Although wetland restoration has been a key part of U.S. environmental policy for 20 years (i.e., “no net loss”), there is little long-term data on restorations to guide planning and assessment. Understanding how restored wetland communities deviate from natural conditions, and how long those deviations persist, can provide important insights into the mechanisms of recovery and improve restoration practice. This study reports the results from a 19-year survey of 37 restored prairie pothole wetlands in northern Iowa, southern Minnesota, and southeastern South Dakota. Complete floristic surveys were performed for each of the wetlands in 1989, 1990, 1991, 2000, and 2007. The accumulation of wetland species across all sites was greatest during the first 12 years after reflooding (14.4 species/year), after which the rate declined to 1.6 species/year. Proximity to natural wetlands and a semi-permanent water regime favored species accumulations during the first 12 years, but changes since then are primarily linked to water regime. Semi-permanent wetlands have experienced fewer major gains and losses in species richness, whereas temporary and seasonal wetlands have been less stable. From 2000 to 2007, extinctions exceeded colonizations in all wetlands, resulting in a convergence of beta diversity. Although 77% of the species considered common to natural wetlands in the region established in these restorations, 70% of those considered infrequent have not. The likelihood that these restorations will eventually support many additional species appears low, given the presence of barriers to recovery, especially the dominance of invasive perennials (e.g., Phalaris arundinacea and Typha angustifolia/x glauca) on all sites and the low colonization efficiency of wet prairie, sedge meadow, and woody perennial species. Management, such as active revegetation of these low efficiency species guilds, particularly sedge meadow and wet prairie perennials, and invasive species control is needed to ensure that restored prairie wetlands support the region's biodiversity. The important barriers to the recovery of prairie pothole restoration: isolation, infrequent flooding, and invasive species, are all factors that do not self-correct over time and need to be addressed during planning by establishing sound practices for initial implementation and long-term vegetation management.

Russian olive (Elaeagnus angustifolia L.) is an invasive non-native tree in western North America capable of nitrogen fixation through symbiotic actinorhizal associations. The high abundance of the tree may have important effects on ecosystem nutrient dynamics and consequent community responses. This study explored the influence of Russian olive on soil nitrogen along a section of the Rio Grande River riparian zone in Rio Grande Valley State Park, Albuquerque, New Mexico. Cottonwood trees (Populus deltoides, var. wislizenii) without subcanopy trees were paired with cottonwood having a Russian olive under the canopy, and soil nitrogen pools were assessed. Relative to open interplant areas, soils under subcanopy Russian olive showed a 55% increase in total nitrogen and nearly four times the amount of available nitrogen compared to soils under cottonwood alone. Organic matter accumulation followed a similar pattern relative to open areas with 73% more accumulation under subcanopy Russian olive compared with cottonwood trees alone. Acetylene reduction and δ¹⁵N revealed that nitrogen fixation occurred in Russian olive at the site during the time of sampling, and foliar chemistry averaged 2.58% nitrogen for Russian olive compared to 0.54% for cottonwood. Both soil texture and Russian olive presence proved to be important factors affecting the observed soil nitrogen patterns. Despite these nitrogen inputs, cottonwood trees appeared to utilize sources other than that derived from Russian olive. A soil respiration experiment assessed the influence of Russian olive on soil microbial productivity, which revealed that soils at this location are carbon limited and not nitrogen limited. Even after imposing a nitrogen limitation through the addition of carbon, Russian olive did not affect microbial productivity despite higher nitrogen levels in soils associated with it. The results of this study show that Russian olive enhances soil nitrogen resources in this semi-arid riparian environment, but the added nitrogen is not likely to facilitate cottonwood tree growth or further exotic weed invasion. Russian olive may instead compete with cottonwood for other resources.

The series of reservoirs located in the upper Paraná River and its tributaries retain a large amount of phosphorus (sedimentation), impoverishing downstream waters. Although these nutrients are limiting for primary production, their role on the growth of native aquatic plants is still unknown. The free-floating macrophyte, Eichhornia crassipes, is among the most successful colonizers and fastest-growing macrophytes in the Neotropics. However, in the upper Paraná River floodplain, this plant rarely develops extensive coverage and it is even absent from some environments. We hypothesize that phosphorus concentration is limiting the growth of E. crassipes in certain aquatic habitats of this floodplain, and to test this hypothesis we designed a field mesocosm experiment using nutrient amendments. Twelve closed mesocosms (1,500 L) plus three open units (with ambient lagoon water) were set up in the Garças lagoon, under five nutrient treatments (three replicates each): L (“lagoon”, no addition), C (control, no addition), N (nitrogen addition), P (phosphorus addition), and NP (nitrogen and phosphorus addition). After nutrient amendments, introduced plants were weighed weekly for fresh biomass over a three-week period. Plants in the P and NP treatments had the most rapid increase in biomass (rmANOVA, F_12,30  =  7.54, p < 0.05) and the greatest development of sprouts (F_12,30  =  3.25, p < 0.05). In addition, phosphorus content in plant tissues was highest in P and NP treatments, while nitrogen content was similar in L, N, and NP treatments. Our results suggest that the growth of water hyacinth in the upper Paraná River floodplain is limited by phosphorus, not nitrogen. Phosphorus removal in upstream reservoirs may limit E. crassipes populations downstream, although more study is required to establish this link.

We used oligotrophic, P-limited herbaceous wetlands of northern Belize to assess how changes in nutrient availability impact species composition and ecosystem processes. The P, N, and NP enrichment plots were established in replicated marshes of three salinity levels to document potential salinity constraints. Addition of P or combination of N and P resulted in rapid switch from a microphyte (cyanobacterial mats, CBM) to macrophyte (Eleocharis spp., Typha domingensis) domination, while N addition did not have any impact. The switch was caused by significant changes in Eleocharis stem density and height, and consequently, the aboveground biomass, which increased from an average 120 g m⁻² in control and N plots to > 500 g m⁻² in P and NP plots. Decreased light under the dense canopy of Eleocharis in P and NP plots caused significant reduction in CBM growth. Biomass of Eleocharis in P and NP plots decreased with increasing salinity, but salinity did not affect biomass production in control and N plots. Tissue P of Eleocharis from P and NP plots increased 4- to 5-fold compared to P content in plants from control and N plots. Tissue P remained high due to internal nutrient recycling even after P addition ceased. Typha transplanted into plots grew exponentially in P and NP plots, while in control and N plots it grew slowly or did not survive. There were significant differences in NH₄-N both in soil extracts and in the interstitial water with soil and water NH₄-N being significantly lower in P-addition plots. The elimination of N₂-fixing CBM is a potential reason for a decrease in available sediment N as documented by a negative correlation between CBM cover and interstitial NH₄-N.

Biogenic methane (CH₄) from wetlands plays a crucial role in the carbon cycle, but the dynamics of dissolved methane flux across the surface water-ground water interface remain poorly understood. This study focused on the effects of spatial transformation of dissolved methane and the role of ground-water recharge in the distribution of dissolved methane across the surface water-ground water interface. Here we present carbon isotopic measurements of biogenic methane and dissolved inorganic carbon (DIC) from the Sarita Wetland, on the St. Paul Campus of the University of Minnesota, and also in six monitoring wells located down gradient from the wetland. The δ¹³C values of CH₄ vary between −10.6 and −58.4‰, and the δ¹³C values of DIC vary between 0.8 and −14.1‰ across the study site. Based on dissolved methane concentrations during the growing season, we estimate that ground water methane represents 8%–38% of total methane dissolved in the wetland. Using the carbon isotopic composition of methane and knowledge of the site hydrology, we found that the degree of methane oxidation increased as methane moved away from the wetland along the ground water flowpath. The proportion of methane oxidized ranged between 4% and 99% with most of the methane oxidation occurring within the first 120 m from the wetland. The degree of oxidation within the wetland itself varied from 81% in the spring to 99% during the winter, suggesting that oxidation of dissolved methane occurs more rapidly in surface waters than in ground water recharge. This study shows that ground water flow paths are a primary control on the export of dissolved methane produced in wetlands. This study also demonstrates that C stable isotopes can be used to study transport of dissolved methane across the surface water-ground water interface, accounting for methane oxidation during transport.

Changes in wetland ecosystems may result from the interactions of endogenous processes with exogenous factors such as environmental fluctuations and anthropogenic influences. Since mid-2004, the Río Cruces wetland, a Ramsar site located in southern Chile (40°S), exhibited a sudden increase in mortality and emigration of the largest breeding population of Black-necked swans in the Neotropics, a massive demise of the dominant macrophyte Egeria densa (the main food of swans and several aquatic birds), and a seasonal appearance of turbid waters. We compared annual variation in rainfall, river flow, and radiation over the period 2000–2005 to assess the role of environmental factors on these wetland changes. Those factors, with the exception of a decrease in river flow during 2004, did not show significant inter-annual differences. However, when comparing Landsat images, we found in the visible and near-infrared spectrum, a corresponding increase and decrease in water reflectance for 2005 with respect to 2003 and 2001, respectively. These results may reflect the appearance of turbid waters and the decrease in cover of E. densa. All temporal changes were restricted to the northern and central zones of the wetland. In addition, spatial analysis showed a gradient in turbidity across the wetland waters, which was enhanced by estuarine influence during spring-tides. Censuses of aquatic birds (1999–2005) showed that only herbivorous birds exhibited a pronounced decrease in population abundance after mid-2004, while piscivorous birds continued normal cycling, with even some positive trends in abundance during 2004–2005. Population declines in herbivorous birds may be related to the demise of E. densa and suspension of sediments during periods of reduced river flow (2004) that gave rise to the turbidity in the wetland waters. Environmental changes could be related to changes in water quality after a new pulp mill, built upstream of the wetland, initiated operations during February 2004.

Mediterranean vernal pools are threatened habitats that support a number of endangered/rare plant and invertebrate species. Conservation management of these important habitats is limited by a lack of knowledge, especially concerning their past and present ecological dynamics. A multidisciplinary palaeoecological investigation was conducted on one of the last alkaline vernal pools of the Rhone delta (southern France). Results highlighted the value of a multidisciplinary approach based on several complementary methods, and provide direction for subsequent palaeoecological studies in temporary wetlands. Despite some degradation, fossil assemblages provide an accurate reconstruction of the past ecological dynamics of the vernal pool studied. The pool originated c. 1100 years ago from the infilling of an abandoned palaeochannel and its subsequent fragmentation. It may thus be considered as a legacy of past natural fluvial activity, which ended with the complete channelization and confinement of the River Rhone in 1869 AD. With natural processes disrupted, new pools may need to be artificially constructed in order to preserve the biological communities of alkaline vernal pools of the Rhone delta.

We surveyed fish assemblages from Blackwater River drainage (Cambridge, Maryland, USA) to assess spatiotemporal patterns of fish distribution in response to salinity intrusion of freshwater wetlands. Three sites spaced along a longitudinal stream gradient were sampled from each of the Little Blackwater River and Blackwater River from December 2005 to December 2006. Salinity in upstream areas of Blackwater River ranged from 9–12 psu, while in the Little Blackwater River salinity ranged from 0–5 psu. Most of the spatial differences in assemblage structure occurred between upstream sites of Blackwater River, an area influenced by saltwater intrusion from the combined effects of sea level rise and a man-made canal, and upstream sites of Little Blackwater River. Freshwater-dependent fishes (e.g., brown bullhead and black crappie) dominated upstream sites of Little Blackwater River, whereas euryhaline species (e.g., killifish and silversides) dominated upstream sites of Blackwater River. We used the Little Blackwater River as a reference system to test the hypothesis that remnant freshwater-dependent fish populations of transitional areas in the Blackwater River may have declined as salinity levels increased. Upstream habitats of Blackwater River were brackish, while such habitats of Little Blackwater River were more persistently freshwater. As salinity increased seasonally in the Little Blackwater River, the abundance of freshwater-dependent fishes declined at two sites. Differences in species diversity and composition between Blackwater River and Little Blackwater River are likely associated with higher salinity and connectivity in upstream portions of the Blackwater River.

Substantial industrial development, agricultural intensification, and an increasing human population have led to the demise of many seminatural habitats, such as wet meadows, in many countries of Europe. This process can cause the extinction and decline of associated insect species. The present paper is the first study analyzing wild bee diversity and abundance patterns in wet meadows. We surveyed bees using pan traps, transect walks, and nest traps in four Molinietum (Poaceae) meadows near Kraków, Poland. During one season, we identified a relatively high γ-diversity of wild bees, consisting of 105 species (13 from the Polish Red List) belonging to 22 genera, which represent almost one-fourth of the Polish bees. The wild bee fauna between sites was not variable, which was indicated by low β-diversity. We found that nesting preference of bees did not differ between the study area and xerothermic meadows, which suggests that differentiation in bee fauna of wet and dry grasslands is mostly due to food specialization rather than nesting preference. Abundance analysis of the bee community showed that the least abundant species were disproportionately comprised of oligolectic species, indicating that species closely associated to plants of wet meadows are especially threatened. Moreover, using occurrence data we found that 34% of the species belonging to the families Halictidae, Melittidae, and the tribe Nomadini found in wet meadows are considered rare in Poland. Our results highlight an urgent need to perform further investigations and develop specific protection plans for bees not only in Kraków's Molinietum meadows, but also in wetlands throughout Europe.

The use of treated wastewater to restore freshwater inputs to arid and semi-arid wetlands is a relatively new concept, and the long-term effects of such practices on plant community structure are largely unknown. We compared vegetation composition, pore water salinity, and soil moisture along permanent transects at a restoration site receiving wastewater effluent since October 1998 to three nearby downstream sites subjected only to freshwater inputs via precipitation and river flooding. Local climate during this period was highly variable and included two droughts and a wet period that began with a series of large floods. Significantly lower pore water salinities were observed at the wastewater site compared to downstream sites, particularly during droughts, when salinities were 20‰–40‰ lower at the wastewater site. Between July 1997 and July 2002, cover of the clonal stress-tolerator, Salicornia virginica, decreased from 87% to 33% at the wastewater site, while cover of the clonal dominant, Borrichia frutescens, increased from 5% to 55%. In contrast, S. virginica cover increased at two downstream sites during the same period, while cover of B. frutescens remained relatively stable. Following large floods in summer 2002, which marked the beginning of a three year-wet period, B. frutescens cover increased at all sites. We concluded that constant wastewater additions and climate-driven wet periods affected plant community structure similarly by promoting expansion of the clonal dominant B. frutescens and inhibiting expansion of the stress-tolerant species S. virginica. We propose distinct management strategies for using wastewater to 1) increase plant cover, 2) promote endemic plant assemblages, and 3) maximize species richness.

As degradation of wetlands continues to occur as a result of human activities, it is important to identify aquatic and amphibious species' extinction risks and the relative hospitalities of sites to support intact biotic communities; one such technique involves comparing the nestedness of assemblages as an assay of predictability and stability. We measured the degree of nestedness of odonate communities (Odonata: dragonflies and damselflies) in the playa wetland complex of the Texas panhandle (data from 23 species in 73 playas in the summers of 2003–05) under current conditions as well as four simulations of future socioeconomic and climate change. Compared to randomized (null model) assemblages, significant nestedness was found for the system as a whole as well as for each year separately and for playas within each of the two dominant regional forms of land cover (cropland and grassland). Cropland and grassland playas were further split into three size categories, based on natural size breaks. Although departures from nestedness (idiosyncrasy) were unrelated to playa size or surrounding land use, larger playas surrounded by cropland displayed lower nestedness than did smaller ones whereas grassland playas showed the opposite pattern. This relationship between playa area and surrounding land-use type showed that there is lower stability in odonate community composition in even large playas if those playas are surrounded by agriculture. Departures from nestedness mainly consisted of unexpected species presences rather than absences, with idiosyncratic species being larger in total body length and including two range extensions. Under simulations of playa losses, community patterns were similar to contemporary data, suggesting that the ephemeral and dynamic nature of playas may already expose the odonate community to selective pressures possible under future land conversion.

Shallow depressions found in karst terrains may contain temporary (vernal) pools that are inundated seasonally in response to changes in meteorological conditions. The hydrogeology of 16 pools (0.06–0.4 ha) was studied in an Appalachian karst valley in central Pennsylvania, USA. The objective was to determine the effect of the geologic substrate on pool hydroperiod. Meteorological, geophysical, and hydrogeological data collected from November 1997–August 1999 and from January 2002–January 2004 suggested that hydroperiod was primarily controlled by meteorological conditions (total annual precipitation) and surficial aquifer geology. Multiple regression models were found to predict most of the spatial variability of pool hydroperiod with the following variables: thickness of the surficial sandy aquifer; sediment electrical resistivity; and annual precipitation. It might be expected that hydroperiod would be longer for clay pools than sandy pools because clay sediments can act as a seal to perch shallow ground-water and surface-water. Our data revealed the opposite to be true. Sandy residual sediments helped capture infiltration and direct this water along perched ground-water lenses or sheets to seasonal pools. This resulted in annual hydroperiods that were 115 days longer for sandy pools when compared to clay pools. The results suggest that the geologic substrate can be a major control on the duration of hydroperiod.

Managers at Smith and Bybee Wetlands Natural Area (SBW), an 800-ha preserve in Portland, Oregon, recently installed a water control structure to suppress invasive reed canarygrass (Phalaris arundinacea L.) with spring and summer flooding. We hypothesized that greater depth of flooding would decrease Phalaris growth and percent cover. We randomly established 27 transects throughout SBW before completion of the water control structure and measured percent cover of vegetation prior to flooding in autumn 2003 and then after one growing season in autumn 2004. We also monitored phenological characteristics of individual stands of reed canarygrass growing in different depths during 2004. Overall reed canarygrass cover decreased from 43.7% in 2003 to 41.2% in 2004 (McNemar's test; p < 0.001). Where inundation was > 0.85 m, reed canarygrass cover declined 6.1%. Where this deeper inundation coincided with regenerating willow forest, reed canarygrass cover declined 10.7%. Both before and after higher inundation, reed canarygrass cover was negatively correlated with plant species diversity (before: Spearman's rho  =  −0.67, p < 0.001; after: Spearman's rho  =  −0.41, p  =  0.036). Cover of several native taxa (e.g., Polygonum spp., Bidens spp., Salix lucida) increased in 2004. After flooding, reed canarygrass stands grew more slowly and changed their structural growth pattern. These findings suggest that managed flooding might be operationally useful in suppressing reed canarygrass.

QuickBird multispectral satellite images taken in September 2002 (peak biomass) and April 2003 (pre-growing season) were used to map emergent wetland vegetation communities, particularly invasive Phragmites australis and Typha spp., within a diked wetland at the western end of Lake Erie. An unsupervised classification was performed on a nine-layer image stack consisting of all four spectral bands from both dates plus a September Normalized Difference Vegetation Index image. The resulting eight cover classes distinguished three monodominant genera (Phragmites australis, Typha spp., Nelumbo lutea), three multigenera plant communities (wet meadow, other non persistent emergents, woody vegetation), and two unvegetated cover types (water, bare soil). Field validation at 196 data points yielded an overall classification accuracy of 62%, with producer's accuracy for the eight individual classes ranging from 41 to 91% and user's accuracy from 17 to 90%. Three-fourths of areas designated as Phragmites were correctly mapped, but 14% were found to be cattail (Typha) during field validation. Lotus (Nelumbo lutea) beds were accurately mapped on multiseason imagery (producer's accuracy  =  91%); these beds had not yet emerged above water in April, but were fully developed in September. Other types of non persistent vegetation were confused with managed areas in which vegetation had been cut and burned to control invasive Phragmites. Multiseason QuickBird imagery is promising for distinguishing certain wetland plant species, but should be used with caution in highly managed areas where vegetation changes may reflect human alterations rather than phenological change.

The sensitivity of wetland saturated hydraulic heads and water budgets to evapotranspiration (ET) was examined using a simplified hydrologic model and eight representations of ET. Estimates of ET that created the most reliable wetland saturated hydraulic heads and water budgets employed vegetation coefficients to correct potential ET, calculated by the Priestley-Taylor equation, to actual ET. The accuracy of simulated hydraulic heads generally improved by < 1 cm, however, when using the most reliable ET estimates based on vegetation coefficients. An ET estimate that used a regression-defined extinction depth created substantial errors in simulated water budgets. Specifically, the extinction-depth ET overestimated the annual actual ET by about 40% (400 mm). An ET approximation that overestimates actual ET by 400 mm annually applied in a regional hydrologic model over the 5400 km² area of Everglades National Park would underestimate the annual volume of water available for ground-water recharge and surface-water runoff to coastal estuaries by 2.3 billion m³. For comparison, this underestimation is about two thirds of the mean volume of water in Lake Okeechobee (3.8 billion m³), the largest lake in Florida, and clearly demonstrates unbiased estimates of ET are necessary for reliably simulating wetland water budgets.

In recent years, the loss and degradation of desert artesian springs has resulted in the loss of endemic species while other species have received “sensitive” designations. Bioassessment procedures have not been developed for groundwater-fed springs in the United States. Assessing the integrity of artesian springs is a challenge because of variable physico-chemical conditions among springs coupled with their unique hydrologic characteristics (a constant inflow of unpolluted water). We collected physico-chemical data and macroinvertebrates from 125 springs. Thirty-three springs clustered into three minimally impacted reference classes. We matched 39 test sites with one of these three classes. An integrated approach combining diversity indices, and aspects of multivariate analyses and multimetrics was more useful than any single method. Multivariate analyses (NMDS, ANOSIM and SIMPER) were particularly helpful in detecting trends at the community level and identifying specific indicator taxa (e.g., amphipods). However, macroinvertebrates in some springs did not respond to the potentially adverse effects of livestock grazing, perhaps because a variety of large ungulates historically frequented these springs (buffalo, elk, deer, etc.). Also, macroinvertebrate diversity increased with increasing disturbance; rare taxa were probably more easily detected as their densities increased with increased food availability in impaired sites. Expanding the scope of this study to artesian springs of the entire Great Basin Province may produce additional reference classes (e.g., > 20°C water temperatures) and provide a way to assess the integrity of all springs.

Vegetation zonation was investigated at an intermountain playa wetland (Mishak Lakes) in the San Luis Valley (SLV) of southern Colorado. Plant composition and abiotic conditions were quantified in six vegetation zones. Reciprocal transplants were performed to test the importance of abiotic factors in governing zonation. Abiotic conditions differed among several vegetation zones. Prolonged inundation led to anaerobic soils in the Eleocharis palustris and the submerged aquatics zones, on the low end of the site's 1.25 m elevation gradient. On the high end of the gradient, soil salinity and sodicity (a measure of exchangeable sodium) were high in the Distichlis spicata zone (electrical conductivity, EC  =  5.3 dS/m, sodium absorption ratio, SAR  =  44.0) and extreme in the Sarcobatus vermiculatus zone (EC  =  21 dS/m, SAR  =  274). Transplanted species produced maximum biomass in the zone where they originated, not in any other higher or lower vegetation zone. The greatest overall transplant effect occurred for E. palustris, which experienced a ≥ 77% decline in productivity when transplanted to other zones. This study provides evidence that physical factors are a major determinant of vegetation zone composition and distribution across the entire elevation gradient at Mishak Lakes. Patterns at Mishak Lakes arise from counter-directional stress gradients: a gradient from anaerobic to well-oxygenated from basin bottom to upland and a gradient from extremely high salinity to low salinity in the opposing direction. Because abiotic conditions dominate vegetation zonation, restoration of the altered hydrologic regime of this wetland to a natural hydrologic regime may be sufficient to re-establish many of the natural biodiversity functions provided by these wetlands.

Approximately 40,500 ha of Spartina-dominated marshes died during a drought-induced disturbance in Louisiana. This caused concern because in the absence of recovery, dieback marshes can subside, increasing the present high rates of wetland loss in coastal Louisiana. We assessed the recovery of one such dieback area after hydraulically dredged sediment-slurries were applied to the site to compensate for post-dieback soil consolidation. Five treatment-levels resulted from the sediment-slurry addition: 1) high elevation 2) medium elevation, 3) low elevation, 4) pop-up, and 5) vegetated. Plant recruitment within the five sediment treatment-levels were compared to two types of reference marshes: 1) ambient marshes, which neither died-back nor received sediment-enrichment, and 2) dieback marshes, which did not receive sediment addition. High and medium elevations had minimal recovery two years following the slurry addition, similar to that in reference dieback marshes. The low elevation, pop-up (highly organic sections of the original substrate that detached during slurry application and settled on top of the sediment-slurry), and vegetated (dieback areas that recovered by the start of the study) treatment-levels, all of which received sediment-slurry application, had rapid plant recovery. Plant recolonization was governed by optimal inundation, high organic matter content at high elevation, and rhizome survivability following sediment burial. If applied appropriately, sediment-slurry amendments can restore salt marshes submerging due to subsidence or other events, like sea-level rise, that may result in excessive plant submergence.

Projects of the scope of the restoration of the Florida Everglades require substantial information regarding ecological mechanisms, and these are often poorly understood. We provide critical base knowledge for Everglades restoration by characterizing the existing vegetation communities of an Everglades remnant, describing how present and historic hydrology affect wetland vegetation community composition, and documenting change from communities described in previous studies. Vegetation biomass samples were collected along transects across Water Conservation Area 3A South (3AS). Ten community types were present between November 2002 and 2005. Separate analyses for key a priori groups (slough, wet prairie, and sawgrass) provided detailed conclusions about effects of historic hydrology on the vegetation of 3AS. Communities were affected by hydrologic variables up to four years previous to the sample. We identified wet prairie/slough species such as Eleocharis spp. and Nymphaea odorata as short-term sentinel species of community change. Sawgrass and N. odorata should be monitored for long-term change. Comparisons to preceding studies indicated that many of the communities of previous times, when conditions were drier, no longer exist in our study area and have been replaced by deeper water community types.

We completed a shoreline survey of Phragmites occurrence and adjacent land use along more than 8,400 km of shoreline in the Maryland and Virginia portions of the Chesapeake Bay and its tidal tributaries. Phragmites occurred along 14.6% of Maryland estuarine shoreline in the mid-to-upper portion of Chesapeake Bay, but along only 2.0% of the surveyed Virginia shoreline in the mid-to-lower portion. The dramatic difference in occurrence was not related exclusively to high salinity restrictions on plant distribution in the lower portion of the bay since most of the survey was completed in mesohaline to oligohaline sections of the estuary. Phragmites occurrence was highest—up to 30% of all shoreline—in the upper northeastern section of the bay and was over-represented adjacent to cleared but undeveloped land. Although Phragmites was found growing adjacent to all types of land uses including undisturbed forest in the mid-to-upper estuary, its occurrence was positively correlated with the percentage of agricultural shoreline. The extensive Phragmites occurrence throughout the upper estuary suggests that both local and regional environmental factors of management concern may contribute to the suspected spread of Phragmites along both Maryland and Virginia shoreline.