Aquatic invertebrates are essential to wetland function, serving as the key trophic link between primary producers, fish, and waterfowl in boreal wetlands. We studied how both aquatic vegetation complexity and prevalence, and fish presence, could be used to predict the distribution of invertebrate biomass in 24 wetlands of the Western Boreal Forest (WBF). The percent volume occupied by aquatic plants was significantly positively associated with overall invertebrate biomass per liter (P = 0.009). Particular invertebrate functional feeding groups were correlated with types of aquatic macrophyte architecture; herbivorous invertebrate biomass (mg/L) was greater in more complex aquatic environments, and predatory invertebrate biomass was greater in environments with simple plant architecture. Wetlands inhabited by Brook Stickleback (Culaea inconstans) had reduced invertebrate biomass of the predatory, non-predatory (excluding omnivores), and gatherer/collector functional feeding groups. Gatherer/collector, predator, shredder, and piercer invertebrate groups were negatively correlated with dissected leaved plant dominance in those wetlands without fish. These invertebrate groups comprise the bulk of invertebrate protein available to nesting hen mallards and their ducklings. We suggest that the presence of stickleback and/or dominance of dissected leaved plants in the wetlands of the WBF results in decreased food supply for hatchling waterfowl.

Riparian spider abundance is influenced by the extent and architecture of litter, which is greatly influenced by flood regime. Flood-deposited clumps of intertwined plant material and inorganic debris (“litter hovels”) attached to trees and elevated above the ground by past high water events present a unique, persistent, and unstudied habitat type for spiders. We investigated spider use of litter hovels along an unregulated reach of West Clear Creek, Arizona, USA dominated by native riparian vegetation. Ninety two percent of litter hovels were occupied by at least one spider, with a mean occupancy of 4.5 spiders per hovel. Spider abundance and diversity at the family level were positively correlated with litter hovel size. Furthermore, spiders were non-randomly distributed among litter hovels in three areas of this riparian system: the vegetated floodplain, creek edges, and islands within the creek channel. Overall spider diversity was two-fold greater on creek islands than in the vegetated floodplain, and spider abundance also varied by predation guild among the three habitat types. Running and web-building spiders were most abundant on creek islands, while stalking and ambushing spiders were two-fold more abundant along creek edges in comparison with other habitats. For this riparian system, we estimate that spider densities could reach 270,000/ha in hovels alone, and therefore alteration of flood regimes through stream management may have important implications for arthropod dynamics. Current efforts to restore natural flood regimes and native vegetation in Southwestern streams are likely to benefit spider populations, their predators, and the regulation of herbivorous arthropods.

Minerotrophic sedge fens are common in sub-arctic regions and are a significant source of atmospheric methane (CH₄), yet they have received less attention than other peatlands, such as boreal ombrotrophic bogs, which are smaller sources of CH₄. At the process level, CH₄ fluxes in sub-arctic systems are limited primarily by cold temperatures, and thus are sensitive to potential climate change. This study examined CH₄ dynamics in a temperate sedge-fen to determine controls on the spatial and temporal variability in CH₄ fluxes and, therefore, how the biogeochemistry of CH₄ in sedge-fen peatlands may respond to predicted changes in climate. We used flux chambers and laboratory peat incubations over a six to seven-year period (1994–2000) to study fluxes, pools, and potential production of CH₄ in a peat-forming wetland in central New York State, USA. Results showed that precipitation (i.e., dry years and depth to water table) exerted an important control on annual and seasonal patterns of CH₄ fluxes. Mean summer flux rates ranged from 2258 nmol m⁻² s⁻¹ in the wettest year to −934 nmol m⁻² s⁻¹ (net consumption) in the driest year. CH₄ concentrations in the surface peat were as low as 0.01 μatm and as high as 10 matm in the summer months depending on precipitation patterns. In contrast, CH₄ concentrations were consistently two to three times greater in sub-surface than in surface peat, and pools persisted during dry years and were temporally less variable. Fluxes were only weakly associated with potential CH₄ production rates, which showed little seasonal variation. In-vitro measurements of potential CH₄ production did not sufficiently explain fluxes, suggesting a need for improved in-situ methods for measuring CH₄ production. Site differences associated with different dominant vegetation had a significant effect on CH₄ cycling in all years except the driest, suggesting sensitivity to vegetation changes. These results indicate that predicting responses of fen peatlands to environmental requires an improved understanding of the underlying microbial processes and mechanisms that control CH₄ cycling.

Small, isolated wetlands in the Prairie Pothole Region of North America may be of critical importance to migrating shorebirds but are at high risk of drainage for agricultural production. We evaluated shorebird use of 1,181 temporary and seasonal wetlands within agricultural fields in the Drift Prairie physiographic region of North Dakota, USA over a 10-week period in spring of 2001. A total of 4,050 shorebirds of 25 species was observed on sampled wetlands. Shorebirds selected temporary wetlands that had water present during multiple visits, little emergent vegetation, large perimeters, and other wetlands in the surrounding landscape. Shorebirds were less likely to use wetlands showing evidence of drainage. Observed use of wetland basins suggests that small wetlands in the Prairie Pothole Region host millions of migrant shorebirds each spring. Continued existence of many of these wetlands may be threatened by a recent U.S. Supreme Court ruling that removed federal protection from certain isolated wetlands. Our results show the importance of current wetland protection provisions such as “Swampbuster” and other conservation practices of the United States Department of Agriculture Farm Program.

The effect of plant growth on surface and porewater concentrations of Fe, Mn, Cu, and S within a natural wetland receiving acidic spoil heap drainage was determined over a period of one year. Comparisons were made between unvegetated sites and those colonized by either Phragmites australis or Eriophorum angustifolium. The presence of vegetation increased surface and porewater concentrations of Fe and Mn in spring and summer largely due to the effects of higher evapotranspiration rates in vegetated areas. Microbiological processes were also thought to be important in controlling iron and sulfur concentrations at depth due to bacterial sulfate reduction and metal sulfide precipitation and iron and manganese concentrations close to the sediment surface due to bacterially mediated oxidation. These processes varied in importance with season due to changes in the dominant chemical and biological processes, although the complexity of the system prevented isolation of the principal mechanism involved.

This paper examines a southern Ontario kettle-hole peatland (Spongy Lake) to determine its hydrogeological linkage with local and regional water tables. The water table in the peat deposit and lake are perched 6 m above the regional aquifer, and there are strong lateral and downward hydraulic gradients. The horizontal hydraulic gradient (Δh/Δz) measured at the edge of the peatland ranged between 0.15 and 0.23 and the vertical gradient reached −1.24 (i.e., downward flow). At depths less than 1.0 m, saturated hydraulic conductivity (K_s) ranged from 10⁻⁷ to 10⁻⁵ m s⁻¹ and increased in magnitude with proximity to the peat surface. In an intermediate zone (1.0–4.0 m depth), K_s values ranged from 10⁻⁸ to 10⁻⁷ m s⁻¹, while deeper clay materials had K_s values ranging from 10⁻⁹ to 10⁻⁸ m s⁻¹. A clay layer directly below the deep peat limits downward seepage of water (one to two orders of magnitude less than evaporation). During periods of relatively high water, most seepage loss occurs laterally at the interface between mineral sediment and the peat. Spongy Lake is an important recharge zone for the regional aquifer, and the hydrologic and ecological integrity of the system should be protected.

Patterns of species diversity and community structure depend on scales larger than just a single habitat and might be influenced by the surrounding landscape. We studied the response of two insect families, mosquitoes (Diptera: Culicidae) and dytiscids (Coleoptera: Dytiscidae), to landscape variables at five spatial scales. We studied adult mosquito and dytiscid abundance, diversity, and species assemblages in relation to water permanence (area of permanent water bodies versus temporary wetlands) and forest cover (area covered by forest versus open land) within nested circles of 100 to 3000 m around trap sites in four wetlands in southern Sweden and in five wetlands in central Sweden. We found that mosquito abundance was greatest in areas with plentiful forest cover and a high proportion of temporary water, while most dytiscids favored open areas with a high proportion of permanent wetlands. However, diversity of both mosquitoes and dytiscids was positively correlated with high permanence and little forest cover. Mosquito species assemblages were mainly influenced by forest cover at a large spatial scale, whereas permanence was more important at local scales. Dytiscid species assemblages were mainly influenced by water permanence, especially at intermediate spatial scales. These results can be explained by the flight capability and dispersal behavior of mosquito and dytiscid species. The observed landscape associations of mosquitoes and dytiscids could be useful when creating new wetlands. Mosquito colonization could be reduced by creating permanent wetlands in an open landscape, which would favor colonization by dytiscids, a potential predator of mosquito larvae, while also supporting the diversity of both taxa.

Cirsium arvense and Lepidium latifolium are species that can aggressively invade wetland margins and potentially reduce biodiversity and alter ecosystem function. Although expansion of these species primarily occurs via rhizomatous growth, seeds are thought to be important in initial establishment. We conducted this study to investigate differences in seed germination of C. arvense and L. latifolium in montane wetlands of Colorado and Wyoming, USA. We used germination chambers to simulate environmental conditions (photoperiod, day/night temperature) during three periods of the growing season at each site and evaluated seed germination in relation to three soil moisture levels and two soil depths. A combination of shallow (<1 cm) seed burial and wet conditions resulted in the greatest germination probability of C. arvense (x̄ = 63.0%), 95% CI = 41.2–80.5%), whereas deep (2–3 cm) seed burial and saturated moisture conditions resulted in almost no germination (x̄ = 0.3%, 95% CI = 0.1–1.3%). The maximum germination probability of 44.0% (CI = 28.1–61.4%) for L. latifolium also occurred in the shallow burial and wet treatment; however, only effects of seed burial were significant (P < 0.05). The estimated mean germination probability of deeply buried seeds was <1.0% (CI = 0.3–1.4%) compared to 32% (CI = 19.7–47.9%) for shallowly buried seeds. Our results suggest that each species has the ability to germinate at similar rates throughout the growing season and across a large portion of the moisture gradient. This suggests that management actions, including water-level manipulations, at any time during the growing season may stimulate germination. Although burial of seed to depths of 2–3 cm reduced the germination potential of both species, the use of mechanical implements may be problematic in established stands because new plants of both species easily sprout from root buds. Further, disturbance resulting from such actions diminishes the density and vigor of other plants already present, which may ultimately decrease the competitive resistance of the disturbed environment to invasion by outside species. Detection of new invasions is a critical component of any integrated weed management program. Our results indicate that the incidence of C. arvense and L. latifolium germination is most likely in areas with seeds that are within 1 cm of the soil surface and soil moisture is 75–100% of field capacity for extended periods.

Wetlands provide important ecosystem functions and values, such as wildlife habitat, water filtration and flood protection. Wetland plant communities play a fundamental role in maintaining these functions but are thought to be increasingly threatened by human modifications of the landscape, such as deforestation and road construction. Here, we examine the quantitative relationships between two dependent variables (plant species richness, community composition) and a set of independent variables describing land use (e.g., forest cover, road density, and building density). As independent variables, we further include wetland characteristics that may be related to landuse practices (e.g., area and nutrient status). Wetland size is the most important predictor of both total plant species richness and the species richness within most functional groups. In addition, landscape properties, such as forest cover, presence of streams and nutrient status of water and sediment are significant predictors of plant species richness. Adjacent land use 250–300 m from the wetland affects plant diversity. Differences in the land-use-diversity relationship among different plant functional groups suggest that adjacent land use affects wetland plant communities in two important ways. First, it alters the abundance and distribution of propagules in adjoining habitats. Second, it alters the number of dispersal routes. Our results suggest that current management practices are inadequate and that regulation of adjacent land use is a critical component of wetland conservation.

Succulence, tissue chloride, bromide, and iodide levels were determined in the coastal salt marsh halophyte Salicornia virginica taken from three elevations over a 12-month period. Soil samples from each sampling area were also taken for the determination of halide concentrations. The average percent dry weight (% DWt) over the 12 months and three elevations ranged from 10.8 ± 0.4 to 16.1 ± 0.3 % (± sd), with a general increase in % DWt (decrease in succulence) in tissue from all elevations peaking in September, after the dry summer, followed by a decrease in % DWt (increase in succulence) during the rainy season. The mean halide levels in S. virginica tissues over the 12 months and three elevations ranged from 17.5 to 30.3 % Cl⁻, 0.27 to 0.76 % Br⁻, and from 3.00 to 1.21 × 10⁴ ppm I⁻. Mean halide concentrations in plant water ranged from 0.66 to 1.6 M Cl⁻, 4.6 to 12 mM Br⁻ and 3.3 μM to 16 mM I⁻. No environmental factors correlated with changes in tissue halide levels. Tissue Cl⁻ levels tended to increase during the dry summer months and decrease during the wet winter months. Bromide levels were more stable. Large increases in tissue I⁻ levels were found during the months of September and October when the plants were in flower, suggesting a developmental control of I⁻ uptake. Soil concentrations of all three halides at the low elevation were consistently higher than those in the middle and high elevations. The high elevation soil Cl⁻ was the most variable of the three halides. Higher I⁻ soil levels in the low elevation during the spring/summer as compared to fall/winter probably reflect an increase in the biological and chemical reduction of IO₃⁻ to I⁻. Tissue halide levels at the three elevations did not correlate with their respective soil concentrations. Plant water halide molar ratios were lower than in seawater and soil, indicating the selective uptake of halides in the order I⁻ > Br⁻ > Cl⁻.

Forested wetlands are important habitat for many bird species, but data about area and habitat relationships of birds in depressional (i.e., non-riverine) deciduous forested wetlands are scarce. Depressional forested wetlands are often surrounded by larger, continuous patches of upland forest, and it is not clear whether this surrounding forest should be considered part of the forested wetland. To contribute regional data to this question, we sampled birds and vegetation in depressional forested wetlands in southern Michigan, USA. Results indicated that the wetland per se should not be considered separate from the surrounding forest because forest area and forest characteristics were the most important predictors of richness and abundance of wetland-associated birds. Conversely, wetland area and wetland characteristics were important for some upland species. Because spatial clustering and model selection uncertainty are often encountered by wetland scientists, we describe analytical methods used to deal with these problems.

Wetland hydrology can be restored to soils that have been drained by plugging ditches to return the water table to its original elevation. Organic soils subside after drainage, and when ditches are plugged the restored water table may rise above the soil surface, killing newly planted vegetation. This study developed a method to estimate amounts of primary (settling) and secondary (oxidation) subsidence that could be applied to any organic soil. Primary subsidence was estimated from differences in bulk density between the drained and representative undrained sites. Secondary subsidence was estimated from accumulation of sand in the surface (Oap) horizons and changes in bulk density between oxidized and unoxidized organic horizons. Total subsidence was the sum of primary and secondary subsidence. Bulk density, particle size, and organic carbon data were gathered from one drained (Juniper Bay) and three undrained Carolina bay wetlands. Juniper Bay was drained with a network of ditches in three stages, 15, 20, and 30 years ago. Mean total subsidence was not significantly different (0.10 level) over time and averaged 121 cm for the three drainage periods. The mean rate of primary subsidence across the three drainage periods was 4 cm yr⁻¹, while secondary subsidence was approximately 2 cm yr⁻¹. Subsidence values were variable across Juniper Bay and were not related to distance from a field ditch. Restoration of the hydrology in Juniper Bay to pre-drainage water-table elevations could result in a water table that is >1 m above the existing soil surface.

The distribution of riparian plant species is largely driven by hydrologic and soil variables, and riparian plant communities frequently occur in relatively distinct zones along streamside elevational and soil textural gradients. In two montane meadows in northeast Oregon, USA, we examined plant species distribution in three riparian plant communities—defined as wet, moist, and dry meadow—along short topographic gradients. We established transects from streamside wet meadow communities to the dry meadow communities located on the floodplain terrace. Within each of the three communities, we sampled plant species composition and cover and monitored water-table depth and soil redox potential (E_h) at 10- and 25-cm depths through three growing seasons (1997, 1998, and 1999). The study objectives were (1) to characterize and compare seasonal patterns of water-table depth and soil redox potential in portions of the floodplain dominated by the three different plant communities; (2) to compare plant species composition, distribution, and diversity among the three communities; and (3) to relate plant species diversity and distribution to water-table depth and redox potential. Strong environmental gradients existed along the transects. Water-table depth followed the seasonal patterns of stream stage and discharge and was consistently highest in the wet meadow communities (ranging from 26 cm above the soil surface to −37 cm below the surface), lowest in the dry meadow communities (−8 cm to − 115 cm), and intermediate in the moist meadow communities ( 17 cm to −73 cm). Dynamics of redox potential were associated with the seasonal fluctuations in water-table depth and differed among the plant communities. In the wet meadow communities, anaerobic soil conditions (E_h ≤ 300 mV) occurred from March through July at 10-cm depth and throughout the year at 25-cm depth. In the moist meadow communities, soils were anaerobic during spring high flows and aerobic in summer and fall during low flows. In the dry meadow communities, soil conditions were predominantly aerobic throughout the year at both depths. Wet meadow communities were dominated by sedges (Carex spp.) and had the lowest species richness and diversity, whereas dry meadow communities were composed of a mixture of grasses and forbs and had the greatest number of species. Species richness and total plant cover were negatively correlated with mean water-table depth and positively correlated with mean redox potential at 10-cm and 25-cm depths (P < 0.01). Distribution of the 18 most abundant plant species in relation to water-table depth and soil redox potential showed that certain species, such as the obligate wetland sedges, occurred within a fairly restricted range of water-table depth, whereas other graminoids occurred over wide ranges. These results suggest that the biological diversity often observed in montane riparian meadows is strongly related to steep environmental gradients in hydrology and soil redox status.

Swamps dominated by the conifer Taxodium distichum var. nutans (pondcypress) are believed to develop into swamps dominated by a variety of hardwood trees (primarily bays), where organic matter accumulates and fires do not occur. To determine the validity of this long-accepted pattern of succession, relationships among basin characteristics, tree composition, hydrology, soils, and logging history were examined in nine pondcypress swamps and nine bay swamps in north central Florida. Basin depth was defined as the total of maximum standing water and organic matter depth. Shallow basins (< 65 cm) contained pondcypress-pine (Pinus elliottii) communities; prolonged drought and fire may control the importance of pondcypress within these basins. Medium basins (65–150 cm) ranged in tree species composition from pure pondcypress communities to pondcypress-swamp tupelo (Nyssa sylvatica var. biflora) communities to bay-cypress communities as organic matter depth increased and standing water depth decreased. Bay-cypress communities that had deeper organic matter than medium-basin pondcypress swamps also had low densities of large pondcypress trees and contained no pondcypress regeneration. Logging in medium-depth basins increased incidence of swamp tupelo and loblolly bay in pondcypress and bay swamps. Deep basins (>150cm) were dominated by bay communities that did not contain pondcypress. Abundant advance regeneration of loblolly bay (Gordonia lasianthus) suggests that this species eventually dominates undisturbed bay communities. Total basal area in pondcypress swamps was directly related to organic matter depth (r² = 0.53, p = 0.016, n = 9), suggesting that growth rate may also be related to this gradient. Productivity of pondcypress may be greatest in medium-basin pondcypress swamps, where deep organic matter leads to faster growth and deep standing water precludes the invasion of hardwoods. Pondcypress does not occur in deep basins. Basin geomorphology appears to play an important role in determining successional seres involving pondcypress and bay trees.

The hydrogeomorphic (HGM) approach to wetland classification and functional assessment was developed to facilitate the rapid assessment of wetland functions and support implementation of the 404 regulatory program in the U.S. This paper describes development of a functional assessment model for the hydrologic regime function of depressional wetlands on the Tennessee Highland Rim. Model output is a functional capacity index that ranges from 0 to 1 and indicates the level of alteration to the wetland hydrologic regime relative to the unaltered condition. The model initially includes four variables, each corresponding to an alteration type common in the study area. One variable reflects alterations to wetland morphology that increase or decrease storage capacity. Two variables reflect alterations to the wetland watershed that result in increased surface runoff. The remaining variable reflects changes in evapotranspiration losses resulting from timber harvesting. Model variable sensitivity and interaction are examined by simulating 47 years of hydrology for a single depressional wetland site. Based on the simulation of hypothetical alterations representing the range of conditions anticipated in the reference domain, three important variable interactions were identified and one variable eliminated from consideration. Several forms of the aggregation equation relating a functional capacity index to three model variables were tested by comparison to index values based on an independent quantitative measure that was simulated with a hydrologic model. Initial model forms, similar in form to many existing models, are improved by the addition of interaction terms and modification of variable weighting. This study demonstrates the utility of hydrologic modeling as a development tool for HGM functional assessment models. Even when limited field measurements are available for a rigorous calibration and validation, hydrologic modeling provides valuable insight into model variable sensitivity and interaction.

Patterns of nutrient circulation were examined to provide insight into the controlling mechanisms behind differences in aboveground net primary production (ANPP) among floodplain forest types. Geochemical and biogeochemical contrasts typical of many riverine forests are exemplified by the floodplains of the Satilla and Altamaha Rivers, blackwater and redwater river systems, respectively, located in Georgia, USA. Since floodplains possess high microtopographic variation, measurement plots were established to cover a range of topographic positions across both floodplains. Given the low nutrient and sediment loads that are characteristic of blackwater rivers, we hypothesized that the Satilla floodplain (SAT) would have lower ANPP and more efficient nutrient use efficiency (NUE). While both floodplains had similar amounts of litterfall production, the Altamaha floodplain (ALT) had greater stem production and, therefore, higher rates of ANPP. On the SAT, the relationship between litterfall mass and litterfall phosphorus (P) content, high P NUE, and high P resorption proficiency suggested that P was the primary limiting nutrient. While (N) circulation patterns were similar for the floodplains, ALT floodplain litterfall N/P ratios and N NUE suggested that N limitation was paramount there. Patterns of base cation circulation on the SAT indicated low calcium and potassium circulation and higher NUE of these elements compared to the ALT. In contrast, the Altamaha floodplain displayed low magnesium (Mg) circulation and high Mg NUE. Differences in P circulation and P NUE appeared to have the largest influence on ANPP between these eutrophic (ALT) and oligotrophic (SAT) floodplain forests. Furthermore, differences in base cation circulation and NUE suggested that biogeochemical distinctions between these two floodplain types could be made on the basis of base cation availability.

A major topic of discussion in community ecology is the relative influence of proximate seed sources and environmental variability on local plant species diversity. We investigated the effect of adjacent seed sources and environmental factors on initial plant species richness and composition in sixty wetland basins created in central Kansas, USA in 1998. We defined the adjacent seed source for each basin as the list of plant species found within a 10-m radius around each basin, filtered for those species capable of growing in wetland conditions. Basin water levels were monitored biweekly over three growing seasons, starting in 1999, as were soil moisture, temperature, and conductivity. Soil samples were analyzed for total nitrogen, total phosphorus, pH, and soluble salts in 2001. We found that in the three-year-old basins, the species richness of the adjacent areas had contributed significantly to basin species richness, as did basin area, soil pH, and water-level fluctuation. After three years, 61% of the species found in the adjacent areas were also found in the basins. While we found that proximate seed sources did influence initial species richness and composition in newly created wetlands, we cannot conclude that any differences in initial plant communities will ultimately result in different successional trajectories for the wetlands in our system. However, given the potential sensitivity of vegetation richness and composition in these newly created wetlands to proximate seed sources, the location of future wetland creations may need to be considered.

Clayey subsurface strata in precipitation-driven wetlands act as aquitards that retain water and can affect wetland hydrology. If the aquitard layers have been cut through by drainage ditches, then restoring wetland hydrology to such sites may be more difficult because of the need to fill ditches completely with low hydraulic conductivity material. Ground penetrating radar (GPR) surveys were conducted to determine the depth and continuity of shallow clay layers and identify those that have been pierced by drainage ditches at Juniper Bay, a 300-ha drained Carolina bay in North Carolina, USA that will be restored. Carolina bays are a wetland type that occur as numerous, shallow, oval-shaped depressions along the Atlantic Coastal Plain. The GPR interpretations found that moderately fine-textured (clay loam, sandy clay loam, silty clay loam) and fine-textured (sandy clay, silty clay, clay) aquitards underlay coarser-textured horizons in most of the bay at an average depth of 1.6 m. Extensive ground truthing showed that, on average, GPR predicted the depth to these aquitards to within 16% of their actual depth. An atypical GPR reflection in the southeast sector of the bay was interpreted as a fluvial deposit without aquitards until a depth of 3 to 5 m. This area may require different restoration strategies than the rest of the bay. By comparing the depths of aquitards and drainage ditches, several areas were identified as likely locations of ditch-induced aquitard discontinuity that may require filling or lining of suspect ditches to prevent potential water losses if there are downward hydraulic gradients. Cost estimates by two professional firms indicated that GPR could provide large volumes of data with cost and time efficiency. GPR surveys are proposed as a useful tool for characterizing potential wetland restoration sites on the Atlantic Coastal Plain and other regions with similar soils.

Wetlands in Torres del Paine National Park in Patagonia, Chile were studied to determine their variety and type because resident wetlands had not been previously described. In 2001, 88 wetlands were sampled for vegetation, water chemistry, water depth, substrate type, and hydroperiod to develop a classification system using a combination of factor, discriminant, and cluster techniques. In 2002–2003 the classification system was applied to an additional 323 wetlands. Types were named for floristic characteristics but were cross-typed with NWI and Ramsar classifications. Types described include Carex-Nothofagus, Juncus-Glyceria, Hippuris-Myriophyllum, Ranunculus, and Schoenoplectus marshes; peatlands; and vegas. Lake/ponds and mudflats were also identified. Wetlands were found in basins, slopes, and channels and have water regimes varying from saturated to permanently flooded. Differences were found in the chemical characteristics of water among wetland types and regions of the Park. Torres del Paine National Park is rich in its diversity of wetland types.

Slope wetlands generally occur at breaks in slope where discharging ground water maintains moist soil conditions. They often are found on the perimeter of highly permeable alluvial fans, but there have been no detailed hydrologic studies of these particular wetlands. We combined stream and spring flow measurements with five years of water-level and piezometric data to understand the hydrology of a 1.6 ha slope wetland at the base of a 5.2 ha alluvial fan in the central Rocky Mountains of Colorado. Step changes in streamflow inputs resulting from an upstream water diversion helped confirm the linkages inferred from the hydrometric data. Nearly 30% of the streamflow along a 180-m reach on the alluvial fan was lost to seepage. Discharge from two springs at the toe of the alluvial fan was eliminated and the piezometric head in the toe of the fan decreased by more than 80 cm within 1–2 days after the stream was diverted, indicating that stream seepage is the primary source of ground-water recharge for the alluvial fan. Streamflow and ground water discharging at the base of the alluvial fan were the primary wetland inflows, with summer precipitation playing a relatively minor role. Consequently, wetland water levels declined by up to 75 cm after the diversion began operating. The largest declines were in the lower part of the wetland, where surface sheet flow from the stream was the main water source. Continuing ground-water discharge into the upper part of the wetland limited the water level declines to less than 40 cm. The importance of streamflow as a water source distinguishes slope wetlands adjacent to alluvial fans from those found in other settings and makes them particularly vulnerable to upstream water diversions.

We examined data collected on fish assemblage structure among three differing floodplain types (broad, moderate, and narrow) during the 1993 flood in the unimpounded reach of the upper Mississippi River. This 500 year flood event provided a unique opportunity to investigate fish-floodplain function because the main river channel is otherwise typically disjunct from approximately 82% of its floodplain by an extensive levee system. Fishes were sampled during three separate periods, and 42 species of adult and young-of-the-year (YOY) fishes were captured. Analysis of similarity (ANOSIM) revealed a significant and distinguishable difference between both adult and YOY assemblage structure among the three floodplain types. Analysis of variance revealed that Secchi transparency, turbidity, water velocity, and dissolved oxygen were significantly different among the floodplain types. However, only depth of gear deployment and Secchi transparency were significantly correlated with adult assemblage structure. None of these variables were significantly correlated with YOY assemblage structure. The numerically abundant families (adult and YOY catches combined) on the floodplain included Centrarchidae, Ictularidae, and Cyprinidae. Both native and non-native fishes were captured on the floodplain, and several of the numerically abundant species that were captured on the floodplain peaked in catch-per-unit-effort 1–3 years after the 1993 flood event. This suggests that some species may have used flooded terrestrial habitat for spawning, feeding, or both. The findings from our study provide much needed insight into fish-floodplain function in a temperate, channelized river system and suggest that lateral connectivity of the main river channel to less degraded reaches of its floodplain should become a management priority not only to maintain faunal biodiversity but also potentially reduce the impacts of non-native species in large river systems.

Wetlands have global, regional, and local values in terms of hydrologic, biogeochemical, and ecological criteria. Especially in developing countries such as Turkey, a continued unsustainable development process, which degrades nature, has also been threatening wetlands. The main problem is the relationship between the stakeholders and local economic interests, which is often conflicting. International agreements such as the Ramsar Convention are key actions for solving these problems in terms of wise-use principles. In this study, Uluabat Integrated Wetland Management Plan, which was prepared under Ramsar principles, has been evaluated as a case study. Uluabat is one of the most important wetlands, not only because of its regional and local usage, but also its global merits such as serving as a wintering and feeding area for some endangered species. The investigated plan is important for Turkey as a pioneer study. It can be seen as a framework rather than a comprehensive plan. It needs not only some revision in its content but also some additional activities, such as monitoring and evaluation. Integrating it with a regional rural development project is needed in order to achieve proposed objectives.

Soil moisture is frequently manipulated by wetland managers to achieve a desired composition and production of plant species. Pink smartweed (Polygonum pensylvanicum) is a species valued by wetland managers because of its potential seed production and food base for migrating and wintering waterbirds. To improve ability to manage pink smartweed, we measured the influence of four growing-season soil moisture regimes (flooded, field capacity, prescribed moist-soil management, and continuously dry) in playa wetlands of the Southern High Plains of Texas. We used xylem water potential as an index of soil moisture available to the plants and compared vegetation and seed production among the four moisture treatments. Daily net photosynthesis was measured in each playa at 0900, 1200, and 1700 hours. The continuously-flooded wetland had the lowest absolute xylem water potential value (−0.294 MPa), followed by the playa at field capacity (−0.446 MPa), moist-soil managed playa (−0.758 MPa), and dry playa (−1.039 MPa). Vegetation biomass (F_3,40 = 97.7, P < 0.001) and seed production (F_3,40 = 54.3, P < 0.001) of pink smartweed differed among soil moisture treatments. Conducting moist-soil management (x̄ = 6816 kg/ha) increased vegetation biomass by 44% over the dry treatment (x̄ = 4706 kg/ha). As soil moisture increased to field capacity (x̄ = 9010 kg/ha) vegetation increased by 32% above the moist-soil treatment. Maintaining standing water in a playa maximized vegetation production (x̄ = 12497 kg/ha) of pink smartweed. Seed production was greatest when soil moisture was maintained at field capacity (x̄ = 695 kg/ha). There was no difference in seed production between the moist-soil managed (x̄ = 492 kg/ha) and flooded playas (x̄ = 514 kg/ha), which was 28% lower than the field capacity treatment. Seed production in the dry treatment (x̄ = 377 kg/ha) was 46% lower than the field capacity treatment and 25% below the flooded and moist-soil managed treatments. Net photosynthesis and xylem water potential decreased throughout the day in all treatments except continuously flooded, which corresponded to the increased vegetation production in this treatment. Slight increases in water stress relative to the continuously flooded treatment resulted in a redistribution of resources from vegetation to seed production. Managers should consider maintaining wetland soils at field capacity to increase seed production of pink smartweed.

This study investigates the fall season similarity of reflectance spectra among salt marsh species to identify and map marsh vegetation types at species level using hyperspectral remote sensing. The medians of the reflectance spectra collected from canopies of dominant marsh vegetation (Phragmites australis, Spartina patens, Spartina alterniflora, and Distichlis spicata) in the New Jersey Meadowlands were compared using a set of statistical metrics. Results show that these marsh species are distinct and separable spectrally in the near infrared (NIR) region of the spectrum. The two Spartina species are similar in spectra and are the most difficult pairs to separate. However, the distribution of red-edge parameter (maximum inflection) suggests that red-edge may be useful for discriminating these two species. The results of this study can be applied to classify marsh vegetation at species level using remote sensing and to map ecotypes along salinity or oxygen gradients as a way to assess coastal wetlands health and condition.

The estimation of aboveground biomass is important in the management of natural resources. Direct measurements by clipping, drying, and weighing of herbaceous vegetation are time-consuming and costly. Therefore, non-destructive methods for efficiently and accurately estimating biomass are of interest. We compared two non-destructive methods, visual obstruction and light penetration, for estimating aboveground biomass in marshes of the upper Texas, USA coast. Visual obstruction was estimated using the Robel pole method, which primarily measures the density and height of the canopy. Light penetration through the canopy was measured using a Decagon light wand, with readings taken above the vegetation and at the ground surface. Clip plots were also taken to provide direct estimates of total aboveground biomass. Regression relationships between estimated and clipped biomass were significant using both methods. However, the light penetration method was much more strongly correlated with clipped biomass under these conditions (R² value 0.65 compared to 0.35 for the visual obstruction approach). The primary difference between the two methods in this situation was the ability of the light-penetration method to account for variations in plant litter. These results indicate that light-penetration measurements may be better for estimating biomass in marshes when plant litter is an important component. We advise that, in all cases, investigators should calibrate their methods against clip plots to evaluate applicability to their situation.