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Seed-based revegetation is increasingly pursued in wetland restoration, but seed and seedling mortality is high and can be further limited by environmental stressors, like hydrology and salinity. The interactive effects of hydrology and salinity on native plants, especially in the presence of invasive plants, are less clear. In greenhouse and mesocosm experiments, we tested different hydrologic and salinity conditions on the growth of native seed mixes and Phragmites australis, a widespread wetland invader in North America. The greenhouse experiment tested two mixes (forb mix, graminoid mix), while mixes in the mesocosm experiment combined forbs and graminoids chosen for broad and diverging environmental tolerances. In both experiments, reduced water negatively affected native plants and P. australis, while increased salinities reduced native plant growth but had minimal impacts on P. australis. In the greenhouse experiment, forbs greatly reduced P. australis growth only under benign conditions but maintained growth under increasing abiotic stress despite the presence of P. australis. In the mesocosm experiment, native plants reduced P. australis growth across all conditions, indicating that mixes chosen for broad environmental tolerances can sufficiently reduce invasive growth even when negatively affected by abiotic stressors. Our results demonstrate the varying drivers of invasion resistance: sometimes environmental conditions and species’ tolerances limit invasives and other times, the composition and competitive potential of the native community is more important. These results also inform wetland restoration practices, i.e., choosing species for revegetation mixes with broad environmental tolerances and, when possible, manipulating wetland environmental conditions to reduce invader performance. [ABSTRACT FROM AUTHOR]

The accelerated eutrophication rate of (sub)tropical lakes is a major environmental problem. Constructed wetlands are considered as an effective method to purify water bodies. However, the removal rate of nitrogen (N), phosphorus (P) and other nutrients by wetland vegetation is quite different, and the continuous observation of plants and water ecosystems is required. In this study, the growth curves of two subtropical wetland plants, Phragmites australis and Zizania caduciflora, and their absorption effects on N and P in constructed wetlands were studied. The results showed that the growth curves of the two wetland plants were similar, reaching the biomass peak in July to August, and the cumulative absorption of N and P by plants had the same trend with the change of biomass. The N and P concentration of plants reached the peak in March to April, with higher concentration in Phragmites australis than that of Zizania caduciflora. At the end of the growing season, i.e. around October 20, the accumulated absorption of N and P by plants reached the maximum, which was the optimal time for harvest of subtropical wetland plants. Thereafter, the residues of plant litter entered the water, causing the recovery of N and P concentration in the water body, therefore affected the purification function of wetland. There is a strong correlation between the water purification efficiency and plant growth. With the increase of biomass, N and P accumulation in Phragmites australis and Zizania caduciflora, the N, P content and chemical oxygen demand (COD) in the water of wetland showed a significant decreasing trend. The removal rates of N, P, COD and suspended substance (SS) in the constructed wetlands with Phragmites australis and Zizania caduciflora as the main plants were 95%, 96%, 82% and 86%, respectively. In general, the purification capacity of Phragmites australis is slightly higher than that of Zizania caduciflora and precipitation had positive effects on the pollutants concentration of wetland water. The results provide scientific basis for plant selection and management of subtropical constructed wetlands. [ABSTRACT FROM AUTHOR]

It is increasingly clear that hydrology, vegetation, and soil characteristics are important in controlling methane (CH4) emissions from wetlands. However, few studies have examined CH4 emissions between wetland habitats dominated by different plants, or between naturally occurring and restorred wetlands, which are hoped to offer a means of sequestering carbon (C) and offsetting greenhouse gas emission. Our goal was to assess the variation of CH4 fluxes between different habitats in natural and restored tidal freshwater wetlands. One natural site with three habitats (low marsh, high marsh, and swamp habitat) and restored site with two habitats (low and high marsh) were selected. Both sites are tidal freshwater wetlands (measured salinity <0.3 Practical Salinity Units (PSU)) located on the Patuxent River, Maryland, USA. Gas flux was quantified using static chambers once a month during day and night from May to August 2016 during a single growing season. At 12.5 and 40 cm soil depth, soil redox potential, temperature, porewater CH4, and total iron (Fe) concentrations were measured on the same days as flux. Restored habitats had significantly higher soil redox potential (i.e., less reducing conditions) than their natural counterparts (P < 0.05). Methane flux had high spatiotemporal variations across natural and restored wetland habitats (ranged from −87,901 mg CH4 m−2 day−1 in restored high marsh during June to 6860 mg CH4 m−2 day−1 in natural swamp habitat during May). Moreover, natural wetland habitats, on average, were significantly warmer (P < 0.05) than their restored counterparts at both soil depths (12.5 and 40 cm), where porewater CH4 concentrations had positive and significant correlation with wetland soil temperatures (r = 0.36 and P < 0.001 – the warmer the soil, the higher the porewater CH4 available). For a more precise global C budget, soil temperature, spatiotemporal CH4 variations between wetland types, and tidal effects should be considered in accounting for CH4 fluxes in wetlands in general and tidal freshwater wetlands specifically. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Denitrification removes reactive nitrogen (N) from ecosystems by transforming nitrate (NO3−) to dinitrogen (N2) gas. Incomplete denitrification produces nitrous oxide (N2O), a potent greenhouse gas. In salt marshes, denitrification, N2O production, and N2O yield (the fraction of denitrification that produces N2O) have implications for N load reduction and greenhouse gas emissions. We collected soil cores from three salt marsh zones (low marsh, high marsh, and invasive Phragmites australis) on five sampling dates that spanned the growing season (May through October) to quantify seasonal patterns of potential denitrification, N2O production, and N2O yield. Potential denitrification peaked at the beginning and end of the growing season, with rates several times higher in May and October than in June, but we found no significant differences among salt marsh zones. In contrast, seasonal patterns of potential N2O production depended on marsh zone; N2O production was aseasonal in high marsh and P. australis zones, but in the low marsh, N2O production was lower in July compared to all other months sampled. In this salt marsh, seasonal variation of potential denitrification and N2O production was greater than spatial variation over the marsh zones, highlighting the importance of understanding temporal patterns of salt marsh N cycling. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Die-back of Phragmites australis in the Mississippi River Delta (MRD), Louisiana, USA, is associated with large populations of nonnative Roseau Cane Scale (RCS), Nipponaclerda biwakoensis. Initial observations suggested different P. australis phenotypes displayed different susceptibilities to scale infestation and die-back, but the role of scale infestation on die-back was unknown. To understand the effect of RCS on P. australis, paired stands of Delta and European phenotypes in the MRD were monitored for stem heights, densities, and scale infestation over two years. A mesocosm experiment was conducted to assess whether RCS abundance and P. australis growth were dependent on water salinity and phenotype. Three Phragmites australis phenotypes were grown in small pools under fresh or mesohaline conditions, and RCS infestated or non-infested treatments. Scale densities were up to 7 times greater on the Delta compared to the European phenotype. Scale infestation resulted in 22%–39% reductions in the proportion of stems with green leaf tissue for all phenotypes, and 12% reduction in stem heights for Delta-type. Salinity was detrimental to all phenotypes, reducing stem heights by 20% compared to freshwater. Our results provide evidence that the RCS can result in die-back symptoms similar to what is observed in the MRD. [ABSTRACT FROM AUTHOR]

Habitat destruction caused by human activities is threatening wetland plants. Based on Landsat 5 TM, Landsat 8 OLI, and Google Earth images, we analysed the spatiotemporal dynamics of plant populations in a degraded wetland in the Minjiang River Estuary from 2009 to 2019. Field survey records, tasselled cap transformation, and supervised classification were used for the image interpretation. The results indicate that the plant habitat area decreased by 42.1% over these 10 years. Consequently, the distribution area of each dominant species declined, and the proportion of total vegetated area in the habitat decreased from 53.1% to 32.6%. Moreover, the dominance relations of the species changed from Spartina alterniflora > Phragmites australis > Cyperus malaccensis > Scirpus triqueter to P. australis > S. alterniflora > C. malaccensis > S. triqueter. We predict that the vegetation landscape in the wetland will be composed exclusively of P. australis and S. alterniflora if habitat destruction continues. Finally, our research shows that the NPCS (net plant carbon sequestration) and PCS (plant carbon stock) in the wetland and the average values of methane flux, NPCS, PCS, and SOCS (sediment organic carbon stock) in the vegetated area have all decreased due to plant population declines. [ABSTRACT FROM AUTHOR]

In a large-scale field experiment in 18 basins in a three-year old constructed wetland (6 ha) in the Netherlands, we analyzed a wide range of environmental variables, grouped into variable groups, to determine the combined direct effect of the environmental variables and the resulting decomposer community on decomposition rates of standing litter biomass in newly constructed wetlands. The variability among the experimental units could only to a limited degree be explained by linear combinations of all 54 possible predictor variables (30 and 23% of variation explained after 6 and 12 months of decomposition). Moreover, models for decomposition after 6 months could not predict decomposition after 12 months. The poor predictions by our models are probably due to (sometimes large) variations in the predictor variables but small differences in decomposition rates between the different basins. Based on our results it seems that decomposition of standing litter biomass in newly constructed wetlands is relatively uniform when considered in time and space, with low explanatory power by variable groups from biotic and abiotic variables. Normally one would expect differences in decomposition rates with differing environments, but counterintuitively in newly constructed wetlands these differences are small. [ABSTRACT FROM AUTHOR]

The relative importance of sexual vs. asexual propagules in wetland plant invasions is poorly understood, particularly for their importance in increasingly disturbed, resource-rich environments. Using the invasive wetland grass Phragmites australis as a model, we evaluated the resource needs of its seeds and rhizome fragments. In a greenhouse experiment where we manipulated nitrogen and propagule type, we found that Phragmites seedlings, but not rhizome fragments, responded positively to nutrient enrichment. In a second experiment, where we focused on seedling resource needs and manipulated light, nitrogen, and seed source, we found that seedlings were inhibited by heavy shade with no additional benefit of nutrient additions. Different seed sources (wetlands surrounded by different dominant land-use types, a proxy for disturbance) had variable leaf production and stem height (biomass did not vary). Understanding the mechanisms of Phragmites recruitment via seeds and rhizomes is critical for informing how a clonal species—now understood to disperse largely by seeds—can invade increasingly disturbed, resource-rich habitats. Our study suggests that Phragmites invasion by seed is being fueled, in part, by the positive effects of increased nutrients and light on Phragmites seedling performance and potentially by varying performance of seedlings derived from different watersheds. [ABSTRACT FROM AUTHOR]

The Medouie Creek wetland complex on Nantucket Island, MA was historically one contiguous salt marsh. Diking in the 1930s caused tidal restriction, creating a freshwater wetland colonized by Phragmites australis. To restore salt marsh habitat, the tidal restriction was removed and tidal salt water hydrology reestablished. Soil pore water salinity increased rapidly through the site with the majority of the marsh exhibiting salt marsh hydrology and higher salinities (25-30 ppt) eight years post-restoration. Extensive dieback of freshwater vegetation facilitated fairly rapid colonization by salt marsh vegetation, particularly adjacent to the culvert and marsh ditches. A non-metric multidimensional scaling (nMDS) analysis demonstrated that vegetation community composition was driven primarily by soil pore water salinity and marsh surface elevation. Eight years post-restoration, areas under 4 m elevation were dominated by salt marsh species while areas over 4 m retained freshwater vegetation. Unlike some other salt marsh restoration projects, salt marsh vegetation communities successfully established at Medouie primarily due to hydrological alteration and without the need for active revegetation or other restoration methods. P. australis stands were also significantly decreased. Given appropriate marsh conditions, altering hydrology alone to mimic functioning salt marsh hydrology may effectively drive vegetation succession and lead to ecologically functional salt marshes. [ABSTRACT FROM AUTHOR]

Invasions by exotic plant species like Phragmites australis can affect wetlands and the services they provide, including denitrification. Native and exotic Phragmites strains were genetically verified in 2002 but few studies have compared their ecosystem effects. We compared relationships between native and exotic Phragmites and environmental attributes, soil nutrient concentrations, and abundance and activity of soil denitrifying bacteria. There were no significant differences for any measured variables between sites with exotic and native strains. However, there were significant positive correlations between native Phragmites stem density and soil nutrient concentrations and denitrification rates. Furthermore, denitrifying bacterial abundance was positively correlated with nitrate concentration and denitrification rates. Additionally, there were significant negative correlations between water levels in native Phragmites sites and native stem density, nutrient concentrations, and denitrification rates. Surprisingly, we found no significant relationships between exotic stem density or water level and measured variables. These results suggest 1) the native strain may have important ecosystem effects that had only been documented for exotic Phragmites, and 2) abiotic drivers such as water level may have mediated this outcome. Further work is needed to determine if the stem density gradients were a consequence, rather than a cause, of pre-existing gradients of abiotic factors. [ABSTRACT FROM AUTHOR]

Phragmites australis (common reed) is a widespread perennial grass of wetland habitats, with cryptic native and introduced subspecies in North America. We determined the relative abundance of the subspecies and the distributions of plastid DNA haplotypes throughout British Columbia, Canada, at the northwestern distribution limit of common reed in North America. Of 203 specimens assigned to subspecies using molecular markers, we identified only 9 plants as the introduced ssp. australis; all remaining samples were the native ssp. americanus. The two subspecies co-occurred at only one locality. We identified four native haplotypes (one widespread in British Columbia and three others more localized) and two introduced haplotypes. Using plants of known haplotype, we assessed the utility of different morphological traits and trait combinations for distinguishing native and introduced subspecies in this geographic region. No single morphological trait was diagnostic, but principal components analysis and identification indices based on combinations of traits consistently separated the native and introduced subspecies in our sample. Two- or three-trait combinations of ligule length, lemma length and stem anthocyanic coloration gave the best separation. These indices could reduce the need for confirmation of the introduced subspecies using molecular tools, facilitating efforts to monitor and control this invasive plant. [ABSTRACT FROM AUTHOR]

The surface waters of Tianjin municipality exhibit severe nitrogen loading and salinization; however, the extent to which the current levels of nitrogen enrichment and salinization have impacted belowground biomass and root morphology in reed marshes is poorly documented. This study was conducted at typical saline reed marshes (Dahuangpu, Qilihai, and Beidagang) in the Tianjin municipality. The relationships between belowground biomass, belowground-aboveground biomass (B-A) ratio, root morphology and the varying sediment nitrogen and salinity levels were investigated. Results showed: 1) Higher salinity levels related to a substantial decrease in the belowground biomass, B-A ratio, and root length density; 2) Higher nitrogen stress levels related to decreased belowground biomass, specific root length and root length density, and B-A ratio at Qilihai site with the highest nitrogen loading; 3) specific root length, root length density, and B-A ratio were significantly correlated to the aboveground plant nitrogen concentration; and 4) neither salinity nor nitrogen stress significantly altered aboveground biomass. The results show that aboveground biomass invariance masks significant belowground productivity changes in response to salinization and nitrogen loading in Reed Marshes. Impact of salinization and nitrogen loading on belowground productivity in wetlands should be considered to fine-tune critical carbon-dependent components of global change models. [ABSTRACT FROM AUTHOR]

The introduced grass Phragmites australis (hereafter Phragmites) is one of the most widespread invasive plants in North American wetlands. Phragmites has been extensively studied in some regions of North America, such as the Chesapeake Bay and the Great Lakes. However, little research has evaluated the extent of Phragmites invasion in the Intermountain West and the environmental drivers that have promoted its spread, particularly in the critically important Great Salt Lake (GSL) wetlands. Here we use high-resolution multispectral imagery to map the current distribution of Phragmites around GSL. We then identify factors associated with Phragmites presence in GSL using a species distribution model using the Random Forest algorithm. We contrast these findings with what is known about Phragmites invasion in other regions. We estimate that Phragmites occupies over 93 km around GSL. Phragmites was more likely to be found in wetland areas close to point sources of pollution, at lower elevations with prolonged inundation, and with moderate salinities. Results from our study will assist wetlands managers in prioritizing areas for Phragmites monitoring and control by identifying likely areas of prime Phragmites habitat. [ABSTRACT FROM AUTHOR]

The relationships between vegetation communities and environmental variables in tropical/subtropical tidal freshwater wetlands are poorly understood. We tracked the vegetation succession of the Huajiang wetland in northern Taiwan for 10 years since its emergence in 2000, likely due to massive sediment deposition caused by typhoon floods. The aquatic plant Phragmites australis expanded and dominated the wetland within the first four years, after which terrestrial herbaceous plants appeared. In 2007, woody plants were found scattered in the wetland. In 2010, the vegetation communities became more diverse. Along the gradient of increasing elevation with decreasing soil water content, three vegetation zones were distinguished: aquatic, terrestrial, and transitional. Along the second gradient of distances from the nearest tidal creek, the transitional zone could be further differentiated into more aquatic and more terrestrial zones. Our results indicate that hydrology engaging soil moisture and sedimentation was the major force driving the vegetation succession in the tidal freshwater wetland. These findings suggest that the vegetation community in tidal freshwater wetlands can be used as an indicator to monitor management measures and assess the impacts within the wetland and catchment. [ABSTRACT FROM AUTHOR]

Plant invasion and increased flooding intensity projected by climate change models can change the soil capacity of marine wetland to store P. This is a key question to the nutrient balances and eutrophication processes of coastal areas, especially in China coastal area that is receiving the freshwaters of a country in fast economical developing process. We studied the impact of changes in flooding intensity and plant invasion on total soil-P concentrations in the Minjiang River estuarine wetland. Flooding had a weak positive effect on soil P-fractions concentrations, but this effect was largely counteracted by the negative effect of salinity. Soil clay concentration and pH, both of which were related more with species community composition than with flooding intensity, were directly related to the P-fraction concentrations. The replacement of the native mangrove community by the invasive plant Phragmites australis was related to a decrease in the soil capacity to store P. A suitable management to maintain this wetland area in optimum conditions to act as a natural eutrophication buffer should tend to favor mangrove communities in the new areas that reach more than 220 days y of flooding, and a combination of the three tall-grasses communities below this level of flooding. [ABSTRACT FROM AUTHOR]

Invasions are dynamic as both the invading organism and the invaded ecosystem change. Intrinsic changes to the invader (invasion process) can involve population level genetic and reproductive changes. Extrinsic changes (invasion effect) occur to the environment that is invaded (e.g. , alterations to the physical environment), to the invaded plant community (e.g. , changes in species diversity and composition or evolutionary changes), or to insect herbivory. To investigate how invasions change through time, we investigated both the process and effect of a Phragmites australis invasion by comparing young and old P. australis stands within two Chesapeake Bay subestuaries. We quantified clonal richness of P. australis stands, vigor of the invader, herbivore damage, and plant community composition. Our results indicate that only the population-scale genetics (clonal richness, genetic distance) changed over the course of 40 years. Clonal richness was lower in the old P. australis stands, likely due to intraspecific competition and/or initial colonization by fewer genotypes. The mean genetic distance among clones within old stands was lower than within young stands, suggesting that clones within old stands were mostly closely-related, while young stands were likely established by seeds from nearby stands and so were more representative of the local area. Clones in different old stands were genetically more distant from each other than those in young stands were from clones in other young stands. This pattern suggested that old stands were established by independent colonization events, while young patches were established by a mixture of seeds from local stands, which generated the lower average genetic distance between clones across young stands. We found that community composition, plant vigor, and herbivore damage to stems were similar across different age stands, which indicated that the effect of P. australis invasion becomes stable within a few decades. Over longer periods, the intrinsic invasion process may be more dynamic than the invasion effect. [ABSTRACT FROM AUTHOR]

Respiration in tidal marshes plays an important role in the global carbon cycle, but is little investigated in Asia. In this study, ecosystem respiration in three brackish marshes dominated by Spartina alterniflora (smooth cordgrass), Phragmites australis (common reed) and Cyperus malaccensis (shichito matgrass) were examined monthly during 2009 in the subtropical tidal wetland of the Min River estuary of southeast China. Measurements were taken before and after tidal inundation. Soil porewater CO concentrations at soil depths of 5 and 10 cm were also measured. Differences in ecosystem respiration before and after tidal inundation stages were statistically indistinguishable in each vegetation type on an annual scale but differed by month. Monthly variation in ecosystem respiration was apparent and overall respiration in P. australis stand had the highest respiration of the vegetation types. Monthly average CO concentration in soil porewater did not differ significantly between the two depths. Ecosystem respiration in P. australis and C. malaccensis stands had a significant positive correlation with soil and air temperature, and a significant negative correlation with soil pH in S. alterniflora and C. malaccensis stands. Our results suggested that the brackish marsh ecosystem of subtropical estuary emits CO to the atmosphere at relatively higher level, but the emission pattern did not differ before and after tides. [ABSTRACT FROM AUTHOR]

Invasive plants in restored habitats can alter the system such that restoration goals are not met. Non-native lineages of Phragmites australis (hereafter Phragmites) are invasive in North American wetlands, and their presence can be problematic because of decreased species diversity and altered physicochemical processes. Phragmites is a challenging species for restoration because both native and non-native lineages can co-occur. We documented Phragmites expansion in a brackish marsh in Louisiana, USA that was restored with dredged sediments. Invasive Phragmites clones were inadvertently planted at the site. Phragmites expansion was documented through field measurements and aerial imagery. No growth differences were apparent between lineages during the first growing season. Horizontal expansion of 2.27 ± 0.15 m (mean ± 1SE) 5 months after planting occurred through rhizome growth. Seven years after planting, three patches with a combined aerial cover of about 0.7 ha were delineated. The study verified that Phragmites can grow relatively rapidly and persist on dredged sediments. Long-term rapid growth of invasive Phragmites may be a positive attribute in areas subject to high erosion and subsidence rates, despite reductions in species diversity. Acceptability of the presence of invasive Phragmites will depend on restoration goals. [ABSTRACT FROM AUTHOR]

Insectivorous birds can provide important ecosystem services, including regulating insect populations. The function of insectivorous birds in wetland ecosystems, such as tidal marshes, however, remains largely unexplored. Most studies of top-down interactions between insectivorous birds and herbivorous insects focus on insects in exposed-feeding guilds, but rarely on those in concealed-feeding guilds. In a reed-dominated estuarine tidal marsh, we examined the impacts of insectivorous birds on three groups of insect herbivores with concealed-feeding habits, including scale insects, gall-forming fly larvae, and stem-boring caterpillars. Insectivorous birds attacked 14.0-75.8% of reed shoots infested with scale insects, 13.3-20.7% with gall-forming fly larvae, and 8.0-100.0% with stem-boring caterpillars. Bird predation also significantly changed the abundance of herbivores, reducing scale insects by 36.7-85.9%, gall-forming fly larvae by 33.3-46.0%, and stem-boring caterpillars by 77.0-100.0%. Scale insects and stem-boring caterpillars suffered bird predation during different periods of the growing season. Our study demonstrated significant impacts of bird predation on concealed-feeding insects in a reed-dominant tidal marsh, highlighting the role of insectivorous birds in vegetated wetland ecosystems. [ABSTRACT FROM AUTHOR]

Wetlands in the Mesopotamian Plain in southern Iraq were extensively drained in the 1990s. Re-flooding of drained areas commenced in 2003, and included parts of the Central marsh between the Euphrates and Tigris Rivers. New vegetation in the re-flooded areas of the Central marsh was studied in 2006. Most of the wetland plant species and communities widely distributed prior to drainage have reappeared, but there were some species and communities that did not re-establish. Aboveground plant biomass is recovering in some communities, but in most of the new communities, biomass and diversity were low. Post-flooding sites were characterized by higher concentrations of chloride and bicarbonates in surface water and higher percent organic matter in sediment than those prior to drainage. Comparisons among the three study sites in the re-flooded areas and those between pre-drainage and post-flooding sites suggests that differences in water quality, including more saline conditions in the re-flooded wetlands, might be hindering the biomass recovery. The water source being limited to only the Euphrates River, a much more subdued seasonal fluctuation in the quantity of water input and output, and inputs of contaminated waters appear to be responsible for the delay in vegetation recovery in the Central marsh. [ABSTRACT FROM AUTHOR]

The reduction of nutrients and sediments from agricultural runoff by natural wetlands has been commonly accepted, but their role in water quality improvement at the catchment scale has been seldom studied, especially in irrigated catchments. This study aims to elucidate the effect of natural and recently created wetlands on stream water quality after the conversion of a catchment for irrigation purposes. Water quality and morphometrical and vegetation-related variables were measured in 19 wetlands on a 750-ha agricultural catchment under semi-arid conditions in the Ebro basin (NE Spain). A pollution gradient was found, increasing from the wetlands located in the upper catchment to those in the lower catchment. Wetlands with the lowest degree of artificiality, measured as the amount of human created structures (e.g., channel excavation, dikes), and higher plant richness had the poorest water quality, probably because they were in the lower catchment and their water contained more pollutants carried from agricultural and saline soils upstream. Some of these wetlands also had the highest rates of sediment and N-NO3 retention, in contrast to more artificial wetlands, which exported nutrients and sediments. Less artificial wetlands could also provide ancillary benefits such as biodiversity enhancement or landscape heterogeneity improvement. [ABSTRACT FROM AUTHOR]

We assessed short-term temporal and spatial variation of metal contents in the upper 100 cm sediment profile of intertidal marshes vegetated by common reed (Phragmites australis) along the Scheldt estuary in Belgium. The upper 0-100 cm sediment profile was sampled in three reedbeds at 56, 94, and 131 km from the river mouth. Sampling was repeated five times, at approximately two month intervals. Sediment properties such as texture and chloride, carbonate and organic matter content differed among locations. Metal accumulation, which is primarily due to association of metals with organic matter and clay in the surface sediment layer, seemed to be supplemented by an accumulation of sulphide precipitates deeper in the sediments. The depth at which sulphide precipitation significantly contributed to metal accumulation depended on the sampling location, and varied from less than 5 cm in clayey, organic sediments to more than 1 m in sandy sediments. Temporal variation of Cu, Cd, Pb, and Zn concentrations could only be linked to newly formed sulphides or sulphide oxidation at the sites with the lowest sulphide content. At sampling sites containing high sulphide amounts, variations should be primarily attributed to metal exchange and the presence of mobile metal complexes. Litter decomposition at the end of the growing season could hereby play a significant role. [ABSTRACT FROM AUTHOR]

The objective of this research was to compare and contrast C dynamics within plots occupied by Phragmites australis, Typha spp., and Sagittaria latifolia in a Lake Erie coastal wetland (Ohio, USA). The effect of each species on above- and below-ground biomass, soil C pools, soil labile C, litter decomposition rates, and microbial catabolic response profiles were analyzed. Phragmites australis and Typha spp. produced significantly more aboveground biomass (1,522 ± 464 and 1,177 ± 164 g DM m-2, respectively) than S. latifolia (500 ± 80 g DM m-2), although no difference was observed in terms of below-ground biomass. After 208 days in the field, litter of S. latifolia had lost 72% of its initial mass while only 47% of the litter of Typha spp. and P. australis had decomposed. This coupled process of high primary production and slow litter decomposition within P. australis and Typha spp. communities did not translate into greater accumulation of C in the soil. In fact, we observed lower rates of C mineralization and greater biomass of methanogens in the S. latifolia plots. Despite similar water level, soil conditions in the S. latifolia community was more saturated, which might have limited availability of C for microbial consumption in these plots. Microbial catabolic responses to 24 substrates demonstrated distinct differences in the respiration responses of the soil microbial communities of the three macrophyte species. The microbial community found in the rhizosphere of P. australis was particularly responsive to phenolic acids. Few differences in C fluxes and pools were observed between plots occupied by P. australis and Typha spp., but the replacement of S. latifolia by one of the two other species could have a significant effect on the C cycle in the Great Lakes coastal wetlands. [ABSTRACT FROM AUTHOR]

This study examined the response of Argilla Marsh in Ipswich, Massachusetts, USA to increased tidal flushing instituted to restore a salt marsh invaded by Phragmites australis. In late fall 1998, we replaced the old 0.9-m-diameter culvert feeding this marsh with a 2.4 × 1.5-m box culvert, thus increasing both the volume of tidal exchange and porewater salinity. We carried out yearly sampling of vegetation for two years pre-restoration and for four years after restoration. Analysis of Similarities (ANOSIM) showed that the plant community on the restored marsh had changed after restoration but that on the reference marshes had not. Over 80% of the change in the restored marsh was attributed to an increase in Spartina alterniflora cover and decreases in the cover of Phragmites australis, Typha angustifolia, and Solidago sempervirens. The two brackish species, P. australis and T. angustifolia showed an immediate negative response to the increased flooding and salinity. Surviving P. australis culms in the restored marsh were shorter in stature than they were prior to restoration, suggesting that the increased flooding and porewater salinities had lowered the productivity of this species. The increase in S. alterniflora post-restoration fit an exponential curve, indicating that there was a lag in its response initially, but then it expanded rapidly and was still in a very rapid expansion phase after four years. Despite an overall decline of P. australis on the scale of the whole marsh, there was a great deal of variation in responses of individual patches of P. australis to the restoration. Some declined, some were unchanged, and some even increased. The response of nekton to the restoration was less obvious than that of vegetation. Before restoration, the creek system in the tidally restricted marsh functioned like an impoundment that was only marginally connected to the larger salt marsh ecosystem. At that time, seining indicated that more species of nekton occurred at greater densities in creeks in the tidally restricted marsh than in the downstream reference. Increasing the tidal amplitude in the restored marsh resulted in an overall decline in the catch per unit effort there. In contrast to the creeks, the Spartina-dominated section of the flooded marsh surface in the restored marsh did harbor more Fundulus here roclitus, particularly the smaller size class, than did the downstream reference marsh or a P. australis patch in the restored marsh. Our analysis of vegetation and nekton suggests that Argilla Marsh was still adjusting to hydrologic changes four years after restoration. [ABSTRACT FROM AUTHOR]

The invasion of Phragmites australis (common reed) into Spartina alterniflora (cordgrass) salt marshes along the northeastern coast of the United States has recently been of concern. Numerous studies have evaluated the effects of P. australis on marsh nekton and infauna, but its effects on the distribution of stem-dwelling epifaunal communities has not been investigated previously. Standing living and dead plants of both species were collected periodically during three growing seasons (2000-2002) from brackish and salt marshes in New Jersey and Long Island, and the abundance, composition, and diversity of epifaunal communities associated with the stems of the two plant species were compared. Spartina alterniflora, particularly dead S. alterniflora, supported a higher density of animals than P. australis in 12 of the 19 samplings. When communities on standing live and dead stem were considered separately, higher abundances were found on dead S. alterniflora stems. Nematodes and harpacticoid copepods were the dominant taxa, with mites, annelids, and insects comprising minor components. Taxon-specific abundances tended to be higher on S. alterniflora stems, and community diversity was generally greater on this species as well. Between-site and between-year variation was observed. Relative to data recorded from sub-tropical salt marshes, the epifaunal communities in our samples were less abundant and diverse. Differences in the epiphytic communities associated with the two species, along with differences in stem structure, may explain why S. alterniflora stems support more epifaunal animals than P. australis stems overall. [ABSTRACT FROM AUTHOR]

Seedling establishment is an important means of re-colonizing herbicide-treated and burned Phragmites australis marshes and of filling in newly created or naturally forming marshes. Knowing the differential sensitivity of the various species to sulfide better enables us to predict which plants are likely to colonize given areas (i.e., be it desirable species or P. australis). This study focuses on the sulfide sensitivity of the seedlings of five plant species that may re-colonize the cleared marsh surface either from wild seed stock or introduced propagules: Spartina alterniflora, Spartina patens, Setaria magna, Atriplex triangularis, and P. australis. Seedlings were grown in culture tubes in semi-solid agar media containing Hoagland's nutrients; sulfide treatments included levels of sulfide from 0 to 8 mM. Parameters measured included number of leaves, number of lateral roots, shoot length, root length, leaf length, and biomass. Setaria magna proved to be the :most sensitive to sulfide, followed in order by A. triangularis, S. patens, P. australis, and S. alterniflora. Differences in edaphic sulfide are not likely to be helpful in favoring S. magna, A. triangularis, or S. patens over P. australis. Phragmites australis was compared to S. alterniflora in a second experiment with six concentrations of sulfide between 0 and 2.0 mM. Results indicated that sulfide levels between 0.4 and 0.9 mM would favor seedling establishment of S. alterniflora over P. australis, and at 0.9 mM, S. alterniflora seedlings would have the decided advantage. [ABSTRACT FROM AUTHOR]

The common reed, Phragmites australis, is a common feature in wetlands across North America. Recent studies have suggested that the widespread invasions of this species may be due to the introduction of a non-native strain from EurAsia. Since native populations persist in many areas where introduced populations are also found, a method for distinguishing population types is needed to facilitate management of the species. A restriction fragment length polymorphism (RFLP) assay was developed to distinguish native, non-native, and Gulf Coast type populations of Phragmites from each other. Two amplified non-coding chloroplast DNA regions are each cut with one restriction enzyme, allowing the distinction of native, non-native and Gulf Coast haplotypes from each other. When used together, these cut sites provide a low cost, rapid way of determining the origin of Phragmites populations. [ABSTRACT FROM AUTHOR]

We compared the ecophysiological performance of four dominant, perennial plant species of tidal marshes of northeastern North America (Phragmites australis, Typha angustifolia, Spartina alternifiora, and Leersia oryzoides), asking whether species that fall along a continuum of invasiveness vary consistently in terms of primary productivity, growth, biomass allocation, phenology, maximal photosynthetic rate, leaf turnover, tissue nutrient and chlorophyll content, and water use. During 1999, we examined plants growing at two brackish marshes and two freshwater tidal marshes in southern Connecticut, USA. Phragmites and Typha consistently exceeded the other two species in both marsh types in terms of ramet biomass, standing crop, length of the growing season, standing leaf area, leaf longevity, and total chlorophyll. Typha, Phragmites, and Spartina showed similar maximal photosynthetic rates across marsh types, significantly greater than the Pmax observed in Leersia. Foliar nitrogen was significantly greater in Phragmites than in all other species, suggesting that this species accrues nutrients more efficiently. Phragmites and Typha populations did not differ in a number of characters between freshwater and brackish marshes, indicating low sensitivity to exposure to moderate salinity levels. A principle components analysis placed Phragmites and Typha close to each other and more distant from Spartina and Leersia along axes describing components of competitive ability and photosynthetic performance. Thus, moderately and highly invasive species are distinct from less invasive species in terms of ecophysiology in both wetland types. As Phragmites australis and Typha angustifolia displace other plant species in marshes, they will likely influence the carbon- and nitrogen-cycling functions of wetlands, subject to the species' varying tolerances for salinity. [ABSTRACT FROM AUTHOR]

Components of the surface energy balance were measured using the Bowen ratio - energy balance method in three different communities (Phragmites australis, Scirpus acutus, and open water) in a wetland located in north-central Nebraska during the growing season of 1994. Duringdaytime, the heat storage term (S) was a considerably larger sink ofenergy in open water as compared to the vegetated communities (Phragmites and Scirpus). During nighttime, S was a significant source of energy in all three communities. As compared to the evapotranspiration(ET) from Phragmites and Scirpus, the evaporation (E) from open water (averaged over the measurement period) was about 25% smaller duringdaytime and three times larger during the night. The diurnal patternof ET in Phragmites and Scirpus generally followed that of Rn. The diurnal pattern of the open water E, however, did not follow Rn; rather, it seemed to depend on thermal stability conditions and air dryness. For the overall measurement period, the daily integrated (24-hour)evaporation from the open water area was 8% more than the evapotranspiration from the Phragmites-dominated part of the wetland and 17% more than the evapotranspiration from the Scirpus-dominated part of thewetland. [ABSTRACT FROM AUTHOR]

This study collected new data on sediment thickness and distributionand integrated it with existing data on the distribution of plant species within a small (0.5 ha) created, tidal salt marsh in Langley, Virginia, USA. The presence of the reed Phragmites australis was foundto be inversely correlated with sediment accumulation on the marsh surface. Sediment-deficient areas seem at a higher risk for invasion by P. australis and subsequent loss of designed marsh habitat. The results indicate that areas of low sediment accumulation may be used as a proxy measure for areas vulnerable to invasion. These areas can be easily delimited both in the field and on aerial photography. [ABSTRACT FROM AUTHOR]