Floodplain forests are critically linked to society's welfare and will rise immensely in value as water related issues become increasingly important. Although progress has been made in promoting the importance of floodplain wetlands to the public and in successfully manipulating wetland systems toward particular goals, we are still quick to generalize and may neglect some of the complexities of these systems during our research, management, and restoration efforts. Within the Southeast, floodplain inundation varies from near constant to none, and forest net primary productivity (NPP) ranges from near the highest of the temperate zone to among the lowest. The complex entanglements of hydroperiod and all other floodplain forest processes and traits are daunting. Our greatest challenge may be to understand and base actions on societal influences and landscape evolution within watersheds and floodplains. It will become increasingly less relevant to study, manage, or try to restore portions of floodplains without due consideration of past, current, and future socioeconomic drivers and land use trends within basins and watersheds. The human footprint on these critical systems has been very distinct for the last 200–300 years; now, it is becoming enormous and must be fully taken into account if we are to be successful in maintaining significant amounts of floodplain forests in the Southeast.

Human alterations along stream channels and within catchments have affected fluvial geomorphic processes worldwide. Typically these alterations reduce the ecosystem services that functioning floodplains provide; in this paper we are concerned with the sediment and associated material trapping service. Similarly, these alterations may negatively impact the natural ecology of floodplains through reductions in suitable habitats, biodiversity, and nutrient cycling. Dams, stream channelization, and levee/canal construction are common human alterations along Coastal Plain fluvial systems. We use three case studies to illustrate these alterations and their impacts on floodplain geomorphic and ecological processes. They include: 1) dams along the lower Roanoke River, North Carolina, 2) stream channelization in west Tennessee, and 3) multiple impacts including canal and artificial levee construction in the central Atchafalaya Basin, Louisiana. Human alterations typically shift affected streams away from natural dynamic equilibrium where net sediment deposition is, approximately, in balance with net erosion. Identification and understanding of critical fluvial parameters (e.g., stream gradient, grain-size, and hydrography) and spatial and temporal sediment deposition/erosion process trajectories should facilitate management efforts to retain and/or regain important ecosystem services.

Alternating braided and meandering stream flow regimes throughout the Quaternary Period have left a subtly complex landscape of depositional features within the Mississippi Alluvial Valley (MAV). Prior to European settlement, those variations produced tremendous spatial complexity and diversity within vast forested wetlands and extensive fire-maintained prairies and savannas, with the distribution of specific plant communities largely reflecting abiotic site characteristics such as geomorphology, soils, and hydrology. Agricultural development, river engineering, flood protection, and drainage projects over the past century have destroyed most of the natural vegetation and obscured the patterns of plant community distribution. Recent studies have established hydrogeomorphic criteria for wetland classification over a large part of the MAV. Detailed, spatially explicit geomorphology and soils data are available for the entire MAV, and hydrologic mapping has been completed in many areas. Thus, even in areas that are currently in agriculture, the tools exist to adapt the hydrogeomorphic classification and to develop maps of potential plant community distribution based on abiotic characteristics of sites. These Potential Natural Vegetation maps provide an indication of the multi-scale complexity that once characterized the MAV, and serve as planning tools for ecosystem restoration.

Data on vegetation composition and structure, soil and leaf nutrient pools, soil redox potential, and surface water hydrologic connectivity were collected from floodplains along six river reaches in western Tennessee to examine the effects of channel modifications on associated riparian systems. Comparisons among channelization treatments (non-channelized reaches, channelized and leveed reaches, channelized but non-leveed reaches) and floodplain geomorphology (depression and nondepressional sites) showed that hydrologic connectivity was affected by channelization treatments, particularly leveeing. The disconnected floodplains were drier, maintained higher nutrient pools, and had greater herbaceous biomass than floodplains still connected to channel hydrology. Runoff onto floodplains from the agriculturally dominated landscape of channelized and leveed tributaries, and flooding stress in the form of scour on floodplains along streams without levees may explain the observed pattern. Channel and floodplain hydrologic processes were most strongly connected for unchannelized streams. Unchannelized streams were varied in soil redox potential, water table, and nutrient pools. Vegetation composition reflects both historical hydrologic regimes and disturbances, and thus complex relationships to channel modifications. Results suggest both the subsidy (i.e., nutrient inputs) and the stress of flood events have been altered by anthropogenic activities, but these alterations were greatest in channelized systems compared to unchannelized systems.

Lateral channel migration initiates complex and dynamic biogeomorphic responses that are fundamental to the creation and maintenance of riparian habitats along low-gradient, coastal plain rivers. This study examines the effects of lateral migration rates on the structure and composition of riparian forests along the Congaree River, Congaree National Park, in the Atlantic Coastal Plain, South Carolina. Lateral channel migration rates were measured in a GIS using aerial photos from 1938–2006. Forest variables were measured from a stratified-random sample of 25 paired edge-interior plots, and analyzed using Mann-Whitney tests, Spearman's correlations, multi-response permutation procedures (MRPP), and non-metric multi-dimensional scaling (NMS) ordinations. Lateral channel migration produced a significant directional control on riparian forests. Pointbar forests exhibited classic forward succession dependent on spatial and temporal controls related to elevation, flood frequency, and lateral migration rates. Cutbank forests responded positively to exposure along the edge and increased in structural complexity with increasing proximity to the river; density, basal area, and richness varied inversely with lateral migration rates. Cutbank edges with low lateral migration allowed longer time for trees to colonize and they contained greater density, basal area, and richness. Cutbanks with high lateral migration contained lower tree density, basal area, and richness.

Alterations to the lower Mississippi River-floodplain ecosystem to facilitate commercial navigation and to reduce flooding of agricultural lands and communities in the historic floodplain have changed the hydrologic regime. As a result, the flood pulse usually has a lower water level, is of shorter duration, has colder water temperatures, and a smaller area of floodplain is inundated. Using average hydrologic conditions and water temperatures, we used established nitrogen and phosphorus processes in soils, an aquatic ecosystem model, and fish bioenergetic models to provide approximations of nitrogen and phosphorus flux in Mississippi River flood waters for the present conditions of a 2-month (mid-March to mid-May) flood pulse and for a 3-month (mid-March to mid-June), historic flood pulse. We estimated that the soils and aquatic biota can remove or sequester 542 and 976 kg nitrogen ha⁻¹ during the present and historic hydrologic conditions, respectively. Phosphorus, on the other hand, will be added to the water largely as a result of anaerobic soil conditions but moderated by biological uptake by aquatic biota during both present and historic hydrologic conditions. The floodplain and associated water bodies may provide an important management opportunity for reducing downstream transport of nitrogen in Mississippi River waters.

Eleven floodplain lakes in the lower White River, Arkansas were sampled using a boat electrofisher and gill nets during periods of river connection (April–May 2004) and disconnection (June–July 2004 and 2005). Environmental characteristics, including water quality and lake morphometrics were concurrently measured in each lake. Average measures of connectivity were calculated for the preceding 5-year period. Of the 11 lakes sampled, 7 lakes contained paddlefish. A total of 44 paddlefish were observed during the study, but only 1 was observed during the period of river connection. Eye-fork lengths ranged from 348–1040 mm (n  =  38). Paddlefish ranged in age from 3–19 years (n  =  27). Paddlefish were more likely to be found in long narrow floodplain lakes that connected to the river early in the year. Paddlefish catch per unit effort increased as lake surface area, dissolved oxygen level, and variability in the start date of connection increased. Our research indicated that both juvenile and adult paddlefish use White River floodplain lakes, despite the risk of being isolated in lakes for long periods or being prevented from accessing riverine spawning habitat.

We present long-term growth trends for 13 freshwater mussel species from two unregulated rivers and one regulated river in the southeastern U.S. Coastal Plain. We also collected baldcypress (Taxodium distichum (L.) Rich.) tree cores adjacent to mussel collection sites in one river and directly compared tree and mussel chronologies in this river. To extend our analysis spatially, we examined published baldcypress chronologies from six other unregulated rivers throughout the region. Biochronologies were developed using standard dendrochronology techniques and we explored relationships between annual growth and a suite of streamflow variables in each river. Growth of mussels in unregulated rivers was negatively correlated with annual flood pulse count and May and June discharge, but positively correlated with annual low pulse count and annual number of hydrographic reversals. Baldcypress growth in unregulated rivers was positively correlated with May and June discharge and negatively correlated with annual low pulse count. Mussel growth in the regulated river was not correlated with any streamflow variable suggesting that biological rhythms are decoupled from hydrologic variations in this system. This study shows how interannual variability in streamflow can benefit diverse taxa in floodplain rivers over long periods and how river regulation can disrupt these relationships.

This report documents changes in forest structure and growth potential of dominant trees in salt-impacted tidal and non-tidal baldcypress wetlands of the southeastern United States. We inventoried basal area and tree height, and monitored incremental growth (in basal area) of codominant baldcypress (Taxodium distichum) trees monthly, for over four years, to examine the inter-relationships among growth, site fertility, and soil physico-chemical characteristics. We found that salinity, soil total nitrogen (TN), flood duration, and flood frequency affected forest structure and growth the greatest. While mean annual site salinity ranged from 0.1 to 3.4 ppt, sites with salinity concentrations of 1.3 ppt or greater supported a basal area of less than 40 m²/ha. Where salinity was < 0.7 ppt, basal area was as high as 87 m²/ha. Stand height was also negatively affected by higher salinity. However, salinity related only to soil TN concentrations or to the relative balance between soil TN and total phosphorus (TP), which reached a maximum concentration between 1.2 and 2.0 ppt salinity. As estuarine influence shifts inland with sea-level rise, forest growth may become more strongly linked to salinity, not only due to salt effects but also as a consequence of site nitrogen imbalance.

Floodplain forests in the southeastern USA have recently been the focus of intensive restoration efforts after centuries of human-caused decline. Many of these restored forests appear to suffer from systemic problems arising from the altered disturbance regime in modern southeastern floodplains. Increasing evidence suggests that fire may be an occasional but important ecosystem component missing from these forests. Most relevant literature mentions fire only in passing, if at all; the literature that does discuss fire is typically either speculative or draws heavily from other ecosystems. This article develops the hypothesis that fire has been an important and recurrent disturbance in southeastern alluvial floodplains for millennia. It first synthesizes research indicating that the expansive monodominant bamboo stands (called canebrakes) once common throughout these floodplain forests were likely fire-obligate and might therefore be used as indicators of recurrent fires. It then examines pre-historic, historic, and recent evidence of fire in bottomland forests from both natural and human sources. Finally, it places these findings into ecological context, proposes an integrated study by which future research might clarify the ecological role of fire in southeastern floodplain forests, and addresses some implications for management.

Economic and cultural values, the same forces that led people to alter floodplain ecosystems, will be the forces that determine the extent of their restoration. Landowner investment in agricultural production and forest and hydrologic restoration will reflect perceived economic returns from investments, as well as personal preferences for the environmental services each land use provides. Conservation programs and emerging environmental markets can encourage floodplain restoration, but will be effective only if they improve economic returns from bottomland management relative to other land uses. Over the past three years, prices for corn, soybeans, wheat, and other agricultural commodities have increased sharply, increasing returns to crop production and decreasing the amount of marginally profitable cropland, land most likely to be restored to bottomland hardwoods. Understanding commodity price dynamics is critical for understanding the potential for retiring cropland into bottomlands. Often Farm Bill conservation title provisions attract the greatest attention regarding bottomland hardwood restoration. However, the commodity title, which sets commodity price supports, and energy policy, need to be considered because commodity and energy policy effect returns from bottomland hardwood restoration.

The emerging carbon market is an increasingly important source of finance for bottomland hardwood afforestation in the Lower Mississippi River Valley (LMV). Notwithstanding, there is a scarcity of empirical estimates of carbon sequestration specific to the region and we sought to address this outstanding need. We evaluated tree measurements from known-age bottomland hardwood stands from a chronosequence of sites in the LMV, drawing on 540 plot measurements within 67 stands. We derived a model of live tree biomass carbon as a function of stand age. The model explained 83% of the variation in live tree biomass carbon at the stand level, and provides a more accurate projection for application in the LMV than broader regional models currently available. Modeled live tree biomass carbon was greater than the corresponding regional estimate used in the U.S. Department of Energy's voluntary greenhouse gas reporting program for years 20 through 90 (up to 59% greater at year 50), but trended toward convergence at mature stages.

The back channels of islands on the Ohio River are assumed to provide habitat critical for several wildlife species. However, quantitative information on the wildlife value of back channels is needed by natural resource managers for the conservation of these forested islands and embayments in the face of increasing shoreline development and recreational boating. We compared the relative abundance of waterbirds, turtles, anurans, and riparian furbearing mammals during 2001 and 2002 in back and main channels of the Ohio River in West Virginia. Wood ducks (Aix sponsa), snapping turtles (Chelydra serpentina), beavers (Castor canadensis), and muskrats (Ondatra zibethicus) were more abundant in back than main channels. Spring peepers (Pseudacris crucifer) and American toads (Bufo americanus) occurred more frequently on back than main channels. These results provide quantitative evidence that back channels are important for several wildlife species. The narrowness of the back channels, the protection they provide from the main current of the river, and their ability to support vegetated shorelines and woody debris, are characteristics that appear to benefit these species. As a conservation measure for important riparian wildlife habitat, we suggest limiting building of piers and development of the shoreline in back channel areas.

Floodplain habitat provides important migration and breeding habitat for birds in the midwestern United States. However, few studies have examined how the avian assemblage changes with different stages of floodplain forest succession in the midwestern United States. In spring and summer from 2002 to 2004, we conducted 839 point counts in wet prairie/forbs fields, 547 point counts in early successional forests, and 434 point counts in mature forests to describe the migrating and breeding bird assemblage in the lower Missouri River floodplain. We recorded 131, 121, and 141 species in the three respective habitats, a number higher than most locations in the midwestern United States and comprising > 15% of all avian species in North America. Avian species diversity generally increased from west to east along the river, differed among land cover classes, but overlapped between seasons (migration and breeding) and years. Wet prairies were particularly important for conservation as there were 20 species of high conservation concern observed, including Dickcissels (Spiza americana). Important species for monitoring biotic integrity included the Northern Harrier (Circus cyaneus) and Bobolink (Dolichonyx oryzivorus) in wet prairie, Bell's Vireo (Vireo bellii) in early successional forest, and Northern Parula (Parula americana) and Prothonotary Warbler (Protonotaria citrea) in mature forest.

Channelization of rivers and streams threatens bottomland forest bird communities because it can lead to the formation of lateral gullies that connect streams to adjacent wetlands and unnaturally accelerate the draining of wetlands, potentially exposing some birds to high rates of nest predation. I studied how the hydrologic restoration of off-channel wetlands (plugging gullies that drain off-channel wetlands) affects the diversity, abundance, and nesting success of birds breeding within forested wetlands within the Cache River watershed in Illinois. I compared surface area, water depth, bird diversity, bird densities, and nesting success between treatment (gully plugs added) and control (gully plugs not added) wetlands pre- and post-treatment. During the breeding season of birds, treatment wetlands retained more flooded area and greater depths of water compared to control wetlands. Bird diversity was unaffected by the installation of gully plugs. The density and nesting success of prothonotary warblers (Protonotaria citrea) was higher in treatment wetlands than in control wetlands. Documenting changes in the bird community in response to this conservation action provides a means to measure the success of restoration activities in the Cache River watershed and inform conservation plans and restoration efforts in other bottomland forest ecosystems.

Ecosystem approaches to management require monitoring of processes and species indicative of the integrity of the system in order to understand the effects of management and other perturbations. We examined the effects of three timber harvest options (single-tree selection, patch cuts, no harvest) on the reproductive biology of a possible indicator of bottomland forest ecosystem integrity, the prothonotary warbler (Protonotaria citrea). Timber harvests reduced the number of available nest cavities, reduced the density of breeding males on the plots, and increased the sizes of male territories. However, timber harvest had no obvious effect on nest predation or brood parasitism frequencies. Brood parasitism was instead related to distance from a nearby levee, a main source of brown-headed cowbirds (Molothrus ater) in the area. Productivity remained similar within suitable habitat regardless of treatment. Reproductive success was strongly influenced by annual variation, which we attribute to the timing and extent of annual flooding, a fundamental ecosystem process in floodplain forests. Continued anthropogenic alterations in flooding patterns may have a greater influence than current timber management on the future population levels of prothonotary warblers in the Mississippi Alluvial Valley. This species, with others, could play a valuable role in an ecosystem-oriented monitoring program.

The Swainson's warbler (Limnothlypis swainsonii Audubon) is a species of concern within forested wetlands across the southeastern U.S. Previous studies involving low-elevation sites may not have adequately represented the habitat affinities of this species. We examined relationships between Swainson's warbler occupancy and vegetation structure at relatively high-elevation bottomlands at White River National Wildlife Refuge (WRNWR). In 2004 and 2005, we systematically surveyed 1453 sites and collected vegetation data at 70 occupied sites (< 5% occupancy) and 106 randomly selected unoccupied sites. Occupied sites had greater canopy cover, density of cane (Arundinaria gigantea Walt. Chapm.) and shrub stems, litter depth, and greater and more uniform understory vegetation density than unoccupied sites. Moreover, cane and understory vegetation density were associated with more persistent habitat use. Ultimately, cane stem density was the best predictor of Swainson's warbler occupancy with an AIC_c weight of 99% over all models considered. Overall, our results suggest that cane, dense understory structure, and a well-developed leaf-litter layer are key habitat components for Swainson's warblers at WRNWR. These findings are especially relevant given the substantial decline of canebrakes throughout the Southeast. Swainson's warbler management should include enhancement of canebrakes via manipulations that mimic natural disturbances.

In the White River National Wildlife Refuge, we located and monitored 39 Mississippi Kite (Ictinia mississippiensis) nests during the 2004 and 2005 breeding seasons to examine reproductive success and causes of nesting failures. Nest failures were documented using five video recording systems. All kite nests not monitored with a video recording system were observed every 3 or 4 d. The apparent reproductive success during this study was 28.2% (n  =  39 nests). Using the Mayfield estimator, we determined the nest success to be 36.3% over 1226 nest-exposure days with a daily nest survival of 0.9837. We recorded seven nest failures and eight probable predation attempts. Predation was the most common cause of nest failures of video observed nests (57%), with western rat snakes (Elaphe obsoleta) being the most common predator of kite eggs and nestlings. Other observed nest failures included nest abandonment, a chick falling out of a nest, and an infertile egg. Reproductive success reported in this study was the second lowest (28%) of all Mississippi Kite studies. This low reproductive success rate is likely not adequate to support a viable population in the White River National Wildlife Refuge, indicating this may currently be a sink population.

Floodplain ecosystems in the southeastern United States provide critical resources for resident and migratory populations of North American wood ducks (Aix sponsa). We studied radiomarked wood duck ducklings and females that nested in artificial structures and used floodplain palustrine, riverine, and lacustrine wetlands at Noxubee National Wildlife Refuge (NNWR) in Mississippi in 1996–1999 and the Tennessee-Tombigbee Rivers and Waterway (TTRW) in Alabama in 1998–1999. We estimated cause-specific mortality rates for 234 and 90 mortality events of wood duck ducklings at NNWR and TTRW, respectively. Composite estimates of duckling mortality rate for the brood rearing period across years and areas were avian (0.46; n  =  155), aquatic predators (0.23; n  =  79), snakes (0.06; n  =  21), mammals (0.05; n  =  18), exposure-related (0.02; n  =  7), and unknown causes (0.13; n  =  44). Based on this and a concurrent study, we recommend the following: 1) conserving suitable brood habitats, specifically scrub-shrub wetlands, without aggregations of nest boxes; 2) locating nest boxes amid or adjacent to these habitats in dispersed, non-aggregated arrangements; and 3) monitoring nest boxes throughout the nesting period, removing down feathers and unhatched eggs to promote use by nesting females and duckling production later in spring.

Swamp rabbits (Sylvilagus aquaticus) are bottomland hardwood forest specialists that may serve as useful indicators of ecosystem health. However, no studies have assessed the influence of both microhabitat and macrohabitat variables on relative abundance of swamp rabbits. To address this gap in the literature, we assessed the influence of landscape- and stand-level habitat variables on relative abundance of swamp rabbits in 29 floodplain forest sites in southern Illinois during 2006–2007. Swamp rabbits were detected at 69% of the sites surveyed. The median contiguity index of the landscape (a measure of patch size and spatial connectedness), the range in contiguity index of upland habitats, and tree stump density were positively and moderately related (w [i]  =  0.381–0.475) to relative abundance of swamp rabbits. Our results emphasize the importance of large unfragmented patches of floodplain forest habitat to swamp rabbits, and confirm that continued fragmentation of remaining habitat could have detrimental effects.

Floodplain ecosystems of the southeastern United States provide numerous services to society, but hydrologic and geomorphic alterations, agricultural practices, water quality and availability, and urban development continue to challenge restorationists and managers at multiple spatial and temporal scales. These challenges are further exacerbated by tremendous uncertainty regarding climate and land use patterns and natural variability in these systems. The symposium from which the papers in 2009 ensued was organized to provide a critical evaluation of current natural resource restoration and management practices to support the sustainability of floodplain ecosystem functions in the southeastern United States. In this paper we synthesize these concepts and evaluate restoration and conservation techniques in light of our understanding of these ecosystems. We also discuss current and future challenges and attempt to identify new approaches that may facilitate the long-term sustainability of southeastern floodplain systems. We conclude that integration of disciplines and approaches is necessary to meet the floodplain conservation challenges of the coming century. Integration will not only include purposeful dialogue between interdisciplinary natural resource professionals, but it also is necessary to sincerely engage the public about goals, objectives, and desirable outcomes of floodplain ecosystem restoration.

Wetlands of the Prairie Pothole Region of North America are vulnerable to climate change. Adaptation of farming practices to mitigate adverse impacts of climate change on wetland water levels is a potential watershed management option. We chose a modeling approach (WETSIM 3.2) to examine the effects of changes in climate and watershed cover on the water levels of a semi-permanent wetland in eastern South Dakota. Land-use practices simulated were unmanaged grassland, grassland managed with moderately heavy grazing, and cultivated crops. Climate scenarios were developed by adjusting the historical climate in combinations of 2°C and 4°C air temperature and ±10% precipitation. For these climate change scenarios, simulations of land use that produced water levels equal to or greater than unmanaged grassland under historical climate were judged to have mitigative potential against a drier climate. Water levels in wetlands surrounded by managed grasslands were significantly greater than those surrounded by unmanaged grassland. Management reduced both the proportion of years the wetland went dry and the frequency of dry periods, producing the most dynamic vegetation cycle for this modeled wetland. Both cultivated crops and managed grassland achieved water levels that were equal or greater than unmanaged grassland under historical climate for the 2°C rise in air temperature, and the 2°C rise plus 10% increase in precipitation scenarios. Managed grassland also produced water levels that were equal or greater than unmanaged grassland under historical climate for the 4°C rise plus 10% increase in precipitation scenario. Although these modeling results stand as hypotheses, they indicate that amelioration potential exists for a change in climate up to an increase of 2°C or 4°C with a concomitant 10% increase in precipitation. Few empirical data exist to verify the results of such land-use simulations; however, adaptation of farming practices is one possible mitigation avenue available for prairie wetlands.

Wetland rapid assessment has become popular in a variety of applications. Because rapid assessments rely on observable field indicators as surrogates for direct measures of condition, they must be validated against independent data. Here we present a case study of the validation of the riverine and estuarine modules of the California Rapid Assessment Method (CRAM). We evaluated responsiveness of the method to “good” vs. “poor” wetland condition, ability to represent a range of conditions, internal redundancy, alternative combination rules for constituent metrics, and reproducibility of results. Because no independent, concurrently collected measure of condition directly reflecting the same elements comprising CRAM was available for validation, we demonstrate the use of existing monitoring and assessment data on avian diversity, benthic macroinvertebrate indices, and plant community composition. Results indicate that CRAM is an effective tool for assessing general riverine and estuarine wetland condition based on its correspondence with multiple independent assessments of condition. Reproducibility analysis revealed several problematic metrics where ambiguous language or metric construction led to high inter-team error rates. Addressing these issues improved overall average error to within 5%. This study demonstrates that, when validated, rapid assessment methods provide a meaningful and reliable tool for assessing wetland condition.

Current methods of wetland assessment rely on the use of ecological indicators such as vegetation and amphibians, but often lack an in-depth analysis of soil parameters. The objective of this study was to determine whether the Ohio Rapid Assessment Method (ORAM) can be used to predict soil quality in forested wetlands. Soil cores were taken from six wetlands ranging in ORAM scores. The soil samples were analyzed for key soil parameters (aggregate stability, bulk density, organic matter, C, N, S, P, microbial biomass, and enzyme activity). Some of these soil parameters (i.e., microbial biomass, soil C, N and S, bulk density, soil moisture) were correlated with the ORAM scores, while others (i.e., P, pH, aggregate stability) showed no correlation. Enzyme activity was correlated with the ORAM score for one of the four sampling events. When analyzed together by a principal component analysis, the soil parameters did not separate the wetland sites along a gradient of ORAM scores. Our results indicate that the ORAM reflects some of the key soil quality conditions, but not all. We further discuss whether some of the soil parameters we selected are appropriate indicators of the quality of wetland soils.

We evaluated changes in wetland abundance, size, and classification between average (1979–1986) and above-average (1995–1999) precipitation periods for two physiographic regions in eastern South Dakota. Temporal shifts in wetland numbers, area, and class varied by topographic location. In high wetland density areas (> 8 wetlands/100 ha), our data suggests that larger, semipermanent wetlands expanded and absorbed nearby wetland basins into their margins, resulting in a net “loss” or disappearance of temporary and seasonal wetlands in above-average water condition years. “Losses” described here are not deemed permanent as in cases of draining or filling, and wetlands may re-form when water conditions return to normal. Nevertheless, temporary disappearance of smaller more isolated wetlands may have implications for breeding waterfowl and other fauna. Percent change of semipermanent basin numbers was positively correlated with wetland density, whereas the opposite was true for seasonal wetlands. Loss of temporary wetlands was correlated with wetland aggregation within the sample area. However, in low wetland density areas, the number and size of seasonal and temporary wetlands generally increased following above-average precipitation. We suggest that wetlands' spatial arrangement be considered along with traditional wetland quantification techniques to better account for shifts in wetland habitat in dry versus wet years.

Annual production of vegetation is an important indicator of various ecosystem processes in coastal marshes; many factors, both biotic and abiotic, can influence production of aboveground biomass. Using a 14-year data set, we evaluated the relative influence of 38 biotic and abiotic factors on annual aboveground biomass of an intermediate coastal marsh on the upper Gulf Coast of Texas. We used visual obstruction (VO) measurements as a surrogate variable in a prediction model to estimate available aboveground biomass in the marsh. Available biomass was greatest (3.34 kg/m²) when sampling site was flooded. Plant growth form, type of animal present, and composition of the ground cover influenced biomass of the marsh. Presence of insects was related to biomass (regression beta weight  =  0.28), uniquely accounting for 7.6% of the incremental variance in biomass. The presence of moderate amounts of litter was also related to available biomass (beta weight  =  0.86). Soil capping had little or no influence on aboveground biomass. Implementing standard protocols for long-term vegetation monitoring can be cost and time intensive. Our results suggest quantitative measurement of VO and qualitative observation of few variables (standing water, insects, and litter) measured annually can yield a reasonable assessment of aboveground biomass of intermediate coastal marshes.

Recent work has demonstrated the connection of seasonal pool-breeding amphibians to other local habitats such as forested wetlands and upland forests. However, the use of seasonal pools by facultative species is less well studied, particularly for highly aquatic species that breed in permanent waters such as American bullfrogs (Rana catesbeiana). Although movement between breeding ponds has been documented, evidence of bullfrog movement among breeding (permanent) and non-breeding (temporary) wetlands is scarce. Our objective was to determine the extent of bullfrog use of seasonal pools by examining movement patterns between breeding and non-breeding wetlands in Acadia National Park, Maine, USA. We examined patterns of bullfrog occupancy within one catchment using visual encounter surveys, mark-resighting, and radiotracking. Bullfrogs readily moved between wetlands with permanent and seasonal water regimes. Until pools completely dried, density of bullfrogs was greater in seasonal pools than in the permanent breeding ponds, underscoring the significance of seasonal pools as non-breeding habitat. The regularity of bullfrog use of seasonal pools throughout this study offers additional evidence for the role of seasonal pools as part of a habitat complex and highlights the importance of these habitats as features in a greater landscape context.

Low food availability and forage quality and concomitant decreased lipid reserves of lesser scaup (Aythya affinis; hereafter scaup) during spring migration in the upper Midwest may partially explain reductions in the continental population of scaup. In springs 2004–2005, we examined wetland use and feeding activity of scaup on 356 randomly-selected wetlands within 6 regions in Iowa, Minnesota, and North Dakota. We examined wetland characteristics that favor high scaup use in 286 of these wetlands. We found that probabilities of wetland use and feeding by scaup increased with turbidity up to 45 and 30 NTU, respectively, but then declined at higher turbidity levels. Wetland use was positively correlated with size of open-water zone and amphipod densities, but was not correlated with chironomid densities. Feeding increased with amphipod density up to 26 m⁻³ and then declined at higher amphipod densities; scaup seemingly forage most efficiently at amphipod densities above 26 m⁻³. Wetland use was higher in North Dakota than in southern Minnesota and Iowa. Our results indicate that effective wetland restoration efforts to benefit scaup require maintaining abundant populations of amphipods (generally near 26 m⁻³ landscape geometric mean) in wetlands with large (> 500 m diameter) open-water zones throughout the upper Midwest, but especially within Iowa and southern Minnesota.

Intensive management of wetlands to improve wildlife habitat typically includes the manipulation of water depth, duration, and timing to promote desired vegetation communities. Increased societal, industrial, and agricultural demands for water may encourage the use of alternative sources such as wastewater effluents in managed wetlands. However, water quality is commonly overlooked as an influence on wetland soil seed banks and soils. In four separate greenhouse trials conducted over a 2-yr period, we examined the effects of municipal wastewater effluent (WWE) on vegetation of wetland seed banks and soils excavated from a wildlife management area in Missouri, USA. We used microcosms filled with one of two soil materials and irrigated with WWE, Missouri River water, or deionized water to simulate moist-soil conditions. Vegetation that germinated from the soil seed bank was allowed to grow in microcosms for approximately 100 d. Vegetative taxa richness, plant density, and biomass were significantly reduced in WWE-irrigated soil materials compared with other water sources. Salinity and sodicity rapidly increased in WWE-irrigated microcosms and probably was responsible for inhibiting germination or interfering with seedling development. Our results indicate that irrigation with WWE promoted saline-sodic soil conditions, which alters the vegetation community by inhibiting germination or seedling development.

A recent decline in wild rice (Zizania palustris) wetlands has been observed. We assessed the factors significant in understanding the distribution of Z. palustris and the surrounding macrophyte community. Sixty historic wild rice wetlands that currently display a wide range of rice densities were sampled in Wisconsin and Minnesota (USA). Chemical and physical factors and aquatic plants densities were measured. Data were analyzed using Canonical Correspondence Analysis in which the following trends were found. Wetlands that exhibited the greatest loss of Zizania tended to have higher levels of residential development within their watershed, ammonia, pH and depth. The aquatic plant community also shifted to plants that likely benefited from increases in light and pollinators. Increased agriculture was correlated with higher nutrient levels and increases with floating plants that can acquire nutrients directly from the water column. This study suggests optimal conditions for wild rice as well as the aquatic plant communities that are associated with these conditions. This paper demonstrates that Zizania (and other aquatic plants) may be very sensitive to small changes within their watershed that are typical of moderate development. Future management strategies should include consideration of these land-use patterns.

The effects of sediment, ground-water, and surface-water processes on the timing, quantity, and mechanisms of N and P fluxes were investigated in the Wood River Wetland 5–7 years after agricultural practices ceased and seasonal and permanent wetland hydrologies were restored. Nutrient concentrations in standing water largely reflected ground water in winter, the largest annual water source in the closed-basin wetland. High concentrations of total P (22 mg L⁻¹) and total N (30 mg L⁻¹) accumulated in summer when water temperature, air temperature, and evapotranspiration were highest. High positive benthic fluxes of soluble reactive P and ammonium (NH₄ -N) were measured in two sections of the study area in June and August, averaging 46 and 24 mg m⁻² d⁻¹, respectively. Nonetheless, a wetland mass balance simultaneously indicated a net loss of P and N by assimilation, denitrification (1.1–10.1 mg N m⁻² h⁻¹), or solute repartitioning. High nutrient concentrations pose a risk for water quality management. Shifts in the timing and magnitude of water inflows and outflows may improve biogeochemical function and water quality by optimizing seed germination and aquatic plant distribution, which would be especially important if the Wood River Wetland was reconnected with hyper-eutrophic Agency Lake.

Aquatic herbaceous macrophytes contribute significantly to the input carbon for the Amazon floodplain. These plants have large seasonal variations in areal coverage and high productivity. The present study estimates annual net primary production (NPP) of aquatic herbaceous macrophytes in a large lake on the eastern Amazon floodplain, assesses the sources and amount of uncertainty associated with these measures, and offers a comparison among the estimates of herbaceous macrophyte productivity in the Amazon region. Plant biomass accumulated during the rising water stage of the annual flood cycle, peaking at 2300 to 6100 g m⁻² and decreasing later in the year. Annual net primary production was estimated to range from 2400 to 3500 g m⁻² yr⁻¹, with above water production between 650 and 1100 g m⁻² yr⁻¹, and below water production between 1700 and 2600 g m⁻² yr⁻¹. Echinochloa polystachya and Paspalum fasciculatum were the most productive species, followed by Paspalum repens, Hymenachne amplexicaulis, and Oryza perennis. The four main sources of uncertainty in the estimates were macrophyte taxa, location, sampling design, and lack of measurements of dead material loss.

Microalgae may contribute more to salt marsh productivity than realized, underscoring the importance of understanding algal dynamics in such systems. Benthic and planktonic chlorophyll-a (surrogate for total algal biomass), sediment ash-free dry weight, total suspended solids, salinity, and nutrients were examined in intermittently connected marsh ponds in the subtropical Guadalupe Estuary, Texas, USA to determine the effects of hydrologic connections on algal biomass in this system. From May 2005 to May 2006, several high water events resulting in surface water connections between ponds and nearby tidal creeks occurred, followed by disconnection and, at times, pond desiccation. During periods of disconnection, algal biomass was higher in both the benthos and the water column than during connection events when flushing occurred. Since connection events did not increase NO_x, the primary source of dissolved inorganic nitrogen seemed to be nutrient cycling within the ponds. Data at the aggregated level, i.e., chlorophyll-a, indicated this system followed the flood pulse concept. During high water events, algal biomass may be exported to supplement the tidal creek food web (aquatic), whereas during low water events accumulated biomass within the ponds feed the marsh food web (terrestrial), which includes blue crabs (Callinectes sapidus) and the whooping crane (Grus americana).

We combined literature reviews with an analysis of regional cartography, aerial photographs, and satellite images to identify the locations of heretofore-unknown salt marshes along the Patagonian coastline of Argentina. Subsequent ground surveys confirmed the presence of the marshes. While numerous sites still require verification, our surveys confirmed the existence of 27 large coastal salt marshes, which had estimated areas of between 3 and 2400 ha distributed along ∼225 km of coastline. We described the major patterns of landscape physiognomy and community structure at eight of these sites. We classified these marshes as either muddy or rocky marshes, and subdivided them into Spartina and Sarcocornia marshes depending on the dominant vegetation. Muddy marshes were the most common type and showed a clear regional pattern with Spartina-dominated communities in the north (≤ 42°S) and Sarcocornia-dominated systems in the south (≥ 42°S). Plant height and standing crop biomass tended to be lower at higher latitudes, but plant cover showed the opposite trend. Spartina marshes had a more diverse marine macro-invertebrate fauna than Sarcocornia marshes, when the two marsh types occur at similar latitudes. Although the diversity of invertebrates was relatively low along the entire latitudinal range, most marshes supported unique species assemblages.