Chasmer, Laura
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- ItemPost-fire vegetation regeneration during abnormally dry years following severe montane fire: southern Alberta, Canada(Elsevier, 2025) Aspinall, Jesse; Chasmer, Laura; Coburn Craig; Hopkinson, ChristopherFire regimes across montane regions of western Canada are changing resulting in longer fire seasons, higher intensity fires, and shortening fire return intervals. The implications of high severity fire and warmer, drier early post-fire conditions on herbaceous understory vegetation regeneration and seedling recruitment in the southern Canadian Rockies are not well known. The overall objective of this study is to quantify trajectories of vegetation recovery (species, structural characteristics, and biomass) during early years of abnormally warm, dry conditions following a high severity fire in two moisture endmember sites Waterton Lakes National Park, Alberta, Canada. Here, we compare the within and between year spatial and temporal variability of vegetation growth and species density and how these change over time and across the broader area as an indicator of ecosystem resilience within these endmember sites. Moderate to extreme drought occurred during the years following fire at Waterton, where 2021 was ranked as the 2nd driest year in 26 years. Despite this, the moist site was characterised by greater herbaceous vegetation recovery with few lodgepole pine seedlings (average biomass = 335 g m−2), while a drier site had greater seedling recruitment over a period of 5 years. Variations in site environmental conditions were more impactful than differences between years (drought) on post-fire vegetation recovery. Use of remotely piloted aircraft system (RPAS) remotely sensed data provided an effective means for quantifying variability in regenerating vegetation height (structure from motion), cover (green chromatic coordinate), and biomass when compared at plot level (R2 = 0.53, 0.53, and 0.30 respectively) using optical photogrammetric methods. The research presented has implications for forest and fuel management in Canada as national parks and forest agencies consider historic use of heterogeneous species patches. High density of lodgepole pine seedling recruitment in mineral soils and under very dry conditions indicate resilience to drought. This will require continued and expanded monitoring as other tree species recruits populate the post-fire environment.
- ItemA bi-temporal airborne lidar shrub-to-tree aboveground biomass model for the taiga of western Canada(Taylor & Francis, 2024) Flade, Linda; Hopkinson, Christopher; Chasmer, LauraMonitoring aboveground biomass (AGB) is critical for carbon reporting and quantifying ecosystem change. AGB from field data can be scaled to the region using airborne lidar. However, lidar-based AGB products emphasize upland forests, which may not represent the conditions in rapidly changing peatland complexes in the southern Taiga of western Canada. In addition, to ensure that modeled AGB changes do not incorporate systematic error due to differences between older and newer lidar technologies, model transfer tests are required. The aim of this study was to develop one bi-temporal lidar-based AGB model applicable to (1) vegetation structures at varying vertical and horizontal continuity in this region and to (2) data collected with an earlier generation lidar system for which Canada-wide aerial coverage is available. Goodness-of-fit metrics show that AGB can be modeled with moderate (R2 = 48%–58% Taiga Shield, peatlands) to high accuracies (R2 = 83%–89% Taiga Plains, upland/permafrost plateau forests including ecotones) by using the point clouds average height and 90th height percentile within a weighted approach as function of modeled AGB and calibrating the earlier lidar data. These results are important for quantifying climate change effects on forest to peatland ecotones.
- ItemWarmer air temperatures predicted to result in wetland drying in the Upper Columbia River Valley, British Columbia, Canada(Elsevier, 2025) Rodrigues, Italo Sampaio; Hopkinson, Christopher; Chasmer, Laura; MacDonald, Ryan J.; Bayley, Suzanne E.Climatic warming is likely to affect the Canadian Rockies, leading to changes in the land cover (LC) and hydrological cycles. This study estimates climate-induced changes in LC (open water, marsh, wet meadow, and woody/shrub) in the Upper Columbia River Wetlands (UCRW), British Columbia, Canada, from 1984 to 2040. An artificial Neural Network (ANN) approach was used with Landsat series archive data from 1984 to 2022 to project seasonal LC change from 2020s to 2040s. Concurrently, hydroclimatic-based models (using air temperature and precipitation to predict river discharge at the UCRW, 1984–2022) were developed (average Nash Sutcliffe: training 0.75 and validation of 0.70) to predict (1984–2040) river discharge forced by Representative Concentration Pathway (RCP) 4.5 and 8.5. The 1984–2022 regression between river discharge and UCRW open water area was forced by RCP scenario river discharge results, calculating open water area for both scenarios. ANN-predicted LC with a Kappa of 0.85 (average of all seasons) for 2020s reference and projected LC, and 0.82 for reference and projected LC change maps (2000s–2020s). From 2020s to 2040s, the ANN projected a reduction (−5 %) of open water areas during late summer (August to mid-September) in the UCRW, consistent with RCP 4.5 forecasts. The peak of the open water area in the UCRW is projected to shift from summer (late-May to July) to spring (April to mid-May) in both RCP scenarios. The projected changing hydrological conditions reduced the marsh area (−1 % to −12 %) and increased the wet meadow (+1 % to +4 %) mostly in the summer and late summer. Meanwhile, woody and shrubby vegetation on the floodplain increased (3 % to 5 %), indicating that the floodplain is projected to dry out.
- ItemUsing bi-temporal lidar to evaluate canopy structure and ecotone influence on Landsat vegetation index trends within a boreal wetland complex(MDPI, 2025) Aslami, Farnoosh; Hopkinson, Christopher; Chasmer, Laura; Mahoney, Craig; Peters, Daniel L.Wetland ecosystems are sensitive to climate variation, yet tracking vegetation type and structure changes through time remains a challenge. This study examines how Landsat-derived vegetation indices (NDVI and EVI) correspond with lidar-derived canopy height model (CHM) changes from 2000 to 2018 across the wetland landscape of the Peace–Athabasca Delta (PAD), Canada. By comparing CHM change and NDVI and EVI trends across woody and herbaceous land covers, this study fills a gap in understanding long-term vegetation responses in northern wetlands. Findings show that ~35% of the study area experienced canopy growth, while 2% saw a reduction in height. CHM change revealed 11% ecotonal expansion, where shrub and treed swamps encroached on meadow and marsh areas. NDVI and EVI correlated significantly (p < 0.001) with CHM, particularly in shrub swamps (r2 = 0.40, 0.35) and upland forests (NDVI r2 = 0.37). However, EVI trends aligned more strongly with canopy expansion, while NDVI captured mature tree height growth and wetland drying, indicated by rising land surface temperatures (LST). These results highlight the contrasting responses of NDVI and EVI—NDVI being more sensitive to moisture-related changes such as wetland drying, and EVI aligning more closely with canopy structural changes—emphasizing the value of combining lidar and satellite indices to monitor wetland ecosystems in a warming climate.
- ItemWildfire as a major driver of recent permafrost thaw in boreal peatlands(Nature Portfolio, 2018) Gibson, Carolyn M.; Chasmer, Laura; Thompson, Dan; Quinton, William L.; Flannigan, Mike D.; Olefeldt, DavidPermafrost vulnerability to climate change may be underestimated unless effects of wildfire are considered. Here we assess impacts of wildfire on soil thermal regime and rate of thermokarst bog expansion resulting from complete permafrost thaw in western Canadian permafrost peatlands. Effects of wildfire on permafrost peatlands last for 30 years and include a warmer and deeper active layer, and spatial expansion of continuously thawed soil layers (taliks). These impacts on the soil thermal regime are associated with a tripled rate of thermokarst bog expansion along permafrost edges. Our results suggest that wildfire is directly responsible for 2200 ± 1500 km2 (95% CI) of thermokarst bog development in the study region over the last 30 years, representing ~25% of all thermokarst bog expansion during this period. With increasing fire frequency under a warming climate, this study emphasizes the need to consider wildfires when projecting future circumpolar permafrost thaw.