Mack Thetford

Distance from the Gulf Influences Survival and Growth of Three Barrier Island Dune Plants

Abstract After hurricane overwash, restoration of dune ecosystems requires information on when, where, and how to replace plants removed by storms. Survival and subsequent growth of Schizachyrium maritimum (Chapman) Nash, Morella cerifera (L. Small), and Ceratiola ericoides Michx., transplanted at increasing distances from the Gulf of Mexico (92, 124, 179, and 200 m landward of the Gulf) with increasing protection from salt spray and desiccating winds by developing dunes, were evaluated. Survival and growth was followed for 15 months. Schizachyrium maritimum survival and growth was high regardless of distance from the Gulf. Ceratiola ericoides and M. cerifera did not survive when planted 92 m from the Gulf behind embryo dunes approximately 0.5–1 m tall. Foliage loss was noted at all distances but survival and regrowth were higher at 170 and 200 m behind two to three ridges of embryo dunes 0.5–1 m tall.

Partitioning of applied 15N fertilizer in a longleaf pine and native woody ornamental intercropping system

The cultivation of ornamentals to produce woody floral products—the fresh or dried stems that are used for decorative purposes—may be an attractive option for southeastern landowners looking to generate income from small landholdings. Since many shrubs native to the understory of the longleaf pine (Pinus palustris Mill.) ecosystem have market potential, one possibility is the intercropping of select species in the between-row spacing of young longleaf pine plantations. The objective of this study was to evaluate how interspecific competition affects the fate of 15N fertilizer when American beautyberry (Callicarpa americana L.), wax myrtle (Morella cerifera (L.) Small) and inkberry (Ilex glabra (L.) A.Gray) are intercropped with longleaf pine. Nitrogen derived from fertilizer (NDF), utilization of fertilizer N (UFN) and recovery of fertilizer N (RFNsoil) were compared between agroforestry and monoculture (treeless) treatments to assess the effects of competition. Results varied by species, with NDF being higher for C. americana foliage and lower for all M. cerifera tissues in the agroforestry treatment. No effect was observed for I. glabra. UFN was lower for all species in the agroforestry treatment. RFNsoil was higher in the agroforestry treatment for I. glabra, but no treatment effects were observed for C. americana or M. cerifera. Overall, while it is clear that interspecific competition was present in the agroforestry treatment, the inefficiency of fertilizer use suggests that nitrogen was not the most limiting resource. Management interventions, particularly those that address competition for water, will likely be critical to the success of this system.

Influence of Seasonal Changes and Shifting Substrate on Survival of Restoration Plantings of Schizachyrium maritimum (Gulf Bluestem) on Santa Rosa Island, Florida

ABSTRACT Miller, D.L.; Thetford, M.; Dupree, J., and Atwood, L., 2014. Influence of seasonal changes and shifting substrate on survival of restoration plantings of Schizachyrium maritimum (Gulf bluestem) on Santa Rosa Island, Florida. Environmental gradients on barrier islands are modified by the loss of dunes as a result of hurricane overwash. The success of restoration plantings in posthurricane landscapes is determined by abiotic conditions, including seasonal and spatial gradients of wind speed and substrate transport encountered before dune redevelopment. The response of Schizachyrium maritimum, a dominant, sand-trapping, dune-forming grass of the northern Gulf Coast to month of planting, sand manipulation, and plant spacing was investigated on Santa Rosa Island, Florida. This grass is also a valuable food for endangered beach mice. Seasonal plantings were initiated in 4 months (November 2005, February 2006, June 2006, and August 2006) at each of six sites. For each site and each planting date, plots were split by plant spacing (30 or 45 cm between plants) and again by two sand manipulation regimes (natural sand accumulation or sand level at 3 cm). Sand surface levels were determined and manipulated every 2 weeks. Plant survival and growth were recorded September 2006 and July 2007. Plant survival and growth were greatest for summer plantings, particularly June plantings. Sand burial by natural accumulation did not result in plant death. Most plant death, particularly for November and February plantings, was associated with root exposure and sand loss around transplants. Closer spacing appeared to slow sand loss and plant death for November plantings. Planting of S. maritimum should be restricted to summer months, preferably June, and where sand loss can be minimized by use of mulch or other sand stabilizing methods.

Germination and Predation of Quercus geminata and Quercus myrtifolia Acorns on Santa Rosa Island, Florida

ABSTRACT Tobing, S.L.; Thetford, M., and Miller, D.L., 2018. Germination and predation of Quercus geminata and Quercus myrtifolia acorns on Santa Rosa Island, Florida. Scrub oak species are an important component of barrier island and xeric mainland scrub ecosystems. Limited recruitment of scrub oaks has been noted on barrier islands. This study evaluated several factors believed to alter germination of the scrub oak species Quercus geminata (sand live oak) and Quercus myrtifolia (myrtle oak) along interior dune fields and swales of Santa Rosa Island in the western panhandle of Florida. Influences of dune-field microrelief (interdunal swale or low-lying dune), vegetation cover (vegetated and unvegetated), and seed placement (buried and surface) on germination of acorns were analyzed. Predation of acorns with and without protection from nonburrowing herbivores (open-bottom cage and no cage) was also evaluated. Acorn predation was high. Less than 1% of Q. myrtifolia acorns were recovered outside cages. Only 33% of Q. geminata acorns were recovered outside of cages, with acorn loss reduced only by burial. Burrowing beach mice were able to access acorns within cages. Recovery inside cages was also greater when acorns were buried. Germination of Q. geminata acorns was 15% and was greatest when acorns were buried but was not influenced by microsite or vegetation cover. Germination of Q. myrtifolia was 74% and greater when buried but similar regardless of microsite and vegetation cover. Scrub restoration strategies to increase germination of these two scrub oak species would benefit from an approach that implements direct seeding (burial) in mesic microsites, while sites with strong predator pressure would further benefit from addition of physical protection from seed predators.

Effect of Polyacrylamide Gel on Woody Plant Establishment in Barrier Island Swales

ABSTRACT: Increased hurricane frequency and intensity and residential and commercial development are contributing to loss of maritime forests, coastal hammocks, and scrub dunes. Barriers to natural regeneration necessitate active restoration. We evaluated the survival of woody species planted in ephemeral barrier island swales on Santa Rosa Island, Florida, in an effort to restore barrier island scrub and pine forest lost in recent hurricanes. Contractors planted sand live oak (Quercus geminata) on swale ridges, inkberry (Ilex glabra) on swale mid-slopes, and slash pine (Pinus elliottii) in swale depressions. Polyacrylamide gels are often used to increase transplant survival in the drought-prone, sandy environments. To assist us in evaluating the efficacy of these gels, contractors planted 10 plants with gel and 10 without for each swale, position, and woody species. We followed plant survival for 21 months and measured changes in plant height after one year. Polyacrylamide gel did not significantly affect survival of slash pine or sand live oak. Less than 25% of slash pine and sand live oak survived after 21 months. We found initial survival of inkberry was greater with than without gel, but plant death continued; and after eight weeks, we found no difference in survival for inkberry planted with and without gel. Inkberry survival declined to < 5% at the last evaluation. Changes in plant height were also not affected by Polyacrylamide gel. We do not recommend the use of Polyacrylamide gel to replace supplemental water or to replace the planting of deeply rooted plants on barrier islands.