COS 23-3 - Development of scrub vegetation in a former agricultural site through 23 years after planting

Tuesday, August 9, 2016: 8:20 AM
Floridian Blrm A, Ft Lauderdale Convention Center
Paul A. Schmalzer and Tammy E. Foster, Ecological Program, IMSS, Kennedy Space Center, FL

Florida scrub is a vegetation type unique to Florida that supports many rare plants and animals. Most scrub has been lost to urban and agricultural development. Formerly cultivated sites offer an opportunity to restore scrub. Observations indicate that scrub does not reestablish in former citrus groves on scrub soils on Merritt Island, Florida. Instead exotic species, particularly grasses, and some weedy native species occupy these sites. In 1992, we began a project to test whether scrub species could be restored to a former grove site and whether scrub vegetation composition and structure could be reestablished over time. Scrub oaks (Quercus chapmanii, Q. geminata, Q. myrtifolia) were planted (988/ha) in a 5.6 ha section of a former grove after the site was cleared and treated with herbicide. Additional scrub species (500 Serenoa repens, 300 Lyonia fruticosa, 200 Vaccinium myrsinites, 100 Pinus elliottii var. densa,) were planted in 1993 along with 2000 scrub oaks. We marked a sample of scrub species after planting and determined their survival and growth annually. We established 10 permanent line-intercept transects (15 m length) and recorded vegetation data in two height strata (< 0.5 m and > 0.5 m) annually to determine long-term vegetation changes.


Initial survival of Q. geminata exceeded than that of Q. chapmanii or Q. myrtifolia. Mean height of Q. geminata reached 310 cm by 1999. Six prescribed burns occurred between 2000 and 2010, but 66% of the tagged Q. geminata were not top-killed by any of these fires; all the tagged Q. chapmanii and Q. myrtifolia were top-killed at least once. Q. gemianta not top-killed reached a mean height of 804 cm by 2010. Cover of scrub oaks > 0.5 m increased from 1.3% in 1992 to 65.2% in 2010. However, the vegetation structure of large Q. geminata did not resemble that of native scrub. Large oaks were cut in the fall of 2010, and the site was burned in early 2011. Cutting and burning appeared to stimulate sprouting and clonal spread of Q. geminata. Nonmetric multidimensional scaling (NMS) ordination (axis 1, >0.5 m strata) indicated directional change related to increasing scrub oak cover and time since planting. In contrast, the first axis of NMS ordination of the <0.5 m strata was related to persisting exotic grasses. By 2015 scrub oaks, Pinus elliottii, and Serenoa repens had substantial cover, but exotic grasses remained abundant, constituting a novel intermediate community.