Breeding Ecology of Mottled Ducks: A Review

Mottled ducks (Anas fulvigula) are endemic to the Gulf Coast of North America, and their range stretches from Alabama to the Laguna Madre of Mexico, with a distinct population in peninsular Florida and an introduced population in South Carolina. As one of the few non-migratory ducks in North America, mottled ducks depend on a variety of locally available habitat throughout the annual cycle, and threats to these landscapes may affect mottled ducks more acutely than migratory species. Annual population monitoring has revealed declines in mottled duck populations in Texas and Louisiana since 2008, and the genetic integrity of the Florida population has been muddled by the presence of large numbers of feral mallards (Anas platyrhynchos) resulting in hybridization. Similar to other closely related dabbling ducks, mottled duck populations are influenced by recruitment and breeding season survival, so changes in these factors may contribute to population decline. Accordingly, researchers have attempted to address various aspects of mottled duck breeding season ecology and population dynamics since the 1950s. We conducted a literature review on this topic by searching a combination of key terms using Google Scholar, including mottled duck, nesting ecology, habitat use, breeding incidence, nest success, brood, and breeding season survival, and followed citation trees to eventually aggregate information from nearly 50 publications on mottled duck breeding ecology. Our review concluded that mottled ducks use brackish and intermediate coastal marsh, including managed impoundments, and agricultural land during the breeding season. Their nests can be found in pastures, levees, dry cordgrass marsh, cutgrass marsh, spoil banks, and small islands. Nesting propensity and nest success estimates are often lower than other waterfowl species that are characterized by stable or increasing populations. Broods use wetlands composed of a mix of open water with submerged and emergent vegetation. Breeding season survival is higher for the Florida population than the western Gulf Coast population, but adult survival in both geographies is comparable to (or higher than) that of other dabbling duck species. Breeding habitat use, breeding season survival, and nest-site selection and success have been studied extensively in mottled ducks, whereas information on nesting propensity, renesting intensity, and post-hatch ecology is lacking. © 2021 The Wildlife Society.     

Salt marsh elevation is a strong determinant of nest‐site selection by Clapper Rails in Georgia,USA

As sea levels rise, birds nesting in coastal marshes will be particularly vulnerable to increased tidal inundation. Understanding how marsh birds select their nesting habitat along the elevational gradient of these marshes will provide insight into how these species might be affected by rising sea levels. Clapper Rails (Rallus crepitans) are coastal marsh‐nesting birds whose nests are vulnerable to flooding, but it is not clear if they select for habitat along the elevational gradient or only use other habitat cues. Our objective was to determine if Clapper Rails select higher‐elevation nest sites, while also controlling for selection of other habitat variables at both landscape and territory levels, by comparing nest habitat to habitat in other areas of territories and at random points in the marsh landscape. At the landscape level, Clapper Rails did not exhibit selection for the elevational gradient, with nests and random points at similar elevations. At the territory level, however, nest‐site selection was most influenced by elevation and plant height, with Clapper Rails selecting nest sites with higher elevations and in areas with taller plants. However, the strength of the elevation effect was uncertain, suggesting the importance of precise elevation measurements in the field. Given this selection for higher‐elevation nest sites, Clapper Rails may be somewhat resilient to increased tidal inundation. However, the potential for increased intra‐ and interspecific competition for high‐elevation marshes should make conservation of these habitats a priority.     

Habitat selection of nesting and fledgling salt marsh songbirds in northeast Florida

Understanding habitat selection by breeding birds and their newly fledged young can be an essential aspect of the conservation of vulnerable species. During 2015–2017, we examined nest site selection of Worthington's marsh wren (Cistothorus palustris griseus) and MacGillivray's seaside sparrow (Ammospiza maritima macgillivraii), and fledgling habitat use by Worthington's marsh wren, 2 imperiled species in northeast Florida, USA. We compared vegetation at unused points to vegetation at nests of both subspecies and at locations used by radio-tagged marsh wren fledglings. Vegetation was taller and stem counts were greater at nest sites compared to unused points. Worthington's marsh wrens also used nest sites with a greater proportion of tall-form smooth cordgrass (Spartina alterniflora) than was observed at unused points. Worthington's marsh wren fledglings also used locations with taller, denser vegetation, but vegetation use changed with fledgling age and tidal stage; older fledglings more frequently used areas with short-form smooth cordgrass and bare ground (and more so during low tides). In contrast, so few nests and nestlings were in black needlerush (Juncus roemerianus) that we could not consider it in our analysis despite its prevalence within our study sites. Our results indicate that tall, dense cordgrass is an important habitat component for these subspecies during the nesting and fledgling life stages in southeastern Atlantic salt marshes.     

Food Resources for Wintering and Spring Staging Black Ducks

Abstract: A bioenergetic approach has been adopted as a planning tool to set habitat management objectives by several United States Fish and Wildlife Service North American Waterfowl Management Plan Joint Ventures. A bioenergetics model can be simplified into 2 major components, energetic demand and energetic supply. Our goal was to estimate habitat-specific food availability, information necessary for estimating energy supply for black ducks (Anas rubripes) wintering on Long Island, New York, USA. We collected both nektonic and benthic samples from 85 wetland sites dispersed among 5 habitat types (salt marsh, mud flat, submersed aquatic vegetation, brackish bay, and freshwater) commonly used by black ducks in proportion to expected use. Biomass varied among habitats (F_4,5 > 7.46, P < 0.03) in 2004–2005, but there was only marginal variation in 2005–2006 (F_3,4 = 5.75, P = 0.06). Mud flats had the greatest biomass (1,204 kg/ha, SE = 532), followed by submersed aquatic vegetation (61 kg/ha, SE = 18), and salt marsh (34 kg/ha, SE = 6). In the second year of the study, freshwater had the greatest biomass (306 kg/ha, SE = 286), followed by mud flats (85 kg/ha, SE = 63), and salt marsh (35 kg/ha, SE = 4). Our results suggest food density on wintering grounds of black ducks on coastal Long Island is considerably lower than for dabbling ducks using inland freshwater habitats, indicating black duck populations are more likely than other species of dabbling ducks to be limited by winter habitat. We recommend targeting preservation, restoration, and enhancement efforts on salt marsh habitat.     

Microhabitat nest‐site selection by ducks in the boreal forest

The boreal forest is one of the North America’s most important breeding areas for ducks, but information about the nesting ecology of ducks in the region is limited. We collected microhabitat data related to vegetation structure and composition at 157 duck nests and paired random locations in Alberta’s boreal forest region from 2016 to 2018. We identified fine‐scale vegetation features selected by ducks for all nests, between nesting guilds, and among five species using conditional logistic regression. Ducks in the boreal forest selected nest sites with greater overhead and graminoid cover, but less forb cover than random sites. Characteristics of the nest sites of upland‐ and overwater‐nesting guilds differed, with species nesting in upland habitat selecting nests that provided greater shrub cover and less lateral concealment and species nesting over water selecting nests with less shrub cover. We examined the characteristics of nest sites of American Wigeon (Mareca americana), Blue‐winged Teal (Spatula discors), Green‐winged Teal (Anas crecca), Mallards (Anas platyrhynchos), and Ring‐necked Ducks (Aythya collaris), and found differences among species that may facilitate species coexistence at a regional scale. Our results suggest that females of species nesting in upland habitat selected nest sites that optimized concealment from aerial predators while also allowing detection of and escape from terrestrial predators. Consequently, alteration in the composition and heterogeneity of vegetation and predator communities caused by climate change and industrial development in the boreal forest of Canada may affect the nest‐site selection strategies of boreal ducks.     

Living Shorelines: Coastal Resilience with a Blue Carbon Benefit

Living shorelines are a type of estuarine shoreline erosion control that incorporates native vegetation and preserves native habitats. Because they provide the ecosystem services associated with natural coastal wetlands while also increasing shoreline resilience, living shorelines are part of the natural and hybrid infrastructure approach to coastal resiliency. Marshes created as living shorelines are typically narrow (< 30 m) fringing marshes with sandy substrates that are well flushed by tides. These characteristics distinguish living shorelines from the larger meadow marshes in which most of the current knowledge about created marshes was developed. The value of living shorelines for providing both erosion control and habitat for estuarine organisms has been documented but their capacity for carbon sequestration has not. We measured carbon sequestration rates in living shorelines and sandy transplanted Spartina alterniflora marshes in the Newport River Estuary, North Carolina. The marshes sampled here range in age from 12 to 38 years and represent a continuum of soil development. Carbon sequestration rates ranged from 58 to 283 g C m^-2 yr^-1 and decreased with marsh age. The pattern of lower sequestration rates in older marshes is hypothesized to be the result of a relative enrichment of labile organic matter in younger sites and illustrates the importance of choosing mature marshes for determination of long-term carbon sequestration potential. The data presented here are within the range of published carbon sequestration rates for S. alterniflora marshes and suggest that wide-scale use of the living shoreline approach to shoreline management may come with a substantial carbon benefit.     

Effects of Rotational Grazing on Nesting Ducks in California

Abstract: Grazing is thought to be incompatible with nesting by dabbling ducks (Anas spp.), but this belief is based on little data. We therefore conducted a 2-year, replicated field experiment to determine whether the habitat requirements of nesting ducks could be met on uplands managed by rotational grazing (1 Jul-1 Nov) in the northern San Joaquin Valley, California, USA. Grazed fields had shorter vegetation than ungrazed fields throughout the winter, but vegetation height did not differ by the beginning of the nesting season in late March, and by the end of the nesting season in late May, previously grazed fields had taller vegetation than did ungrazed fields. In 1996, densities of duck nests were >3 times higher in grazed than in ungrazed fields (least-squares means [± 1 SE]: grazed = 2.18 [0.34] nests/ha, ungrazed = 0.59 [0.34] nests/ha), but nest densities were substantially lower in 1997 and did not differ between treatment groups (grazed = 0.65 [0.32] nests/ha, ungrazed = 0.39 [0.32] nests/ha). Mayfield nest success did not differ between grazed fields (5.3%) and ungrazed fields (2.9%). We conclude that rotational grazing was successful in providing summer nesting habitat for dabbling ducks, and we recommend that it be considered for other managed habitats within the Central Valley, California, USA.     

Zonation of spiders (Araneae) and carabid beetles (Coleoptera: Carabidae) in island salt marshes at the North Sea coast

The specific communities of spiders and carabid beetles of island salt marsh habitats of the East Frisian Island chain at the German North Sea coast were investigated. During the vegetation periods of 1997 and 1998 three pitfall trapping transects were installed on the islands of Borkum and Wangerooge. Within the salt marshes, transects extended from 0 m to 175 m. Elevation gradients varied between 10 cm and 232 cm above MHT (mean high tide). On Borkum, 35 traps were exposed in two transects, on Wangerooge 25 traps were placed in one transect. Three to five elevations above MHT were investigated per transect, each one with five traps. Highest species numbers were recorded in the higher elevated salt marshes. In contrast, highest activity values were noticed in the medium elevated salt marshes. Within both groups, spiders and carabids, four communities were distinguished by indirect gradient analysis. Indicator species were assigned to the different communities that were mainly assorted to different elevations of the salt marshes. Thus, the communities of both taxa corresponded well to the vegetational formations. The importance of sea level rise for structuring the communities of salt marsh arthropods is discussed. Overall, still great uncertainties exist on how arthropod communities and salt marshes themselves will develop.     

Salt tolerance and osmotic adjustment of Spartina alterniflora (Poaceae) and the invasive M haplotype of Phragmites australis (Poaceae) along a salinity gradient

An invasive variety of Phragmites australis (Poaceae, common reed), the M haplotype, has been implicated in the spread of this species into North American salt marshes that are normally dominated by the salt marsh grass Spartina alterniflora (Poaceae, smooth cordgrass). In some European marshes, on the other hand, Spartina spp. derived from S. alterniflora have spread into brackish P. australis marshes. In both cases, the non-native grass is thought to degrade the habitat value of the marsh for wildlife, and it is important to understand the physiological processes that lead to these species replacements. We compared the growth, salt tolerance, and osmotic adjustment of M haplotype P. australis and S. alterniflora along a salinity gradient in greenhouse experiments. Spartina alterniflora produced new biomass up to 0.6 M NaCl, whereas P. australis did not grow well above 0.2 M NaCl. The greater salt tolerance of S. alterniflora compared with P. australis was due to its ability to use Na(+) for osmotic adjustment in the shoots. On the other hand, at low salinities P. australis produced more shoots per gram of rhizome tissue than did S. alterniflora. This study illustrates how ecophysiological differences can shift the competitive advantage from one species to another along a stress gradient. Phragmites australis is spreading into North American coastal marshes that are experiencing reduced salinities, while Spartina spp. are spreading into northern European brackish marshes that are experiencing increased salinities as land use patterns change on the two continents.     

Habitat size, flora, and fauna: Interactions in a tidal saltwater marsh

Anthropogenic habitat fragmentation is increasingly problematic in both terrestrial and aquatic systems. Fragmentation reduces the size of habitat patches, so examining the effect of patch size on community structure can provide insight into the potential effects of fragmentation. In this study, we examined the effect of habitat size on the density of Spartina alterniflora shoots in tidal saltwater marshes, as well as on the two predominant macrofaunal species, the marsh periwinkle Littoraria irrorata and fiddler crabs Uca spp. We estimated the density of shoots in three different marsh habitats, (1) large island marshes, (2) small island marshes, and (3) large fringing marshes, in Indian Field Creek, York River, Chesapeake Bay. We manipulated shoot density in each of the marsh types to distinguish between the effects of marsh grass density and marsh type on crab and Littoraria densities in the system. We found significant differences in grass density among the three marsh types as well as significant species-specific effects of grass density, marsh type, and distance from edge on faunal abundance. Decreasing the shoot density resulted in a decrease in Littoraria density in the large marshes. Littoraria density increased with distance from edge in the small marshes and in the first 5 m of the fringing marshes, then decreased with distance from edge after 5 m in the fringing marshes. Shoot density had a negative effect on crabs in both the large and small marshes. These results suggest that fragmentation would have a negative effect on the community structure by lowering the densities of both the flora and fauna.     

Climate change and loss of saltmarshes: consequences for birds

Saltmarshes are areas of vegetation subject to tidal inundation and are important to birds for several reasons. Saltmarshes are areas of high primary productivity and their greatest significance for coastal birds is probably as the base of estuarine food webs, because saltmarshes export considerable amounts of organic carbon to adjacent habitats, particularly to the invertebrates of mudflats. In addition, saltmarshes are of direct importance to birds by providing sites for feeding, nesting and roosting. Climate change can affect saltmarshes in a number of ways, including through sea-level rise. When sea-level rises the marsh vegetation moves upward and inland but sea walls that prevent this are said to lead to coastal squeeze and loss of marsh area. However, evidence from southeast England, and elsewhere, indicates that sea-level rise does not necessarily lead to loss of marsh area because marshes accrete vertically and maintain their elevation with respect to sea-level where the supply of sediment is sufficient. Organogenic marshes and those in areas where sediment may be more limiting (e.g. some west coast areas) may be more susceptible to coastal squeeze, as may other marshes, if some extreme predictions of accelerated rates of sea-level rise are realized.     

Nest occurrence and survival of King Rails in fire‐managed coastal marshes in North Carolina and Virginia

Prescribed burning maintains marsh habitat, but its impact on breeding King Rails (Rallus elegans) is poorly understood. This practice may serve as a means to enhance populations of a species whose numbers are declining in the southeastern United States. We used call‐broadcast surveys and nest searches to categorize the state of occupied plots by the presence or non‐presence of nesting activity in the Back Bay region, North Carolina and Virginia, in 2010. We also used nest video surveillance to estimate nest survival in 2009 and 2010. The probabilities that a surveyed plot was occupied (¹) and contained an active nest (²) were higher in recently burned marsh plots (0–1 year‐since‐burn [YSB]) than in plots with ≥2 YSB at Mackay Island and Back Bay National Wildlife Refuges (NWRs). Highest probabilities were recorded in 0–1 YSB plots at Mackay Island NWR ( = 0.96 ± 0.04, = 0.75 ± 0.18), and the lowest in ≥2 YSB plots at Back Bay NWR ( = 0.21 ± 0.10, = 0.03 ± 0.04). Nest survival from egg laying to hatching (31 d) was 0.48 (95% confidence interval [CI] = 0.06–0.83), with an estimated 0.79 (95% CI = 0.29–0.96) survival rate for the incubation stage (21 d). These nest survival estimates for King Rails in fire‐managed marshes were similar to estimates for other populations. Measures of vegetation cover, proxies for concealment, did not differ between nest sites and unused sites, even within recently burned marshes. This lack of differences in vegetation structure suggests that regrowth occurs rapidly during the period between burning (winter months) and the onset of reproduction (late April). Thus, recently burned marshes may benefit nesting King Rails by providing nest concealment. In addition, burned marshes may enhance availability of many invertebrates. Although we found that the probability that surveyed plots contained active nests was higher in recently burned marsh plots, estimates of fledging success are needed before marsh burns can be considered an effective means of fostering population growth.     

Optimal hurricane overwash thickness for maximizing marsh resilience to sea level rise

The interplay between storms and sea level rise, and between ecology and sediment transport governs the behavior of rapidly evolving coastal ecosystems such as marshes and barrier islands. Sediment deposition during hurricanes is thought to increase the resilience of salt marshes to sea level rise by increasing soil elevation and vegetation productivity. We use mesocosms to simulate burial of Spartina alterniflora during hurricane‐induced overwash events of various thickness (0–60 cm), and find that adventitious root growth within the overwash sediment layer increases total biomass by up to 120%. In contrast to most previous work illustrating a simple positive relationship between burial depth and vegetation productivity, our work reveals an optimum burial depth (5–10 cm) beyond which burial leads to plant mortality. The optimum burial depth increases with flooding frequency, indicating that storm deposition ameliorates flooding stress, and that its impact on productivity will become more important under accelerated sea level rise. Our results suggest that frequent, low magnitude storm events associated with naturally migrating islands may increase the resilience of marshes to sea level rise, and in turn, slow island migration rates. Synthesis: We find that burial deeper than the optimum results in reduced growth or mortality of marsh vegetation, which suggests that future increases in overwash thickness associated with more intense storms and artificial heightening of dunes could lead to less resilient marshes.     

Cavity use and breeding biology of endangered Bahama Swallows (Tachycineta cyaneoviridis): implications for conservation

Bird populations, especially on islands, have declined or gone extinct due to overhunting, habitat loss and fragmentation, and adverse effects of the introduction of non-native species. Bahama Swallows (Tachycineta cyaneoviridis), endangered secondary cavity nesters that breed on only three islands in the northern Bahamas, are an island species with a declining population, but the causes of this decline are unknown. During four breeding seasons on Great Abaco Island (2014–2017), we identified cavity-nesting resources used by breeding swallows in native pine forest and other habitats, and estimated phenology and breeding parameters from a subset of nests. Bahama Swallows nest in cavities in a variety of structures, but rely most on woodpecker-excavated cavities in pine snags and utility poles. Swallows nesting in cavities in pine snags had higher fledging success (92%) than those nesting in cavities in utility poles (50–62%), which were concentrated in non-pine habitat that may expose swallows to predation and increased competition for nest cavities from other species. The high reproductive success of Bahama Swallows nesting in the pine forest indicates that the decline in population cannot be attributed to poor productivity on southern Great Abaco. However, our results suggest that the dependence of Bahama Swallows on cavities excavated by Hairy Woodpeckers (Dryobates villosus) for nesting sites may be a factor in their decline, and highlight the potential importance of the protection and management of pine forests in future efforts to ensure the survival of Bahama Swallows.     

Ecological responses to tidal restorations of two northern New England salt marshes

Efforts are underway to restore tidal flow in New England salt marshes that were negatively impacted by tidal restrictions. We evaluated a planned tidal restoration at Mill Brook Marsh (New Hampshire) and at Drakes Island Marsh (Maine) where partial tidal restoration inadvertently occurred. Salt marsh functions were evaluated in both marshes to determine the impacts from tidal restriction and the responses following restoration. Physical and biological indicators of salt marsh functions (tidal range, surface elevations, soil water levels and salinities, plant cover, and fish use) were measured and compared to those from nonimpounded reference sites. Common impacts from tidal restrictions at both sites were: loss of tidal flooding, declines in surface elevation, reduced soil salinity, replacement of salt marsh vegetation by fresh and brackish plants, and loss of fish use of the marsh.Water levels, soil salinities and fish use increased immediately following tidal restoration. Salt-intolerant vegetation was killed within months. After two years, mildly salt-tolerant vegetation had been largely replaced in Mill Brook Marsh by several species characteristic of both high and low salt marshes. Eight years after the unplanned, partial tidal restoration at Drakes Island Marsh, the vegetation was dominated bySpartina alterniflora, a characteristic species of low marsh habitat.Hydrologic restoration that allowed for unrestricted saltwater exchange at Mill Brook restored salt marsh functions relatively quickly in comparison to the partial tidal restoration at Drakes Island, where full tidal exchange was not achieved. The irregular tidal regime at Drakes Island resulted in vegetation cover and patterns dissimilar to those of the high marsh used as a reference. The proper hydrologic regime (flooding height, duration and frequency) is essential to promote the rapid recovery of salt marsh functions. We predict that functional recovery will be relatively quick at Mill Brook, but believe that the habitat at Drakes Island will not become equivalent to that of the reference marsh unless the hydrology is further modified.Corresponding Editor: R.E. Turner Manuseript     

Ecological responses to tidal restorations of two northern New England salt marshes

Efforts are underway to restore tidal flow in New England salt marshes that were negatively impacted by tidal restrictions. We evaluated a planned tidal restoration at Mill Brook Marsh (New Hampshire) and at Drakes Island Marsh (Maine) where partial tidal restoration inadvertently occurred. Salt marsh functions were evaluated in both marshes to determine the impacts from tidal restriction and the responses following restoration. Physical and biological indicators of salt marsh functions (tidal range, surface elevations, soil water levels and salinities, plant cover, and fish use) were measured and compared to those from nonimpounded reference sites. Common impacts from tidal restrictions at both sites were: loss of tidal flooding, declines in surface elevation, reduced soil salinity, replacement of salt marsh vegetation by fresh and brackish plants, and loss of fish use of the marsh. Water levels, soil salinities and fish use increased immediately following tidal restoration. Salt-intolerant vegetation was killed within months. After two years, mildly salt-tolerant vegetation had been largely replaced in Mill Brook Marsh by several species characteristic of both high and low salt marshes. Eight years after the unplanned, partial tidal restoration at Drakes Island Marsh, the vegetation was dominated bySpartina alterniflora, a characteristic species of low marsh habitat. Hydrologic restoration that allowed for unrestricted saltwater exchange at Mill Brook restored salt marsh functions relatively quickly in comparison to the partial tidal restoration at Drakes Island, where full tidal exchange was not achieved. The irregular tidal regime at Drakes Island resulted in vegetation cover and patterns dissimilar to those of the high marsh used as a reference. The proper hydrologic regime (flooding height, duration and frequency) is essential to promote the rapid recovery of salt marsh functions. We predict that functional recovery will be relatively quick at Mill Brook, but believe that the habitat at Drakes Island will not become equivalent to that of the reference marsh unless the hydrology is further modified.     

千岛湖栖息地片段化对大山雀营巢资源利用的影响

为了解栖息地片段化对次级洞巢鸟营巢资源利用的影响, 我们于2008年2-8月, 在千岛湖地区选取21个岛屿, 采用悬挂人工巢箱方法进行大山雀(Parus major)招引实验。通过测定岛屿面积、岛屿隔离度、捕食者活动率、人工巢箱周围植被盖度和人工巢箱巢向等5种参数, 分析大山雀人工巢箱利用与上述参数间的关系。实验期间, 共悬挂443个人工巢箱, 其中有72个(16.3%)被大山雀利用。大山雀倾向于选择捕食者活动率低、植被盖度低、巢口向东或向南的人工巢箱; 岛屿面积和隔离度对大山雀利用人工巢箱不存在显著的直接影响, 但岛屿面积可通过影响捕食者的活动率, 对大山雀利用人工巢箱产生间接影响。因此, 我们认为在栖息地片段化后, 应更多关注对洞巢鸟营巢资源利用有直接影响的栖息地特征因素, 以及片段化效应的间接影响。     

Fifteen Years of Vegetation and Soil Development after Brackish-Water Marsh Creation

Aboveground biomass, macro‐organic matter (MOM), and wetland soil characteristics were measured periodically between 1983 and 1998 in a created brackish‐water marsh and a nearby natural marsh along the Pamlico River estuary, North Carolina to evaluate the development of wetland vegetation and soil dependent functions after marsh creation. Development of aboveground biomass and MOM was dependent on elevation and frequency of tidal inundation. Aboveground biomass of Spartina alterniflora, which occupied low elevations along tidal creeks and was inundated frequently, developed to levels similar to the natural marsh (750 to 1,300 g/m²) within three years after creation. Spartina cynosuroides, which dominated interior areas of the marsh and was flooded less frequently, required 9 years to consistently achieve aboveground biomass equivalent to the natural marsh (600 to 1,560 g/m²). Aboveground biomass of Spartina patens, which was planted at the highest elevations along the terrestrial margin and seldom flooded, never consistently developed aboveground biomass comparable with the natural marsh during the 15 years after marsh creation. MOM (0 to 10 cm) generally developed at the same rate as aboveground biomass. Between 1988 and 1998, soil bulk density decreased and porosity and organic C and N pools increased in the created marsh. Like vegetation, wetland soil development proceeded faster in response to increased inundation, especially in the streamside zone dominated by S. alterniflora. We estimated that in the streamside and interior zones, an additional 30 years (nitrogen) to 90 years (organic C, porosity) are needed for the upper 30 cm of created marsh soil to become equivalent to the natural marsh. Wetland soil characteristics of the S. patens community along upland fringe will take longer to develop, more than 200 years. Development of the benthic invertebrate‐based food web, which depends on organic matter enrichment of the upper 5 to 10 cm of soil, is expected to take less time. Wetland soil characteristics and functions of created irregularly flooded brackish marshes require longer to develop compared with regularly flooded salt marshes because reduced tidal inundation slows wetland vegetation and soil development. The hydrologic regime (regularly vs. irregularly flooded) of the “target” wetland should be considered when setting realistic expectations for success criteria of created and restored wetlands.     

Restoration of the Sieperda Tidal Marsh in the Scheldt Estuary, The Netherlands

Because of land reclamation, reinforcement of dikes, and the deepening of shipping channels, large areas of tidal marshes have been removed or eroded from the Scheldt estuary during the last two centuries. Tidal wetland restoration contributes toward compensating this loss of habitat. Not all restoration projects are meticulously planned, however; some are forced by nature. During a severe storm in 1990, a dike was breached in the brackish part of the Scheldt estuary and returned tidal influence to the Sieperda polder. In the 10 years since the dike breach, the former polder has changed into a brackish tidal marsh. Here we report on the geomorphologic and ecological developments that have taken place in the marsh. Tidal intrusion into the former polder turned crop fields into mudflats and changed pastures into salty marsh vegetation. The digging of a new creek improved marsh hydrology and enhanced tidal intrusion further into the marsh. Macrofauna typical of estuarine mudflats established rapidly in the developing marsh. Vegetation succession took place rapidly. Within 5 years, large areas of mudflats became covered with marsh vegetation. Birds characteristic of salt marshes were observed breeding or seen foraging in the marsh. The number of wading birds declined as areas of mudflat became overgrown. It is demonstrated that tidal flow is the engine to tidal marsh restoration. Tidal influence caused geomorphologic changes, which directed ecological developments in the former polder.     

Connectivity in coastal systems: Barrier island vegetation influences upland migration in a changing climate

Due to their position at the land–sea interface, barrier islands are vulnerable to both oceanic and atmospheric climate change‐related drivers. In response to relative sea‐level rise, barrier islands tend to migrate landward via overwash processes which deposit sediment onto the backbarrier marsh, thus maintaining elevation above sea level. In this paper, we assess the importance of interior upland vegetation and sediment transport (from upland to marsh) on the movement of the marsh–upland boundary in a transgressive barrier system along the mid‐Atlantic Coast. We hypothesize that recent woody expansion is altering the rate of marsh to upland conversion. Using Landsat imagery over a 32 year time period (1984–2016), we quantify transitions between land cover (bare, grassland, woody vegetation, and marsh) and the marsh–upland boundary. We find that the Virginia Barrier Islands have both gains and losses in backbarrier marsh and upland, with 19% net loss from the system during the timeframe of the study and increased variance in marsh to upland conversion. This is consistent with recent work indicating a shift toward increasing rates of landward barrier island migration. Despite a net loss of upland area, macroclimatic winter warming resulted in 41% increase in woody vegetation in protected, low‐elevation areas, introducing new ecological scenarios that increase resistance to sediment movement from upland to marsh. Our analysis demonstrates how the interplay between elevation and interior island vegetative cover influences landward migration of the boundary between upland and marsh (a previously underappreciated indicator that an island is migrating), and thus, the importance of including ecological processes in the island interior into coastal modeling of barrier island migration and sediment movement across the barrier landscape.