A comparison of residual tree mortality in forest island remnants following wildfire and harvest

• Author / Creator

  Odell, Rosanise

• As forested ecosystems are put under compounding stresses due to the effects of climate change and demand for resources, forest managers must develop innovative ways to utilize natural resources in less-impactful ways. In the boreal forests of Alberta, Ecosystem Based Forest Management (EBFM) is implemented is through emulation of natural disturbances such as wildfire using retention forestry to leave behind patches of intact forest during a harvest, called island remnants. Previous studies have compared residual tree mortality in dispersed retention or partial harvest to reference forests and clearcuts, but not against island remnants created by wildfires. The objectives of this study were the following: 1) examine the effects of disturbance type (fire and harvest) on post-disturbance tree mortality amounts in island remnants compared to reference forest; 2) determine if plots on forest edges experience higher post-disturbance mortality than plots located in the interior of these forests; 3) examine if certain tree species experience higher post-disturbance mortality rates and if this has any relation to disturbance type, island/reference plot or edge effects; 4) determine if tree size predicts mortality rates, and 5) assess if there are any temporal patterns of post-disturbance tree mortality following wildfire and harvest. Post-disturbance tree mortality was calculated by conducting stem surveys of each plot and tree cores were collected from standing snags for dendrochronological analysis. We determined the year of death for snags to determine if EBFM-created island remnants are functioning similarly to wildfire-created island remnants with respect to tree survival. Harvest created island remnants did not exhibit higher residual tree mortality than reference forest or similar sized fire island remnants, however edges of fire islands had higher mortality than fire reference edges. Aspen had overall higher mortality throughout the study area than spruce, and smaller sized trees also had a higher probability of mortality. These results support the continued implementation of retention forestry using island remnants within the scope of EBFM in Alberta and may aid in promoting forest recovery and resilience following disturbances.

• Subjects / Keywords

  • structural retention
  • ecosystem based management
  • tree mortality
  • disturbance emulation
  • harvest retention
  • forest management
  • boreal forest
  • dendrochronology

• Graduation date

  Spring 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-jnen-mm52

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.