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Disturbance is a fundamental ecological force that shapes biodiversity, community composition, and ecosystem function. Human-driven disturbances—such as habitat fragmentation, deforestation, and air pollution—are increasing worldwide, altering ecosystems at unprecedented rates. While ecological research has illuminated many effects of disturbance, significant knowledge gaps remain for underappreciated but ecologically vital organisms, such as lichens. Lichens are obligate symbioses between at least one fungus and one alga or cyanobacterium. As such, they are sensitive bioindicators of environmental change, offering unique insights into ecosystem health due to their responses to stressors such as poor air quality, habitat fragmentation, and deforestation. Yet, their responses to disturbance are complex and not fully understood, particularly in biodiverse regions like the Southern Appalachians. This knowledge gap is relevant to ecosystem health because lichens contribute to nutrient cycling, habitat structure and ecological stability.
This dissertation investigates how lichens respond to anthropogenic disturbances, through examining patterns of lichen species richness, community composition, and functional group variation at multiple scales. The Southern Appalachian Mountains are an excellent study system due to their high biodiversity supported by a range of habitat types and lichen substrate availability. Two chapters of this dissertation analyze the drivers of lichen diversity across the region, using a large dataset built from intensive sampling. The dataset, one of the most comprehensive lichen datasets in North America, uses 899 species documented by over 16,000 voucher specimens collected from 208 one-hectare plots. Two other chapters focus on montane cliffs, unique ecosystems which often serve as ecological refuges for lichens but are increasingly impacted by human activities like rock climbing. The Linville Gorge, a rugged and biodiverse gorge in the Southern Appalachian Mountains of North Carolina serves as the study area for our cliff-based research. Collectively, these findings contribute to a broader understanding of how disturbance shapes ecological systems at different scales and provides actionable strategies to conserve lichen diversity and ecosystem health amidst rapid environmental change.
Chapter one examines the effects of anthropogenic disturbance at the site level on overall lichen richness as well as richness of selected lichen functional groups. Using a habitat quality index as a proxy for disturbance, results show a negative linear relationship between disturbance and species richness: as disturbance increases, lichen species richness decreases. This result contradicts the Intermediate Disturbance Hypothesis and suggests that lichen conservation efforts should prioritize older, less-disturbed forests to maintain lichen diversity. Chapter two evaluates the influence landscape-level anthropogenic disturbance in the form of stand age, fragmentation, and air pollution on lichen community composition throughout the Southern Appalachians. Site-level factors, particularly tree species richness and elevation, emerged as the primary drivers of species richness and community composition, while landscape-level factors, such as nearby developed land, had minimal influence. Surprisingly, air pollution and stand age had no significant influence on lichen community composition. These findings highlight the need to integrate both fine- and broad-scale variables in conservation planning and suggest that protecting tree biodiversity is an important step toward maintaining unique lichen communities.
Chapter three shifts the focus from the whole Southern Appalachian region to an important but understudied ecosystem: montane cliff faces. This chapter reviews the impact of rock climbing on cliff vegetation, including lichens, bryophytes, and vascular plants. We identify inconsistencies in methodology across nineteen climbing studies and propose best practices for standardizing research methods. The best-practices suggested in the paper aim to produce more reliable data to guide plans for managing anthropogenic disturbance on cliffs such as rock climbing. Chapter four investigates the distinct lichen communities on cliffs in the Linville Gorge, comparing them to rock- and soil-dwelling lichens in forests. The cliffs examined included both popular climbing areas as well as unclimbed cliffs within the Linville Gorge. The results demonstrate that cliffs support 20% of regional rock-dwelling lichen diversity, including rare, cliff-specialist lichens absent from surrounding forests. This chapter underscores the ecological importance of cliffs and the need to include them in biodiversity inventories and conservation plans, as well as provides the first lichen checklist for Linville Gorge. Overall, this dissertation advances our understanding of the drivers of lichen diversity and community composition across gradients of disturbance. By identifying key ecological patterns and proposing methods for improved data collection, this work provides data-driven suggestions for lichen conservation and stewardship in the face of environmental change.
