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Aboveground vs. belowground competition for seedlings in post fire rosemary scrub, Florida.
Carrington, Mary *,1, 1 Governors State University, University Park, IL
ABSTRACT- Belowground competition is expected to be more intense than aboveground competition during post fire seedling recruitment in rosemary scrub, an open, shrub-dominated ecosystem occurring in peninsular Florida on nutrient-poor, sandy soils. To test this prediction, during September 2002 I established a field study at Archbold Biological Station to compare the intensity of aboveground vs. belowground competition during recruitment of sand pine (Pinus clausa) seedlings. The study is a 2 x 2 factorial design; treatment factors are aboveground competition (+ or -) and belowground competition (+ or -). I established treatment plots in 11 rosemary scrub patches (balds) within a 268-ha area that burned in February 2001. In each rosemary patch I established eight treatment plots (two replicates of each of the four treatments) in a stratified random manner on both sides of a 44-m line transect. To eliminate aboveground competition, I clipped all vegetation to ground level in a 2-m diameter circular area surrounding the treatment plot. To eliminate belowground competition, I inserted a PVC pipe 13 cm in height and 10 cm in diameter into the soil at the treatment plot so that the top of the pipe was level with the soil surface. For all other plots (with belowground competition), as a procedural control I inserted a PVC pipe and immediately removed it. I then placed five sand pine seeds within the 10-cm diameter area in the center of each treatment plot, and covered the seeds with a 7 x 7 x 3 cm exclosure made of 1/8-in hardware cloth to deter seed predators. Seed germination and seedling survival are checked monthly, and plots were re-clipped in February 2003. Seedling germination began in October 2002, with the majority of germination occurring in November 2002. Twenty-five seedlings germinated in 23 different plots by March 2003. Number of emerged seedlings did not differ by treatment (2 = 2.06, d.f. = 3, P > 0.5). Although more seedlings died in plots without aboveground competition (6) than in plots with aboveground competition (1), the difference is not statistically significant (2 = 1.33, d.f. = 1, P>0.1). Monthly monitoring of seedling survival and growth will continue for an additional year.
Key words: sand pine scrub, Pinus clausa, competition, rosemary scrub