Date of Award

2022

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Natural Resources

First Advisor

Anthony W. D'Amato

Abstract

As non-native forest pests disperse across the United States, the emerald ash borer, Agrilus planipennis (EAB), has emerged as one of the most costly and destructive invaders. In response to EAB, forest management practices, including pre-salvage logging, "phloem reduction" (large ash removal), and strategies to improve future ash regeneration, have been implemented to meet economic, ecological, cultural, and safety objectives. Although many studies have quantified the impacts of EAB on mortality of ash trees (Fraxinus spp.), less is known about the short- and long-term ecological impacts of forest management in response to this pest. In summer 2020, we measured forest structure and composition at sites across New England that included white ash harvests motivated by the threat of EAB impacts. Management responses varied from selective ash removals to capture potential economic losses to group selection harvests designed to recruit new ash cohorts. Informed by our findings, we modeled three approaches to ash management under three potential future climate regimes, along with EAB and natural wind disturbance for a 100-year period in northern Bennington County, Vermont. This dual approach allowed us to examine both the immediate aftermath of forest management responses to EAB, and the future outcomes of these management practices on ash trees and their natural communities, in the context of other important drivers of forest dynamics such as climate change.

In our observational study, we found a lower proportion of white ash basal area in harvested study sites compared to unharvested control sites. However, white ash regeneration at the seedling and sapling stages was higher in harvested than in unharvested plots. In addition, our modeling of ash management practices projected more white and black ash biomass present in 2120 forests when harvests and chemical treatments prioritizing ash retention and regeneration were implemented compared to typical current practices, and less ash biomass in 2120 following more aggressive salvage and pre-salvage harvests removing white ash. Climate also played a significant role in next-century forest composition, as more drastic climate projections compared to current conditions favored warmer-adapted species in the region. Our findings indicate that forest management practices that align with ash species’ silvics, such as the greater light availability needed to successfully recruit new white ash cohorts, can bolster ash regeneration and perpetual presence in New England forests. Although EAB remains a significant threat, our work confirms the importance of implementing a variety of management approaches, supported by recent findings that ash survival and resistance to EAB is more prevalent, and more variable, than previously thought. This work will help inform future management decisions in response to this invasive pest that ensure long-term ecological and economic options are maintained on site.

Language

en

Number of Pages

96 p.

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