Year of Award

2022

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Forestry

Department or School/College

W.A. Franke College of Forestry and Conservation

Committee Chair

Cara Nelson

Commitee Members

Robert Keane Andrew Larson David Patterson

Keywords

Pinus albicaulis, ecological response, prescribed burning, mechanical cutting, ecological restoration, wildfire

Subject Categories

Forest Management | Other Forestry and Forest Sciences

Abstract

The field of ecological restoration is growing rapidly, increasing the need for reliable and generalizable information on the impacts of management interventions aimed to be restorative. Prescribed burning and mechanical cutting have been proposed as primary strategies for restoration. However, there is limited information on their efficacy and effects in subalpine forest types, suggesting that monitoring to inform adaptive management is a priority need. I used data from a 15-year, replicated before-after-control-impact (BACI) study on Pinus albicaulis (whitebark pine) restoration to assess the ecological effects of prescribed burning and mechanical cutting, with and without subsequent unplanned wildfire, as well as the efficacy of the monitoring design. Mature tree mortality was high across all study units (77-100%), but neither treatment type nor wildfire were significant predictors of mortality. Similarly, I was unable to detect any effects of treatments or wildfire on P. albicaulis basal area, which declined over time across all study units. However, I found a significant effect of treatment on basal area for two (Pinus contorta and Picea engelmannii) of the three competing conifer species. At Bear Overlook, the site not affected by wildfire, P. contorta basal area change varied significantly between the two treatment units; it decreased by 2.1 m2ha-1 in the burn-only unit but increased by 2.4 m2ha-1 in the prescribed burn with mechanical cutting unit; however, neither treatment was significantly different from the control unit. In contrast, at Beaver Ridge, the prescribed burn with mechanical control treatments, both with and without wildfire, resulted in significant reductions of P. contorta basal area (by 9.8 m2ha-1 and 4.1 m2ha-1, respectively), compared to the untreated control (which did not experience wildfire), which increased by 1 m2ha-1. For P. engelmannii, at Bear Overlook, the site not affected by wildfire, basal area increased after treatment (by 10.3 m2ha-1 and 2.6 m2ha-1 in the burn-only and prescribed burning with mechanical cutting, respectively), but these increases did not differ from changes in the control unit (7.2 m2ha-1). Pinus albicaulis seedling density decreased across both sites and all treatments, however, response to treatment was not statistically significant, while response to wildfire was. The most precisely estimated variable was basal area with a 34% margin of error, followed by mortality (47%) and seedling density (71%). Overall, my findings reveal that the restoration treatments did not affect P. albicaulis mature tree mortality, basal area or seedling density, and were not consistently effective at reducing pressure from competing conifers 15-years after treatment. Although the study utilized best practice design (BACI) and had a relatively large number of replicates (n= 5), loss of study sites due to wildfire coupled with low precision of estimation in field measurements limited power of detection, and highlights the need for large-scale long-term monitoring networks and innovative sampling designs to improve understanding of the efficacy and effects of restoration treatments in P. albicaulis and other degraded forest ecosystems.

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© Copyright 2022 Enzo Paolo Martelli Moya