Biological assessment of dune restoration in south Texas

Abstract

A dune restoration program was initiated by the City of South Padre Island, Texas in 2010 consisting primarily of plantings of Sea Oats, Uniola paniculata, and Bitter Panicum, Panicum amarum, and has continued annually thereafter. These restoration efforts were evaluated by comparing selected metrics of ecosystem structure and function among reference and restoration plots ranging in age (time after planting) from 2 to 5 years. Plant and animal communities were examined using a combination of quadrat sampling, funnel traps, pit-falls, and sweep nets. Soil organic content and soil electrical conductivity were also measured. Dune volumes and heights were calculated using a 2013 Lidar DEM. Plant communities were similar across 2 and 4 year-old plots but differed markedly among 2 and 5 year-old plots and between all restoration plots and undisturbed reference plots. After 5 years, restoration plots had 15 plant species, while reference plots had 19. Animal communities followed a similar trend in which all restoration plots differed from the reference plots with the exception of 5 year-old plots which were similar. More time seems necessary for restored dunes to accumulate soil organic matter at levels similar to natural dunes which is still about three times higher. There was a significant positive correlation between plot age and dune heights. These results suggest the native dune plant revegetation as implemented by the City of South Padre Island from 2010 to 2015 is successful in fostering plant and animal community succession and potentially increasing coastal resiliency.