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Ecological Indicators 24 (2013) 294–304

Contents lists available at SciVerse ScienceDirect

Ecological Indicators

journa l homepage: www.e lsev ier .com/ locate /eco l ind

sing hydrologic suitability for native Everglades slough vegetation to assessverglades restoration scenarios

licia M. Lo Galboa,∗, Michael S. Zimmermana, David Hallacb, Gregg Reynoldsa,ennifer H. Richardsc, Janice H. Lyncha

National Park Service, South Florida Natural Resources Center, Everglades National Park, 950 North Krome Avenue, Homestead, FL 33030, USANational Park Service, Yellowstone Center for Resources, Yellowstone National Park, P.O. Box 168, WY 82190, USADepartment of Biological Sciences, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA

r t i c l e i n f o

rticle history:eceived 13 December 2011eceived in revised form 20 April 2012ccepted 8 June 2012

eywords:vergladesydrologyodelymphaea odorataestorationloughater lily

a b s t r a c t

Simulating ecological indicator responses to alternate restoration strategies provides decision supporttools for resource managers and restoration planners. Our case study provides a methodology for how toutilize hydrologic suitability for native vegetation to evaluate effects of modeled restoration scenarios.We propose that hydrologic suitability of white water lily, Nymphaea odorata, an indicator species ofthe native Florida Everglades slough vegetation community, be used to evaluate modeled restorationscenarios in the Everglades ridge and slough landscape. Based on experimentally derived mesocosmand field studies and historical evidence, we developed a predictive performance measure to assesshydrologic suitability for N. odorata. We applied the performance measure to predict the hydrologicsuitability for slough vegetation in the Everglades ridge and slough landscape using model-simulatedhydrology of existing conditions, future conditions with restoration, and the predrainage Everglades. Ourresults indicate that Everglades restoration will provide the greatest benefits to native slough vegetationin Arthur R. Marshall Loxahatchee National Wildlife National Refuge (LNWR), Water Conservation Area

(WCA) 3B, and Everglades National Park, and may degrade slough conditions within portions of WCA 2 andWCA 3A. Our analysis indicates that additional restoration efforts are needed to fully restore native sloughvegetation communities throughout the Everglades ridge and slough landscape. Performance measureresults for the predrainage scenario in the WCAs conflict with paleoecological data; these results indicatea need to improve the modeled predrainage topography as well as flow and evapotranspiration rates ofthe Natural System Model version 4.6.2 (hereinafter NSM).

. Introduction

Prior to the substantial drainage and compartmentalization ofhe Florida Everglades that began in the late 1800s, the ridge andlough habitat was the most expansive landscape in this wetlandcosystem, comprising more than half of the historical EvergladesMcVoy et al., 2011). This landscape comprised the majority of

odern-day Arthur R. Marshall Loxahatchee National Wildlifeational Refuge (LNWR), Water Conservation Area (WCA) 2, WCA, and Shark River Slough in Everglades National Park (Lodge, 2010;

Abbreviations: CERP, Comprehensive Everglades Restoration Plan; LNWR, Arthur. Marshall Loxahatchee National Wildlife Refuge; NSM, Natural System Model;FWMM, South Florida Water Management Model; WCA, Water Conservation Area.∗ Corresponding author. Tel.: +1 305 224 4243; fax: +1 305 224 4147.

E-mail addresses: Alicia Logalbo@nps.gov (A.M. Lo Galbo),ike Zimmerman@nps.gov (M.S. Zimmerman), David Hallac@nps.gov (D. Hallac),regg Reynolds@nps.gov (G. Reynolds), Richards@fiu.edu (J.H. Richards),

anice Lynch@nps.gov (J.H. Lynch).

470-160X/$ – see front matter. Published by Elsevier Ltd.ttp://dx.doi.org/10.1016/j.ecolind.2012.06.011

Published by Elsevier Ltd.

McVoy et al., 2011) (Fig. 1). During the predrainage era, deeperwater sloughs populated with white water lily, Nymphaea odor-ata, interspersed with tree islands and dense stands of sawgrass,Cladium jamaicense, forming the patterned ridge and slough land-scape that was oriented parallel to the direction of flow (Lodge,2010; McVoy et al., 2011). This topography was termed “ridgeand slough”, because the C. jamaicense ridges were approximately30–90 cm (1–3 ft) higher than the adjacent sloughs in the early1900s (Baldwin and Hawker, 1915; Lodge, 2010; Wright, 1912).Sawgrass ridges in the predrainage Everglades were an estimated30–762 m (100–2500 ft) wide and 2–8 km (1–5 miles) long; sloughswere approximately 91–396 m (300–1300 ft) wide and more than10 km (6 miles) long (McVoy et al., 2011).

Substantial alterations in the natural hydrology and topogra-phy of the Everglades ridge and slough landscape began in the

late 1800s as a result of the urbanization, compartmentalization,and wide-scale drainage of the Everglades (Light and Dineen,1994; McVoy et al., 2011). During the first half of the twentiethcentury, approximately one-half of the 1.2 million ha Everglades

A.M. Lo Galbo et al. / Ecological Indicators 24 (2013) 294–304 295

Fig. 1. Estimated predrainage Everglades landscape (left) and modern-day Everglades landscape (right), figure reprinted with permission of the University Press of Florida,M Loxah

woiatcacPw

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cVoy et al. (2011) (EAA = Everglades Agricultural Area, LNWR = Arthur R. Marshall

as developed or converted to agriculture (Davis et al., 1994). Muchf the modern environmental degradation within the Evergladess attributed to the Central and Southern Florida Project that wasuthorized by the US Congress in 1948. This project supplies watero municipal, industrial, and agricultural areas, and provides floodontrol throughout South Florida by use of water impoundments,n intricate canal system, and water management structures. Theonstruction and operation of the Central and Southern Floridaroject further fragmented the landscape and altered hydrologyithin the remaining Everglades ecosystem.

The Comprehensive Everglades Restoration Plan (CERP),pproved by the US Water Resources Development Act of 2000, ishe guiding framework for modifications to the Central and South-rn Florida Project. The purpose of the CERP is to restore, conserve,nd protect the South Florida ecosystem while providing for othereeds such as water supply and flood protection. The CERP is the

argest ecosystem restoration project in the world and consists ofsuite of 68 projects intended to improve ecological connectiv-

ty, water quality, hydroperiods, and hydropatterns throughout theverglades landscape. The initial series of 10 restoration projectsodeled and planned as part of the CERP are referred to as the

and 1 projects.The modern-day “ridge and slough” landscape is symptomatic of

he anthropogenic degradation of the predrainage Everglades thats characterized by flattened topography, oxidized soils, and alteredegetation community composition (McVoy et al., 2011; Richardst al., 2009; Sklar et al., 2000). Estimated elevation differences

mean ground) between ridges and sloughs in WCA 3 and Sharkiver Slough are now only 10 cm (0.3 ft) (Richards et al., 2009). The

oss and degradation of the ridge and slough landscape had cascad-ng impacts on the aquatic productivity of the Everglades ecosystem

atchee National Wildlife Refuge, WCA = Water Conservation Area).

that ultimately impacted higher-level trophic consumers (Daviset al., 1994; McVoy et al., 2011; White, 1994).

Palynological sediment core profiles provide data for recent andfossil pollen and spore abundances; these have been used to esti-mate changes in Everglades vegetation assemblages from historicalto modern times. While the spatial sampling of deep-core paly-nological data is limited, existing data indicate the presence ofN. odorata slough communities in LNWR, WCA 2A, and WCA 3Aduring the predrainage era (Bernhardt et al., 2004; Willard et al.,2001a,b). The palynological profile indicates that significantly drierconditions occurred during the twentieth century as comparedto the predrainage era in these slough vegetation communities(Bernhardt et al., 2004; Willard et al., 2001a,b). A communityshift from sloughs to C. jamaicense marshes and weedy annualsoccurred after 1930 at sites in WCA 2A and WCA 3A (Willardet al., 2001a). Between 1950 and 1960, vegetation changed from N.odorata sloughs to C. jamaicense marshes in LNWR (Willard et al.,2001a). The twentieth century drying events coincided with theconstruction of the Herbert Hoover Dike around Lake Okeechobee,with completion of drainage canals connecting Lake Okeechobeeto the Atlantic Ocean and the Gulf of Mexico, and with imple-mentation of the Central and Southern Florida Project (McVoyet al., 2011; Willard et al., 2001a). After 1930, the pollen profileat a Taylor Slough site in Everglades National Park indicated achange in vegetation community composition to asters and sedges,potentially signifying increased disturbance, fluctuating water lev-els, and/or drier conditions (Willard et al., 2001a). Seed profile

data also have revealed a decline in N. odorata slough communi-ties in Everglades ridge and slough habitats such as WCA 3B andShark River Slough at the start of the twentieth century as com-pared to the predrainage era (Saunders et al., 2008). This decline

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96 A.M. Lo Galbo et al. / Ecologi

ignified a vegetation community response to the drainage andompartmentalization of the Everglades at the start of the twen-ieth century.

N. odorata is no longer abundant throughout the estimatedidge and slough predrainage geographic landscape in modern-day

CA 2, WCA 3, and Everglades National Park (McVoy et al., 2011;ichards et al., 2009; Sklar et al., 2000; Stober et al., 2001). The cen-ral portion of many sloughs sampled in WCA 3 and Shark Riverlough that historically were a N. odorata-dominated community,re now dominated by coastal spikerush, Eleocharis cellulosa, signi-ying a change to shallower water depths and reduced hydroperiodsRichards et al., 2009). While distinct physicochemical and plantssemblage differences still distinguish Everglades ridges fromloughs today, slough degradation is characterized by changes inlant species composition and physical degradation of the ridge andlough topography (Nungesser, 2011; Richards et al., 2009; Wattst al., 2010; Wu et al., 2006).

Everglades vegetation communities have been characterizedy interacting multi-dimensional environmental parameters that

nclude hydroperiod, hydropatterns, water quality, and soil physic-chemistry (Givnish et al., 2008; King et al., 2004; Powers, 2005;ichards et al., 2009; Stober et al., 2001). Water depth andydroperiod are two hydrological variables that have been usedo distinguish Everglades vegetation communities (Givnish et al.,008; King et al., 2004; Powers, 2005; Richards et al., 2009;tober et al., 2001). Canonical correspondence analysis revealedhat annual mean water depth, soil depth, soil total phosphorus,orewater nitrate and nitrite, soil total nitrogen, and surface waterotal phosphorus significantly affected vegetation patterning byite and species composition at ridge and slough sites in WCA 3nd Shark River Slough (Richards et al., 2009). Annual mean waterepth and soil depth had the most explanatory power in deter-ining plant community composition in ridge and slough habitats

Richards et al., 2009). The US Environmental Protection Agencyegional Environmental Monitoring and Assessment Program sur-eyed plant communities across the Everglades ecosystem in 1999.luster analysis of vegetation communities based on frequencyf occurrence, throughout LNWR, WCA 2, and WCA 3, and Ever-lades National Park resulted in a N. odorata-dominated clusterhat also contained the two bladderworts, Utricularia purpurea andtricularia foliosa, the slim spikerush, Eleocharis elongata, and maid-ncane, Panicum hemitomon (Stober et al., 2001).

The paleoecological data in association with field vegetationtudies and the historical record provide unified evidence that N.dorata is an indicator species of the native Everglades slough veg-tation community (Bernhardt et al., 2004; Jordan et al., 1997;owers, 2005; McVoy et al., 2011; Richards et al., 2009; Saunderst al., 2008; Stober et al., 2001; Willard et al., 2001a,b). N. odoratas the signifying pollen and seed signature of the slough vegeta-ion community in paleoecological data collected throughout theverglades (Bernhardt et al., 2004; Saunders et al., 2008; Willardt al., 2001a,b). Field vegetation studies provide evidence of thendicator value (in terms of abundance and frequency of occur-ence) of N. odorata in the Everglades slough vegetation communitynd the effect of hydrology on vegetation community compositionJordan et al., 1997; Powers, 2005; Richards et al., 2009; Stober et al.,001). McVoy et al. (2011) provides historical evidence from landurveyors, explorers, early settlers, and scientists that N. odorataas “ubiquitous in predrainage sloughs”. To use N. odorata as an

ndicator, however, we need to quantify this species’ response toydrologic change.

Predictive tools to assess the effects of landscape-scale restora-

ion efforts are needed by resource managers and planners tonticipate future effects from restoration efforts and identify defi-iencies. Ecological indicators have been used to assess currentonditions in the Everglades ecosystem (Doren et al., 2009), but

icators 24 (2013) 294–304

have not been used to predict the suitability for reestablish-ment of predrainage Everglades vegetation. The purpose of ourstudy was to develop a predictive performance measure tool thatcan be used to simulate the effects of past, current, and futurehydrological conditions on the native Everglades slough plant com-munity. A key objective was to predict the anticipated effects of theCERP hydrology on Everglades slough vegetation. The importanceof hydrological factors driving vegetation community composi-tion is well documented from field studies conducted outside ofthe Florida Everglades; however, studies that estimate vegetationcommunity response to future hydrologic conditions are limited(Battaglia and Collins, 2006; Boumans et al., 2002; Poiani andJohnson, 1993; Venterink and Wassen, 1997). Our study contributesto this body of literature and provides a case study for how to applyhydrologic suitability for native vegetation to evaluate effects ofmodeled restoration scenarios.

2. Methods

Hydrologic suitability metrics for the slough vegetation indica-tor species N. odorata were established based on a literature review.From the compiled literature, we identified metrics for N. odoratathat could be evaluated with hydrologic simulation output pro-vided by the South Florida Water Management Model (SFWMM)and the Natural System Model (NSM).

The SFWMM is used to simulate current hydrological conditionsand future conditions, both with and without restoration scenar-ios. The NSM is used to simulate the hydrologic response of thepredrainage Everglades to rainfall and climatic inputs. The SFWMMand the NSM hydrologic simulation models have a 2-mile by 2-mile grid cell resolution and the domain of the models is limited tolands within the South Florida Water Management District (Fig. 2).The simulation period for both the SFWMM and the NSM is basedon 1965–2000 climatic data. The NSM, however, uses estimatedpredrainage topography, evapotranspiration rates, and hydrologicparameters such as resistance to flow.

We developed a slough vegetation performance measure thatconsists of the following four metrics: annual maximum continu-ous days (hydroperiod) that the water elevation was above groundsurface; annual maximum continuous dry down days at or below20 cm (0.7 ft); and annual mean wet season (June–October) and dryseason (November–May) water depths.

All field and mesocosm literature we reviewed indicates thatnear-continuous hydroperiod (∼>90% time inundated) providessuitable conditions for N. odorata (Table 1; Cohen et al., 1984;Conti and Gunther, 1984; David, 1996; De Steven and Toner,2004; Duever, 1982; Givnish et al., 2008; Goodrick, 1984; Jordanet al., 1997; Richards et al., 2009; Stober et al., 2001; Zaffke,1983). Flowering and leaf production rates of N. odorata were sup-pressed in a mesocosm dry down experiment when the shoot tipsbecame emergent (Richards et al., 2009). Such a severe physiolog-ical response did not occur in N. odorata plants that dried down tothe 20 cm (0.7 ft) water depth in the mesocosm experiments. Theresults of the experiments indicate that suitable conditions for N.odorata will be to minimize dry downs below 20 cm (0.7 ft).

While water depth maxima and minima would be viable metricsfor assessing slough vegetation hydrologic suitability, the SFWMMbetter simulates seasonal water depth averages (Bras et al., 2005).Therefore, we used seasonal water depth metrics in the slough veg-etation performance measure. Preferential flowering rates and leafbiomass for N. odorata were reported at mesocosm water depth

treatments where plant shoot apices were at 45 cm (1.5 ft) and75 cm (2.5 ft) as compared to the shallower 15 cm (0.49 ft) treat-ment (Table 1; Richards et al., 2011). Compilation of field recordsprovided an estimated annual mean slough vegetation water depth

A.M. Lo Galbo et al. / Ecological Indicators 24 (2013) 294–304 297

Fig. 2. Indicator regions in the South Florida Water Management Model grid of the Everglades, figure courtesy of Restoration Coordination and Verification (2007)(Lox = Loxahatchee, LNWR = Arthur R. Marshall Loxahatchee National Wildlife Refuge, NE = Northeast, NW = Northwest, SFWMM = South Florida Water Management Model,SW = Southwest, WCA = Water Conservation Area, WMA = Wildlife Management Area).

298 A.M. Lo Galbo et al. / Ecological Indicators 24 (2013) 294–304

Table 1Empirical evidence defining hydroperiods and hydropatterns for native Everglades slough vegetation (values presented ± standard error unless otherwise indicated.SD = standard deviation).

Species or community Study type Location Hydroperiod and dry out ordry down tolerance

Water depth Reference

N. odorata-dominated openmarsh

Field Okefenokee Swamp, GA ∼365 days Common range 30–100 cm(1–3 ft)

Cohen et al. (1984)

N. odorata Field Okefenokee Swamp, GA ∼365 days Range 25–100 cm (0.8–3 ft) Conti and Gunther (1984)N. odorata Field WCA 3A, FL 219–365 days (mean

discontinuous range)Mean 54 ± 21 (SD) cm(1.8 ± 0.69 ft)

David (1996)

N. odorata-dominated openwater community

Field Upper Coastal Plain, SC Index 3.8 ± 0.1(4 = continuous, 3 = dry out(August–October))

Mean (ponded conditions)150 ± 20 cm (4.9 ± 0.7 ft)

De Steven and Toner (2004)

N. odorata mixed graminoidcommunity

Field Okefenokee Swamp, GA 346 days (April–March): 1dry out (for a month ormore) in 16 years

Range ∼ −2.00–38.0 cm(−0.0656–1.25 ft)

Duever (1982)

N. odorata and Utriculariaspp.-dominated slough

Field Central WCA 3A, FL 364 ± 0.2 days Mean 55.6 ± 1.2 cm(1.82 ± 0.039 ft); minimum16.1 ± 1.3 cm(0.528 ft ± 0.043 ft); maximum92.6 ± 1.4 cm (3.04 ± 0.046 ft)

Givnish et al. (2008)

N. odorata and Utriculariaspp.-dominated slough

Field Southern WCA 3A, FL 365 ± 0.1 days Mean 78.4 ± 1.9 cm(2.57 ± 0.062 ft); minimum36.0 ± 1.6 cm (1.18 ± 0.052 ft);maximum 114.3 ± 2.0 cm(3.750 ± 0.066 ft)

Givnish et al. (2008)

N. odorata and Utriculariaspp.-dominated slough

Field Southern WCA 3B, FL 359 ± 1.3 days Mean 51.6 ± 1.3 cm(1.69 ± 0.043 ft); minimum15.8 ± 1.3 cm (0.518 ± 0.043 ft);maximum 81.3 ± 1.6 cm(2.67 ± 0.052 ft)

Givnish et al. (2008)

N. odorata and E.elongata-dominatedcommunity

Field WCA 2A, FL 360 days (meandiscontinuous); 1 (48 days)dry out in 10 years; 60%time > 76 cm (2.5 ft) inOctober

Maximum wet season 130 cm(4.2 ft)

Goodrick (1984)

N. odorata-dominatedcommunity

Field WCA 3A, FL 348 days (meandiscontinuous); 4 dry outs(7–63 days) in 10 years;40% time > 76 cm (2.5 ft) inOctober

Maximum wet season 110 cm(3.5 ft)

Goodrick (1984)

N. odorata dominated-sloughsand alligator holes

Field LNWR, FL 365 days Mean ∼38 + 1 cm (1.3 + 0.03 ft) Jordan et al. (1997)

N. odorata, C. jamaicense, E.elongata, U. purpurea andfibrous bladderwort,Utricularia fibrosa (synonym ofUtricularia gibba) community

Field WCA 2A, FL Frequency ≤ 10 cm(0.3 ft) = 6.0 + 0.8%

Mean 46.4 ± 10.4 (SD) cm(1.52 ± 0.341 ft)

King et al. (2004)

Slough Historical FL Everglades 365 days Maximum wet season 90 cm(3 ft); minimum dry season30 cm (1 ft)

McVoy et al. (2011)

E. elongata slough with annualspikerush, Eleocharisgeniculata, N. odorata,Utricularia spp. andspider-lilies, Hymenocallis spp.

Field WCA 3A, FL Mean range 24–88 cm(0.80–2.9 ft)

Powers (2005)

Banana lily, Nymphoidesaquatica, N. odorata, andUtricularia spp. deep slough

Field WCA 3A, FL Mean range 30.–110 cm(1.0–3.5 ft);maximum ≥ 88.7 cm (2.91 ft)

Powers (2005)

Utricularia spp. shallow slough,may contain N. odorata

Field WCA 3A, FL Mean range 43–79 cm(1.4–2.6 ft)

Powers (2005)

E. cellulosa, U. purpurea, N.odorata, and N. aquaticacommunity

Field WCA 3A, WCA 3B,Everglades NationalPark, FL

355.3 ± 2.1 days (mean);2.0 ± 0.3 dry outs in 6 years

Mean 45.3 ± 2.4 cm(1.49 ± 0.079 ft); range25–71 cm (0.82–2.3 ft); N.odorata and U. purpureamaximum frequencyoccurrence 38–67 cm(1.2–2.2 ft)

Richards et al. (2009)

N. odorata Mesocosm Miami, FL Dry out(0.0 cm/ft) = exposed shoottips = suppressed leaf andflower production andminiaturized leaves;rewetted 0.0–20 cm(0.7 ft) ≥ flower productionand >leaf size

Leaf biomass 75 and 45 > 15 cm(2.5 and 1.5 > 0.49 ft); leaf size75 > 45 > 15 cm

Richards et al. (2009)

N. odorata Mesocosm Miami, FL Flower and seed production75 > 45 > 15 cm(2.5 > 1.5 > 0.49 ft)

Saunders et al. (2008)

A.M. Lo Galbo et al. / Ecological Indicators 24 (2013) 294–304 299

Table 1 (Continued)

Species or community Study type Location Hydroperiod and dry out ordry down tolerance

Water depth Reference

N. odorata and Utricularia spp.community

Field LNWR, WCA 2, WCA 3,Everglades NationalPark, FL

Hydroperiod class (annualmean) 330–365 days

Annual mean depth class30–61 cm (1.0–2.0 ft); meanwet season 94 cm (3.1 ft)

Stober et al. (2001)

N. odorata and spatter-dock,Nuphar lutea ssp.advena-dominatedcommunity

Field Lake Tohopekaliga, FL Range 20–180 cm (0.7–6 ft);biomass and densityhighest > 110 cm (3.6 ft)

Welch (2004)

N. odorata mixed graminoidcommunity

Field WCA 3, EvergladesNational Park, FL

Mean ∼ 24–58 cm(∼0.79–1.9 ft)

Wood and Tanner (1990)

N. odorata, Utricularia spp., E.elongata, lemon bacopa,Bacopa caroliniana aquaticslough

Field WCA 3A, FL Slough 339 days (mean);N. odorata 219–343 days(range); Utriculariaspp.190–343 days (range);

gata 2); B. ca43 day

Zaffke (1983)

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wr

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f 54 cm (1.8 ft)1 (Table 1; David, 1996; Givnish et al., 2008; Jordant al., 1997; King et al., 2004; Powers, 2005; Richards et al., 2009;tober et al., 2001; Wood and Tanner, 1990). In addition, com-ilation of historical evidence indicated an estimated maximumater depth (average annual) in predrainage sloughs of 90 cm (3 ft)

McVoy et al., 2011). Using both NSM and observed water depths,n annual maximum water depth of approximately 91 cm (3.0 ft)esulted in an average slough wet season water depth of approxi-ately 76 cm (2.5 ft). Based on our interpretation of the compiled

nformation, we estimated a wet season (annual mean) water depthf 61–91 cm (2.0–3.0 ft) as most suitable for N. odorata.

We based the dry season (annual mean) water depth suitabil-ty on the mesocosm and historical evidence because field data

ay indicate tolerance of sub-optimal conditions versus more suit-ble conditions. The predrainage minimum water depth for sloughsas approximately 30 cm (1 ft) (McVoy et al., 2011). Using bothSM and observed water depths, an annual minimum water depthf approximately 30. cm (1.0 ft) resulted in an average slough dryeason water depth of approximately 52 cm (1.7 ft). Therefore, wenterpreted the historical and mesocosm evidence (Table 1; McVoyt al., 2011; Richards et al., 2011) to estimate a suitable annual meanry season water depth of 45–61 cm (1.5–2.0 ft). These wet and dryeason water depths were used to define water depth metric targetshat would support N. odorata.

To account for temporal variability associated with varyinglimatic conditions, we fitted our respective metric targets tompirical frequency curves developed from a 1965–2000 periodf simulation. The targets used for all the metrics within appli-able ridge and slough areas were the hydroperiod, dry down,nd seasonal water depth frequency curves for NSM Cell C25 R21Figs. 3–6). The NSM at Cell C25 R21 (in Shark River Slough) approx-mately matched the empirical evidence (Table 1) defining suitableydrological conditions for N. odorata.

Table 2 summarizes the metrics and metric targets for the sloughegetation performance measure. We developed a scoring method-logy that calculated the percent of target achieved from a scenarioelative to an existing conditions baseline (Section 3). The perfor-ance measure was calculated for landscape units called indicator

egions (Fig. 2) that are groups of cells within the SFWMM grid thatontain similar hydrology, vegetation community structure, and

opography (Restoration Coordination and Verification, 2007). Wealculated the performance measure for indicator regions becausehey allow for a regional landscape analysis and because these

1 Mean water depths, mean water depth ranges, and an annual mean depth classere used for this calculation. For references with mean ranges, the median of the

ange was used in the calculation.

92–343 daysrolinianas (range)

regions contain field hydrologic monitoring gauges to which themodel was calibrated and exclude model domain areas that pro-duce less reliable output, such as at the model boundary andat water management structures (Restoration Coordination andVerification, 2007). The slough vegetation performance measurewas applied in the following indicator regions that were estimatedto represent the predrainage Everglades ridge and slough landscape(Lodge, 2010; McVoy et al., 2011): 100, 101, 102, 110, 111, 112, 113,114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,128, 129, 130, 131, 132, 133, and 160 (Fig. 2).

We applied the performance measure using hydrologic simu-lation output to estimate slough vegetation hydrologic suitabilityin the Everglades for existing hydrological conditions (ECB3,SFWMM version 6.0), future hydrological conditions without CERPimplementation (2015BS, SFWMM version 5.6.5), future hydro-logical conditions following the initial Band 1 phase of CERPimplementation (2015CP, SFWMM version 5.6.5), future hydrolog-ical conditions following complete CERP implementation (CERP0,SFWMM version 5.4), and simulated predrainage hydrology fromthe NSM.

We coded the performance measure calculations described inSection 3 using a Linux shell script. We used Microsoft® OfficeExcel® 2007 and ESRI® ArcMapTM 9.3.1 to display graphical andspatial performance measure output. We generated (average com-bined metric) spatial output for LNWR, WCA 2, WCA 3, andEverglades National Park within the estimated predrainage ridgeand slough landscape.

3. Performance measure calculations

Each of the four respective slough vegetation performancemeasure metrics was calculated (Sections 3.1–3.4) from SFWMMand NSM hydrologic model simulation output for individualridge and slough indicator regions. Existing conditions baselineoutput (ECB3) served as the baseline for performance measurecalculations for all model simulation output (2015BS, 2015CP,CERP0, and NSM) and was also scored as an alternative in theexisting conditions performance measure calculations. We usedthis scoring methodology so that benefits and negative impactsto slough vegetation hydrologic suitability relative to existingconditions could be evaluated. Relating scenario performance toexisting conditions provides resource managers and restorationplanners with a scenario score relative to a well-defined reference

benchmark. Existing conditions baseline (ECB3) scores differedfrom the scenario scores because in each year the target is notachieved, the score = 0. An ECB3 score of zero is assigned so thatscenarios represent lift from existing conditions. Only the ECB3

300 A.M. Lo Galbo et al. / Ecological Indicators 24 (2013) 294–304

Fig. 3. Empirical frequency curve of the slough vegetation hydroperiod performancemetric target. Return period is the recurrence interval for maximum continuoushydroperiods at the Natural System Model (NSM) Cell C25 R21 for the 1965–2000NSM simulation.

Fig. 4. Empirical frequency curve of the slough vegetation dry down performancemetric target. Return period is the recurrence interval for maximum continuous dryds

rstnpstd

Fig. 5. Empirical frequency curve of the slough vegetation wet season water depthperformance metric target. Return period is the recurrence interval for mean wetseason water depth at the Natural System Model (NSM) Cell C25 R21 for the1965–2000 NSM simulation.

Fig. 6. Empirical frequency curve of the slough vegetation dry season water depth

TS

own at the Natural System Model (NSM) Cell C25 R21 for the 1965–2000 NSMimulation.

eceives a score of zero when the target is not achieved. Thecenarios receive a score that is scaled between the ECB3 and thearget when the scenario performs better than the ECB3, but doesot meet the target. The scaled site-specific score represents theercent of target achieved relative to ECB3 at a respective ridge and

lough indicator region. Scores for the scenarios are provided ashe percent of performance measure target achieved as a relativeifference from existing (baseline) conditions, scaled from −100

able 2ummary of slough vegetation performance measure metrics, empirical evidence suppor

Metric Empirical evidence used to estimatemetric target

Continuous hydroperiod Near continuous inundation

Continuous dry down eventbelow 0.7 ft (20 cm)

Avoidance of dry down events below20 cm (0.7 ft)

Average wet season depth Approximately 61–91 cm (2.0–3.0 ft)

Average dry season depth Approximately 45–61 cm (1.5–2.0 ft)

performance metric target. Return period is the recurrence interval for mean dry sea-son water depth at the Natural System Model (NSM) Cell C25 R21 for the 1965–2000NSM simulation.

to 100. A positive scenario score indicates a relative improvement,whereas a negative score indicates worsening conditions.

The slough vegetation performance measure at each respectiveindicator region was computed annually by arithmetically averag-ing each of the four respective slough vegetation metrics. Annualoutput was arithmetically averaged to provide summarized output

for the entire period of record analyzed (1965–2000). Results forindicator regions analyzed were then arithmetically averaged toprovide results at a regional landscape level for LNWR, WCA 2,

ting metric targets, and metric targets (NSM = Natural System Model).

Metric target

NSM frequency curve representing near continuousinundation (Fig. 3).NSM frequency curve representing minimization of dry downevents < 20 cm (0.7 ft) (Fig. 4).NSM frequency curve representing an average wet seasondepth of ∼61–91 cm (∼2.0–3.0 ft) (Fig. 5).NSM frequency curve representing a dry season average depthof ∼45–61 cm (∼1.5–2.0 ft) (Fig. 6).

cal Indicators 24 (2013) 294–304 301

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35

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ECB3 2015BS 2015CP CERP0 NSM

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dry season depth wet season depth hydroperiod dry down average

Everglades National Park

Fig. 7. Slough vegetation performance measure scores for existing conditions base-line (ECB3) and for future conditions without Band 1 (2015BS), future conditionswith Band 1 (2015CP), future conditions with CERP (CERP0), and predrainage con-ditions (NSM) scenarios. The vertical dotted line separates the existing conditionsbaseline scores from the scenario scores. Output for the scenarios is provided asthe percent of performance metric/measure target achieved as a relative difference

A.M. Lo Galbo et al. / Ecologi

CA 3, and Everglades National Park respectively (Fig. 2). Southlorida Water Management Model output for indicator regions27 and 160 were included within the WCA 3 landscape score dueo their proximity to this landscape region. (For Eqs. (3.1)–(3.4),BS = absolute value, b = baseline, z = alternative, t = target.)

.1. Annual maximum continuous hydroperiod metric (days)

% = (((t − b) − (t − z))/(t − b)) ∗ 100

If b ≥ t & z < t % = −100

If z ≥ t % = 100

.2. Annual maximum continuous dry down metric (days)

% = (((t − b) − (t − z))/(t − b)) ∗ 100

If b ≤ t & z > t % = −100

If z ≤ t % = 100

.3. Annual mean wet season water depth metric

% = (((t − b) − (t − z))/(t − b)) ∗ 100

If b ≥ t & z < t % = −100

If z ≥ t % = 100

.4. Annual mean dry season water depth metric

% = ((ABS(t − b) − ABS(t − z))/ABS(t − b)) ∗ 100

If b = t & z /= t % = −100

If z = t % = 100

. Results

Slough vegetation performance measure output produced vary-ng results throughout the ridge and slough landscape. Resultsiffered between the landscape regions of LNWR, WCA 2, WCA, and Everglades National Park and within portions of individual

andscape regions (Figs. 7 and 8).Band 1 generally improved slough vegetation hydrologic suit-

bility (average metric) in LNWR, mainly through an improvementn hydroperiod (Fig. 7). Complete CERP implementation generallymproved hydrological suitability for slough vegetation within por-ions of LNWR as compared to Band 1 and existing conditionsFigs. 7 and 8(1)–(4)).

Band 1 generally improved hydrologic suitability for slough veg-tation in WCA 2 as compared to existing conditions and futureonditions without Band 1 (Figs. 7 and 8(1)–(3)). While completemplementation of CERP generally showed some minor improve-

ent to slough vegetation hydrologic suitability as compared toxisting conditions, hydrological suitability generally declined withERP implementation in WCA 2 as compared to Band 1 conditionsFigs. 7 and 8(1)–(4)).

Hydrological suitability for slough vegetation within WCA 3enerally declined with implementation of the Band 1 as com-ared to existing conditions and future conditions without Bandimplementation (Figs. 7 and 8(1)–(3)). Implementation of the

ERP generally indicated a minor improvement to slough vegeta-ion suitability within portions of WCA 3 as compared to existingonditions. Hydrological suitability for slough vegetation notablyeclined within WCA 3A east of the Miami Canal and within south-

rn WCA 3A with CERP implementation (Fig. 8(4)). In contrast,ydrological suitability within WCA 3B generally improved follow-

ng implementation of the CERP as compared to existing conditionsFig. 8(4)).

from the existing conditions baseline score (LNWR = Arthur R. Marshall LoxahatcheeNational Wildlife Refuge, NSM = Natural System Model, WCA = Water ConservationArea).

Band 1 generally provided a level of incremental benefits toslough vegetation hydrologic suitability in Everglades NationalPark that was then enhanced by implementation of the CERP(Figs. 7 and 8(1)–(4)). The results also indicate the severity of detri-mental effects to slough vegetation hydrologic suitability, notablydry down effects, within Everglades National Park without Band 1and the CERP implementation (Fig. 7).

The predrainage scenario results generally indicated lowerslough vegetation suitability in LNWR, WCA 2, and WCA 3 than theother scenarios (Figs. 7 and 8). In the ridge and slough landscape ofEverglades National Park, however, slough vegetation hydrologicsuitability was highest in the predrainage hydrologic simulationscenario as compared to all other modeled scenarios (Figs. 7 and 8).

5. Discussion

Our study results indicated that the level of hydrologic improve-ments with complete CERP implementation was insufficient to fullyrestore slough vegetation communities throughout the Evergladeslandscape. Benefits generally did not occur or were negligible in

302 A.M. Lo Galbo et al. / Ecological Ind

Fig. 8. Combined average slough vegetation performance metric output for (1)existing conditions baseline (ECB3), (2) future conditions without Band 1 (2015BS),(3) future conditions with Band 1 (2015CP), (4) future conditions with CERP (CERP0),and (5) estimated predrainage conditions (NSM). Output for the scenarios is pro-vided as the percent of performance measure target achieved as a relative differencefrom the existing conditions baseline score (LNWR = Arthur R. Marshall LoxahatcheeNational Wildlife Refuge, NSM = Natural System Model, WCA = Water ConservationArea).

icators 24 (2013) 294–304

northernmost LNWR and average metric output indicated lessthan a 25% overall improvement in slough vegetation hydrologicsuitability as compared to existing conditions (Figs. 7 and 8(4)).Negative impacts to slough vegetation hydrologic suitabilityoccurred within portions of southern WCA 2 and improvementsin slough hydrologic suitability were nearly negligible with CERPimplementation in this region overall (Fig. 8(4)). Slough vegetationsuitability improvements within WCA 3 with the CERP implemen-tation were nearly negligible, mainly resulting from the negativeimpacts that occurred east of the Miami Canal and within southernWCA 3A (Fig. 8(4)). This indicated that water deliveries to theseareas in WCA 3A were inadequate for slough vegetation restora-tion. While our results generally indicated improved conditionsin WCA 3B and Everglades National Park with implementationof the CERP, the benefits appeared insufficient to restore sloughvegetation communities throughout the full geographic extent ofShark River Slough and Taylor Slough (Figs. 7 and 8(4)). Results ofthe spatial analysis revealed only minor improvements to north-western and southeastern Shark River Slough and Taylor Slough(Fig. 8(4)).

While the CERP projects generally improved hydrologic suit-ability for slough vegetation in LNWR and Everglades NationalPark, additional restoration projects are needed to optimize sloughvegetation hydrologic suitability in these regions and all otherEverglades landscape regions analyzed. Our results indicate thatcontiguous slough vegetation restoration between the landscaperegions of LNWR, WCA 2, WCA 3, and Everglades National Park willnot occur with the CERP implementation alone. While the sloughvegetation performance measure was not used to specifically eval-uate the habitat connectivity of landscape regions, restoring sloughvegetation hydrologic suitability throughout the ridge and sloughlandscape is a priority for restoring overall ecological connec-tivity in the Everglades ecosystem. Such connectivity may benecessary to restore pattern to the landscape through channeledflow (Cohen et al., 2011; Larsen and Harvey, 2010; Larsen et al.,2007).

Results from the slough vegetation performance measure forthe NSM scenario in the WCAs contrasted with the paleoecolog-ical and historical literature, which showed that the predrainageera provided suitable conditions for slough vegetation throughoutthe ridge and slough landscape (Bernhardt et al., 2004; McVoy et al.,2011; Saunders et al., 2008; Willard et al., 2001a,b). This result maybe caused by inconsistencies with the assumed predrainage topog-raphy of the NSM, and inadequacies in modeled flow volumes, andevapotranspiration rates of the NSM. Improved topography andadvances in the hydrologic simulation of the predrainage Ever-glades may address such issues.

Validation of the slough vegetation performance measure willbe challenging because of the landscape-scale model output, whichcontrasts with the limited amount of field-verified spatial commu-nity data available for comparison. Another issue is that vegetationtransect data are collected at a finer spatial resolution than theslough vegetation performance measure output that is providedat a 2-mile by 2-mile resolution. However, vegetation transect datacollected in a comprehensive field study in 1999 throughout LNWR,WCA 2, WCA 3, and Everglades National Park (Stober et al., 2001)allow for a relative comparison to the slough vegetation perfor-mance measure output.

The existing conditions slough vegetation performance mea-sure output (Figs. 7 and 8(1)) matches general spatial vegetationpatterns in the Stober et al. (2001) field transect data. The fielddata reveal a more expansive spatial distribution of N. odorata

north of Everglades National Park; likewise, our results generallyindicate superior slough vegetation suitability in regions north ofEverglades National Park (Stober et al., 2001; Figs. 7 and 8(1)). Thenear absence of N. odorata in Everglades National Park in the field

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A.M. Lo Galbo et al. / Ecologi

ransect data matches our performance measure output indicatinghat current slough vegetation suitability is lowest in Evergladesational Park sloughs (Fig. 7). The highest scoring cells in theerformance measure output generally correspond to the highestecorded frequencies of N. odorata in the field data with few excep-ions (Fig. 8(1)). The wide range of performance measure scores ateld sites that lacked N. odorata is a notable disparity between theerformance measure output and the field data.

This disparity may result from comparing field data that wereollected at a much finer-resolution to the coarser-resolution mod-ling output. It could also result from other parameters affectingpecies distributions in these areas such as intraspecific compe-ition and responses to environmental parameters not evaluatedith the slough vegetation performance measure, such as water

uality. However, the relative match of some of the general spatialatterns from the performance measure output to the field transectata (Stober et al., 2001) provides support for use of this perfor-ance measure as an evaluation and assessment tool. Remotely

ensed data from satellite imagery provides another data sourceor model validations at the landscape level. Recent research usingemotely sensed data shows that Everglades slough communitiesan be mapped over relatively large extents using such data (Gannnd Richards, 2009; Gann et al., 2012).

The slough vegetation metrics rely on hydrologic model out-ut that is a simulated water surface elevation over an estimatedround surface elevation. Evaluations of hydrologic simulationodel output are affected by errors in both simulated water

urface elevations and the estimated ground surface elevations.e have reduced uncertainty by aggregating hydrologic simulation

utput from calibrated reference indicator regions and focusing oneneral spatial patterns. Thus, the slough vegetation performanceeasure is useful for providing relative comparisons between sim-

lated hydrologic scenarios but is not intended to be used asquantitative, predictive tool. Another source of uncertainty is

hat the NSM attempts to simulate the hydrologic response of theredrainage Everglades but utilizes modern rainfall and climatic

nputs. Therefore, a NSM simulation does not replicate the actualredrainage hydrology. It is also affected by the uncertainty previ-usly described regarding modeled elevations. The NSM does servepurpose as a planning tool, but our results indicate that its appli-

ation must be carefully considered and evaluated in relation tour scientific knowledge of the predrainage and modern-day Ever-lades ecosystem.

The slough vegetation performance measure evaluates theydrologic suitability of modeled restoration scenarios for sup-orting slough vegetation. It does not evaluate other abiotic andiotic parameters that affect the formation and sustainability ofhe ridge and slough microhabitat. Restoration of hydroperiods andydropatterns alone is not anticipated to fully restore the ridge andlough landscape (Watts et al., 2010). Therefore, the slough vege-ation performance measure is intended to be used in combinationith other performance measures that attempt to mimic biotic andhysicochemical ridge and slough formation processes such as flowelocity, flow direction, and floc depositional patterns. Additionalesearch and development of performance measures that mimicidge and slough dynamics within the Everglades landscape areecommended.

While this performance measure addresses hydrological param-ters that affect slough vegetation compositional patterns,egetation composition dynamics are affected by a complex inter-ction of other environmental parameters besides hydrology suchs water quality, storms, fire patterns, disturbance, climatic change,

nd wildlife (biotic) interactions. As our knowledge of the effects ofnvironmental parameters and their impacts on vegetation dynam-cs increases, further development and integration of additionalimulation models would be valuable.

icators 24 (2013) 294–304 303

6. Conclusions

We provided a case study for how to employ an ecological indi-cator defined by empirical data and historical evidence to developperformance metrics that can be used to evaluate future restorationscenarios. Our investigation indicates that the hydrologic suitabil-ity for N. odorata can be used to assess the relative effects of past,current, and future conditions on the Everglades slough vegeta-tion community. We applied the slough vegetation performancemeasure with hydrologic simulation output of the SFWMM andthe NSM to evaluate the effects of Everglades restoration scenariosin the Everglades. Our results indicate that additional restorationefforts besides the Band 1 and the CERP are needed to fully restoreslough vegetation communities in the extant Everglades ridge andslough landscape. The slough vegetation performance measure is aviable tool for resource managers and planners for evaluating rela-tive effects of restoration scenarios within the Everglades ridge andslough landscape.

Acknowledgements

We sincerely thank Chis McVoy, Winifred Park Said, JayanthaObeysekera, Joel VanArman, Thomas Dreschel, and the SouthFlorida Water Management District for providing the depiction ofthe estimated predrainage and modern-day Everglades landscape.We sincerely thank Jed Redwine, Doug Donalson, Erik Powers,Nick Aumen, Agnes Mclean, Jimi Sadle, and Daniel Gann for theirhelpful comments and suggestions. We sincerely thank Mark Sen-gelmann for his contributions to the graphics. Financial supportfrom the Critical Ecosystem Studies Initiative, Florida InternationalUniversity, and Everglades National Park was provided to developthis performance measure.

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