Introduced saltcedar (Tamarix ramosissima, T. chinensis, and their hybrids) reaches its northward distribution in the Great Plains in Montana, USA. We mapped the locations, patterns of abundance, and ages of saltcedar along the Musselshell River and Fort Peck Reservoir in northeastern Montana to identify concentrations of plants that could be used to infer introduction location, establishment year, and mechanisms of dispersal. We estimated the presence of 24,500 plants on the Musselshell River over a river distance of 240 km, with concentrations at three nodes close to Roundup (2,000 plants, seedlings to 24 years), Melstone (6,000 plants, seedlings to 23 years), and the mouth of the river at Fort Peck Reservoir (10,000 plants, seedlings to at least 11 years). Concentrations at Roundup and Melstone probably originated from urban plantings in the 1960s. The third concentration may have established from seeds and plant pieces washed downriver during floods and deposited in the hydraulic backwater of the Musselshell River delta at Fort Peck Reservoir. We believe there may be one-half to one million plants on Fort Peck Reservoir, with concentration nodes at recreation areas on the south shore. We estimated 3,500 mature saltcedar to be present at the Devils Creek Recreation Area, more than 11,000 plants at Hell Creek Recreation Area, and more than 40,000 plants at 6 sites at the south end of Dry Arm close to the Nelson Creek Recreation Area and mouth of Big Dry Creek. The oldest plants on the reservoir were 21 to 33 years old in 2001. Based on these ages, we suggest that saltcedar arrived at the south shore of Fort Peck Reservoir in the mid- to late 1960s, which means that it must have dispersed from the Bighorn/Yellowstone River system soon after it became established in southern Montana. Although wind dispersal and ornamental plantings cannot be ruled out as primary transport mechanisms to the reservoir, the concentrations and ages of saltcedar at recreation areas suggest that seeds and other plant propagules were also transported to the reservoir by earth-moving equipment during site construction between 1966 and the mid-1980s and later by boats and their towing vehicles. Saltcedar was dispersed away from these nodes by wind and water. As Tamarix ramosissima and T. chinensis originated in the cold dry deserts of northeastern Asia, saltcedar may not be limited in its northward expansion by the cold winters, short growing seasons, and periodic droughts characteristic of the northern Great Plains in Canada.

We investigated the soil chemical environment of coastal peat mires with a Picea glehnii forest and Sphagnum community in Ochiishi, north-eastern Japan. We tested the hypothesis that the soil chemical environment in an ombrotrophic peat mire is affected by the vegetation and the consequent chemical modification of precipitation by plants. We measured the chemical properties of peat pore water and precipitation both in the P. glehnii forest and the Sphagnum community and found that the forest acidifies the peat and accumulates sea salt deposited by precipitation. Picea glehnii grows in soils that have a higher salt concentration than the Sphagnum communities. We measured a stem flow salt concentration that was higher than the bulk deposition. The salt concentration in precipitation and peat pore water decreased with increasing distance from the coastline. These results imply that atmospheric sea salt deposition is effectively trapped by the P. glehnii canopy, and it then contributes to the accumulation of salt and the consequent acidification within the peat. Stem-flow water was more acidic than bulk deposition or throughfall within the P. glehnii forests. This means that acids are dissolved while precipitation runs through on the bark of P. glehnii, and then the acids are transferred and accumulate in the peat. The chemical modification of precipitation by P. glehnii makes the soil chemical environment more acidic than the Sphagnum community that usually makes the soil environment acidic in a peat mire ecosystem.

Foraging activity by snow geese (Chen caerulescens) often creates large areas devoid of vegetation (“eat-outs”) in moist-soil impoundments and coastal wetlands. Open-water habitats that result from eat-outs may be valuable foraging areas for other wetland-dependent birds (i.e., waterfowl and shorebirds). However, few studies have examined the effects of goose-induced habitat changes on invertebrates, an important food source for both waterfowl and shorebirds. We quantified changes in abundance and composition of benthic invertebrates in response to snow goose herbivory in moist-soil impoundments at Prime Hook National Wildlife Refuge, Delaware, USA. We found invertebrate taxon richness and diversity and abundance of Chironomidae, Coleoptera, and Total Invertebrates to be higher in goose-excluded sites than in adjacent eat-outs. These effects were most pronounced during January, February, and early April. We also measured invertebrate abundance in shorebird exclosures in eat-outs but found few detectable effects of shorebird predation on invertebrates. Our study demonstrated that abundant snow geese may negatively influence availability of invertebrates for other nonbreeding waterbirds, suggesting that management actions to reduce local goose populations or deter feeding in impoundments may be warranted.

Coastal wetland loss is a major environmental issue in the Mississippi Delta region of the southern United States, where grasses such as Spartina alterniflora may play a critical role both as early colonizers on created sites and as facilitators of other marsh grasses and shrubs, particularly at high intertidal elevations. We explored the potential role of S. alterniflora as a facilitator of the colonization and growth of the shrub Baccharis halimifolia at two created wetlands in southwestern Louisiana through a combination of plant surveys and experimentation. Surveys for the presence of B. halimifolia inside and outside the bare centers of S. alterniflora clones that had begun to senesce inwardly were conducted at a 4-yr-old site originally created in 1993. The percent of clones containing B. halimifolia and the number of individual B. halimifolia plants per clone increased with increasing S. alterniflora clone size and decreased with increasing distance from an adjacent containment berm. Two experiments conducted at a second 4-yr-old site that was originally created in 1996 were designed to assess seed capture and growth of seedlings of B. halimifolia inside S. alterniflora clones. These experiments revealed that while significantly fewer seeds settle inside clones, those seedlings that grow in such areas gain a clear advantage in terms of both survival and rate of growth, which helps to explain the results of the initial survey and testifies to the role of S. alterniflora as a nurse plant in newly-created high intertidal marshes.

The zonation of Scirpus mariqueter and Scirpus tabernaemontani communities is conspicuous in salt marshes of the Changjiang estuary. However, diking, which partly restricted tidal fluctuation in a salt marsh, resulted in the invasion of S. tabernaemontani into S. mariqueter communities. To explore the role of the interaction between the two species in the vegetation change, the structure of S. mariqueter tussocks at low elevation and S. tabernaemontani clones at medium elevation were investigated in the diked marsh, and biomass allocations to different components of the two species was also estimated. Scirpus mariqueter performed better at the edges of the tussocks but aged and declined in the central areas of the tussocks with low density of living shoots, large proportion of flowering shoots, and low aboveground dry mass. Scirpus taberaemontani grew vigorously in the center areas of large S. taberaemontani clones with high density of shoots, and those clones were surrounded by a residual ring of S. mariqueter, whose structure was similar to the pattern observed in the tussocks of S. mariqueter. Comparison of the vegetation structure along the elevational gradient of the diked marsh suggests that S. taberaemontani invades the center area of the Scirpus mariqueter tussocks, possibly due to changed topography and its well-developed aerenchymatous tissue. Scirpus tabernaemontani allocates a significantly greater proportion of biomass to photosynthetic shoots and rhizomes than S. mariqueter does, both above ground and below ground, a potential competitive advantage. Once established in the central areas of the S. mariqueter tussocks, S. taberaemontani successfully replaced S. mariqueter. We hypothesize that the competitive displacement of S. mariqueter by S. taberaemontani plays an important role in the vegetation change after the short-term tidal restriction and also in generating plant zonation in the salt marshes.

The regulation and management of wetlands is often contentious because wetlands share characteristics of both land, typically a private good, and water, typically treated as a public good. Landowners' desires to develop “their property” with wetlands tend to conflict with the public benefits associated with healthy, intact wetland ecosystems. To understand better how residents in the state of Michigan, USA understand and perceive wetlands, a statewide telephone survey was undertaken. The survey of 1012 Michigan residents revealed most people to be very familiar with wetlands and think it very important to protect them. Across demographic groups, at least 60 percent of respondents believe it to be very important that wetlands exist both now and in the future. Multiple regression analysis suggests that younger, better educated, and wealthier people place greater importance than others on wetland existence; the analysis also indicates that Republicans seem to value wetlands slightly less than Democrats and Independents. Interestingly, respondents' community type (e.g., rural, urban, suburban) appears to make relatively little difference on the importance of wetland existence.

Although regulatory agencies in the USA typically require 3–5 yr of post-restoration monitoring of biotic responses to wetland mitigation, many researchers have argued that longer time frames are needed to assess population responses adequately. We conducted an 8–yr study to examine the demographic responses of the wood frog (Rana sylvatica) and spotted salamander (Ambystoma maculatum) to wetland creation at a mitigation bank in western North Carolina. Our primary goals were to compare juvenile output in ten reference and ten constructed ponds and to assess the overall change in breeding population size in response to site restoration. We used annual censuses of egg masses to assess changes in breeding population size and used estimates of larval population size at hatching and the initiation of metamorphosis to assess embryonic and larval survival. Adults of both species bred in most constructed ponds within a few months after filling in 1996. Estimated juvenile production from 1996 to 2002 did not differ significantly between pond types for either species. The percentage of both constructed and reference ponds that produced juveniles decreased markedly from 1996 to 1998 and remained low through 2002. The decrease in juvenile output was mostly associated with reduced larval survival rather than increased embryonic mortality across years. Drought and outbreaks of a pathogen (Ranavirus) were the primary causes of low juvenile production from 1998 to 2002. The overall breeding population of R. sylvatica increased markedly in 1999–2000 following a large recruitment of juveniles from constructed ponds in 1996–1997. With the onset of drought and ranaviral infections, the population declined to levels in 2002 that were at or below 1995 pre-restoration numbers. Despite site perturbations, the breeding population of A. maculatum remained relatively stable from 1995 to 2002, a phenomenon that may reflect selection for delayed reproduction and iteroparity in this species. Although we have monitored R. sylvatica and A. maculatum for seven breeding seasons after the creation of seasonal wetlands, we are still uncertain that site restoration will achieve the goal of increasing breeding populations above pre-restoration levels. Because amphibians have significant population lags and are sensitive to site perturbations, monitoring that exceeds five years may be required to assess demographic responses to site restoration adequately.

Patchy wetlands are commonly found in the polar desert at localities where ample water supply is available during the thawed season. These wetlands can occur on a wide range of topography, and they support more luxuriant vegetation than their surrounding areas. Snowbank wetlands are characterized by a zonation of vegetation, with increasingly rich plant coverage away from the snowbed edge. Ground-water wetlands usually occupy topographic concavities or depressions, with exfiltration of subsurface water to sustain a high water table and to provide an enrichment of nutrients. Riverine wetlands experience prolonged flooding during the peak snowmelt season, and their vascular plant cover is low owing to inundation by the cold, turbulent stream water. Lakes and ponds are associated with topographic depressions, receiving surface- and ground-water inputs from catchment areas larger than the surface extent of the water bodies. Their evaporation rates are high, but the open water season is curtailed by ice cover. Lake outflow wetlands are supported by spillage and seepage from lakes, and they maintain a relatively lush vegetation cover. Coastal wetlands form narrow strips enclosed by raised beaches, with high salinity that limits plant diversity. Strong interactions exist among the water and heat fluxes to the wetland, the vegetation, and the hydrogeomorphology. Locally enhanced water supply and shallow permafrost enable frequent saturation, augmenting nutrient enrichment and encouraging vegetation development. Slow vegetation decay in a cold environment facilitates the formation of peat. The saturated soil conditions give rise to large ground-ice content in the winter, requiring much latent heat for ground thaw in subsequent summers. This, together with the insulating properties of the organic layer, creates shallow frost tables during the summer and produces a positive feedback that maintains high water tables in the wetlands to favor plant growth.

The initial stages of seed-bank and vegetation development were documented in a newly created tidal freshwater wetland where donor soils were not applied. The 32.3-ha site adjacent to the Delaware River in New Jersey, USA was completed in stages from November 1993 to November 1994. Objectives of the study were to determine characteristics of the seed bank and vegetation and to monitor spatial and temporal changes. The study was carried out from 1995 to 1999 using three sites (North, East, and South Marshes) and three elevation locations (1 m from a tidal channel, midpoint, and 1 m from the upland edge). Development of the seed bank and vegetation demonstrated tremendous colonization potential derived from regional and local sources. Colonization and complete plant cover occurred within one year, and subsequent changes were rapid. Individual species behaved uniquely regarding colonization time, duration, and decline in both the seed bank and vegetation. Large seed banks of some species were present even after decline in the vegetation. Overall, the seed bank was large, small-seeded and persistent, and diverse. A total of 177 species occurred in soil seed bank and 92 in field vegetation samples, with 72 contributing to cover. Seed-bank densities (mean ± SE/m²) ranged from 450 ± 152 to 394,600 ± 29,950. Species richness (species/sample) ranged from 3.3 ± 1.2 to 32.3 ± 1.8. Density and species richness were clearly reduced by inundation and were lowest in channel edge samples and in the first year (1995). Cover species richness ranged from 1.6 ± 0.2 to 7.3 ± 0.6 per quadrat. Complexity of the vegetation increased over time, with lowest diversity along the channels. The 1995 site differences, with greatest densities and species richness in the East Marsh, could be related to site history (timing of construction). Species similarity between the seed bank and vegetation ranged from 11 to 53 % and showed no site, location, or temporal pattern. However, similarity between sites of the seed bank and vegetation increased from 1995 to 1998. Several New Jersey State rare or threatened species, as well as invasive species, were present. Results indicated that it is ecologically feasible to create a wetland adjacent to a tidal freshwater river without use of donor soil and that transplantation had not been necessary.

The use of dredge material is a well-known technique for creating or restoring salt marshes that is expected to become more common along the Gulf of Mexico coast in the future. However, the effectiveness of this restoration method is still questioned. Wetland structural characteristics were compared between four created and three natural salt marshes in southwest Louisiana, USA. The created marshes, formed by the pumping of dredge material into formerly open water areas, represent a chronosequence, ranging in age from 3 to 19 years. Vegetation and soil structural factors were compared to determine whether the created marshes become more similar over time to the natural salt marshes. Vegetation surveys were conducted in 1997, 2000, and 2002 using the line-intercept technique. Site elevations were measured in 2000. Organic matter (OM) was measured in 1996 and 2002, while bulk density and soil particle-size distribution were determined in 2002 only. The natural marshes were dominated by Spartina alterniflora, as were the oldest created marshes; these marshes had the lowest mean site elevations (< 30 cm NGVD). The six-year-old created marsh (formed in 1996) was higher in elevation (> 35 cm NGVD) and became dominated by high marsh (S. patens, Distichlis spicata) and shrub (Baccharis halimifolia, Iva frutescens) species. The higher elevation marsh seems to be following a different plant successional trajectory than the other marshes, indicating a relationship between marsh elevation and species composition. The soils in both the created and natural marshes contain high levels of clays (30–65 %), with sand comprising < 1 % of the soil distribution. OM was significantly greater and bulk density significantly lower in two of the natural marshes when compared to the created marshes. The oldest created marsh had significantly greater OM than the younger created marshes, but it may still take several decades before equivalency is reached with the natural marshes. Vegetation structural characteristics in the created marshes take only a few years to become similar to those in the natural marshes, just so long as the marshes are formed at a proper elevation. This agrees with other studies from North Carolina and Texas. However, it will take several decades for the soil characteristics to reach equivalency with the natural marshes, if they ever will.

This study investigated the distribution and determinants of marsh vegetation along the major distributary channel system of southern Africa's largest wetland, the Okavango Delta, using a large, interdisciplinary data set. Eight communities were recognized, dominated respectively by Pennisetum glaucocladum, Phragmites mauritianus, Cyperus papyrus, Cyperus papyrus/Miscanthus junceus, Miscanthus junceus, Imperata cylindrica, Pycreus nitidus and a mixed bog community. The Pennisetum glaucocladum community is situated in the Panhandle (a narrow valley reach at the head of the fan) on elevated scroll bars that are flooded seasonally for short periods (days to weeks). The Phragmites mauritianus community occurs largely in the Panhandle where channel margins have high clay contents and where soils are seasonally flooded for moderate periods (months). Fires are widespread in the Panhandle, but both Pennisetum glaucocladum and Phragmites mauritianus are stoloniferous, and meristems occur below the soil surface and are protected from fire. In contrast, the rhizomatous sedge C. papyrus dominates in situations where meristems are permanently submerged, and therefore protected from fire, such as areas of open channel water where current velocities are sufficiently low to enable the extension of C. papyrus into the channel. This situation exists where channel avulsion has recently taken place or where discharge is reduced by water loss from the channel by overspill. The semi-floating habit of C. papyrus in the channel fringe results in high hydraulic conductivities, which promotes water loss from channels and leads to sediment deposition within channels. Miscanthus junceus occurs in areas where the nutrient status of water is low, seasonal changes in water level are small, and the average water level is approximately constant over decadal time scales. It occurs some distance from the channel on the upper reaches of the Delta and progressively closer to the channel downstream such that it is the dominant channel fringe species in the distal reaches. This pattern, where a community occurs progressively closer to the channel downstream is similar for communities dominated by Imperata cylindrica and Pycreus nitidus suggesting that environmental gradients (probably nutrient supply) perpendicular to the channel axis are steep and that they are mirrored by long-range environmental gradients downstream. An analysis of hydraulic characteristics of this distributary river system illustrates that channel width varies most with variation in discharge, while channel depth and current velocity are relatively constant over the range of discharges in the study area. Since channel width is primarily a consequence of vegetation processes in the channel margin, especially the growth of the giant sedge C. papyrus it is clear that channel hydraulics are affected largely by vegetation.

Vegetation restoration was attempted in four plots of a degraded wet heath overgrown by Molinia caerulea in High Ardenne (Belgium). Two treatments, mowing for two years and removal of the top 3–28 cm of peat, were applied in spring 1989. The vegetation was recorded in 1989 and 1998 using the Braun-Blanquet method. After nine years, the mowing treatment had relatively little effect on vegetation composition. We observed a 0–25 % decrease of Molinia cover and an increase of some heath species like Calluna vulgaris (12–47 %) and Erica tetralix (0–12 %). However, top peat removal had a pronounced and beneficial effect. A decrease of a mean of 66 % in cover of Molinia caerulea was observed as well as an increase of the cover of Erica tetralix (0–12 %). Peat removal also promoted the re-establishment of some typical wet heath species like Juncus squarrosus and Carex panicea, as well as of some rare pioneer species like Drosera rotundifolia and Lycopodiella inundata. This treatment appears to be favorable for the regeneration of degraded wet heaths in High Ardenne.

A tissue culture and plant regeneration protocol for the salt marsh grass, Spartina alterniflora, has been developed. Callus was efficiently induced on Murashige and Skoog (MS) medium supplemented with 1 mg L⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) and 1 mg L⁻¹ indole-3-acetic acid (IAA). Callus initiation from 6-day-old seedlings was faster and occurred with a greater frequency than callus initiation from coleoptile-covered segments from the same age seedlings. However, only the coleoptile-covered segments produced regenerable callus, which was maintained on MS medium supplemented with 1 mg L⁻¹ 2,4-D and 1 mg L⁻¹ naphthaleneacetic acid (NAA). The regenerable callus differentiated into shoots upon transfer to shoot regeneration medium. A high frequency of shoot regeneration was obtained when the medium contained 3 mg L⁻¹ 6-benzylaminopurine (BA) or Thidiazuron (TDZ), with or without the addition of 0.2 mg L⁻¹ IAA. Regenerated shoots were transferred to root regeneration medium, the optimal of which was determined to be half-strength MS medium supplemented with 1 mg L⁻¹ indole-3-butyric acid (IBA). TDZ in the shoot regeneration medium inhibited root formation in the root regeneration medium, making BA rather than TDZ the optimal hormone for the shoot regeneration medium. The mode of plant regeneration was organogenesis. Upon transfer to soil, the most successful growth of plants occurred in a mixture of commercially available potting soil and natural marsh mud. The development of a tissue culture and regeneration protocol for S. alterniflora provides the possibility of selecting lines of this species, via somaclonal variation, with characteristics desirable for wetland creation and restoration.

Alnus maritima (seaside alder) occurs in wet or flooded soils on the Delmarva Peninsula (southern Delaware and adjacent counties of eastern Maryland, USA) and in small niches in Georgia and Oklahoma. Although some A. maritima exist in coastal estuaries, responses of the species to salt, and whether salt resistance depends on provenance of plant origin, are not known. We first compared salt injury among A. maritima from all provenances irrigated with dilutions of ocean water. Seedlings from the three provenances responded similarly. Salinity up to 3.1 g/kg did not alter stem elongation but did cause increases in the ratio of dry to fresh weight of basipetal leaves, which reflected their necrosis. Photosynthesis and growth after treatment with salt then were compared among A. maritima and four other woody species: Baccharis halimifolia, Ceanothus americanus, Myrica cerifera, and Cornus amomum. Irrigation solutions with up to 12 g/kg salinity had no effect on B. halimifolia and caused no visible damage to M. cerifera. Ceanothus americanus showed foliar necrosis and decreases in photosynthesis at 3, 6, and 12 g/kg. Photosynthesis of A. maritima and C. amomum was sustained after irrigating with solutions at 3 g/kg but was reduced by 6 and 12 g/kg salinity. Our third experiment showed a more pronounced decrease in photosynthesis as salinity increased for A. maritima with roots partially or totally inundated in solutions with salt compared to plants irrigated but not inundated with these solutions. Lastly, symptoms of salt injury among A. maritima planted at locations that differed in salinity along the Broadkill River, an estuary in Delaware, were found to be similar to those we documented among plants treated in a greenhouse. We conclude that necrosis of basipetal leaves is the most apparent symptom of injury caused by salt in the root zones of A. maritima, that low concentrations of salt can lead to damage, and that the rate at which symptoms develop in this riparian species varies with the extent of root-zone inundation with salt water. Alnus maritima was less sensitive than C. americanus to salt but was considerably more sensitive than B. halimifolia and M. cerifera.

In Far East Asia, coastal dune forests dominated by the conifer Picea glehnii represent a rare plant community type. A P. glehnii forest and adjacent plant communities on the dunes of the Syunkunitai sand spit, Hokkaido, northern Japan were examined. Using the basal area of P. glehnii and Abies sachalinensis stems measured in a belt transect across a portion of the sand spit, we identified three plant community zones: SALT MARSH, PICEA, and ABIES. The three zones were distributed along a topographic gradient that was associated with differences in water table depth, salinity, and pH of soil pore water. Nearly pure stands of P. glehnii grew on a relatively level portion of the sand dune where the ground-water-table level was shallow (−10.9 to −26.3 cm, without isolated depressions). The salinity of the soil pore water was significantly lower than that in the adjacent salt marsh (Dunnett's T3, P = 0.047). The A. sachalinensis community grew on the upper slope and ridge of the dune where the ground-water-table was significantly lower (P = 0.003) than in the P. glehnii forest. Our results show that the boundary between the P. glehnii forest and the salt marsh community is determined primarily by the salinity of the soil pore water, whereas the boundary between the P. glehnii and A. sachalinensis forests is determined by the ground-water-table depth and the pH of the soil pore water. Because of continual ground subsidence, the salt marsh community and P. glehnii forest will likely be submerged within 50 and 100 years, respectively.

Wetlands in the Prairie Pothole Region of North America are harsh environments for fish, and only two planktivorous species are common in these ecosystems: fathead minnows (Pimephales promelas) and brook sticklebacks (Culaea inconstans). Given their similarities, competition between these species may be high, especially for food resources. We assessed potential competition between fathead minnows and brook sticklebacks, as well as their influence on zooplankton communities, by measuring their selectivity for zooplankton prey in controlled laboratory experiments. Minnows and sticklebacks of varying size were placed in aquaria with mixed zooplankton assemblages to assess selectivity for copepod and Daphnia prey. Sticklebacks of all sizes showed strong selectivity for Daphnia, while minnows were less selective, and prey selectivity varied with fish size. Selectivity of prey was not related to relative prey abundance for either minnows or sticklebacks. Although minnows were less selective, their mass-specific consumption rates were significantly lower than consumption rates for sticklebacks. Our results indicated that effects of predation on zooplankton may differ between these two fish species, with minnows potentially affecting greater numbers of taxa. Additionally, generalist feeding on zooplankton prey by fathead minnows may be advantageous in habitats with low Daphnia densities, as is common in prairie wetlands with dense fish populations.

A 9.9-ha constructed wetland designed to reduce nitrogen in municipal wastewater following conventional secondary treatment began operating in southern California's San Jacinto Valley in September 1994. The wetland incorporated zones of bulrush (Schoenoplectus acutus and S. californicus) for effluent treatment, plus areas of 1.8-m deep open water and other features to benefit wintering waterfowl. A one-year long program to monitor bird use and evaluate their contribution to loadings of nitrogen and phosphorus was initiated seven months later and a second, four-month long period of monitoring was initiated after a 20-month hiatus. Daily bird use peaked at nearly 12,000 individuals during the second period. Estimates of maximum daily nitrogen and phosphorus input by birds were 139 g N ha⁻¹ day⁻¹ and 56 g P ha⁻¹ day⁻¹. Following a reconfiguration of the wetland that increased the area of open water, a third year-long period of monitoring was initiated in September 2000. Estimated maximum daily loading attributable to birds during this period reached 312 g N ha⁻¹ day⁻¹ and 124 g P ha⁻¹ day⁻¹. These levels represent only 2.6% and 7.0%, respectively, of the mean daily loads of N and P in inflow water from the wastewater-treatment plant. Wintering waterfowl contributed the most to nutrient loading, but the numerically dominant species was the colonial Red-winged Blackbird (Agelaius phoeniceus). The wetland's nutrient-removal efficiency was negatively correlated to bird loading. However, the greatest bird loading occurred during November to March, when winter conditions would reduce microbial nutrient-removal processes and plant uptake in the wetland. Multiple regression analysis indicated that variation in nutrient removal efficiency over a one-year period was best explained by wetland water temperature (R² = 0.21) and that little additional insight was gained by adding bird loading and inflow nutrient load data (R² = 0.22). This case study supports the concept that a constructed wetland can be designed both to reduce nutrients in municipal wastewater and to provide habitat for wetland birds.

Data acquired by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) with 224 bands, each with 0.01-μm spectral resolution and 20-meter spatial resolution, were used to produce a vegetation map for a portion of Everglades National Park, Florida, USA. The vegetation map was tested for classification accuracy with a pre-existing detailed GIS wetland vegetation database compiled by manual interpretation of 1:40,000-scale color infrared (CIR) aerial photographs. Although the accuracy varied greatly for different classes, ranging from 40 percent for scrub red mangroves (Rhizophora mangle) to 100 percent for spike rush (Eleocharis cellulosa) prairies, the Everglades communities generally were successfully identified, averaging 66 percent correct for all classes. In addition, the hyperspectral image data proved suitable for detecting the invasive exotic species lather leaf (Colubrina asiatica) that is sometimes difficult to differentiate on aerial photographs. The findings from this study have implications for operational uses of spaceborne hyperspectral image data that are now becoming available. Practical limitations of using such image data for wetland vegetation mapping include inadequate spatial resolution, complexity of image processing procedures, and lack of stereo viewing.

The term nursery implies a special place for juvenile nekton (fishes and decapod crustaceans) where density, survival, and growth of juveniles and movement to adult habitat are enhanced over those in adjoining juvenile habitat types. We reviewed recent literature concerning these four topics and conducted meta-analyses for density and survival data. Most studies of mangroves as nurseries have addressed only occurrence or density of fishes or decapods, have not used quantitative sampling methods, and have not compared alternate habitats. Comparison of nekton densities among alternate habitats suggests that, at times, lower densities may be typical of mangroves when compared to seagrass, coral reef, marsh, and non-vegetated habitats. There is little direct consumption of mangrove detritus by nekton. C, N, and S isotope studies reveal little retention of mangrove production by higher consumers. Densities of prey for transient fishes and decapods may be greater within mangroves than elsewhere, but there has been no verification that food availability affects growth or survival. Experimental evidence indicates that mangrove roots and debris provide refuge for small nekton from predators, thus enhancing overall survival. There is no evidence that more individuals move to adult habitats from mangroves than from alternate inshore habitats. There is an obvious need to devise appropriate experiments to test the nursery functions of mangroves. Such data may then be one more reason to add support for mangrove conservation and preservation.

In earlier greenhouse and field studies, we found that upper leaves of Phragmites australis (common reed) and Spartina alterniflora (cord grass) tended to have lower levels of metals than lower leaves. Since lower leaves are produced earlier in the season and are older than upper leaves, there are two possibilities: (1) leaves produced earlier in the season have more metals than those produced later and/or (2) individual leaves continue to accumulate metals during their lifespan. We tested these two hypotheses by numbering all leaves as they emerged from both species of plants growing in Cu-, Pb-, or Zn-contaminated vermiculite in a greenhouse. We removed tissue from the new odd-numbered leaves for metal analysis, and then analyzed the remaining half-leaves later in the season when they had senesced. We could thus compare initial and final metal levels in individual leaves and compare the final metal levels in leaves that emerged early (low numbered leaves) with those that emerged later. We found that hypothesis 2 was supported, since initial levels in individual leaves tended to be lower than the final levels. Hypothesis 1 was not generally supported for either species. We also found very great variation in both initial and final metal levels in leaves on the same plant and in different plants of the same species exposed to the same metal concentration. This suggests that scientists who are sampling leaves of these species in the field should collect many leaves and pool them to get accurate data, since individual leaves are not representative of the plant as a whole.