Sarah Gergel


Relevant Thesis-Based Degree Programs

Affiliations to Research Centres, Institutes & Clusters


Graduate Student Supervision

Doctoral Student Supervision

Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.

Understanding the human health benefits of urban green space across the life course by integrating epidemiological and novel geospatial approaches (2022)

Growing research indicates that natural environments – including green and blue spaces – are beneficial for human health. However, evidence gaps remain concerning the health associations with different types of natural environments and forms of human-nature contact, pathways underlying nature-health associations, and health associations across different life stages. To address these gaps, this dissertation examined the relationship between natural environments and human health among residents of Metro Vancouver, Canada. First, a method for estimating and comparing different forms of human-nature contact was developed, specifically access (i.e., living within proximity of a public green space) and exposure (i.e., quantity of natural and non-natural features surrounding residence). Next, these exposure metrics were used to analyze the association between access and exposure to natural environments and self-reported general health, mental health, and common mental disorders among respondents of the Canadian Community Health Survey (CCHS). The exposure metrics were likewise utilized in analyses investigating the association between exposure to natural environments and early childhood development, as measured by teacher-ratings on the Early Development Instrument (EDI). Finally, underlying pathways of nature-health associations were analyzed by evaluating potential mediation by reductions in traffic-related air pollution and noise. In general, natural environments were positively associated with human health. Nature-health associations varied according to land cover type. Specifically, water and some vegetation types were associated with lower odds of poor self-reported health among respondents of the CCHS, while exposure to tree and grass cover was positively associated with children’s EDI scores. Conversely, exposure to paved surfaces was adversely associated with self-reported health and children’s early development. Furthermore, nature-health associations varied according to form of nature contact, with more consistent associations observed for exposure than access. Finally, positive associations between green space exposure and early childhood development were partially explained by reductions in traffic-related air pollution and noise levels. This dissertation provides new empirical evidence of the benefits of natural environments on human health. Results support urban planning and policy frameworks that increase the availability of natural environments to contribute to optimal population health across the life course.

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Linking landscape indicators to groundwater nitrate concentrations in a transboundary aquifer (2018)

Groundwater aquifers provide nearly half the freshwater used in drinking and cooking. However, in the last century, massive transformations of landscapes have produced enduring impacts on natural resources such as groundwater. Excess nitrate contamination of groundwater is a growing health concern, particularly in agricultural regions. Despite its importance, very few studies have quantitatively linked land use land cover (LULC) and groundwater nitrate concentrations. Furthermore, understanding the impacts of LULC on transnational water resources is especially challenging as multi-jurisdictional data disparities and inconsistencies can complicate monitoring efforts.Here, I developed a suite of innovative long-term monitoring approaches and evaluated their utility in a well-studied transnational aquifer where elevated groundwater nitrate concentrations are of concern. My overall objective was to develop approaches for examining LULC impacts to groundwater via two primary components. First, I used remote sensing to examine two decades of LULC change surrounding 11 groundwater dependent cities. Second, I created more localized landscape indicators and evaluated their correspondence to long-term trends in groundwater nitrate concentrations. I examined two nested spatial extents spanning the US-Canada border including: small cities throughout the Greater Abbotsford-Sumas Aquifer region as well as the confined extent of the Abbotsford-Sumas Aquifer (ASA) proper. I integrated a unique combination of historical photography, transnational satellite imagery, and groundwater monitoring wells spanning four decades. Throughout the larger region, I found that landscape evenness increased over time driven by greater forest losses in Canada and greater losses of agricultural land in the USA. Within the localized ASA, I determined that groundwater nitrate concentrations could be explained using landscape features measured within the vicinity of wells. Landscape indicators such as the proportional area of berries, raspberry fields undergoing renovations, as well as forage/pasture were particularly useful. I further determined that long-term trends in nitrate were best explained by historical landscape indicators from two decades prior (as opposed to contemporaneous indicators). Very few studies have examined LULC emphasizing transboundary aquifers and even fewer have quantitatively linked groundwater nitrate concentrations to land use practices. Thus, this work demonstrates a valuable, consistent monitoring approach that is transportable to other regions facing similar challenges.

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Quantifying the development of small-scale fisheries on coral reefs, and their impact on habitats (2017)

Growing human populations place multiple pressures on social-ecological systems, including coastal oceans. However, the effects of long-term and/or overlapping stressors remain poorly understood, particularly over large spatial scales. My dissertation evaluated how pressures from fishing and co-occurring stressors correspond to current ecological conditions in the Danajon Bank, a coral reef ecosystem in the central Philippines. I used long-term local ecological knowledge (LEK) to map fishing practices (1950-2010) and high spatial resolution satellite imagery to map coastal habitats. This innovative suite of methods enabled me to examine patterns over broader spatial scales and longer time periods than those usually assessed. I met five primary objectives: (1) quantify the spatio-temporal dynamics of fishing effort and gear use; (2) examine the influence of fisheries governance; (3) map the spatial distribution of benthic (seafloor) habitats; (4) model the spatial distribution of living corals in relation to co-occurring stressors and biophysical conditions; and (5) explore the conservation implications of these relationships. While individuals’ fishing practices were fairly consistent over time, this small-scale fishery has changed dramatically. First, total fishing effort (days per year fished by all fishers) accelerated between 1960 and 2010 because of rapid growth in the number of fishers. Aggregate fishing effort increased almost 2.5-fold and spatially-explicit fishing effort increased over 20-fold. Second, the areal extent of fishing grounds expanded greatly. Third, use of fishing gears changed over time. Diversity of fishing gears increased, as did fishing effort with destructive, active, and non-selective gears. Considering the timing of these changes, I found a lasting influence of fishing policies, and small improvements in the sustainability of fishing gears following implementation of co-management. Finally, I found that the probability that an area supported living corals was affected by fishing through both long- & short-term mechanisms, and I documented strong coral-landscape relationships. My research demonstrates that to strengthen ocean conservation, it will be essential to reduce the frequency and intensity of stressors, remove some areas from exploitation, foster resilience traits of ecosystems, gather data to better understand systems, and strengthen the institutions that can support these endeavors.

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Long-term mapping of ecosystem services in a river-floodplain system (2016)

Humans derive a wide range of benefits from ecosystems, known as ecosystem services (ES). At the nexus of land and water, floodplains are particularly important for providing ES. Recently, problematic declines in ES have motivated research to better understand their spatial distributions. However, the temporal dynamics of critically important floodplain-specific ES remain poorly understood. These spatial and temporal dynamics as well as trade-offs that occur when management enhances one ES at the expense of others are particularly germane as a warming climate alters river flows. Landscape history is foundational to elucidating these dynamics. Here, I explore the importance of landscape history for understanding the historical, contemporary, and future distributions of ES in the Wenatchee watershed, central Washington State. Using several widely-used datasets in novel ways, my dissertation has five primary objectives (1) quantify the relative importance of different landscape positions for frontier settlers, (2) map change in ES from 1949-2006 using high-resolution imagery, (3) enhance understanding of ES interactions by incorporating change in ES over time, (4) explore the spatial distribution of floodplain-specific ES, and (5) conceptualize shifts in ES under future climates. I found riparian zones and floodplains were disproportionately important for frontier settlement, setting the stage to explore floodplain-specific ES in more detail. ES were dynamic from 1949-2006, largely driven by increasing urbanization and forest densification. Next, I showed how history can provide important insights into ES interactions. Finally, I also found floodplain ES varied considerably with floodplain position. Analyses over broad time frames and at fine spatial scales greatly enhance our understanding of ES dynamics, highlighting the need for long-term monitoring for ES, especially as ES continue to interact under future climates.

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Relative influence of cultural identity and market access on agricultural biodiversity in swidden-fallow landscapes of Eastern Panama (2012)

Agricultural biodiversity is essential to local and global food security, yet is being rapidly eroded world-wide. The increasing reach of global transportation and trade networks is predicted to homogenize agriculture at regional scales. However, relatively little is known about how cultural values and norms, as reflected in local farmer decision-making, will interact with market forces to sustain or erode agricultural biodiversity. Working with farmers from three ethnic backgrounds — Black, Emberá or Kuna — in a region of Panama undergoing rapid landscape change, I determined the relative influence of farmer cultural identity and market access on several indicators of agrobiodiversity. Twelve villages were chosen to minimize environmental differences while maximizing differences in access. Villages were classified as “highway” or “remote” based on time and cost of travel to Panama City markets, with each ethnic group represented by two highway and two remote villages. From 2007-2009, a combination of crop inventories and land-use mapping (for 645 fields) as well as interviews with > 130 farmers were conducted. Diversity of staple food crop varieties, agroforest trees and shrubs, and the spatial and temporal dynamics of shifting cultivation were compared among villages. Farmer cultural identity had a stronger impact on agrobiodiversity indicators than did access. For staple food crops (e.g., maize, rice, yam, cassava, bananas, and taro), ethnicity explained 2.5 to 8.5 times more variation in assemblages than access. Distinct assemblages of staple crop landraces (varieties) and agroforest trees and shrubs were associated with different ethnic groups, even where access was high, reflecting culturally patterned dietary preferences, ceremonial or customary uses, and culturally-bounded seed-exchange networks. Mean number, size, and types of fields maintained (homegardens, outfield agroforests, annual fields, pastures), as well as their management (e.g., forest felling, herbicide use), also varied among ethnic groups. These differences reflected culturally-based crop preferences, values of land, traditional settlement patterns, and contemporary relationships to other actors, including the Panamanian government. Together, the distinct agricultural practices of individual ethnic groups combined to create diversity across many levels of biotic organization: from landrace, to species, to patch, to landscape. These findings strongly suggest that new approaches to conservation that support and respect heterogeneous socio-cultural systems will be critical to global efforts to maintain agrobiodiversity.

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Sustainable Forest Management in the Context of Integrated Watershed Management in Southern China (2009)

No abstract available.

Relative influence of temperature and disturbance on vegetation dynamics in the Low Arctic : an investigation at multiple scales. (2008)

Climate change will affect Arctic plant communities directly, by altering growth and recruitment, and indirectly, by increasing the frequency of natural disturbance. Since the structure of northern vegetation influences global climate, understanding both temperature and disturbance effects on vegetation is critical. Here, I investigate the influence of temperature and disturbance on Low Arctic vegetation at several spatio-temporal scales in the Mackenzie Delta Region, N.W.T. To disentangle the relative impact of temperature and disturbance on forest-tundra and tundra ecosystems, I sampled microenvironmental variability, plant community composition, and green alder abundance, growth, and reproduction on disturbed (burns and thaw slumps) and undisturbed sites across a regional temperature gradient. Disturbed areas showed increases in alder productivity, catkin production, and seed viability, as well as differences in plant community composition and microenvironment. The magnitude of plot-level responses to disturbance compared to variation across the temperature gradient suggests that in the short-term, increasing the frequency of disturbance may exert a stronger influence on tundra ecosystems than changes in temperature. At the plot level, increases in alder seed viability and recruitment at warmer sites point to the fine-scale mechanisms by which shrub abundance will change. To examine the relative influence of temperature and biophysical variables on landscape-level patterns of shrub dominance, I mapped Low Arctic vegetation using aerial photos. At this broader scale, correlations between temperature and the areal extent of shrub tundra suggest that warming will increase the dominance of shrub tundra. To assess the magnitude of changes in temperature and thaw slump activity, I analyzed climate records and mapped retrogressive thaw slumps using aerial photographs. An increase in thaw slump activity in recent decades, coincident with higher temperatures, suggests that continued warming will change the area affected by thermokarst disturbances like slumps. Taken together, my research indicates that the effects climate change will be magnified by shifts in the frequency of disturbance, initiating changes to Arctic vegetation with significant implications for global climate. My work also shows that to fully understand the influence of patch-landscape feedbacks on Arctic vegetation dynamics, the effects of disturbance must be examined across longer temporal and broader spatial scales.

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Master's Student Supervision

Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.

Assessing the vulnerability of small-scale water resources using high spatial resolution remote sensing (2023)

Water stress due to physical scarcity and poor water quality impacts billions of people worldwide. Internationally, an important goal of the United Nations’ Sustainable Development Goals (SDGs) is the improvement of ambient water quality by tracking the proportion of inland water bodies with acceptable water quality. Thus, there is a global, pressing need for fast, reliable, and accessible ways to monitor the water quality in small inland water bodies. In this research, I evaluate the utility of high spatial resolution remote sensing for monitoring water quality constituents (Chlorophyll-a and turbidity) in small reservoirs (0.01 km²) in southwestern Kenya.First, I used a novel combination of remote sensing indices and landscape features to build statistically robust empirical models of water quality parameters that were measured in situ. I then used these models to extrapolate water quality in 60 reservoirs over 43 consecutive months (2019-July 2022) across a land-use gradient. These results were then used to examine patterns in water quality across space and time. Finally, I used high spatial resolution imagery to quantify the areal change (or drying out) of reservoirs throughout a single dry season.Overall, Sentinel-2 satellite imagery produced better models of Chl-a (R² = 0.66) when compared to PlanetScope imagery which produced more accurate maps of turbidity (R² = 0.72). Furthermore, introducing landscape features such as land cover, maximum reservoir size, and proximity to roads improved the statistical power of models by as much as 9%. Turbidity was marginally significantly different in reservoirs across the land-use gradient, with the transition zone having the most turbid reservoirs. From 2019 to 2022, Chl-a and turbidity have been steadily improving in 46% and 40% of reservoirs, respectively. Notably, Chl-a concentrations have been improving more rapidly in the cropland zone. Additionally, nearly half of reservoirs lost over 50% of their surface area during the 2021 dry season, a period of exceptionally intense drought; whereas a quarter of all reservoirs dried out completely. This research has the potential to help support monitoring and planning within the water resources sector by prioritizing the use of climate resilient infrastructure such as water pans.

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Tracking long-term landscape change: habitat connectivity for moose and fisher in Tsilhqot'in territory (2022)

Traditional ecological knowledge and values of Indigenous peoples are increasingly incorporated into resource management. However, science still lacks sufficient examples of collaborative research with Indigenous communities. To explore the potential of geospatial approaches in this regard, I examined changes in habitat connectivity from 1984 to 2019 for two species of significance to the Tŝilhqot’in First Nation: fisher (Pekania pennanti) and moose (Alces alces). Within the Tŝilhqot’in traditional territory, I used existing geospatial datasets in conjunction with ecological literature to map fisher and moose habitat suitability over time. Then, these suitability ratings were used as proxies for animal movement to create resistance surfaces. These resistance surfaces were further used in a long-term connectivity analysis for each species (via Linkage Mapper software) throughout the study area and within a highly disturbed sub-region. Connectivity was quantified using measures of patch size, corridors (i.e. cost-weighted distance), as well as importance values for patches and corridors (i.e. centrality) and areas of high resistance (i.e. barriers). Based on the accounts of Tŝilhqot’in communities and regionally reported population declines linked to landscape-level disturbances, I expected that connectivity would decline for both species. However, between 1984 and 2019, quantitative connectivity metrics for fisher habitat showed conflicting results, including decreased patch size in the disturbed sub-region but not across the total study area. Habitat connectivity indicators for moose generally indicated improved connectivity, including increased patch size and reduced intensity of barriers. Centrality (indicating the most important pathways) shifted greatly for fisher, yet not for moose habitat. Possible associations between decreased fisher population and habitat connectivity are discussed (such as habitat loss), as are the factors potentially explaining moose population declines despite increasing habitat connectivity (such as greater predation risk while accessing abundant browse). This research demonstrates a collaborative application of geospatial techniques that can enhance our understanding of landscape connectivity of Indigenous wildlife resources and offers suggestions for managing connectivity in the face of landscape alteration and climate change.

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Can forests increase food production? Exploring landscape configuration and crop productivity - a case study from Southern Ethiopia (2019)

Understanding the factors influencing agricultural yields and productivity is vital to food security. For millions of smallholder farmers, however, estimating field-level yields can be challenging. Furthermore, within agricultural landscapes interspersed with forests and trees, agricultural productivity in fields may be impacted by nearby forests, hedgerows, and other forms of tree cover. In an agricultural-forest mosaic in Southern Ethiopia, I used high spatial resolution (5-10m) satellite imagery to identify and differentiate two primary crops (with >90% accuracy) and assess the impact of nearby forest patches on wheat productivity. Second, using a suite of vegetation indices (VIs) as a proxy for wheat productivity, I determined whether productivity was enhanced or suppressed with increasing distance to forest. Results indicated that the proxies for wheat productivity increased by as much as 5% in parts of fields within 30 m of forest edges compared to fields further from forests. Lastly, I used historical and hypothetical future scenarios to examine the landscape-level implications of my results on overall wheat production. To do so, I applied the estimated 5% productivity increase to a series of agricultural-forested landscapes based on forest cover characteristics from the same study area. My goal was to compare and contrast landscapes to determine forest amounts and configurations which could optimize food production while minimizing forest loss. Between 1967 and 2013, a land cover and fragmentation analysis of Landsat and air photos showed a general trend towards reforestation (increase of ~8%) of more fragmented and sparser tree cover throughout the landscape over time. From hypothetical scenarios I found that forest edge productivity increases created non-linear food production benefits with hedgerow expansion. Differences in yield and production increases were ~2x higher when transitioning from a landscape with low to medium tree cover than transitioning from a landscape with high to higher tree cover. My results highlight potential benefits of a landscape approach for enhancing smallholder agricultural productivity in Southern Ethiopia. I argue that considering a landscape perspective can help support food security goals, particularly within the context of climate change considerations, and should play a more prominent role in planning for forest conservation and restoration.

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Scaling-up natural resource management in northern landscapes: utilizing landscape ecology and remote sensing in environmental impact assessment and wetland monitoring (2019)

The rapid pace of natural resource development often exceeds our capacity to comprehensively monitor its range of environmental impacts. More recently, increases in both the availability and spatio-temporal scale of environmental geodata have created new opportunities for improving environmental assessment and monitoring. Here I aim to improve upon the conceptual and technical basis for scaling-up assessment and monitoring via exploration of two contrasting landscapes typical of northern Canada. In Chapter 2, I examined different ways of incorporating landscape ecology and ecosystem service approaches into the first phase of Environmental Impact Assessment (EIA) during the scoping process. Using examples from the Skeena River watershed in northwest British Columbia, I first demonstrated how changing the extents of spatial boundaries can potentially misrepresent cumulative impacts. Second, I used network analysis to assess the extent to which seemingly small, localized developments can disrupt landscape connectivity and how historical aerial photographs can help improve restoration planning. Lastly, I present a framework for using regulating ecosystem to better account for water filtration services provided by wetlands. Building upon these insights, in Chapter 3 I utilized a 27-year time series of Landsat imagery to monitor road construction and evaluate subsequent recovery trends in boreal peatlands. I examined long-term trends of wetland-relevant tasseled cap (TC) indices (wetness, greenness, etc.) using a Before/After, Control/Impact study design, which also controlled for the impact of precipitation trends. I demonstrated not only that hydrologic disruption is discernible via remote sensing, but that it persisted for at least 5-years post-disturbance with no signs of hydrologic recovery in several types of wetlands. Furthermore, hydrologic disruptions following road construction were not evenly distributed within wetlands, but rather concentrated near roadside margins. Taken together, my research provides insight into the possibilities for practical yet rigorous up-scaling of environmental assessment techniques using open-source data. Furthermore, my work also highlights current gaps in implementation of concepts and tools in environmental monitoring, as well as solutions to aid responsible, transparent natural resource development.

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New approaches for understanding urban greenspace using ecosystem services concepts and high spatial resolution mapping (2018)

Urban areas are where most people in the world directly benefit from ecosystem services (ES), yet there is evidence that ES are distributed inequitably with respect to socio-economic status which can lead to environmental injustices. There are a number of barriers to understanding UGS equity, some conceptual and some technical. One barrier is that few studies of environmental justice use similar quantitative methods, nor do they use concordant conceptual frameworks of UGS and ES equity. Another barrier is the fine scale information needed to accurately map greenspace can be difficult and expensive to obtain. In light of these barriers, this thesis seeks to contribute to UGS/ES equity studies in two fundamentally important ways.First, I explore the concepts of equity in ecosystem services as applied to urban settings. I undertake a review of trans-disciplinary literature on urban systems to answer the question “How has environmental justice been considered and incorporated into urban ES research?” I characterize types of urban ES and measure the breadth of justice issues addressed in each article using a new environmental justice index (EJI). I also highlight the methods and results of key quantitative and qualitative papers that can inform future urban ES justice frameworks. Second, I explore how new advances in remote sensing can better characterize UGS distributions via more accurate mapping of heterogeneous urban areas. I combine three-dimensional information from airborne Light Detection and Ranging (LiDAR) data with RapidEye high spatial resolution imagery in a Geographic Object-Based Image Analysis (GEOBIA) approach to classify urban landcover in a large metropolitan region. Though 5m RapidEye pixels were often mixed in urban areas, LiDAR data enabled accurate classification of fine spatial objects such as street trees and single-family dwellings. Ultimately, I propose that mapping ES distributions among urban socio-demographic groups and assessing potential ES tradeoffs is not enough to avoid injustices. Because ES are socio-political constructs, gaining a comprehensive understanding of urban ES injustices is not merely a process of mapping greenspace, but also understanding how the groups in question ascribe value to the ES supply sources around them.

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Land degradation in Central Asia: identifying dynamics of pasture resources in heterogeneous landscapes using remote sensing (2016)

Rangeland degradation is an issue of global concern yet it can be challenging to accurately assess. In Kyrgyzstan, the post-Soviet transition led to wide-ranging environmental changes in pasturelands, though comprehensive and spatially explicit data remains scarce. Remote sensing vegetation indices (VI) are often used to assess pasture condition where higher VI are assumed to indicate greater productivity. However, pasture productivity may be degraded owing to declining vegetation productivity or changes in plant species composition, both of which can differentially affect vegetation indices. Here, we examined these two aspects using satellite-derived vegetation indices. In Chapter 1, we compared temporal trends (2000-2015) and seasonal maximums of Moderate-Resolution Imaging Spectroradiometer (MODIS) VI in field sites with varying cover of plant species unpalatable to livestock. Relative to other pastures, we found pastures with unpalatable plant cover were associated with higher seasonal maximums of VI (r² = 0.23-0.31) and increases in VI over time (r² = 0.08-0.16). These findings were problematic for pasture monitoring using remote sensing, as detrimental changes in species composition may be conflated with desirable increases in plant cover. In Chapter 2, we examined pixel-based temporal trends in the Normalized Difference Vegetation Index (NDVI) in Naryn oblast, Kyrgyzstan from 2000-2015. We then examined trends in the residuals after applying a regression relationship linking NDVI as a function of precipitation and temperature metrics in order to differentiate anthropogenic from climate-induced impacts to pasture resources. Trend maps were validated against areas of overgrazing identified from interviews with local pasture managers. Temporal trends in NDVI and the regression residuals were overwhelmingly negative (24.0 and 15.2% of the landscape, respectively) outside of row crop agricultural fields, particularly in the lower elevation spring/fall and winter pastures, and were consistent with local managers’ perceptions of pasture degradation. While our approach was limited by the topographic complexity of the study region, it was most successful in the semi-arid steppe region where pasture degradation is believed to be worst.

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Towards improved understanding and management of mixed-security fire regimes in mountain forests (2013)

Understanding spatial and temporal patterns of fire regimes is critically important forsustainable forest management and fire hazard mitigation. Mixed-severity fire regimes, inparticular, are poorly understood, yet increasingly recognized as important drivers of stand and landscape-heterogeneity. I address knowledge gaps pertaining to the management andunderstanding of mixed-severity regimes including: (1) classification and mapping, (2)prevalence in mountain forests, (3) underlying topographical drivers, and (4) stand dynamics. Research questions were addressed using dendrochronological field data (fire scars, tree establishment dates, stand composition and structure) from 20 randomly selected research sites in southeastern British Columbia,I examined whether mixed-severity regimes, as currently represented in fire-regimeclassification schemes, led to erroneous landscape-level fire regime mapping. I used my field data to evaluate the accuracy of two classification systems (Natural Disturbance Type (NDT)and Historical Natural Fire Regime (HNFR)) used by managers to map fire regimes in BritishColumbia (Chapter 2). Each classification system made considerable and contrasting errors in identifying mixed-severity regimes relative to the field data and these misrepresentations were tied to elevation. I attributed these errors to assumptions about disturbances underlying each classification system, as well as limitations of the research methods used to estimate firefrequency (i.e., using either stand-age or fire-scar data in isolation). I explored the prevalence of mixed-severity fire regimes, importance of underlying topographic drivers, as well as the influence of mixed- versus high-severity fires on forest composition and structure (Chapter 3). I found evidence of mixed-severity fires at 55%. At these sites, most reconstructed fires (73%) were documented solely by fire scars, indicating many were of low-to-moderate severity. The remaining 27% of fires were severe enough to create conditions suitable for even-aged cohort to establish. Spatial patterns of fire severity were primarily controlled by elevation (i.e., severity increased with elevation). Composition varied with disturbance history; however, structural differences (e.g., tree size classes) were subtle, with the exception of snag densities, which were much greater in old, high-severity forests (where time-since-last-fire >250 years). Understanding the ecological heterogeneity created by mixed-severity regimes potentially influences decisions related to conservation, silviculture, wildfire and fuel mitigation.

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Current Students & Alumni

This is a small sample of students and/or alumni that have been supervised by this researcher. It is not meant as a comprehensive list.

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