Hopkinson, Christopher

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https://opus.uleth.ca/handle/10133/4541

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Browsing Hopkinson, Christopher by Subject "Biomass"

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    Partitioning carbon losses from fire combustion in a montane valley, Alberta Canada
    (Elsevier, 2021) Gerrand, S.; Aspinall, Jesse; Jensen, T.; Hopkinson, Christopher; Collingwood, A.; Chasmer, Laura
    Direct carbon (C) emissions from wildland fires have been difficult to quantify, especially in montane environments where sites are difficult to access. Here we examined pre-fire C partitioning and losses in a southern Canadian montane valley ecosystem, in Waterton Lakes National Park, Alberta Canada. The objectives of this study were to: (a) quantify the C loss due to combustion at a moist riparian site compared with a dry undulating upland site and (b) compare C loss observations to an active multi-spectral lidar remote sensing index. C losses from wildfire were consistently greater at the wet riparian site compared with the dry valley site. Average soil C losses were 92.92 Mg C ha −1 (st. dev. ± 48.60 Mg C ha −1) and 58.05 Mg C ha −1 (st. dev. ± 37.19 Mg C ha −1). Average tree C losses were 114.0 Mg C ha −1 (std.dev. ± 9.9 Mg C ha −1) and 86.9 Mg C ha −1 (std.dev. ± 13.5 Mg C ha −1) respectively. C losses from trees were greater than soils, where trees lost 55% (moist riparian ecosystem) and about 60% (drier valley site) of C during combustion. Using post-fire multi-spectral airborne lidar data, we found that increased proportion of charred soils were significantly related to enhanced reflectivity in SWIR, resulted in more negative active normalised burn ratio (aNBR) results, indicating enhanced burn severity. Increased proportional cover of regenerating vegetation resulted in less negative aNBR both at the drier site, though no significant relationships between aNBR and charred vs. vegetated results were observed at the moist riparian site. No significant relationship was observed between depth of burn/soil C loss and aNBR derived from lidar data, indicating potential limitations when using burn indices for below canopy burn severity. The use of multi-spectral lidar may improve understanding of below canopy fire fuels and C losses in optical imagery, which often occludes these important components of fire ecology. The results of this research improve understanding of C losses associated with wildland fire in montane ecosystems that have undergone fire suppression and management by Euro-American colonizers for over 100 years.
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    Post-fire vegetation regeneration during abnormally dry years following severe montane fire: southern Alberta, Canada
    (Elsevier, 2025) Aspinall, Jesse; Chasmer, Laura; Coburn Craig; Hopkinson, Christopher
    Fire 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.