The Trinity River Mitigation Bank was proposed to develop and use a mature, contiguous, diverse riparian corridor along the West Fork of the Trinity River near Dallas, Texas, USA. In the proposed wetland design, water would be diverted from Walker Creek as necessary to maintain wetland function. Therefore, assessment of the magnitude and continuity of the flow from Walker Creek was paramount to successful wetland operation. The Soil and Water Assessment (SWAT) model was used to assess whether the sustained flow (storm flow and base flow) from the Walker Creek Basin could maintain the proposed bottomland wetland ecosystem. For this study, SWAT was modified to allow ponded water within the prescribed wetland to interact with the soil profile and the shallow aquifer. The water budget was prepared for the wetland based on a three-step process. First, data required to run the model on Walker Creek, including soils, topographic, land-use, and daily weather data were assembled. Next, data required to validate the model were obtained. Since stream flow was not available at the proposed site, flow from a nearby watershed with similar soils, land use and topography were used. In the final step, the model was run for 14 years and compared to the measured water balance at the nearby watershed. The model results indicate that the wetland should be at or above 85 percent capacity over 60 percent of the time. The wetland did not dry up during the entire simulated time period (14 years) and reached 40 percent capacity less than one percent of the time during the simulation period. The advantages of the continuous simulation approach used in this study include (1) validation of wetland function (hydroperiod, soil water storage, plant water uptake) over a range of climatic conditions and (2) the ability to assess the long-term impact of land-use and management changes.

The recent expansion of Phragmites australis (common reed) from the marsh-upland interface into high marsh zones provides an opportunity to assess the impact of individual plant species on biomass production and decomposition in salt marshes. Seasonal harvests of aboveground and belowground biomass demonstrate that annual production of P. australis is approximately three times greater for aboveground biomass, two times greater for belowground biomass, and 30% lower in root: shoot ratio than neighboring populations of S. patens. Whole-plant litter (stems and leaves) also decomposes at a much slower annual rate for P. australis (k = 0.25) than S. patens litter (k = 0.57). By crossing litter type with site of litter decomposition, I found these plant species to influence decay rates through litter type and not through their effects on marsh surface conditions (e.g., temperature, sedimentation rates). Based on these calculations, annual rates of carbon accumulation in the peat of high marshes are likely to increase 5-fold once P. australis becomes established due to its greater rates of biomass production and residence time in infrequently flooded brackish marshes.

The composition of seed banks of areas on the drained Kissimmee River floodplain (Florida, USA) that are currently pasture and formerly had been wet prairie, broadleaf marsh, and wetland shrub communities was compared to that of seed banks of areas that have extant stands of these communities. The species composition of the seed banks of existing wet prairie and former wet prairie sites were the most similar, with a Jaccard index of similarity of 55. Existing and former broadleaf marsh and wetland shrub communities had Jaccard indices of 38 and 19, respectively. Although existing and former wet prairie seed banks had nearly the same species richness, species richness at former broadleaf marsh and wetland shrub sites was higher than at existing sites. Mean total seed densities were similar in existing and former wet prairies (700 to 800 seeds m²). However, seed densities in former broadleaf marsh and wetland shrub sites were significantly greater than in comparable existing communities (>4,900 seeds m² at former sites versus 200 to 300 in existing communities). The higher seed densities in former broadleaf marsh and wetland shrub sites was due to over 4,000 seeds m² of Juncus effusus in their seed banks. Half of the species that characterize wet prairies were found in the seed banks at former and existing wet prairie sites. At existing broadleaf marsh and wetland shrub sites, most of the characteristic species were found in their seed banks. However, only one characteristic broadleaf species was found in the seed banks of the former broadleaf marsh sites, and no characteristic wetland shrub species were found in the seed banks of the former wetland shrub sites. The seeds of only two non-indigenous species were found in the seed banks of former wetland communities at very low densities. For all three vegetation types, but particularly for the broadleaf marsh and wetland shrub sites, re-establishment of the former vegetation on the restored floodplain will require propagule dispersal from off-site sources.

Conflicting interpretations of the negative impacts of invasive species can result if inconsistent measures are used among studies or sites in defining the dominance of these species relative to the communities they invade. Such conflicts surround the case of Lythrum salicaria (purple loosestrife), a widespread exotic wetland perennial. We describe here a 1999 study in which we quantified stand characteristics of L. salicaria and associated vegetation in arrays of 30 1-m² plots in each of five wet meadows in Connecticut, USA. We explored linear and non-linear relationships of above-ground plant biomass, stem density, and indices of species richness, diversity, and composition to gradients of L. salicaria dominance, including stem density, percent cover, and biomass. Species richness, other diversity metrics, and stem density of other species were not significantly correlated with the density or percent cover of L. salicaria stems. The relative importance values (number of quadrats in which they were found) of co-occurring species in low-density L. salicaria quadrats were significantly correlated with their relative importance in high-density L. salicaria quadrats, indicating that only modest shifts in abundance occurred as L. salicaria increased in density. No individual species were consistently associated with or repelled by the presence of L. salicaria across sites. In contrast to density and diversity features, however, the total biomass of species other than L. salicaria was significantly, negatively correlated with the total biomass of L. salicaria at each site surveyed. Lythrum salicaria in pure, dense stands maintained a greater above-ground standing biomass on invaded sites than uninvaded vegetation of similar physiognomy. This study demonstrates that hypotheses about L. salicaria effects can vary depending upon the ecological metric that is examined. Where one-time, correlative studies are the most feasible option, data taken on a range of metrics—especially biomass—should be taken to inform us about mechanisms by which L. salicaria invades and predominates in wetlands.

This paper describes a study of nutrient dynamics in 12 tidal and non-tidal freshwater riverine wetlands in The Netherlands, Belgium, and Maryland (USA). The purpose of the study was to investigate the relationships between nutrient cycling processes in riverine wetlands that were geographically separated, that were dominated by different types of vegetation, and that had different hydrodynamics. We also compared restored and natural riverine wetlands. The results showed distinct differences in interstitial water chemistry between the sites in Maryland and Europe. No such regional differences were found in the soil variables, except for soil phosphorus, which was higher in The Netherlands. Soil organic matter, total nitrogen and phosphorus content, and bulk density were higher in tidal freshwater wetland soils. Forested wetland soils had higher organic matter and total nitrogen and lower bulk density and total phosphorus than soils from wetlands dominated by herbaceous species. Restored wetlands had lower soil organic matter and total soil nitrogen and phosphorus than similar types of natural riverine wetlands. There were no differences in nutrient-related process rates nor plant nutrient concentrations in tidal versus non-tidal riverine wetlands. Lower nitrogen and phosphorus concentrations in plants at the restored sites suggest that nutrient uptake by vegetation may be poorly coupled to rates of nutrient cycling during early stages of vegetation development. A principal components analysis of the data identified groupings of soil and water variables that were similar to those that had been previously identified when we applied the same methods to peatlands that were also geographically widely separated. Results of the study demonstrate that the techniques that we have been using are robust and repeatable. They are especially useful for making general comparisons of nitrogen and phosphorus cycling when there are limitations on the number of wetland that can be sampled. The approach that we have developed may also be used to calibrate and refine nutrient cycling models that are incorporated into wetland assessment procedures.

We evaluated the use of macroinvertebrates as a potential tool to identify dry and intensively farmed temporary and seasonal wetlands in the Prairie Pothole Region. The techniques we designed and evaluated used the dried remains of invertebrates or their egg banks in soils as indicators of wetlands. For both the dried remains of invertebrates and their egg banks, we weighted each taxon according to its affinity for wetlands or uplands. Our study clearly demonstrated that shells, exoskeletons, head capsules, eggs, and other remains of macroinvertebrates can be used to identify wetlands, even when they are dry, intensively farmed, and difficult to identify as wetlands using standard criteria (i.e., hydrology, hydrophytic vegetation, and hydric soils). Although both dried remains and egg banks identified wetlands, the combination was more useful, especially for identifying drained or filled wetlands. We also evaluated the use of coarse taxonomic groupings to stimulate use of the technique by nonspecialists and obtained satisfactory results in most situations.

Soil characteristics of a wide variety of created wetlands were compared to those of native wetlands in phosphate-mined areas from central and north Florida, USA. Criteria selected for evaluation of soil samples from 184 sites included soil compaction, bulk density, organic matter (carbon) and nitrogen content, C:N ratio, and available and total nutrient contents. Organic matter accumulation, one of the indicators of a functional wetland, increased across transects going from uplands toward the center of the wetlands, and with wetland age. The organic matter accumulation rate in the AO and A1 horizons was 320 g m² yr⁻¹. Native wetlands had significantly greater organic matter accumulation, both in the litter and mineral soil surface. The C:N ratio of the soil organic matter decreased with created wetland age and approached values commonly found in wetland soils (15–25). Bulk density decreased with increasing organic matter content in the created wetlands, and low bulk density soils appeared to support better vegetative growth. Based on the above-mentioned parameters, reclaimed wetlands are slowly developing into “typical” wetlands; the rate of development could possibly be increased by minimizing soil compaction, incorporation of organic matter, or by fertilization.

Tamarisk (Tamarix spp.), an introduced shrub or small tree, has invaded riparian areas throughout the western United States. Tamarisk invasion has been studied extensively in the Southwest, but there is little information on its performance at the northern margin of its naturalized range. We measured the canopy cover, density, height and age of tamarisk and plains cottonwood (Populus deltoides) in 50 plots at 25 sites along the Bighorn, Powder, and Yellowstone rivers in southeast Montana near the northern edge of tamarisk's western North American range. Tamarisk commonly formed thickets on open, low terraces and along overflow channels but was less dense beneath a cottonwood canopy. Tamarisk stems routinely died back to the ground, and the oldest live stems were generally much younger than the plants. Tamarisk 30 to 40 years old in our study area usually attained heights of only 4 m or less. Height and number of live stems of tamarisk plants were 16% and 44% lower respectively under a tall cottonwood canopy. Cottonwood grows faster than tamarisk, eventually shading it and causing its decline. We believe that tamarisk will be only an understory shrub in most eastern Montana riparian forests, declining as cottonwoods form a closed canopy. Minimizing the spread of tamarisk in riparian areas in Montana can best be accomplished by managing for cottonwood.

Kampoosa Bog in Stockbridge, Massachusetts, USA is a 70-ha wetland comprised of calcareous basin fen and red maple swamp bordered, in part, by roads including the Massachusetts Turnpike. High salt concentrations in the ground water (due to the application of deicing salts on the Turnpike) and Phragmites australis colonies appear to be impacting the native vegetation at this site. Sodium and chloride concentrations at Kampoosa Bog are generally below previously published threshold levels for impacting vegetation, although such levels vary by species and in relation to other environmental stress conditions. Giant reed (Phragmites), a salt-tolerant invasive species, invaded the northern portion of the wetland adjacent to the Turnpike and a gas pipeline sometime after they were built in the 1950s. By 1998, Phragmites had formed dense colonies that continued to spread across the wetland, which supports several state-listed rare plant and animal species. High salt concentrations (Na > 112 mg/L, Cl^- > 54 mg/L) are present up to 300 meters from the Turnpike. Phragmites colonies occur in areas with high and low salt concentrations, and the species abundance is not well-correlated with elevated salt levels. Although high salt concentrations and Phragmites abundance do not seem to produce an interaction effect on the vegetation of the wetland, the graminoid fen community is impacted by both factors separately. We attribute decreases in the abundance of species between invaded and non-invaded areas to the presence of Phragmites. In the graminoid fen, we attribute decreases in both community measures (richness, evenness, and overall cover) and individual species abundances to high salt concentrations.

In this paper, some issues of the autoecology of Halocnemum strobilaceum (a rare succulent halophyte that occurs in southeastern Spain) are examined, particularly the germination process and the first stages of plant development. In regards to germination, this species shows the general pattern of halophytes under increased salt stress (reduced germination and germination rate). What stands out is the extreme salt tolerance of H. strobilaceum seeds. The stimulation of root length by the presence of salt probably plays an important role in avoiding salt stress at surface-level soils, within salt concentrations where germination still occurs. Halocnemum strobilaceum typically accumulates Na ions, which, combined with Cl^-, contributes to the internal osmotic potential. The accumulation of both ions clearly increases with an increase in salinity stress. In contrast, accumulation of K , Mg² , and Ca² decreases with an increase in salinity stress. Glycinebetaine contents are approximately 100 times greater than proline contents, although their contribution was significant only if cell compartmentalization was considered. The accumulation of ions along with the osmoprotective compounds glycinebetaine and proline allows seedlings to mantain a lower internal osmotic potential than that of the growth medium, which is necessary for water uptake in saline soils.

Only a few relatively wide barrier islands support shallow freshwater aquifers. Rare, swale wetlands occur on islands where fresh water inundates, at least seasonally, low-lying troughs between interior dunes. Swale wetlands are dominated by emergent vegetation and submerged aquatic vegetation in the deepest areas and by woody shrubs in more shallow areas. On southern Hatteras Island, wetland shrubs have progressively invaded open water areas over the past 40 years, suggesting a change in hydrologic regime. To determine the relationship between vegetation cover type and length of saturation, water-level fluctuations over time were analyzed to tie boundaries of six wetland cover types to the duration of soil saturation at 20-cm depth. We found that areas dominated by herbaceous vegetation had significantly longer flooding regimes than areas dominated by shrubs (85–95% vs. 12–69% of the growing season, respectively). Only 22–25 cm elevation differences were found to separate emergent marsh from the various shrub cover types, suggesting that lowering the mean water level via drainage has likely been responsible for shrub swamps replacing emergent marsh in swales. Although succession from open water to shrub swamp probably occurs naturally in the absence of drainage through the accumulation of organic matter, natural disturbances such as wildfire and storm-driven surges of saline water would have periodically re-set succession. Therefore, managing for long-term maintenance of freshwater swale wetlands on barrier islands should include (1) eliminating or controlling drainage through constructed ditches, (2) eliminating man-made barriers that prevent the transport of saline water into ponds during hurricanes and nor'easters, and (3) initiating a prescribed burning program to mimic the historic, natural fire regime.

Playas undergo dynamic environmental changes throughout the growing season, resulting in the need for a persistent seed bank for plants to respond to these changes. Therefore, we investigated seasonal germination patterns of species found in seed banks of playa wetlands. We used the seedling-emergence technique to determine recruitment patterns from seed banks of eight playas. In the greenhouse, seed-bank samples were subjected to two treatments, drawdown or flooded, over a 210-day duration divided into seven 30-day time periods. In both treatments, seedling emergence differed among time periods and species but was similar among playas. Approximately 52% of drawdown seedlings and 44% of seedlings occurring in the flooded treatment germinated in the first 30 days. Plants occurring in playa seed banks had variable germination strategies. Three patterns for common (>5% occurrence) species were identified in the drawdown treatment: (1) early germinators (those species that germinated rapidly after exposure to treatments with low germination during the remainder of time periods), (2) late germinators (those that germinate after specific environmental conditions have existed for some time), and (3) continuous germinators (those with even germination rates throughout submersion). Two patterns were found for common species in the flooded treatment: (1) early germinators and (2) continuous germinators. Germination throughout the period of suitable environmental conditions was the dominant strategy for persistence in the unpredictable playa environment. With only a few exceptions, species persisting in seed banks of playas do not show germination for all available seeds upon creation of suitable environmental conditions but rather use viable dormant seeds as a hedge against the unpredictable environment.

Great Lakes coastal marshes serve as spawning areas for adult and nurseries for young-of-year fishes, but the capacity of these habitats to facilitate fish reproduction is threatened due to their continued destruction and degradation. In order to appreciate the consequences of marsh loss and degradation, we collected fish larvae with icthyoplankton nets during the summers of 1997 and 1998 in three coastal marsh bays in Les Cheneaux, northern Lake Huron. In addition, we obtained several metrics of human activities and local habitat features (vegetation, water temperature, and substrate slope) and evaluated the importance of these metrics in structuring local larval fish assemblages. Our study indicated that local habitat features strongly and directly affected local larval fish assemblages in Les Cheneaux, while human activities did not. However, human activities may have altered local habitats in Les Cheneaux, thus indirectly impacting local larval fish assemblages.

Wisconsin has lost approximately 2 million hectares of wetland since statehood (1848). Through the combined efforts of state and federal agencies and private groups focused primarily on wetland restoration for waterfowl habitat management or compensatory mitigation, a fairly substantial gain in wetland area has been achieved. Much of the wetland restoration effort in Wisconsin has occurred on formerly agricultural lands. However, due to the nature of the past disturbance and possible residual effects not corrected by simply returning surface waters to these lands, there is some question regarding the resultant wetland quality or biological integrity. In an effort aimed at developing tools to measure wetland gains in terms of quality or ecological integrity, the Wisconsin Department of Natural Resources (WDNR) initiated a study of biological communities on restored wetlands in Wisconsin. In this paper, we report on the community of microcrustaceans and arthropods that can be collected with a plankton net in open water in wetlands. We examined zooplankton community structure in restored wetlands in terms of richness, taxonomic representation, and Daphnia sexual reproduction and related these metrics to attributes on wetlands representing least-disturbed conditions and agriculturally impacted wetlands. We sampled 56 palustrine wetlands distributed across Wisconsin. These wetland sites were categorized as agricultural, least-impacted, and restored (recently withdrawn from agricultural usage). The wetlands were reasonably homogeneous in many ways, so that taxon richness was not correlated with basin origin, presence of adjacent roads, presence or absence of fish, water chemistry, or the size of the open water. We identified a total of 40 taxa. Taxon richness was significantly lower in agricultural sites (average of 3.88 taxa per site) compared to that of least-impacted sites (7.29 taxa) and restored sites (7.21 taxa). Taxon richness of restored sites was significantly correlated with time since restoration. The data indicate that taxon richness changes from a value typical of agricultural sites to the average richness of least-impacted sites in about 6.4 years. The total taxon list for 8 agricultural sites (14 taxa) was significantly smaller than the average value for randomly chosen sets of 8 least-impacted sites (20.4 taxa). Agricultural and least-impacted sites tended to have the same common taxa. Many taxa of chydorid cladocerans and cyclopoid copepods that were rare in least-impacted sites did not occur in the agricultural sites, nor did fairy shrimp occur in agricultural sites. Daphnia populations only produced males in least-impacted and restored sites. Further research is needed to identify the mechanism(s) responsible for the reduced species richness and lack of sexual reproduction in agricultural wetland sites. Likely factors include eutrophication, turbidity, or chemical contamination. We conclude that restoration of wetland watersheds works. Withdrawal of the watershed from agricultural usage is followed by an increase in taxon richness, and the sites resembled least-impacted sites in about 6–7 years.

Activity traps are commonly used to develop abundance indices of aquatic invertebrates and may be deployed with either the funnel parallel to the water surface (horizontal position) or facing down (vertical position). We compared the relative performance of these two positions in terms of numbers of invertebrates captured, species richness of samples, detection rates of specific taxa, and community-level characterizations. Estimates of zooplankton abundance were also compared to quantitative estimates obtained using a water-column sampler. We used a matched-pairs design where 10 pairs of traps (one horizontal, one vertical) were deployed in each of 4 prairie wetlands on 5 dates in 1999. Vertical traps had higher detection rates and captured greater numbers of adult and larval Coleoptera, Hemiptera, Chaoboridae, hydracarina, cladocera, and Copepoda and also produced samples with greater species richness. Horizontal traps captured greater numbers of Amphipoda and Ostracoda and had higher detection rates for these taxa. Estimates of zooplankton abundance with vertical traps also correlated better with quantitative estimates and indicated greater differences between wetlands than horizontal traps. Both traps showed similar relationships among wetlands and changes through time at the community level, but vertical traps were more sensitive to temporal change. Our results indicate that vertical traps outperform horizontal traps and are preferable for obtaining indices of invertebrate abundance.

Traditional methods for sampling aquatic macro-invertebrates are very labor-intensive and largely ineffective when attempting to collect Florida applesnails (Pomacea paludosa) from their natural wetland habitats. We found the use of funnel traps an effective alternative that decreased collection time ten-fold and required considerably less labor than throw traps. The funnel traps described herein can be used effectively for collecting applesnails in a variety of wetland habitat types and plant densities, and they may also be effective in catching other wetland organisms (e.g., Kinosternid turtles).