Hundreds of wetlands comprising thousands of hectares have been restored in the Midwestern United States. In nearly all cases, restoration consisted of simply restoring wetland hydrology. For this reason, the success of these restorations relies on natural colonization. We compared the structure and composition of the vegetation in two types of wetlands: 10 natural wetlands and 17 five-to-seven-year-old restored wetlands. The overall vegetative composition of restored wetlands was different from that of natural wetlands. Restored wetland flora was formed from a subset of species found in natural wetlands. The species restricted to natural wetlands tended to be native perennials and were evenly represented along the elevational gradient. The few species that were restricted to restored wetlands were largely mudflat annuals whose presence is more indicative of the presence of more unvegetated habitat in restored wetlands than of the presence of a distinctive restored wetlands flora. In addition, restored wetlands had lower vegetative cover and species richness than natural wetlands. Both wetland types had similar numbers of exotic species at the whole wetland (4.4 species per wetland) and quadrat scale (1.5 species m²), and dominance of exotics increased with elevation. The lower species richness, greater compositional variability, and lack of a distinctive flora support the hypothesis that dispersal limitation is the primary cause of the differences between the vegetation in restored and natural wetlands.

A number of studies have noted the occurrence of intermittent surface-water connections between depressional wetlands in general and prairie potholes in particular. Yet, the ecological implications of such connections remain largely unexplored. In 1995, we observed spillage into and out of a North Dakota wetland during two field visits. Between May 3 and May 26, there was a positive relationship between specific conductance and water level at this site, suggesting an external source of dissolved ions. We estimated that specific conductance may have increased at the site by as much as 614 μS cm⁻¹ due to spillage from the upslope wetland. Based on a spatial analysis that compared National Wetlands Inventory maps with 1996 color infrared imagery, we estimated that 28% of the area's wetlands had a temporary surface water connection to at least one other wetland at that time, including one complex of 14 interconnected wetlands. These results indicate that the connectivity observed in 1995 was not confined to the two wetlands nor to that single year. The degree of connectivity we observed would be expected to occur during the wetter portions of the region's 20-year wet-dry cycle. We hypothesize that intermittent surface-water connections between wetlands occur throughout the prairie pothole region. Given patterns in relief and precipitation, these connections most likely would have occurred in the eastern portion of the prairie pothole region. However, wetland drainage may have altered historical patterns. The implication of these spatial and temporal trends is that surface-water connections between depressional wetlands should be viewed as a probability event that has some distribution over time and space. We refer to connections that are impermanent, temporally discontinuous, or sporadic as temporal connectivity. The most intriguing feature of these temporary connections may be that they could affect biodiversity or population dynamics through transport of individuals or reproductive bodies. Research is needed to determine whether these connections actually cause these biological effects and to characterize the distribution and effects of this phenomenon.

Intensive agricultural activities near prairie wetlands may result in excessive sediment loads, which may bury seed and invertebrate egg banks that are important for maintenance and cycling of biotic communities during wet/dry cycles. We evaluated effects of sediment burial on emergence of plants and invertebrates from seed and invertebrate egg banks. Sediment-load experiments indicated that burial depths of 0.5 cm caused a 91.7% reduction in total seedling emergence and a 99.7% reduction in total invertebrate emergence. Results of our burial experiments corroborated prior research on seedling emergence. However, our study demonstrated that invertebrate emergence is also highly susceptible to the effects of burial. Our research suggests that sediment entering wetlands from agricultural erosion may also hamper successional changes throughout interannual climate cycles. Land-management strategies need to be implemented that will prevent erosion of cropland top soil from entering wetlands.

Productivity is an important ecological function of any natural system and may be quite high in wetlands. Restoration of productive wetlands may play a key role in re-establishing ecological function to portions of the vast areas of wetlands (roughly 86%) drained and otherwise altered in the United States over the past two centuries. A restored wetland at the Montezuma National Wildlife Refuge (upstate New York, USA) was examined to determine if ecological function (i.e., productivity), as well as biotic structure, was restored. Physicochemical conditions and both aquatic and terrestrial productivity were measured at the restoration site and compared with rates and conditions in a reference wetland. Gross aquatic community production rates (based on diurnal oxygen curves) were similar at each site (1,679 and 2,311 g O₂ · m⁻² · yr⁻¹) and within the range expected for the habitat. Terrestrial Net Aboveground Primary Production rates (measured by monthly biomass changes) (2,400 and 2,500 g dry wt. · m⁻² · yr⁻¹) were also similar between sites when tree and herb production were combined. Aquatic respiration rates (3,704 and 4,552 g O₂ · m⁻² · yr⁻¹) were also similar but high, typically more than twice as large as gross aquatic production. As a result, net aquatic production rates at both sites were usually negative, indicating that these small wetlands are organic matter sinks that satisfy aquatic respiration by consumption of both autochthonous aquatic production and imported terrestrial production. They enhance diversity of the local landscape by producing populations of aquatic consumers that cannot be supported by aquatic production alone. Typical wetland conditions and processes developed quickly after restoration, but differences in biotic community structure indicate that observed rates of production and respiration at both sites were maintained by flow through different food-web pathways. Despite the relatively high process rates, any successional progress of the restoration site is expected to be slow.

Before agricultural expansion in the 19^th century, river valleys of North America supported expanses of wetland habitat. In restoring these landscapes, it is important to understand their historical condition and biological function. Synthesizing historical primary accounts (from explorers, travelers, settlers, and farmers) with contemporary knowledge of these wetland systems, we developed a profile of the wetlands and their use by nonbreeding waterbirds (e.g., waterfowl, wading birds, and shorebirds) within the Willamette Valley, Oregon, ca. 1840. We found evidence for three types of wetlands used by non-breeding waterbirds in fall, winter, and spring: emergent wetlands, riverine wetlands, and wetland prairie. The most extensive wetland type was wetland prairie, which functioned as fall/winter habitat for waterbirds, but only while native Kalapuyans managed the region with fire. Since the mid-1800s, four species, in particular, have decreased their use of the Willamette Valley: trumpeter swan (Cygnus buccinator), snow goose (Chen caerulescens), sandhill crane (Grus canadensis), and long-billed curlew (Numenius americanus). Information suggests that ca. 1840, waterbirds and their habitats were more abundant in the Willamette Valley than today. Restoration of the Willamette Valley landscape is warranted, and today's agricultural wetlands—former wetland prairie—hold highest restoration potential.

We characterized wetland mitigation projects at 50 randomly selected sites across Tennessee, USA. Mitigation in the form of creation, restoration, enhancement, and preservation was used to replace the 38 ha of jurisdictional wetlands destroyed. Over 104 ha of compensatory wetland mitigation were proposed for this loss; however, only 77.7 ha were present when each of the sites was delineated. A large percentage of the mitigation area (61%) was in the form of preservation and enhancement of existing wetlands. The majority of sites (72%) contained less area than was stipulated in the permit. Poor design resulting in improper hydrology and poor survival of planted stock was likely the primary cause of this reduced area. Wetland mitigation efforts in Tennessee likely could be improved if greater emphasis was placed on design of the project, especially with regard to the hydrology of the site.

Vernal pools in northeastern North America are typically seasonal woodland pools that support breeding populations of amphibians and invertebrates dependent upon fishless environments for successful reproduction. A survey of 304 vernal pools in southern, central, and northern Maine, USA was conducted to assess pool physical characteristics, landscape setting, and presence of pool-breeding amphibians for the purpose of guiding potential pool conservation strategies. In particular, information on reproductive effort by pool-breeding amphibians was used to assess the statewide applicability of the Maine Natural Resources Protection Act's proposed definition of Significant Vernal Pool, a category of Significant Wildlife Habitats that allows closer environmental review of proposed impacts to vernal pools. The results of our study show regional differences in pool characteristics and amphibian usage. Defining “significance” based on number of egg masses and diversity of vernal pool indicator species is a useful tool but should be considered in the context of such landscape characteristics as availability of suitable terrestrial habitat and distribution of other breeding habitats and wetlands.

An integrated, multimedia-geographic information system (GIS) approach to inventorying and characterizing thirty-nine wetland sites identified on the Winnebago Upper Pool Lakes in Wisconsin, USA was developed. Available black-and-white aerial photographs recorded in 1937, 1957, and 1981 and color digital orthophotos of 2000 were employed as primary data sources to develop a spatio-temporal GIS database using a combination of digital image processing, GIS, Global Positioning System (GPS), and field survey techniques. Ten representative sites were selected to investigate the physical, chemical, and biological characteristics of the wetland habitat in the study area further. Multimedia information as text, graphics, ground photographs, and digital video was then developed to highlight the ecosystem function and structure of those representative wetlands. A computer-based interactive multimedia system, consisting of a graphical user interface and a GIS application module, was constructed to allow easy access to both the spatial data sets and the multimedia information. Given the increased concern over environmental preservation, expansion of urban development, and agricultural land use, it is anticipated that the database will prove valuable for a series of management tasks. The integrated approach provides an innovative way for integrating, analyzing, and presenting wetland information, thus enabling truly interactive collaborations among resource managers, policy makers, researchers, and stakeholders.

The Clear Lake watershed, California, USA has been modified for agriculture since the arrival of Europeans in the early 1800s, and this has led to the deterioration of lake water quality. To assess the response of Clear Lake wetland sediments to recent environmental changes caused by watershed modification, physical and chemical properties of sediment cores at the inlet (Rodman Slough) and outlet (Anderson Marsh) were analyzed. ²¹⁰Pb dating showed increases of sedimentation rate for Anderson Marsh in the 1930s and 1980s, and those increases corresponded to algal blooms and the increase of P input into Clear Lake, respectively. Ranges of recent sedimentation and mass accumulation rates in Anderson Marsh were 0.41–0.52 cm/yr and 1070–1380 g m⁻² yr⁻¹. Accumulation rates of P, Ca, Mg, K, and Pb were slightly higher in Rodman Slough than in Anderson Marsh. Sediment analyses showed that the excess P originating from agricultural activities reach Clear Lake through Rodman Slough and were removed in the lake.

To evaluate the potential development of a macroinvertebrate Index of Biotic Integrity (IBI) for Prairie Pothole Region wetlands, we sampled the aquatic macroinvertebrate and fish communities in 24 semipermanent wetlands located throughout central North Dakota. Wetland basins were selected to encompass a range of surrounding land-use, ranging from 100% grassland to 100% cropland. We used redundancy analysis (RDA) to identify the influences of fish, and temporal and spatial variation on the macroinvertebrate community. We also used RDA to look for relationships between wetland macroinvertebrate communities and land-use. Seventeen potential invertebrate metrics were tested by graphical analyses. We identified a strong influence on the macroinvertebrate community due to the presence of fish. A number of invertebrate taxa decreased in abundance as the summer progressed, and there was noticeable variation in the invertebrate community among individual wetlands of the region. However, we detected no strong relationships between the varying degrees of agricultural land-use in the wetland catchments and the invertebrate community. Consequently, we were unable to identify any effective IBI metrics indicative of land-use disturbance. Lack of correspondence between land-use and macroinvertebrates in this habitat is most likely due to a high degree of natural disturbance (e.g., presence of fish, temporal changes) and a low diversity community of resilient taxa in Prairie Pothole Region wetlands.

The recovery plan for the U.S. federally endangered Xyris tennesseensis calls for increasing the size of some existing populations and establishing new ones in suitable sites. As a contribution to this goal, we investigated seed dormancy and germination and attempted to propagate the species in non-native soil. Freshly matured seeds were conditionally dormant and germinated to 0, 0, 92, 91, and 74% in light after two weeks at 15/6, 20/10, 25/15, 30/15, and 35/20°C, respectively. Seeds retained the ability to germinate to 80–100% in light at 25/15 and at 30/15°C throughout a 39.5-month period of burial in an unheated greenhouse. Following the first year of burial, however, germination at 20/10°C showed an annual cycle, with 79–86% of the seeds germinating in spring but only 0–1% in autumn. Under natural temperature regimes, seeds sown on native soil germinated from mid-May to early August. Seeds had an absolute light requirement for germination, and those incubated at 30/15°C required six days of light (14-hour daily photoperiod) to subsequently germinate in darkness. The species has a small persistent soil seed bank. Although no dormancy-breaking treatments are required for seeds to germinate to high percentages in light at high temperatures, growing seedlings/juveniles in non-native soil is very difficult. Seeds germinated during summer when sown on both inorganic and black organic soils, with and without the addition of lime, but few seedlings lived for more than one month. Only two of 125 juveniles lived for two months after they were transplanted from native soil into black organic soil. One strategy to increase the number of plants at a site may be to remove litter and sow seeds on the surface of undisturbed soil in late spring-summer.

In riparian ecosystems, river flow is the dominant driver influencing ecological process and pattern, including the recruitment of riparian tree species. In a four-year field study (1997–2000) of seedling recruitment on sandbars in the Wisconsin River, I evaluated the hypothesis that the timing of seed dispersal and river flow interact to determine the annual composition of pioneer tree seedling cohorts. In the final three years of the study (1998–2000), growing season flow pulses strongly influenced the species composition and density of new seedling cohorts. Mortality rates of new seedlings exceeded 90% during the 1998 and 1999 flow pulses, and species composition shifted to dominance by Acer saccharinum following the 1999 flow pulse. Different species dominated the cohort of each year: in 1997, 83% of new seedlings were Betula nigra; in 1998, 63% were Salix spp. (S. nigra 39%, S. exigua ssp. interior 24%); in 1999, 89% were Acer saccharinum; and in 2000, 71% were S. exigua and 23% were Betula nigra. Cohorts retained their initial differences in species composition for at least one year after establishment. The three years (1998–2000) with summer flow pulses produced very low end-of-the-growing-season densities of new seedlings (<0.1 seedlings/m² on random plots), and subsequent mortality in the first year after establishment further reduced seedling numbers by 53–94% on monitored plots. Thus, although summer flow patterns during the first year of growth strongly influenced species composition of seedling cohorts, low seedling densities and high overwinter mortality likely reduce the long-term impacts of initial cohort differences on successional trajectories.

Wetland basins in the Prairie Pothole Region of the U.S. are commonly modified by excavation (e.g., roadside ditches, stock dugouts), partial drainage (ditching), and diking. Differences in the distribution of modified wetlands may affect the predictive accuracy of waterfowl survey data if such wetlands are not distributed randomly in the landscape and if waterfowl are not distributed equally among them. We used data collected on thirty-eight 40-km² plots in North Dakota to examine the distribution of modified basins relative to roadside transects and their use by five species of dabbling ducks in 1995. The 800-m-wide transects were subdivided into an inner 400-m transect, centered on the road, and the remaining outer transect area. We compared the distribution of modified and natural wetland basins among three sample areas: 1) the inner 400-m-wide roadside transect area, 2) the outer transect area, and 3) the remaining area within the 40-km² plot that was outside of the transects (outer plot). Duck use was compared between the two transect areas. The plots contained 20,582 basins, of which 88.5% were unmodified, 7.5% were excavated, 3.7% were partially drained, and 0.2% were diked. Nearly all excavated temporary (89%) and seasonal (90%) basins occurred in the inner transect area, reflecting the high proportion of basins that would be defined as roadside ditches. Excavated semipermanent basins were more evenly distributed among the outer plot and two transect widths; these basins often were dugouts but also included roadside ditches. Partially drained and diked basins also were fairly evenly distributed among the three sample areas. Semipermanent basins had greater use by mallards (Anas platyrhynchos) and northern pintails (A. acuta) when they were partially drained than when they were excavated or unmodified; pintails also had greater use of partially drained seasonal basins. Use of wetland basins by gadwall (A. strepera), blue-winged teal (A. discors), and northern shovelers (A. clypeata) did not differ among water regimes or modification. We found no evidence to indicate that duck numbers determined from standard 400-m-wide roadside transects were biased relative to the larger landscape. However, pond counts derived from such transects were biased. Correlations of duck numbers to pond counts that exclude ditches or temporary basins would poorly reflect the response of ducks to available water.

Preserving biodiversity implies the development of indicators to evaluate management practices and to identify critical thresholds and dynamics that modify ecosystems. This study was conducted in the Camargue Delta (South of France). Mediterranean wetlands represent great potential for biodiversity, and their natural dynamics are strongly influenced by water control. We hypothesized that human influence can be estimated by taking into account spatial patterns of human artifacts. We defined two types of landscape indicators of human pressure: the spatial density and the connectivity of the hydrologic network. Co-inertia analysis was used to explore the correlation between these indicators and aquatic macrophyte communities sampled in marshes. Results suggested that human action may strongly influence marsh aquatic macrophyte communities and affect ecological dynamics. Particularly, alteration of wetland integrity by water control may promote the replacement of specialized species by generalist and exotic species. The canal network seems to facilitate dispersion of Ludwigia peploides between marshes. This result confirmed the negative role of corridors in facilitating dispersion of exotic species from one patch to another. We found positive correlations between landscape indicators and macrophyte composition, which is consistent with the tested hypothesis. The density of hydraulic structure was revealed to be a relevant landscape predictor of marsh biological state.

Seagrasses in shallow sheltered regions of estuarine, brackish, and marine environments are of productive and ecological importance. The major seagrass meadows in India exist along the southeast coast (Gulf of Mannar and Palk Bay) and in the lagoons of islands from Lakshadweep (Arabian sea) and Andaman and Nicobar (Bay of Bengal). The flora comprises 15 species and is dominated by Cymodocea rotundata, C. serrulata, Thalassia hemprichii, Halodule uninervis, H. pinifolia, Halophila beccarii, H. ovata, and H. ovalis. Distribution occurs from the intertidal zone to a maximum depth of ∼15 m. Maximum growth and biomass are restricted from the lower littoral zone to the depth of 2–2.5 m. A significant correlation (r = −0.63 and −0.71, respectively, p < 0.05) was observed between depth and biomass from major seagrass meadows. Greatest species richness and biomass of seagrass occur mainly in open marine sandy habitats. Associated and epiphytic floras mainly consist of marine algae and are dominated by members of the rhodophyceae group. Various fishes, molluscs, crustaceans, and echinoderms form the predominant associated fauna. Macrofauna mainly comprised of Oligochaetes (40.17%), Polychaetes (18.96%), Crustaceans (11.36%), and Nematods (18.71%), while meiofaunal groups mainly consisted of Turbellaria (34.17%), Nematoda (37.3%), and Harpacticoida (10.11%). In India, seagrass habitat, although categorized under ecologically sensitive coastal areas, is largely ignored from the educational, research, and management points of views. In spite of being one of the predominant marine macrophytic floras, surprisingly, seagrasses have not been introduced in plant science studies, even at the university level. Unawareness regarding the functions of seagrasses at an educational level and among the common people and coastal zone managers has resulted in enormous damage to them in the recent past. Seagrass habitat is under constantly increasing threat from various anthropogenic activities. Strict implementation of a Coastal Zone Regulation (CRZ) act is imperative to check further deterioration of seagrass beds.

Shallow depressions found in karst terrains may contain wetlands (karst pans) that fluctuate seasonally in response to climatic conditions. This study examined the ground-water hydrology of a chain of 17 wetlands, ranging in size from 0.06 to 0.4 hectares, located in an Appalachian karst valley in central Pennsylvania, USA. The study objective was to determine the contributing area of wetland source waters. A variety of hydraulic head, soil stratigraphy, and water chemistry data indicate that the combined contributing areas of these wetland ponds extend to a maximum distance of approximately 150 m from the ponds. The hydrologic catchment area of the ponds during January and February, 1999 (approximately 2–8 hectares) was significantly smaller than catchment area based on topography (69 hectares). The water source of the wetlands consists of direct precipitation inputs and shallow (0.5–6 m) perched ground water. The hydrologic catchment area of the ponds expands during wet periods and contracts during dry periods. The ponds have been shown to be perched above the regional water table.

We tested the hypothesis that decomposition in flood-inundated patches of riparian tree leaf litter results in higher plant-available nitrogen in underlying, nutrient-poor alluvium. We used leafpacks (n = 56) containing cottonwood (Populus deltoides ssp. wislizenii) leaf litter to mimic natural accumulations of leaves in an experiment conducted on the Yampa River floodplain in semi-arid northwestern Colorado, USA. One-half of the leafpacks were set on the sandy alluvial surface, and one-half were buried 5 cm below the surface. The presence of NO₃⁻ and NH₄ presumed to result from a leafpack's submergence during the predictable spring flood pulse was assessed using an ion-exchange resin bag (IER) placed beneath each leafpack and at control locations. Leafpacks and IERs were collected one week after flood peak (71 days total exposure) at half the stations; the remainder were collected three weeks later (93 days exposure). A multi-peaked spring flood with above-average maximum discharge inundated leafpacks for total time periods ranging from 133 to 577 hours. Litter lost from 43 to 68 percent of its initial organic matter (OM) content. Organic matter loss increased with total time inundated and total time of exposure on the floodplain. Burial retarded OM loss if the total time inundated was relatively long, and substrate texture (sand vs. silt) affected OM loss in a complex manner through interactions with total time inundated and total time of exposure. No pulse of N attributable to leaf breakdown was detected in the IERs, and leafpack litter showed no net change in the mass of nitrogen present. Patterns of leafpack and IER nitrogen levels suggested that litter removed N from floodwater and thereby reduced N availability in underlying sediment. Immobilization of floodwater-N by litter and N mineralization outside the flood period may be important components of N flux in semi-arid and arid floodplain environments.

This study forms part of a French Government initiative supporting research into the function of wetlands as regulators of water regimes and supporters of a rich biodiversity. Aquifer recharge has been studied in a section of the floodplain of the River Adour, between Saubusse and Le Vimport, one of the major wetland areas in southwest France. The study has focused primarily on a major flood event observed during 6 to 19 March 1999. The March flood allows 2.1 × 10⁶ m³ of water to be stored in the sub-surface as the water-table rises to the surface of the floodplain giving complete saturation. After the passage of the flood wave, the water table declines to a level that restores the original volume of water stored in the sub-surface. The 7 km² floodplain has an estimated total sub-surface storage capacity of ∼ 6.3 × 10⁶ m³ down to a layer of impermeable clay. During summer low water periods, the sub-surface storage is estimated to be ∼ 4.2 × 10⁶ m³ (i.e., 67% of the total available sub-surface storage in the zone studied). A hydrologic balance was calculated for the flood event that considers inputs and outputs to the floodplain. The input volume from stream overflow, surface runoff, rainfall, and input from a small stream in the floodplain was estimated to be 6.9 × 10⁶ m³ (of which 5.6 × 10⁶ m³ is retained on the surface). Water outputs including drainage channels, direct drainage by the river, and evapotranspiration were estimated to be 7.5 × 10⁶ m³. These volumes contribute water representing ca. 1.4% of the total flood event flow of 5.40 × 10⁸ m³. Relatively low nitrate concentrations and associated low conductivities were observed in the water sampled at a number of piezometers placed within the study zone. A mechanism is suggested that involves the mixing of water of low nitrate content and conductivity from small streams and the sub-surface within the floodplain, with water containing elevated levels of dissolved nitrate and high conductivity from the River Adour.

The purpose of this study was to determine the changes in concentrations of phosphorus and iron in pondwater and porewater in the littoral zone of Sakaryabaşi-Kirkgiz pond in central Turkey. The pond supplies water to the Rainbow Trout Fish Culture and Research Station in four months in which temperatures do not show a strong variation (16°C-22°C). Concentrations of soluble reactive phosphorus were 4- to 5- fold higher in porewater than in pondwater; thus, diffusion of SRP from porewater to pondwater might be possible. Water content of the sediment was high, although loss on ignition ranged from 13 to 18 % and iron content ranged from 0.16 to 0.22 mg/gdw. The total phosphorus content of the sediment was high, with a range 0.64 to 1.70 mg/gdw, and organic phosphorus was the dominant sedimentary phosphate pool in October, January, and April. Despite having calcerous sediment in the drainage area, a relatively low quantity of phosphorus was bound to calcium and aluminium. In April and October, sediment phosphorus and SRP in porewater and overlying water were greater than in other months. Our results suggest that it would be more appropriate to control phosphorus concentration in spring and autumn than in the warm summer months.