in a highly heterogeneous glaciofluvial deposit to investigate the feasibility of reproducing the spatial distribution of observed temperature responses based on a heat transport model with HT K estimates. Five sequential studies are documented in this thesis to explore the integration of borehole geophysical logging with HT analysis for improved mapping of K and porosity heterogeneity, which enables enhanced predictions of groundwater flow and solute/heat tracer transport: (1) Study I integrated two conventional geophysical logging surveys, including electrical conductivity (EC) and gamma ray (GR) logging, with HT analysis to yield 2D K fields in a numerical sandbox experiment. A new spatial conditioning term was proposed to better delineate the hydrostratigraphy from geophysical logging data, which was used to derive the initial guess of K fields for geostatistical inverse modelling of HT analysis. The HT K models with comparative initial guesses of K distributions were evaluated based on their predictive capabilities for groundwater flow and solute transport. After demonstrating the effectiveness of integrating geophysical logging with HT analysis for improved K estimation in a numerical sandbox study, the subsequent studies were conducted at the North Campus Research Site (NCRS) underlain by a highly heterogeneous glaciofluvial deposit. (2) Study II conducted nuclear magnetic resonance (NMR) logging at the NCRS. Compared to conventional geophysical logging surveys, NMR logging can directly provide K estimates, as well as total porosity and effective porosity measurements. The petrophysical relationship between NMR signals and K was site-specifically optimized, and the NMR-derived downhole K profiles were compared with a variety of hydraulic measurements to evaluate their accuracy and resolution along boreholes. (3) Study III constructed 3D K fields based on downhole NMR K profiles and evaluated the representativeness of these K models. Various spatial interpolation approaches were employed to generate spatial K patterns. A multi-level heterogeneity characterization approach was proposed to better represent the layered porous medium at the NCRS. The model performance to predict groundwater flow was examined through simulating the observed drawdown responses from multiple pumping tests. (4) Study IV integrated NMR logging with HT analysis for improved characterization of subsurface heterogeneity. To highlight the importance of incorporating high-resolution initial K distributions to reduce the smoothness of K tomograms, a limited HT calibration dataset with fewer pumping tests and decreased observation density was utilized for model calibration. The effectiveness of this integration was evaluated through a comparative case study using varying numbers of head data for calibration and different spatial interpolation techniques for constructing initial NMR K models. (5) Study V conducted a heat tracer test at the NCRS, in which a dense monitoring network was installed to record temperature responses. The ability of various characterization approaches (e.g., HT analysis) to accurately map K heterogeneity was investigated by reproducing the complex spatial distribution of the temperature breakthrough curves (BTCs). Additionally, NMR-derived effective porosity was used to map a heterogeneous porosity field. Lastly, the sensitivities of heat tracer plume migration to flow, transport, and thermal parameters were investigated. The main contributions of these studies are: (1) conventional geophysical logging survey can provide hydrostratigraphic information to improve the resolution and accuracy of HT estimates; (2) NMR logging yields reliable downhole K estimates for interbedded layers of gravel, sand, silt and clay; (3) after spatial interpolation, 3D K models can be constructed based on NMR logging, which offers reasonable drawdown predictions to pumping tests; (4) integrating NMR logging with HT analysis can provide more representative K estimates consistent with the depositional environment, and the integrated models can still yield reliable K estimates at high resolution when only a limited head data is available for calibration; and (5) the complex temperature response from a heat tracer test can be best reproduced using HT analysis and NMR logging to represent the heterogeneous K and effective porosity fields. Based on their robust performance in predicting groundwater flow and solute/heat transport at different scales, this work advocates the joint use of HT analysis and borehole geophysical logging to characterize subsurface heterogeneity.
From sufficiency principles to circular economy strategies
(Taylor & Francis, 2025-10-29) Chenavaz, Regis Y.; Dimitrov, Stanko
The ecological crisis, marked by the transgression of planetary boundaries, necessitates a reevaluation of sustainability paradigms, including the integration of sufficiency and circular economy principles. Traditional sustainability models, reliant on technological solutions and market mechanisms, inadequately address the root causes of ecological degradation, such as overconsumption and economic expansion. This research advocates for a paradigm shift toward sufficiency and explores its integration with circular economy practices. Utilizing a review of the literature, we examine how sufficiency drives circular economy. We implement a two-stage search-protocol-driven selection in Web of Science and a qualitative complement focused on recent work - yielding a corpus of 113 articles. From this evidence, we develop a sufficiency-centred framework with three tiers: core pillars (limit setting; operational and normative thresholds; transparency and accountability), implementation guidelines (co-efficiency and product-service systems under weak sustainability; absolute caps, longevity, repair, and degrowth-aligned metrics under weak sustainability), and outcomes (relative gains with rebound risk versus absolute reductions within planetary limits). The framework clarifies how sufficiency reorients circular strategies from recycling toward preventing demand, extending product lifetimes, and retaining value at higher orders. We conclude with actionable implications for governance and stakeholder engagement, and identify barriers and enablers shaping sufficiency-driven transitions in firms and policy.
Mechanical Testing of Adhesive, Self-Piercing Rivet, and Hybrid Jointed Aluminum Under Tension Loading
(Elsevier, 2022-03) Ibrahim, Ahmed; Cronin, Duane
Joining technologies play a crucial role in facilitating vehicle weight reduction, while maintaining structural performance and vehicle crashworthiness. Adhesive and self-piercing rivet (SPR) joining have individually been assessed in joining multi-material structures including aluminum alloys; however, limitations include fixturing requirements for adhesive joints and non-uniform load distribution within SPR joints. Hybrid (adhesive-SPR) joining has been proposed to potentially address these limitations. Yet, there is limited data regarding the strength, stiffness and energy absorption of hybrid joints under tension loading, and a lack of quantitative comparisons between adhesive, SPR and hybrid joints. In the present study, adhesive, SPR and hybrid joints were created in aluminum H-shaped tension specimens and the joint morphologies were quantified. Joint strength, stiffness and energy absorption were compared for two aluminum sheet metal alloys and three sheet thicknesses. Adhesive joints exhibited higher strength (up to 20.5%) and stiffness (up to 422%) than SPR joints, while SPR joints demonstrated higher energy absorption (up to 352%). Hybrid joints in 3 mm sheet exhibited reduced strength and stiffness relative to adhesive joints. Importantly, hybrid joints for 1 and 2 mm sheet thicknesses demonstrated strength and stiffness comparable to adhesive joints (<8% difference), and improved energy absorption compared to adhesive (up to 336%) and SPR joints (up to 53.5%), enhancing the performance of the individual methods. The study results could facilitate identifying suitable joining method, sheet thickness and alloy type according to structural applications (e.g. intrusion prevention versus energy-absorbing structures), and support future adoption and improvement of hybrid joints.