The sprouting of vegetative propagules disseminated hydrochorously throughout the active zones of braided rivers is a potentially important method of riparian tree establishment for some species. The hydrogeomorphological characteristics of the immediate local environment (patch), upon which the propagules are deposited, can have a significant influence on survivorship and shoot growth. We conducted a field experiment along the River Tagliamento, Italy during 2003, which involved the planting of Salix elaeagnos and Populus nigra cuttings (vegetative fragments) within exposed sediment patches differing in their relative elevations and sedimentary characteristics. Both species are found in riparian systems throughout Europe and are employed in riparian restoration/conservation schemes. The experiment was designed to examine the influence of environmental factors on the survivorship and shoot growth of these species immediately following propagule deposition. The study plots were comprised of a mix of silt, sand, and gravel. Small amounts of clay and organic matter (maximum 1% and 1.3%, respectively, by weight) were present. Relation between survivorship and growth of the two species and environmental characteristics were explored using a combination of Principal Components and regression analyses. Probability of survival for both species was found to be greater in patches containing relatively greater amounts of clay and organic matter and low proportions of sand in relation to gravel. However, Salix elaeagnos had greater survival probability at lower elevations with relatively higher moisture levels, while the reverse was true for P. nigra. Both species were similar in their growth response to environmental variables, growth primarily being supported by relatively higher levels of clay, organic matter, and moisture, and lower elevations. Populus nigra survivorship was greater than that of S. elaeagnos, although shoot growth from S. elaeagnos exceeded that of P. nigra. The study highlights the influence of abiotic factors within a river's active zone on vegetative sprouting and indicates the interspecific variations that can be observed in riparian tree species with similar life-history traits. The findings have implications for river management, restoration, and conservation efforts.

Wind-tidal flats are the dominant coastal wetland type in southern Texas, USA. Succulent vascular plants are colonizing the flats in some locations, often where past dredge disposal along navigation channels and other activities have interrupted natural water communication between hypersaline bays and large areas of wind-tidal flats. The objective of this study was to test the feasibility of proposed removal of a causeway at Laguna Atascosa National Wildlife Refuge to restore the historic hydrologic regime and eradicate encroaching vascular plants, mostly Salicornia bigelovii, on the assumption that high sediment salt excluded these vascular plants under natural conditions. Assessment in spring 1998 of the density of Salicornia in relation to elevation and sediment salt of bare and vegetated zones on the vegetated flats on one side of the causeway and entirely barren flats with unimpaired connection to Laguna Madre on the other side of the causeway suggested that sediment salt >0.1 g ml⁻¹ excluded vascular plants. However, bimonthly sampling in 1999–2000 revealed that sediment salt concentrations were >0.1 g ml⁻¹ throughout the vegetated zone in July and more locally in the period of winter low water, with little impairment to established plants. This indicates that if control is desired, it must be exerted at germination and early establishment during and after fall high water. Continuous monitoring of water levels on either side of the causeway suggests that, even with removal of the causeway, flooding with hypersaline lagoon water will be too infrequent to counteract the freshening effect of a permanent hydraulic connection to the main agricultural drain of the lower Rio Grande Valley that has developed at the other end of the salt flat. Monitoring Salicornia distribution over six years documented huge variation between years but no trend toward increasing dominance of the flats. The results of this study illustrate that the most obvious alterations to a site may not be the most influential on function and that the scale of analysis may have to extend far beyond the site in space and time to evaluate a proposed restoration properly.

Establishing species-rich plant communities is a common goal of habitat restoration efforts, but not all species within a target assemblage have the same capacity for recruitment and survival in created habitats. We investigated the development of a tidal salt marsh plant community in the presence of a rapidly colonizing dominant species, Salicornia virginica, in a newly created habitat in Mugu Lagoon, California, USA. We planted rooted cuttings of S. virginica, Distichlis spicata, Jaumea carnosa, and Frankenia salina in single- and mixed-species stands, where each species was planted alone or in combination with S. virginica in 4 m² plots. We measured species percent cover, recruit density, canopy structure, and aboveground biomass after three growing seasons. When planted alone, S. virginica achieved the greatest cover, up to 70%, followed by J. carnosa (55%), F. salina (35%), and D. spicata (12%). Total percent cover was about 30% lower than in a reference site. For each species, average percent cover and aboveground biomass per plant were generally similar between single-species and mixed planting treatments, suggesting that on the time scale of this study, competition between species was weak. Canopy structure (height, number of layers) and total aboveground biomass of all species were largely unaffected by planting treatments, although S. virginica was shorter when planted with J. carnosa. Salicornia virginica recruits constituted approximately 98% of the cover of seedling recruits into the created site. Despite intense S. virginica recruitment, our intervention in the successional process by planting species with poorer colonization abilities, particularly J. carnosa and F. salina, prevented S. virginica from completely dominating the canopy, thus increasing vascular plant richness in the created site. Artificially increased richness may enhance some ecosystem functions and create a seed source to facilitate the persistence of a diverse plant assemblage in restored sites.

Water balance in a seasonal floodplain in the Okavango Delta, Botswana was determined for three years (1997–1999). There was no surface outflow, and infiltration to ground water was very large (4.7–9.7 m during 90–175 days of flooding, or on average 4.6–5.4 cm·d⁻¹), amounting to 90% of total annual loss of water from the floodplain. At the arrival of the flood, when floodplain ground water was 3–5 m below ground, infiltration was controlled by vertical percolation through the aeration zone and was taking place with rates as high as 1.11–1.74 m during 10 days, or on average 11.1–17.4 cm·d⁻¹. Lateral ground-water flow from the floodplain toward surrounding dryland became the dominant process after the first days of flooding, when the floodplain ground-water table rose to the surface. Lateral ground-water drainage accounted for at least 80% of total infiltration. Direct measurements of infiltration confirmed high rates obtained from the water balance and revealed that the majority of infiltration occurred within a 10-m belt along the shore of the inundated area, with point infiltration rates as high as 42 cm·d⁻¹. The infiltration values are high compared to other large recharge wetlands (e.g., the Everglades, the Hadejia-Nguru) and result from a combination of lack of a low permeability surface layer in the floodplain and strong drainage of floodplain ground water driven by evaporation from the surrounding drylands. High infiltration and lateral ground-water flows have major implications for the Okavango Delta ecology, as they provide water to riparian vegetation, affect floodplain nutrient balance, and are part of the process responsible for immobilization of dissolved minerals.

Alteration of natural hydrologic regimes of most rivers in the southwestern United States has led to degradation of riparian habitats. Most areas historically covered by Rio Grande cottonwood [Populus deltoides Marshall subsp. wislizenii (Wats.) Eckenw.] have been replaced by exotic saltcedar (Tamarix chinensis Lour.). Following an earlier study in the Middle Rio Grande Valley, New Mexico that evaluated faster staged water drawdowns to restore riparian habitat, we evaluated slower rates, 2 cm/day and 5 cm/day (starting depth  =  30 cm) to determine if cottonwood seedling density could be increased. During the period of spring flood recession of the Rio Grande, we placed seed-bearing branches of cottonwood in experimental basins and applied the drawdown treatments. Following the end of drawdowns, we conducted the first vegetation sampling to determine cottonwood and saltcedar seedling densities in the area. We also conducted a mid-season, an end-season, and an over-winter vegetation sampling to observe changes in seedling densities over time. Saltcedar and cottonwood seedling densities did not differ statistically between the drawdown treatments. However, survival of cottonwood seedlings during the first growing season in the 2 cm/day drawdown was greater than in the 5 cm/day drawdown. Greater seedling survival in the slower drawdown was likely due to increased soil moisture levels in that treatment, corresponding to a more gradual descending limb of the historical hydrograph. Use of a slow water drawdown (2 cm/day; about 20 days duration) synchronized with natural seed rain of cottonwoods will result in high first season densities of this important riparian species.

The main objectives of this study were to identify a small of edaphic factors that could be related to vegetation distribution in a coastal dune salt marsh system in the Southeast of Spain and to establish a simple conceptual model to describe the relationships between these soil factors and the main plant communities. Soil and vegetation data were obtained from 87 sampling plots. The plant communities studied were dominated by Crucianella maritima, Teucrium dunense, Ammophila arenaria, Lygeum spartum, Schoenus nigricans, Juncus maritimus, Limonium cossonianum, Sarcocornia fruticosa, Arthrocnemum macrostachyum, and co-dominance of Sarcocornia fruticosa and Arthrocnemum macrostachyum. The first four communities occupied summit positions and the rest of communities interdune depressions. In addition, we sampled plots in bare soil at interdune depressions. The soil parameters studied were soil salinity, soil moisture, the ground-water level, the depth to gleyed matrix, and the distance to the shoreline. Soils at interdune depressions were consistently more saline, wetter, and with a shallower water table and gleyed matrix than soils at summit positions. Soil moisture, salinity, and the distance to the shoreline were parameters related to plant distribution at summit positions. However, at interdune depressions species distribution was mainly related to salinity, moisture, the depth of the ground water, and the depth to gleyed matrix. In the conceptual model proposed, bare soils are characterized by their extreme salinity in the growing season (spring) and a shallower ground-water level, which leads to a shallower gleyed matrix.

The Floristic Quality Index (FQI) has been proposed as a tool that can be used to identify areas of high conservation value, monitor sites over time, assess the anthropogenic impacts affecting an area, and measure the ecological condition of an area. FQI is based on the Coefficient of Conservatism (C), which is a numerical score assigned to each plant species in a local flora, primarily from best professional judgment, that reflects the likelihood that a species is found in natural habitats. FQI is computed by multiplying the mean Coefficient of Conservatism (C) by the square root of species richness for an observational unit. Great Lakes coastal wetlands were used to assess the properties and performance of various species richness, Coefficient of Conservatism, and Floristic Quality indices, as well as compare C-value assignments from two U.S. states (Wisconsin and Michigan). FQI and species richness increased with sampling area according to a power function, but C more or less remained constant. Sampling schemes should therefore focus on controlling sampling area and minimally sampling each community type at a site. In some cases, Wisconsin and Michigan assigned different values of C to the same species, highlighting possible effects due to the somewhat subjective nature of C-value assignment. Coefficient of Conservatism and Floristic Quality indices were better at discriminating differences between sites, independent of a condition gradient, than species richness alone, but neither index type outperformed the other. Both types of indices were also found to be acceptable ecological indicators of condition, although Floristic Quality indices consistently outperformed Coefficient of Conservatism indices in this capacity. Regardless of the subjectivity involved with the assignment of C-values and that ‘floristic quality’ is a human concept and not a true ecosystem property, both Coefficient of Conservatism and Floristic Quality indices seem to be effective indicators of condition in Great Lakes coastal wetlands.

Amphibian populations have declined worldwide. To pursue conservation efforts adequately, land managers need more information concerning amphibian habitat requirements. To address this need, we examined relationships between anurans and habitat characteristics of wetlands in the Lower Mississippi River Alluvial Valley (LMAV). We surveyed chorusing anurans in 31 wetlands in 2000 and 28 wetlands in 2001, and measured microhabitat variables along the shoreline within the week following each survey. We recorded 12 species of anurans during our study. Species richness was significantly lower in 2000 than 2001 (t-test, P < 0.001) and correlated with an ongoing drought. We found species richness to be significantly greater at lake sites compared to impoundment, swale, and riverine sites (ANOVA, P  =  0.002). We used stepwise regression to investigate the wetland types and microhabitat characteristics associated with species richness of chorusing anurans. Microhabitat characteristics associated with species richness included dense herbaceous vegetation and accumulated litter along the shoreline. Individual species showed species-specific habitat associations. The bronze frog, American bullfrog, and northern cricket frog were positively associated with lake sites (Fisher's Exact Test, P < 0.05), however wetland type did not significantly influence any additional species. Using bivariate correlations, we found that six of the seven most common species had significant associations with microhabitat variables. Overall, our findings support the view that conservation and enhancement of amphibian communities in the LMAV and elsewhere requires a matrix of diverse wetland types and habitat conditions.

Turloughs are seasonal ground-water-dependent wetlands that occur in the karst landscape of western Ireland. Various typologies based on between-site variation have been applied to turloughs. However valid in understanding turlough functioning, these typologies are difficult to relate to one another, tend to overlook within-site variation, and do not address management issues affecting these priority habitats of the European Union. Furthermore, typologies have not fully utilized available data and lack the comprehensive perspective needed to capture processes driving turlough ecology. We used unpublished and published data on a per-turlough basis to explore the main variables affecting turlough ecology in Ireland. Multivariate analysis shows that turloughs do not split into distinct types; rather, there is one continuum from dry to wet sites, which affects all aspects of turlough ecology. This dry-wet continuum arises from various degrees of karstification of the underlying and surrounding bedrock, which in turn leads to different water inputs, water chemistries, and different deposits on the turlough floor. Few turloughs can be considered as truly dry or wet; most are intermediate or dry-wet mosaics. Turloughs or parts of turloughs at extremes of the dry-wet continuum need different protection measures to prevent water pollution, manage summer grazing, or maintain the hydrologic regime. Although turlough typologies seem logical and straightforward in theory, in practice, typing turloughs is difficult. Trying to fit turloughs within typologies that are weakly supported by the data on which they are based can lead to problems if inappropriately used. A dry-wet continuum concept not only better fits these same data but also gives scope for a more flexible approach to turlough conservation.

This study examined landscape change in the Peace-Athabasca Delta, northern Alberta, Canada. The proportion of the landscape covered by ten habitat types was determined for five vintages of air photos (1945–2001) from 24 randomly chosen study areas. To test for reproducibility, three vintages were analyzed by two independent teams, neither of which knew the dates or locations of air photos. Their results were highly correlated. Comparison with another air photo study focused in the southeastern delta revealed good agreement. Analysis of oblique air photos extended the reconstruction back to 1927. Of four cover types (water, marshes, willows, forests), only water differed significantly in area between vintages. Cover trends for the most general of types (wet communities and dry communities) indicated drying from 1927 to 2001. This trend may be due to multidecadal geomorphic evolution and climate change. Currently, the changes are statistically non-significant, but nevertheless may inform about the long-term future of the ecosystem. Large spatial and temporal variation in landscape cover is characteristic of the system. The types and ranges of change in the delta's vegetation post-Bennett Dam (1968) do not appear unusual relative to pre-Bennett Dam change. A multi-decadal perspective is necessary to encompass normal oscillations in abundance. Key to understanding change in the delta is to think at multiple scales and to remain aware that trends or patterns are scale-dependent. The delta may not be predictable on the meso-scales relevant to society and management.

Two 1-ha riverine wetlands at the Olentangy Wetland Research Park in Columbus, Ohio, USA were constructed in 1993 with a nearly identical geomorphology and have maintained an identical hydrology since their creation. The only initial difference was that one wetland was planted with native macrophytes in 1994 while the other was not. Sediment and nutrient accumulation was evaluated in May 2004, ten years after the wetlands were created. Higher mean sediment accumulation was detected in the deeper open water (OW) zones of both wetlands (6.1 ±0.6 and 7.3 ±0.5 kg m⁻² yr⁻¹) than in the emergent (EM) vegetation zones (3.7 ±0.2 and 3.9 ±0.3 kg m⁻² yr⁻¹). Directional spatial structure associated with sediment accumulation was detected in both wetlands and was attributed to the greater accumulation in the OW zones and the gradual decrease in accumulation from inflow to outflow. Despite several years of markedly higher productivity in Wetland 2, this wetland showed no evidence of greater organic C accumulation; however, the dense Typha established during those years may have elicited greater deposition and reduced re-suspension of sediment in the OW zones. Large accumulations of Ca (235 ±23 and 235 ±15 kg m⁻² yr⁻¹) and inorganic C (71.6 ±6.9 and 70.3 ±4.8 g m⁻² yr⁻¹) in the OW zones of both wetlands suggest that CaCO₃ deposition has remained a critical process where alga productivity has been highest. Annual rates of sediment and nutrient accumulation for each wetland were lower than those calculated in previous years and typically fall between ranges seen for newly created wetlands and natural wetlands.

Diatom-based bioassessment in wetlands requires quantitative characterization of spatial and temporal variability of the diatom assemblages within each wetland. The purpose of this study was to examine surface-sediment diatom distributional patterns in a wetland to determine how best to sample these systems to capture spatial variability in the assemblage. Diatoms and environmental conditions were characterized from 29 sampling points within a wetland in the floodplain of the Columbia River, Oregon, USA. A total of 159 diatom taxa were identified in the surface-sediment samples. Species richness was high at each sampling point (median: 42, range: 23–57), and relative abundances of common taxa varied between 15 and 39% throughout the wetland. Assemblages contained taxa with both benthic (e.g., Staurosira construens, Nitzschia palea, Fragilaria capucina, Achnanthidium minutissimum) and planktonic (e.g., Aulacoseira granulata and Tabellaria spp.) preferences. Non-metric multidimensional scaling (NMDS) techniques detected differences in the low marsh and upper marsh sediment diatom assemblages. Geostatistical analysis showed spatial autocorrelation of the diatom assemblage in the wetland, measured as semivariance and Moran's I. A simulation procedure indicated that changes in diatom species richness stabilized after approximately five samples were composited. Our results suggest that the wetland surface sediment diatom assemblage is heterogeneous and that hydrologic gradients may be an important structuring force. Diatom-based bioassessment has the potential to be a useful tool in assessing wetland environmental conditions; however, the shallow nature and complex hydrology of these systems require careful sampling design to adequately characterize the diatom assemblage.

Salinity is increasing in wetland ecosystems, but the consequences for ecological communities are poorly understood. Iris hexagona is the only North American iris that survives in brackish marsh. Environmental salinity affects the physiology, growth, and reproduction of this glycophytic perennial, as well as plant-herbivore interactions. In brackish wetlands, 80% of iris flowers are consumed by white-tailed deer (Odocoileus virginianus), which rarely browse flowers in freshwater habitats. We investigated the effects of florivory and salinity on I. hexagona sexual and clonal reproduction. Irises that were protected from deer produced 20 times more mature seed capsules than unprotected plants. Experimental floral browsing increased both belowground clonal growth by 30% (P  =  0.0003) and flower production the following year by 16% (P  =  0.112). Iris populations differed significantly in clonal reproduction (P  =  0.004), and interactions between salinity and population affected clonal (P  =  0.005) and sexual (P  =  0.054) output, suggesting that populations may be differentially adapted to environmental salinity. Brackish conditions can promote floral browsing and loss of sexual reproduction, but plants such as I. hexagona can compensate by allocating more resources to belowground clonal growth.

This study investigated how changes in salt marsh soil properties and topography on sediment fans related to shifts in salt marsh plant community composition in the Elkhorn Slough Watershed, California, USA. Several sediment fans have formed in this watershed as soil eroding from farms moved downslope, filling marshes, mudflats, and channels. Sandy sediment deposition increased marsh plain elevation and altered edaphic properties by increasing bulk density and decreasing soil moisture, salinity, and soil nitrogen compared to reference sites. These changes created a strong wetland-upland gradient and influenced the development of well-defined vegetation zones from wetland to upland: pickleweed (Salicornia virginica), cattail (Typha spp.) and bulrush (Scirpus spp.), and arroyo willow (Salix lasiolepis). Based on statistical analysis, arroyo willow grew in a distinct edaphic environment, and its expansion into the salt marsh was restricted by elevation in tidal areas greater than 1.80 m NAVD 88, spring soil moisture levels lower than 20%, and year-round salinity levels lower than 2.67 dS/m. Cattail and bulrush were present in transitional environmental conditions with fluctuating salinity and at an elevation similar to that of the pickleweed community. The hydrogeologic setting played a part in this change, as the contribution of upland sandy soils likely facilitated the emergence of new edaphic properties including lower salinity, lower soil moisture, and reduced soil nutrients. The findings in this study underline the importance of on-going erosion-control efforts to estuarine conservation in Central California.

Twelve tree species common in Everglades tree islands were subjected to three hydrologic regimes under controlled conditions for 25 weeks and assessed for growth and physiological responses. Treatments representing high, low, and no flood were maintained in pools of water to mimic seasonal variation in water depths at different positions in tree islands. Soil inundation under the high flood treatment resulted in reduced tree growth (height, basal diameter, crown volume) that was more pronounced and occurred earlier in mesic forest species than in swamp forest species. Physiological responses differed less among species, although stomatal conductance was a better predictor of the effects of flood stress on growth than either relative water content or chlorophyll fluorescence (F_v/F_m). Some swamp species appeared to be better adapted to rising water levels than others; Annona glabra, Morella cerifera, and Salix caroliniana responded more positively to flooding, while Magnolia virginiana, Persea borbonia, Chrysobalanus icaco, and Ilex cassine were less flood-tolerant. The highest mortalities and lowest growth were observed in the five upland species: Bursera simaruba, Coccoloba diversifolia, Eugenia axillaris, Sideroxylon foetidissimum, and Simarouba glauca. Of these, Sideroxylon and Simarouba did not survive to the end of the study under the high flood treatment. The moist soil conditions simulated by the low flood treatment resulted in greater growth in all species compared to soil inundation under high flood, except for the most flood-tolerant (Annona, Morella, Salix). The arrangement of species according to their responses to experimental flooding roughly paralleled their spatial distribution in the tree islands. The gradient in species responses demonstrated in this experiment may help guide responsible water management and tree island restoration in the Everglades.

The coastal salt marshes of the Aransas National Wildlife Refuge (ANWR), Texas, USA support a wintering population of the endangered Whooping Crane (Grus americana). Although the bulk of their winter diet is comprised of blue crabs, berries from the Carolina wolfberry (Lycium carolinianum) can contribute 21–52% of crane energy intake early in the wintering period. Monthly, from November 2003 to February 2005, we tracked L. carolinianum growth in nine 1-m² permanent macrophyte plots along the estuarine gradient to understand the spatial and temporal variability of this perennial halophyte. Lycium carolinianum showed strong seasonal growth patterns, with leaf production peaks in late winter and again in late summer, just prior to flowering, but little significant spatial variation. Flowering of L. carolinianum occurred in October and November, and peak berry abundance coincided with the arrival of the cranes in late October and early November. During this period, the total number of flowers per plant and total number of leaves per plant across all sites were positively related to surface-water depth and pore-water salinity. The numbers of flowers and berries per plant were significantly higher at our lowest elevation site during the 2004 fruiting season. Berries were rarely observed in the marshes for the remainder of each calendar year. Stem diameter was the best estimator of L. carolinianum aboveground biomass in ANWR marshes, accounting for approximately 94% of the variability (p < 0.001). Monthly changes in estimated aboveground biomass at each site revealed no distinguishable spatio-temporal trends. This is likely a result of L. carolinianum's woody stem, which accounts for much of the total plant biomass but is much less dynamic than photosynthetic and reproductive tissues.

We describe effects of salinity and temperature on germination characteristics of three dominant macrophytes, Phragmites australis, Juncus acutus, and J. kraussii, located in wetlands along the Hunter River, New South Wales, Australia. These wetlands were altered, from estuarine to freshwater habitats, by flood mitigation activities initiated during the 1970s. Tidal restoration to approximately 300 hectares of the marsh is planned to occur by 2008, with the goal to reduce freshwater vegetation in favor of salt marsh species. We determined if timing restoration projects to coincide with natural germination cycles or seasonal conditions of high salinity would be disadvantageous to P. australis or J. acutus germination. Germination trials lasted 25 days under two temperature range treatments (l0–25 and 15–30°C) and a salinity gradient (0–30 ppt). Many P. australis seeds commenced decomposition after three days (up to 58%). Increased salinity lowered germination in all species; however, only P. australis was influenced by temperature. Phragmites australis germinated in all conditions, although germination rate was low (2% ± 1.7) in the highest salinity treatment at high temperature regime. Both Juncus species obtained 100% germination in freshwater, failed to germinate in the highest salinity, and seed viability was not affected by 25 days emersion in high salinity. For areas dominated by P. australis in eastern Australia, we suggest that tidal reinstatement should be initiated in late autumn when P. australis seed banks are low. Additionally, periods of heavy rainfall, which reduce soil salinity, may help other species colonize the area. Further studies are required to determine characteristics of J. acutus that can be used to repress the species spread along the eastern coast of Australia. Currently, active measures involving chemical and physical weed suppression, litter removal, and mass planting of native species, are likely to be required to achieve management goals.

The effects of hydrologic conditions, water quality gradients, and vegetation on nitrous oxide gaseous emissions were investigated in two identical 1-ha surface-flow created riverine wetlands in Columbus, Ohio, USA. For two years, both wetlands experienced seasonal (winter-spring) controlled hydrologic flood pulses followed by one year in which they received a steady flow rate of water. Nitrous oxide fluxes were quantified in a transverse gradient at different elevations (edge plots and high marsh plots with alternate wet and dry conditions, and low marsh plots and open water plots that were permanently flooded). The highest average of N₂O fluxes was observed in high marsh plots (21.8 ± 2.5 µg-N m⁻² h⁻¹), followed by edge plots (12.6 ± 2.5 µg-N m⁻² h⁻¹), open water plots (9.9 ± 2.1 µg-N m⁻² h⁻¹), and low marsh plots (7.0 ± 4.8 µg-N m⁻² h⁻¹). Highest nitrous oxide fluxes were consistently observed in high marsh plots during summer when soil temperatures were ≥ 20°C. In permanently flooded plots without vegetation, nitrous oxide fluxes were low, regardless of flood-pulse conditions. In high marsh plots, water table remained near the soil surface one week after flooding, causing an increase in N₂O fluxes (25.9 ± 13.9 µg-N m⁻² h⁻¹) compared with fluxes before (2.4 ± 6.4 2.2 µg-N m⁻² h⁻¹) and during (6.9 ± 2.2 µg-N m⁻² h⁻¹) flooding. In edge plots, nitrous oxide emissions increased during and after the flooding (11.3 ± 3.2 and 7.3 ± 3.3 µg-N m⁻² h⁻¹) compared with fluxes before the flood pulse (4.1 ± 1.8 µg-N m⁻² h⁻¹). In low marsh and edge zones, no significant (P>0.05) differences were observed in the seasonal N₂O fluxes in the pulsing year versus steady-flow year. Spring N₂O fluxes from high marsh plots were significantly (P = 0.04) higher under steady-flow conditions (26.2 ± 5.5 µg-N m⁻² h⁻¹) than under pulsing conditions (9.6 ± 3.6 µg-N m⁻² h⁻¹), probably due to the water table near the surface that prevailed in those plots under steady flow condition. N₂O fluxes were higher in plots with vegetation (39.6 ± 13.7 µg-N m⁻² h⁻¹) than in plots without vegetation (−3.6 ± 13.7 µg-N m⁻² h⁻¹) when plots were inundated; however, when no surface water was present, N₂O fluxes were similar in plots with and without vegetation. Implications for large-scale wetland creation and restoration in the Mississippi River Basin and elsewhere for controlling nitrogen are discussed.

Local abundance of animals with aquatic and terrestrial life stages may be useful to determine criteria for protective buffers around wetlands. Maiden flights and daily commutes of adult Odonata (damselflies, dragonflies) occur between wetland breeding area and adjacent upland habitat used for foraging, maturation, and nocturnal roosting. We measured abundance of dragonflies adjacent to a wetland in Mississippi, USA to determine if abundance varied with distance from water. Sexually mature males and combined females/prereproductive adult males (females-immatures) were recorded 10–160 m from the littoral edge of a 185 ha shallow reservoir. The number of dragonflies was dominated by Celithemis eponina throughout the study period. Mean abundance did not change with distance from water out to 160 m, both for all species combined and for each of three dominant species. In the assemblage, mature males outnumbered females-immatures in the 10–40 m distance, whereas the reverse occurred in the 130–160 m distance. At the species-level, there was a mixed response in the mature male: female-immature ratio, with little resemblance to the assemblage pattern. Results of this study suggest that wide buffer zones around wetlands may be essential to protect Odonata assemblages, especially females and sexually immature adults. Furthermore, odonate flight behavior may serve as a useful bio-criterion to determine the width of ecologically significant wetland buffers.