Scirpus Acutus Research Articles

Selenium Removal by Sediments and Plants at the Constructed Pariette Wetlands, Utah (USA)

Selenium (Se) contamination of public lands and water is a result of irrigated agriculture and mining activities in areas rich in Se geologic deposits. Pariette Draw is part of the northern Colorado Plateau and is an area of concern for Se contamination in the Pariette Wetlands. Pariette Wetlands, a wetland built in the 1970s to provide wildlife habitat, is distinguished by its arid climate and a short growing season of hot dry summers followed by cold winters with several months below freezing. An understanding of how Se is mobilized and removed within the wetland will provide management strategies that minimize and mitigate Se contamination and promote sustainable ecosystem services. The data collected in 2012 and 2014 was the first comprehensive spatial and temporal analysis of Se in all environmental compartments (bird eggs, macroinvertebrates, plants, sediments, and water) of an arid wetland ecosystem in the Colorado Plateau. Water, sediment, and plant tissue samples were collected and analyzed to determine Se’s spatial and temporal variation in Pariette Wetlands. Se concentrations in water, sediment, and plants were evenly distributed throughout wetlands. No significant differences were found in plant Se concentrations between samples collected in 2012 (447 ± 44 ug kg−1) or 2014 (541 ± 42 μg kg−1), indicating that plant Se did not vary temporally during sampling. Aquatic plant species (e.g., pondweed (Potamogeton filiformis), 743 ± 66 μg kg−1 and watermilfoil (Myriophyllum spicatum), 874 ± 122 μg kg−1) accumulated more Se than plant species growing at the edges of the ponds (e.g., hardstem bulrush (Schoenoplectus acutus), 368 ± 37 μg kg−1 and cattail (Typha), 420 ± 43 μg kg−1). Plant roots (1045 ± 110 μg kg−1) accumulated more Se than aboveground vegetation (flowers, 228 ± 17 μg kg−1 or stems, 224 ± 19 μg kg−1). Relative to Se retained by sediments (75%), plants were not an extensive reservoir of wetland Se (<5%) but still may pose a risk to animals feeding on plant tissue. Thus, phytoremediation of Se does not appear to be a viable tool for Se mitigation in wetlands of arid climates with a short growing season, such as those located in the Colorado Plateau.

Wetland phosphorus dynamics and phosphorus removal potential.

Wetlands are typically defined as inundated areas with hydric soils forming a transitional zone between terrestrial and aquatic systems. Wetlands have numerous ecosystem benefits, one of which is the potential to mitigate or reverse eutrophication of surface water bodies. The physical, chemical, and biological processes governing phosphorus cycling in wetlands are nuanced and complex; understanding these has direct relevance to the restoration of wetlands, particularly for projects aimed at improving water quality in adjacent water bodies. This literature review summarizes these processes and provides recommendations relevant to restoration of permanent and semipermanent flow-through wetlands, such as those in the Upper Klamath Basin of Oregon. It also reviews several wetland restoration studies assessing phosphorus removal. In summary, appropriately designed and managed wetlands can remove 25% to 44% of inflowing total phosphorus. Deposition of particulate matter, adsorption, uptake by biomass, and peat accretion are the primary phosphorus sequestration mechanisms in wetlands, depending on site-specific conditions (e.g., growing season length, vegetation communities, and soil type). In areas with relatively short growing seasons and where wintertime loads are targeted for treatment, as in the Upper Klamath Basin, deposition of particulate matter will be the primary mechanism for phosphorus sequestration in wetlands given that two of the three remaining processes occur during the growing season. Recommendations to maximize phosphorus sequestration in wetlands include the following: designing wetlands for hydraulic residence time of several days to weeks, managing wetlands for rapid establishment of wetland vegetation with limited decomposition potential (e.g., tule [hardstem bulrush] to facilitate peat accretion), and flooding during periods with low water temperatures and initially isolating restored wetlands from adjacent water bodies (both to minimize diffusive flux of phosphorus from wetland sediment to the water column). Relevant to the Upper Klamath Basin, there is also justification to prioritize areas with relatively high particulate phosphorus load given the potential limited capacity for phosphorus treatment associated with other sequestration mechanisms. Finally, a combination of mitigation and restoration strategies is necessary to achieve water quality objectives, meaning that wetland restoration alone may not be sufficient. Monitoring is advised to facilitate application of adaptive management principles. PRACTITIONER POINTS: Appropriately designed and managed wetlands can remove 25% to 44% of inflowing total phosphorus. Deposition of particulate matter, adsorption, uptake by biomass, and peat accretion are the primary phosphorus sequestration mechanisms in wetlands, depending on site-specific conditions (e.g., growing season length, vegetation communities, and soil type). Recommendations to maximize phosphorus sequestration in wetlands include designing wetlands for hydraulic residence time of several days to weeks; managing wetlands for rapid establishment of wetland vegetation with limited decomposition potential (e.g., tule [hardstem bulrush], to facilitate peat accretion); and flooding during periods with low water temperatures and initially isolating restored wetlands from adjacent water bodies (both to minimize diffusive flux of phosphorus from wetland sediment to the water column). A combination of mitigation and restoration strategies are necessary to achieve water quality objectives, meaning that wetland restoration alone may not be sufficient. Monitoring is advised to facilitate application of adaptive management principles.

Metal concentrations in wetland plant tissues influences transfer to terrestrial food webs.

Wetland plants tolerate potentially hazardous metals through a variety of strategies, including exclusion or accumulation. Whether plants sequester metals and where they store them in their tissues is important for understanding the potential role of plants as remediators or vectors of metals to terrestrial food webs. Here we evaluate metal sequestration in Great Salt Lake wetlands for one invasive (Phragmites australis; phragmites) and three native plant species, i.e. threesquare bulrush (Schoenoplectus americanus), hardstem bulrush (Schoenoplectus acutus), alkali bulrush (Bolboschoenus maritimus), and their terrestrial invertebrates. We observed higher concentrations of arsenic and copper than other metals in plant tissues, although high lead concentrations were observed in phragmites. All plants acted as excluders of arsenic and selenium, retaining the bulk of the metal mass in belowground tissues. In contrast, lead, copper, and cadmium were transferred to above ground tissues of hardstem bulrush and phragmites. The aboveground translocation facilitated the movement of these metals into invertebrates, with the highest concentrations in most cases found in predators. Though our results highlight the potential for metal remediation via wetland plant growth and removal, care should be taken to ensure that remediation efforts do not lead to bioaccumulation.

Effectiveness of combined tools: adsorption, bioaugmentation and phytoremediation for pesticides removal from wastewater

The aim of this study was the comparison of two process in pentachlorophenol (PCP: 100 mg L−1) removal by combined process bioaugmentation-adsorption and bioaugmentation-phytoremediation in secondary treated wastewater (STWW). The phytoremediation procedure was conducted by using two plants such as Typha angustifolia and Schoenoplectus acutus, and the bioaugmentation procedure was operated by Pseudomonas putida HM 627618 as a plant growth promoting bacteria (PGPR). The adsorption process was performed by palm date activated carbon. The PCP monitoring was assessed by high performance liquid chromatography (HPLC) and the optical density determination at 600 nm (OD600). The performance of the two processes was observed by the determination of total bacteria, chlorophylls and physical and chemical analysis (COD, pH, conductivity, chloride, and organic carbon). The alfalfa seed germination test was conducted to assess the two operational performance procedures. According to the results obtained from the physical and chemical analysis of the treated STWW, there was no significant differences in the pH and in the EC content of the bioaugmentation-phytoremediation treatment, while a significant increase of the EC content was observed in the bioaugmentation-adsorption to 5.08 mS cm−1. The COD value significantly decreased up to 1320 mg L−1 in bioaugmentation-adsorption treatment (control value 2400 mg L−1) and 98 mg L−1 in bioaugmentation-phytoremediation treatment (control value 98 mg L−1). Microbial biomass monitoring of P. putida shows significant greater in both processes in the order of 9.18 and 7.01 Log CFU mL−1 for bioaugmentation-adsorption and bioaugmentation-phytoremediation, respectively. The chlorophyll content in Typha angustifolia and Schoenoplectus acutus significantly decreased after 144 h with the exception of the chlorophyll a content of Schoenoplectus acutus in which the content increased up to 3.31 mg mL−1. Comparing the performance of these two treatments, it was found according to HPLC analysis that the bioaugmentation-adsorption process was more efficient in removing about 97% of PCP after 48 h, against around 90% of PCP after 72 h for the phytoremediation-bioaugmentation. The alfalfa seeds showed a germination rate after the 5th day of incubation of 100% and 95%, respectively for the PCP-non-contaminated and treated STWW, while for wastewater containing PCP the germination was totally inhibited.

Arthropod Assemblages in Invasive and Native Vegetation of Great Salt Lake Wetlands

Wetlands provide essential habitat for shorebirds, songbirds, and waterfowl. Invasive species can disrupt trophic interactions within wetlands by altering the arthropod assemblages on which birds rely. An invasive grass species, Phragmites australis (common reed), has invaded wetlands across North America, including those surrounding the Great Salt Lake, Utah, U.S.A. Phragmites outcompetes native vegetation and alters habitat for resident and migratory birds, yet how Phragmites affects arthropod assemblages is unclear. To address these knowledge gaps, this study investigated how arthropod assemblages differ between native and invasive vegetation in Great Salt Lake wetlands. We examined the arthropod assemblages found within three native habitats as well as in Phragmites-invaded areas. There were few differences in arthropod assemblages between Phragmites and two native habitats (hardstem bulrush, Schoenoplectus acutus and alkali bulrush, Bolboschoenus maritimus). Arthropod assemblages differed between Phragmites and the native Salicornia rubra (pickleweed), which differed markedly from the other plant species in structure, biomass, and related site conditions. Identifying how arthropods interact with Phragmites and native vegetation is critical to recognizing how to effectively manage wetlands for bird habitat. By gaining an understanding of these relationships, arthropod biomass, abundance, diversity, and assemblage composition could serve as assessment metrics for determining wetland management success.

Kinetics of nitrous oxide mass transfer from porewater into root aerenchyma of wetland plants.

The creation and/or restoration of wetlands is an important strategy for controlling the release of reactive nitrogen (N) via denitrification, but there can be tradeoffs between enhanced denitrification and the production of nitrous oxide (N2 O), a potent greenhouse gas. A knowledge gap in current understanding of belowground wetland N dynamics is the role of gas transfer through the root aerenchyma system of wetland plants as a shortcut emission pathway for N2 O in denitrifying wetland soils. This investigation evaluates the significance of mass transfer into gas-filled root aerenchyma for the N2 O budget in wetland mesocosms planted with Sagittaria latifolia Willd. and Schoenoplectus acutus (Muhl. ex Bigelow) Á. Löve & D. Löve. Dissolved gas tracer push-pull tests with N2 O and the nonreactive gas tracers helium, sulfur hexafluoride, and ethane were used to estimate first-order rate constants for gas transfer into roots and microbial N2 O reduction and thereby disentangle the effects of root-mediated gas transport from microbial metabolism on N2 O balances in saturated soils. Root-mediated gas transport was estimated to account for up to 37% of overall N2 O removal from the wetland soils. Rates of microbial N2 O reduction varied widely based on the organic matter content of the soil media and served as a key control on the fraction of N2 O that transferred into roots. This research identifies transport through root aerenchyma as a potential shortcut pathway for N2 O emission from wetland soils and sediments and indicates that this process should be considered in both measurements and mechanistic modeling of belowground wetland N dynamics.

Salinity and inundation effects on productivity of brackish tidal marsh plants in the San Francisco Bay-Delta Estuary

Plant productivity is central to numerous ecosystem functions in tidal wetlands. We examined how productivity of brackish marsh plants in northern California responded to abiotic stress gradients of inundation and salinity using two experimental approaches. In a greenhouse study with varying salinity, shoot production and biomass of Juncus balticus, Schoenoplectus acutus and S. americanus all declined monotonically with higher salinity, with evidence of differences in sensitivity among species by their varied functional responses. Salinity also negatively affected fecundity for the one species (S. americanus) that produced enough inflorescences during the experiment for analysis. In a field manipulation of inundation and initial pore water salinity, total end-of-season biomass and other metrics of growth in the high marsh species, J. balticus, had unimodal relationships with inundation. Root production tended to be greater strongly impacted by greater inundation than shoot production. The salinity treatment quickly dissipated for treatments that were flooded more frequently but persisted at a higher marsh elevation where it suppressed plant growth. These results suggest that both increased flooding and salinity associated with climate change and sea-level rise may negatively impact productivity of brackish marsh species, but with variable effects by species and stressor.

Vegetation vs. Anoxic Controls on Degradation of Plant Litter in a Restored Wetland

The ability of wetlands to accrete organic matter in response to rising sea-level is a key to landscape resilience, especially in light of reduced sediment availability consequent to dam construction and channelization. This study examined degradation of cattail (Typha spp) and tule (Schoenoplectus acutus) litters in restored wetlands through the lens of lignin, a major structural biopolymer in vascular plants with degradation characteristics very sensitive to oxic vs. anoxic conditions. A series of litterbags were deployed during the first 10 years after flooding of Deep (55 cm) and Shallow (25 cm) restored wetlands. As emergent marsh vegetation spread through the maturing wetlands, anoxic conditions were more prevalent and overall degradation rates of litter in litterbags were lower. In later experiments in the maturing wetlands, lignin was progressively enriched in litter as evidenced by carbon-normalized yields (8) that increased in tule starting materials from 6.3 to 7.1 mg 100mgOC-1 to as high as 9.9 mg 100mgOC-1, and in cattail starting materials from 5.9 to 7.0 mg 100mgOC-1 to as high as 10.9 mg 100mgOC-1. However, in an experiment initiated soon after the restored wetlands were constructed, 8 in tule litter decreased from 6.8 to 3.6 mg 100mgOC-1, highlighting the prevalence of initial oxic conditions. With the exception of the early oxic conditions for tule there was an overall trend of decreasing lignin acid-to-aldehyde ratios with litter degradation, which runs counter to most studies in the literature. We hypothesize that this reflects the utilization of more oxygen-rich lignin components as electron acceptors in redox reactions. No consistent differences were observed in degradation patterns between the Shallow and Deep wetlands. There were distinct differences in lignin degradation in cattail (more resistant) vs. tule (less resistant), which indicates that although anoxia may be the dominant control on organic matter accretion in wetlands, specific types of vegetation in restored or constructed wetlands affects organic matter preservation, and hence accretion. Thus, selective management of predominant species in wetlands may prove important for the ability of wetlands to maintain emergent vegetation during sea-level rise and to preserve the overall stability of wetland soils.

Ecosystem Functioning of Great Salt Lake Wetlands

Like many wetlands worldwide, Great Salt Lake (GSL) wetlands have been declining. Yet, little is known about the ecosystem functions provided by the different GSL wetland plant species. This knowledge gap hinders predictions of the effects of species loss and restoration practices on ecosystem functioning. To better understand how the loss of different habitat types affects the provisioning of ecosystem functions, we quantified eight functions and multifunctionality (the support of multiple functions simultaneously) across seven dominant GSL wetland habitat types. Habitats varied greatly in their capacity to perform functions. However, no single habitat type supported all eight functions even at 20% of the maximum value for each individual function. We found that native plants Typha latifolia and Schoenoplectus acutus and invasive Phragmites australis had the highest levels of multifunctionality. Although these three species were able to support more functions, we found that a diversity of habitats are required to maintain the breadth of ecosystem functions examined. This study supports the idea that habitat heterogeneity is critical in supporting a multifunctional environment, and that habitat homogenization may cause a reduction in functioning provided by GSL wetlands.

Patch scale evapotranspiration of wetland plant species by ground-based infrared thermometry

Accurate estimation of evapotranspiration (ET) is essential to calculate the wetland water balance. However, wetlands are often composed of patches of different species of vegetation, raising the question whether different species will have different ET rates. Standard field-based meteorological methods to estimate ET, e.g., Priestley-Taylor (P-T), are sensitive to changes in climate drivers of ET but not to spatial variations in vegetation. To investigate whether ET is sensitive to vegetation type, we used thermal infrared (TIR) temperature-based surface energy balance (SEB) and Bowen ratio (β) ET estimation methods in four wetlands in northern New York State. The four wetlands had different plant communities including hardstem bulrush (Scirpus acutus), reed canary grass (Phalaris arundinacea), cattail (Typha Spp.) and meadow willow (Salix petiolaris). Across all four sites, the TIR-based methods generally had similar results as P-T methods, with mean absolute difference (MAD) of 17.1–53.0 W m−2 and root mean squared difference (RMSD) of 23.4–62.4 W m−2 across sites. This suggests that ET was not strongly dependent on vegetation type and topography in these northern wetlands. However, different methods showed different sensitivities to atmospheric variables including wind speed and relative humidity, suggesting that under certain conditions TIR-based methods may better represent differences in ET from different vegetation architectures.

Direct analysis of naphthenic acids in constructed wetland samples by condensed phase membrane introduction mass spectrometry.

The application of direct mass spectrometry techniques to the analysis of complex samples has a number of advantages including reduced sample handling, higher sample throughput, in situ process monitoring, and the potential for adaptation to on-site analysis. We report the application of a semi-permeable capillary hollow fibre membrane probe (immersed directly into an aqueous sample) coupled to a triple quadrupole mass spectrometer by a continuously flowing methanol acceptor phase for the rapid analysis of naphthenic acids with unit mass resolution. The intensity of the naphthenic acid-associated peaks in the mass spectrum are normalized to an internal standard in the acceptor phase for quantitation and the relative abundance of the peaks in the mass spectrum are employed to monitor compositional changes in the naphthenic acid mixture using principle component analysis. We demonstrate the direct analysis of a synthetic oil sands process-affected water for classical naphthenic acids (CnH2n+zO2) as they are attenuated through constructed wetlands containing sedge (Carex aquatilis), cattail (Typha latifolia), or bulrush (Schoenoplectus acutus). Quantitative results for on-line membrane sampling compare favourably to those obtained by solid-phase extraction high-resolution mass spectrometry. Additionally, chemometric analysis of the mass spectra indicates a clear discrimination between naphthenic acid-influenced and natural background waters. Furthermore, the compositional changes within complex naphthenic acid mixtures track closely with the degree of attenuation. Overall, the technique is successful in following changes in both the concentration and composition of naphthenic acids from synthetic oil sands process-affected waters, with the potential for high throughput screening and environmental forensics.

The Role of Seed Bank and Germination Dynamics in the Restoration of a Tidal Freshwater Marsh in the Sacramento–San Joaquin Delta

Liberty Island, California, is a historical freshwater tidal wetland that was converted to agricultural fields in the early 1900s. Liberty Island functioned as farmland until an accidental levee break flooded the area in 1997, inadvertently restoring tidal marsh hydrology. Since then, wetland vegetation has naturally recolonized part of the site. We conducted a seed bank assay at the site and found that despite a lack of germination or seedling recruitment at the site, the seed bank contained a diverse plant community, indicating that the site’s continuous flooding was likely suppressing germination. Additionally, the frequency of germinating seeds in the seed bank did not represent the dominant adult plant community. We conducted a cold stratification study to determine if this observed disparity could be explained by seed germination dynamics, and whether germination could be enhanced using a pre-germination cold exposure, particularly for species of concern for wetland restoration. The cold stratification study showed that longer durations of pre-germination cold enhanced germination in Schoenoplectus acutus, but reduced germination in Schoenoplectus californicus, and had no effect on Typha latifolia. Overall, germination of S. californicus and S. acutus was much lower than T. latifolia. Our findings suggest that seeding may not be an effective restoration technique for Schoenoplectus spp., and, to improve restoration techniques, further study is needed to more comprehensively understand the reproduction ecology of important marsh species.

Experimental test of abiotic and biotic factors driving restoration success of Vallisneria americana in the Lower Bay of Green Bay

Abstract The eutrophication of aquatic habitats is a primary driver of ecosystem degradation, often culminating in a switch from a macrophyte-dominated clear water state to a phytoplankton-dominated turbid water state. While numerous studies have documented the ecological implications of this switch, subsequent reductions in nutrient and sediment loading do not consistently result in predictable reversals to macrophyte dominance. Re-introduction of rooted aquatic macrophytes at appropriate scales and species combinations may disrupt these negative feedbacks, although our current limited understanding of these complex mechanisms hinders the development of effective, targeted restoration strategies. We evaluated the potential for restoration of Vallisneria americana (wild celery) in the Lower Bay of Green Bay by altering restoration size and co-planting with the emergent species Schoenoplectus acutus (hardstem bulrush). Wild celery survival among all sites exceeded 90% in 2015 and 110% in 2016. However, in contrast to our expectations the effect of restoration size and interspecific facilitation on survival was either marginal or non-significant. Instead, various environmental effects focused largely on the interaction of water depth, substrate characteristics, and the abundance of unrestored floating macrophytes (i.e. Lemna, Ceratophyllum, and Utricularia spp.) drove variability in restoration success, suggesting that future work focus on identifying restoration methods that can withstand a highly dynamic environment. Our results provide insight into the factors continuing to limit the re-establishment of aquatic macrophytes in degraded systems, suggesting a more limited role of water quality and greater role of interspecific competition and propagule limitation or seedling establishment than previously recognized.

Fine‐scale genetic diversity and landscape‐scale genetic structuring in three foundational bulrush species: implications for wetland revegetation

The appropriate sourcing of seeds for restoration is critical for establishing foundational plant species that support ecosystem functions and services. Genetic analyses of such species can yield insights into patterns of genetic diversity and structuring to inform seed collections. Here we document, for three foundational bulrush species, distinct genetic patterns to guide restoration of wetlands along the iconic Great Salt Lake, the largest lake in western North America. Specifically, Schoenoplectus acutus and Schoenoplectus americanus had moderate levels of site‐scale genet richness and relatively low genet richness levels within 1‐m2 plots. These patterns contrast with Bolboschoenus maritimus, which had higher levels of site‐ and plot‐level genet richness, and has therefore likely experienced more recent seedling establishment. At the landscape scale, we found some evidence for genetic isolation of individuals at more remote sites (namely Fish Springs National Wildlife Refuge in the West Desert of Utah), but all species are relatively well dispersed over hundreds of kilometers, a pattern most likely to occur via avian dispersal. In our mechanistic dispersal assessment, we found abundant bulrush seeds present in waterfowl gizzards and those seeds germinated readily despite (or because of) partial digestion. Migratory waterfowl likely facilitate the broad dispersal of all species and may aid in bulrush establishment by breaking seed dormancy. These findings suggest that seeds for restoration should be collected within and among seed source sites to ensure a diverse restoration seed lot that does not disrupt gene flow patterns.

Late Pleistocene mammoth trackway from Fossil Lake, Oregon

Behavior of Columbian mammoths (Mammuthus columbi) is revealed by a newly discovered trackway at the Pleistocene locality of Fossil Lake, Oregon. Our 8 by 20 m excavation of the mammoth trackway found 117 tracks, including one 20-m-long adult trail, partial trackways of 3 additional adults, a yearling and a baby all heading generally west. The tracks are in the Marble Bluff biotite tuff (43.2 cal ka), which forms a surface horizon to the Pogani silty clay loam paleosol (Natrargid), with a cracked surface and a columnar-structured, subsurface (Bn) horizon, like soils under desert soda pans with alkali shrubland. Directly below is the Yada silty clay paleosol (Xeroll) with crumb textured surface (A) horizon like grassland soils. The Pasiwa loam (Psamment) is a thin brown siltstone, with sparse roots and burrows of lake-margin early successional vegetation. The Pui sandy loam (Aquent) is well-bedded tuff and sand (A) with subhorizontal calcareous rhizomes and adventitious roots, like those of lake-margin tule reeds (Schoenoplectus acutus). Columbian mammoths may have moved like modern elephants with infants in matriarchal groups through landscapes of sagebrush and grassland, and this trackway includes a limping female attended by concerned juveniles. Grassland paleosols common in the Fossil Lake Formation, are now rare in the same region, perhaps related to extinction of proboscidean and equine grazers.

Impact of nitrogen and importance of silicon on mechanical stem strength in Schoenoplectus acutus and Schoenoplectus californicus: applications for restoration

Nitrogen (N) and Silicon (Si) availability can affect the vigor and resiliency of plant communities. The effects of N on plant growth has been investigated in multiple species and is understood to promote growth. Though it is generally understood that Si aids in plant functions such as stem strength enhancement and herbivory defense, the role Si has not been explored in many wetland plant species. Tidal wetland plants are often subjected to high wind and wave energy, which can cause breakage or collapse of stems. This body of research investigated the combined effects of Si and N regimes to reduce the occurrence of stem collapse through its influence on stem strength. We investigated the effects of Si and N concentration on the growth, morphology, and physiology of Schoenoplectus acutus and Schoenoplectus californicus, two species of macrophytes that are commonly used in freshwater tidal restoration plantings. Individuals of each species were grown hydroponically in four different nutrient combinations (low Si and low N, low Si and high N, high Si and low N, and high Si and high N). Results indicated that increased N concentrations promoted aboveground biomass production, whereas increased Si concentration enhanced stem strength and decreased the likelihood of stem collapse and herbivory. Plants receiving a high Si and low N nutrient combination exhibited the most robust stems. Our findings emphasize the importance of Si, as well as N, in Schoenoplectus spp. growth and highlight the potential applications for these nutrients in enhancing tidal marsh management.

Water depth and lake-wide water level fluctuation influence on α- and β-diversity of coastal wetland fish communities

Abstract Coastal wetlands in the Laurentian Great Lakes are critical habitats for supporting fish diversity and abundance within the basin. Insight into the coupling of biodiversity patterns with habitat conditions may elucidate mechanisms shaping diverse communities. Within coastal wetlands, water depth as well as fluctuations in lake-wide water levels over inter-annual timescales, both have the potential to influence fish communities. Water level fluctuation can influence fish habitat structure (e.g., vegetation) in Great Lakes coastal wetlands, but it is unclear how water depth and lake-wide water level fluctuations affect fish community composition and diversity. Using β dissimilarity indices and multivariate ordination techniques, we assessed fish community structure among bulrush (Schoenoplectus acutus)-dominated wetlands in Saginaw Bay, Lake Huron, USA. We examined whether community structure was related to wetland water depth at the time of sampling and whether fish communities were more similar among years with similar Lake Huron water levels. Results suggested relatively high levels of both spatial (among wetlands) and temporal (among year) community dissimilarity that was driven primarily by species turnover. Thus, variability in water depths among wetlands and in Lake Huron water levels among years likely both contribute to regional fish diversity. Further, fish abundance and alpha diversity were positively correlated with wetland water depth at the time of sampling. Both climate change and anthropogenic water level stabilization may alter the magnitude and timing of water level fluctuations in the Great Lakes. Our data suggest that these changes could affect local fish community composition and regional fish diversity.

Model parameters for representative wetland plant functional groups

AbstractWetlands provide a wide variety of ecosystem services including water quality remediation, biodiversity refugia, groundwater recharge, and floodwater storage. Realistic estimation of ecosystem service benefits associated with wetlands requires reasonable simulation of the hydrology of each site and realistic simulation of the upland and wetland plant growth cycles. Objectives of this study were to quantify leaf area index (LAI), light extinction coefficient (k), and plant nitrogen (N), phosphorus (P), and potassium (K) concentrations in natural stands of representative plant species for some major plant functional groups in the United States. Functional groups in this study were based on these parameters and plant growth types to enable process‐based modeling. We collected data at four locations representing some of the main wetland regions of the United States. At each site, we collected on‐the‐ground measurements of fraction of light intercepted, LAI, and dry matter within the 2013–2015 growing seasons. Maximum LAI and k variables showed noticeable variations among sites and years, while overall averages and functional group averages give useful estimates for multisite simulation modeling. Variation within each species gives an indication of what can be expected in such natural ecosystems. For P and K, the concentrations from highest to lowest were spikerush (Eleocharis macrostachya), reed canary grass (Phalaris arundinacea), smartweed (Polygonum spp.), cattail (Typha spp.), and hardstem bulrush (Schoenoplectus acutus). Spikerush had the highest N concentration, followed by smartweed, bulrush, reed canary grass, and then cattail. These parameters will be useful for the actual wetland species measured and for the wetland plant functional groups they represent. These parameters and the associated process‐based models offer promise as valuable tools for evaluating environmental benefits of wetlands and for evaluating impacts of various agronomic practices in adjacent areas as they affect wetlands.

Seed Dormancy Break and Germination for Restoration of Three Globally Important Wetland Bulrushes

Limited knowledge of seed dormancy break, germination requirements, and intraspecific variation of these traits hinders revegetation of many species targeted for restoration. We evaluated the importance of cold stratification and chemical scarification for breaking seed dormancy and the impact of soaking in water on germination for three globally distributed bulrush species. These species, Bolboschoenus maritimus (alkali bulrush), Schoenoplectus acutus (hardstem bulrush), and S. americanus (threesquare bulrush), form critical habitat in Great Salt Lake wetlands. For B. maritimus and S. acutus , we also evaluated variation in response to seed dormancy breaking treatments among geographically-distant seed sources. We found that both 180 days of cold, moist stratification or 48 hours of bleach scarification were effective for breaking seed dormancy for most seed sources of B. maritimus . For S. acutus , longer stratification lengths may result in consistently higher germination percentages, but 30 days of stratification may be of sufficient length for some source sites. For S. americanus , stratification improved germination in one experiment, but 20–60 percent of viable seed did not germinate in each experiment potentially due to a poor understanding of germination requirements. Soaking seeds in water under greenhouse conditions, improved the germination of all species when done after dormancy breaking treatments. Importantly, response to dormancy breaking treatment varied among source sites; intraspecific variation may account for unpredictable responses to dormancy breaking treatments. These findings can assist practitioners in crafting strategies to effectively break dormancy and germinate seeds of B. maritimus, S. acutus , and S. americanus .

Can community structure track sea-level rise? Stress and competitive controls in tidal wetlands.

Climate change impacts, such as accelerated sea‐level rise, will affect stress gradients, yet impacts on competition/stress tolerance trade‐offs and shifts in distributions are unclear. Ecosystems with strong stress gradients, such as estuaries, allow for space‐for‐time substitutions of stress factors and can give insight into future climate‐related shifts in both resource and nonresource stresses. We tested the stress gradient hypothesis and examined the effect of increased inundation stress and biotic interactions on growth and survival of two congeneric wetland sedges, Schoenoplectus acutus and Schoenoplectus americanus. We simulated sea‐level rise across existing marsh elevations and those not currently found to reflect potential future sea‐level rise conditions in two tidal wetlands differing in salinity. Plants were grown individually and together at five tidal elevations, the lowest simulating an 80‐cm increase in sea level, and harvested to assess differences in biomass after one growing season. Inundation time, salinity, sulfides, and redox potential were measured concurrently. As predicted, increasing inundation reduced biomass of the species commonly found at higher marsh elevations, with little effect on the species found along channel margins. The presence of neighbors reduced total biomass of both species, particularly at the highest elevation; facilitation did not occur at any elevation. Contrary to predictions, we documented the competitive superiority of the stress tolerator under increased inundation, which was not predicted by the stress gradient hypothesis. Multifactor manipulation experiments addressing plant response to accelerated climate change are integral to creating a more realistic, valuable, and needed assessment of potential ecosystem response. Our results point to the important and unpredicted synergies between physical stressors, which are predicted to increase in intensity with climate change, and competitive forces on biomass as stresses increase.