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Community assemblages provide insight into ecosystem processes, both spatially and temporally. They interact with biotic and abiotic factors that vary with habitat structure, influencing community composition. Ecological theory demonstrates that species have the potential for a wide fundamental niche, but habitat range may be restricted by factors exposed to species in their realized niche. In barrier island ecosystems, edaphic and environmental characteristics (e.g. elevation and distance to shoreline) are major drivers determining where and how plant communities establish. Physical stressors, such as salt stress and drought influence community grouping and can alter plant function within the environment. With projected increases in sea level rise and storm disturbance it is important to understand how plant communities are organized across barrier islands, as most studies are limited to dune habitats and not inland plant communities.
I analyzed plant communities across environmental gradients on a Virginia barrier island from dune to marsh. I established transects on Hog Island and assessed soil characteristics (i.e. carbon, nitrogen, pH), species composition, percent cover and specific leaf area. Elevation and distance to shoreline were obtained using recent Lidar imagery. Bray-Curtis ordination showed that position in landscape is an important driver in structuring dominant species such as the grasses Ammophila breviligulata, Spartina patens, and S. alterniflora. Elevation (r = -0.511) and distance to shoreline (r = 0.551) both show relationships with species composition and distribution across the island. Elevation was important in structuring dominant community types (i.e. dune building and marsh plants). Mantel test was used to determine if relationship exists between species cover and measured edaphic/environmental factors (r = 0.299, p > 0.0001). Percent carbon found in soil within plots was weakly related with distance to the inner portion of the island (r = 0.56). This reflects biotic processes that occur in interior portions of the island. There was no obvious relationship with percent nitrogen due to extremely low levels across the ecosystem. Understanding community structure across coastal ecosystems is necessary for predicting how shorelines and interior communities will be affected with projected sea level rise and increases in storm frequencies. An updated understanding of how biotic and abiotic drivers of community composition will provide information into predictive modeling of plant community and ecosystem level responses to change.
Ecology, Barrier Islands, Physiological Ecology
Botany | Plant Biology
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