RICHARDS, J.H.1*, Q.J. STOBER2, R.D. JONES3, and S.L. RATHBUN4. 1Dept. of Biological Sciences, Florida International University, Miami, FL 33199; 2EPA Region 4 Science and Ecosystem Support Division, 980 College Station Road, Athens, GA 30605; 3Southeast Environmental Research Center, Florida International University, Miami, FL 33199; 4Dept. of Statistics, University of Georgia, Athens, GA 30602. - A quantitative analysis of wetland plant communities in south Florida Everglades.
South Florida’s Everglades, which are the focus of an $8 billion,
30-year restoration plan, have diverse subtropical wetland plant
communities. In May and October, 1999, we censused 240 sites in the
Everglades for plant species presence and relative abundance, then
used UPGMA to cluster these sites into groups based on this data.
Sites were chosen in a stratified-random sampling design, and 1 or 2
10-m transects were sampled at each site for a total of 418 transects.
Soil and water nutrients were also analyzed for each site. The species
present were determined for 5 1-m2 quadrats per transect. Each quadrat
was subdivided into 4 0.25-m2 units. We found 161 taxa, but 91% of
these occurred in fewer than 10% of the transects. Transects had a
mean of 5 species (range = 0 – 30). When the transects were aggregated
into 8 clusters, we had 4 small clusters with 1-3 transects each and 4
larger clusters. The larger clusters were a sawgrass (Cladium
jamaicense) cluster, a spikerush (Eleocharis cellulosa)
cluster, a water lily (Nymphaea odorata) – bladderwort
(Utricularia purpurea) cluster, and a cattail (Typha
domingensis) cluster. Some commonly recognized Everglades plant
associations, such as maidencane (Panicum hemitomon) and
beakrush (Rhynchospora tracyi) flats, did not form distinct
clusters in our analysis. The absence of large clusters defined by
these species could represent differences among studies in scale or
type of analysis, or it could reflect historical changes in the
Everglades ecosystem. Logistic regression of species occurrence
against soil phosphorus (P) or ash-free dry weight (AFDW) showed that
sawgrass occurs across a broad range of P levels and soil types, while
cattails increase in abundance with increasing soil P. Beakrush,
bladderwort and spikerush are found at relatively low soil P, and
water lilies are found in soils with intermediate P and high AFDW.
Key words: Cladium, Eleocharis, Everglades wetland plant communities, Nymphaea, Typha, Utricularia