Accelerating the reestablishment of a mature, biotic community following a disturbance is a common goal of restoration ecology. In this study, we describe the relative successional status of a recently disturbed riparian seed bank when compared with less recently disturbed and undisturbed systems, and the short-term effects of restoration on seed bank development within the recently disturbed system. The study location, the U.S. Department of Energy's Savannah River Site in South Carolina, provides a unique opportunity to investigate the development of wetland seed banks following a severe disturbance, in this case the release of elevated temperature and flow effluent from nuclear reactor operations. To assess the recovery of wetland seed banks over time, we compared seed banks of naturally recovering riparian corridor and swamp delta sites of two different ages since disturbance (nine years and 30 years) with undisturbed forested corridor and swamp sites. To assess the potential effects of restoration efforts (site preparation and planting of seedlings) on seed bank development, we compared seed banks of naturally recovering (unplanted) and planted riparian corridor and swamp delta sites in the more recently disturbed system. We expected total germinants and species richness to be highest in the recently disturbed sites and decline as wetland systems matured. Within recently disturbed sites, we expected planted sites to have higher abundance and richness than unplanted sites. We also expected a greater abundance of woody species in the undisturbed forested sites. The number of germinants differed among the sites, ranging from 748 individuals per m² in the undisturbed swamp area to 10,322 individuals per m² in the recently disturbed planted swamp delta. When corridor and delta sites within a stream system were combined, the mean number of germinants was greater in the recently disturbed system, intermediate in the 30-year (mid-successional) system, and lowest in the undisturbed system. Seed banks from the recently disturbed and mid-successional sites were more similar in composition than they were to the undisturbed systems. Across all stream systems, riparian corridors had greater mean species richness than swamp deltas, though differences in seed bank abundances were not significant. Sedges and rushes were the predominant life forms in the recently disturbed and mid-successional sites, while undisturbed sites had a greater proportion of herbs and woody seedlings. In addition, there were more germinants from planted sites than from unplanted sites. The dominance by early successional species at recently disturbed planted sites may be an unintended consequence of site preparation treatments, and such potential effects should be recognized and weighed during the development of restoration plans.

Spartina alterniflora is unique among salt marsh macrophytes in its synthesis of dimethylsulfoniopropionate (DMSP). One potential degradation product of DMSP is dimethylsulfoxide (DMSO). The concentrations of DMSP and DMSO were determined for S. alterniflora plants collected from Mobile Bay, Alabama. Although the distribution of DMSO within healthy S. alterniflora tissues mirrored somewhat that of DMSP, with the highest concentrations found in leaf tissue followed by stem and root tissue, the DMSO/DMSP ratio in root tissue was more than twice that in leaf or stem tissue. This is likely the result of a higher rate of DMS(P) oxidation in roots. It has been proposed that DMSP functions as an antioxidant in certain marine phytoplankton, and a similar function may be operational in S. alterniflora. Enhanced oxidative stress in the S. alterniflora root zone may help explain the high DMSO/DMSP ratio. In support of this idea was the finding that the DMSO/DMSP ratio was higher in tissues presumably experiencing increased oxidative stress such as yellowing S. alterniflora leaves and senescing segments of individual leaves compared to healthy tissue. The occurrence of DMSO in tissues of S. alterniflora is consistent with DMS(P) functioning as an antioxidant in this plant. Higher DMSO/DMSP ratios in stressed leaves further supports that role. However, specific roles for DMSP, DMS, or DMSO in oxidative stress protection in S. alterniflora remain to be demonstrated.

An experimental water treatment plant was established to verify the effectiveness of constructed wetlands to improve water quality in the Venice Lagoon watershed. The wetland comprised three different subsystems, ranging from a riparian swamp to a marsh ecosystem. As a first step, monitoring was conducted over three years to evaluate the efficacy and efficiency of the system. Here, we report an analysis of the water budget resulting from routinely collected hydraulic and meteorological data. We used independent estimates of the water-budget terms, rather than budgetary residual estimation, because we wanted to estimate the water-budget error. Surface-water inflow, surface-water outflow, and direct precipitation were measured. Daily potential evapotranspiration values were estimated using the FAO Penman Monteith equation; runoff was estimated using the USDA Soil Conservation Service curve number model; indirect precipitation that flows toward the wetland via subsurface flow was estimated from the soils field capacity; and seepage was estimated using Darcy's law. The objectives of the research were to establish the best way to develop a water budget useful for application and design purposes, to determine the term that most influences the water-budget error, and to perform a sensitivity analysis on the parameters affecting this term. Surface flow dominated the wetland system, precipitation and evapotranspiration contributed about 10% to the water budget, and changes in water storage and the seepage flow contributed less than 5% to the water budget. The seepage flow term had the highest uncertainty, and the frequency of ground-water level measurements had the greatest impact on the water-budget error (ranging from 10.0%–28.6%). Therefore, in a free-water surface wetland with a shallow ground-water system, the main effort in field measurement should be to ensure a measurement frequency of less than five days.

Salt marshes created on dredge spoil were compared to natural marshes to evaluate the capacity of created marshes to perform carbon cycle functions. Several carbon cycle attributes were measured in eight created Spartina alterniflora Loisel salt marshes that ranged from one to 28 years, each paired with a nearby mature natural reference marsh. The attributes measured included gross primary production, respiration, net ecosystem exchange, potential microbial respiration (CH₄ and CO₂), and aboveground biomass. In situ exchange rates of CO₂ and plant biomass in created marshes met or exceeded those of reference marshes in three to four years. There was some evidence that ecosystem gas exchange in created marshes developed slightly faster than aboveground biomass production. Soil carbon mineralization per gram carbon was generally higher in the created marshes than reference marshes, suggesting higher carbon quality and/or nutrient availability in the created marshes. However, carbon mineralization rates per gram soil were relatively low in the created marshes due to lower soil organic matter content. With proper construction, we suggest most major carbon fluxes can be established in created salt marshes in less than five years.

Since the 1970s, southwestern Georgia has seen significant decreases in annual stream flows and changes in seasonal rainfall patterns (i.e., slightly wetter winters and drier springs) that have implications for leaf breakdown processes in wetlands. In four separate study years (1999–2002), we examined leaf breakdown processes in two types of forested wetlands, floodplain and depressional. Using a reciprocal transfer design, litter bags containing black gum (Nyssa sylvatica biflora) and water tupelo (Nyssa aquatica) were placed in three wetlands of each type. We predicted open wetlands (floodplain) would have faster breakdown rates than isolated wetlands (depressional), and water tupelo leaves acquired from high-nutrient wetlands (floodplain) would be less refractory and decompose faster than black gum leaves obtained from low-nutrient wetlands (depressional). There was no consistent pattern of one wetland type having faster breakdown rates than the other. Breakdown of water tupelo (k  =  −0.57 to −1.77 yr⁻¹) was faster than black gum (k  =  −0.53 to −1.31 yr⁻¹) in three out of eight instances (i.e., same wetland type and year); otherwise, no difference was detected between species. Results from the drier years (1999, 2000, and 2001) suggest that litter species was more important than wetland type in determining P levels in litter and in some instances N concentrations, but in the wetter year (2002) N and P patterns in litter differed by wetland type. This multiyear study allowed us to conclude that in drought years, moisture levels primarily influenced breakdown of organic matter, but in years with prolonged flooding, faster breakdown rates occurred in the wetland type and litter species with the higher nutrient levels. A 1.4 to 3-fold difference in breakdown rates among study years (for the same wetland type and litter) suggest that caution should be used in making conclusions based on a single decomposition study.

The distribution of wetland breeding amphibians may be influenced by multiple habitat variables interacting at various scales. We applied a multi-scaled modeling approach to relate the presence and absence of carpenter frogs (Lithobates virgatipes), a species of conservation concern in Maryland, to several wetland and landscape characteristics. We also investigated relationships between wetland habitat quality and adjacent landscape composition using correlation analysis and summarized those relationships in a hierarchical path model. Breeding call surveys were conducted at 40 wetland sites to determine the presence of calling male carpenter frogs. We collected data on aquatic and terrestrial habitat using both on-site measurements and geographic information system analyses. Logistic regression modeling revealed that wetlands occupied by carpenter frogs were significantly more acidic, exhibited intermediate hydroperiods, and had higher proportions of surrounding forest cover than did sites unoccupied by carpenter frogs. Path analysis revealed forest cover exhibited a negative correlation with wetland pH and hydroperiod. Our study corroborates a growing body of research that suggests the distributions of many amphibians are related to forest cover adjacent to wetland habitat and provides evidence on the importance of forest cover for maintaining wetland habitat quality.

Height-biomass regressions were used to produce non-destructive aboveground biomass assessments for Spartina foliosa. We performed a statistical analysis of these regression models using data collected in Punta Banda Estuary, Baja California, Mexico. We found these models to be inconsistent with available data, on the basis of lack of homoscedasticity and randomness of residuals. The allometric scaling of aboveground plant biomass and corresponding leaf area was tested as a basis for alternative biomass assessment. We show that regression models using leaf area result in simpler, more reliable non-destructive estimations of Spartina foliosa biomass.

Canyon riparian zone vegetation is vulnerable to effects of upstream river regulation. We studied box elder (Acer negundo) dominated canyon riparian forests intensively on the Green and Yampa rivers in Dinosaur National Monument, Colorado, and extensively in four other major rivers of the upper Colorado River Basin to determine the effects of river regulation on riparian tree establishment patterns. We: 1) aged individuals to determine if establishment was correlated with high annual peak flows, 2) mapped cohorts to determine if the areal extent of post-regulation cohorts was reduced on regulated compared to unregulated river reaches, and 3) measured the floodplain position of cohorts in regulated and unregulated rivers to determine if establishment was confined to lower landscape positions under regulated flow regimes. Box elder establishment was highly correlated with annual peak flows, with most recruitment occurring during years with unusually high peak flows. In regulated river reaches recruitment was facilitated by annual peak flows that were below average under a natural flow regime but were unusually high under the post-dam flow regime. The areal extent of post-regulation box elder cohorts was reduced on the regulated river compared to pre-regulation cohorts on all rivers, and recent cohorts on an unregulated river. Post-regulation cohorts on regulated rivers established at lower landscape positions than cohorts on unregulated rivers, resulting in inset floodplain forests on regulated rivers. The reduction in establishment height above the river was directly proportional to the magnitude of post-regulation peak flow reduction. Controlled high magnitude flood releases would facilitate forest regeneration across the full extent of historic forests, and peak flows that would mimic a lower magnitude natural hydrograph would facilitate establishment in the inset floodplain. In an era of increasing consumption of shrinking water supplies, opportunities for high magnitude reservoir releases are likely to diminish, increasing the need for active management of riparian forest ecosystems.

An intact hydrologic regime and the presence of peat forming vegetation are critical for the persistence of fen wetlands. Fen restoration projects often focus on reestablishing water tables near the soil surface, with little effort directed toward identifying historic hydrologic regimes, hydrologic modifications, and the sources of degradation. We used inconsistencies in the modern hydrologic regime and historic hydrologic indicators present in the soil seedbank, vegetation, and organic soil composition to identify areas of Drakesbad Meadow, a mountain fen in Lassen Volcanic National Park, California, that had been degraded. A network of ground-water monitoring wells and piezometers were used to identify the hydrologic regime of the 4.7-ha site. The presence of thick organic soils in sites with deep late summer water tables, inconsistencies between species present in the seedbank and the existing vegetation, and the presence of dry meadow species such as Poa pratensis and Hordeum brachyantherum in areas with organic soils were used to determine that 2.4 ha of the site was degraded. A drainage ditch within the fen and diversions of the fen's water supply caused by a road outside of the fen were identified as the source of hydrologic modification and degradation. These were restored by blocking the flow of water in the main drainage ditch and by installing a series of channels to allow water to cross the road. Reconnecting flow beneath the road resulted in raising the summer water table from 80 cm below the soil surface to less than 10 cm in areas downslope of the road. The addition of five sheet-metal dams perpendicular to flow in the main drainage ditch resulted in raising the water table to within 10 to 20 cm of the soil surface in areas adjacent to and down gradient of the ditch. Before restoration, average late August water table levels across the entire site were 30 cm below the soil surface, while average post-restoration water table levels were 19 cm below the soil surface. One year following hydrologic restoration, the percent canopy cover of species indicative of uplands and wet meadows, but not fens including Deschampsia cespitosa, Hordeum brachyantherum, and Poa pratensis decreased compared with pre-restoration years, while the cover of the peat-forming species Carex utriculata, Scirpus microcarpus, and Carex simulata increased. It is clear from our study that fens in this region will not persist under drought-like conditions created by water diversions, yet well-designed restoration projects can be used to restore modified hydrologic regimes and peat-forming vegetation necessary for the persistence of fen wetlands.

Horseshoe Lake, Alexander County, Illinois, is a shallow floodplain lake that lies at the northern range boundary of Taxodium distichum var. distichum (L.) L.C. Rich (bald cypress) in the Mississippi River Valley. About 35% of the lake surface is occupied by a flooded forest of Taxodium distichum and Nyssa aquatica L. (water tupelo). Pollen in two sediment cores was examined to determine the time of arrival of the forest at the site. Taxodium and Nyssa pollen increased in sediment deposited in 1850. The Modern Analogue Technique (MAT) showed that samples dating from before the arrival of Taxodium were most similar to sites in a variety of locations with high Quercus (oak) and Carya (hickory) and low Pinus (pine) percentages without Taxodium. For sediment deposited after the increase in Taxodium, the most similar modern analogues came from Taxodium/Nyssa swamps in the lower Mississippi River Valley and Virginia. Ring analysis of extant trees suggested an increase in reproduction and growth after 1850. The MAT results were consistent with the hypothesis that the Taxodium/Nyssa forest first colonized the lake around 1850 when American farmers developed the upland loess soils of the watershed for agriculture. We suggest that agricultural development on the uplands surrounding the lake encouraged the growth of the Taxodium/Nyssa forest by increasing sedimentation rate and producing large shallow areas of seasonally flooded eroded material.

Headwater streams and wetlands with a combination of surface and subsurface flows are common features of many upland-forested watersheds. Unlike headwater stream reaches with continuous surface flow, the hydrology and ecology of subsurface stream reaches are poorly studied and not factored into existing wetland legislation. We assessed subsurface habitats and associated biota in a 435-m reach of a first-order, intermittent stream draining a riparian zone dominated by eastern hemlock (Tsuga canadensis) in north central Massachusetts. Stream flow was found only in subsurface flowpaths beneath large boulders and surface root mats over approximately 70% of the total stream length at summer base flow. Temperature, specific conductivity, dissolved oxygen, and dissolved organic carbon concentrations of subsurface water were similar to surface water. Macroinvertebrates were found in subsurface habitats but at a lower abundance and richness per unit area compared to surface habitats. Collectors such as Chironomidae, Polycentropodidae, and Ephemerellidae were generally the most abundant families in both surface and subsurface habitats. Our findings indicate that in some glaciated watersheds, intermittent streams with no visual evidence of surface flow may contain subsurface flowpaths with water chemistry and biota comparable to coupled perennial surface flow reaches. The prevalence and importance of subsurface habitats in some headwater streams may warrant review or revision of existing state and local regulatory definitions of intermittent and headwater streams.

Nutrient patterns in wetlands are usually studied at a single sampling station and not for more than two or three hydrological years. This makes environmental assessment difficult, particularly when spatial heterogeneity and wetland responses depend upon water availability, as often occurs in Mediterranean wetlands. Furthermore, the spatial scale of environmental control of wetland dynamics is usually hypothesized to change as a result of water connectedness, so the higher the rate of water renewal, the larger the spatial scale of environmental control. To test this idea, we carried out a study of monthly nutrient loadings, organic carbon, total nitrogen, and phosphorus in a Spanish hypertrophic floodplain (Tablas de Daimiel National Park) for six years at three sites to ascertain the significance of both the spatial heterogeneity and the long-term responses of nutrient patterns to water availability. Our study demonstrated that strong site effects prevailed on nutrient chemistry in this wetland, irrespective of the degree of wetland connectivity, since there were very few significant correlations among different sites for a single nutrient and no significant correlations with loadings. Causes for this behavior might be that water inputs to this Mediterranean wetland were highly variable and leveling ecological effects were dampened by site processes. Spatially, an increasing gradient of total organic carbon and nitrogen occurred toward the outlet, but total phosphorus peaked in the middle of the wetland. Such a decoupling was also shown by PCA analysis where three different factors explained 69% of overall variability of nutrient patterns: flooding, both organic carbon and total nitrogen content, and total phosphorus. No temporal trend in nutrient content was observed. No simultaneous seasonal patterns were obvious in nutrient data from the same site or for the same nutrient at different sites. Periodicity analyses did not show overlapping of annual rhythms. That lack of patterns could be evidence of the major importance of site processes. This wetland behaved as a sink for nutrients, a fact also suggested by the increasing carbon and phosphorus content in sediments of all sites over time. Sediment nitrogen dynamics, however, might experience differential among-site processes resulting in no trend in accumulation in some areas. These results challenge current views on the spatial scale of environmental control on wetland performance and suggest that the role of water availability in ecological connectivity may be more complex than previously suspected.

The free surface flow Integrated Constructed Wetlands (ICW) concept explicitly combines the objectives of cleansing and managing water flow from farmyards with that of integrating the wetland infrastructure into the landscape and enhancing its biological diversity. This leads to system robustness and sustainability. Hydraulic dissipation, vegetation interception, and evapotranspiration create an additional freeboard at the outlet of each wetland segment and at the point of discharge, thus enhancing hydraulic residence time and cleansing capacity during hydraulic fluxes. The principal design criteria leading to adequate effluent water quality (i.e., molybdate reactive phosphorus less than 1 mg/l) from ICW are that the wetland area needs to be sized by a factor of at least 1.3 times the farmyard area and the aspect ratio for the individual wetland segments (i.e., approximately four cells) needs to be less than 1∶2.2 (width to length). Within a year of ICW commissioning, approximately 75% of farmyard runoff was intercepted, leading to improvements in the receiving surface waters of the catchment. Most of the recorded phosphate concentrations after ICW treatment agreed with the Irish Urban Wastewater Treatment Regulation 2001, which can be used as a benchmark to assess ICW treatment performance and which is usually applied unofficially to ICW even if it may appear to be too stringent. A case study of 13 ICW systems suggested that phosphorus exported from an ICW system was similar to the typical background concentrations of phosphorus export rates from land to water.

A low-lying coastal harvested bog in New Brunswick was inundated by a storm surge in January 2000 and commercially abandoned due to saltwater contamination. This study examines the hydrological processes controlling the seasonal and annual variability of salinity, and its long-term persistence. In the summer period there were two distinct hydrological zones characterized by differences in salinity, elevation, compressibility, soil moisture content, and water-table position. Low-lying sites had higher and more stable surface salinity concentrations (mean 5.7‰, coefficient of variation 0.57) than slightly elevated sites (mean 2.9‰, coefficient of variation 1.13) that experienced more evaporative enrichment. Salts permeated the peat column to a depth of at least 95 cm, with peak salinity occurring 35–75 cm below the surface. A persistent downward hydraulic gradient also indicated downward advective transport of salts, suggesting that over the long term salts will be leached out of the system.

The coastal plain ponds that occur within glacial deposits in the northeastern U.S. experience annual and inter-annual water level fluctuations. Periodic inundation and drying of coastal plain pond shorelines has led to the development of pondshore vegetation communities that are unusually diverse and restricted in distribution. Because water level fluctuations are the primary abiotic control on plant community composition and dynamics, ground-water extraction for municipal supply has the potential to alter pond hydroperiod and plant community structure. We assessed the influence of ground-water pumping on pond levels at Mary Dunn Pond in the Hyannis Ponds Complex in Barnstable, Massachusetts. Short-term well pumping tests, seepage rate measurements, and measurements of surface-water and ground-water temperatures during pumping tests provided unequivocal evidence of an intimate surface-water/ground-water connection. A regression model that related pond levels to pumping and natural background variations in water levels from 1976–2003 indicated that pumping affected water levels in all seasons and that the drawdown from high intensity pumping during 1983–91 persisted for more than one year. The model also indicated that pumping truncated ecologically significant multi-year periods of high water. Pumping shifted the zone of pond-level fluctuations to lower elevations of the Mary Dunn Pond shore and into more organic-rich soils potentially diminishing plant community diversity over the long term. The current rates of pumping, instituted in 1992 after a severe drawdown, more closely approximated the natural hydrologic regime. Planning agencies and water suppliers should consider the ecological effects of ground-water withdrawals in water supply planning and during management of existing wellfields in similar hydrogeologic settings.

Populus spp. (cottonwood) and Salix spp. (willow), the dominant overstory trees in many western riparian forests, are disturbance-adapted species with short seed dispersal periods. Changes to flood cycles often lead to a decrease in recruitment success and survival of these species, and may increase the recruitment success of Tamarix spp. (saltcedar), an introduced riparian tree species that has a longer seed dispersal period. This investigation compared Populus, Salix, and Tamarix stem density in 63 stands on unregulated and regulated reaches of the Verde River. Populus and Salix stem density were not different between the unregulated and regulated reaches in sapling (1–10 year) stands. However, Populus stems showed a trend towards higher density in mature stands (11–40 year) in the unregulated reach, and Populus density was significantly higher in old-growth (41 year) stands in the unregulated reach. Tamarix stem density was higher in the regulated reach for the sapling class (4.75 ± 1.83 stems/m² versus 0.03 ± 0.03 stems/m²). Analysis of flow conditions during a recent recruitment year (1995) suggests that water release patterns in the regulated reach created favorable conditions for Tamarix. Results from this study suggest that where major flooding still occurs in regulated reaches, or where managed flooding is an option, recruitment of Populus and Salix is possible at similar levels to unregulated reaches. However, careful attention to later season water releases may be important in managing Tamarix recruitment opportunities.

Baltic coastal meadows are among the most threatened habitats in Europe, with most residual habitat being in Estonia and Sweden. We quantitatively related the changes in this habitat type in Estonia to the history of a key inhabitant — the natterjack toad (Bufo calamita Laur.). Between the 1930s and 2000s, 67% of 52 local populations of the toad disappeared; in coastal meadows, the decline was 91%. Since the 1980s, coastal grasslands have lost their value as the main habitat for the species, and occupation of secondary habitats has not balanced the disappearance of primary habitat. According to aerial photographs from 1950–51, 1970–71, and 1996–2000, 60%–83% of the coastal meadow habitats in Estonia were lost by 2000, and the toad became extinct in more than 80% of its historical habitat. The survival of local populations was related to the sizes of managed meadows and sandy areas — larger initial areas were related to better survival, probably due to larger population size. Extinction rates exceeded habitat loss rates during advanced stages of habitat loss after 1970, probably due to the additive effects of habitat fragmentation and the disappearance of critical habitat components. Hence, habitat restoration for natterjack toads should focus on large meadow areas, and should be initiated prior to advance habitat loss. Currently, however, meadow populations of the toad in Estonia are unlikely to persist without artificial re-establishment of populations.

Organic matter decomposition is an important ecological function in tidal flat ecosystems, and extracellular hydrolytic enzyme activities can be used as indices of this process. In this study, the spatial and temporal variations of enzyme activities were determined to establish easily measured variables that could be used to assess wetland functions. Seven sampling sites belonging to the hydrogeomorphic subclasses estuary, foreshore, and lagoon were selected in the intertidal zone of the Obitsu River Delta and the Banzu Tidal Flat in Tokyo Bay, Japan. Ten field surveys were conducted between June 2001 and April 2003. In each survey triplicate sediment samples were collected from each sampling site. For each sample, fluoresceindiacetate hydrolysis (FDH), β-glucosidase (GLU), and β-acetylglucosaminidase (AGA) activities were measured. Among the 210 samples, the means and standard deviations were 0.018 ± 0.011 unit g⁻¹ h⁻¹ for FDH, 0.074 ± 0.043 mmol kg⁻¹ h⁻¹ for GLU, and 0.043 ± 0.041 mmol kg⁻¹ h⁻¹ for AGA. According to analysis of variance, sampling time, site location, and their interaction significantly influenced FDH activity. Both the sampling time and sampling location affected GLU and AGA activities, although no significant interaction was found. GLU and AGA activities were higher in the estuary sites than in the foreshore sites and the lagoon site. GLU and AGA activities differed among the estuary sites, although there were no significant differences in GLU and AGA activities among the foreshore beach sites. We recorded significant temporal changes of GLU and AGA activities, and seasonal changes differed across the three years of the study.