Thursday, August 7, 2008
Exhibit Hall CD, Midwest Airlines Center
Eric S. Menges1, Gretel L. Clarke2, Stacy A. Smith3, Carl W. Weekley3, Sarah T. Hamman4 and Nancy J. Bissett5, (1)Plant Ecology Program, Archbold Biological Station, Venus, FL, (2)Biology Department, University of Vermont, Burlington, VT, (3)Archbold Biological Station, Venus, FL, (4)Center for Natural Lands Management, Olympia, WA, (5)The Natives, Inc., Davenport, FL
Background/Question/Methods We describe initial results from an experimental Florida scrub restoration. We are restoring former pasture and degraded scrub sites, and contrasting vegetation to that of nearby reference sites on the same soil, same elevations, and comparable landscape positions. Before beginning the study, we identified key attributes of high-quality Lake Wales Ridge scrub (e.g. shrub cover 60-90%, bare sand cover 10-40%) as restoration objectives. Pre-treatment (2005) vegetation and soil surveys showed substantial differences in key attributes among reference sites (e.g. extensive soil crusts, lowest soil nutrients, lowest exotic species cover), disturbed scrub (highest bare sand cover, greatest frequency of rare species), and pastures (least developed soil crusts, lowest shrub cover, highest soil nutrients). We established replicated restoration treatments to examine the effects of seed additions, plant additions, grass removal using herbicides, and nitrogen reduction using carbon (sugar and sawdust) additions on restoration outcomes.
Results/Conclusions In 2006, we initiated our first seed addition experiment, placing 900 seeds of each of 11 species into disturbed scrub. One-year post-sowing, overall germination was higher in open than shrub microsites (1.0 vs 0.4%) and varied among species (0-5.2%). We hypothesized that grass removal, particularly in improved pastures, would speed restoration. In the fall of 2007, we transplanted 1165 plants of eight species into the restoration. After six months, plants introduced into herbicided pasture plots had higher survival (84%) than plants inserted into exotic grasses (70%). Transplant survival was higher for larger transplants and also varied depending on exotic grass species and transplant species (woody plants outperformed palms). In two experiments, sugar addition created short-term decreases in inorganic soil nitrogen, but sugar and sawdust combined resulted in both short- and long-term decreases. Exotic grass removal, nitrogen reductions, manipulation of vegetation structure, and use of transplants appear to provide the fastest routes to achieving Florida scrub restoration goals.
