Date of Award

Spring 5-1-2022

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Amber Roth

Second Committee Member

Malcolm Hunter

Third Committee Member

Robert Seymour

Additional Committee Members

Brian McGill

Abstract

Active forest management alters the resources available to forest-obligate species. Large-scale intensive management practices where timber production is the primary objective can lead to notable ecological changes in forest ecosystems. A key concept of ecological forestry is to design forest management activities to emulate natural disturbance regimes as a way to maintain the ecological integrity of forests. The Acadian Forest Ecosystem Research Program (AFERP) was undertaken as an experimental demonstration of management reflective of the region’s disturbance regime, which typically produces small canopy gaps. AFERP includes nine research areas assigned to three silvicultural treatments: unharvested control, small gap (expanding-group selection with reserves), and large gap (irregular expanding-group shelterwood with reserves). Initial harvests took place in the winter of 1995 and two subsequent harvests have been conducted, every 10 years, making AFERP the longest running experimental study of these silvicultural treatments. Using a territory mapping approach, the avian assemblage was surveyed from 1995-1998 and again in 2020-2021. A significant decline in the abundance and diversity of birds was noted between the early set of surveys and the most recent surveys, regardless of treatment. Despite these declines, composition of the avian assemblage remained similar among treatments. The majority of bird species found on territory mapping surveys are declining in abundance region-wide with species-specific changes in abundance at AFERP mirroring those observed at larger scales. These results indicate that the natural disturbance-based silviculture systems studied here retained the mature forest bird assemblage over the course of multiple harvest entries. Natural disturbance-based forest management has the potential to meet the objectives of many landowners.

Retention of mature trees within harvested gaps is a component of ecological forestry as these trees support natural regeneration and promote structural diversity post-harvest. At present three types of harvests gaps exist at AFERP: small, expanded-small, and large. Retention, in both the form of long-term reserve trees and overwood, is present in each gap type. Avian use of these retention trees was recorded via observational surveys conducted in each gap type. Avian preference for tree type, gap type, and tree type within each gap type was calculated using a Vanderploeg-Scavia index for each of the nine bird species most frequently observed during observational surveys. Birds generally avoided small gaps and preferred larger gap sizes; however small gaps are a necessary part of the silvicultural system. Bird preferences for tree type was stronger than for gap types, each bird species most strongly preferred a different type of tree and those preferences were broadly consistent with the forest type associations of each species. All nine bird species are forest-obligates and their use of retained trees within gaps indicates that these trees act as important resources for forest birds in areas where such resources might not otherwise exist. These results support selecting a diverse set of tree species for retention within harvested gaps in order to support a diverse group of forest birds.

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