Barrier Island Dune Vegetation in the Southeastern United States: Future Survival at
the Land-Sea Interface
The land-sea interface is a dynamic environment that has drawn the attention of plant biologists since the inception of the field of ecology. Few areas exhibit such distinct zonation patterns in response to abiotic factors including salt spray, overwash, low water content of the substrate, low nutrient availability, high light intensity, abrasion and episodic burial by sand. Although not reviewed in the past twenty-four years, an extensive body of ecological literature exists for the coastal southeastern U.S. including work that focuses on dune stabilization through beach fencing and revegetation. In contrast, little work has been conducted using modern ecophysiological methods first developed in the 1970s. These methods, along with advances in micrometerological instrumentation, allow today’s researchers to more precisely measure abiotic microenvironments and corresponding plant physiological processes in response to daily, seasonal and episodic stress factors. From these studies, predictions can be made concerning the future of dune plant populations along the southeastern United States in relation to climate change impacts such as increased sea level or the frequency and intensity of storm events. Here we review existing ecological and ecophysiological literature on coastlines, predictions for future dune plant populations, and address new avenues of research.
Limited Seed Set and Germination Cues of the Federally Endangered Perennial,&Nbsp; Thalictrum cooleyi , Ahles
Thalictrum cooleyi Ahles, is a dioecious species, endemic to the coastal plain of the southeastern US, listed as federally endangered in 1989. We lack biological knowledge for Thalictrum cooleyi, e.g., its reproductive ecology, critical to prioritize and effectively implement conservation efforts. During the summer of 2013, I documented: 1) sex ratios at three NC sites, 2) potential pollen limitation, and 3) average seed set in the field. Deviations from a 1:1 functional sex ratio were found at two of the three sites surveyed. I performed a pollen supplementation experiment to compare seed set in 37 females at three sites. Percent seed set was 67% in hand pollinated flowers, greater than in open pollinated controls (35%), an indication of pollen limitation. Average seed set per flower in the field was 62% at one site surveyed (n = 226). In comparison, average seed set per flower was 45% for plants grown without assisted pollination inside environmental growth chambers and a greenhouse (n = 368). Seed mass ranged from 1.22-6.01 mg (mean ± SE = 3.02 ± 0.02, n = 1171). Preliminary data suggest seeds are dormant at maturity. I also selected seeds of known mass to test for factors which might influence germination: seed age, exposure to gibberellic acid, length of cold stratification, and light exposure during incubation. My results suggest that low seed set from pollen limitation, and complex seed dormancy and germination cues, coupled with habitat degradation, limit successful sexual reproduction of Thalictrum cooleyi.
1 Biology, East Carolina University, NC; 2 Biology, East Carolina University, NC; 3 Biology, East Carolina University, NC
182 • Rebecca K. McKee1, Kristen K. Cecala2, Michael E. Dorcas1
The Effect of Bycatch Reduction Device Presence and Orientation on Diamondback Terrapin Capture and Behavior
Diamondback terrapins (Malaclemys terrapin) have experienced declines throughout their range, and accidental mortality in crab traps is a significant conservation concern. To minimize the risk of terrapins entering crab traps, researchers have suggested the use of bycatch reduction devices (BRDs) to reduce the size of crab trap openings and thereby exclude terrapins from entering crab traps. Despite these recommendations, few studies have observed terrapin behavioral interactions with BRDs and the effectiveness of these devices at preventing entry of smaller terrapins into crab traps. The objective of our study was to determine the effect of BRDs and bait on blue crab and terrapin behavior and overall capture abundance. We observed terrapin behavior when crab traps were baited with a variety of commonly used baits and with vertical and horizontal installation of BRDs. Overall, terrapins investigated crab traps more frequently when the traps were baited with mackerel versus chicken or crab, and the terrapins were captured more frequently when BRDs were not installed on the trap. The presence of the BRDs also increased the length of time necessary for a terrapin to enter the traps and decreased the proportion of entries relative to the number of investigations. Understanding these interactions will better allow us to recommend regulations to prevent the continued decline of terrapin populations due to blue crab fisheries while maintaining or improving the blue crab catch.
1 Dept of Biology, Davidson College, Davidson, NC; 2 Dept of Biology, Sewanee: The University of the South, Sewanee, Tennessee
183 • Joanna E. Hawley Howard1, Rob F. Baldwin1, Amber L. Pitt2, Elizabeth D. Baldwin1
