Conservation of boreal moth communities in the mixedwood boreal forests of northwestern Alberta: Impacts of green tree retention and slash-burning

• Author / Creator

  Kamunya, Esther W

• Green tree retention (GTR), which involves leaving dispersed or clustered live trees on harvested stands, is being adopted as an alternative to clear-cutting, and to conserve biodiversity on managed forests. This thesis examines the post-harvest (7-10yrs) recovery of boreal moths following retention harvest and slash-burning in the managed mixedwood boreal of northwestern Alberta. Night-flying moths were light-trapped from coniferous (CDOM) and deciduous (DDOM) stands harvested to three retention levels (10%, 20% and 50%), stands harvested to 10% retention and burned (slash-burns), and compared to un-cut control stands that had regenerated from wildfires (~80-140 yrs ago). At the 50% level, moth communities of the DDOM cover-type did not differ from un-harvested stands, but those of the CDOM cover-type were still very different, 8-yrs post-harvest. Retentions at the 20% level were insufficient to promote the recovery of moth communities on harvested stands of both cover-types. The abundances of moths that feed on pioneer plant species in their larval stages were increased while feeding specialists were decreased at both levels of retention. Thus, higher levels of retention are likely required in order to conserve feeding and habitat specialists in the managed mixedwood boreal. Arboreal larval assemblages on trees sampled from harvested stands were not significantly different from those on un-harvested stands. Larval abundance and richness greatly varied among trees of the same species due to tree height, diameter at breast height and the percent crown-cover around individual trees. Retaining single dispersed trees of different species, size and age classes on harvested blocks may therefore help to maintain populations of specialized feeders, albeit in low abundances, through the stand regeneration cycle. Burning slash after harvesting did not promote a recovery of moth assemblages different from that found in low (20%) retention harvest, 8-yrs post harvest, but both forms of disturbance greatly reduced moth abundances and richness compared to unharvested controls. It is likely that fire behavior and intensity is modified in stands where low retention levels have been applied. Hence, prescribed burning aimed at complementing GTR will better achieve conservation objectives as complements to high retention or unharvested forest stands.

• Subjects / Keywords

  • Mixedwood boreal forest
  • Caterpillars
  • Green tree retention
  • Light traps
  • Moths
  • Forest Canopy

• Graduation date

  Fall 2012

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R38W6K

• 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.