Restoration of Red Spruce Forest: Understory Plant and Soil Responses to Canopy Gaps at Roan Mountain, NC
- WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
- Thomas Hennessey (Creator)
- Institution
- Western Carolina University (WCU )
- Web Site: http://library.wcu.edu/
- Advisor
- Beverly Collins
Abstract: Red spruce-Fraser fir dominated forests are considered threatened in the southern Appalachian Mountains and are known to support a variety of rare and endemic species. Their range has diminished greatly due to human disturbance over the past century, and questions about their long-term persistence and ecosystem-level role as local carbon sinks have led to interest among land managers in assisting their health and regeneration. Spruce and fir seedling survival and growth may depend on soil conditions (e.g. disturbance, microbial activity) and environmental conditions (e.g. temperature, light) that affect resource availability. This study explored the effectiveness of 10 m-diameter and 3.5 m-diameter canopy gaps in boosting seedling growth and recruitment in one such forest at Roan Mountain with the goal of identifying a successful management strategy that mirrors historically natural processes. To investigate gap effects, I tracked seedling survival in gaps and uncut areas periodically from June to October 2021 and measured soil respiration weekly in the same areas. Soil respiration, or carbon exchange (CO2 efflux) between the spruce-fir stand and surrounding environment, was used as an index for soil conditions and activity that may underlie seedling response. In addition to gap effects, soil disturbance (scarification) effects on soil respiration were investigated to account for possible understory response to increased foraging by the federally endangered Carolina northern flying squirrel. To measure soil respiration, one soil ring was inserted in the center of each measurement area and a second was inserted beside it with duff removed in the top few centimeters of soil. Each 10 m gap was also given a second set of rings on the northern edge to test the effects of different angles and amounts of light. Spring, midsummer, and fall seedling census found that seedling survival was greater than 95% across the growing season in all gaps and uncut areas and that visible seedling growth was negligible (~0.5-1 mm). Weekly soil CO2 efflux observations indicated that large gaps had lower efflux than both small gaps and uncut forest, but also that edges of large gaps had significantly higher efflux than centers of large gaps when soil was scarified. Strength of gap and within-gap-position effects also varied significantly with time when soil was scarified. Time was an important factor in soil CO2 efflux with both disturbed and undisturbed soil. Results suggest that canopy gaps 10 m in diameter may have a negative effect on red spruce and Fraser fir seedling growth that diminishes toward the gap edge, and that smaller 3.5 m gaps may be a beneficial management tool for stimulating seedling activity in these ecosystems. Additionally, foraging-related soil scarification tended to impact soil respiration negatively, meaning that increased flying squirrel foraging could harm seedling regeneration. Connections between gap effects and soil scarification will therefore be important to monitor in the future depending on the extent to which restoration practices impact spruce-fir forest and Carolina northern flying squirrel populations.
Restoration of Red Spruce Forest: Understory Plant and Soil Responses to Canopy Gaps at Roan Mountain, NC
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Created on 6/1/2022
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Additional Information
- Publication
- Thesis
- Language: English
- Date: 2022
- Keywords
- Ecology, Forestry, Natural Resource Management
- Subjects
- Forests and forestry
- Natural resources—Management
- Ecology
- Red spruce
- Forest canopy gaps