The hydrology of wetlands located in urban landscapes is likely to be affected by the numerous effects of urban development on the water cycle. Although urbanization is affecting an increasingly large amount of wetland area, there have been few studies documenting hydrologic patterns in such wetlands. We have studied a set of 21 forested wetlands distributed through northeastern New Jersey, USA, a region characterized by dense residential and commercial development. The sites varied widely in area (6–500 ha), and all were bordered by urban land uses. In ten sites, water levels were monitored for 2.5 yr in shallow wells and piezometers; in all sites, qualitative indicators of hydrology, vegetation, and soil indicators of wetland hydrology were sampled. The sites were placed in five hydrogeomorphic (HGM) classes (depression, slope, riverine, mineral flats, and mineral flat-riverine) and also in three qualitative classes of hydrologic disturbance (low, medium, and high). We examined water-level dynamics, variability, the occurrence of discharge/recharge conditions, and the frequency of occurrence of hydrologic indicators across both HGM and disturbance classifications. Qualitative indicators of hydrology did not reveal differences in hydrology that were apparent from the quantitative data, the soils, and the vegetation. Mineral flat-riverine sites were the most wet, and the riverine sites the most dry, but hydrologic disturbance tended to blur distinctions among HGM classes by creating relatively dry conditions in most site types. Sites with a high level of hydrologic disturbance also tended to be more “flashy,” regardless of HGM class. We conclude that the utility of HGM classifications and qualitative indicators of hydrology in urban/suburban landscapes are limited by the high degree of variability in both the extent and particularly the sources of hydrologic disturbance. We conclude that the hydrology of wetlands in an urban region reflects not only the hydrogeomorphic setting but also the unique set of disturbances from current and historical land-uses found at each site.

The frequency distributions of mire water pH are often bimodal in data sets covering the poor-rich gradient in vegetation. Area-representative data sets of pH could indicate ecologically meaningful differences between regions, independent of differences in mire classification. Comparisons of pH results are, however, hindered by differences in water sampling methods. We conducted a field survey to assess variation of water pH related to the poor-rich gradient, the water-table-depth gradient, time of day, aeration of samples, and different methods of obtaining water samples. Considerable diurnal and fine-scale vertical and horizontal variation of pH was found in samples obtained by depressing from bryophyte capitula or directly from open water surfaces. A diurnal pattern of lower pH at night and higher at day was found, typically with a 0.5–1.0 pH unit range. Open surface-water samples showed a wide range of fine-scale horizontal variation (pH 4.6–8.0) in Scorpidium-flarks, while pipe-well samples were less variable both in unaerated samples (pH 5.0–5.3) and in aerated samples (pH 6.6–7.3). The frequency distributions of pH of both unaerated and aerated pipe-well samples were bimodal in a data set covering the transition from rich to poor fen. The higher mode was located at pH 5.6 for unaerated samples and at pH 7.6 for aerated samples. The results conformed to the hypothesis of a bimodal frequency distribution of water pH along the poor-rich gradient. A combination of measurements from unaerated and aerated water samples obtained from pipe wells is suggested as a standard method for comparable pH measurements in mires.

We assessed whether peat mining intensity influences the use of bog ponds by green frogs (Rana clamitans). We selected 21 ponds in three areas undergoing different levels of peat mining: 1) mined (vegetation completely removed exposing bare peat, presence of drainage ditches with little or no water), 2) in preparation to be mined (vegetation intact but presence of drainage ditches filled with water), and 3) natural (vegetation intact, absence of drainage ditches). We estimated green frog abundance and reproduction using a combination of sampling techniques. Green frogs were detected more often at ponds in the moderately disturbed section than at ponds in either the mined bog or natural sections. Furthermore, no green frogs called at ponds on mined surfaces, as opposed to ponds on either natural or moderately disturbed surfaces. Tadpoles occurred only in the moderately disturbed section. This suggests that ponds on mined surfaces provide suboptimal habitat for green frogs. Within the moderately disturbed section, drainage ditches may provide additional breeding habitat and facilitate movements between ponds. However, if this positive effect occurs, it is only temporary because moderately disturbed sections are inevitably mined. Although preserving vegetated corridors or buffer zones around bog ponds within mined surfaces may not necessarily increase pond use by amphibians in the short term, it will facilitate the restoration phase of mined sites by providing a source of dispersers of bog plants and wildlife, including amphibians.

Submerged macrophytes are important components of wetland ecosystems in the Prairie Pothole Region of North America, but factors influencing species abundance and community structure are poorly known. We sampled submerged macrophyte communities and habitat characteristics in 18 prairie wetlands for five years in order to 1) assess interspecific relationships between macrophyte species, 2) test for presence of distinct species assemblages at the whole-basin level, and 3) identify relationships between community composition and limnological characteristics of the wetland basins. Macrophyte communities did not occur as distinct assemblages of species; most species showed eurytopic distributions, and communities varied along gradients of individual species abundances. Redundancy analysis showed that turbidity, presence/absence of fish, drainage history (restored versus non-drained), average depth, and surface area explained 20% of the variance in species abundance. However, turbidity and drainage history alone accounted for 15% of this variance. Most species showed a negative relationship with turbidity, while drainage history influenced community composition but had little effect on overall abundance at the community level. Our results indicate that restored and non-drained wetlands have similar species richness but differ in species composition. Species richness and total plant abundance in both restored and non-drained wetlands will be greatest in wetlands with low turbidity, moderate depth, and small surface area. However, substantial residual variation indicates that additional, unstudied factors are important determinants of community structure.

Stable carbon isotope ratios (δ¹³C) and C/N atomic ratio {(C/N)_a} were used to investigate the sources and fate of organic matter in Khung Krabaen Bay, Thailand (KKB) and to assess the effect of shrimp pond effluent on the KKB system. Five major sources (mangroves, seagrass, algae, plankton, and shrimp feeds) contributing organic matter into waters and sediments were identified. Statistically significant differences between the δ¹³C values and (C/N)_a of mangrove leaves (δ¹³C ∼ −29‰ (C/N)_a ∼ 40–105), seagrass (δ¹³C ∼ −11‰ (C/N)_a ∼ 19), and algae (δ¹³C ∼ −16‰ (C/N)_a ∼ 18) were found, while plankton (δ¹³C ∼ −21‰ (C/N)_a ∼ 5–6) and shrimp feeds (δ¹³C ∼ −23‰ (C/N)_a ∼ 7) had similar values. The most negative δ¹³C values of particulate organic matter (POM) and sediments in the mangrove area indicated that mangroves were the major sources of organic matter in this area. The δ¹³C levels in POM and in sediments found in the canals indicated that the organic matter was predominantly of mangrove origin rather than from shrimp-pond effluent. High nitrogen content in mangrove leaves and in sediments, and the low nutrient concentrations in the bay waters, suggested that the KKB system was not affected by shrimp-pond effluent during the sampling period. These results showed that mangroves were probably effective in trapping nutrients from shrimp-pond effluent. In the inner bay area, sources of POM were a mixture of seagrass, algae, and plankton, while sediments contained a strong signature from seagrass and algae. Plankton represent a major source contributing organic matter to POM and sediment in the offshore area. Our results showed that the δ¹³C value was a good tracer in identifying sources and fate of organic matter. On the other hand, the (C/N)_a was less reliable in identifying organic matter sources because the original sources in POM and, particularly, sediment may be lost or masked by biochemical alteration. However, the combined analysis of δ¹³C and (C/N)_a provided substantially more information regarding the source and fate of organic matter in the KKB system than could be achieved by using one tracer alone.

Aquatic invertebrates are essential components of duckling diets, but little is known about temporal changes of invertebrate populations in different types of brood habitats. In spring and summer 1996 and 1997, we conducted searches for duck nests in upland fields in the Grasslands Ecological Area in California's Central Valley to determine timing of nest initiation and hatching. We also sampled aquatic invertebrate populations in adjacent permanent wetlands, semi-permanent borrow areas within seasonal wetlands that were drawn down in spring, and reverse-cycle wetlands (i.e., wetlands flooded from spring to summer) to estimate invertebrate food resources available to ducklings. Abundances of many invertebrates important in duckling diets (Gastropoda, Cladocera, Ostracoda, Amphipoda, Corixidae, Dytiscidae, Hydrophilidae) were greater in borrow areas and reverse-cycle wetlands than in permanent wetlands. Peak macroinvertebrate densities in borrow areas occurred immediately after adjacent wetlands are drawn down in March–April. Peak densities in reverse-cycle wetlands and permanent wetlands occur in May. Although total numbers of microinvertebrates (<1 mm size) and macroinvertebrates (≥1 mm size) in all wetlands decreased after May, most mallard (Anas platyrhynchos) and cinnamon teal (A. cyanoptera) eggs hatched in May. Therefore, these ducklings hatch when abundant invertebrate food resources were most available in reverse-cycle wetlands. In contrast, most gadwall (A. strepera) eggs hatched in June after invertebrate numbers started to decrease. In areas where hydrology is controlled, managing for reverse-cycle wetlands may be a useful strategy to provide abundant invertebrate food resources during the waterfowl breeding season.

We compared the ecophysiological performance of four dominant, perennial plant species of tidal marshes of northeastern North America (Phragmites australis, Typha angustifolia, Spartina alterniflora, and Leersia oryzoides), asking whether species that fall along a continuum of invasiveness vary consistently in terms of primary productivity, growth, biomass allocation, phenology, maximal photosynthetic rate, leaf turnover, tissue nutrient and chlorophyll content, and water use. During 1999, we examined plants growing at two brackish marshes and two freshwater tidal marshes in southern Connecticut, USA. Phragmites and Typha consistently exceeded the other two species in both marsh types in terms of ramet biomass, standing crop, length of the growing season, standing leaf area, leaf longevity, and total chlorophyll. Typha, Phragmites, and Spartina showed similar maximal photosynthetic rates across marsh types, significantly greater than the P_max observed in Leersia. Foliar nitrogen was significantly greater in Phragmites than in all other species, suggesting that this species accrues nutrients more efficiently. Phragmites and Typha populations did not differ in a number of characters between freshwater and brackish marshes, indicating low sensitivity to exposure to moderate salinity levels. A principle components analysis placed Phragmites and Typha close to each other and more distant from Spartina and Leersia along axes describing components of competitive ability and photosynthetic performance. Thus, moderately and highly invasive species are distinct from less invasive species in terms of ecophysiology in both wetland types. As Phragmites australis and Typha angustifolia displace other plant species in marshes, they will likely influence the carbon- and nitrogen-cycling functions of wetlands, subject to the species' varying tolerances for salinity.

Elaeagnus angustifolia (Russian olive) is an alien tree that is increasingly common in riparian habitats of western North America. This paper reviews the pertinent scientific literature in order to determine the status of E. angustifolia as a riparian invader and to suggest ecological reasons for its success. Elaeagnus angustifolia meets the biogeographic, spread, and impact criteria for invasive species. Ecological characteristics likely enabling its invasiveness include adaptation to the physical environmental conditions that characterize semi-arid riparian habitats, lack of intense pressure from herbivores, and tolerance of the competitive effects of established vegetation. We believe that the success of this species is at least partly due to its ability to take advantage of the reduced levels of physical disturbance that characterize riparian habitats downstream from dams. Control of E. angustifolia is likely to be most promising where natural river flow regimes remain relatively intact.

The ability of coastal wetlands of the Laurentian Great Lakes to reduce pollution from tributaries has not been documented in detail or over multiple seasons. This study developed a surface-water budget for a coastal wetland along Lake Erie and estimated monthly, annual, and storm-related exports of total suspended solids and selected nutrients from the wetland. Water-budget measurements included precipitation, evaporation, surface discharge into the wetland, and net surface discharge into Lake Erie. Water samples collected upstream and downstream and composite dryfall-precipitation samples were analyzed for total suspended solids (TSS), total phosphorus (TP), soluble reactive phosphorus (SRP), nitrate nitrite nitrogen (NO_{2 3}), ammonia nitrogen (NH₃), total Kjeldahl nitrogen (TKN), soluble reactive silica, chloride, and specific conductance. Seasonal and storm-related concentration patterns and a wide variation in monthly, seasonal, and annual loads from the tributary into the wetland were typical of streams draining the western Lake Erie basin. All substances reached higher maximum concentrations upstream than downstream; however, median monthly time-weighted mean concentrations of TP, TSS, NH₃, and TKN were higher downstream. Concentrations without discharge data were inadequate to estimate removal rates. Annual loads of TSS, NH₃, and TKN increased during passage through the wetland, whereas those of TP, SRP, NO_{2 3}, and soluble reactive silica decreased. During storm runoff events, various proportions of TP, SRP, TSS, NO_{2 3}, and soluble reactive silica were removed, despite brief hydraulic residence times, whereas more NH₃ exited than entered. Wetlands occupying the flooded lower reaches of Great Lakes tributaries collectively are probably important in maintaining and enhancing the water and sediment quality of the lakes. Water levels throughout the Laurentian Great Lakes have decreased in recent years; consequently, wetland areas with standing water and hydraulic residence times have decreased, probably reducing the effectiveness of the wetlands in mitigating pollution.

Annual and seasonal variations in precipitation have been shown to influence the hydrology of nontidal wetlands, including depth to water table. Water-table depth is assessed in wetlands for a variety of reasons, most notably for wetland delineations or determining the success of restoration projects. Many short-term assessment efforts probably occur during periods of abnormal precipitation and, as such, may not provide a thorough understanding of wetland hydrology. I have been evaluating water-table dynamics of a wetlands complex in western North Carolina for seven years in support of a wetlands restoration project. A series of water-table wells and piezometers were installed to determine the spatial and temporal patterns of the water table and vertical hydraulic gradient (VHG). For over three years, the area was classified as having conditions of moderate to severe drought. The drought lowered the average monthly water table by 26 cm in a mountain fen and 22 cm in the adjacent floodplain. The fen was a constant ground-water recharge area before the drought and a discharge area for three of 12 months during the drought. The drought also impacted a shallow, constant ground-water source to the fen on an adjacent hillslope. The impacts of the drought were greater during the active growing season, presumably due to increased evapotranspiration. The results support the need for long-term hydrologic assessment of wetlands and the need to relate wetland hydrology to annual, seasonal, and monthly precipitation patterns.

Development of lakeshores has occurred at unprecedented levels in recent decades. Changes in the shoreland ecosystem concomitant with this development have been little studied. In this study, we compared the structural and floristic characteristics of vegetation at 97 developed and 85 undeveloped (reference) shoreland sites in northern Wisconsin, USA. Quantitative comparisons of vegetation structural characteristics (percent cover of canopy, subcanopy, and understory vegetation layers; percent of shoreline overhung by trees and shrubs; and amount of coarse woody debris) showed significantly greater complexity and cover at undeveloped versus developed sites. We classified plant communities and described plant species composition along three belt transects parallel to shore (upland, shoreline, and shallow water) using ordination techniques to describe the differences between developed and undeveloped sites, as well as among undeveloped sites. The mean number of plant species and the percent of native species were both greater at undeveloped than at developed sites along all three transects. Undeveloped upland sites could be grouped by plant species composition into three types: Northern Wet Forest (bog species), Northern Mesic Forest, and Northern Xeric Forest. Undeveloped shoreline vegetation was also clustered into three categories: bog species, upland species with an abrupt transition to aquatic species, and wet meadow species. Soil characteristics further distinguished the upland and shoreline categories. No distinct vegetation categories emerged in the shallow water ordination. We recommend that appropriate species for shoreland restoration efforts be selected based on the native plant communities present at the undeveloped sites, their relative location along an upland to shallow water gradient, and, in some cases, soil characteristics.

Constructed wetlands are recognized as a means to improve water quality through nitrogen (N) removal. Water-quality concerns in the N-sensitive Neuse River Estuary, North Carolina, USA, have necessitated enactment of a 30% reduction in nitrogen (N) loading accompanied by an N loading cap. Open Grounds Farm (OGF) is an 18,220-ha row-crop farm located in the lower Neuse River Estuary. In 1999, a wetland was constructed to remove nutrients (N and Phosphorus), sediment, and pathogens in surface water draining from a 971-ha area of OGF. The wetland site is 5.1 ha of alternating segments of emergent marsh and open water. Nitrogen removal from the wetland via denitrification was measured monthly by analysis of dissolved nitrogen, oxygen, and argon in laboratory incubated sediment chambers using a Membrane Inlet Mass Spectrometer (MIMS). Nitrate concentration appeared to be the primary variable controlling denitrification rates. Spatial and temporal variability in rates of denitrification were investigated, including pre- and post- N loading events. Following rainfall, there was a 400% increase in denitrification rates in response to increased inorganic N loading. Nutrient loads entering and leaving the wetland were determined from nutrient analysis (twice monthly), intensive precipitation event sampling, and continuous flow measurements at the entrance and exit of the wetland. Results indicated that the wetland received variable N loading (1–1,720 kg N per month) and had variable N removal via denitrification (8–81 kg N per month). Denitrification was an important mechanism for N removal.

Irrigation practices may have adverse impact on aquatic ecosystems. Quantification of such impacts is possible only if a condition of an aquatic ecosystem is known before the impacts started. This study attempted to simulate the reference hydrologic regimes of three coastal lagoons in southern Sri Lanka, two of which are currently receiving return flows from upstream irrigation scheme. The lagoon that does not receive irrigation drainage flows is considered to be a reference wetland. The simulation of its water volumes and levels was carried out using a daily water-balance model. The model assumed that a lagoon may be described as a reservoir, which is separated from the sea by a sand bar. The simulated water levels in a reference lagoon were then modified to describe water-level fluctuation in the other two lagoons. This modification uses a spatial interpolation approach based on duration curves and incorporates information received from local farmers. The probable changes caused by irrigation drainage flows to two lagoons can be illustrated by duration curves of observed and simulated water levels.

This experiment tested the hypothesis that the movement of water into the soil due to macrophyte transpiration stimulates nitrate removal from wetlands. The short-term impacts of biomass harvesting upon the ability of wetlands to reduce nitrate concentrations were also investigated. Different amounts of biomass were harvested from Typha latifolia specimens to create three treatments of varying transpiration rates. Harvesting and the resulting different rates of transpiration explained between 10 and 38% of the variation in nitrate reduction during the 10-day experiment and had significant effects upon nitrate concentrations. Greater rates of harvesting and lower rates of transpiration resulted in decreased reductions of nitrate in the surface water of the microcosms. During the first four days of the experiment, 70% and 85% rates of aboveground harvesting reduced transpiration by 63% and 91%, respectively. These changes led to respective decreases in nitrate reduction of 16% and 31% compared to unharvested treatments. Differences in nitrate reduction between the treatments were minimal in the later days of the experiment as nitrate concentrations decreased. Results support the hypothesis that water movement due to plant uptake contributes to nitrogen removal and offers a partial explanation for increased nitrogen removal in vegetated wetland treatment systems. Decreased reduction of nitrate with greater harvesting demonstrates potential negative impacts on water quality improvement when using wetlands as bio-energy production systems.

Planting Spartina patens (Salt Meadow Cord Grass) is an integral part of restoring salt marshes along Tampa Bay, Florida, USA. Of the salt marsh species that are planted, S. patens often has the lowest survivorship. State managers have hypothesized that this low survivorship is related to transplant shock and to acidic soil conditions commonly found under dense stands of Casuarina sp. (Australian Pine), an exotic invasive. This study documents planted S. patens health and survivorship over 11 months at a restoration site previously dominated by Casuarina sp. Three plots of 100 plants each were established in varying soil pH, with each plot covering above and below the recommended elevation range for S. patens. Transplant shock occurred within the first thirty days after planting and affected overall survival. Spartina patens survival was not affected by soil pH (p = 0.827) as evidenced by the presence of healthy individuals outside the plots, in soil pH ranging from 4.76 to 8.94. However, there was a sharp decline in plant health when redox potentials fell below −50 mV. Although elevation and redox potential were highly correlated (p < 0.001, R² = 0.736), plant health varied more with elevation (p < 0.001, R² = 0.387) than redox potential (p < 0.001, R² = 0.950), suggesting that elevation, while a good coarse predictor of site suitability, may not always be the best measure. Redox potential should be monitored, in addition to measuring elevation, to avoid planting in highly reduced areas. Furthermore, adjusting the lower limit of the target elevation range to a higher elevation will increase the amount of survivorship.

A major obstacle to assessing functional equivalency of restored or created wetlands is the time needed to develop the functions of natural wetlands. We compared hydrologic, water-quality, and vegetation-composition functions of nine natural coastal plain ponds in the New Jersey Pinelands with those of four small, well-established excavated basins that are at least 50 years old. Our study revealed that well-established (> 50 yr old) excavated ponds achieved a moderate degree of functional equivalency with Pinelands wetlands, representing a range of coastal plain pond characteristics. Based on water-depth-fluctuation patterns and the similarity of most hydrologic indices, including high-water pond area, mean water depth, area of exposed substrate (drawdown), and the presence of a clay lens, the excavated ponds seemed to achieve hydrologic equivalency with the natural reference wetlands. However, steeper bank slopes found at most of the excavated ponds affected nearshore water depths and resulted in the absence of plant zonation that characterizes coastal plain ponds. The water-quality function, represented by pH, specific conductance, and total organic carbon, differed between pond types. The pH and specific conductance of the excavated ponds were higher and total organic carbon concentrations were lower compared with the natural ponds. We attributed these differences to landscape setting, reflected by adjacent vegetation and contrasting plant zonation. Elevated specific conductance values in the natural ponds were likely due to the higher hydrogen ion concentrations. Reduced light transmission due to higher organic carbon concentrations in the natural ponds may have greater ecological importance. However, differences in water-quality functions between the pond types may make excavated ponds more prone to changes in pH if constructed within landscapes with extensive developed or agricultural lands. The excavated ponds met or exceeded most vegetation-composition reference criteria associated with the natural wetlands. Total and herbaceous species richness were greater in the excavated ponds. Most importantly, the excavated ponds supported a native Pinelands species composition, thus preserving regional biodiversity. Because all ponds were acidic and displayed pH values within the range associated with native Pinelands plants, differences in pH may not have been the cause of the greater species richness. Although overall species composition differed between the two pond types, the flora of the created wetlands was similar to that of coastal plain ponds found in other regions and other areas of the Pinelands. The major difference in vegetation composition between ponds was both the lack of distinct vegetation zonation due to steeper slopes and lower patch-type diversity in the excavated ponds. These structural differences can be overcome by constructing ponds with slopes that are comparable to natural ponds. Because the transitional-upland location of the excavated ponds is a more likely location for a mitigation wetland, the effect of landscape setting on water quality may not be as easily remedied as the lack of nearshore slopes.

Responses of wetland abiotic variables and aquatic invertebrate community structure to cattle stocking density, pasture type, and dominant vegetation were evaluated in subtropical pastures. Cattle were stocked at four treatment levels on improved (fertilized) and semi-native (unfertilized) pastures in south-central Florida, USA. Improved pasture wetlands were dominated either by Panicum hemitomon (maidencane) or by a mixture of Polygonum spp. (smartweed) and Juncus effusus; semi-native pasture wetlands were dominated mainly by maidencane. Cattle stocking density had few significant effects on water-column nutrient concentration or invertebrate community structure. However, water-column nutrient concentrations were significantly greater in the wetlands on improved pastures compared to semi-native pastures. Invertebrate richness and diversity were greater in wetlands on semi-native pastures than on improved pastures, despite lower nutrient concentrations in the former. Overall, the cattle stocking treatment had little impact on invertebrate community structure in these systems relative to prior pasture land use. However, vegetation type influenced invertebrate communities and explained some of the differences between pasture types. Semi-native (lower nutrient) wetland pastures dominated by maidencane had significantly greater invertebrate richness and diversity than improved (higher nutrient) wetland pastures dominated by mixed vegetation but showed no difference when compared to improved wetland pastures dominated by maidencane. Chironomids were the dominant invertebrate in wetlands of both pasture types. Correspondence analysis revealed that ostracods and Culicidae larvae might be useful as bioindicators of subtropical wetlands that are experiencing cultural eutrophication.

We investigated the impact of arbuscular mycorrhizae fungi on common cattails (Typha latifolia), a ubiquitous wetland plant species. The mycorrhizal relationship, which involves the exchange of fungal-acquired nutrients and plant-produced carbon, has been shown to elicit a range of physiological and biochemical responses in host plants. Growth, photosynthetic activity, biomass accumulation, and nutrition were compared between seedlings inoculated with viable mycorrhizal fungal spores and control seedlings given a sterilized inoculum. Plants were grown in inundated soils at three levels of phosphorous availability under glasshouse conditions for 11 weeks. The presence of arbuscules and hyphae was confirmed in all inoculated plants with levels of infection reaching 23.1 and 34.1%, respectively. Control plants were taller and had greater above- and below-ground biomass. Photosynthetic rates measured at week 11 of the experiment were significantly higher in mycorrhizal plants than in control plants. Mycorrhizal plants had higher concentrations of N, P, and C in their shoots and higher concentrations of N in their roots. Our results suggest that under greenhouse conditions, the fungus acts to reduce host plant growth despite increased mineral nutrition and photosynthetic activity.

Aquatic invertebrates are important food resources for wintering waterbirds, and prey selection generally is limited by prey size. Aquatic invertebrate communities are influenced by sediments and hydrologic characteristics of wetlands, which were affected by structural marsh management (levees, water-control structures and impoundments; SMM) and salinity on the Gulf Coast Chenier Plain of North America. Based on previous research, we tested general predictions that SMM reduces biomass of infaunal invertebrates and increases that of epifaunal invertebrates and those that tolerate low levels of dissolved oxygen (O₂) and salinity. We also tested the general prediction that invertebrate biomass in freshwater, oligohaline, and mesohaline marshes are similar, except for taxa adapted to specific ranges of salinity. Finally, we investigated relationships among invertebrate biomass and sizes, sediment and hydrologic variables, and marsh types. Accordingly, we measured biomass of common invertebrate by three size classes (63 to 199 μm, 200 to 999 μm, and ≥1000 μm), sediment variables (carbon content, C:N ratio, hardness, particle size, and O₂ penetration), and hydrologic variables (salinity, water depth, temperature, O₂, and turbidity) in ponds of impounded freshwater (IF), oligohaline (IO), mesohaline (IM), and unimpounded mesohaline (UM) marshes during winters 1997–1998 to 1999–2000 on Rockefeller State Wildlife Refuge, near Grand Chenier, Louisiana, USA. As predicted, an a priori multivariate analysis of variance (MANOVA) contrast indicated that biomass of an infaunal class of invertebrates (Nematoda, 63 to 199 μm) was greater in UM marsh ponds than in those of IM marshes, and biomass of an epifaunal class of invertebrates (Ostracoda, 200 to 999 μm) was greater in IM marsh ponds than in those of UM marshes. The observed reduction in Nematoda due to SMM also was consistent with the prediction that SMM reduces invertebrates that do not tolerate low salinity. Furthermore, as predicted, an a priori MANOVA contrast indicated that biomass of a single invertebrate class adapted to low salinity (Oligochaeta, 200 to 999 μm) was greater in ponds of IF marshes than in those of IO and IM marshes. A canonical correspondence analysis indicated that variation in salinity and O₂ penetration best explained differences among sites that maximized biomass of the common invertebrate classes. Salinity was positively correlated with the silt-clay fraction, O₂, and O₂ penetration, and negatively correlated with water depth, sediment hardness, carbon, and C:N. Nematoda, Foraminifera, and Copepoda generally were associated with UM marsh ponds and high salinity, whereas other invertebrate classes were distributed among impounded marsh ponds and associated with lower salinity. Our results suggest that SMM and salinity have relatively small effects on invertebrate prey of wintering waterbirds in marsh ponds because they affect biomass of Nematoda and Oligochaeta, and few waterbirds consume these invertebrates.

Shrub cover was quantified by species for a 1.9-ha shrub carr adjacent to White Clay Lake near Shawano, WI, USA and related to soil properties and sedimentation rates. Principal components analysis of soil characteristics distinguished two distinct groups: alluvial surface soils having organic matter contents less than 30 g/100g and histic surface soils having organic matter contents averaging 56 g/100g. The alluvial surface soils were on slightly elevated natural levees along a relict stream bed that had received 1.3 cm/yr of silty sediments from agricultural runoff. Alluvial surface soils had twice the bulk density and organic P concentrations, nearly three times the reactive P, and 4.5 times the NO₃-N concentrations of histic surface soils. Total shrub cover and shrub overlap was significantly greater on the alluvial surface soils, but there was no difference between the two soil groups in proportion of open space, suggesting that the increased total shrub cover on alluvial surface soils was due to increased shrub layering rather than infilling of canopy gaps. Shrub diversity was greater on the alluvial surface soils: average shrub species richness per 30.5 m line segment was five species on alluvial surface soils as opposed to three species on histic surface soils. Four willow species were strongly associated with the alluvial surface soils and may serve as indicators of sediment deposition: Salix discolor, S. eriocephala, S. interior, and S. lucida. The most common shrub species present, Cornus sericea spp. sericea and Salix petiolaris, were poor indicators of soil conditions within the wetland.

Urban wetlands, despite their imperfections, provide natural and aesthetic landscape diversity in the built environment. We are beginning to understand and document the ecological significance of this diversity and the management challenges presented by the urban context. The cultural significance of urban wetlands has not received similar attention. The research presented in this paper explores the relationship between people and wetlands in local neighborhood settings. We surveyed residents of three urban communities in the Halifax Regional Municipality, Nova Scotia, Canada for their knowledge about and perceptions of a small wetland in each of their respective neighborhoods. Results of the survey show that the study participants are aware of the wetlands in their midst but are not especially observant of or knowledgeable about ‘their’ sites, nor do they visit their wetlands regularly. Yet, despite this apparent disinterest, they readily identify the wetlands as part of their neighborhoods and as assets, especially as natural features and habitat for urban wildlife. The study participants do not consider these neighborhood wetlands nuisance environments or a waste of land. Instead, respondents revealed an appreciation of the aesthetic attributes and habitat value of wetlands in the city and of urban natural spaces.

Using minirhizotrons, fine root dynamics were compared in two Atlantic white-cedar swamps with contrasting hydroperiods (intermittently and persistently flooded) in order to evaluate the effects of flooding regime on fine root depth, abundance, production, and longevity. Despite the higher mean water-table depth in the persistently flooded site, no differences in rooting depth were observed. Root length density, root abundance, and root longevity were generally greater in the persistently flooded site throughout the 439-day study period, although root length production was similar between the two sites. These results suggest that prolonged inundation in Atlantic white-cedar swamps decreases root elongation rates, but due to greater observed root densities, stand-level belowground production remains similar to that of intermittently flooded stands. Significant increases in root mortality were observed in the intermittently flooded site during a period of water-table drawdown, suggesting less than optimal hydrologic conditions at this site.

The age and sequence of peat accumulation were investigated at a calcareous fen in northeastern Illinois, USA. The purpose of this study was to identify the processes that form and sustain marl flats, which are areas of marl or tufa substrate within the fen that contain numerous rare plant species. Geomorphic, stratigraphic, and radiocarbon evidence was used to establish the processes and chronology of peat accumulation and erosion adjacent to each marl flat. The age of the base of the peat deposit varies greatly throughout the fen, ranging from 14,679 calibrated years before present (cal. years BP) to nearly modern, indicating that colonization of the sand and gravel substrate by peat occurred throughout the period from the Late Pleistocene to present. Adjacent to one marl flat, trends in basal peat age and thickness show that peat accumulation has progressed laterally inward from both sides, suggesting that the marl flat has been infilling with peat progressively by accumulation at the margins since at least 5,370 cal. years BP or longer. A second marl flat in the fen is surrounded by older, thick peat of differing ages on either edge and is bounded by fresh scarps, indicating that the marl flat currently is expanding laterally by erosion into the preexisting peat blanket. These two examples suggest a continuously repeating process, where erosion of the accumulated peat blanket forms a marl flat, which is later covered by peat accumulation. Trends in basal peat age elsewhere in the fen suggest that other marl flats may have existed in the past that have been completely infilled with peat. This study suggests that marl flat formation is a natural process that has been occurring for millennia, continuously creating habitat for the rare plant species that occupy marl flats. There is no evidence that the marl flats at this site are indicative of anthropogenic disturbance, so that management options for these areas are limited to maintaining the quality and quantity of ground-water discharge that supports both peat formation and erosion.

Arbuscular mycorrhizae, which are plant root-fungal symbioses, are common associates of vascular plants. Such relationships, however, are thought to be rare in wetland plant roots, although several recent studies suggest that arbuscular mycorrhizae may be important in wetland ecosystems. Our objectives were to determine (1) the level of arbuscular mycorrhizal colonization of plant roots in three freshwater marshes and (2) the effect of restoration status, hydrologic zone, and plant species identity on mycorrhizal colonization. We quantified the percentage of plant roots colonized by mycorrhizal fungi in one reference and two restored freshwater marshes in northern Indiana, USA during summer 1999. Roots were collected from soil cores taken around dominant plant species present in each of three hydrologic zones and then stained for microscopic examination of mycorrhizal colonization. Mycorrhizae were present in each wetland, in all hydrologic zones and in all sampled plants, including Carex and Scirpus species previously thought to be non-mycorrhizal. Both restored and reference wetlands had moderate levels of mycorrhizal colonization, but no clear trends in colonization were seen with hydrologic zone, which has been hypothesized to regulate the formation of mycorrhizae in wetlands. Mycorrhizal colonization levels in the roots of individual species ranged from 3 to 90% and were particularly large in members of the Poaceae (grass) family. Our results suggest that arbuscular mycorrhizae may be widely distributed across plant species and hydrologic zones in both restored and reference freshwater marshes. Thus, future research should examine the functional role of mycorrhizal fungi in freshwater wetlands.

We studied a Great Lakes peatland protected by a barrier dune system to test the hypothesis that changes in the morphology of a barrier beach alter the wetland surface-water and ground-water hydrology such that the plant rooting zone in the wetland interior might be affected. Hydraulic head measured in observation wells located on transects perpendicular to a flow-through channel, uplands, and Lake Ontario were compared to lake-level changes, weather patterns, and the temporal conditions of the barrier beach. Water-table elevations within the wetland complex always remained 0.35 to 0.84 m above Lake Ontario's water level (mean difference = 0.62 m) and did not fluctuate in parallel with changes in the lake's water level. Flooding events occurred when breaches closed and isolated the wetland complex from Lake Ontario; daily average water levels rose between 0.06 m and 0.27 m. When the barrier beach was breached naturally or by human activity, daily average water-table elevations in the wetland receded between 0.16 m and 0.41 m. During the growing season, vertical ground-water-flow directions also changed as a function of changing hydraulics controlled by the barrier beach. Vertical recharge-discharge gradients ranged from −0.2 to 0.1 m·m⁻¹. Water-table elevation and hydraulic head gradients across the study area were controlled primarily by short-term (days to weeks) changes in shoreline geomorphology, whereas seasonal weather patterns and Lake Ontario water-level fluctuations imposed secondary controls on the ground-water-flow regime.

Riparian wetlands have a demonstrated ability to filter and control nitrogen (N) and phosphorus (P) movement into streams and other bodies of water; few studies, however, have examined the roles that individual plant species serve in sequestering N and P pollutants. We evaluated the potential for growth and consequent N and P accumulation by five species of wetland perennials. We planted blocks consisting of 900-cm² plots of each species at 11 sites within a riparian wetland that receives large inputs of agricultural runoff. Plant shoots and roots were collected at the time of peak standing crop to determine net accumulation of biomass, N, and P for one growing season. A portion of the plant shoots was placed in decomposition litterbags in the field to determine biomass, N, and P losses for 60, 120, and 150 days. Of the five species, bur reed (Sparganium americanum) had the greatest aboveground accumulation of N and P but had the lowest belowground accumulation values. In contrast, woolgrass (Scirpus cyperinus) had the lowest aboveground values for N and P accumulation but had the highest belowground value for P. Soft rush (Juncus effusus) and reed canary grass (Phalaris arundinacea) showed high values for both aboveground and belowground N and P accumulation, while blue joint grass (Calamagrostis canadensis) showed low values for aboveground N and P. The five species also showed wide variations in the retention of N and P in decomposing shoots. Juncus effusus had the highest percentages of N and P remaining in litter after five months (87% N and 69% P), while P. arundinacea retained only 28% N and 18% P. Sparganium americanum had high retention rate for N in litter (74% N) but showed low P retention values (35%). Scirpus cyperinus and C. canadensis also showed high retention rates of litter N but lower values for P retention. Our study suggests that species show differential accumulation and release of N and P and may influence the overall potential of a wetland to retain agricultural nutrients.

Hydroperiod is considered the primary determinant of plant species distribution in temperate floodplain forests, but most studies have focused on alluvial (sediment-laden) river systems. Few studies have evaluated plant community relationships in blackwater river systems of the South Atlantic Coastal Plain of North America. In this study, we characterized the soils, hydroperiod, and vegetation communities and evaluated relationships between the physical and chemical environment and plant community structure on the floodplain of the Coosawhatchie River, a blackwater river in South Carolina, USA. The soils were similar to previous descriptions of blackwater floodplain soils but had greater soil N and P availability, substantially greater clay content, and lower soil silt content than was previously reported for other blackwater river floodplains. Results of a cluster analysis showed there were five forest communities on the site, and both short-term (4 years) and long-term (50 years) flooding records documented a flooding gradient: water tupelo community > swamp tupelo > laurel oak = overcup oak > mixed oak. The long-term hydrologic record showed that the floodplain has flooded less frequently from 1994 to present than in previous decades. Detrended correspondence analysis of environmental and relative basal area values showed that 27% of the variation in overstory community structure could be explained by the first two axes; however, fitting the species distributions to the DCA axes using Gaussian regression explained 67% of the variation. Axes were correlated with elevation (flooding intensity) and soil characteristics related to rooting volume and cation nutrient availability. Our study suggests that flooding is the major factor affecting community structure, but soil characteristics also may be factors in community structure in blackwater systems.

Conservation efforts require detailed knowledge of a species' habitat use and movements about the landscape. We radio-tracked sympatric congeners, the Copperbelly Water Snake (Nerodia erythrogaster neglecta) and the Northern Water Snake (Nerodia sipedon sipedon) in northwestern Ohio and southern Michigan, USA, to investigate differences in the use of wetland and upland habitats between species. Nerodia erythrogaster neglecta used twice as many wetlands (4.1 ± 0.4) as N. s. sipedon (2.1 ± 0.3), moved between these wetlands three times more often (9.1 ± 1.9 times) than N. s. sipedon (2.8 ± 1.0 times), and moved to small wetlands seven times more often (3.6 ± 0.7 times) than N. s. sipedon (0.5 ± 0.3 times). Nearly 30% of N. e. neglecta locations were in uplands, sometimes over 100 m from the nearest wetland. Less than 3% of N. s. sipedon locations were in upland habitats, and all locations were < 30 m from wetlands. We simulated the impact of small wetland loss and demonstrated that N. e. neglecta would need to move longer than normal distances when traveling between wetlands after small wetlands are lost, while N. s. sipedon would not. The northernmost populations of N. e. neglecta are listed as federally threatened and state endangered in Ohio, Michigan, and Indiana; N. s. sipedon remains abundant in this region. Historic and current wetland losses in the midwestern United States may have severely impacted N. e. neglecta populations due to this species' high vagility and use of numerous wetlands. Protection and restoration of wetland landscapes are critical for the long-term persistence of many wetland-associated species, including N. e. neglecta.

The Hole-in-the-Donut is a 4000-ha region of former farmlands within Everglades National Park that is dominated by a monoculture of the non-indigenous pest plant Schinus terebinthifolius (Brazilian pepper). Prior to extensive farming in the region, the area consisted of short hydroperiod graminoid wetlands and mesic pine savannah. Rock plowing in preparation of these lands for farming created an artificial soil layer that broke up the limestone substrate, mixed and aerated the native marl soil layer with the broken limestone, and elevated the surface slightly. Farming practices also included the use of chemical fertilizers and pesticides. The modified soil substrate quickly became dominated by S. terebinthifolius when farming ceased in 1975, despite efforts to control its establishment, such as prescribed fire, herbicide treatment, and mowing. Preliminary evidence indicated that soil removal would prevent re-invasion by S. terebinthifolius and could lead to colonization by native wetlands plants. Two trials, a partial soil removal (PSR) and a compete soil removal (CSR), were performed on a pilot test site beginning in 1989 to determine whether all or only a portion of this modified soil substrate needed to be removed to attain desired results. Removal of rock-plowed surface material lowered elevation in both treatments. While the PSR treatment did show an increase in the number and coverage of hydrophytes for a few years, it did not prohibit re-colonization and re-establishment of a canopy of S. terebinthifolius, and by 1996, the site was again dominated by a monoculture of S. terebinthifolius. By contrast, the CSR treatment showed rapid colonization by hydrophytes and no successful re-colonization by S. terebinthifolius. Lowering elevations by 15 to 45 cm allowed for longer periods of flooding and rapid colonization by hydrophytes on both sites. After the sites were cleared, the average difference in elevation between the two treatment areas was less than a tenth of a meter, but this resulted in a slightly shorter hydroperiod on the PSR site. The small amount of residual rock-plowed soil with high levels of nutrients, along with its slightly shorter hydroperiod on the PSR site, appear to have contributed significantly to the success of S. terebinthifolius in re-colonizing this treatment area.

Although amphibians are increasingly being used to assess ecosystem function of compensatory wetlands, there are almost no long-term studies of responses to ecological restoration. Consequently, much uncertainty exists about the appropriate timeframes and best criteria for evaluating responses to wetland restoration. We studied aspects of pond colonization and long-term community dynamics in ponds created at a mitigation site in western North Carolina. We examined whether landscape variables influenced the initial colonization of 22 constructed ponds and conducted a long-term study of changes in species richness and community composition in ten constructed and ten reference ponds over seven breeding seasons. During the first year of pond filling, species richness and the number of egg masses of the wood frog (Rana sylvatica) and spotted salamander (Ambystoma maculatum) were positively correlated with pond size, depth, and hydroperiod but independent of distance to the nearest forest, paved road, or source pond. The ten constructed ponds in the long-term study first filled in 1996 and were larger, deeper, warmer, more oxygen-rich, and of longer seasonal hydroperiod than reference ponds. Seven species bred in the constructed ponds during the first year of filling, and species richness reached equilibrium within two years of initial pond filling. Most species colonized constructed ponds rapidly, but frequency of use by eastern newts (Notophthalmus viridescens) increased slowly over five years. Constructed ponds supported significantly more species than reference ponds, and the annual turnover rate of breeding populations was approximately 25% for both pond types. Our data suggest that post-restoration monitoring for 2–3 years may be sufficient to characterize species and communities that will utilize ponds for the first decade or so after pond creation.

The common reed, Phragmites australis, is a common feature in wetlands across North America. Recent studies have suggested that the widespread invasions of this species may be due to the introduction of a non-native strain from EurAsia. Since native populations persist in many areas where introduced populations are also found, a method for distinguishing population types is needed to facilitate management of the species. A restriction fragment length polymorphism (RFLP) assay was developed to distinguish native, non-native, and Gulf Coast type populations of Phragmites from each other. Two amplified non-coding chloroplast DNA regions are each cut with one restriction enzyme, allowing the distinction of native, non-native and Gulf Coast haplotypes from each other. When used together, these cut sites provide a low cost, rapid way of determining the origin of Phragmites populations.