We examined the relationship between water-table elevations and plant community distributions in a hydrologically restored riparian meadow. The meadow, adjacent to Bear Creek in northeastern California, experienced hydrologic modification due to “pond and plug” stream restoration. Plant species composition and cover were sampled within 128 plots, and a hydrologic model was used to simulate a three-year time series of water-table for each plot. TWINSPAN was used to classify the vegetation into four community types: Eleocharis macrostachya / Eleocharis acicularis, Downingia bacigalupii / Psilocarphus brevissimus, Carex nebrascensis / Juncus balticus, and Poa pratensis / Bromus japonicus. Nonmetric multidimensional scaling was utilized to investigate the relationships between community types and hydrologic variables. Community types were distributed along the hydrologic gradient at reasonably similar positions to those found in previous studies; however Carex nebrascensis, a species frequently used as an indicator of shallow water tables, occurred at greater water-table depths than reported in other studies. The range of water-table depths in this meadow was greater than previously observed, presumably due to the higher temporal resolution of water-table measurements, in addition to the intermittent nature of stream flow in Bear Creek. This study provides an increased understanding of the ecology of meadow communities, and can be utilized for improved design and objective setting in future restoration projects.

Human-induced and natural processes continue to act upon the estuaries of the northern Gulf of Mexico. Predictive models have been applied to project the interactions between habitat modification and population estimates for some estuarine species. However, these assessments may be furthered by focusing on a suite of species, such as a subset of the marsh birds that inhabit these ecosystems. During 2004 and 2005, we conducted point count surveys within the estuarine systems of Alabama and Mississippi, USA to assess whether small-scale wetland characteristics and a broader scale metric of habitat modification influenced the distributions of several marsh bird species: clapper rail (Rallus longirostris), common yellowthroat (Geothlypis trichas), least bittern (Ixobrychus exilis), marsh wren (Cistothorus palustris), and seaside sparrow (Ammodramus maritimus). On the basis of current habitat, we project change in species occupancy through several scenarios. Projections suggest that habitat alteration through loss of emergent marsh and increased cover of the halophyte Juncus roemerianus may be most influential to the distribution of these marsh bird species. Thus, continued alteration of existing conditions coupled with sea-level rise will likely have a significant impact on the distribution of this group of marsh bird species as well as the integrity of their habitat.

Baldcypress-water tupelo (cypress-tupelo) swamps are critically important coastal forested wetlands found throughout the southeastern U.S. The long-term survival and sustainability of these swamp forests is unknown due to large-scale changes in hydrologic regimes that prevent natural regeneration following logging or mortality. We used NWI wetland maps and remotely sensed hydrologic data to map cypress-tupelo communities, surface water, and the extent and location of proposed regeneration condition classes for cypress-tupelo swamps in the Atchafalaya Basin, LA. Only 6,175 ha (5.8%) of the 106,227 ha of cypress-tupelo forest in the Lower Atchafalaya Basin Floodway was classified as capable of naturally regenerating. Over 23% (24,525 ha) of the forest area was mapped as unable to regenerate either naturally or artificially. The loss and conversion of nearly 25,000 ha of cypress-tupelo forest would have significant and long-lasting impacts on ecosystem services such as wildlife habitat for birds and Louisiana black bears. Given the landscape-scale changes in surface elevations and flooding depths and durations throughout southern Louisiana, similar conditions and impacts are likely applicable to all coastal cypress-tupelo forests in Louisiana. Better data on flooding during the growing season are needed to more accurately identify and refine the location and spatial extent of the regeneration condition classes.

Bottom-up factors such as nutrient availability have long been thought to be the primary regulators of plant growth in salt marshes. However, that paradigm has been challenged by investigations showing that grazing by the periwinkle snail Littoraria irrorata regulates Spartina alterniflora growth through top-down forces. Our investigation was conducted between November 2003 and March 2007 within the North Inlet Estuary (NIE) salt marsh to examine relationships between S. alterniflora and L. irrorata. The primary goal was to determine if observed in situ densities of L. irrorata significantly decreased S. alterniflora productivity at the study sites. The results indicate that S. alterniflora productivity positively correlated with L. irrorata snail density during winter. However, no correlation was observed during summer. Hence, there was no inverse relationship between snail density and primary productivity and no support for the hypothesis of ‘top-down’ control of marsh plant production. A significant relationship between S. alterniflora stem density and L. irrorata density was observed during summer and winter, suggesting that stem density may play a key role in determining the distribution of periwinkle snails in NIE. These results challenge the applicability of the L. irrorata-S. alterniflora top-down control model as a generalized phenomenon in southeastern salt marshes.

Pine flatwoods (a mixture of cypress wetlands and managed pine uplands) is an important ecosystem in the southeastern U.S. However, long-term hydrologic impacts of forest management and climate change on this heterogeneous landscape are not well understood. Therefore, this study examined the sensitivity of cypress-pine flatwoods hydrology to climate change and forest management by using the physically based, distributed hydrologic modeling system, MIKE SHE. The model was first calibrated and validated with a long-term data set, and then applied using several hypothetical scenarios developed in north central Florida. Our study showed that MIKE SHE could simulate the temporal and spatial dynamics of the shallow ground-water table. The model also identified and confirmed three horizontal ground-water flow patterns at this study site. The modeling results suggested that forest removal and climate change (i.e., warming and drying) would have pronounced impacts on the ground-water table during the dry periods, but these impacts may be minor under wet conditions at this typical flatwoods landscape. At the landscape scale, depressional wetlands may have higher responses to tree removal and climate change than surrounding uplands.

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is among the most frequently detected pesticides in the water-column of surface waters in Canada. Bottom sediments (0 to 15 cm) were collected in 41 wetlands across the prairie region of Canada and analyzed for organic carbon content (OC), pH, and texture. Using batch equilibrium experiments at 5 and 25°C, the herbicide sorption coefficient, Kd, was determined for 41 sediments, along with more comprehensive herbicide sorption and desorption isotherms for 7 of these 41 sediments. The 2,4-D Kd was positively correlated with OC and negatively correlated with sediment pH. A small (3%) significant increase in the 2,4-D Kd occurred when the temperature was at 25°C rather than 5°C. Desorption rates were faster for sediments with ≤ 2.4% OC and exhibited little or no hysteresis, compared to sediments with ≥ 5.9% OC that consistently exhibited hysteresis. We conclude that bottom sediments could serve as a source of 2,4-D to the water-column regardless of water temperature (5 to 25°C). However, the potential for accumulation of 2,4-D in wetland sediments would be small because between 62 and 100% of the 2,4-D sorbed by sediments was released after 8 hours.

Understanding the nutritional quality of wildlife foods is important for management and conservation efforts. We report the gross energy and macronutrient content of 10 plant species consumed by endangered Hawaiian Moorhens (Gallinula chloropus sandvicensis) along with gross energy and macronutrient content of three plant species not known to be consumed by moorhen. We also report the same information for Urochloa mutica that is consumed when it is < 10 cm tall, but not when it is taller. We also compared macronutrient composition of plant species collected from sites with different soil moisture levels. Energy density, fat, ash, nitrogen, protein, carbohydrates, and fiber of these wetland plants were similar across soil moisture categories, but differed among plant species. We tested for rank consistency of nutrient values across species to determine if some were consistently high across measures, and we tested whether there were differences in energy and protein content between natives and non-natives, and between species consumed versus not eaten. Rank values of macronutrients were inconsistent across species, and we found no differences in energy or protein across groups of species. Information on Hawaiian Moorhen nutritional requirements and the species' ability to metabolize these different plants will help inform wetland managers.

Turloughs are karst wetlands unique to Ireland. We sought to elucidate mollusc community composition across a broad range of turloughs and to establish the major factors determining spatial distribution and community composition to better inform management decisions. Quantitative pond-net surveys for molluscs were conducted on Carex nigra dominated vegetation zones at each of eight turloughs. Surveys were conducted at each site twice – once just after flooding (early) and once before emptying (late). Thirteen other homogeneous zones were surveyed in the same way once, to assess relationships with environmental variables over the full hydrological gradient. The abundance of temporary-wetland specialists was significantly higher in the early as compared to the late samples, but late samples were more dissimilar to each other than early ones. Site was a more effective grouping variable than time of sampling for the Carex nigra community, and this effect was even higher when considering the whole hydrological gradient. The idiosyncratic nature of the turlough mollusc fauna was notable in both the indicator species analysis and the nestedness analysis. Results suggest a blanket approach to the conservation of turlough molluscan faunas is not appropriate and that turloughs should be considered individually when developing management recommendations.

We evaluated methodology for estimating total plant species richness in seasonally inundated depressional wetlands of the longleaf pine (Pinus palustris Mill.) ecosystem. Our objectives were to assess non-parametric estimators of plant species richness based on species incidence plot samples and to determine the minimum sampling requirement for accurate extrapolation of species richness. We quantified species accumulation in varying sample plot areas and spatial distribution within nine depressional wetlands. We recorded species presence on 1 m², 4 m², and 100 m² plots along transects extending across each wetland. Increasing sample area from 1 m² to 4 m² plots resulted in an increase in mean species richness up to 33%. EstimateS was used to estimate total species richness for each wetland and sampling method. Species accumulation curves did not reach a plateau and none of the estimates showed a convergence of estimated and observed richness. Due to the large number of unique species and the heterogeneous distribution of species in these hyperdiverse wetlands, we conclude that the most commonly used non-parametric estimators are not effective as tools to obtain accurate estimates of total species richness.

California's Tulare Lake Basin (TLB) is one of the most important waterbird areas in North America even though most wetlands there have been converted to cropland. To guide management programs promoting waterbird beneficial agriculture, which includes flooding fields between growing periods, we measured emergence rates of insects, an important waterbird food, in three crop types (tomato, wheat, alfalfa) in the TLB relative to water depth and days flooded during August–October, 2003 and 2004. We used corrected Akaike's Information Criterion values to compare a set of models that accounted for our repeated measured data. The best model included crop type and crop type interacting with days flooded and depth flooded. Emergence rates (mg m⁻² day⁻¹) were greater in tomato than wheat or alfalfa fields, increased with days flooded in alfalfa and tomato but not wheat fields, and increased with water depth in alfalfa and wheat but not tomato fields. To investigate the relationship between the range of diel water temperatures and insect emergence rates, we reared Chironomus dilutus larvae in environmental chambers under high (15–32°C) and low fluctuation (20–26°C) temperature regimes that were associated with shallow and deep (respectively) sampling sites in our fields. Larval survival (4×) and biomass (2×) were greater in the low thermal fluctuation treatment suggesting that deeply flooded areas would support greater insect production.

During 1999–2005, we studied aquatic invertebrate communities in 24 small, seasonally flooded wetlands (seasonal ponds) in aspen (Populus spp.)-dominated landscapes in north central Minnesota, USA. Sites were chosen from 2 different landforms, with 6, 6, and 12 wetlands selected from stands estimated to have been harvested 10–34 (young age), 35–58 (mid-age), and 59 (old age) years before onset of the study, respectively. Of 12 ponds in the old age group, six were clear-cut during the winter of 2000–2001. Direct gradient analysis indicated that invertebrate communities were influenced by canopy openness, total phosphorus, total alkalinity, maximum depth, and hydroperiod, although relationships were complex, with no single environmental variable explaining >9.3% of invertebrate variance. Invertebrate taxon richness was negatively correlated with stand age and was also lower during the period following tree removal. However, taxon richness declined to a lesser extent in harvested old age stands relative to unharvested controls during the post-harvest time period. Our results indicated the presence of weak relationships between invertebrate communities and environmental characteristics of seasonal ponds and adjacent uplands. Innovative research strategies are needed because adaptations of aquatic invertebrates may limit interpretation of responses to natural and anthropogenic gradients in these habitats.

We analyzed invertebrate abundance and richness associated with decomposing litter across three riverine wetlands with different inundation regimes located in the alluvial floodplain of the Paraná River. Three replicate bags were incubated for different types of leaf litter that were dominant in each wetland for five sampling dates, yielding a total of 165 litterbags. The number of invertebrates per g of remaining leaf litter differed among wetlands and was affected by leaf litter type and incubation date within each wetland. In contrast to abundance, differences in invertebrate composition were more pronounced across wetlands than across leaf litter types within a wetland. Different species dominated in each of the three wetlands. When we compared the number of invertebrates per g remaining of a single litter type (Eichhornia crassipes) across the three wetlands, variability in density was explained by the NH₄ content of the water and dissolved oxygen concentration. Many invertebrates associated with litter may not be directly involved in shredding the material, and collectors dominated invertebrate assemblages at study sites. Although both litter quality and wetland condition affect the invertebrates colonizing leaf litter, our results suggest that spatial heterogeneity, linked to connectivity, plays an important role in determining invertebrate assemblages.

With the recent Final Compensatory Mitigation Rule by the US Army Corps of Engineers and US Environmental Protection Agency, wetland mitigation banking has been designated as the preferred means of compensatory mitigation after avoidance and minimization of wetland impacts. Permits and supporting documents were reviewed and site visits conducted at 29 Florida wetland mitigation banks to assess their permit-based success. Just over half of the banks included three or more ecological criteria in permit success requirements. Release of a majority of potential credits (60–75%) was strongly based on completion of activities (e.g. conservation easement, financial assurance, ditch filling). A review of bank compliance suggested that over 40% of banks had reached final success criteria or were clearly trending towards success, but that 17% of the banks were not trending towards success. Most banks were deemed successful according to permit criteria and compliance considerations, although permit criteria were not explicitly tied to ecological considerations. While permit success criteria may have been met, it was unclear what level of functional performance wetland mitigation banks provided.

Structural properties of the cordgrass, Spartina foliosa, were studied in parallel with nitrogen fixation rates and diversity of nitrogen-fixing microbes (diazotrophs) for two years in sediments of an early successional (6 year old) and a mature marsh at Tijuana Estuary (California, USA) via acetylene reduction and genetic fingerprinting (T-RFLP with nifH). Nitrogen fixation rates reflected biannual dynamics and differences in S. foliosa between marshes. In initial comparisons (fall 2005), S. foliosa height and aboveground biomass were less developed and average nitrogen fixation rates were higher in the early successional marsh than in its mature counterpart. By the following fall (2006), sediment organic content, nitrogen fixation rates and total rhizosphere diversity were similar between marshes, but S. foliosa aboveground biomass and porewater ammonium remained lower in the early successional marsh and diazotrophic community composition differed significantly. Diazotroph assemblages in surface sediments consistently differed from those in S. foliosa rhizospheres of the late-successional marsh, but not in the younger marsh, where rhizosphere diazotroph richness (T-RFs) declined from 2005 to 2006 in parallel with aboveground biomass of S. foliosa plants. These dynamics of diazotroph communities and S. foliosa suggest that ecological interactions of microbes and plants significantly influence wetland ecosystem function and succession.

There has been an increasing interest in characterizing and mapping isolated depressional wetlands due to a 2001 U.S. Supreme Court decision that effectively removed their protected status. Our objective was to determine the utility of satellite remote sensing to accurately detect isolated wetlands. Image segmentation and object-oriented analysis were applied to Landsat-7 imagery from January and October 2000 to map isolated wetlands in the St. Johns River Water Management District of Alachua County, Florida. Accuracy for individual isolated wetlands was determined based on the intersection of reference and remotely sensed polygons. The January data yielded producer and user accuracies of 88% and 89%, respectively, for isolated wetlands larger than 0.5 acres (0.20 ha). Producer and user accuracies increased to 97% and 95%, respectively, for isolated wetlands larger than 2 acres (0.81 ha). Recently, the Federal Geographic Data Committee recommended that all U.S. wetlands 0.5 acres (0.20 ha) or larger should be mapped using 1-m aerial photography with an accuracy of 98%. That accuracy was nearly achieved in this study using a spatial resolution that is 900 times coarser. Satellite remote sensing provides an accurate, relatively inexpensive, and timely means for classifying isolated depressional wetlands on a regional or national basis.

Road salt, a common pollutant in regions with snowy winters, enters roadside wetlands when temperatures are low and organisms are physiologically inactive and remains until flushed by snowmelt or rainfall. Flushing might not occur until spring temperatures rise and organisms are physiologically active. Thus, effects of road salt on aquatic organisms must be studied within the context of temperature. We monitored temperature and conductivity at the sediment–water interface from January to May 2004–2006 in two constructed wetlands in Erie, Pennsylvania. Runoff caused peaks in conductivity (up to ∼30 mS/cm) followed by exponential declines. Conductivity remained >4 mS/cm during winter and returned to <1 mS/cm in late spring (temperature >10°C). Overspray caused lower peaks (<∼6 mS/cm), and values reached baseline early in spring. Winter/spring chironomid abundance was significantly lower in wetlands that received salt than in other wetlands. We used a factorial-design laboratory study to test whether survival of chironomid larvae exposed to NaCl was temperature dependent. At 1°C and 5°C, low concentrations of salt appeared to increase survival; at 22°C all concentrations of salt significantly decreased survival. Salt might protect larvae in winter and increase survival if flushed before spring thaw, but could be detrimental after temperatures rise.

Mean soil respiration rates (carbon dioxide efflux from bare soils) among salt marshes in Narragansett Bay, RI ranged from 1.7–7.8 µmol m⁻² s⁻¹ in Spartina patens in high marsh zones and 1.7–6.0 µmol m⁻² s⁻¹ in S. alterniflora in low marsh zones. The soil respiration rates significantly increased along a gradient of increasing watershed nitrogen (N) loads (S. alterniflora, R²  =  0.95, P  =  0.0008; S. patens, R²  =  0.70, P  =  0.02). As the soil respiration increased, the percent carbon (C) and N in the soil surface layer decreased in the S. alterniflora, suggesting that in part, the increased soil respiration rates are contributing to the increased turnover of labile organic matter. In contrast, there were no apparent relationships between the soil respiration rates in the high marsh and the soil C and N contents of the surface layer. However, there was a broad-scale pattern and significant inverse relationship between the high marsh soil respiration rates and the landscape belowground biomass of S. patens. As more and more salt marsh systems are subjected to increasing nutrient loads, decomposition rates of soil organic matter may increase in marsh soils leading to higher turnover rates of C and N.

Typha x glauca (hybrid cattail) is an aggressive invader of wetlands in the upper Midwest, USA. There is widespread concern about declines in plant diversity following Typha invasion. However, relatively little is known about how Typha alters habitat characteristics, i.e., its potential to act as an “ecosystem engineer”. Over five years, we measured physical, chemical, and plant community changes associated with Typha invasion in a Lake Huron wetland in northern lower Michigan. We compared uninvaded areas with patches varying in invasion intensity. Our study was observational, but we used statistical inference to try to separate effects of Typha and confounding variables, particularly water depth. We used space–for–time substitution to investigate whether Typha–associated changes increased over time, as predicted if Typha invasion was in part a cause (not only a consequence) of abiotic changes. Relative to uninvaded areas, Typha–invaded areas differed in plant–community composition and had lower species richness, higher litter mass, and higher soil organic matter and nutrient concentrations (all P < 0.001). Overall, Typha invasion appeared to displace native species and enrich wetland soils. These changes could benefit Typha at the expense of native species, potentially generating plant–soil feedbacks that pose special challenges for wetland management and restoration.

After channellization of the Kissimmee River, the primary land use of the drained floodplain was cattle pasture but included sod farms. A project to restore the river began in 1999. One of its goals is to reestablish the three dominant, pre-channelization vegetation types (wetland shrub, broadleaf marsh, and wet prairie) in areas where they previously were found. We investigated whether indicator species of these three vegetation types were present in 53 permanent quadrats on the drained floodplain. All seven indicator species were found in the permanent quadrats. We also examined three potential sources of propagules (relict wetlands, seed banks, and several surrogates of hydrochory) for these indicator species. All seven species were found in adjacent relict wetlands; and six were found in the seed banks of permanent quadrats. Based on binomial logistic regressions, the presence of relict wetlands and surrogates for flooding (relative elevation, total days flooded) can predict the presence or absence of most of these indicator species. Sod farming reduced the presence of wet-prairie and broadleaf marsh indicator species in permanent quadrats, in adjacent relict wetlands and in the seed bank. The potential importance of relict wetlands for the re-vegetation of the floodplain was our most important finding.

We examined factors that influence the expansion of alder forests in a wetland isolated by dikes and drainage ditches in northern Japan. Using aerial photographs, airborne laser scanner data, and existing elevation data, we described the spatial distribution and heights of alder forest in 2002 and the spatial distribution in 1977. We also measured water level and water quality in 2002. The mean water level was slightly lower than the ground surface, and water level fluctuation was minimal. The study site was mesotrophic, but salt concentration was high. The alder forest expanded around the area adjacent to the alder forests present in 1977, and the canopy cover ratio increased over a wide area. A generalized linear model suggested that water level and quality and the previous distribution of reproductively mature trees controlled the expansion pattern of the alder forest. A decrease in water level fluctuation promoted initial establishment, while an increase in fluctuation promoted height growth. A decrease in salt concentration or acidity promoted both initial establishment and growth. Flood protection by dikes may change spatial distribution of alder trees by narrowing water level fluctuation, restricting fruit dispersal, and reducing tree mortality.

Land-surface subsidence and erosion are the principal processes that form accommodation space in interior coastal wetlands when they are converted to open water. The relative contribution of subsidence and erosion to wetland loss can be estimated by comparing elevations and vertical offsets of stratigraphic contacts that are correlated between adjacent sediment cores. Accommodation-space measurements assume that wetland-sediment thicknesses and the elevation of stratigraphic contacts were originally nearly uniform over short horizontal distances (tens to hundreds of meters). The accommodation space attributable to erosion equals the difference in wetland-sediment thickness between wetland cores and adjacent open-water cores taken at formerly emergent wetland sites. The accommodation space attributable to subsidence equals the elevation difference of a stratigraphic marker correlated between the two cores using the wetland core as the reference standard. Together, subsidence plus erosion at an open-water core location equals the accommodation space created by land loss, which is the difference between the adjacent emergent wetland elevation and the existing water depth.

Nutrient dynamics and seasonal vegetation growth were examined in a newly formed floating marsh dominated by Panicum virgatum in the Mississippi River delta. The floating marsh formed in a shallow aquatic environment receiving secondarily treated municipal effluent. Net Areal Primary Productivity (NAPP), total belowground biomass, NO₃, and plant-tissue δ¹⁵N ratios varied significantly (P < 0.05) along a 75-m marsh transect, while mean plant-tissue δ¹³C values differed between the dominant species. The area nearest the effluent discharge had the highest NAPP (3876 g m⁻² y⁻¹), total belowground biomass (4079.0 ± 298.5 g m⁻²), and mean NO₃ (5.4 ± 2.9 mg l⁻¹). The mean δ¹⁵N of Hydrocotyle umbellata floating marsh was less enriched at 0–75 m (9.7 ± 1.9‰) compared to 100–200 m (21.0 ± 3.8‰). The δ¹³C of the belowground peat mat of the floating marsh was similar to P. virgatum but not H. umbellata, indicating that P. virgatum was forming the mat. Nutrient availability affected NAPP and δ¹⁵N. NAPP was greater than most reported values for floating marsh from 0–45 m then decreased along with NO₃ concentrations and δ¹⁵N further from the effluent source. These results suggest that nutrient rich freshwater can promote restoration of some floating marshes.

Using remote sensing and geographic information system technologies, we analyzed changes in ecosystem boundary conditions in the Yellow River Delta. We investigated variations in soil water, bulk density, total nitrogen, total phosphorus, and organic matter, as well as concentrations of soluble Ca² , K , Mg² and Na , under different ecosystem conversions. Results indicated that from 1992 to 2006, boundary characteristics became more complicated and ecosystem conversion was mainly from farmland to a mixed ecosystem supporting Tamarix chinensis-Phragmites communis. These ecosystem conversions may be attributed to a combination of urban expansion, oil exploration and extraction, water interception, and soil salinization. Ecosystem conversion also affected soil properties. Organic matter differed among the ecosystems, as did the concentrations of the soil base cations. Ca² concentration was higher than concentrations of other cations, and significant differences existed in Ca² and Mg² concentrations among ecosystems. While the concentration of K and Mg² showed similar concentrations, mostly increasing, among different ecosystem conversions, Na concentrations decreased. In summary, the concentrations of soluble minerals were significantly influenced by ecosystem conversions.

The loss of coastal wetlands throughout the Hawaiian Islands has increased the numbers of created (CW) and restored (RW) wetlands. An assessment of these wetlands has yet to occur, and it has not been determined whether CWs and RWs provide the same functions as natural wetlands (NWs). To address these concerns, vegetation and soil characteristics of 35 wetlands were compared within sites along hydrologic gradients and among sites with different surface water salinity and status (i.e., CW, RW, NW). Only 16 of 85 plant species identified were native and three of the four most abundant species were exotic. Vegetative characteristics differed primarily across salinity classes, then along hydrologic zones, and to a lesser extent among CWs, RWs, and NWs. Soil properties exhibited fewer differences across salinity classes and along hydrologic zones and greater differences among CWs, RWs, and NWs. The dominant presence of invasive species in coastal Hawaiian wetlands suggests that it will be difficult to locate reference sites that can be used as restoration targets. Differences in edaphic characteristics suggested that RWs/CWs do not exhibit the same functions as NWs. Future restoration and creation should include planting of native vegetation, controlling invasive vegetation, and alleviating inadequate soil conditions.

Wetlands of the Great Lakes region are increasingly dominated by invasive cattails (Typha angustifolia and Typha X glauca) which form dense stands of live and dead biomass that may reduce plant diversity. We hypothesized that differences in plant litter accumulation explain cattail dominance under certain hydrologic regimes related to wetland hydrogeologic setting. We investigated cattail abundance, litter accumulation, and species density in three bayside wetlands hydrologically connected and three protected wetlands hydrologically isolated from Lake Ontario. Mean litter biomass was higher in bayside wetlands (1.7–2.6 vs. 0.4–1.2 kg/m²) and negatively related to species density (p  =  0.004) in both settings. A litter addition experiment demonstrated that fallen litter negatively influenced seedling survival (p  =  0.061) and species density (p  =  0.024). Decomposition rates accounted only partially for higher overall litter accumulation in bayside wetlands. Growing season water levels in bayside wetlands tracked Lake Ontario levels and showed less variation than protected wetlands. More stable water levels and higher density of standing dead stems in bayside wetlands may limit litter fragmentation, resulting in greater litter accumulation. Thus, anthropogenic and natural factors affecting cattail litter production, fragmentation, and decomposition could influence species diversity in coastal wetlands.

Identifying sites meeting wetland hydrology requirements is simple when long-term (>10 years) records are available. Because such data are rare, we hypothesized that a single-year of hydrology data could be used to reach the same conclusion as with long-term data, if the data were obtained during a period of normal or below normal rainfall. Long-term (40–45 years) water-table and rainfall data were obtained for two sites in North Carolina (with modeling), and one site in Minnesota (direct measurements). Single-year wetland hydrology assessments were made using two-rainfall assessment procedures recommended by the U.S. Army Corps of Engineers for their Wetland Hydrology Technical Standard, and two other rainfall assessment methods that were modifications of those procedures. Percentages of years meeting wetland-hydrology conditions during normal or drier than normal periods were identified for each plot with each rainfall assessment method. Although the wetland hydrology criterion was met in over 90% of the years across all plots using the long-term records, the four assessment techniques predicted the criterion was met in 41–81% of the years. Based on our results, we recommend that either the Direct Antecedent Rainfall Evaluation Method, or its modified version, be used for wetland hydrology assessment.

Low nutrient availability in salt marsh ecosystems can potentially limit primary productivity and subsequent carbon export to coastal waters. In temperate marshes with low external nitrogen inputs, nitrogen (N₂) fixation may enhance availability of usable nitrogen to marsh plant communities and increase their growth. The effects of sub-surface soil amendment of polysaccharides on rhizosphere N₂ fixation, and on plant growth and tissue characteristics of the California cordgrass, Spartina foliosa, were tested in microcosms in a tidal simulator. Polysaccharide was added as alginate extract, and rhizosphere N₂ fixation and plant characteristics were measured over 9 weeks. N₂ fixation rates increased 10-fold in the alginate treatment compared to controls after 1 week of exposure as a result of increased availability of a readily usable form of carbon. N₂ fixation rates in amended sediment were significantly higher than rates in control sediments at weeks 1 and 3. Although plant characteristics did not differ between treatments, trends of increased number of leaves and shoots in amended plants compared to controls appeared between weeks 7 and 9. The potential for increased plant growth following an increase in N₂ fixation rates warrants further investigation as it may have implications for recovery of N-limited disturbed and restored salt marshes.

Constructed farm ponds represent a major wetland habitat type in southeastern Minnesota. Farm ponds are subject to a variety of disturbances associated with agricultural land use, especially sedimentation and eutrophication. Chironomid community structure often reflects environmental changes in aquatic ecosystems. However, chironomid communities in farm ponds are poorly understood and their response to short-term increases in sedimentation and eutrophication remains undetermined. We studied relationships between pond-land cover condition and chironomid community structure. Of the 40 ponds selected for the study, 10 were natural, permanent palustrine wetlands. The remaining ponds were constructed habitats (i.e., farm ponds) with 10 in each of the following categories: non-grazed grassland, grazed grassland, and row crop agriculture. Larval chironomids and water quality parameters were collected during early, mid-, and late summer 2001. Total nitrogen concentrations were significantly greater and turbidity was generally greater in grazed grassland ponds as compared to all other pond types. Chironomid communities of grazed grassland ponds were characterized by lower taxonomic richness and abundant chironomids tolerant of increased sedimentation and nutrient enrichment (i.e., Chironomus and Glyptotendipes). This study determined that agricultural land use, particularly cattle grazing, can markedly affect pond water quality, thereby influencing the chironomid community structure in farm ponds.