Habitat use of breeding diving ducks is not well-documented. I studied nesting and brood-rearing female redheads (Aythya americana) in southwestern Manitoba during 1994 and 1995 to document habitat use and associations between wetland characteristics and reproductive success. Most females nested in small, semi-permanent wetlands and were successful in wetlands with large bands of emergent cover. Success was associated with water depth at the nest and distance between the nest and dry land. Brood-rearing females switched from smaller wetlands used for nesting to larger, semi-permanent wetlands. Successful females selected appropriate habitat whereas unsuccessful females showed no preferences. These results support a landscape approach to wetland management and emphasize the need for plans that reduce impact to wetland margins.

National Wetland Inventory (NWI) maps are widely used in the United States but have not been independently evaluated in the Great Lakes region nor in forested areas with level topography. Field data from 148 plots in the Hiawatha National Forest ecological classification and inventory program were combined with an additional review to evaluate NWI mapping accuracy. NWI maps were over 90% accurate in identifying uplands and jurisdictional wetlands. All nonforested wetlands were identified correctly. Uplands were correctly identified 96.9% of the time. The lowest level of accuracy, 90.7%, was achieved in identifying forested wetlands. The most common error was the NWI classification of wetlands on the AuGres soil series, a somewhat poorly drained upland soil that often occurs in complexes with wetland soils in the region. Forested wetlands with a cover type similar to adjacent uplands were also a source of error on NWI maps. The already high accuracy of NWI maps could be improved by the mapping of wetland–upland complexes, a development corresponding to the increased mapping of hydric-nonhydric soil complexes in area soil surveys. The continued refinement of regional lists of hydrophytic vegetation is supported by indicator status discrepancies between an extensive Hiawatha National Forest database and the current NWI list for the region.

Resource managers confronted with preserving ecosystems for prairie wetland birds in fragmented landscapes require landscape studies that direct conservation efforts over broad geographic regions. We investigated the role of local and landscape factors affecting habitat suitability by integrating remotely sensed wetland and land-cover data with wetland bird habitat models. We linked habitat models with locations of easement and fee-title wetlands to evaluate spatial location and extent of protected, suitable habitat. We also simulated impacts of the loss of small wetlands on suitability of larger wetlands for mobile species that use multiple wetlands. Lastly, we evaluated the efficacy of waterfowl habitat programs in preserving suitable habitat for nongame wetland bird species to recommend strategies for maximizing regional landscape connectivity. Regional databases constructed for this study indicate that easement and fee-title tracts encompass 13.9% (1.2 million ha) of land area and protect 19.8% of the wetlands in eastern South Dakota, USA. Proportion of protected wetlands is highest for semi-permanent (32.3%), intermediate for seasonal (25.6%), and lowest for temporary wetlands (15.8%). A stratified, two-stage cluster sample was used to randomly select 834 semi-permanent and seasonal wetlands that were surveyed for birds in 1995 and 1996. Logistic analyses indicate that habitat suitability for some species (e.g., Virginia rail, pied-billed grebe) is related to local vegetation conditions within wetlands, while suitability for others (e.g., northern pintail, black tern) is related to landscape structure at larger scales. As a result, unfragmented prairie wetland landscapes (i.e., areas with wetland complexes embedded within upland grasslands) provide habitat for more species than isolated wetlands in tillage fields. Models developed from survey wetlands were used to classify habitat suitability for all semi-permanent and seasonal wetlands in eastern South Dakota. Small wetlands are critical components of the surrounding landscape that influence habitat suitability of larger wetlands. Models used to reclassify suitability of larger remaining wetlands after small wetlands (<0.5 ha) were removed indicate that species most vulnerable to loss of small wetlands are vagile species that exploit resources over broad spatial scales. Number of wetlands suitable for northern pintails, a mobile species that uses multiple wetlands within a season, decreased 20.7% when wetlands <0.5 ha were removed. Historic paradigms dictating waterfowl habitat protection efforts also have conserved habitat for nongame bird species. Modern paradigms that acknowledge the importance of small shallow wetlands to breeding waterfowl have shifted the focus of protection towards preserving habitat for species that occupy more abundant seasonal wetlands. Cessation of protection efforts would result in further fragmentation of regional wetland landscapes. We recommend that wetlands be acquired not only to consolidate suitable habitat within protected core areas but also to ensure that core areas coalesce to preserve connectivity among regional wetland landscapes.

The Kyoto Protocol accepts terrestrial sinks for greenhouse gases (GHGs) as offsets for fossil fuel emissions. Only carbon sequestered in living biomass from re- and afforestation is presently considered, but the Protocol contains a provision for the possible future inclusion of other land uses and soils. As a result, the possibility of sequestration of carbon in wetlands, and particularly peatlands, is being discussed. Natural peatlands are presently a relatively small sink for CO₂ and a large source of CH₄: globally, they store between 400 and 500 Gt C. There are large variations among peatlands, but when the “global warming potential” of CH₄ is factored in, many peatlands are neither sinks nor sources of GHGs. Some land-use changes may result in peatlands acting as net sinks for GHGs by reducing CH₄ emissions and/or increasing CO₂ sequestration (e.g., forest drainage), while other land uses may result in large losses of CO₂, CH₄, and N₂O (e.g., agriculture on organic soils, flooding for hydroelectric generation). Other land uses, such as peatland creation and restoration, produce no net change if they are replacing or restoring a previous level of GHG exchange. These are analogous to reforestation of deforested areas. On closer examination, the inclusion of peatlands in a national greenhouse gas strategy as sinks, despite their large role in the terrestrial carbon cycle, may not significantly reduce net greenhouse gas emissons. If the sinks are to be considered, it is reasonable that terrestrial sources associated with all land uses on peatlands also should be considered. If peatlands are not considered explicitly, but soils in forest and agriculture systems are included in the Kyoto Protocol in the future, then those peatlands impacted by these land uses will be incorporated implicitly.

Peat harvesting has altered site water and peat chemistry at the Seba Beach peatland through removal of surface bog peat, moving the site back in the fen-to-bog succession time sequence. The post-harvested site is more similar to a moderate-rich fen in water and peat chemistry than the bog that it was originally. The exposure of fen peat has resulted in significantly higher concentrations for almost all water and peat chemical components compared to the neighboring natural bog. During five years of sampling this study found no significant differences between years in the water and peat chemistry within the natural area. A few significant yearly differences were found in the harvested area water chemistry, while the harvested area peat chemistry had many significant yearly differences. Several patterns were noted in the nitrogen concentrations in the harvested field. First, the harvested site had significantly higher concentrations of aqueous NH₄ -N and NO₃^--N, as well as available NO₃-N in the peat, compared to the neighboring natural area. A variety of possible factors, such as increased aeration, high pH values, and low vegetation cover may account for these high nitrogen concentrations. Second, peat nitrogen concentrations seem to be affected by soil moisture. Harvested areas with high soil moisture had high concentrations of available NH₄-N and lower available NO₃-N concentrations, while drier areas had high concentrations of available NO₃-N and lower available NH₄-N concentrations. Third, the concentrations of these nutrients in the harvested area did not remain static over the years. In the peat, available NO₃-N concentrations were significantly reduced in 1995, and in the well samples, NH₄ -N was significantly reduced in 1994 and 1995 compared to earlier years. This research shows that the chemistry of the harvested site has significantly changed from the original bog ecosystem. As the site is more similar to a moderate-rich fen, ombrotrophic bog species are unlikely to thrive on this site.

Zooplankton structure and dynamics were studied in a freshwater wetland subject to strong hydrologic fluctuations. This wetland underwent a six-year drought that terminated at the end of 1996. At that time, inundation area and water level increased, diminishing macrophyte cover in some cases and enhancing a continuing eutrophication problem. Sampling was performed monthly from January 1996 to December 1998 in five shallow water sites. Zooplankton were a mixture of limnetic and littoral species (66 rotifer, 15 cladoceran, and 10 copepod taxa, plus unidentified oligotrichid and peritrichid ciliates), the composition of which changed coincident with the shift of the hydrologic conditions. The most common taxa were bdelloid rotifers and Lecane closterocerca. The microcrustaceans Ceriodaphnia dubia, Daphnia curvirostris, and Acanthocyclops robustus were frequent. Ciliates were the most important component of zooplankton in terms of biomass, except in spring when cladocerans were dominant. Rotifer biomass was the lowest fraction of zooplankton. When community structure was described by taxonomic classes, mean biomass, or time biomass trajectories, only weak spatial patterns were found following the flux of water in the wetland. Each zooplankton group was distinctly affected by flood. Ciliates and rotifers increased biomass after the flooding, possibly as a result of the enhancement of eutrophication; cladoceran populations decreased after the flooding likely due to macrophyte loss that facilitated planktivorous fish control. Copepods increased biomass consequent to the stabilized water level. There was a clear seasonal trend of zooplankton biomass seemingly unaffected by flood. Ciliates and rotifers had fluctuating low biomass in winter-spring, with maximum biomass in summer-autumn; cladocerans appeared and peaked only in spring; copepods peaked in late winter and spring.

Africa's numerous floodplain wetlands provide a host of hydrologic, ecological, economic, and social benefits. They play a fundamental role in supporting significant human populations. In common with all wetlands, the hydrology of Africa's floodplains is central to their functioning and in turn plays a key role in determining the benefits that they provide. The timing and extent of wet-season inundation are major influences upon the temporal and spatial distribution of floodplain resource use. Using results from intensive hydrologic surveys, supplemented by analyses of river flow data and flood extent maps, this paper delineates areas within the Hadejia-Nguru Wetlands of northeastern Nigeria according to their hydrologic characteristics. This delineation is used in combination with a land-use map derived from aerial and field surveys to examine the impacts of hydrology upon human activities and land use. The timing of different cultivation practices in the wetlands is shown to be in tune with the annual flood cycle. Rice is cultivated in inundated areas that are then planted with other crops after the floods recede. The intensity of fishing and cattle grazing also varies with the pattern of rising and falling water levels. The distribution of major land uses is strongly influenced by spatial variations in hydrologic characteristics. The location of rice cultivation and small-scale irrigation is determined by water availability in the wet and dry seasons, respectively. Extensive flood rice farms are found along the Jama'are River, which contributes over 70% of the river inflow to the wetlands. Within the Hadejia River system, important flood rice areas are the Madachi Swamp and the Marma Channel. The primary area of small-scale irrigation is along the Burum Gana River in which small, but year-round, flows are maintained by return flows from upstream irrigation schemes. This area, which covers only 13% of the land-use map, contains 48% of the area of small-scale irrigation. Extensive inundation seems to act as a barrier to human activities in some areas and is responsible for the maintenance of natural vegetation within central parts of the wetlands. Modifications to the hydrologic characteristics of some parts of the wetlands resulting from drought and upstream irrigation schemes have required local communities to adapt, with varying degrees of success, their modes of floodplain resource use. Farmers along the Burum Gana have embraced small-scale irrigation, while those along the Keffin Hausa River, which has all but dried up, have had no option but to concentrate on rain-fed agriculture. The strong inter-connections between hydrology, land use, and human activities dictate that any further hydrologic modifications should not be undertaken without a full appreciation of their potential impacts.

Strip transects located along roads are commonly used to estimate waterfowl populations and characterize associated wetland habitat. We used data collected in May and early June, 1995, on forty-five 40-km² plots in North Dakota to evaluate bias of 800-m and 400-m wide roadside transects for sampling wetlands relative to a larger (40-km²) scale and to compare duck abundance at the two widths. Densities of all basins combined and of seasonal basins considered alone were biased high for both transect widths, but mean bias did not differ from zero for temporary or semipermanent basins. Biases did not occur when excavated seasonal and temporary basins (i.e., road ditches) were excluded from the sample. Mean basin density was higher for the inner (400-m) transect width than for the outer transect width (area remaining of the 800-m transect, outside of center 400-m width) for all basins combined and for seasonal and temporary basins. We detected an area-related bias in the occurrence of basins in transects: smaller basins (0.08–1.6 ha) were over-represented in transect samples by 2.9–6.5%, and larger basins (≥11 ha) were under-represented in 800-m transects by 7.3% and in 400-m transects by 16.3%. We compared the distribution of ducks relative to water conditions in the inner and outer transect widths to evaluate whether they were affected by proximity to the road. Mallards (Anas platyrhynchos L.), northern pintails (A. acuta L.), and gadwall (A. strepera L.) responded to water conditions equally in the inner and outer transect widths, but northern shovelers (A. clypeata L.) and blue-winged teal (A. discors L.) responded more strongly to wetlands on the inner than the outer transect width, indicating that estimates of these species would be higher from a 400-m wide transect than from an 800-m wide transect. Differences in an adjustment index, used to account for the portion of basin obscured from view, were highly variable between inner and outer transect widths but did not indicate that use of wider transects was hampered by visibility. Biases of transect sampling need to be carefully considered when extrapolating wetland basin or duck densities from transects to larger landscape scales.

Wetlands are created to compensate for the loss of natural wetlands as a result of human land-use activities. How well these constructed wetlands mimic natural wetlands is in debate. The goal of this study was to compare soil and other environmental conditions within constructed and adjacent reference wetlands to assess the progress of the constructed wetlands towards a functional wetland. Three constructed wetlands in Virginia, USA, 4 to 7 years old, were paired with adjacent palustrine forested and scrub-shrub reference wetlands to examine differences in topography, hydrology, soil properties, and other environment conditions such as soil temperature and redox potential. Degree of microrelief was greater in reference wetlands than in the associated constructed wetlands. Seasonal fluctuations in water-table levels were similar in both wetland types. Two of the paired wetlands showed considerable differences (15 to 20 cm) in the depth to the water table. Redox potentials were similar in reference and constructed wetlands. Paired wetlands with water-table levels at or near the soil surface throughout the year showed similar soil temperatures. At the site where the summer water levels were 80 to 100 cm below the soil surface, summer temperatures were substantially higher in the poorly shaded, constructed wetland. At the two sites with high water-table levels throughout the year, percent clay and silt, levels of organic C and N, and cation exchange capacity were significantly greater (p <0.05) in the reference wetlands. At the drier site, only 3 of the 16 soil parameters compared were significantly different. In this limited study, observed differences in soil and other environmental conditions between paired wetlands suggest that constructed wetlands may not function in the same capacity as adjacent reference wetlands.

Denitrification measurements were made under simulated field conditions using sediment cores and water collected from the Hemet/San Jacinto Multipurpose Demonstration Wetland (Riverside County, California, USA). The 9.9 ha constructed wetland is used to both polish ammonia-dominated secondary municipal effluent and provide migratory bird habitat. The wetland was originally constructed as a marsh-pond-marsh system in 1994. Over the period from January through March 1998, measured denitrification rates averaged 20.9 ± 20.9 μmol N m⁻² h⁻¹ within the emergent marsh portions of the wetland and 646 ± 353 μmol N m⁻² h⁻¹ in open water areas. The mean areal denitrification removal rate for this period was 0.70 kg N ha⁻¹ d⁻¹, which accounted for about 8% of the total N removed by the wetland. Internal retention was the main N-removal mechanism. Synoptic water quality surveys indicated that denitrification was limited by a lack of nitrification within the wetland. Between April 1998 and January 1999, the wetland was reconfigured as a hemi-marsh system, having equal areas of interspersed emergent marsh and deep open water. In May 1999, measured denitrification rates averaged 1414 ± 298 μmol N m⁻² h⁻¹ within the emergent marsh zones and 682 ± 218 μmol N m⁻² h⁻¹ in the open water areas. The mean areal denitrification removal rate was 3.58 kg N ha⁻¹ d⁻¹, which accounted for 40% of the total N removed by the wetland. A synoptic water quality survey indicated that nitrification within the wetland had been enhanced by the reduction of emergent macrophyte biomass and the increase in the area of interspersed deep open water. The modifications to the wetland shifted the nitrogen balance from a large internal storage component and a small denitrification component in 1998 to a more denitrifying system in 1999.

In the early 1900s, baldcypress swamps were harvested en masse in coastal Louisiana, USA. In many areas, natural regeneration did not occur; instead, these areas converted to marsh or open water. One of the factors that may have been responsible for the lack of regeneration was shading of newly-germinated seedlings by herbaceous vegetation. Alternatively, prolonged flooding or complete submergence may have suppressed germination or growth rates of young seedlings and even caused mortality. This study investigated the effects of complete submergence and variable light regime on two age classes of baldcypress seedlings. Newly-germinated seedlings (under two weeks of age) subjected to complete submergence began to show clear signs of stress after approximately one month and substantial mortality following 45 days of submergence. In contrast, one-year-old seedlings submerged for as much as five months experienced up to 75% survival. In a four-way factorial experiment, two age classes of baldcypress seedlings were subjected to five light transmissions (100%, 80%, 50%, 30%, 20%), five flood durations (0 days, 14 days, 25 days, 35 days, 45 days), and two nutrient regimes (fertilized vs. not fertilized). At 100% light transmission, the newly-germinated seedlings suffered complete mortality after 35 days of submergence, whereas the one-year-old seedlings were largely unaffected by prolonged flooding or light regime. Fertilized one-year-old seedlings that were submerged for an entire month had considerably greater growth in height and diameter than seedlings grown under mesic conditions without fertilizer. This is particularly important in coastal Louisiana because several re-introductions (i.e., diversions) of Mississippi River water into declining swamps are planned or underway, and these diversions will periodically increase nutrient and flood levels.

Seasonal forest ponds (SFPs) are isolated, ephemeral lentic habitats in upland forest ecosystems. These ponds occur commonly throughout temperate forests. Faunal communities of these ponds are dominated by invertebrates. Composition of these communities varies temporally both between years and also seasonally within a single hydrologic year, composition is most affected by pond permanence or hydroperiod. Benthic macroinvertebrates (BMIs) were sampled up to three times a year in five SFPs between 1994 and 1996. The ponds were of short, intermediate, and long hydroperiod. Hydroperiod also varied among years, based on precipitation patterns. During the study, 64,000 specimens of 57 taxa were collected. No pattern was identified in the variation of BMI abundance among years and pond hydroperiod; abundance increased with successive surveys within years. Taxon richness and diversity varied significantly with pond hydroperiod, increasing with increasing hydroperiod. Diversity measures increased over the three years of the study but without obvious pattern across the successive surveys within years. Insects dominated the samples, but large numbers of other Arthropoda and Oligochaeta were also collected. Chironomidae were dominant in most ponds, years, and surveys; chironomid dominance was significantly greater in shorter hydroperiod ponds. Seasonal forest ponds function as aquatic islands in a “sea” of terrestrial forest. The effect of hydroperiod on the composition of the benthic macroinvertebrate community is analogous to that of size on marine island fauna, longer hydroperiod ponds generally have richer invertebrate communities just as larger marine islands typically have richer faunas. However, the effect is confounded by the close relationship between pond hydroperiod and pond size/volume.

We related macroinvertebrate community structure to physical, chemical, and biological gradients in flow-through constructed wetlands receiving secondarily treated domestic wastewater and lower-nutrient river water in Ohio, USA. Macroinvertebrates collected with benthic colonization plates and emergence traps were analyzed with diversity, biotic, and combination indices and related to seventeen parameters of water quality, substrate characteristics, and primary productivity in both wetland systems. A total of 36 and 39 macroinvertebrate taxa were collected in the wastewater wetland and river wetland, respectively. Invertebrate communities nearest to the wastewater source in the wastewater wetland had significantly lower (mean ± SE) Simpson diversity (0.5 ± 0.13) and Invertebrate Community Index (ICI) scores (2.6 ± 0.8) than those of other sampling locations. Sampling locations near the middle and outflow of the wastewater wetland had diversity scores (0.84 ± 0.01) and ICI scores (4.8 ± 0.7) statistically similar to sites in the river-fed wetlands. Average diel dissolved oxygen and specific conductivity were the best environmental predictors of invertebrate community metrics; these variables along with chemical oxygen demand and nitrate-nitrogen described nearly 90% of the ICI variation in a four-predictor regression model. Multiple correspondence analysis showed sampling locations loosely grouped by average diel dissolved oxygen, which described 65.4% of the overall variation in the gradient data, and specific conductivity, which described and additional 16.4%. Macroinvertebrate analyses are presented as a valuable means of assessing the ecological status of wetlands used to improve water quality and as an important supplement for traditional chemical analyses.

Twenty-eight legume species (14% Caesalpinieae, 29% Mimosoideae, and 57% Papilionoideae) were found growing actively in the wetlands and riversides of Guadeloupe. Only 11% of the checked species appeared not to be nodulated after repeated investigation in the field, and all belong to the Caesalpinieae tribe. The legume distribution brings out the importance of this family in the wetlands in terms of abundance of legume trees and shrubs. In wet meadows, herb and liana legumes have low cover and species richness, allowing the Poaceae to dominate. Of the 19 species of trees and shrubs, 17 have shown efficient N-fixing symbiosis in natural conditions. N-fixing legume predominance seems to be a biotic characteristic that recurs in perennial plant communities of flooded habitats. Efficient N-fixing symbiosis under flood conditions is achieved through various nodulation strategies including (i) waterlogging tolerance with aquatic nodules associated with aerenchymateous tissue, (ii) seasonal avoidance brought about by short-lived determinate nodules, and (iii) spatial stress avoidance with aerial nodules developing on root, plank buttress or stem.