Habitat structure and plant community composition in a northern Everglades wetland landscape

Abstract

The structure of a priori-defined aquatic habitats was compared within the Arthur R. Marshall Loxahatchee National Wildlife Refuge, which comprises the northern remnant of the Everglades ecosystem. Total plant biomass, canopy height, water depth, and the relative abundance (percent cover) of plant species in adjacent sloughs (including alligator holes), wet prairies, and sawgrass stands were compared over a 30-month period. These habitats formed a mosaic of aquatic habitats of differing structure and plant community composition. Slough and alligator hole habitats were in deeper water with little or no canopy, and habitat structure was provided almost entirely by submersed bladderwort (Utricularia) and floating water lily (Nymphaea). Sawgrass stands were present in shallower water and had a well-developed canopy that was generated almost entirely by Cladium. Wet prairies were intermediate in water depth and canopy stature, with emergent sedges (i.e., Eleocharis, Rhynchospora) providing most habitat structure. Differences among adjacent habitats accounted for most of the observed variation in habitat structure and plant relative abundance, whereas differences among widely-separated areas in the Refuge (i.e, landscape-level differences) accounted for little of the observed variation. In contrast, water depth varied considerably among sampling areas, likely reflecting hydrologic gradients that occur across the Refuge landscape. Similarly, although differences among sampling months were minimal for most habitat features examined, most of the variation observed in water depth was accounted for by sampling rnonth, as would be expected in a seasonally dynamic wetland such as the Everglades. Discriminant function analyses using plant relative abundance data, habitat structure data, or both sets of data combined correctly classified most sites with respect to a priori-defined habitat type, despite similarities in plant community composition in sloughs and wet prairies. Overall, it appears that sloughs, wet prairies, and sawgrass stands are distinct with respect to habitat structure and plant corm'nunity composition and that differences among these habitats are persistent across the Refuge landscape.

Using soil profiles of seeds and molecular markers as proxies for sawgrass and wet prairie slough vegetation in Shark Slough, Everglades National Park

“…Using the resulting, albeit preliminary, depth-to-age relationship, we found that peaks in C. jamaicense seed profile corresponded to historic minimum water levels (e.g., at 1989-1990, and 2000-2001), while low points in the seed profile corresponded to historic maxima in water levels (e.g., 1995). This negative correlation between C. jamaicense seed abundance and higher water levels is consistent with the autecology of C. jamaicense: that high water levels decrease C. jamaicense biomass production (Newman et al, 1996;Childers et al, 2006) and that C. jamaicense biomass is less abundant in the deeper (long hydroperiod) areas of peat marshes (Gunderson, 1994;Snyder et al, 1994;Jordan et al, 1997). We emphasize that the soil dates presented here are tentative, and our inferred accretion rates ($5 mm year )1 ) appear relatively high compared to most peat-accumulating marshes in the Everglades (2.8-4.0 mm year )1 , Craft & Richardson, 1993;1.4-6.7 mm year )1 , Craft & Richardson, 1998; 1.2-1.8 mm year )1 , Cohen et al, 1999) although they are not unprecedented for South Florida peatlands (5-9 mm year )1 , Donders et al, 2004).…”

Ecological effects of low-level phosphorus additions on two plant communities in a neotropical freshwater wetland ecosystem

“…Approximately 65% of the Everglades is SAW, dominated by C. jamaicense Crantz (Davis 1943;Loveless 1959), with shorter hydroperiods and more frequent fires than other Everglades wetlands (Wood and Tanner 1990;Herndon et al 1991;Gunderson 1994;Jordan et al 1997). WP, the second most common wetland type, is dominated by two spikerush species, Eleocharis cellulosa and E. elongata (henceforth collectively referred to as Eleocharis spp.)…”

Discharge Competence and Pattern Formation in Peatlands: A Meta-Ecosystem Model of the Everglades Ridge-Slough Landscape

“…The ridge-slough landscape of the central Everglades is a lotic peatland in which distinct vegetation assemblages are organized by microtopographic variation and associated differences in hydroperiod [37], [38]. Higher elevation ridges experience annual hydroperiods of 300–340 days [39]–[41], and are occupied by largely monotypic stands of sawgrass ( Cladium jamaicense ); sloughs contain a mixture of floating and submerged plants and calcareous periphyton mats that thrive under continuous inundation.…”

“…Prior to modern hydrologic changes, elevation differences between ridges and sloughs are estimated to have ranged from 30 to 60 cm [41], [44]. Intermediate depths between ridges and sloughs were relatively rare historically [41] and in conserved landscapes [40], but support a more diverse assemblage of emergent species, in a community commonly referred to as wet prairie [37]–[39]. The abundance of the wet prairie community varies considerably across the landscape [39], [40] and increases during dry periods when slough hydroperiods and inundation depths decline [38], [45].…”