PARENT SESSION
Organized Oral Session 6: Development of landscape heterogeneity at multiple scales in wetlands
Organizer(s): B Warner and A van der Valk
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 516 A, Level 5, Palais des congrès de Montréal

Tree islands in the Everglades as a function of hydrological heterogeneity.

Sklkar, Fred^*,1, van der Valk, Arnold², Coronado, Carlos¹, Korvela, Michael¹, ¹ Everglades Division, West Palm Beach, FL, USA² Ecology, Evolution & Organismal Biology, Ames, Iowa

ABSTRACT- Tree islands are 1-10 ha organic outcroppings that harbor the highest diversity of plants and animals in the Everglades. The maximum elevations of these habitats are often elevated only slightly from the surrounding marsh making them quite vulnerable to changes in hydrology. Permanent vegetation plots were established on nine tree islands to examine how hydrology has shaped the current distribution and abundance of woody tree species in Water Conservation Area (WCA) 3. Study sites represented a hydrologic gradient ranging from low water levels with short hydroperiods in northern WCA-3 to high water levels with longer hydroperiods in southern WCA-3. In general, tree species basal area (BA) tended to be highest on tree islands characterized by having elevated heads, high soil Total Phosphorus, and moderate hydrologic regimes. Canonical Correspondence Analysis (CCA) indicated that both depth and hydroperiod explained 26% of the variability of the presence/absence of woody species, and that soil Total Phosphorus explained only 10% of the presence/absence variability. A complexity index (CI), which takes into consideration basal area, stem density, canopy height, and diversity, was used as an indicator of tree island health. A low CI value for islands in the northern portion of WCA 3 indicated low BA and low species diversity associated with extended periods of low water and poor-nutrient soil. In contrast, islands with moderate hydrologic regimes and rich-nutrient soil had the highest CI values due to a high degree of ecological maturity (i.e., high basal area and stem densities). These results indicate the importance of hydrology and nutrients in driving the distribution and abundance of woody species in tree islands located in WCA-3.

Key words: restoration, wetlands, tropical, management