Graduate Thesis Or Dissertation


Assessing Post-fire Tree and Understory Vegetation Response to a Mixed-severity Fire Gradient in the Klamath Mts., Oregon, USA Public Deposited

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  • Severe wildfires are increasing in the western United States, impacting vegetation structure, and in turn, forest regeneration conditions. These wildfires are also raising a substantial amount of scientific and management concern regarding the resilience of forested ecosystems, or the ability of the ecosystem to return to a pre-fire condition. This is particularly uncertain with respect to the gradient in fire severity common in wildfires today. Surveying tree regeneration and understory plant community response in post-fire environments is one important method for assessing the resilience of conifer-dominated forests. In this context, I assessed the abundance of mixed-conifer tree regeneration and understory vegetation response two years post-fire following three mixed-severity fires in the Klamath Mountains ecoregion, Oregon, USA. First, I examined the influence of two LiDAR-derived metrics (pre-fire average stand height and distance to surviving trees), heat load, and fire severity on the abundance of regenerating conifer seedlings. Basal area mortality and pre-fire average stand height were the significant variables impacting mixed-conifer regeneration, but pre-fire stand height was a subtle modifier compared to basal area mortality. I concluded that overstory tree mortality appears to be beneficial to future conifer regeneration when sufficient seed sources are still available. Second, I aimed to improve our knowledge of short-term post-fire understory response and evaluated differences in species richness and understory plant community composition based on the fire severity gradient. I observed increasing species richness with the increasing basal area mortality. Additionally, understory vegetation groups were separated mainly between unburned and low-severity groups, versus moderate-and high-severity groups. Overall, I observed that fire disturbance significantly impacted post-fire tree regeneration and understory vegetation response, and observing and understanding these changes created by disturbance is highly important for the conservation and management of ecosystems.
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  • This research is supported by the Ministry of National Education of Türkiye.
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