Estuaries Vol. 21, No. 48, p. 818-828 December 1998

Marsh Vegetation Types of the Mississippi River Deltaic Plain

JENNEKE M. VISSER!

CHARLES E. SASSER

Coastal Ecology InstituteLouisiana State UniversityBaton Rouge, Louisiana 70803

ROBERT H. CHABRECK

School ofForestry, Wildlife, and FisheriesLouisiana State University Agricultural CenterBaton Rouge, Louisiana 70803

R. G. LINSCOMBE

Louisiana Department of Wildlife and FisheriesRoute 4, Box 78New Iberia, Louisiana 70560

ABSTRACT: Marshes of the Mississippi River Deltaic Plain represent 17% of the coastal marshes in the continentalUnited States. However, only a few detailed descriptions of the diverse plant communities that occur in this large expanseof wetlands exist and none are based on detailed vegetation analysis. The objective of this study was to quantitativelyanalyze the vegetation data collected in the wetlands of the Barataria and Terrebonne estuary to determine naturallyoccurring vegetation associations. Two-way indicator species analyses (TWINSPAN) revealed nine vegetation types: po­lyhaline mangrove, polyhaline oystergrass, mesohaline mix, mesohaline wiregrass, oligohaline wiregrass, oligohaline mix,fresh bulltongue, fresh maidencane, and fresh cutgrass. These nine types form a logical expansion on the four salinityzones described for the region by previous studies and form a basis to compare the vegetation types of the MississippiRiver Delta region with other regions of the Atlantic and Gulf coasts.

Introduction

The Mississippi River Deltaic Region (MRDR) es­tuary complex contains the largest salt marsh areaand the second largest fresh marsh area in the con­tinental United States, representing 17% of thecoastal marshes in the continental United States(557,000 ha of fresh and salt marsh in the MRDRcompared to 3,216,000 ha of fresh and salt marshin the continental United States; Field et al. 1991).However, detailed descriptions of the diverse plantcommunities that occur in this large expanse ofwetlands have been few. Penfound and Hathaway(1938) provided the earliest descriptions of thecommunity types found in the MRDR. Their effortswere followed by O'Neil (1949), who published thefirst map of major vegetation associations for coast­al Louisiana, including the MRDR, as part of aninventory of muskrat habitat.

The most recent description of the major habi­tats within coastal Louisiana was by Chabreck et al.(1968) based on a vegetation survey of more than5000 stations. Chabreck (1970, 1972) delineated

I Corresponding author; tele: 225/388-6515; fax: 225/388­6376; e-mail: comvss@lsu.edu.

© 1998 Estuarine Research Federation 818

and mapped four vegetation zones (fresh, inter­mediate, brackish, and saline) mainly on the basisof Penfound and Hathaway'S (1938) descriptionsof the major vegetation types of the MRDR. Withinthese salinity zones several vegetation associationscan be distinguished (O'Neil 1949; Shiftlet 1963;White 1983; Visser et al. 1994; Sasser et al. 1995).However, the 1968 survey remains the only coast­wide vegetation study in Louisiana. In this paper,we revisit the 1968 data using quantitative tech­niques to describe in more detail the major vege­tation types occurring in one of the world's largestdeltas. Data analysis focused on Barataria andTerrebonne estuaries, which contain 77% (429,000ha) of the marshes of the MRDR (based on Fieldet al. 1991).

Methods

DATA COLLECTION

The 1968 Louisiana coastwide survey of vegeta­tion was funded by the Louisiana Wildlife and Fish­eries Commission and the United States ArmyCorps of Engineers. Sampling stations were locatedalong north-south transects spaced at 13-km (7.5'longitude) intervals (Fig. 1). Along these transects,

Marsh Vegetation Types 819

Ifa-________/ --------

22

I 25km I

23

24 25

LakePontchartrain

29

GulfofMexico 36

o

'" "

Fig. 1. Location of the vegetation transects in Barataria and Terrebonne basins. Transect numbers are those used by Chabreck(1972). Terrebonne Basin is the area between the Atchafalaya River and Bayou Lafourche. Barataria Basin is the area between BayouLafourche and the Mississippi River.

stations were located at O.4-km intervals (0.25mile) starting from the Gulf of Mexico.

Vegetation was surveyed by one observer from ahelicopter hovering above the station. Each speciesoccurring in a 30-m (100-ft) radius from the sta­tion was recorded and assigned an abundance val­ue (3 = abundant, 2 = common, and 1 = rare).Species identification was improved by landing atevery eighth station and collecting unknown spec­imens. Specimens were returned to the laboratoryand identified. In addition, the station was classi­fied as natural marsh, forested (shrubs or trees),dewatered marsh, open water, beach, natural leveeor ridge, spoil bank, or developed. Plant speciesnomenclature follows Godfrey and Wooten (1981),

except for ferns which follows Correll and Correll(1975).

ANALYSES

For the analyses in this study, only those stationsclassified as natural marsh were used. Before thestart of the analyses all submerged, free-floating,and tree species were removed from the dataset,so that only emergent marsh vegetation was in­cluded in the analysis. Some species that were dif­ficult to identify correctly using helicopter surveys,such as some grasses and sedges, were grouped bygenus. Mter this, species occurring in less than fivestations (approximately 1% of the stations) wereremoved to reduce the influence of these rare spe-

820 J. M. Visser et al.

cies in the analyses, and reduce instability in theanalysis (Tausch et al. 1995).

Separate datasets were compiled for Baratariaand Terrebonne basins. These datasets were clas­sified using two-way indicator-species analysis(TWINSPAN) with the default setting of the pro­gram (Hill 1979). TWINSPAN was chosen over oth­er classification strategies because this techniquebest reflects the intuitive phytosociologic classifi­cation of vegetation types (Dale 1995).

Results

COMPARISON AMONG BASINS

TWINSPAN revealed nine vegetation types forthe deltaic plain (Fig. 2). For both basins the firstsplit seems to differentiate between high and lowsalinity stations. Indicator species identified for thehigh salinity plots were Spartina alterniflora and Dis­tichlis spicata (in both basins), Spartina patens (Bar­ataria) , and funGus roemenanus (Terrebonne). Incontrast, indicator species for low salinity plotswere Panicum hemitomon and Eleocharis spp. (inboth basins), Sagittaria lancifolia (Barataria), andTypha spp. (Terrebonne). The second level sepa­rates the high salinity plots into polyhaline and me­sohaline, with Spartina alterniflora as the indicatorspecies for polyhaline marsh and Spartina patens formesohaline marsh. At the same level, low salinityplots are divided into oligohaline and fresh, withthe combination of Spartina patens and Bacopa mon­nieri as indicators for oligohaline and Panicum hem­itomon as an indicator for fresh. The naming of thevegetation types uses the salinity zones of coastalmarshes as described by Odum et al. (1984) com­bined with common names for the dominant plantspecies. Subsequent splits are different for each ba­sin. However, resulting vegetation types are verysimilar for both basins (Fig. 2).

The percentage occurrence of vegetation typesin each basin shows several differences (Fig. 3).Barataria Basin has larger percentages of mesoha­line marshes, while Terrebonne Basin has largerpercentages of fresh and polyhaline marshes.

VEGETATION 'TYPES

Polyhaline mangrove is characterized by thepresence of Avicenia germinans. However, it isequally dominated by Spartina alterniflora and Batismaritima (a complete list of species observed ineach vegetation type is provided in Appendices 1and 2). Polyhaline mangrove has relatively low spe­cies richness (Table 1), is uncommon in BaratariaBasin, and is slightly more common in TerrebonneBasin (Fig. 3). Avicennia germinans reaches itsnorthernmost range in Louisiana as a dwarf shrubgrowth form. It occurs mostly flanking the largebays (Fig. 4) on the protected side of barrier is-

lands, as well as on a few islands on the northernedge of the bays.

Polyhaline oystergrass is the common "saltmarsh" association abundant in both basins (Fig.3). Polyhaline oystergrass is always dominated bySpartina alterniflora, sometimes with funGUs roemeri­anus as a co-dominant. It occurs mostly flankingthe large bays (Fig. 4). Number of species per sta­tion is the lowest of all described vegetation types(Table 1).

Mesohaline mix is without a clear dominant andcan be described as a mixture of Spartina alterniflo­ra, Spartina patens, and Distichlis spicata. Speciesrichness of mesohaline mix is higher than in thepolyhaline oystergrass. This vegetation type isabundant in Barataria Basin and common in Terre­bonne Basin (Fig. 3). It occurs just inland from thepolyhaline vegetation types (Fig. 4).

Mesohaline wiregrass is always dominated bySpartina patens, sometimes with Distichlis spicata asa co-dominant. It occurs generally just inland fromthe mesohaline mix (Fig. 4). Mesohaline wiregrassis similar in species richness to the mesohaline mix(Table 1). Mesohaline wiregrass is abundant inBarataria Basin and common in Terrebonne Basin(Fig. 3).

Oligohaline wiregrass generally occurs just in­land from the mesohaline wiregrass (Fig. 4). Likemesohaline wiregrass, oligohaline wiregrass is al­ways dominated by Spartina patens. However, Dis­tichlis spicata is occasionally present with a lowabundance. Scirpus americanus is a frequent co­dominant in this type. In addition, oligohalinewiregrass has a higher species richness than themesohaline wiregrass (Table 1). This vegetationtype is common in both basins (Fig. 3).

Oligohaline mix generally occurs interspersedwith the oligohaline wiregrass (Fig. 4). Oligohalinemix is clearly dominated by Sagittaria lancifolia inthe spring, but this might be less clear in the fall.In the fall, oligohaline mix is characterized by theco-occurrence of Sagittaria lancifolia with Cyperusspp. and Bacopa monnieri. Oligohaline mix has thehighest number of species per station (Table 1).Oligohaline mix is common in both basins (Fig.3).

Fresh bulltongue is always dominated by Sagit­taria lancifolia and is frequently co-dominated byPanicum hemitomon and Eleocharis spp. This vegeta­tion type can be distinguished from the oligoha­line mix based on the absence of Bacopa monnieriand the presence of ferns (Thelypteris palustris andOsmunda regalis) , Myrica cerifera, and Hydrocotylespp. Fresh bulltongue has relatively high speciesrichness. It occurs generally inland from the oli­gohaline vegetation types and is often found inter­spersed with the fresh maidencane type (Fig. 4).

Marsh Vegetation Types 821

Barataria Basin

Saline Fresh

Spartina alterniflora Spartina patens

84860

Spartina patens /Bacopa monnieri

44329072683

PolyhalineMangrove

MesohalineMix

OligohalineWiregrass

FreshBulltongue

FreshCutgrass

PolyhalineOystergrass

MesohalineWiregrass

OligohalineMix

FreshMaidencane

Terrebonne BasinSaline Fresh

Spartina patens /Bacopa monnieri

30 115 41 48 70 27 58 108 15

PolyhalineMangrove

MesohalineMix

OligohalineWiregrass

FreshBulltongue

FreshCutgrass

PolyhalineOystergrass

MesohalineWiregrass

OligohalineMix

FreshMaidencane

Fig. 2. Summary of the results from the TWINSPAN analyses for vegetation data from Barataria and Terrebonne basins. Speciesat each fork are important indicator species for the division; however, not all indicator species used in the division are listed. Numbersindicate the number of stations within each vegetation type.

This vegetation type is common in both basins(Fig. 3).

Fresh maidencane is dominated by Panicum hem­itomon. The species richness (5.8 species per stationwith a total of 55 species observed) of the freshmaidencane marsh is slightly lower than the freshbulltongue marsh. It occurs in large expanses inthe interior of the estuaries, sometimes inter­spersed with the fresh bulltongue (Fig. 4). Thisvegetation type is abundant in Terrebonne Basinand common in Barataria Basin (Fig. 3).

Fresh cutgrass is dominated by Zizaniopsis mili-

acea, with Panicum hemitomon as a frequent co-dom­inant. Within the fresh marsh this vegetation typehas the lowest species richness (4.3 species per sta­tion with a total of 23 species observed). It occursmostly along the natural levee of Bayou Lafourche(Fig. 4). This vegetation type is uncommon in bothbasins (Fig. 3).

Discussion

The nine vegetation types described in this pa­per are a logical expansion from the four vegeta­tion-salinity zones previously described by Pen-

822 J. M. Visser et al.

Barataria

2% 1%

lO%~_TII14%

8% 21%

Terrebonne

3% 6%

17%

22%

8%

II Polyhaline Mangrove

Polyhaline Oystergrass

§ Mesohaline mix

[[]ill Mesohaline Wiregrass

mOligohaline Wiregrass

mOligohaline mix

IT] Fresh Maidencane-Bulltongue

~ Fresh Maidencane

D Fresh Cutgrass

14%Fig. 3. Percent occurrence of each vegetation type in Barataria and Terrebonne basins.

TABLE 1. Number of species in each vegetation type.

found and Hathaway (1938) and Chabreck (1970)for coastal Louisiana. These previously describedvegetation-salinity zones are as follows:

Saline Marsh: This vegetation zone is a combi­nation of Spartina alterniflora, Juncus roemerianus,Batis maritima, Avicennia germinans, and Distichlisspicata. Salinity 18%0 (range 8-29%0).

Brackish Marsh: This vegetation zone is a com­bination of Spartina patens, Scirpus americanus, Scir­pus robustus, and Eleocharis parvula. Salinity 10%0(range 4-18%0).

Intermediate Marsh: This vegetation zone is acombination of Spartina patens, Vigna luteola, Scir­pus califomicus, Echinochloa walteri, Sagittaria sp.,Cladium jamaicense, and Phragmites australis. Salinity4%0 (range 2-8%0).

Vegetation Type

Polyhaline mangrovePolyhaline oystergrassMesohaline mixMesohaline wiregrassOligohaline wiregrassOligohaline mixFresh bulltongueFresh maidencaneFresh cutgrass

AverageSpecies per Station

4.32.74.04.67.68.07.05.84.3

TotalSpecies

142630375549525523

Fresh Marsh: This vegetation zone is a combi­nation of Panicum hemitomon, Hydrocotyle sp., Ponte­deria cordata, Sagittaria sp., and Althernantera philox­eroides. Salinity 0%0 (range 0-3%0).

Polyhaline mangrove and polyhaline oystergrasscompose the saline marsh of previous authors. Thepolyhaline mangrove vegetation type is relativelyrare in Barataria Basin (the area used by Penfoundand Hathaway to define their marsh types) andtherefore was probably not recognized as a differ­ent type in the qualitative analysis. This vegetationtype reflects the northern range of Avicenia germi­nans and can also be found in Florida and Texas(Chapman 1977; Montague and Wiegert 1990).

The polyhaline oystergrass vegetation type oc­curs throughout the eastern coast of North Amer­ica (Chapman 1960; Teal 1986; Montague andWiegert 1990; Wiegert and Freeman 1990). In NewEngland, this vegetation type is commonly referredto as low marsh (Niering and Warren 1980; Bert­ness and Ellison 1987). Along the Gulf of Mexicocoast to the east of the MRDR, salt marshes aresometimes characterized by monocultures of Jun­cus roemerianus (Eleuterius 1976; Montague andWiegert 1990). Our results show that this speciesoccurs as a frequent co-dominant in the polyhalineoystergrass marsh.

The mesohaline mix vegetation type seems to be

LakePontchartrain

Interspersed Vegetation Types

/HI Fresh MaidencanelFresh Bulltongue

IT] Fresh Bulltongue/Oligohaline Mix

Gl OligohalinelMesohaline Wiregrass

~ Mesohaline MixlMesohaline Wiregrass

~ Polyhaline OystergrasslMesohaline Mix

21 22

I 25 kill I

23 .' j., • • : gO"';'~oii~ 27~'-=='24 25 26 28 29

Marsh Vegetation Types 823

Vegetation Types

Fresh Cutgrass

Fresh Maidencane

Fresh Bulltongue

Oligohaline Mix

Oligohaline Wiregrass

Mesohaline Wiregrass

Mesohaline Mix

~ Polyhaline Oystergrass

~~ Polyhaline Mangrove

d'~..~ I''lt~~~l?*.Pl l> 0 0l;; d

~

GulfofMexico 36

Fig. 4. Distribution of vegetation types along transects. Breaks indicate areas not occupied by marsh. Areas of the coast where twovegetation types were found interspersed are indicated. However, individual stations within these areas possessed one of the twovegetation types.

a transition zone from the saline to the brackishmarsh. Palmisano (1970) considered this vegeta­tion type, without Spartina alterniflora as the cleardominant, a brackish marsh. The occurrence ofDistichlis spicata in the mesohaline mix generallyindicates a slightly higher elevation than the ele­vation in the polyhaline oystergrass vegetation type(Shiflet 1963; Sasser 1977; Bertness and Ellison1987; Wiegert and Freeman 1990). The mesoha­line wiregrass vegetation type is similar in speciescomposition to the brackish marsh in the qualita­tive analysis (Chabreck 1970; see above). White(1983) classified what we call mesohaline wiregrass(marsh dominated by Spartina patens with low spe­cies diversity) as saline marsh for the Pearl Riverestuary in Louisiana. The mesohaline wiregrassvegetation type seems very similar in species com­position to the high marsh as it has been describedfor the New England coast of the United States(Niering and Warren 1980; Bertness and Ellison1987). Along the southeastern Atlantic, mesoha­line wiregrass is relatively uncommon and usuallyconfined to small patches or to a narrow fringeshoreward of the polyhaline oystergrass marsh(Wiegert and Freeman 1990). In Louisiana, themesohaline marsh can be several kilometers wide.This might be due to the gentle slope of the coastand the small tidal amplitude (30 cm) along theGulf Coast.

The intermediate marsh is divided into the oli­gohaline wiregrass and the oligohaline mix. Otherstudies. (Sasser et al. 1994; Visser et al. 1994; Sasseret al. 1996) have mentioned these different vege­tation types in the intermediate salinity zone of theLouisiana coast. Visser et al. (1994) calls the oli­gohaline mix a Bacopa marsh, characterized by Ba­copa monnieri, Sagittaria lancijolia, Eleocharis spp.,Pluchea camphorata, and Leptochloa jascicularis, whileSasser et al. (1994) calls this marsh type Sagittarialancifolia intermediate marsh. The oligohalinewiregrass marsh seems very similar in species com­position to the floating-brackish marshes describedby O'Neil (1949). No descriptions of similar oli­gohaline vegetation types outside of Louisianawere found in the literature. Along the southeastAtlantic Coast oligohaline marshes are dominatedby Spartina eynosuroides (Wiegert and Freeman1990).

The fresh maidencane and the fresh bulltonguevegetation type have been previously described byWhite (1983) and Sasser et al. (1995). Both thesevegetation types can occur on floating mats. Everset al. (1996) mapped 95% of the maidencanemarsh and 51 % of the fresh bulltongue as floatingmarshes in Barataria and Terrebonne basins. Pan­icum hemitomon-dominated marshes occur in cen­tral Florida under two different environmental re­gimes (Kushlan 1990): flag marshes (moderate hy-

824 J. M. Visser et al.

droperiod and fire frequency) and wet prames(short hydroperiod and high fire frequency). Nodescriptions of vegetation associations similar tothe fresh bulltongue were found in the literature.Therefore, the fresh bulltongue type seems to beunique to the Louisiana coast. In Florida, the Clad­ium jamaicense-dominated Everglades are the mostcommon freshwater marsh (Kushlan 1990). Alongthe mid-Atlantic Coast fresh tidal marshes are of­ten mixtures which include Peltandra virginica, Pon­tederia cordata, Zizania aquatica, and Typha spp.(Odum et al. 1984). Similar mixtures are alsofound in some of the fresh marshes of central Flor­ida (Kushlan 1990), while along the north Atlantic,fresh marsh is composed of perennial grasses (e.g.,Calamagrostis canadensis) and sedges (Odum et a1.1984).

The fresh cutgrass is a vegetation type previouslydescribed by Shiflet (19163) as occurring on firmmineral soils in the Chenier Plain of Louisiana.Fresh cutgrass also occurs along the Atlantic coastsouth of Virginia and Maryland in tidal freshwatermarshes (Odum et al. 1984).

ConclusionThe nine vegetation types classified using TWIN­

SPAN form a logical extension of the four vegeta­tion zones identified for the MRDR by previousauthors. This new classifilcation provides a basis toachieve consistency for comparisons within vege­tation types rather than within the very broad sa­linity zones that have been extensively used by Lou­isiana ecologists for the last 30 yr. This is especiallyimportant in light of the serious land loss and as­sociated changes in the region (Craig et a1. 1979;Gagliano et a1. 1981; Scaiife et a1. 1983; Sasser et a1.1986; Walker et a1. 1987; Evers et a1. 1992; Boeschet al. 1994). As new vegetation datasets are assem­bled our classification utilizing the 1968 databasewill provide a substantial baseline for quantitativeanalyses relating vegetation change to forcing fac­tors such as subsidence, sea-level rise, hydrologicmodification, hurricanes, and development. Mostof the vegetation types described in this paper aresimilar to vegetation types described for the Atlan­tic and Gulf coasts of the United States. Only thetwo oligohaline vegetation types and the fresh bull­tongue vegetation type appear to be restricted toLouisiana.

ACKNOWLEDGMENTS

This study was funded by the Barataria-Terrebonne NationalEstuary Program. The comments of three anonymous reviewersgreatly improved this paper.

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Marsh Vegetation Types 825

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Received for consideration, April 15, 1997Accepted for publication, March 31, 1998

Appendix 1. Condensed TWINSPAN output for Barataria Basin. Consistency classes are as follows: + = <5% of the stations, I = 5-20%, II = 21-40%, III = 41-60%, IV = 61-80%, and V = 81-100%.

Vegetation Type I

Species PM PO MM MW OW OM FB FM FC

Spartina alterniflora II V V IISalicornia virginica IV + +Avicennia germinans V IJuncus roemerianus IV III II +Borrichia frutescens II + + +Batis maritima IV I I +Iva frutescens IV I I II + + +Spartina eynosuroides + + IScirpus robustus I IDistichlis spicata II II V IV ISpartina patens + V V IV IIpomoea sagittata + I I IBaccharis halimifolia I I I I +Aster subulatusl tenuifolius + I I IAmaranthus australis + I I I +Scirpus americanus + + I II IIEleocharis parvula I II I ISetaria magna I I I + +Lythrum lineare I I IKosteletzkya virginica + I I +Pluchea camphoratalfoetida + + I IV II ISolidago sempervirens + I + +Setaria geniculata + I + +Phyla lanceolatal nodiflora IEchinochloa walteril crusgalli + II IV IBacopa monnieri + IV III +Leptochloa fascicularis I +Cyperus spp. + + IV IV I IIVigna luteola + + II II ISesbania drummondiil macrocarpa + + + I I IPolygonum punctatum + + II IHibiscus lasiocarpus + I I + +Eleocharis spp. + I V III III IIITypha latifolial domingensis + I III III +

826 J. M. Visser et al.

Appendix l. Continued.

Vegetation Type l

Species PM PO MM MW OW OM FB FM Fe

Sagittaria lancifolia + + V V V IIEupatorium capillifolium + + + + +Scirpus californicus/validus I I I I IIAlternanthera philoxeroides I ISagittaria latifolia I +Phragmites australis + I IMyrica cerifera + I III IHydrocotyle spp. I II II IIILudwigia leptocarpa/peploides + + + I IIThelypteris palustris/ Osmunda regalis I IZizaniopsis miliacea + II II VPanicum hemitomon II IV V IVLimnomum spongia IDecodon verticillatus + + I IV ICephalanthus occidentalis .r II V

Species omitted from the analysis

Aeschynomene indica +Agalinis maritima +Ammania coccinea + +Andropogon virginicus +Bidens laevis + +Chenopodium allntm +Cladium jamaicenseCuscuta indecora +Dichromena colorata + +Erianthus giganteus +Euphorma spp. + + + +Panicum spp. + +Paspalum distichum +Philoxerus vermicularisPhytolacca americana + +Pontederia cordata +Rhynchospora spp. +Saururus ceruuus + +Triadenum virginicum + +Verbena spp. + +1 PM = Polyhaline Mangrove.PO = Polyhaline OystergrassMM = Mesohaline Mix.MW = Mesohaline Wiregrass.OW = Oligohaline Wiregrass.OM = Oligohaline Mix.FB = Fresh Bulltongue.FM = Fresh Maidencane.FC = Fresh Cutgrass.

Marsh Vegetation Types 827

Appendix 2. Condensed TWINSPAN output for Terrebonne Basin. Consistency classes are as follows: + = <5% of the stations, I =5-20%, II = 21-40%, III = 41-60%, IV = 61-80%, and V = 81-100%.

Vegetation Type

Species PM PO MM MW OW OM FB FM Fe

Borrichia frutescens II + + +Batis maritima IV + IAvicennia germinans V +Salicornia virginica II I I +Spartina alterniflora V V V IIfunGUs roemerianus + IV II II + +Iva frutescens III I + II +Scirpus rolmstus I IFimlJristylis castanea + I I + +Distichlis spicata II III V IV I I +Spartina patens I II V V V II I +Spartina cynosuroides I I I + +Baccharis halimifolia + + II I I I +Lythrum lineare + I I II +Agalinis maritima + I + + IAmaranthus australis + + I I II + +Vigna luteola + + III I IScirpus americanus II III I + +Sesbania drummondii! macrocarpa + + I III I + +Pluchea camphorata!foetida + I II V I ISetaria magna + + I II I +Setaria geniculata + I I I + +Aster sulmlatus! tenuifolius + + I I IKosteletzkya virginica I I IIIpomoea sagittata II I I +Cyperus spp. + III IV II IILeptochloa fascicularis III +Bacopa monnieri II IV I +Phyla lanceolata! nodiflora I IEchinochloa walteri! crusgalli I IV II I IAlternanthera philoxeroides + I + IIPanicum spp. I +Paspalum distichum I I +Hibiscus lasiocarpus + I + I IEleocharis parvula + + I I +Cladium jamaicense I I ISagittaria lancifolia II III V IIPolygonum punctatum + I I +Phragmites australis II II IScirpus californicus! validus I + + IEupatorium capillifolium + + I I I IEleocharis spp. I II III III IVThelypteris palustris! Osmunda regalis I III + ITypha latifolia!domingensis + II IV III IIMyrica cerifera I IV I IILudwigia leptocarpa!peploides + I II IHydrocotyle spp. I + IL IV IISolidago sempervirens + + IPanicum hemitomon + I IV V IITriadenum virginicum + IDichromena colorata + + IDecodon verticillatus I ICephalanthus occidentalis + III IBidens laevis +Zizaniopsis miliacea + I VSagittaria latifolia + III

Species omitted from the analysisAeschynomene indica +Andropogon virginicus +Boehmeria cylindrica +Centella asiatica +Chenopodium allmmColocasia esculenta + +

828 J. M. Visser et al.

Appendix 2. Continued.

Species

Cuscuta indewraConoclinium coelestinum/Eupatorium perfoliatumEuphorlJia spp.Habenaria repensHeliotrapium curassavicumIris spp.Lobelia cardinalisPhiloxerus vermicularisPhytolacca americanaPontederia cordataRanunculus spp.Rhynchospora spp.Saururus cernuus&suvium portulacastrumSonchus spp.Suaeda maritimaTriglochin striataXyris iridifolia

1 PM = Polyhaline Mangrove.PO = Polyhaline OystergrassMM = Mesohaline Mix.MW = Mesohaline Wiregrass.OW = Oligohaline Wiregrass..OM = Oligohaline Mix.FB = Fresh Bulltongue.FM = Fresh Maidencane.FC = Fresh Cutgrass.

Vegetation Type

PM PO MM MW OW OM FB FM Fe

+ ++ + +

+ + I ++

++

++

++++

+ ++

++ +

++