Alexander Lanti-Traikovski | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Alexander Lanti-Traikovski. This seminar is open to the general public to attend.

Zoom Link: https://ualberta-ca.zoom.us/j/92419446647

MSc with Dr. Scott Nielsen

Thesis Topic: Regional-scale hydrologic settings buffer black spruce regeneration in the presence of post-fire droughts

Abstract:

Climate change is increasing the frequency of droughts and wildfires, reducing tree recruitment, and altering post-fire species composition. In Canada’s western boreal forests, post-fire recruitment, particularly of coniferous species like black spruce, has declined in recent decades to the benefit of early-successional species like jack pine and trembling aspen. Boreal peatlands may stave off such structural and compositional shifts by supplying groundwater to adjacent forests. The degree to which peatlands buffer upland forests may therefore depend on topographic position and soil texture, factors that govern groundwater connectivity. In this study, I examined how these topoedaphic factors influence upland tree regeneration from post-fire drought. Since higher-positioned peatlands are more mostly fed by precipitation and thus represented mostly as bogs, they are more vulnerable to drought than regionally fed fen-like peatlands at lower topographic positions. I therefore hypothesized that regenerating forest structure and composition at lower topographic positions would be buffered from post-fire drought across a range of soil textures. Specifically, I predicted that tree density and volume of drought-sensitive black spruce should decline as topographic position increases, favoring instead jack pine and aspen. I tested this by measuring 5 – 20-year-old post-fire stands that experienced either wet or dry post-fire climate conditions in Alberta’s boreal forest Study sites spanned local and regional topographic position gradients. I used generalized linear mixed effects models to test for interactions between these local and regional topographic positions, soil texture, and post-fire drought. I found that post-fire drought reduced the proportion of regenerating black spruce at high regional topographic positions in both fine- and coarse-textured soils, while total regeneration (stem density), tree volume (basal area), and species of jack pine and aspen were not affected. This study highlights that hydrologically well-connected areas of Alberta’s boreal forest may act as refugia from drought and fire for drought-intolerant black spruce, and that more predominant upland jack pine and aspen species appeared to be resilient under the current fire regime. Larger-scale hydrological dynamics therefore interact with forest regeneration and should be considered to identify areas that may resist altered post-fire trajectories.