The sawgrass Cladium jamaicense forms extensive, quite monospecific stands within coastal swamps of the Caribbean region. Fire acts as an important ecological factor in the control of vegetation dynamics in these marshes. In the archipelago of Guadeloupe, during the dry season, fires are set as a customary practice nearly each year. The purpose of this study was to characterize the ecology of Cladium marshes in Guadeloupe and to assess more specifically floristic and structural changes that might occur within these marsh communities once the setting of fires has been discontinued. Fifty-four 2 × 10 m plots were set up along seaward/landward transects including mangrove and swamp forest edges. The main characteristics of soil and vegetation in a regularly burned marsh were compared to those of two marshes where the setting of fires had been discontinued for at least 15 years. Cladium height and species richness were negatively correlated to water level, redox potential, and salinity, and followed decreasing landward/seaward gradients. Discontinuation of fire regime modified the vertical structure of the vegetation and the marsh flora by promoting woody species vs. herbaceous species. Paleoecological investigations are needed for a better understanding of the influence of anthropogenic fires in the long-term dynamics of such marshes.

Most amphibians that breed in seasonal wetlands are predominantly terrestrial animals that require “upland” habitats for the majority of their life cycles. However, wetland regulations aimed partially at protecting wildlife values are often limited to the wetland basins and small terrestrial “buffer zones” that typically extend 30 m or less from the wetland edge. In this study, we assessed whether a common buffer zone (i.e., 30 m) is sufficient for the conservation of marbled salamanders (Ambystoma opacum). We installed and monitored two concentric and continuous drift fence arrays (3 m and 30 m from the pond margin) around each of three seasonal ponds in western Massachusetts, USA. We quantified the numbers and percentages of breeding adults and emerging juvenile salamanders that immigrated from and/or emigrated beyond the 30-m fences. In addition, we recorded incidental year-of-emergence captures of juveniles at more distant drift fences that were in place for a broader study. Of the breeding adults captured immigrating to the basins at 3-m fences, 84–96% were first captured at 30-m fences, and corrections for capture probabilities suggested that nearly 100% of these individuals originated beyond 30 m from their breeding sites. Of the newly emerging juveniles captured emigrating from the basins at 3-m fences, 58–85% were subsequently captured at 30-m fences and 284 juvenile captures were recorded at distances between 111 and 1,230 m (median = 269.2 m) from natal ponds. Our findings highlight the dramatic limitations of existing wetland regulations with regard to upland habitat use by mole salamanders (family Ambystomatidae) and the need to approach conservation of these animals both at broader scales and with more comprehensive and innovative strategies.

We assessed salt marsh use by foraging egrets in coastal Rhode Island, USA. Two species [great egret (Ardea alba) and snowy egret (Egretta thula)] nest in mixed-species colonies on islands in Narragansett Bay and regularly forage in adjacent salt marshes. We surveyed 13 salt marshes approximately twice weekly during the breeding and post-breeding seasons in 2001 and 2002. Based on resource selection functions, foraging great and snowy egrets strongly preferred pools within salt marshes, while mosquito control ditches were rarely used. Foraging egrets were never detected in stands of common reed (Phragmites australis). The number of egrets using individual marshes varied considerably, although density estimates were far less variable. Salt marsh area was better at predicting the mean number of foraging egrets using a marsh than landscape-level parameters, such as distance to the nearest nesting colony or the total area of salt marsh within 5 km. Carefully designed salt marsh restoration projects could benefit local egret populations because it appears that foraging habitat availability may be a limiting factor. To ensure use by foraging egrets, salt marsh restoration designs should increase the availability of pool and open water habitat, reduce common reed, and modify deep ditches and channels to make them more accessible for foraging egrets.

The Heron Lake System historically has been an important resource for waterfowl in Southern Minnesota, USA. In the early 1900s, the system was a major nesting, feeding, and staging area for breeding and migrating waterfowl mainly due to the extensive growth of sago pondweed, Stuckenia pectinata. In recent years, the abundance of S. pectinata has decreased dramatically. We conducted a study from 2002 through 2003 to identify factors limiting the success of S. pectinata. Distribution and biomass of S. pectinata differed significantly over the years of this study. Biomass was related to environmental factors, including water transparency and water temperature early in the season. Water transparency during May (time of early growth) had a negative relationship with maximum biomass at each site over all years. Water temperature had a positive relationship with increases in seasonal biomass yield of S. pectinata in the Heron Lake System.

Carex stricta dominates sedge meadows in southern Wisconsin, USA. In contrast with invasive species that dominate as monotypes, C. stricta supports a diversity of co-occurring species by forming tussocks. Concerns about diversity loss and the potential to restore species-rich tussocks led us to ask how tussocks foster high species richness and affect composition. Our study of 181 tussocks at three sites showed that tussocks structure sedge meadow vegetation by adding both surface area and micro-habitats. Tussocks, which average 15–25 cm tall, increase surface area of an otherwise flat plot by 40%. Species richness was positively correlated with tussock size, but the patterns differed among sites. At a site where water was deep, tussock height was the best predictor of richness; at two other sites, surface area and circumference were the best predictors. Micro-habitats differed in conditions and species composition: tussock tops were high in light, variable in temperature, and high in litter cover. Tussock sides had less litter but more moss; off-tussock areas tended to be aquatic. Of the 56 taxa found, 34 showed significant affinities for one or more micro-habitats. Of these, four species occurred primarily on tops, several extended from tops to lower levels, seven aquatic taxa preferred areas off-tussocks, and one species specialized in tussock sides. Over the 2004 growing season, species richness increased in an additive process, from 35 species in May to 56 in September 2004. Cover of litter and moss increased and bare surface decreased with season, but only seven of the 34 taxa with micro-site preferences expanded their distributions as the September drawdown exposed the off-tussock micro-habitat. We conclude that tussocks enhance species richness in three ways, by increasing surface area, by providing multiple micro-habitats, and by undergoing seasonal changes in composition. Our detailed data on plant-diversity support by large tussocks form a benchmark for tussock meadow conservation, as well as a target for restoration of degraded meadows.

The flood pulse of the Illinois River (Illinois, USA) has been distorted and the floodplain extensively modified as a result of human activity. This activity has changed the historic flood regime from moderate, late winter-early spring flood pulses, followed by a summer drawdown period, to a chaotic hydrology with floods occurring throughout the year. Boltonia decurrens (Torrey and Gray, Wood), federally listed as a threatened species, is endemic to the Illinois River floodplain. The species occurs as a large metapopulation; however, flood regime and habitat alteration have substantially reduced the size and number of populations within the metapopulation. We developed a geographic information system (GIS) to analyze habitat and geospatial population dynamics for B. decurrens. We analyzed floodplain land cover, identified specific wetland patches supporting B. decurrens, quantified habitat availability, habitat pattern, and analyzed the distribution of populations and individuals by wetland type and flood regime for the census period 1984– 2001. Our results show that floodplains of the navigation pools analyzed were dominated by row crop agriculture and forested wetlands with five land-cover types accounting for >90% of floodplain land-cover. Distribution analyses indicate that more populations and larger populations of B. decurrens occur on non-forested wetlands than forested wetlands. Habitat has been reduced for the species, and remaining habitat is highly fragmented with reduced connectivity. Patch occupancy rates were ≤ 1% for each pool and for all pools combined. Colonization and extinction rates fluctuated widely during this study, and there were no significant differences in the means of these rates for each individual pool and for all pools combined. Although during this study, there was relative stability between colonization and extinction rates, low patch occupancy combined with habitat reduction and reduced connectivity leaves the species vulnerable to extinction.

Constructed wetlands are used throughout North America to treat various types of wastewater in warm climates; however, little has been documented about their treatment processes and efficiencies during winter periods in Atlantic Canada. Two small-scale constructed wetlands (100 m²) of differing operational depth (wetland 1: 0.15 m shallow zone depth and wetland 2: managed water level) were designed to treat agricultural wastewater at the Bio-Environmental Engineering Center of the Nova Scotia Agricultural College. Both wetlands were monitored from November 2000 through March 2002 to evaluate treatment efficiencies and mass reductions of five-day biological oxygen demand (BOD₅), total suspended solids (TSS), total phosphorus (TP), and ammonia-nitrogen (NH₃-N). An average loading rate of 44.7 kg BOD ha⁻¹ d⁻¹ was loaded into each wetland, even during winter months. Percent removal and mass reductions for BOD₅, TSS, TP, and NH₃-N in both wetlands, irrespective of water levels, ranged from 62 to 99%. The treatment of TP was not found to be as effective as the other parameters, especially during high loading periods. Results show promise for the operation of constructed wetlands on a year-round basis in Atlantic Canada.

The hydrogeomorphic (HGM) wetland assessment method has been developed to provide a much-needed, ecologically-sound means for classifying, assessing, and comparing wetland hydrodynamics and related functions. A first step in using the HGM is the identification of ‘biogeographical regions’ to characterize regional wetland subclasses. I found no attempts to test existing ecoregions or other subclassification methods in the glaciated Great Lakes basin for use with HGM. Two subclassification methods are tested here. One ecosystem classification (based on geology, climate, topography, and other large-scale variables) is compared with a method based solely on the permeability of underlying glacial deposits. Water-level fluctuation, conductivity, and alkalinity were monitored for three years to determine whether differences in hydrodynamics and water chemistry existed between depressional wetlands using either subclassification method. The hydrodynamics of inland wetlands differed significantly between subclasses based on either method. The permeability-based subclasses were also effective in differentiating wetland water chemistry. Aspects of the ecosystem classification, however, provided additional information not accounted for by the permeability-based method. Thus, the ecosystem classification provides better biogeographical regions for use with HGM in the glaciated Great Lakes basin.

The re-establishment of native plant communities, in particular the re-creation of ridge (sawgrass dominated; Cladium jamaicense) and slough (Eleocharis spp. and Nymphaea odorata) habitat, is a significant component of Everglades restoration. Two wetland species indicative of pristine slough habitats are Eleocharis cellulosa and Rhynchospora tracyi. This study conducted controlled experiments to examine three factors affecting seed germination of native slough species: 1) seed viability and the affect of burial length, 2) soil phosphorus (P) concentrations, and 3) allelopathic properties of cattail (Typha spp.). Two soil P levels (high and low) and two seed burial durations (three and five months) were chosen to represent field conditions to which these species are exposed. Allelopathic properties were determined using extracts from cattail plants. Eleocharis germination significantly decreased in high P soil concentrations (>500 mg/kg) compared to low P soil, independent of seed burial length as well as decreased germination between control (de-ionized water) and high concentration cattail extracts. For Rhynchospora, seed germination was significantly reduced between the three-month and five-month burial lengths regardless of nutrient levels. There were also significant reductions in seed germination upon exposure to cattail extracts as a result of allelopathic compounds. The seed germination results could be influenced by localized site aspects associated with high soil P causing increased microbial activity, which subsequently degraded seed viability. Additionally, dense cattail stands reduce light and temperature at the soil surface adversely affecting germination. Germination appears to be inhibited by a combination of factors indicative of high nutrient marsh areas. Therefore, germination and adult population re-establishment may be more successful in transition zones found between enriched and un-enriched marsh areas.

We characterized soil and the concentrations of solutes in soil solutions and in stream water in and around a wetland located within a first-order stream in a forested watershed at the Hubbard Brook Experimental Forest (New Hampshire, USA). We hypothesized that the in-stream wetland would retain solutes in stream water, especially Ca² , H , and strong acid anions (NO₃⁻, SO₄²⁻). Rather, the wetland had subtle impact on stream water chemistry causing slightly greater Na concentrations and lesser concentrations of H and dissolved inorganic C (DIC). We expected anaerobic microbial denitrification and SO₄²⁻ reduction in wetland soils to consume the strong acid anions and account for less H , but Na release was responsible. The wetland soil produced dissolved organic C (DOC) but did not export it into stream water. The DOC was saturated with monomeric Al, suggesting a sink rather than source for Al. Soil extracted with 1 M NH₄Cl yielded much larger amounts of Ca² and Mg² than in the surrounding mineral forest soil, whereas NH₄ , K , and Na budgets were smaller in the wetland soil than in the forest soil. Characterization of soil surface charge and organic matter fractions revealed distinct differences between wetland soil organic matter (SOM) and forest soil SOM. Our results suggest that the wetland behaves much like gelatin: the organic matrix holds water tightly, such that stream water flows mostly over the matrix rather than entering and forcing much of the old water into runoff. The subtle biogeochemical role of the wetland adds to the complex interactions that control solute mobility in small watersheds.

Desert playas can be unambiguously identified in a geological context. However, identifying those portions of desert playas that are defined as either three-parameter wetlands or Waters of the United States (WoUS) in the Clean Water Act (CWA), and thus under the jurisdiction of Federal agencies charged with enforcing the CWA, is sometimes problematic. Although the WoUS definition specifically includes playas, the guidance for playa delineation is not as highly developed as that for wetlands. Delineating WoUS on desert playas involves determining the Ordinary High Water Mark. Field experience has demonstrated that the indicators for Ordinary High Water on desert playas have not been fully identified nor have they been associated with ponding that represents the limits of Ordinary High Water. This report discusses the distribution of indicators above, below, and at the Ordinary High Water Mark. Fifteen playa features are identified for possible delineation use and are rated for reliability and their relationship to the Ordinary High Water position.

Sediment filtration potential is well known as a key function of riparian forests; however, the capacity of riparian ecosystems to accumulate sediment without degradation is unclear. This study examined the effects of sediment deposition on productivity, vegetation composition, and structure in riparian forests of ephemeral streams at Fort Benning, Georgia, USA. Sedimentation occurs at Ft. Benning as a result of erosion from unpaved roads situated in sandy soils along slopes and ridges. Seven ephemeral streams were selected to represent a range of sediment deposition rates, and another two were selected as reference catchments. Within all nine catchments, paired plots were established with one plot being delineated in an upper portion of the catchment and another lower, nearer to the ephemeral stream. Upper plots of disturbed catchments showed evidence of sediment accumulation, such as buried tree bases and alluvial fans, while lower plots lacked those indications. Aboveground net primary productivity (ANPP), litterfall nutrient contents, leaf area index (LAI), species composition, and stand structure were compared within and among catchments. Decreases in litterfall, woody increment, ANPP, and LAI were observed with sediment accumulation rates near 0.2 cm yr⁻¹, and an equilibrium response appeared to be reached near 0.5 cm yr⁻¹. Nutrient contents of litterfall followed a similar pattern. Changes in species composition and structure were also observed. In general, reference catchments and lower plots were associated with closed overstory canopies, whereas upper plots had more overstory mortality and heavier densities of saplings and seedlings of shade-intolerant species. These results suggest that sedimentation rates commonly occurring in some riparian forests may alter productivity, structure, and composition. Consequently, riparian functions that are closely linked to forest integrity may be jeopardized as well.

Methods of wetland delineation require presence of three parameters: hydric soils, wetland hydrology, and hydrophytic vegetation. Currently accepted methods to assess these parameters often have inconsistent agreement among the parameters in bottomland hardwood forested wetlands. This study characterized soil morphology, hydrology, and vegetative composition in a bottomland hardwood forest in east Texas, USA. Alternate methods for assessment of the three parameters were examined with the aim of determining if there is an approach that provides better agreement among parameters than methods in current use. We compared four methods for determining dominance ratios and a prevalence index to assess the status of vegetation. The most stringent method of assessment and the method that provided best agreement with soil and hydrology parameters at this site was a prevalence index. We compared three criteria to assess the hydrology parameter: (1) length of growing season as defined by air temperature greater than −2°C (28°F) vs. 0°C (32°F), (2) saturation or inundation for 5% vs. 12.5% of the growing season, and (3) saturation to within 30 cm vs. 15 cm of the soil surface. Length of growing season had little or no effect on the outcome at this site; duration of required hydrology had the greatest influence over agreement with vegetation and soil parameters. We also compared the field method used to determine presence of hydric soil when sampling was conducted in 1995 with currently used field indicators. The combination that, in general, provided better agreement among the three parameters at this site was saturation to within 15 cm of the surface for 12.5% of the growing season, using current field indicators for hydric soil. Despite having been mapped as a wetland by the National Wetlands Inventory, under current federal guidelines, most of this bottomland hardwood forest would not be a jurisdictional wetland as defined by Clean Water Act regulations.

An exclosure experiment was carried out at two sites in Delta Marsh, Manitoba, Canada to investigate the role of fish in limiting the growth of submersed macrophytes. The experiment consisted of three treatments: (1) fine-mesh exclosures designed to exclude both planktivorous fish and carp, (2) coarse-mesh exclosures designed to exclude adult carp but admit smaller fish, and (3) reference plots marked with corner stakes but without sides. Treatments were established in mid-May, and macrophyte biomass was sampled from within the exclosures in late August to assess treatment effects. Exclosure treatments had strong effects on the macroalgae Chara, with biomass 11.9-fold greater in full-exclosure plots than in reference plots, and 3-fold greater in carp exclosures than in reference plots. Exclosure treatments had no effect on above-ground or below-ground biomass of Stuckenia pectinata, the most widespread and abundant macrophyte in Delta Marsh. Thus, fish appear to limit macrophyte growth in Delta Marsh, but the effect of fish exclusion was dependent on species composition of the macrophyte assemblage.

In the Platte River Valley of central Nebraska, USA, riparian grasslands (also known as wet meadows) have been severely impacted by a reduction in river flows, causing lower ground-water levels and altered seasonal hydroperiods. The potential impacts of these hydrologic changes, as well as the environmental factors that influence wet meadow soil invertebrate communities, are not well understood. An understanding of the ecological processes that influence these invertebrate communities is crucial for maintaining and restoring wet meadows along the Platte River. Our objectives were to describe the soil invertebrate community of wet meadows throughout the growing season and to examine the relative roles of abiotic factors in determining patterns in invertebrate community structure. We conducted the study in 12 wet meadows along the Platte River during 1999 and 2000. We identified 73 invertebrate taxa; 39 were considered soil inhabitants. Total biomass was primarily composed of earthworms, Scarabaeidae, Isopoda, and Elateridae, with earthworms and Scarabaeidae accounting for >82%. Differences in river flow and precipitation patterns influenced some soil invertebrates. Earthworms and Scarabaeidae declined dramatically from 1999 (wet year) to 2000 (dry year). The topographic gradient created by the ridge-swale complex affected several soil invertebrate taxa; Scarabaeidae, Diplopoda, and Lepidoptera biomasses were greatest on drier ridges, while Tipulidae and Isopoda biomasses were greatest in wetter sloughs. Responses of earthworm taxa to the topographic gradient were variable, but generally, greater biomasses occurred on ridges and mid-elevations. Water-table depth and soil moisture were the most important variables influencing wet meadow soil invertebrates. Because these communities are linked to the hydrologic processes of the Platte River, future alterations of wet meadow hydrology could shift the distribution patterns of many of these invertebrates and possibly eliminate more moisture-tolerant taxa. To maintain wet meadows and their biotic communities, flow management should focus on regaining as much as possible of the former hydrograph through properly timed flows that provide an adequate hydrologic regime for wet meadows. In addition, restoration of wet meadows will depend on restoring the natural topography of wet meadows.

Wetlands in many inland catchments are being subjected to increasing salinity. To expand our limited understanding of how increasing salinity will alter carbon and nutrient dynamics in freshwater sediments, we carried out microcosm experiments to examine the acute effects of increasing salinity on the anaerobic cycling of carbon, nutrients (N, P, and S), metals (Fe and Mn), and microbial community structure in sediments from a non-salt-impacted freshwater wetland. Sediments were collected from a wetland on the River Murray floodplain, south eastern Australia and incubated with NaCl concentrations ranging from 0 to 100 mmol L⁻¹. Increasing NaCl concentration led to the immediate release of between about 80 and 190 μmol L⁻¹ ammonium and 235 to 3300 μmol L⁻¹ Fe(II) from the sediments, the amount released ‘increasing with NaCl concentration. Conversely, net phosphate release decreased with increasing NaCl concentration. The overall microbial community structure, determined from phospholipid fatty acid profiles, changed only at the highest NaCl loadings, with evidence of a decrease in microbial diversity. Bacterial community structure, determined by examining terminal restriction fragment length polymorphism (T-RFLP) of the bacterial 16S rRNA gene, showed little response to increasing NaCl concentration. Conversely, the archaeal (methanogen) population, determined by examining T-RFLP of the archaeal 16S rRNA gene, showed significant changes with increasing NaCl loading. This shift corresponded with a significant decrease in methane production from salt-impacted sediments and therefore shows a linkage between microbial community structure and an ecosystem process.

The location and distribution of wetlands and riparian zones influence the ecological functions present on a landscape. Accurate and easily reproducible land-cover maps enable monitoring of land-management decisions and ultimately a greater understanding of landscape ecology. Multi-season Landsat ETM imagery from 2001 combined with ancillary topographic and soils data were used to map wetland and riparian systems in the Gallatin Valley of Southwest Montana, USA. Classification Tree Analysis (CTA) and Stochastic Gradient Boosting (SGB) decision-tree-based classification algorithms were used to distinguish wetlands and riparian areas from the rest of the landscape. CTA creates a single classification tree using a one-step-look-ahead procedure to reduce variance. SGB uses classification errors to refine tree development and incorporates multiple tree results into a single best classification. The SGB classification (86.0% overall accuracy) was more effective than CTA (73.1% overall accuracy) at detecting a variety of wetlands and riparian zones present on this landscape.

Three saline evaporation ponds formed by wastewater from a solar energy-generating facility near Harper Dry Lake in the Mojave Desert of California, USA were compared for differences in the communities of benthic and planktonic invertebrates and algae present along with avian visitation and foraging activity. Salinity of the ponds ranged from near 90 to over 200 g L⁻¹ total dissolved solids. During the period of study (1997–1999), the lowest salinity pond averaged 98 g L⁻¹, the intermediate salinity pond 112 g L⁻¹, and the high salinity pond 173 g L⁻¹. Differences in the biological communities, abundance of invertebrates and algae, and avian foraging were examined in relation to these differences in salinity. Only three aquatic invertebrate species were present in substantial numbers, a water boatman (Trichocorixa reticulata), a brine shrimp (Artemia franciscana), and a brine fly (Ephydra gracilis). An abundance of the predator Trichocorixa under low salinity conditions appeared to reduce algae-grazing Artemia, and so released phytoplankton growth, but this was observed only in surveys later in the growth season when populations were mature and had greatest potential for efficient consumption of resources. Brine fly larvae were also fed upon by Trichocorixa and were least abundant in the low salinity pond. At highest salinities where Trichocorixa could not survive, Artemia were abundant and waters were usually clear, becoming dense with phytoplankton only during the winter dormancy of brine shrimp. Intermediate salinity levels supported some water boatmen, often coexisting with dense brine shrimp and phytoplankton populations, and the greatest dry mass of benthic brine fly larvae and pupae. The high salinity pond produced abundant but small Ephydra larvae and pupae, accompanied by reduced emergence success of adult flies. Birds appeared to forage primarily on benthic brine fly larvae and were most successful in the intermediate salinity pond, possibly because lower salinity resulted in loss of this preferred prey to water boatman predation, and high salinity produced prey of poor quality. These observations suggest that reduced salinity may at times mediate a trophic cascade within a simple food chain, where an invertebrate predator may reduce primary consumers and permit enhanced algal density, but the predation control becomes uncoupled as salinity increases. In the case of the ponds studied here, there appeared to be minimal risk associated with selenium poisoning of water birds because Se was not detected in brine fly larvae or pupae and was found only occasionally in low content in the brine shrimp and corixids and mostly in locales where few birds were found feeding.

Hydric soils are identified on-site using morphological features called “field indicators”. It is not known how long it takes for these indicators to form, nor whether they occur in created wetlands inundated for approximately 5% of the growing season, which is the minimum duration needed to meet wetland hydrology requirements. This study evaluated formation of redoximorphic features and hydric soil field indicators under field conditions following controlled, short-term floods that produced ponding events. A flood plain was constructed along an artificial stream channel (100-m long) where flooding was controlled by dams at each end of the channel. Floodwaters inundated soils on the flood plain nine times over a 3-year period. Ponded water was kept on the soils for periods ranging from 4 to 44 days. During ponding events, Fe² concentrations were approximately 1 to 4 mg/L, which indicated that the soils were anaerobic and undergoing Fe reduction. Redox depletions formed in A horizons following a single 7-day ponding event. Abundance of depletions increased from 2% to an average of 15% after nine ponding events. Most depletions were approximately 1 cm in diameter and had Munsell hues of 2.5Y and 5Y, values of 4, and chromas of 2 or less. The depletions appeared to form in place by loss of both Fe and C. Hydric soil field indicators developed in all plots after nine ponding events over a 3-year period and included the depleted matrix, redox dark surface, and a variant of the depleted dark surface. All indicators formed by a reduction and/or oxidation of Fe.

We quantified the influence of agricultural activities on environmental and biological conditions of floodplain wetlands in the upper Missouri River basin. Seasonally-flooded wetlands were characterized as low impact (non-disturbed) or high impact (disturbed) based on local land use. Biological data collected from these wetlands were used to develop a wetland condition index (WCI). Fourteen additional wetlands were sampled to evaluate the general condition of seasonally-flooded floodplain wetlands. Structural and functional attributes of macrophyte, algae, and macroinvertebrate communities were tested as candidate metrics for assessing biotic responses. The WCI we developed used six biological metrics to discriminate between disturbed and non-disturbed wetlands: 1) biomass of Culicidae larvae, 2) abundance of Chironomidae larvae, 3) macroinvertebrate diversity, 4) total number of plant species, 5) the proportion of exotic plant species, and 6) total number of sensitive diatom species. Disturbed wetlands had less taxa richness and species diversity and more exotic and nuisance (e.g., mosquitoes) species. Environmental differences between low and high impact wetlands included measures of total potassium, total phosphorus, total nitrogen, alkalinity, conductance, and sediment phosphorus concentration. Canonical analyses showed that WCI scores were weakly correlated (P = 0.057) with environmental variables in randomly selected wetlands. In addition, mean WCI score for random wetlands was higher than that for high impact wetlands, implying that floodplain wetlands were less impacted by the types of agricultural activities affecting high impact sites. Inter-year sampling of some wetlands revealed that WCI metrics were correlated in 2000 and 2001, implying that biological metrics provided useful indicators of disturbance in floodplain wetlands.

Wetlands improve water quality through denitrification, but these ecosystems are also an important source of the greenhouse gas, methane. The objective of this research was to determine the effect of two common macrophyte species (Juncus effusus and Salix nigra) on denitrification and on the methane cycle. The research was conducted in a newly constructed wetland on the Columbus campus of The Ohio State University during two growing seasons. In the wetland, some plots were left unplanted, while others were planted with Salix or Juncus species (i.e., 3 treatments; n = 15 per treatment). For each treatment, we quantified concentrations of methane at two depths (15 and 25 cm) in the sediment, emissions of methane from the sediment and through the plants, and denitrification rates. During most of the second growing season, both species had a limited effect on denitrification and methanogenesis. The effects of the plants became evident by the end of the second growing season and during the third growing season. During the third growing season, Salix species enhanced the release of the greenhouse gas methane to the atmosphere, while Juncus limited the emission of methane. In comparison to the unplanted plots, the long-term removal of nitrate by denitrification was favored in the plots planted with Juncus and was not affected by Salix. Our study provides evidence that certain plants (such as Juncus) can be planted in constructed wetlands to favor denitrification, while buffering methane emission.

We studied the effects of number of visits, point placement, and vegetation type on bird species richness and relative abundance indices using the Marsh Monitoring Program (MMP) bird point-count-protocol. We also assessed the performance of MMP point counts versus flushing lines. The study was conducted at Great Lakes coastal and inland emergent wetlands, southern Ontario, Canada. At the scale of an individual point, increasing number of visits yielded significant increases in cumulative species richness up to nine visits in flooded, interspersed, inland wetlands, and up to five visits in relatively dry, dense, coastal wetlands. Presence at points for six of eight common species could be determined with 90% certainty with three visits. Point placement at the edge versus the interior of large vegetation patches within large wetlands had no effect on species richness or relative abundance counts. Flushing lines detected significantly fewer species than did point counts and did not significantly improve relative abundance estimates of individual species.

Corrections can be used to estimate actual wetland evapotranspiration (AET) from potential evapotranspiration (PET) as a means to define the hydrology of wetland areas. Many alternate parameterizations for correction coefficients for three PET equations are presented, covering a wide range of possible data-availability scenarios. At nine sites in the wetland Everglades of south Florida, USA, the relatively complex PET Penman equation was corrected to daily total AET with smaller standard errors than the PET simple and Priestley-Taylor equations. The simpler equations, however, required less data (and thus less funding for instrumentation), with the possibility of being corrected to AET with slightly larger, comparable, or even smaller standard errors. Air temperature generally corrected PET simple most effectively to wetland AET, while wetland stage and humidity generally corrected PET Priestley-Taylor and Penman most effectively to wetland AET. Stage was identified for PET Priestley-Taylor and Penman as the data type with the most correction ability at sites that are dry part of each year or dry part of some years. Finally, although surface water generally was readily available at each monitoring site, AET was not occurring at potential rates, as conceptually expected under well-watered conditions. Apparently, factors other than water availability, such as atmospheric and stomata resistances to vapor transport, also were limiting the PET rate.

This study examined the response of Argilla Marsh in Ipswich, Massachusetts, USA to increased tidal flushing instituted to restore a salt marsh invaded by Phragmites australis. In late fall 1998, we replaced the old 0.9-m-diameter culvert feeding this marsh with a 2.4 × 1.5-m box culvert, thus increasing both the volume of tidal exchange and porewater salinity. We carried out yearly sampling of vegetation for two years pre-restoration and for four years after restoration. Analysis of Similarities (ANOSIM) showed that the plant community on the restored marsh had changed after restoration but that on the reference marshes had not. Over 80% of the change in the restored marsh was attributed to an increase in Spartina alterniflora cover and decreases in the cover of Phragmites australis, Typha angustifolia, and Solidago sempervirens. The two brackish species, P. australis and T. angustifolia showed an immediate negative response to the increased flooding and salinity. Surviving P. australis culms in the restored marsh were shorter in stature than they were prior to restoration, suggesting that the increased flooding and porewater salinities had lowered the productivity of this species. The increase in S. alterniflora post-restoration fit an exponential curve, indicating that there was a lag in its response initially, but then it expanded rapidly and was still in a very rapid expansion phase after four years. Despite an overall decline of P. australis on the scale of the whole marsh, there was a great deal of variation in responses of individual patches of P. australis to the restoration. Some declined, some were unchanged, and some even increased. The response of nekton to the restoration was less obvious than that of vegetation. Before restoration, the creek system in the tidally restricted marsh functioned like an impoundment that was only marginally connected to the larger salt marsh ecosystem. At that time, seining indicated that more species of nekton occurred at greater densities in creeks in the tidally restricted marsh than in the downstream reference. Increasing the tidal amplitude in the restored marsh resulted in an overall decline in the catch per unit effort there. In contrast to the creeks, the Spartina-dominated section of the flooded marsh surface in the restored marsh did harbor more Fundulus heteroclitus, particularly the smaller size class, than did the downstream reference marsh or a P. australis patch in the restored marsh. Our analysis of vegetation and nekton suggests that Argilla Marsh was still adjusting to hydrologic changes four years after restoration.

Leaf decomposition rates of nine types of litter, ranging in lignin content from 1.04 to 25.71%, were measured at three wetlands with different inundation regimes and related to internal and external factors. In these sites (located in the alluvial floodplain along at transect perpendicular to the main channel of the Paraná River), 180 litter bags were incubated under water. To test the importance of initial nitrogen, lignin, phosphorus, or L:N content of the litter in predicting decay rates, we analyzed the relationship between leaf quality and dry weight remaining (at 30 days and at the end of the incubation) within each wetland and under uniform environmental conditions. To elucidate the effects of environmental factors (especially hydroperiod) on decomposition processes, we compared the decay coefficient of one of these species (Eichhornia crassipes) across the three wetlands. Our results strongly suggest that under uniform environmental conditions, decomposition rates were best explained by a single internal factor related to litter quality. We found two different situations. 1) In the marsh with riverine forest, where decomposition was rapid and the half-life of the litter ranged from 9.6 to 63 days, the initial nitrogen content of leaves was a good predictor of decay rates both at 30 days and at the end of the incubation. 2) In the oxbow lake and palm swamp forest, where decomposition was lower and the half-life varied between 31.5 and 219 days, the L:N explains the variability on dry weight remaining at the end of the incubation. The decay coefficient of E. crassipes across sites was significantly related to NO₃⁻ concentration of water. We concluded that both environmental variables (i.e., the fluvial quotient of connectivity and the number of days in high water) and leaf litter quality (i.e., nitrogen content and L:N) are important factors regulating leaf litter decomposition in Paraná River floodplain wetlands.

Restoring depressional wetlands or geographically isolated wetlands such as cypress swamps and Carolina bays on the Atlantic Coastal Plains requires a clear understanding of the hydrologic processes and water balances. The objectives of this paper are to (1) test a distributed forest hydrology model, FLATWOODS, for a Carolina bay wetland system using seven years of water-table data and (2) to use the model to understand how the landscape position and the site stratigraphy affect ground-water flow direction. The research site is located in Bamberg County, South Carolina on the Middle Coastal Plain of the southeastern U.S. (32.88° N, 81.12° W). Model calibration (1998) and validation (1997, 1999–2003) data span a wet period and a long drought period, which allowed us to test the model for a wide range of weather conditions. The major water input to the wetland is rainfall, and output from the wetland is dominated by evapotranspiration. However, the Carolina bay is a flow-through wetland, receiving ground water from the adjacent upland, but recharging the ground-water to lower topographic areas, especially during wet periods in winter months. Hypothetical simulations suggest that ground-water flow direction is controlled by the gradient of the underlying hydrologic restricting layer beneath the wetland-upland continuum, not solely by the topographic gradient of the land surface. Ground-water flow may change directions during transition periods of wetland hydroperiod that is controlled by the balance of precipitation and evapotranspiration, and such changes depend on the underlying soil stratigraphy of the wetland-upland continuum.

A dominant determinant of successful amphibian dispersal from vernal pools and colonization of other pools in a metapopulation is pool hydrology and hydroperiod. We created a hydrologic model for vernal pools inhabited by wood frogs (Rana sylvatica). The hydrologic model used a classic water-budget approach, which had been applied to larger water bodies but not vernal pools. Depth profiles for eight pools in Cloquet, Minnesota, USA were measured for the open water seasons from June 2000 to September 2002. In the model, we adjusted infiltration rates and runoff coefficients to match depth profiles measured in 2000 and 2001 most closely. The simulated and observed depth profiles for 2000 and 2001 agreed well. In an assessment using novel depth profiles from 2002, modeled depths were somewhat deeper than observed depths for three pools, and four pools included sources of inflow that could not be explained by the model. We believe that the difference was from ground-water inflow rather than systematic changes in parameters, such as runoff curve numbers, because fit was good in 2000 and 2001, and some pools actually filled in 2002 during conditions when they typically would lose volume. Modeling hydroperiods using our methods for all pools in a region is problematic, as depth information is required for each pool studied, but the model will perform reasonably well for even small pools with adequate depth data.

Perennial African C4 grasses are highly successful invaders in tropical and subtropical environments. One of these species, Echinochloa pyramidalis, has been introduced in the freshwater wetlands of the Mexican tropics. This alien species reduces biodiversity by replacing native species. The removal of non-indigenous species from invaded communities often requires different techniques such as physical, chemical, or biological controls. We evaluated the effects of mechanical (cutting or soil-disking) and chemical (spraying Round Up^TM herbicide) disturbance treatments on the plant community of a freshwater marsh invaded by E. pyramidalis. We predicted that intense disturbance would eliminate this African grass from the experimental plots. Over a nine-month period, we analyzed species cover, richness, and diversity in experimental plots that received different disturbance treatments. Also, we measured the aerial biomass at the end of the experiment. The treatment that best reduced the dominance of E. pyramidalis and increased the diversity of native species was soil disking, but this was not enough to eliminate the grass. After nine months, E. pyramidalis recovered in all the treatments and again became the dominant species. To eliminate this species completely, it is necessary to recreate the natural topography and hydrology of the wetland and to select control mechanisms that disrupt those growth characteristics (e.g., rapid propagation from rhizomes and horizontal expansion via tillers) that make this grass more competitive than native species.

Uncertainty about the effects of ongoing natural and anthropogenic changes to Great Lakes ecosystems, such as managed stabilized water levels, coupled with widespread public interest regarding status of wetland birds prompted us to evaluate sensitivity of regional wetland birds to hydrologic changes. We reviewed published literature to determine preferred habitat of 30 wetland birds in the region, emphasizing vegetation required for foraging and nesting during the breeding season. Species were subsequently assigned to one of three risk categories based on association with vegetation types sensitive to water-level stabilization, as well as nesting height above water. Notably, of the bird species designated as low, moderate, and high risk, 25%, 33%, and 63%, respectively, have been regionally declining based on Bird Studies Canada's Marsh Monitoring Program. This evaluation may be useful to regional biologists, planners, and managers concerned with predicting how particular species might be affected by future hydrologic changes in this and related systems.

CO₂ efflux from tropical peat swamp substrates was measured under three different land uses (selectively logged forest, recently burned and cleared forest, and agriculture) in Jambi Province, eastern Sumatra over a six-month period that incorporated parts of both the major wet and dry seasons. Clearance of peat swamp forest and cultivation led to increased emissions: mean CO₂ effluxes ranged from 2.59 ± 0.22 μmolCO₂ m⁻² sec-¹ for peat beneath selectively logged forest to 4.44 ± 1.16 μmolCO₂ m⁻² sec-¹ beneath recently burned and cleared forest to 5.58 ± 1.34 μmolCO₂ m⁻² sec-¹ beneath settled agriculture. Mean CO₂ effluxes were significantly correlated with soil temperature at 20 cm depth (Q₁₀ = 2.5) and water-table position. We combined SPOT satellite and CO₂ efflux data to establish that the conversion of selectively logged forest to agricultural land has led to a substantial increase in annual emissions of CO₂–C in the study area.

We conducted Least Bittern (Ixobrychus exilis) surveys on Reelfoot Lake and nearby Black Bayou Waterfowl Refuge, in northwest Tennessee, USA during May–June 2003 to determine the distribution of Least Bitterns among structurally different vegetation types, including giant cutgrass (Zizaniopsis miliacea), swamp loosestrife (Decodon verticillatus), and woody vegetation. Least Bitterns were historically abundant on Reelfoot Lake when giant cutgrass once occupied 1,000 ha, but water-level stabilization resulted in 93% of the emergent zone now being dominated by swamp loosestrife interspersed with trees and saplings, including baldcypress (Taxodium distichum) and maple (Acer spp.). Least Bitterns were detected 49 times. Sites with Least Bitterns had greater percent giant cutgrass coverage, less woody vegetation coverage, and fewer tall trees than sites where Least Bitterns were not detected; however, Least Bittern presence was positively related with only giant cutgrass coverage and was unrelated to woody vegetation coverage or tall tree density. Density of Least Bitterns was greater on Black Bayou (0.45/ha) than Reelfoot Lake (0.11/ha). The lower density of Least Bitterns on Reelfoot Lake is partially attributed to the shift in the dominant emergent species from a grass to a shrub. In the absence of vegetation management, Least Bitterns will continue to decline on Reelfoot Lake as many swamp loosestrife marshes convert to forests.

The U.S. federal government has developed lists of plant species that occur in wetlands. The initial purpose of these lists was to enumerate plants that grow in wetlands and that could be used to identify wetlands according to the U.S. Fish and Wildlife Service's wetland classification system. The first list was generated in 1976 by the Service, and since that time, the list has undergone several iterations as more information was reviewed or became available through field investigations and scientific research. Two lists are currently published and available for use: a 1988 list and a 1996 draft list. The latter list represents an improvement based on nearly 10 years of field work by the four signatory agencies plus comments from other agencies, organizations, wetland scientists, and others. The national list was generated from 13 regional lists. These data have not been summarized previously; this note provides an interregional summary of vital statistics. The 1988 list included 6,728 species, while the 1996 list has nearly 1,000 additions for a total of 7,662 species (a 14% increase). Roughly one-third of the nation's vascular plants have some potential for being hydrophytes—plants growing in water or on a substrate that is at least periodically deficient in oxygen due to excessive wetness. Each species on the list is assigned an indicator status reflecting its frequency of occurrence in wetlands: 1) obligate (OBL; >99% of time in wetlands), 2) facultative wetland (FACW; 67– 99% in wetlands), 3) facultative (FAC; 34–66%), 4) facultative upland (FACU; 1–33%), and 5) upland (UPL; <1%). From 1988 to 1996, the regional lists of potentially hydrophytic species increased by more than 39 percent in three regions: Caribbean, North Plains, and Central Plains. The percent of OBL, FACW, and FAC species on the lists decreased in the Northeast and Hawaii. The percent of OBL and FACW species also decreased in the Southeast and Northwest. The number of OBL species declined in all but three regions, whereas the number of FACU species added to the lists increased in all regions except Hawaii. The regional “wetland plant” lists have been used to help identify plant communities that possess a predominance of wetland indicator plants (i.e., a positive indicator of hydrophytic vegetation) and to identify wetlands that can be recognized solely based on their vegetation.