Avian Guano as a Nutrient Input to Cliff-Face Ecosystems in Western North Carolina

Terrestrial cliff-face ecosystems are unique habitats that harbor diverse vegetational communities and an array of animal species. However, fundamental processes such as nutrient cycling in cliff-face ecosystems remain poorly understood. Cliff-face vegetative communities receive some nitrogen through atmospheric deposition, but few other nutrient-linkages have been explored. Seabirds are a well-established vector of nitrogen subsides between marine ecosystems and coastal cliffs, and I document a similar nutrient transfer between highly productive forest ecosystems and nutrient-poor terrestrial cliffs. Like seabirds, terrestrial cliff-nesting birds excrete nitrogen-rich guano at cliff nest sites, subsequently increasing nitrogen (N) availability below nesting sites. This study investigates a fundamental ecosystem process on cliffs, nitrogen cycling, while also exploring a potential link between terrestrial forest and cliff-face ecosystems in western North Carolina.To measure the community effects of a potential nitrogen subsidy, I compared cliff-face N levels, vascular plant, bryophyte and lichen diversity between the paired vertical transects. My data indicate higher ammonium levels below nests on the cliff-face (p<0.05), and differences between vegetation community composition below nests and on adjacent areas on control transects (p<0.05). Thus, nitrogen levels below raptor cliff nests are elevated enough to cause vegetation community composition shifts in terrestrial cliff-face ecosystems.