CAN REWATERING REVERSE THE EFFECTS OF REGIONAL DRAINAGE
ON FOREST COMMUNITIES OF THE BIG CYPRESS SWAMP?
by
Scott M. T. Park
A Thesis Submitted to the Faculty of
The Charles E. Schmidt College of Science
in Partial Fulfillment of the Requirements for the Degree of
Master of Science
Florida Atlantic University
Boca Raton , Florida
May 2002 Can rewatering reverse the effects of regional drainage on forest
communities of the Big Cypress Swamp?
by
Scott M. T. Park
This thesis was prepared under the direction of the candidate's thesis advisor, Dr. John C. Volin, Division of Biological Sciences, and has been approved by the members of his supervisory committee. It was submitted to the faculty of The Charles E. Schmidt College of Science and was accepted in partial fulfillment of the requirements for the degree of Master of Science.
SUPERVISORY COMMITTEE:
Dr. Daniel F. Austin
Dr. William A. Dunson
Director, Envrronmental Sciences Program
Vice Provost
II ACKNOWLEDGEMENTS
I wish to thank Dr. John C. Volin for his mentoring and research assistantship throughout my studies. Also, Dr. Daniel F. Austin and Dr. William A. Dunson for their continued guidance to focus my efforts through numerous turns in the thesis process. In addition, I would like to express my sincere gratitude to Dr.
Dianne Owen for her "youthful enthusiasm" with statistical analysis.
I am truly grateful to everyone who has helped me to collect data.
Especially, I would like to thank Michelle DaCosta, Jordan Muss, Michael Lott,
John Erickson and Molly Taylor for their willingness to "swamp tromp" to sampling sites.
Most importantly, I would also like to thank Dara Park, who helped me enjoy the rain as well as the sunny weather.
This study has been funded by the Seminole Tribe of Florida. Their support was greatly appreciated.
Ill ABSTRACT
Author: Scott M. T. Park
Title: Can rewatering reverse the effects of regional drainage on
forest communities of the Big Cypress Swamp?
Institution: Florida Atlantic University
Thesis Advisor: Dr. John C. Volin
Degree: Master of Science
Year: 2002
The impact of five years of rewatering on a desiccated forested wetland within the Everglades Big Cypress Swamp was investigated. It was found that
rewatering generally resulted in a shift in species composition along a
hydrological gradient. This was particularly evident in the seedling and
herbaceous layer of the cypress domes, the most hydric community studied, where obligate and facultative wetland species had their highest species
richness. Overall there were no detectable differences in the number of non
indigenous species in rewatered compared to reference sites. Results from th is short-term study showed that rewatering may potentially reverse the trend of increasing coverage by non-obligate wetland plants that have established in the past century as a result of regional desiccation.
IV T ABLE OF C ONTENTS
LIST OF TABLES ...... v i
LIST OF FIGURES ...... vii
INTRODUCTION ...... 1
MATERIALS AND METHODS ...... 6
RESULTS ...... 18
DISCUSSION ...... 32
CONCLUSIONS ...... 38
APPENDIX A ...... 40
APPENDIX B ...... 41
APPENDIX C ...... 42
LITERATURE CITED ...... 46
v LIST OF TABLES
TABLE 1. COMPARISON BETWEEN DIFFERENT SAMPLING TECHNIQUES TO FIND CANOPY TREE DENSITY ...... 13
TABLE 2. COMPARISON OF AVERAGE ECOLOGICAL PARAMETERS BETWEEN TREATMENT AND HABITAT TYPE ...... 22
TABLE 3. A LIST OF SIGNIFICANT COMPARISONS BETWEEN SAC AND REFERENCE SITES IN TERMS OF THE CHANGES IN SPECIES WETLAND CLASSIFICATION TYPE ...... 29
TABLE 4. DISTRIBUTION OF NON-INDIGENOUS PLANT SPECIES BETWEEN THE SAC AND REFERENCE SITES ...... 30
VI LIST OF FIGURES
FIGURE 1. STUDY AREA DRAINAGE BASIN ...... 7
FIGURE 2. STUDY SITES INCLUDING SAC IMPOUNDMENT...... 8
FIGURE 3. STUDY SITES ...... 10
FIGURE 4. STUDY SITES ...... 11
FIGURE 5. SPECIES AREA CURVES FOR CYPRESS, CYPRESS-MAPLE, LAUREL OAK, AND LIVE OAK SAC AND REFERENCE HABITATS ...... 15
FIGURE 6. WATER DEPTHS OF SAC FORESTED COMMUNITIES IN 1999 AND 2000 ...... 19
FIGURES 7 AND 8. TREATMENT AND REFERENCE SITE COMPARISION ACROSS HABITATS ...... 20
FIGURE 9. CANOPY SPECIES RICHNESS IN CYPRESS, CYPRESS-MAPLE, LAUREL OAK, AND LIVE OAK COMMUNITIES ...... 23
FIGURE 10. SUBCANOPY SPECIES RICHNESS CYPRESS, CYPRESS- MAPLE, LAUREL OAK, AND LIVE OAK COMMUNITIES ...... 24
FIGURE 11 . SHRUB SPECIES RICHNESS CYPRESS, CYPRESS-MAPLE, LAUREL OAK, AND LIVE OAK COMMUNITIES ...... 25
FIGURE 12. HERB SPECIES RICHNESS CYPRESS, CYPRESS-MAPLE, LAUREL OAK, AND LIVE OAK COMMUNITIES ...... 26
FIGURE 13. SEEDLING SPECIES RICHNESS IN CYPRESS, CYPRESS- MAPLE, LAUREL OAK, AND LIVE OAK COMMUNITIES ...... 27
V II INTRODUCTION
Southern Florida has been subjected to many anthropogenic alterations in hydrology to guarantee freshwater availability and flood protection for agriculture and urban development. Hydrology is one of the primary factors influencing wetland ecology throughout Florida (Mitsch and Ewel 1979, Duever
1984). The anthropogenic alteration of the regional hydrology, through the construction of a vast network of canals, levees and water control structures, that began in the early 1900's, has had a substantial negative impact on the greater Everglades ecosystem. Largely as a result of these negative impacts, the world's largest ecosystem restoration project, or Comprehensive
Everglades Restoration Plan, was formally initiated in 2000. One of the main goals of Comprehensive Everglades Restoration Plan is to substantially improve regional hydrology in selected natural areas.
Many studies have focused on hydrology and its effects on herbaceous plant diversity (Walker 1965, Spence 1982, Sjoberg and Danell 1983, Wallsten and Forsgren 1989, Squires 1991 , van der Valk 1991 , Squires and van der
Valk 1992, van der Valk eta/. 1994, Jordan eta/ 1997). In general, these researchers have found decreased plant diversity with increased hydroperiod in herbaceous dominated wetlands. Mitsch and Ewe I ( 1979) explored biomass and growth of cypress (Taxodium distichum) under different hydrological treatments and although they focused only on one species as opposed to an entire community, they found that cypress were most productive under riverine conditions where a short inundation period eliminated competing , flood-intolerant species. Reed (1998) reported a list of wetland plants and their hydrological dependencies as indicator categories: obligate (>99% occurrence in wetlands) , facultative wetland (67 to 99%), facultative (34 to 66%), facultative upland species (1 to 33%) and upland species (<1% occurrence in wetlands). Although herbaceous wetlands have been the focus of many studies, current literature explains little about the impact of increased hydrology on the structure and composition of forested wetlands.
In addition to hydrology, interaction with nonindigenous species is often a major feature of the control of forest structure (U .S. Congress 1993,
Simberloff 1997). The Florida Exotic Pest Plant Council (FLEPPC) publishes an annual list of the most invasive nonindigenous species in the State
(FLEPPC 2001 ). FLEPPC (2001) groups the most invasive species into two categories: Category I and Category II . Category I invasive species are defined as "invasive exotics that are altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives (FLEPPC 2001 )." Category II includes exotic invasive species that have not yet altered native habitats (FLEPPC
2 2001 ). Native habitats which have been greatly affected by anthropogenic disturbances such as altered hydrology and physical disturbance tend to be more susceptible to invasion by nonindigenous plant species (Ewel 1986,
Schmitz et a/. 1997). For instance, Duever (1984) reported that melaleuca
(Melaleuca quinquenervia) , a Category I native Australian plant species
(FLEPPC 2001 ), is found in areas affected by decreased hydrology where the native Everglades plant communities may be stressed by "drier-than-normal" conditions. Of course, the invasive characteristics of such plants may also be independent of hydrological change.
Twenty-seven percent of the historic Greater Everglades ecosystem consisted of the Big Cypress Swamp, a forest-dominated wetland system.
Like the sawgrass marsh Everglades, the Big Cypress Swamp has also undergone severe drainage and decreased spatial extent over the last half century (Fennema et a/. 1994, Ogden et a/. 1999). In many restoration projects, the goal is to re-establish a historic, seasonal hydropattern.
However, the amount of water needed is not known for certain , and few restoration projects involve adequate replication and tests of experimental hypotheses. The difficulty is compounded when determining the impact of restoration on native habitats that are dominated by long-lived woody species, as compared to relatively short-lived herbaceous species. As a result, little is
3 known about the cause and effect relationships of rewatering desiccated, forested wetlands.
The purpose of this study was to determine the effects of increased
hydrology on the structure and composition of four forested communities in the
Everglades Big Cypress Swamp. The four communities are historically differentiated by slight differences in elevation, which correspondingly
impacted their hydrology. These communities, along a hydrological gradient from hydric to mesic, were cypress domes, cypress-maple forests, laurel oak
hammocks, and live oak hammocks. I hypothesized that a shift in species composition and diversity in the seedling, herbaceous and shrub layers would occur across this gradient after rewatering over a five year period .
Specifically, obligate wetland species would dominate these layers in the two
rewatered cypress communities and diversity would decrease as a result of a decrease in facultative wetland and upland plant species. In the two oak communities, facultative wetland species would increase in richness and abundance in these three layers, but diversity would still be less than the non
rewatered reference communities. I further hypothesized that the two canopy
layers would not show a significant difference in composition or diversity from
reference sites after five years of rewatering , since only longer-term responses would typically be apparent in these layers. Finally, I hypothesized that
4 nonindigenous invasive species would dramatically decline in abundance as a result of rewatering in all four communities.
5 MATERIALS AND METHODS
Study site
The study site was located on the Big Cypress Seminole Indian
Reservation within the northeastern Big Cypress Swamp (Figure 1) . The four native forested communities chosen for study were located in the same historic drainage basin . In 1994, a 73-hectare stormwater attenuation cell impoundment (SAC) containing representative samples of each community type was constructed within part of this basin (Figure 2) . Based on examination of 1953 aerial photography, these rewatered communities appeared to be originally physionomically similar to adjacent wetlands that were drained continuously over the last century.
The primary purpose of the SAC was to receive excess water from adjacent agricultural fields during periods of high precipitation . During precipitation events, three pumps on the eastern boundary move water into the impoundment. Water drainage occurs primarily by infiltration through the soi l substrate and, secondarily, during extreme events, through an overflow structure at the southern end of the SAC. As a result, the SAC has experienced higher water levels (approximately 1 to 2 meters) and longer periods of inundation (approximately 3 months) than nearby wetlands. At the time of its construction, the impoundment contained 27 1 ha of cypress dome
6 Source: Seminole Tribe of Florida, 1998
7 !· li-:-:-. 7
Figure 2. Study sites including the SAC impoundment.
SAC boundary 600 0 600 1200 Feet
8 habitat, 9.2 ha of cypress-maple mixed forest, 1.7 ha of laurel oak hammock and 4 ha of live oak hammock. The remaining 30 hectares were comprised of pasture lands, abandoned after impoundment, that are currently dominated by grasses (i.e. Para grass, Uroch/oa mutica), and secondarily by willow trees
(Salix caroliniana). In 1999, study sites within the SAC were established within each forested community described above (Figure 1) . Reference sites within the same historic drainage basin characterized by similar canopy dominance were selected utilizing aerial photographs from 1953, 1988, and 1998 (Figures
1-4 ). Ground verification and later analysis of canopy and subcanopy similarity values reinforced the initial reference site decision.
Habitat Characterization
Within each sampled community, vegetation was characterized in the canopy, subcanopy, shrub, and herbaceous layers and seedling component.
To capture the effect of seasonal fluctuation , the shrub, herbaceous and seedling data were collected in both the wet and dry seasons (between May and December 1999) and later combined for analysis. The canopy layers were only sampled in the dry season because little change was anticipated in these strata during the one-year study period. The canopy was the tallest, dominant vegetation , while the subordinate vegetation between the canopy and shrub layer was designated as the subcanopy. The shrub layer consisted of vegetation 1 to 5 meters in height, and the herbaceous layer consisted of any
9 Figure 3. Study sites.
200 0 200 400 Feet
10 Figure 4. Study sites 300 0 300 600 Feet ~
II established vegetation up to 1m in height. The seedling component consisted of germinating seeds. Canopy trees were completely enumerated for one cypress dome and one live oak community to determine the optimal sampling technique for measuring canopy species. Several different ecological sampling techniques were subsequently tested on these two communities using randomly selected points for each technique (Table 1) .
The best sampling method among those tested for the cypress dome habitat was a 12 X 12 m quadrat. However, since 10 X 10 m quadrats gave statistically similar results with a much reduced sampling time, these were used to characterize the canopy of this habitat. Five to ten quadrats were used in each dome, depending on the size of dome. In the SAC, a total of 58 quadrats were sampled within seven domes; a total of 40 quadrats were used within four reference cypress domes outside the SAC.
The point quarter method was the most accurate canopy sampling method in the live oak hammock (Table 1) . A minimum of two randomly placed transects with a combined length of no less than 100 meters was used to sample each live oak hammock. The single live oak hammock within the SAC was sampled with two transects with a combined length of 101 m. The two reference live oak hammocks were sampled with a total of five transects with a combined length of 234 m. The laurel oak and cypress/maple mixed forested areas were not enumerated since Harms eta/. (1980) found that circular 0.04
12 Table 1. Comparison between different sampling techniques to find canopy tree density.
Communit n C* Method c ress Enumeration 100 0.078 Quadrat Sampling 10 X 10 6 10.0 0.072 Quadrat Sampling 12 X 12 6 14.0 0.074 Ordered Distance 40 0.029 Point-Quarter 39 26.3 0.121 Variable Area 7 0.019
Live Oak Enumeration 100 0.009 Point-Quarter 27 76.7 0.009 Quadrat sampling 10X10m 6 11 .8 0.020 Quadrat sampling 12X12m 6 16.9 0.019 Ordered distance 7 12.6 0.010
C*, this column denotes the percent of the total area of the habitat.
13 ha plots were an adequate sampling method to characterize similar community types. For the purpose of this study, 0.03 ha and 0.04 ha circular plots were
used in the laurel oak hammock and cypress-maple forest, respectively, based on the amount of area being characterized. Laurel oak hammock communities of the SAC and outside reference sites had a smaller area than cypress-maple communities, so a smaller quadrat area was utilized to accommodate a larger sample number to avoid sampling overlap. In the SAC, two laurel oak and one cypress-maple community were sampled while the outside reference sites
included two laurel oak hammocks and two cypress-maple forests. Within the
laurel oak hammocks and the cypress maple forests, a total of 7 and 4 circle quadrats, respectively, in each area were sampled. Adequate sampling of these communities was verified using species area curves (Figure 5) . All sampling plots and transects were located at least five meters from borders to
minimize edge effects. Species stem count and coverage were obtained for all
layers except for regenerating seedlings.
One by one meter subplots were used to measure shrub and herbaceous
layers and seedling component. These were randomly placed within the
different habitats: three within each of the 1OX1 Om canopy quadrats of the
cypress dome community, ten and twelve within each of the laurel oak and
cypress-maple mixed forest circle quadrats, respectively, and ten along
random points on each transect line in the live oak hammock. Within each
14 Figure 5. Species area curves for cypress (a.), cypress maple (b.), laurel oak (c.), and live oak (d.) SAC and reference habitats.
(a .)
80
"'Q) 70 - ·u 60 ~ Q) ~ 50 ./"' 0 40 ./ ~ 30 1-./
E::;, 20 1-- / z 10 I 0 51 101 151 201 251 301 Number of plots
Vl (c.)
60 .!!!"' 50 (,) -1 8. 40 "' 0... 30 1: 20 ~ E . ~ 10 ~ ~ I 0 11 21 31 41 51 Number of plots subplot, species stem counts were recorded for the shrub and herbaceous layers and seedling component.
Statistical Analysis
Quadrat sampling data were used to compute importance values on the canopy and subcanopy vegetative layers for each sample site as described by
Brower et a/. (1998). The importance values combine relative frequency, relative coverage, and relative density into one value for each species. Based on these importance values, matrices of similarity coefficients between study sites were generated for the canopy and subcanopy vegetation (Odum 1950,
Bray and Curtis 1957). Bray-Curtis cluster analysis of the similarity matrices was used as a measure of the relatedness of the study sites (Odum 1950,
Bray and Curtis 1957). This analysis allowed assessment of the uniformity among community types between re-watered and reference habitats and provided validation of the a priori assignment of study sites to specific community types based on aerial photography and preliminary ground surveys.
Species richness, evenness, Shannon and Simpson diversity and relative abundance measures were calculated from the sampling data using PC-ORO software (McCune and Mefford 1999). These parameters were compared using a two-sample Student t-test to determine significant differences. Global differences in species diversity, richness, evenness and relative abundance
16 between the SAC and the reference sites were determined by a t-test for all four community types. Data for each community type was also analyzed to identify trends in the community indices between rewatered and reference sites. Determination of the relative abundance of wetland and nonindigenous species between re-watered and reference sites was done by analysis of stem count data using PC-ORO software and assigning observed species to categories based on hydrological dependence (Reed 1998) and non indigenous status (FLEPPC 2001 ).
To assess hydrology during the study period , water depth measurements were taken near the inflow pumps, the outflow structure, and within each community type every two weeks when water was present. To augment these water depth measurements, water depth was also recorded by two digital wells, installed within the SAC after the vegetation sampling was completed .
17 R ESULTS
Water depth measurements within the four forested communities of the
SAC were consistent with the expected hydrological gradient. For instance, the cypress dome community had the greatest water depth (1.06 m) and hydroperiod (approximately 3 months), followed in order of decreasing depths by the cypress-maple (0 .83 m) , laurel oak (0.73 m) and live oak communities
(0.60 m) (Figure 6) . No surface water was observed in the reference habitats throughout the duration of the study. The digital well data showed higher water
levels the year after sampling and, as expected, the cypress community was the deepest (Figure 6) .
Cluster analysis of canopy and subcanopy similarity values among the four forested wetland communities within the SAC and reference sites generated groups consistent with a priori community designations and the historic
hydrological gradient (Figures 7 and 8) . Specifically, wetland and upland canopy vegetation diverged at 27.57 percent similarity, while subcanopy vegetation also separated wetlands from uplands with a low similarity value of
36 .86 percent. In contrast, the two wettest communities, cypress domes and cypress-maple forests, were most similar to each other at an average canopy similarity of 88 .65% , while the canopy of the two oak communities grouped
most closely together, with an average similarity of 75.86% (Figures 7 and 8) .
18 FtgUre 6 Water Depths of SAC F orested Commurnhe s m 1999 and 2000
1 6 .------1 4 +------1 2 +-----.,..or------+- cvpress dome, 99 ---- cypress-maple. 99 -E - ______.._ laurel oal<. 99 s 0 8 +------=,...-~:---~~~------ Q.. ----1<'---- live oak. 99 ~ 06 ...... ,=----=*-~"<--~&-----"'..------..:31~--- -a- popasr1. 00 0 4 +------'>.~~;=------>...;-->..,------"'c--- -'"v- cvpress clome, 00
0 2 +------~~~=----.~::------'V
0 +--.---.--.--.--.--.~~==T-~ Q"J 0 -..._ ~ 0l --. --. •='l 0 0
19 Similarity Canopy Similarity
27.57 -
51 .71 -
75.86 - I I 100.00 2--1 I ,-L-, r-'---1 r-C..., I I I I I I I I I I~ I r1l I I
Figures 7 and 8. Treatment and reference site compari son ac ross habitats. LEGEND: s denotes SAC and r represents reference sites. Habitats are designated by the following: C, cypress; M, cypress/maple forest; L, laurel oak hammock; and 0 , for li ve oak hammock.
Similarity Subcanopy Similarity 36.88
57.92
78.96
100.00
20 Species richness, evenness and Shannon and Simpson diversity indices calculated for each vegetative layer in the forested communities are shown in
Table 2. Index values were generally higher in the reference sites, with four significant exceptions which occurred only in the live oak canopy and in the cypress dome subcanopy and seedling component. Most of the significant differences in index values, 24 out of a total of 32 , occurred in the seedling component and herbaceous layer. Furthermore, index values were higher in the reference sites for 23 of these 24 significant differences, the single exception being the higher species richness found in the seedling component of the rewatered cypress domes. Although not significant, the shrub layer showed a similar trend , with higher index values in the reference sites compared to the rewatered sites. Average percent cover in the herbaceous and shrub layers was also higher in the reference communities, especially during the wet season, but these differences were generally not significant
(Appendix B) .
Among the four community types, most of the obligate wetland species were found within the historically wettest cypress dome habitat (Figures 9 through 13). In addition, the herbaceous layer and seedling component of the rewatered cypress domes had the greatest number of obligate wetland species (Figures 12 and 13). The canopy and subcanopy of the three relatively drier forested communities showed no difference in the number of obligate
21 Table 2. Comparison of average ecological parameters between treatment and habitat type.
Richness Evenness Shannon Simpson SAC reference SAC reference SAC reference SAC reference CANOPY Cypress dome 0.03 0.08 0.06 0.16 0.06 0.13 1.12 1.31
Cypress/ maple 2.00 2.50 0.32 0.67 0.28 0.59 0.15 0.36
Laurel oak 2.14 2.71 0.49 0.71 0.53 0.76 0.31 0.45
Live oak 2.50 2.40 0.95* 0.33 0.85 0.39 0.55* 0.19
SUBCANOPY Cypress dome 1.58* 1.47 0.27 0.28 0.25 0.23 0.15 0.14
Cypress/ maple 2.50 3.25 0.81 0.88 0.69 0.99 0.44 0.58
Laurel oak 1.75 2.00 0.23 0.58 0.32 0.48 0.23 0.30
Live oak 2.00 3.00 0.99 0.66 0.68 0.83 0.49 0.46
SHRUB Cypress dome 0.12 0.17 0.24 0.29 0.17 0.27 1.24 1.52
Cypress/ maple 1.88 2.29 0.52 0.43 0.45 0.48 0.29 0.27
Laurel oak 2.13 2.29 0.51 0.59 0.49 0.63 0.30 0.37
Live oak 1.25 2.88 0.25 0.59 0 17 0.68 0.13 0.38
HERB Cypress dome 0.29 0.54* 0.41 0.70* 0.56 1.06* 3.63 4.88*
Cypress/ maple 3.00 8.63* 0.64 0.58 0.80 1.29 0.45 0.58
Laurel oak 4.00 12.36* 0.57 0.74 0.85 1.77* 0.44 0.74*
Live oak 4.33 11 .90* 0.72 0.79 0.93 1.80* 0.49 0.73
REGENERATION Cypress dome 3.25* 2.56 0.29 0.50* 0.37 0.54* 0.19 0.31 *
Cypress/ maple 2.14 4.00 0.23 0.82* 0.23 1.09* 0.13 0.57*
Laurel oak 2.38 3.43 0.56 0.61 0.56 0.81 0.32 0.43
Live oak 6.00 4.71 0.91 0.87 1.45 1.16 0.73 0.59
* significant at P<0.05
22 Figure 9. Canopy species richness in (a) cypress, (b) cypress-maple, (c) laurel oak, and (d) live oak communities.
(a .) ..1/) 5 '2 4 a. 1/) 3 0 ..... 2 DsAc .0 E reference :I c 0 OBL FACW FAC FACU u
(b.) 5 4 3 2
0 OBL FACW FAC FACU u
(c.) 5 4 3 2
0 OBL FACW FAC FACU u
(d .) 5 4 3 2
0 OBL FACW FAC FACU u
* significant at P<0.05
23 Figure 10. Subcanopy species richness in (a) cypress, (b) cypress-maple, (c) laurel oak, and (d) live oak communities.
(a .) 5 en ·Cl>u 4 Cl> ~ 3 0 ~ Cl> 2 OsAc ~ E ::J reference c: 0 OBL FACW FAC FACU u
(b.) 5 4 3
2
0 OBL FACW FAC FACU u
(c.) 5
4 3 2
0 -.------OBL FACW FAC FACU u
(d .) 5 4 3
2
0 OBL FACW FAC FACU u
* significant at P<0.05
24 Figure 11 . Shrub species richness in (a) cypress, (b) cypress-maple, (c) laurel oak, and (d) live oak communities.
(a .) "'10 ·;:;Cl> Cl> 8 Q. 6 DsAc 0"' :;; 4 .0 reference E 2 :I c:: 0 OBL FACW FAC FACU u
(b.) 10 8 6 ----- 4 2 0 OBL FACW FAC FACU u
(c. ) 10 8 6 4 2 0 OBL FACW FAC FACU u
10 (d .) 8 6 4
2 0 OBL FACW FAC FACU u
* significant at P 25 Figure 12. Herbaceous species ri chness in (a) cypress, (b) cypress-maple, (c) laurel oak, and (d) live oak communities. (a .) 16 ~------~------ ~ 14 +-,..-.----,..-,------i;l------· ~ 12 g. 10 0 8 D sAc 0; 6 e 4 reference ~ 2 0 +-'-'-'-..-,--'-- OBL FACW FAC FACU u (b.) 16 ,------14 +------12 +------~--- 10 +-_JL______JI.______8 +------6 4 2 0 OBL FACW FAC FACU u (c.) 16 .------.------14 +------12 +------4------~- ~------10 +------~~----~~~------8 +------6 +------4 +------2 0 OBL FACW FAC FACU u (d .) 16 ------14 12 * 10 * 8 1- 6 lin 4 1111 2 Ill 0 IBt r- I ~ I = OBL FACW FAC FACU u * significant at P<0.05 26 Figure 13. Seedling layer species richness in (a) cypress, (b) cypress-maple, (c) laurel oak, and (d) live oak communities. (a .) OsAc reference OBL FACW FAC FACU u (b.) 14 .------12 +------10 +------8 6 +------~r------4 +------~~------2 +------0 +--'--'-----,-..._ OBL FACW FAC FACU u (c.) 14 ,------12 +------10 +------8 +------6 +------4 +------2 +------0 +--''---'L__~--'-- OBL FACW FAC FACU u (d .) 14 12 10 8 6 4 Bl1 I"'KI _m1 2 r---KI 0 l lfl I Ill OBL FACW FAC FACU u * significant at P<0.05 27 wetland species (Figures 9 and 10, Table 3) . The cypress-maple community, historically the second-wettest, had the same number of obligate, facultative wetland and facultative species in the canopy and subcanopy, although no facultative upland or upland species were present. The two historically drier communities also had facultative upland and upland species represented in both the canopy and subcanopy (Figures 9 and 10) . The herbaceous layer and seedling component, and to a lesser degree the shrub layer, tended to show the same pattern (Figures 11 ,12 and 13, Table 3) ; along the historic hydrological gradient, a greater proportion of facultative, facultative upland and upland species are represented in the two drier hammock communities of the reference sites, while the greatest proportion of obligate and facultative wetland species were found in the rewatered cypress dome communities. In summary, two patterns appeared when considering significant changes in composition of species' wetland classifications with rehydration (Table 3) . The rewatered historically wettest community found a general increase in obligate wetland species and a decrease in facultative species, while the three rewatered drier communities generally decreased in facultative wetland , facultative, and facultative upland species {Table 3) . Nonindigenous plant species were present throughout the strata of both the SAC and reference communities (Table 4) . Few nonindigenous species 28 Table 3. A list of significant comparisons between SAC and reference sites in terms of the changes in species wetland classification type. The results are presented as changes in SAC relative to the outside reference communities. t= decrease, i= increase, OBL= obligate wetland species, FACW= facultative wetland species, FAC= facultative species, FACU= facultative upland species. Community Cypress- Cypress Laurel Oak Live Oak maple I. -.-.-., . ,!. FAC - - - Canopy .I I I ..... Q) . >. I co Subcanopy I i OBL - - - _J . . c I I 0 - ;- - . ------""1-- ~ I I a; . ,!. FAC - ,!. FACU ,!. FAC I 0> Shrub I Q) I I > I .I I t OBL t FACW t FACW I ,!. FAC j1- fF"'Acw- ,!. FAC ,!. FAC I Herb I .I ,!. FAC t FACU t FACU I ·-·-·-· I ------ 29 Table 4. Distribution of nonindigenous plant species between the SAC and reference sites. Numbers indicate the total number of species whose highest abundance occurred at that site. Total number of non- Type I nonindigenous Type II nonindigenous indigenous species species species SAC reference SAC reference SAC reference CANOPY Cypress dome 0 2 0 2 0 0 Cypress/maple 0 0 0 0 0 0 Laurel oak 0 0 0 0 0 Live oak 0 0 0 0 SUBCANOPY Cypress dome 0 0 Cypress/maple 0 0 0 0 0 0 Laurel oak 0 0 0 0 Live oak 0 0 0 0 0 0 SHRUB Cypress dome 2 2 0 0 Cypress/maple 2 2 0 0 Laurel oak 0 0 0 0 Live oak 0 0 0 0 0 0 HERB Cypress dome 4 2 3 0 0 Cypress/maple 2 0 2 0 0 Laurel oak 0 0 Live oak 0 4 0 0 2 SEEDLING Cypress dome 3 0 0 Cypress/maple 2 0 0 0 Laurel oak 0 0 Live oak 0 0 30 were found in upland communities other than the herbaceous layer of the reference live oak hammocks (Table 4) . The same number of nonindigenous species were found in the herbaceous layer of the rewatered and reference cypress domes. However, the rewatered cypress domes contained mostly Category I invasive species, whereas the reference live oak hammock contained only one Category I and two Category II invasive species. In the seedling component, the concentration of nonindigenous species was greatest in the wetland communities of the SAC, whereas the upland communities showed little difference in nonindigenous species composition. 31 DISCUSSION To achieve the ecological goals and objectives of the Comprehensive Everglades Restoration Plan, it has been determined that the remaining natural system should be changed in the direction of its pre-drainage wetland character through modifications of the hydrologic features. Specifically, the Central and Southern Florida Project Comprehensive Review Study ( 1999) stated that the "recommended Comprehensive Plan achieves the restoration of more natural flows of water, including sheetflow, improved water quality, and more natural hydroperiods in the south Florida ecosystem. Improvements to native flora and fauna , including threatened and endangered species, will occur as a result of the restoration of hydrologic conditions." Therefore, understanding the impact of rewatering desiccated native habitats is of primary importance to the success of the restoration effort. Within the Everglades Big Cypress Swamp, natural communities have experienced drier conditions over the last half-century as a result of regional drainage. Vegetation composition was compared within four forest communities that had been diked and rewatered for five years to representative drier habitats outside the impounded area. The communities ranged across a historic hydrological gradient from hydric to mesic, largely as 32 a result of slight differences in elevation. The enhancement in hydroperiod was not for the purpose of restoration, but to detain stormwater pumped from agricultural fields. I hypothesized that along this hydrological gradient, a shift in species composition and diversity in the seedling, herbaceous and shrub layers would occur with hydration. Specifically, obligate wetland species would dominate these layers in the two hydrated cypress communities and diversity would decrease as a result of a decrease in facultative wetland and upland plant species. In the two oak communities, facultative wetland species would increase in richness and abundance in these three layers, but diversity would still be less than the non-rewatered reference communities. The comparisons between the rewatered SAC and reference sites generally supported this hypothesis for the seedling component and herbaceous layer within the cypress dome but not the other three communities (Figures 9 - 13, Tables 2 and 3) . For instance, despite the increase in obligate wetland species abundance, the re-watered cypress had an overall decrease in plant diversity because of the large reduction in more facultative plant species. The response to rewatering in the shrub layer tended to support my hypothesis, but obligate and facultative wetland species were less represented in this layer compared to the two lower layers. This muted response in the shrub layer is consistent with Kirkman eta/. (2000) in that deep inundation, in the absence of 33 sufficiently shallow and appropriately timed periods of drawdown, may not allow regenerating species to attain an adequate height for survival. The hydrology of the SAC consisted of relatively short inundation periods and deep water depth from year to year. This would potentially facilitate obligate wetland species within the seedling component but would also potentially reduce their regeneration into the herbaceous layer (Kirkman et a/. 2000). In contrast, in the reference sites, which were not inundated, herbaceous cover was higher, persistent throughout the year, which may have contributed to the reduced seedling count (Marks 197 4, Gilliam et a/. 1995, Fredericksen et a/. 1999). Jordan et a/. ( 1997) found a similar pattern in the Everglades marsh communities, where herbaceous wetland species were inversely correlated to water depth. They found that the deepest slough areas had a more sparse herbaceous understory that increased in structure and complexity as the community became less inundated. As my second hypothesis, I proposed that there would be no significant difference in diversity in the canopy layer between rewatered and desiccated sites. This layer typically shows a longer term response to chronic abiotic changes (Spurr and Barnes 1980). In my study, when examined by individual community types, this hypothesis was generally supported in both canopy layers. In particular, it was noted that there were substantially fewer facultative wetland laurel oak (Quercus laurifolia) canopy trees in cypress and 34 cypress-maple communities within the rewatered SAC. It appeared that rewatered laurel oak trees became susceptible to root rot by Ganoderma Jucidum fungus under inundated conditions, eventually resulting in their death. However, further studies will need to be conducted to substantiate this observation. Kirkman et a/. (2000) also found that flood intolerant hardwood species declined as a result of an increase in water depth and hydrology. In my study, the live oak hammock, which historically was the driest community among the four, displayed a significantly greater canopy diversity in the reference sites because it had greater evenness of facultative and facultative wetland species such as red maple (Acer rubrum) and laurel oak, respectively. In other studies, mesic species have increased in upland areas because of a lack of fire (Vena 1976, Cowell 1998). However, none of my research sites have evidence of recent fire. Moreover, Duever et. a/. (1984) found that the lack of fire has never played a large role in the establishment of small pockets of oak hammock in the Big Cypress Swamp. Because these species exhibit individual distributions along a hydrological gradient, it is more likely that in my study these faster growing species have increased in abundance in the upland sites as a result of regional desiccation. For instance, the drier conditions which have prevailed over the last 50 years have likely resulted in a substantial increase in red maple and laurel oak trees in historically hydric cypress communities and a general increase across the 35 entire landscape (Alexander and Crook 1984 ). With rewatering , it is likely that the spatial extent of the niche occupied by these species will narrow in the most hydric sites, while expanding in the upland sites where rewatering has provided appropriate growing conditions. Although for laurel oak, it was noted that rehydration in more upland areas resulted in a possible truncation of its roots which may have made them more susceptible to mortality during drought periods. Further monitoring of the long-term response of these species to rehydration will be necessary substantiate these findings. My third hypothesis was that rewatering would significantly reduce nonindigenous species abundance in all four communities. It has often been shown that extended periods of deep inundation preclude successful establishment of native seedlings (Demaree 1932, DuBarry 1963) and I expected nonindigenous species to show a similar response, even though nonindigenous species have a wide range of tolerances to ecological pressures (Baker 1974, Gordon and Thomas 1997, and Mack et. al. 2000). Although invasive nonindigenous canopy species were more abundant in the reference sites compared to the rewatered sites, this hypothesis was generally not supported. Category I invasive species were present in both the rewatered and reference sites. There was a general tendency for more hydric invasive species to be present on the rewatered sites, and more mesic species to be on the reference sites. Interestingly, regeneration of Brazilian pepper, a 36 facultative wetland species, was killed with rewatering but was survived by plants found in the shrub and subcanopy/canopy layers. Longer-term studies will be required to more fully elucidate the impact of hydrological restoration on nonindigenous species. 37 CONCLUSIONS Re-establishing more natural flows of water within the Everglades Big Cypress Swamp will greatly affect the landscape community structure and composition (Gunderson 1994). Hydrological changes impact wetland species composition such that species assemblages will reflect the changed hydrology in both the short- and long-term (Wicker et a/. 1981 , Davidson and Forman 1982, Pearlstine et a/ 1985). This study supports this paradigm; rewatering generally resulted in a shift in species composition along a hydrological gradient, such that wetter areas became relatively more dominated by obligate and facultative wetland species and drier sites had a greater presence of facultative and facultative upland species. This association was particularly evident in the shorter-term response that was observed in the seedling component and herbaceous layer. Historically within the Big Cypress Swamp, cypress communities were the most dominant (Duever et. a/. 1979). Because cypress trees are obligate wetland canopy species that can , once established, grow under drier conditions (Mitsch and Ewel 1979), their competitive advantage in wet conditions over more facultative species resulted in their widespread historical dominance (Demaree 1932, Young et. al. 1995). Although cypress continues to dominate throughout the landscape, the diminished hydrology of the 38 southern Florida region has led to an increase in coverage by facultative wetland species. This study suggests that rewatering may reduce or, in some cases, reverse this trend and lend to a more historic plant distribution. 39 Appendix A Nonmd1genous spec1es w1th the highest abundance m torested wetland commun1t1es. Wetland ca tegory IS noted (OBL-obl1 gate wetland, FACW-fa cultative wetland. FAG-facultati ve FACU-facultative upland, U-upland)(Reed 1988) Total number of non-1nd1genous spec1es Category I non-Indigenous Category II non-indigenous ANA reference CANOPY Cypress dome none Ps1d1um guajava Schmus terebinthifofius Cypress-maple forest none none Laurel oak hammock C1 trus sp none Lrve oak hammock none Melaleuca qumquenervta SUBCANOPY Cypress dome Schmus terebmthifollus Pstdium guajava Cypress-maple forest none none Laurel oak hammock Schinus terebinthifollus none L1ve oak hammock none none SHRUB Cypress dome Schmus terebmthtfOIIUS Lygodwm m'crophylfum Psidi11m guajava Cypress-maple forest Pstdwm gua,ava Lygodium mtcrophyffum Schmus terebinthifoltus Psidium guajava Passi11ora foettda Schinus terebinthifolius Urena lobata Laurel oak hammock Schmus terebmthifollus none Melaleuca quinquenervia Lygodium microphyllum L1ve oak hammock none none HERB Cypress dome Pamcum repens Urena lobata Schinus terebmthifolws Ludwigia peruviana Pist1a stralloites Amaranthus viritidis Cypress-maple forest Paspalum notatum Lygod1um mtcrophyllum Schinus terebinthifolius Laurel oak hammock Schmus terebmthtfol,us Urena lobata L1ve oak hammock none Passiflora foetida Urena lobata Paspalum notatum Pamcum repens SEEDLING Cypress dome Citrus sp Urena fobata Schmus terebinthtfollus L udw1g1a peruviana Cypress/maple Urena lobata none Schmus terebmthlfollus Laurel oak Urena lobata Schtnus terebmthlfollus L1ve oak Schmus terebmthtfoltus Urena lobata 40 Appendix B Average vegetation coverage per m2 between vegetative layers. SAC reference p Cypress dome canopy 0.3 0.4 0.04 subcanopy 0.3 0.2 0.24 shrub 18.3 16.2 0.37 herb 21 .2 27.9 0.30 Cypress-maple forest canopy 0.1 0.1 subcanopy 0.0 0.1 shrub 30 .8 5.9 0.00 herb 6.8 19.4 0.21 Laurel oak hammock canopy 0.2 0.1 0.64 subcanopy 0.0 0.0 0.61 shrub 17.1 19.4 0.75 herb 11 .3 35 .1 0.01 Live oak hammock canopy 51 .1 50 .8 0.98 subcanopy 1.5 3.7 0.37 shrub 23.6 20.6 0.81 herb 25 .9 55.4 0.01 41 APPENDIX C Species List Binomial e~ithet Common Name Family Wetland Source {a) ~ Category Acerrubrum red maple Aceraceae FAC Reed N 2 Amaranthus viridis slender amaranth Amaranthaceae FACW Austin Nl 3 Ambrosia artemisiifo/ia ragweed Asteraceae FACU Reed N 4 Ampelopsis arborea peppervine Vitaceae FAC Reed N 5 Annona glabra pond apple Annonaceae OBL Reed N 6 Ardisia escallonioides downy rosemyrtle Myrsinaceae FAC Tobe et.al. N 7 Aristida stricta threeawn Poaceae FAC Reed N 8 Aster dumosus bushy aster Asteraceae FAC Reed N 9 Baccharis glomeruliflora saltbush Asteraceae FACW Reed N 10 Bacopa caroliniana lemon bacopa Scrophulariaceae OBL Reed N 11 Bacopa monneri herb-of-grace Scrophulariaceae OBL Reed N 12 Berchemia scandens rattan vine Rhamnaceae FACW Reed N 13 Bidens alba Spanish needles Asteraceae FAC Tobe et.al. N 14 Blechnum serrulatum swamp fern Blechnaceae FACW Reed N 15 Boehmeria cylindrica bog hemp Urticaceae FACW Reed N 16 Bursera simoruba gumbo limbo Burseraceae u Austin N 17 Calicarpa americana beautyberry Verbenaceae FACU Reed N 18 Campyloneurum phillitidis strap fern Polypodiaceae EPIPHYT N 19 Carex gigantea giant sedge Cyperaceae OBL Reed N 20 Celtis laevigata hackberry Ulmaceae FACW Reed N 21 Centella asiatica spadeleaf Apiaceae FACW Reed N 22 Cephalanthus occidentalis buttonbush Rubiaceae OBL Reed N 23 Chiococca alba snow berry Rubiaceae FAC Tobe et.al. N 24 Cirsium horridulum Nuttall's thistle Asteraceae FAC Reed N 25 Citrus sp. Rutaceae FACU Reed Nl 26 Cladium jamaicensis sawgrass Cyperaceae OBL Reed N 27 Commelina diffusa dayflower Commelinaceae FACW Reed N 28 Conyza canadensis Canadian horseweed Asteraceae FACU Reed N 29 Crinum americanum string-lily Amaryllidaceae OBL Reed N 30 Dichanthelium cypress witchgrass Poaceae FAC Reed N dichotomum 31 Diospyros virginiana common persimmon Ebenaceae FAC Reed N 32 Eclipta alba false daisy Asteraceae FACW Reed N (a) (Reed 1988, Tobe et al1998, Austin personal communication) (b) N - Native, Nl - non-indigenous, 1- Type I invasive (EPPC 2001 ), II - Type II invasive (EPPC 2001 ) 42 Binomial e~ithet Common Name Family Wetland Source (a} !.!ll Category 33 Eleocharis sp. spikerush Cyperaceae OBL Reed N 34 Erechtites hieracifolia American burnweed Asteraceae FAC Reed N 35 Erigeron quercifolius oakleaf fleabane Asteraceae FAC Reed N 36 Eryngium yuccifolium button Apiaceae FAC Reed N rattlesnakemaster 37 Erythrina herbacea coral bean Fabaceae u Austin N 38 Eupatorium capi/lifolium dog fennel Asteraceae FACU Reed N 39 Ficus sp. Moraceae FAC Tobe et.al. N 40 Fraxinus caroliniana pop ash Oleaceae OBL Reed N 41 Galium tinctorium stiff marsh bedstraw Rubiaceae FACW Reed N 42 Habenaria floribunda toothpetal false Orchidaceae FACW Reed N rein orchid 43 Hydrocotyle umbellata musky mint Lamiaceae OBL Reed N 44 Hyptis alata dollar weed Apiaceae OBL Reed N 45 /lex cassine Florida holly Aquifoliaceae FACW Reed N 46 Ipomoea alba moon vine Convolvulaceae FAC Reed N 47 Ipomoea saggitata saltmarsh Convolvulaceae FACW Reed N morningglory 48 lresine diffusa Juba's bush Amaranthaceae FAC Reed N 49 Lemna obscura little duckweed Lemnaceae OBL Reed N 50 Liatris sp. gayfeather Asteraceae u Austin N 51 Lindernia grandiflora savannah false Scrophulariaceae OBL Reed N pimpernel 52 Ludwigia peruviana Peruvian Onagraceae OBL Reed Nl primrosewillow 53 Ludwigia repens creeping Onagraceae OBL Reed N primrosewillow 54 Lycopus sp. waterhorehound Lamiaceae OBL Reed N 55 Lygodium microphyllum Japanese climbing Schizaeaceae FACW Austin fern 56 Lyonia ferruginea rusty lyonia Ericacea FAC Reed N 57 Mecardonia acuminata axilflower Scrophulariaceae FACW Reed N 58 Melaleuca punk tree Myrtaceae FAC Reed I quinquenervia 59 Melothria pendula creeping cucumber Cucurbitaceae FACW Reed N 60 Mikania scandens white vine Asteraceae FACW Reed N 61 Morus rubra mulberry Moraceae FAC Reed N 62 Myrcianthes fragrans twin berry Myrtaceae u Austin N 63 Myrica cerifera wax myrtle Myricaceae FAC Reed N 64 Myrsine guianensis myrsine Myrsinaceae FAC Reed N 65 Nephroleptis exaltata Boston fern Nephrolepidacea FACU Reed N e 66 Osmunda regalis royal fern Osmundaceae OBL Reed N (a) (Reed 1988, Tobe et al1998, Austin personal communication) (b) N - Native, Nl - non-indigenous, I- Type I invasive (EPPC 2001 ), II - Type II invasive (EPPC 2001) 43 Binomial e~ithet Common Name Family Wetland Source {a} fill Category 67 Oxalis corniculata common yellow Oxalidaceae FACU Reed N wood sorrel 68 Panicum hemitomon maiden cane Poaceae OBL Reed N 69 Panicum repens torpedo grass Poaceae FACW Reed 70 Parietaria floridana Florida pellitory Urticaceae FAC Reed N 71 Parthenocissus Virginia creeper Vitaceae FAC Reed N quinquefolia 72 Paspalum notatum Bahiagrass Poaceae FACU Reed Nl 73 Passiflora foetida fetid passionflower Passifloracea u Austin II 74 Persea borbonia swamp bay Lauraceae FACW Reed N 75 Phlebodium aureum golden polypody Polypodiaceae EPIPHYT N 76 Phyla nodiflora creeping charlie Verbenaceae FACW Reed N 77 Phytolacca americana pokeberry Phytolaccaceae FACW Austin N 78 Pinus elliottii slash pine Pinaceae FACW Reed N 79 Pistia stratiotes water lettuce Araceae OBL Reed 80 P/uchea rosea camphor weed Asteraceae FACW Reed N 81 Polygonum punctatum dotted smartweed Polygonaceae FACW Reed N 82 Polypodium resurrection fern Polypodiaceae EPIPHYT N polypodioides 83 Pontederia cordata pickeral weed Pontederiaceae OBL Reed N 84 Proserpinica pectinata combleaf Haloragaceae OBL Reed N mermaidweed 85 Psidium guajava guava Myrtaceae FACU Reed 86 Psilotum nudum whisk fern Psilotaceae FACU Reed N 87 Psychotria nervosa wild coffee Rubiaceae FAC Tobe et.al. N 88 Psychotria sulzneri shortleaf wild coffee Rubiaceae FAC Tobe et.al. N 89 Pteridium aquilinum bracken fern Dennstaedtiacea FACU Reed N e 90 Ptilimnium capillaceum mock bishopseed Apiaceae OBL Reed N 91 Quercus laurifolia laurel oak Fagaceae FACW Reed N 92 Quercus virginiana live oak Fagaceae FACU Reed N 93 Randia acu/eata white indigoberry Rubiaceae u Austin N 94 Rhus copallinum winged sumac Anacardiaceae u Austin N 95 Rivinia humilis rougeplant Phytolaccaceae u Austin N 96 Rubus trivia/is blackberry Rosaceae FAC Reed N 97 Rhynchospora plumosa plumed beaksedge Cyperaceae FACW Reed N 98 Saba/ palmetto sabal palm Pal mae FAC Reed N 99 Sagittaria lancifolia bulltongue Alismataceae OBL Reed N Arrowhead 100 Salix caro/iniana swamp willow Salicaceae OBL Reed N 101 Salvinia minima water spangles Marsileaceae OBL Reed N 102 Sarcostemma clausum milk-weed vine Asclepiadaceae FACW Reed N 103 Saururus cernuus lizard's tail Saururaceae OBL Reed N 104 Schinus terebinthifolius Brazilian pepper Anacardiaceae FAC Reed (a) (Reed 1988, Tobe et a/1998, Austin personal communication) (b) N - Native, Nl - non-indigenous, 1- Type I invasive (EPPC 2001), II - Type II invasive (EPPC 2001 ) 44 Binomial e~ithet Common Name Family Wetland Source {a} .{!ll Category 105 Scleria sp. nutrush Cyperaceae FACW Tobe et.al. N 106 Senecio glabellus butterweed Asteraceae FACW Reed N 107 Serenoa repens saw palmetto Pal mae FACU Reed N 108 Sideroxylon salicifolium willow bustic Sapotaceae u Austin N 109 Smilax spp. greenbriar Smilacaceae SPP. Reed N 110 Solanum americanum American black Solanaceae FACU Reed N nightshade 111 Solanum capsicoides soda apple Solanaceae u Austin N 112 Solidago sp. goldenrod Asteraceae FACW Austin N 113 Sonchus spp. Asteraceae FACW Austin N 114 Taxodium distichum cypress Taxodiaceae OBL Reed N 115 Thalia geniculata alligator flag Marantaceae OBL Reed N 116 Thelypteris interrupta hottentut fern Thelypteridaceae FAC Reed N 117 Thelypteris kunthii widespread maiden Thelypteridaceae FACW Reed N fern 118 Tillandsia spp. air plant Bromeliaceae N/R Reed N 119 Toxicodendron radicans poison ivy Anacardiaceae FAC Reed N 120 Urena lobata Caesar's weed Malvaceae FACU Reed II 121 Vaccinium corymbosum Sparkleberry Ericaeae FACW Reed N 122 Vicia acutifolia four-leaf vetch Fabaceae FACW Reed N 123 Vitis rotundifolia muscadine grape Vitaceae FAC Reed N 124 Vitis shuttleworthii calloose grape Vitaceae FAC Reed N 125 Vittaria lineata shoe string fern Vittariaceae FAC Reed N 126 Woodwardia virginica chain fern Blechnaceae OBL Reed N 127 Ximenia americana tallow wood Olacaceae FACU Reed N 128 Zanthophylum fagara wild lime Rutaceae u Austin N (a) (Reed 1988, Tobe et al1998, Austin personal communication) (b) N- Native, Nl - non-indigenous, 1- Type I invasive (EPPC 2001), II- Type II invasive (EPPC 2001) 45 LITERATURE CITED Alexander T R, Crook A G. 1984. 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