Fire and tree recovery on seismic lines

  • Author / Creator
    Filicetti, Angelo T.
  • The world’s forests are highly fragmented by linear disturbances, many of which have failed to recover decades after abandonment. Lack of recovery is common, most notably in xeric and hydric forests. Possible mechanisms for this lack of recovery are: life history traits of local species, lack of recent wildfires that encourage tree regeneration, soil compaction, and simplification of microtopography that leads to a loss of microsites for tree establishment. The persistence of these disturbances affects biodiversity, but of particular concern in Canada’s boreal forest are the detrimental effects on threatened woodland caribou. Although natural regeneration of trees on linear disturbances occurs in some places (passive restoration), it is not considered to be an effective recovery strategy for restoring disturbed habitat of woodland caribou. This has led to active restoration efforts of silviculture and tree planting where costs can exceed $12,500 (CAD) per km of seismic line. Current restoration models do not, however, consider wildfires that although destroy planted trees, can also initiate early seral conditions that favor natural regeneration. Here, I examine patterns in passive restoration, with and without recent wildfires, possible mechanisms for places that lack recovery, and the effectiveness of active restoration treatments of seismic lines in northern Alberta, Canada. Life history traits, such as fire serotinous-cones, suckering, and shade tolerance, best explain patterns of recovery for many sites. Overall, regeneration density and tree heights on most lines met suggested restoration guidelines (1000 stems/ha and 5-m height) within a 20-year period. Seismic lines in uplands sites may experience moderate levels of compaction, but it did not appear to affect regeneration rates. Except for fens, wildfires promoted increases in tree regeneration density and height on seismic lines, but this requires waiting for places to burn. Because fens burn less frequently and typically experience lower fire severity, as well as losing microtopography during line clearing, tree recovery here is slower than elsewhere, but may still be suitable considering tree density and heights here are naturally lower. Active restoration treatments of seismic lines, and in particular in peatlands with mounding, promoted natural tree regeneration and tree growth over the short-term (< 5-yrs) thus overcoming site limitations (most notably the loss of microtopography), but longer-term studies are needed to assess their long-term success and cost-benefit of passive restoration strategies that depend on natural regeneration and in many cases wildfires.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • 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.