The Development of a Geographic Information System （GIS） to Document Research in an Everglades Physical Model

The Loxahatchee Impoundment Landscape Assessment （LILA） facility is a unique physical model of the Everglades ecosystem. LILA has a closed-loop water delivery system and consists of four 0.08 square kilometer （-8 ha） macrocosms, created to be replicates of one another and of the Everglades landscape. Built in 2003, LILA＇s purpose is to provide scientists with an opportunity to design and implement research concerning Everglades restoration techniques in an accessible, controlled and replicated Everglades environment. Key Everglades habitats were sculpted within LILA： tree islands, ridges, sloughs and alligator holes. Water levels and flows in each macrocosm are controlled independently, so that researchers can study the effects of hydrology on Everglades landscape and ecology. Studies have focused upon measuring survival and growth of native trees planted on the tree islands; measuring surface water and ground water movement and chemistry; studying wading bird feeding and the movement of prey species （crayfish）; and measuring erosion and accretion on tree islands and ridges. We developed a Geographic Information System （GIS） data set to identify, characterize, and spatially reference the features of LILA and document research activities. This development included mapping the boundaries of the landscape features, creating a theoretical Digital Elevation Model （DEM） and describing the research projects being carried out. The creation of this GIS data set enhances the ability to schedule and coordinate research, assist scientists in the visualization and spatial representation of their research, and provide a resource for the storage, analysis and synthesis of valuable scientific information.

Impacts of fire and phosphorus on sawgrass and cattails in an altered landscape of the Florida Everglades

Introduction:Although fire as a critical ecological process shapes the Florida Everglades landscape,researchers lack landscape-based approach for fire management.The interactive effect of fire,nutrients,water depth,and invasive cattails(Typha spp.)on vegetation communities is of special concern for ecosystem restoration.In particular,questions concerning the effect of fire on nutrient release and,by extension,the potential thereof to stimulate sawgrass(Cladium jamaicense Crantz)re-growth and cattail expansion under varying hydrological conditions are of immediate relevance to ecologists and land managers who work to restore the Everglades.Methods:In late April of 1999,a 42,875 ha surface fire,including a 100 ha peat fire,burned the northern section of Water Conservation Area 3A(WCA-3A)in the Everglades.In this study,total phosphorus(TP)in soil,surface water,pore-water,and vegetation was sampled at non-burned,surface-burned and peat-burned areas within one and five months after the burn.Four years after the initial fire,field data were collected in a large scale survey to analyze how the 1999 fire affected cattail distribution in the altered landscape of high soil TP and cattail habitats.Existing GIS maps were utilized to select field sampling locations and to provide additional information for the analysis.Results:The analyses showed that five months after the fire,sawgrass biomass re-growth was about 5 times higher in burned areas(611±47 g/m^(2))than in non-burned areas(102±18 g/m^(2)).Sawgrass re-growth in water depths less than 30 cm was 4.9±0.4 g/m^(2)/day while sawgrass re-growth in water depths deeper than 60 cm decreased to 0.5±0.3 g/m^(2)/day.Cattail biomass re-growth in peat-burned areas was as high as 1,079±38 g/m^(2).The data also showed that post-fire cattail expansion could be related to cattail stands existing before the fire.Furthermore,post-fire cattail appeared more significant expansion in the areas with soil TP above 900 mg/kg than in that with soil TP below 900 mg/kg.Conclusions:The data showed that fire within altered landscapes(e.g.high soil TP and/or cattail)of the Everglades could stimulate the re-growth and expansion of cattails,and post-fire re-growth of sawgrass could be severely impeded by deep water after a surface-burn.This research indicates that fire continues to be an effective ecological process for maintaining the Everglades;therefore,ecologists and land managers may have to reevaluate the future management of natural fire with regard to its dynamic relationship with high soil TP and cattail expansion in the altered Everglades landscape.

Counteracting the Effects of Sea Level Rise in Southeast Florida

Over the past 100 years, worldwide surface temperatures have increased at an unprecedented rate, contributing to warming of the oceans, melting ice fields and glaciers, and other adverse climatic effects. Southeast Florida＇s vulnerability derives from its geographic location, low elevation, porous geology, unusual ground and surface water hydrology, subtropical weather patterns, and proximity to the Atlantic Ocean. The region is especially susceptible to sea level rise. After several millennia of stable sea levels prior to the 20th century, sea levels have been rising at accelerating rates due to thermal expansion of the oceans and from land-based ice melt The Everglades ecosystem and the water supplies for southeast Florida are particularly vulnerable as neither can be protected without significant expenditures of public dollars, and even these efforts may not prove to be successful. New approaches may be required to improve the resilience and prolong the sustainability of the region＇s water resources and ecosystem. The efforts to adapt to sea level changes in both the urban area and ecosystem as outlined herein are date and incident based-climate changes may occur earlier or later so instead of spending limited public dollars early, expenditures can be adjusted given future information.

Evaluation of nutrient stoichiometric relationships among ecosystem compartments of a subtropical treatment wetland. Do we have “Redfield wetlands”?

Background:Evaluation of carbon(C),nitrogen(N),and phosphorus(P)ratios in aquatic and terrestrial ecosystems can advance our understanding of biological processes,nutrient cycling,and the fate of organic matter(OM)in these ecosystems.Eutrophication of aquatic ecosystems can change the accumulation and decomposition of OM which can alter biogeochemical cycling and alter the base of the aquatic food web.This study investigated nutrient stoichiometry within and among wetland ecosystem compartments(i.e.,water column,flocculent,soil,and aboveground vegetation biomass)of two subtropical treatment wetlands with distinct vegetation communities.Two flow-ways(FWs)within the network of Everglades Stormwater Treatment Areas in south Florida(USA)were selected for this study.We evaluated nutrient stoichiometry of these to understand biogeochemical cycling and controls of nutrient removal in a treatment wetland within an ecological stoichiometry context.Results:This study demonstrates that C,N,and P stoichiometry can be highly variable among ecosystem compartments and between FWs.Power law slopes of C,N,and P within surface water floc,soil,and vegetation were significantly different between and along FWs.Conclusions:Assessment of wetland nutrient stoichiometry between and within ecosystem compartments suggests unconstrained stoichiometry related to P that conforms with the notion of P limitation in the ecosystem.Differences in N:P ratios between floc and soil suggest different pathways of organic nutrient accumulation and retention between FWs.Surface nutrient stoichiometry was highly variable and decoupled(or close to decoupled as indicated by<25%explained variation between parameters),in particular with respect to P.We hypothesize that decoupling may be the imprint of variability in inflow nutrient stoichiometry.However,despite active biogeochemical cycles that could act to restore nutrient stoichiometry along the FW,there was little evidence that such balancing occurred,as the degree of stochiometric decoupling in the water column did change with distance downstream.This information is only the beginning of a larger journey to understand stoichiometric processes within wetland ecosystems and how they relate to ecosystem function.

Environmental stress and eutrophication in freshwater wetlands: evidence from carbon and nitrogen stable isotopes in cattail (Typha domingensis Pers.)

Background:Florida’s Everglades is a vast freshwater peatland that has been impacted by the alterations of hydrological pattern and water quality which led to changes in plant species composition and biodiversity.In this study,carbon and nitrogen stable isotopes(δ13C andδ15N)in cattail(Typha domingensis)are evaluated as indicators of environmental changes in the Everglades wetlands along nutrient and hydrological gradients represented by reference sites with total phosphorus(TP)<10μg L−1,transition sites with TP≥10μg L−1<20μg L−1 and impacted sites with TP≥20μg L−1 which differed in hydrology or habitats(marsh and canal).Results:Cattailδ13C values decreased significantly from reference(–24.1‰),transition(–26.8‰)to the impacted sites(–28.2‰).In contrast,δ15N values increased significantly from reference(–5.2‰),transition(2.4‰)to the impacted site(5.9‰).In response to a poor hydrological condition,cattail in marsh area displayed 13C enrichment(–26.0‰)and 15N depletion(0.2‰).By contrast,cattail grown in the canal sites with favorable hydropattern displayed 13C depletion(–27.6‰)and 15N enrichment(5.9‰)from the canal sites with more favorable hydrological condition.Conclusions:The different patterns for the changes inδ13C andδ15N in cattail suggested that increased nutrients led to increased stomatal conductance and 13C fractionation during carbon uptake and decreased 15N fractionation with increasing nitrogen demand while poor hydrological condition coupled with low nutrients led to reduced plant growth indicated by higherδ13C and lowerδ15N values.Findings from this study suggested thatδ13C in emerged macrophytes such as cattail can be used as an indicator for environmental stress whileδ15N is a robust indicator for wetland eutrophication.