Remnant and restored community trajectories following disturbance

Background/Question/Methods

Pine savannas are among the most diverse ecosystems in North America and provide critical habitat for many species but have seen a dramatic decline in size over the past century due to urbanization, logging, and fire suppression. Coastal pine savannas are especially vulnerable to anticipated effects of global climate change. Models of climate change predict rapid sea-level rise along the northern Gulf of Mexico and more intense hurricanes. Restoration of these fragile ecosystems is needed, but the effects of climate change on restored, as well as remnant communities, are unknown. This research aims to compare resilience of remnant and restored plant communities to simulated hurricane disturbance. We hypothesized that species composition of both site types would change following experimental storm surge, and restored communities would follow a different trajectory due to site conditions, particularly invasion by neighboring non-target species. Non-metric multidimensional scaling (NMDS) ordination was used to visualize dissimilarities in composition, and an Analysis of Similarity (ANOSIM) was used to test whether there were significant differences based on the following factors: site type, time, and treatment. 

Results/Conclusions

Results from three compositional surveys (one prior to and two following treatment application) suggest that there was a significant effect of site type on community composition. These differences are likely a result of propagule pressure from neighboring plants within the restored site, including the highly invasive Chinese tallow and Japanese honeysuckle.  Results indicate that there may be several possible alternative compositional trajectories following the onset of restoration in a degraded system. The effects of the storm surge were not significant in either post-treatment survey, suggesting that the disturbance effects are ephemeral or that the communities are tolerant of the disturbance. As climate change unfolds, it will be important to compare the compositional trajectories of remnant and restored communities and determine what environmental factors are most significant in community assembly following disturbance.