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Introduced Phragmites australis represents a widespread threat to North American wetlands. Management agencies invest millions of dollars annually to manage the species, mostly by applying herbicides, to mitigate and prevent negative impacts. The often temporary reduction of P. australis rarely increases native diversity, and long‐term legacy effects of P. australis and repeat herbicide treatments are unknown. We used a coordinated management program targeting mostly small P. australis populations in the Adirondack Park in New York State, United States, to assess the potential for such legacy effects. We planted individuals of three native species as sentinels into treated and untreated, uninvaded reference wetlands after unassisted succession had occurred in treatment areas. Sentinel plants survived and grew in treated areas, suggesting legacy of P. australis and its management did not permanently limit establishment of native plants. However, responses were variable among sentinel species, with negative or neutral impacts on survival rates and neutral or positive effects on growth. Species‐specific responses and large variation in survival rates between sites and sentinels indicate that site factors are a dominant influence on survival and growth. Importantly, as treatment frequency increased, survival of one sentinel species decreased significantly, indicating a potential for long‐term negative impacts of repeated herbicide applications. Additional replanting after P. australis treatment and initial unassisted plant succession may enable more diverse plant communities to return, including species not able to recruit from local seed banks or seed sources. However, it remains unclear if active transplanting will enable more long‐term suppression of P. australis. [ABSTRACT FROM AUTHOR]

To increase the resilience of salt marshes subject to sea‐level rise impacts, managers can focus on interventions within current marsh footprints or in adjacent uplands to facilitate landward marsh migration. The latter approach may be more appropriate when degradation is severe and in situ intervention options are limited. Strategies for facilitating marsh migration include removing artificial barriers, soil grading to reduce steep topography, and manipulating adjacent upland vegetation that can hinder migration, but experiments testing the effectiveness of these activities are limited. We therefore conducted a field experiment to determine if physically removing three upland vegetation types (forest, shrub, and Phragmites australis) adjacent to a Rhode Island salt marsh facilitates short‐term marsh migration. Upland vegetation removal led to increased ambient light in all habitats, significantly enhanced marsh plant cover, extent, and elevation in shrub habitat, and declines in total bird abundance in forest and shrub habitats. Enhanced migration did not occur in forest or Phragmites habitats, and in shrubs, marsh plants only colonized where Baccharis halimifolia, common in upper marsh borders, had been removed. Five years after removal, all upland habitats and associated vegetation were indistinguishable from initial conditions. Our study suggests that upland plant removal might provide a limited window for facilitating salt marsh migration and that more intensive methods may be needed for sustained, longer‐term benefits. It also demonstrates that there may be ecological trade‐offs to consider when altering upland habitats to enhance landward marsh migration. [ABSTRACT FROM AUTHOR]

Societal Impact Statement Summary The invasive species S. alterniflora and P. australis are fast growing coastal wetland plants sequestering large amounts of carbon in the soil and protect coastlines against erosion and storm surges. In this global analysis, we found that Spartina and Phragmites increase methane but not nitrous oxide emissions, with Phragmites having a lesser effect. The impact of the invasive species on emissions differed greatly among different types of native plant groups, providing valuable information to managers and policymakers during coastal wetland planning and restoration efforts. Further, our estimated net emissions per wetland plant group facilitate regional and national blue carbon estimates. Globally, Spartina alterniflora and Phragmites australis are among the most pervasive invasive plants in coastal wetland ecosystems. Both species sequester large amounts of atmospheric carbon dioxide (CO2) and biogenic carbon in soils but also support production and emission of methane (CH4). In this study, we investigated the magnitude of their net greenhouse gas (GHG) release from invaded and non‐invaded habitats. We conducted a meta‐analysis of GHG fluxes associated with these two species and related soil carbon content and plant biomass in invaded coastal wetlands. Our results show that both invasive species increase CH4 fluxes compared to uninvaded coastal wetlands, but they do not significantly affect CO2 and N2O fluxes. The magnitude of emissions from Spartina and Phragmites differs among native habitats. GHG fluxes, soil carbon and plant biomass of Spartina‐invaded habitats were highest compared to uninvaded mudflats and succulent forb‐dominated wetlands, while being lower compared to uninvaded mangroves (except for CH4). This meta‐analysis highlights the important role of individual plant traits as drivers of change by invasive species on plant‐mediated carbon cycles. [ABSTRACT FROM AUTHOR]

In subtropical monsoon climate regions, traditional plants in constructed wetlands such as farmland ditches underperform in cold months, detracting from both purification capacity and esthetic appeal. To alleviate this weakness, this study introduced Phalaris arundinacea, a species with strong adaptability and cold tolerance, into a plant community dominated by Phragmites australis, constructing an ingenious composite plant community for year‐round water quality restoration and enhancement of attractiveness. First, laboratory simulations revealed significant seasonal differences in the removal rates of ammonia nitrogen (NH3‐N), total nitrogen (TN), and total phosphorus (TP) by the P. arundinacea community and P. australis community under different pollutant loads. Phragmites australis showed superior NH3‐N and TN removal capabilities from May to October, whereas P. arundinacea excelled in the rest of the months throughout the year. For TP removal, P. australis outperformed P. arundinacea from July to October, while P. arundinacea was more effective from January to May. We then verified this in rear farmland ditches, where P. australis were strategically partial substituted with P. arundinacea (Partial Replacement Treatment [PRT]), and compared it with unchanged farmland ditches (Control Treatment). We found that PRT enhanced decontamination efficiency over the year, especially significantly improving the water quality during colder months. Hence, this study advocates a novel strategy for effective annual decontamination and maintenance of wetlands such as farmland ditches, highlighting the importance of seasonally adaptive plant communities for water restoration. This transformative approach dramatically advances the field of wetland management, insisting on the important role of cold‐resistant species for year‐round ecosystem service optimization. [ABSTRACT FROM AUTHOR]

Intraspecific trait variation, essential to Darwin's mechanism of natural selection, has been widely examined for single characters. However, intraspecific variation of adaptive strategies which represent trade‐offs among multiple functional traits has received less attention, particularly for species that are globally distributed or invasive. Grime's competitor, stress tolerator and ruderal (CSR) scheme, well validated in the context of alien species invasions, provides both the theory and quantitative methodology to investigate adaptive strategies.Here, we quantified the intraspecific CSR strategy scores of a worldwide collection of 89 Phragmites australis genotypes which were cultivated in a common garden. We assessed the relationships between intraspecific variation in CSR strategy scores, genome size and climate of origin and tested whether the invasive and native lineages differ in CSR strategies.Substantial variation in intraspecific adaptive strategy, characterized mainly in C‐ and S‐selection, was observed. As expected, C‐, S‐ and R‐scores showed clear latitudinal clines and were strongly related to either genome size or climate of origin. Furthermore, invasive lineages were more stress adapted than native lineages.We conclude that the adaptive strategy of this perennial wetland grass varies globally, and its genotypes are surprisingly more stress tolerant in the invaded range where it was first detected ~150 years ago. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Coastal‐wetlands play a crucial role as carbon (C) reservoirs on Earth due to their C pool composition and functional sink, making them significant for mitigating global climate change. However, due to the development and utilization of wetland resources, many wetlands have been transformed into other land‐use types. The current study focuses on the alterations in soil organic‐C (SOC) in coastal‐wetlands following reclamation into aquaculture ponds. We conducted sampling at 11 different coastal‐wetlands along the tropical to temperate regions of the China coast. Each site included two community types, one with solely native species (Suaeda salsa, Phragmites australis and Mangroves) and the other with an adjacent reclaimed aquaculture pond. Across these 11 locations we compared SOC stock, active OC fractions, and soil physicochemical properties between coastal wetlands and aquaculture ponds. We observed that different soil uses, sampling sites, and their interaction had significant effects on SOC and its stock (p <.05). Reclamation significantly declined SOC concentration at depths of 0–15 cm and 15–30 cm by 35.5% and 30.3%, respectively, and also decreased SOC stock at 0–15 cm and 15–30 cm depths by 29.1% and 37.9%, respectively. Similar trends were evident for SOC stock, labile organic‐C, dissolved organic‐C and microbial biomass organic‐C concentrations (p <.05), indicating soil C‐destabilization and losses from soil following conversion. Soils in aquaculture ponds exhibited higher bulk density (BD; 11.3%) and lower levels of salinity (61.0%), soil water content (SWC; 11.7%), total nitrogen (TN) concentration (23.8%) and available‐nitrogen concentration (37.7%; p <.05) than coastal‐wetlands. Redundancy‐analysis revealed that pH, BD and TN concentration were the key variables most linked with temporal variations in SOC fractions and stock between two land use types. This study provides a theoretical basis for the rational utilization and management of wetland resources, the achievement of an environment‐friendly society, and the preservation of multiple service functions within wetland ecosystems. [ABSTRACT FROM AUTHOR]

Aim: Estuarine vegetation routinely experiences natural tidal fluctuations and is highly vulnerable to extreme events such as heavy rainfall, leading to changes in plant population structure and adaptability. Genetic and epigenetic modifications are widely considered to be mechanisms of phenotypic variation, triggered in plants responding to extreme changing environments. However, understanding on correlations among genetic, epigenetic, and phenotypic variation of wild plant populations is still limited. Location: China. Methods: In this study, populations of the typical wetland clonal species Phragmites australis were selected from four estuaries along various latitudes in China. Genetic and epigenetic diversity and phenotypic variation of these populations were analysed. Results: Phenotypic variation of P. australis populations was the highest at Yellow River Estuary and the lowest at Min River Estuary. Across all estuaries, Genetic and epigenetic diversity was strongly linear‐correlated. Genetic diversity had significant correlations with variation in reproductive traits, whereas epigenetic diversity had significant correlations with variation in growth traits. Climatic factors of mean annual temperature and precipitation, as well as soil nitrogen and phosphorus, were negatively correlated with variation in genetic diversity, epigenetic diversity, and variation in reproductive traits of P. australis populations along latitudes. Variation in growth traits was negatively correlated with soil salinity, reflecting the limiting effect of salinity on plant growth. Main Conclusion: Our findings found that genetic and epigenetic variations may play different roles in phenotypic variation of P. australis populations along latitudes, the variation becomes greater when the climatic and edaphic conditions deteriorate. The findings shed new light on the adaptation and evolution of wetland plant populations along a large latitudinal scale, and may contribute to the revegetation of estuary wetlands. [ABSTRACT FROM AUTHOR]

Escape from native range enemies can give invasive species a competitive edge according to the enemy‐release hypothesis. While more commonly associated with predators and herbivores, release from belowground microbial antagonists has been recently demonstrated to benefit invasive plants. Biogeographic variation in dominance and comparisons of soil communities suggest that invasive European Phragmites australis may have also benefitted from belowground enemy release in North America (NA). Here we examine the effects of native range (Europe) versus introduced range (NA) soil communities on European and North American P. australis using a reciprocal inoculation seedling growth experiment. Contrary to the enemy‐release hypothesis, we found that North American P. australis was sensitive to soil community origin in that the seedlings grown in European soil communities had higher total biomass than seedlings grown in North American soil communities. This pattern was not observed in the European P. australis seedlings which had similar biomass when grown with North American or European soil communities. Notably, North American P. australis had higher biomass than European P. australis regardless of which soil community it was grown in, suggesting a growth–defense tradeoff. Though the relative abundance of mutualists and pathogens composition did not differ between the two ranges, an indicator analysis revealed that mutualistic fungi and bacteria were key components of European soil communities but not in North American communities. Interestingly, North American soil communities had lower β diversity than European communities suggesting higher levels of community conservation among North American populations. This research represents the first evidence of growth–defense trade‐offs in North American P. australis and offers a novel mechanism in understanding the invasion of P. australis in NA. [ABSTRACT FROM AUTHOR]

Questions: Understanding drivers of biotic resistance has important implications for ecological restoration. Two potential drivers of biotic resistance that restoration practitioners can manipulate are native plant diversity and seeding density. Here we examined the effects of native plant species identity, native functional evenness, native seeding density and presence of Phragmites australis (a prolific invader in North America) on the growth of native species and invasion resistance to P. australis. Methods: We conducted two greenhouse experiments. In the first, native wetland species were grown in monoculture at one of two native seeding densities (1,938 pure live seed (PLS) per m2 or 9,688 PLS/m2) with or without P. australis. In the second experiment, native wetland species were grown in mixtures that differed in functional evenness at two levels of native seeding density (1,938 PLS/m2 or 9,688 PLS/m2) with or without P. australis. Results: The results of these experiments show certain high‐performing species drove final native and P. australis growth when tested individually, even overriding any effect of the functional evenness treatment when grown in mixtures. In addition, we found the effect of P. australis presence on native growth differed depending on the native identity and the growth metric measured (biomass, cover or intrinsic rate of growth). Finally, a higher native seeding density increased native growth and reduced P. australis growth, with the growth rate analysis yielding important insights into which species achieved these results fastest. Conclusions: Our results have three important implications for wetland restoration: (a) prioritize high‐performing native species for invasion resistance rather than necessarily focusing on functional diversity; (b) account for the fact that native species will vary in their performance, often in unexpected ways, under different contexts; and (c) seed at a high native seeding density, potentially orders of magnitude higher than current restoration practice, to sufficiently increase native growth and biotic resistance. [ABSTRACT FROM AUTHOR]

The maintenance of biological diversity is frequently enhanced in a heterogenous landscape by some level of disturbance. Thus, when a landscape becomes stabilized and homogenized through the spread of an invasive plant species, there may be consequences for native biodiversity, particularly for those biotas that depend on the pre‐existing, natural disturbance regime of that landscape. At Long Point, Ontario, Canada, a sandspit in Lake Erie, the community of anuran amphibians experienced the co‐incidence of 2 major disturbance events, 1 anthropogenic and 1 natural: an intervention to remove the invasive form of the common reed (Phragmites australis australis) and a spate of extensive dune washouts caused by high water levels and storms. As a result of the unequal distribution of disturbance in the landscape, different areas were affected by only the dune washouts, only the common reed treatment, both disturbances, or neither disturbance. From May to August 2021, we explored how the disturbances affected the resident frog and toad species habitat associations in the 4 different disturbance conditions in the landscape. By means of minnow traps, acoustic surveys, and visual surveys, we determined that the dune washouts had a greater influence on resident anurans than the common reed treatment. Ranid frogs (Ranidae) tended to inhabit non‐washout sites, whereas Fowler's toads (Anaxyrus fowleri) congregated in the newly formed, sand flats and shallow, de‐vegetated pools resulting from the washouts. Neither ranid frogs nor Fowler's toads demonstrated avoidance of the sites affected by the herbicide treatment and mechanical rollover of the common reed. This evidence of species sorting, which enables multiple species to persist in a dynamic and heterogeneous landscape, suggests that wildlife management in aid of threatened species recovery may find success by encouraging natural disturbance regimes in dynamic landscapes. Future management endeavors should consider refraining from complete dune stabilization in these landscapes to allow the natural washouts to occur at a higher frequency, while ensuring the continued effectiveness of the invasive common reed eradication. [ABSTRACT FROM AUTHOR]

Bedload sediment transport plays an important role in the evolution of rivers, marshes and deltas. In these aquatic environments, vegetation is widespread, and plant species have unique morphology. However, the impact of real plant morphology on flow and sediment transport has not been quantified. This study used model plants with real plant morphology, based on the aquatic species Phragmites australis, Acorus calamus and Typha latifolia. The frontal area of these species increases away from the bed, which leads to higher near‐bed velocity than would be predicted from depth‐average frontal area. A plant morphology coefficient was defined to quantify the impact of vertically‐varied plant frontal area. Laboratory experiments confirmed that the plant morphology coefficient improved the prediction of near‐bed velocity, near‐bed turbulent kinetic energy and bedload transport rate in canopies with realistic morphology. Plant morphology can alter transport rates by up to an order of magnitude, relative to the assumption of uniform morphology. Plain Language Summary: Aquatic vegetation is a crucial component of river, marsh and delta ecosystems. It has a significant impact on landscape evolution by altering sediment transport. Each vegetation species has a unique shape, but the impact of plant shape on sediment transport has not been previously investigated. This study explained how plant shape impacts sediment transport. Results show that differences in plant shape can change velocity and turbulence close to the channel bed, and thus alter sediment transport rate by an order of magnitude. Plants with greater vertical variation in shape, and specifically less plant volume near the channel bed, produced greater sediment transport. A parameter was defined to quantify the impact of plant shape on flow and sediment transport. By incorporating this parameter, our new model improves the prediction of sediment transport in vegetated regions. This study provides a method for describing the impact of plant shape on flow and sediment transport, which is important to the management and restoration of rivers, marshes and deltas. Key Points: Plant morphology influences the near‐bed velocity, turbulent kinetic energy (TKE) and bedload transport rate inside emergent canopiesA new model accounts for plant morphology in the prediction of near‐bed velocity and TKE and bedload transportFor each canopy solid volume fraction, plants with greater vertical variation in frontal area produce greater bedload transport [ABSTRACT FROM AUTHOR]

Seed‐based restoration of wetlands is often necessary to improve important ecosystem functions (e.g., invasion resistance and habitat provisioning) and meet society's need for wetland ecosystem services such as supporting recreational activities and improving water quality. However, persistent questions remain about the composition and sowing density of seed mixes needed to restore robust native wetland plant communities. In Great Salt Lake wetlands (Utah, USA), the revegetation of native species is crucial to recovering critical habitat and preventing reinvasion of the invasive, non‐native grass Phragmites australis and other invasive species (e.g., Typha spp.). In greenhouse and field experiments, we investigated the effects of seed mix composition and sowing density on plant community reassembly. We predicted that seed mixes containing native forb species with resource‐preempting traits (e.g., rapid seedling emergence and high aboveground growth rate) and high sowing densities (>5500 pure live seed m−2), would increase native plant light acquisition and establishment, thereby limiting invasive species. To our surprise, the effect of seed mix composition on native plant performance (cover and biomass) varied among the experiments, with distinct differences between plant functional groups arising. Native forb species had the highest performance in the greenhouse, but native grasses performed better in the field. Although multiple seed mix compositions show promise for establishing high native cover and biomass, these mixes may not always suppress invasive species. Interestingly, seed mix composition most often affected plant performance independent of sowing density. However, in one greenhouse experiment, we found that only slow‐growing mixes required a high sowing density to maximize native cover, an indication that the ideal sowing density may depend on the seed mix composition. Our research also supports the idea that in addition to reducing propagules of invasive species via appropriate management strategies, the application of higher sowing densities (>5500 pure live seed m−2) may lead to more favorable outcomes when a high density of invasive plant seeds remains or stressful field conditions are present. This research contributes to knowledge of plant community reestablishment in wetlands and demonstrates how seed‐based restoration strategies can catalyze native species revegetation and, in some situations, reduce the cover of invasive species. [ABSTRACT FROM AUTHOR]

The hydrological regime is considered to be the major factor that affects the distribution of arbuscular mycorrhiza (AM) fungi in wetlands. We aimed to investigate the responses of AM fungal community to different hydrological gradients. Illumina Miseq sequencing technology was used to study the AM fungal community structure in roots and rhizosphere soils of Phragmites australis in different moisture areas (dry area, alternating wet and dry area, and flooded area) in Mengjin Yellow River wetland. The rhizosphere soils and roots hosted different AM fungal communities. In roots, the AM fungal colonization and Chao1 richness in dry area were significantly higher than that in alternating wet and dry area and flooded area, but the community composition did not vary clearly under different water conditions. In rhizosphere soils, the Chao1 richness of AM fungi in flooded area was significantly higher than that in alternating wet and dry area and dry area, and the AM fungal community structure obviously differed across different areas. The redundancy analyses indicated that changes in the AM fungal community in soils were associated with altered soil properties, and the abundance of the dominant genus Glomus was mostly positively correlated with alkali‐hydrolyzable nitrogen in soils. This study helps us to understand the responses of AM fungal community to hydrological gradients in wetlands. [ABSTRACT FROM AUTHOR]

Understanding where consumers control plant reproduction in a time of changing plant–consumer interactions with environmental change can inform conservation. A seminal hypothesis—the environmental stress model (the ESM)—posits that consumer control of plants varies predictably with environmental stress. The ESM has been tested often along gradients of an abiotic stressor, yielding highly mixed support, although plants and consumers are often differently affected by a stressor.Here, to provide a conciliation, we introduced and tested a new ESM—the ESM in plants' versus consumers' perspectives. In field exclusion experiments conducted at three marsh sites that varied broadly in plant productivity, crab abundance and salinity within a coastal landscape, we tested the new ESM in predicting the impact of crab herbivores on the sexual reproduction of Phragmites australis. We analysed how their impact varied with plant productivity and crab abundance—proxies for environmental stresses in plants' and consumers' perspectives, respectively.We found that environmental stresses in plants' and consumers' perspectives were uncoupled across this coastal landscape. Neither crab abundance nor crab grazing intensity was correlated with plant productivity. Plant productivity and crab abundance were inconsistently related to key abiotic stressors including soil salinity.Depending on site, crab herbivores substantially suppressed Phragmites sexual reproductive effort (by >90%, by regulating a series of population‐ and individual‐level reproductive processes) or had little effect. Where crab herbivores had stronger impacts was not predicted by plant productivity, but largely by crab abundance via a threshold model. Above an abundance threshold, crabs increasingly suppressed Phragmites sexual reproductive effort.Synthesis. Our study revealed that consumer control of plant reproduction may be highly variable, even within a coastal landscape and for the same species, and that consumer abundance, rather than plant productivity, was a key predictor of this variation. As plants and consumers become increasingly uncoupled in many ecosystems under environmental change, the newly introduced ESM in plants' versus consumers' perspectives may be more versatile than previously recognized to inform conservation actions. [ABSTRACT FROM AUTHOR]

The effects of the addition of molasses (5 and 10% of dry matter: DM basis; M5 and M10 respectively) with or without urea (2%; U2, U2 + M5 and U2 + M10) on chemical and mineral composition, silage quality, microbial populations, buffering capacity and fermentation/digestion characteristics of common reed (Phragmites australis) ensiled under anaerobic conditions were investigated. The additives changed the silage quality of common reed compared with the control. Crude protein content was significantly (p < 0.0001) increased in urea‐containing silages, whereas ash‐free neutral detergent fibre concentration decreased in M10 compared with the control (p = 0.05). Treatment with 2% urea (U2) resulted in the reduction of most measured minerals with a severe decrease in iron concentration. The amount of gas produced after 96 h of incubation was, respectively, higher for U2, M10, U2M10, U2M5 and M5 compared with the control (p < 0.0001). Although the greatest in vitro dry matter digestibility and in vitro organic matter digestibility (96 h) were observed in U2 (p < 0.0001), no significant differences were found between U2 and M10. Supplementation with 10% molasses (M10) significantly increased lactic acid concentration, aerobic stability and total bacteria compared with other treatments (p < 0.0001). Moreover, DM loss (p = 0.0004), total yeast and mould (p < 0.0001) were significantly decreased as a result of 10% molasses treatment. Overall, it can be suggested that treating silage with 10% molasses (M10) has the potential to efficiently improve the nutritive value of common reed. [ABSTRACT FROM AUTHOR]

Plant invasions driven by global environmental changes (e.g. nutrient enrichment) increasingly threaten natural ecosystems. It is unclear whether reducing nitrogen (N) inputs helps to mitigate plant invasions in natural ecosystems.Using ongoing, landscape‐scale N reductions in the Yangtze River, we combined spatiotemporal surveys before and after reducing N inputs and manipulative experiments to explore how N reductions contributed to native community recovery in estuarine marshes degraded by plant invasions.We found that native Phragmites australis patches gradually recovered in Spartina alterniflora‐invaded marshes after reducing N inputs. The competitive advantage of S. alterniflora over P. australis decreased with N reduction, shifting the competitive outcomes away from P. australis exclusion to their coexistence.Synthesis and applications. Our findings reveal that the reversal of nitrogen enrichment may shift ecosystems from being more susceptible to invasion toward successional recovery, offering a promising approach for facilitating native community recovery in the invaded ecosystems. These findings have important implications for restoring invaded ecosystems, especially as global environmental change escalates the extent and impact of invaders by exacerbating current invasions and facilitating new ones. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate weed infestations of cotton (Gossypium hirsutum) fields in the region of Tarim River. Forty‐nine species among 17 families were identified in these cotton fields, and 24 of them were annuals. The eight dominant weed species in the cotton fields of Tarim River basin included Chenopodium glaucum, Solanum nigrum, Chenopodium album, Chenopodium hybridum, Bolboschoenus planiculmis, Sonchus arvensis, Phragmites australis, and Mulgedium tataricum. The number of weed species in the Aksu River tributary area, Yeerqiang River tributary area, and the upper and lower reaches of the Tarim River reached 29, 36, 35, and 33, respectively. Twenty species were found widely distributed among each basin. The dominant weeds in the cotton fields in the Aksu River basin and upper reaches of the Tarim River were S. nigrum and C. glaucum, those in the cotton fields in the Yarkand River basin included C. album and C. hybridum, and those in the cotton fields in the lower reaches of the Tarim River were C. glaucum and C. album. Notably the 20 common surveyed species of C. glaucum, S. nigrum, C. album, C. hybridum, B. planiculmis, S. arvensis, P. australis, M. tataricum, and others, could pose a serious challenge to regional crop production if not adequately controlled. As such, each cotton field should adopt a suitable weeding scheme with strengthened weed monitoring according to the local conditions, especially the weed distribution area characteristics. [ABSTRACT FROM AUTHOR]

Ecological stoichiometric homeostasis represents the physiological and biochemical adaptations of organisms to variations in environmental conditions and plays a pivotal role in maintaining ecosystem stability. However, existing literature predominantly concentrates on the changes in plant homeostasis under different external environments. There is a paucity of comparative analyses focusing on the stoichiometric homeostasis attributes among different types of halophytes, particularly using these halophytes as a primary investigative lens. In this study, by analyzing the differences in organ and soil ecological stoichiometry as well as salt accumulation characteristics of three halophytes (Phragmites communis, Suaeda salsa, and Tamarix chinensis) in the Yellow River Delta, we revealed the salt ion enrichment capacity and stoichiometric homeostasis characteristics of the three halophytes and clarified the adaptive capacity of the three halophytes in saline soil environments. Our results indicated that S. salsa accumulated more Na+ and Mg2+, while P. communis maintained a low salt content in its surrounding soil. The soil C:N ratios of P. communis and S. salsa negatively correlated with most ions, while T. chinensis displayed a positive correlation with ions. S. salsa demonstrated the highest ion enrichment but the least homeostasis, whereas T. chinensis showed superior homeostasis. We hypothesize that T. chinensis might have experienced a faster growth rate during the study period, and P. communis' topsoil appears to be more conducive for plant growth. The different salt tolerance strategies of these plants influenced homeostasis, with S. salsa demonstrating greater adaptability to soil modifications and higher potential in saline land management. These insights enhance our understanding of the physiological and ecological adaptations of halophytes and their contribution to improving the quality of saline soils in the Yellow River Delta. [ABSTRACT FROM AUTHOR]

Within‐species genetic diversity is shaped by multiple evolutionary forces within the confines of geography, and has cascading effects on the biodiversity of other taxa and levels. Invasive species are often initially limited in genetic diversity but still respond rapidly to their new range, possibly through 'pre‐adapted' genotypes or multiple sources of genetic diversity, but little is known about how their genetic structure differs from that of native species and how it alters the genetic‐species diversity relationship. Here, we selected a widespread native species Phragmites australis and its co‐occurring invasive competitor Spartina alterniflora as our model plant species. We investigated the genetic structure of P. australis using two chloroplast fragments and ten nuclear microsatellites in 13 populations along the Chinese coastal wetlands. We discovered a distinct geographical differentiation, showing that the northern and southern populations harbored unique genotypes. We also found a significant increase in genetic diversity (allelic richness and expected heterozygosity) from south to north. Combined with previous studies of S. alterniflora, the Mantel tests revealed a significant correlation of genetic distances between P. australis and S. alterniflora even when controlling for geographic distance, suggesting that the invasive species S. alterniflora might exhibit a phylogeographic pattern similar to that of the native species to some extent. Furthermore, our results suggest that the S. alterniflora invasion has altered the relationship between the genetic diversity of the dominant native plant and the associated species richness of soil nematodes. The reason for the alteration of genetic‐species diversity relationship might be that the biological invasion weakens the environmental impact on both levels of biodiversity. Our findings contribute to understanding the latitudinal patterns of intraspecific genetic diversity in widespread species. This work on the genetic diversity analysis of native species also provides significant implications for the invasion stage and ecological consequences of biological invasions. [ABSTRACT FROM AUTHOR]

Common reed is a widespread aquatic grass in wetland areas of Turkey. In reed samples, RNAs with the sequence of the Maize dwarf mosaic virus (MDMV) were found using high‐throughput sequencing. The nearly complete genome sequence comprised 9514 nucleotides. It contains a 5′ UTR of at least 145 nucleotides, a 3′ UTR of at least 237 nucleotides, and an ORF encoding a single polyprotein of 3041 amino acid residues. Two partial sequences were 7709 nt and 7858 nt long, respectively. Three reed sequences contained 22 nt, 25 nt, and 80 nt insertions in the 5′UTR, respectively. The coding region of MDMV TR‐34 (49%) was more conserved than UTRs (34.3%) compared to Johnsongrass mosaic virus (JGMV), Sugarcane mosaic virus (SCMV), and Sorghum mosaic virus (SrMV). MDMV‐TR34 reed isolate shares 91%–53.1% nucleotide identity and 98.2%–49% amino acid sequence similarity with other MDMV and three potyvirus sequences, respectively. Recombination analysis indicated six putative recombination events. In 2020–2022, the survey studies showed that 25 of 260 reed samples were infected with MDMV at the infection rate of 9.6% in Tekirdag province. This result is the first report of the complete nucleotidesequence of MDMV in the common reed, a reservoir host for cereals growing areas in Turkey. [ABSTRACT FROM AUTHOR]

Heavy metals (HMs), like chromium (Cr), manganese (Mn), and nickel (Ni), are toxic pollutants frequently detected in industrial wastewater. In this study, column‐type vertical‐flow constructed wetlands (CWs) filled with different substrates were examined for their ability to remove Cr, Mn, and Ni, focusing on their applicability to high HM concentrations (tens of mg/L) and short hydraulic retention times (2 days). Five candidate substrates—gravel, limestone, reddish soil, wood pellets, and activated carbon—were screened for their ability to remove 6 mg/L of the three HMs, revealing that reddish soil and activated carbon removed all three HMs efficiently. Further experiments to remove 60 mg/L of HMs were conducted using CWs filled with reddish soil or activated carbon with or without planting Phragmites australis. The results indicated that (1) substrate adsorption contributed exclusively to HM removal and the effects of planting may be negligible, and (2) activated carbon (removal efficiency of 74–99%, 98–99%, and 99% for Cr, Mn, and Ni, respectively) is likely a more promising substrate than reddish soil (removal efficiency of 90–99%, 48–99%, and 61–99% for Cr, Mn, and Ni, respectively) in light of its ability to achieve efficient HM removal under high loading conditions. [ABSTRACT FROM AUTHOR]

The ability of native communities to maintain invasion resistance in the face of environmental changes is crucial for biodiversity conservation. However, previous studies have primarily focused on the inhibitive effects experienced by invaders, providing limited insights into the ultimate outcome of resistance.In this study, we integrated modern coexistence theory into biotic resistance research to investigate the impact of nutrient enrichment on the resistance of Phragmites australis marshes to Spartina alterniflora invasion in the Yangtze estuary saltmarshes of China.Our results demonstrated that under non‐enriched conditions, successful invasion resistance was facilitated by stable coexistence between native and invasive species in the field. This prediction of invasion resistance aligned with the distribution dynamics of the two species in the Yangtze estuary saltmarshes over the past two decades. However, nutrient enrichment was likely to lead to a fundamental shift in their coexistence and ultimately, the failure of resistance.Synthesis and applications. Integrating modern coexistence theory into biotic resistance studies advances the assessment of invasion resistance by shifting from quantifying relative strength to predicting explicit resistance outcomes. Ecosystem managers can draw explicit conclusions about the potential establishment and impact of invaders by analysing observational or experimental data within the framework of modern coexistence theory. This information aids in identifying the most efficient strategies for addressing invasive species. [ABSTRACT FROM AUTHOR]

Both genetic and phenotypic intraspecific diversity play a crucial role in the ecological and evolutionary dynamics of organisms. Several studies have compared phenotypic divergence (Pst) and differentiation of neutral loci (Fst) to infer the relative roles of genetic drift and natural selection in population differentiation (Pst–Fst comparison). For the first time, we have assessed and compared the genetic variation and differentiation at the leaf trait level in two key macrophytes, Phragmites australis and Nuphar lutea.To this aim, we quantified and described the genetic structure and phenotypic diversity of both species in five lake systems in north‐central Italy. We then investigated the relative roles of genetic drift and natural selection on leaf trait differentiation (Pst–Fst), assuming that Fst reflects divergence caused only by genetic drift while Pst also incorporates the effects of selective dynamics on the phenotype.In terms of genetic structure, the results for P. australis were in line with those observed for other Italian and European conspecific populations. Conversely, N. lutea showed a more complex genetic structure than expected at the site level, probably due to the combined effect of genetic isolation and its mixed mating system. Both species exhibited high variability in leaf functional traits within and among sites, highlighting a high degree of phenotypic plasticity. Pst–Fst comparisons showed a general tendency towards directional selection in P. australis and a more complex pattern in N. lutea. Indeed, the drivers of phenotypic differentiation in N. lutea showed a variable mix of stabilising and directional selection or neutral divergence at most sites.The prevalence of vegetative over generative reproduction leads P. australis populations to be dominated by a few clones that are well adapted to local conditions, including phenotypes that respond plastically to the environment. In contrast, in N. lutea, the interaction of a mixed mating system and geographical isolation among distant sites tends to reduce the effect of outbreeding depression and provides the genetic basis for adaptive capacity.The first joint analysis of the genetic structure of these two key macrophytes allowed a better understanding of the relative roles of genetic drift and natural selection in the diversification of phenotypic traits within habitats dominated by P. australis and N. lutea. [ABSTRACT FROM AUTHOR]

Salinity is a widespread abiotic stress, which has strong adverse effects on plant growth and crop productivity. Exopolysaccharides (EPS) play a crucial role in plant growth‐promoting rhizobacteria (PGPR)‐mediated improvement of plant stress tolerance. This study aimed to assess whether Glutamicibacter sp. strain producing large amounts of EPS may promote tolerance of common reed, Phragmites australis (Cav.) Trin. ex Steud., towards salt stress. This halotolerant rizhobacterium showed tolerance to salinity (up to 1 M NaCl) when cultivated on Luria‐Bertani (LB) medium. Exposure to high salinity (300 mM NaCl) significantly impacted the plant growth parameters, but this adverse effect was mitigated following inoculation with Glutamicibacter sp., which triggered higher number of leaves and tillers, shoot fresh weight/dry weight, and root fresh weight as compared to non‐inoculated plants. Salt stress increased the accumulation of malondialdehyde (MDA), polyphenols, total soluble sugars (TSSs), and free proline in shoots. In comparison, the inoculation with Glutamicibacter sp. further increased shoot polyphenol content, while decreasing MDA and free proline contents. Besides, this bacterial strain increased tissue Ca+ and K+ content concomitant to lower shoot Na+ and root Cl− accumulation, thus further highlighting the beneficial effect of Glutamicibacter sp. strain on the plant behavior under salinity. As a whole, our study provides strong arguments for a potential utilization of EPS‐producing bacteria as a useful microbial inoculant to alleviate the deleterious effects of salinity on plants. [ABSTRACT FROM AUTHOR]

The total amount and rate of atmospheric nitrogen (N) deposition are constantly increasing, which substantially influences the soil microbial community structure and function. However, it is still unclear whether the responses of different plant rhizosphere soil bacterial community to short‐term N addition was consistent. Based on 16s rRNA sequencing, we investigated the responses of rhizosphere and bulk soil bacterial community of halophytes (salt‐absorbing, salt‐rejecting, and salt‐secreting plant) to short‐term N addition in the Yellow River Delta. The bacterial community α‐diversity of Suaeda salsa (salt‐absorbing plant) was significantly higher in rhizosphere soil than in bulk soil, while no significant difference between Phragmites communis (salt‐rejecting plant) rhizosphere and bulk soil bacterial community α‐diversity was found. The differences were mainly ascribed to the higher N uptake capacity of P. communis, which resulted in no difference in N content between rhizosphere and bulk soil. The short‐term N addition significantly increased the α‐diversity of bacterial community in the rhizosphere soil of Aeluropus sinensis (salt‐secreting plant), but there was no effect on the α‐diversity of bacterial community in the rhizosphere soil of P. communis. Nitrogen addition enhances the salt uptake capacity of A. sinensis and alleviates the salt stress of bacterial growth. The relative abundance of Bacteroidetes for S. salsa and A. sinensis was significantly higher in rhizosphere soil than in bulk soil, and the relative abundance of Actinobacteria for P. communis and S. salsa was higher and lower in rhizosphere soil than in bulk soil, respectively. Salt‐absorbing of S. salsa leads to elevated rhizosphere soil salinity. Higher salinity and abundant carbon promote the Bacteroidetes and inhibit the Actinobacteria. Short‐term N addition caused an increase in the relative abundance of Gemmatimonadetes in halophyte rhizosphere soil and a decrease in the relative abundance of Firmicutes in S. salsa and A. sinensis bulk soil, which may be due to the different response of C:N of root secretions to N addition in halophytes. The relative abundance of rhizosphere soil denitrifying bacteria was higher in S. salsa and A. sinensis than in P. communis, while the reverse was observed for N‐fixing bacteria. The relative abundance of denitrifying bacteria decreased in P. communis and increased in S. salsa and A. sinensis. The low N soil environment of P. communis promotes the activity of N‐fixing bacteria, and the abundant N content of S. salsa and A. sinensis soil promotes the denitrification process. The research clarified that the response of soil bacterial community to short‐term N addition Treatment differed due to the influence of plant species and that N additions had smaller effects on the bacterial community than plant species. [ABSTRACT FROM AUTHOR]

Aim: Latitudinal variation in biotic interactions is recognized as a driver underlying variation in plant invasion success and therefore an important issue in conservation biogeography. However, previous studies have mainly focused on interactions between living plants and herbivores, whereas litter traits and detritivory have been hardly studied along latitude or compared between native and invasive plants. Our aim was to compare latitudinal variation in leaf litter chemistry and palatability to detritivores between invasive and native plants, and investigate which chemical traits determine detritivory and whether they are climate‐driven. Location: China. Taxa: Spartina alterniflora, Phragmites australis, Porcellio laevis, Chiromantes dehaani. Methods: We combined field surveys with laboratory experiments to compare latitudinal variation in litter chemistry between the widespread invasive Spartina alterniflora and its native competitor Phragmites australis across their co‐occurring range (20.9–40.7° N, ~2200 km). For both species, we examined litter palatability to two common detritivores (Porcellio laevis and Chiromantes dehaani) along the same latitude. We also analysed relationships among climate, litter traits and detritivory. Results: In five of nine litter traits, we found latitudinal clines, with little difference between the two plant species in how they responded across the gradient. Litter palatability decreased with increasing latitude, but was generally higher in Spartina than Phragmites. Two key litter traits (C:P ratio and flavonoid content) were significantly associated with temperature of origin and with detritivory. Main Conclusions: There were geographic clines in litter traits and palatability, with strong links between climate, litter chemistry and detritivory, in both Spartina and Phragmites. Spartina litter, however, was more rapidly decomposed by detritivores, which could create positive feedbacks, and contributes to the successful Spartina invasion along China's coast. Future ecological restoration projects should therefore dispose Spartina plant tissue or litter off‐site, to reduce the competitiveness of Spartina and support the conservation of native Phragmites. [ABSTRACT FROM AUTHOR]

An invasion of Roseau cane scale, Nipponaclerda biwakoensis, native to East Asia, is associated with recent widespread dieback of common reed stands in the Mississippi River Delta, Louisiana. A previous study suggested that, in its native range, the combined mortality from Common Reed Bunting Emberiza schoeniclus and parasitoid wasps may control the abundance of Roseau cane scale. However, there is limited knowledge about which other bird species may prey on Roseau cane scale or the feeding patterns of these birds. Here we used web search and citizen science monitoring data to tabulate bird predation events on Roseau cane scales across sites in Japan and determine which bird species may be the most important predators and when the observed feeding typically occurs. We scanned web entries using both Google image searches and the social networking services including Twitter, Instagram, and Facebook. Additionally, we accessed long‐term field observation records obtained by volunteer monitoring conducted by the members of the Kanagawa Branch of the Wild Bird Society of Japan. By using these citizen science approaches, we detected 16 bird species, mainly Common Reed Bunting but also other migratory and resident species, preying on the Roseau cane scale in reed beds throughout central Japan and most detection occurred during the winter. This study demonstrates that biological information obtained from publicly available data from citizen observers can be useful for exploring ecological patterns of various species including potential predators against invasive species. [ABSTRACT FROM AUTHOR]

The definition of simple and accurate methods to estimate flow resistance in vegetated channels is still a challenging issue in soil bioengineering practices and programming riparian vegetation management to control channel conveyance capacity, sediment deposition, and flooding propensity. In this paper, measurements collected by Errico et al. (2018, 2019) in drainage channels colonized by common reed (Phragmites australis) were used to study the effect of flexible vegetation and its management in flow resistance estimate. At first, a theoretical flow resistance equation, obtained applying dimensional analysis and incomplete self‐similarity condition for the velocity distribution of an open channel flow, was briefly summarized. Then, this flow resistance equation was calibrated and tested by open‐field hydraulic experiments carried out by Errico et al. (2018, 2019) at the real scale of existing vegetated drainage channels. In particular, the Γ function of the power velocity profile was empirically related to the slope energy and the flow Froude number by using the available measurements. Taking into account the hydrological regime of the flow in the investigated channels, the original data set was divided into two sub‐data sets (calibrating and testing data set) exploring the same range of measured discharges. The calibration and testing of the flow resistance equation were carried out without distinguishing measurements corresponding to different vegetation conditions (full‐vegetated, half‐vegetated, non‐vegetated, central vegetation cut, extensive vegetation cut). The analysis demonstrated that the theoretical flow resistance equation allows an accurate estimate of the Darcy‐Weisbach friction factor which is characterized by errors that are always less than 10% and less than or equal to 5% for 90.9% of the investigated cases. The finding of this study also allowed to evaluate the effects of different vegetation management scenarios on flow resistance. [ABSTRACT FROM AUTHOR]

With increasing global awareness of the ecological services that wetlands can provide, an increased emphasis has been placed on the need for wetland restoration projects. Among the types of wetland restoration projects that have been initiated are those that aim to return farmlands back to their previous wetland state to restore wetland vegetation and regain the ecological services that had been lost. However, studies on the changes of belowground bacterial diversities following the conversion of farmlands back to wetlands are rare, especially in coastal areas. In the present study, we examined the soil characteristics and the microbial diversity of the soil and roots across Phragmites australis–dominated coastal marshes within the Yellow River Delta. We sampled two marshes that had been restored 11 and 3 years prior to sampling (11‐year site and 3‐year site, respectively). We also sampled two additional, undisturbed wetlands—one within the new Yellow River course (NC site), and the other within the abandoned Yellow River course (OC site)—to serve as controls to assess the effectiveness of the wetland restoration project. Specifically, we measured the concentrations of nutrients and organic matter in the soil, the activities of the enzymes urease, sucrase, and alkaline phosphatase in the soil, and the diversity of the microbial communities in the soil and roots. The results showed that the concentrations of soil nutrients and the activities of the soil enzymes were significantly greater in the 11‐year site compared to the 3‐year site but were similar between the 11‐year site and the NC site. Shannon, Simpson, and Pielou indices of diversity among the soil bacteria were positively correlated with the concentrations of soil nutrients and the activities of the soil enzymes, which were generally lowest in the 3‐year site compared to the other study sites. The diversity indices among the root bacteria, however, did not exhibit a similar trend. The bacterial community composition of the soil and roots differed between sites. The relative abundance of Firmicutes in the soil and roots was highest in the 3‐year site compared to the 11‐year, NC, and OC sites. The relative abundance of soil Bacteroidetes was higher in the soils of the NC and OC sites compared to in those of the restoration sites. Overall, the diversity richness of the subsurface bacterial communities increased with the time since the restoration of these wetlands, and after 11 years post‐restoration, appeared to resemble those of the natural wetlands of the area. Our results therefore imply that future assessments of coastal wetland restoration projects could be made based in part on soil nutrient concentrations, enzyme activities, and the microbial diversity of the soil and plant roots within these systems. [ABSTRACT FROM AUTHOR]

Premise: To genetically discriminate subspecies of the common reed (Phragmites australis), we developed real‐time quantitative (qPCR) assays for identifying P. australis subsp. americanus, P. australis subsp. australis, and P. australis subsp. berlandieri. Methods and Results: Utilizing study‐generated chloroplast DNA sequences, we developed three novel qPCR assays. Assays were verified on individuals of each subspecies and against two non‐target species, Arundo donax and Phalaris arundinacea. One assay amplifies only P. australis subsp. americanus, one amplifies P. australis subsp. australis and/or P. australis subsp. berlandieri, and one amplifies P. australis subsp. americanus and/or P. australis subsp. australis. This protocol enhances currently available rapid identification methods by providing genetic discrimination of all three subspecies. Conclusions: The newly developed assays were validated using P. australis samples from across the United States. Application of these assays outside of this geographic range should be preceded by additional testing. [ABSTRACT FROM AUTHOR]

Plant‐mediated CH4 emission is an important part of the ecosystem CH4 emission from vegetated wetlands. Inundation depth may alter the potential magnitude of CH4 releases by changing CH4 production and plant transport, but the relationships between plant‐mediated CH4 emissions and inundation depth are still uncertain, especially for estuarine wetlands with changeable hydrological processes. Besides, there are conflicting results regarding the role of inundation depth in plant‐mediated CH4 emissions.Here we conducted a novel inundation depth experiment (0, 5, 10, 20, 30 and 40 cm inundation depth) dominated by Phragmites australis in the Yellow River estuary, China. Soil CH4 emissions, ecosystem CH4 emissions, net ecosystem CO2 exchange (NEE), soil organic carbon (SOC) and plant traits were measured during the growing seasons of 2018, 2019 and 2020. Plant‐mediated CH4 emissions were the difference between ecosystem CH4 emissions and soil CH4 emissions.The results showed that inundation depth decreased soil CH4 emissions but increased ecosystem CH4 emissions. Plant‐mediated CH4 transport from Phragmites australis accounted for 99% of total ecosystem CH4 emissions under different inundation depths. Inundation depth strongly stimulated plant‐mediated CH4 emission from 0 to 20 cm during the growing seasons. The increased NEE enhanced plant‐mediated CH4 emissions by altering production, suggesting that carbon components derived from photosynthetic carbon input may benefit CH4 production. Additionally, the increased plant height promoted CH4 emission by regulating plant transport, indicating that plant traits may play an important role in transport of CH4.Our findings indicated that NEE and plant height play an important role in plant‐mediated CH4 emissions under different inundation depths in estuarine wetland. This study also highlights that hydrological regimes and plant traits are essential for the estimation of CH4 emissions in future projections of global wetland changes. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The scarcity of water is perceived as a systematic global risk due to increasing water demand. Vertical flow constructed wetland (VFCW) is proposed as an energetically efficient and economical process to treat greywater (GW) for non‐potable purposes. Macrophyte contributes a significant amount to the treatment process, and it depends on species, and their ecology. In this study, four single‐stage VFCW systems were planted with locally available plant species named Hymenocallis littoralis as Plant 1, Phragmites australis as Plant 2, Canna indica Plant as 3, and Colocasia as Plant 4, which were used for the treatment of GW. The mean removal efficiencies associated with Plant 1, Plant 2, Plant 3, and Plant 4 are 55.13%, 48.11%, 52.53%, and 56.39% for chemical oxygen demand (COD); 45.35%, 35.36%, 64.10%, and 56.39% for ammonia; and 32.97%, 20.85%, 71.57%, and 33.40% for phosphate, respectively. All systems show significant removal efficiency (more than 40%) of all pollutants, except TDS and pH. Among all the observed plants, C. indica achieved the highest removal efficiency for COD, ammonia, and phosphate. The obtained results were analyzed for the dependency of correlations with effluent, influent, and macrophytes used in the treatment system. The principal component analysis (PCA) identified two principal components from 13 variables and explained 50.25%, 47.47%, and 45.62% variance of normalized datasets in VFCW. The PCA also shows significant correlations of plant species with different targeted effluent parameters. [ABSTRACT FROM AUTHOR]

Successful invasive plant management—where invaders are sufficiently reduced and diverse native plant communities recover—remains an elusive goal for land managers. The site‐ and landscape‐scale drivers of variable management outcomes and vegetation recovery are poorly understood due to a lack of rigorous experiments that characterize longer term vegetation trends across contexts. We present the results of a five‐year experiment across eight subestuaries of Chesapeake Bay, representing a gradient of watersheds with differing dominant land‐use types and anthropogenic impacts, to evaluate invasive and native plant response to herbicide management. The focal invader, Phragmites australis (common reed), is one of the most aggressive and pervasive invasive plants in North American wetlands. We found that with multiyear herbicide treatments, it was possible to greatly reduce Phragmites across an array of subestuaries while increasing the cover and quality of native plant communities. Yet, by the end of the study, plant community composition in all Phragmites‐managed sites remained distinct from, even if composition was shifting toward, reference sites. There was also large inter‐site variation in the vegetation responses related to site environmental conditions and subestuary vegetation conditions. We uncovered specific aspects of the surrounding landscape that were linked to improved vegetation recovery—the species richness and conservation value of nearby wetlands. Results from this five‐year experiment conducted at multiple sites in Chesapeake Bay inform what is possible for management, particularly in more degraded landscapes and sites where setting realistic expectations and pragmatic goals will be essential. Assessing environmental and vegetation conditions of the site and surrounding landscape prior to commencing invasive species management is critical to predict the time and effort required to achieve restoration goals. [ABSTRACT FROM AUTHOR]

A blue‐green bioeconomy revolution is underway in Europe, with particular attention being paid to the development of new or underutilized marine biomass resources. The wild harvest and mariculture of low‐trophic non‐fed species of marine biomass may be contributing to circular economies, the mitigation of environmental problems such as eutrophication and climate change through the uptake of nutrients and carbon, while also recovering finite phosphorus from marine coastal environments, thus contributing to food security. The present study provides a cradle‐to‐gate life cycle perspective on seven established or innovative/emerging marine biomass utilization cases in Sweden: mariculture of sugar kelp, blue mussels, and ascidians and the harvest of invasive Pacific oysters along the Skagerrak coast, the mariculture of blue mussels in the Baltic sea, the harvest of common reed in the Stockholm archipelago, and the harvest of beach‐cast seaweed in Gotland. Results showed that the mariculture cases were found to contribute to eutrophication and climate impact mitigation (at gate). All cases were found to contribute to closing the loop on phosphorus by enabling recovery from marine or coastal environments, bridging marine–land flows, all while performing well from an environmental perspective with a relatively low cumulative energy demand and low carbon and nutrient footprints. This highlights the potential of low‐trophic biomass to contribute to phosphorus security in the future, and demonstrates the value of industrial ecology tools such as LCA in support of this imminent Decade of Ocean Science for Sustainable Development. [ABSTRACT FROM AUTHOR]

Sowing native seeds is a common approach to reintroduce native plants to degraded systems. However, this method is often overlooked in wetland restoration despite the immense global loss of diverse native wetland vegetation. Developing guiding principles for seed‐based wetland restoration is critical to maximize native plant recovery, particularly in previously invaded wetlands. Doing so requires a comprehensive understanding of how restoration manipulations, and their interactions, influence wetland plant community assembly. With a focus on the invader Phragmites australis, we established a series of mesocosm experiments to assess how native sowing density, invader propagule pressure, abiotic filters (water and nutrients), and native sowing timing (i.e., priority effects) interact to influence plant community cover and biomass in wetland habitats. Increasing the density of native seeds yielded higher native cover and biomass, but P. australis suppression with increasing sowing densities was minimal. Rather, community outcomes were largely driven by invader propagule pressure: P. australis densities of ≤500 seeds/m2 maintained high native cover and biomass. Low‐water conditions increased the susceptibility of P. australis to dominance by native competitors. Early sowing of native seeds showed a large and significant benefit to native cover and biomass, regardless of native sowing density, suggesting that priority effects can be an effective restoration manipulation to enhance native plant establishment. Given the urgent wetland restoration need combined with the limited studies on seed‐based wetland restoration, these findings provide guidance on restoration manipulations that are grounded in ecological theory to improve seed‐based wetland restoration outcomes. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) in coastal wetlands, also known as "blue C," is an essential component of the global C cycles. To gain a detailed insight into blue C storage and controlling factors, we studied 142 sites across ca. 5000 km of coastal wetlands, covering temperate, subtropical, and tropical climates in China. The wetlands represented six vegetation types (Phragmites australis, mixed of P. australis and Suaeda, single Suaeda, Spartina alterniflora, mangrove [Kandelia obovata and Avicennia marina], tidal flat) and three vegetation types invaded by S. alterniflora (P. australis, K. obovata, A. marina). Our results revealed large spatial heterogeneity in SOC density of the top 1‐m ranging 40–200 Mg C ha−1, with higher values in mid‐latitude regions (25–30° N) compared with those in both low‐ (20°N) and high‐latitude (38–40°N) regions. Vegetation type influenced SOC density, with P. australis and S. alterniflora having the largest SOC density, followed by mangrove, mixed P. australis and Suaeda, single Suaeda and tidal flat. SOC density increased by 6.25 Mg ha−1 following S. alterniflora invasion into P. australis community but decreased by 28.56 and 8.17 Mg ha−1 following invasion into K. obovata and A. marina communities. Based on field measurements and published literature, we calculated a total inventory of 57 × 106 Mg C in the top 1‐m soil across China's coastal wetlands. Edaphic variables controlled SOC content, with soil chemical properties explaining the largest variance in SOC content. Climate did not control SOC content but had a strong interactive effect with edaphic variables. Plant biomass and quality traits were a minor contributor in regulating SOC content, highlighting the importance of quantity and quality of OC inputs and the balance between production and degradation within the coastal wetlands. These findings provide new insights into blue C stabilization mechanisms and sequestration capacity in coastal wetlands. [ABSTRACT FROM AUTHOR]

Root system characteristics are of fundamental importance to soil improvement and underground resource acquisition in riparian buffer strips. Root architectural traits determine the in situ space‐filling properties of a root system. The aims of this study were to examine the grassland root morphological characteristics in the vegetation zone from the lower reaches of Yellow River. Five natural homogeneous grasslands including Imperata cylindrica, Phragmites australis, Cynodon dactylon, Artemisia argyi and Juncellus serotinus were selected. Seven root architecture parameters including fractal dimension, total root length, total root surface area, total root volume, average diameter, root crossing number and root tip number were analyzed, and comprehensive scores were evaluated using principal component analysis. The results showed that average root diameter of the five herbaceous plants was ranged from 0.42 to 0.78 mm. The total root length, total root surface area, total root volume, root crossing number and root tip number of I. cylindrica and P. australis were significantly higher than those of C. dactylon, A. argyi and J. serotinus. The main factors influencing root architecture were average diameter, total root surface area and total root volume through principal component analysis. I. cylindrica had the highest comprehensive score, followed by P. australis, A. argyi, C. dactylon and J. serotinus. I. cylindrica and P. australis would be good competitors for both soil resource acquisition and soil quality improvement due to their root traits. These results could provide a scientific basis for evaluating the ecological function of riparian vegetation. [ABSTRACT FROM AUTHOR]

Accounting for the impact of riparian plant communities on water balances is usually ignored due to the lack of data and information on water use of these plant communities. This is especially important for areas with limited water resources and in areas where water resources are shared between different users (agriculture, riparian zones, other ecosystems/agro‐ecosystems, municipalities, recreational, mining, agro‐ecology, etc.). Modelling stomatal resistance (rL) of riparian vegetation species is a complex process, but is also one of the limited processes to estimate evaporative losses for these plant communities for more inclusive, complete and robust water balance and hydrologic analyses for forecasting, planning, allocating and managing surface and groundwater resources and for hydrologic modelling. The objectives of this research were to (i) modify Jarvis‐type model for estimating rL for three riparian plant species [Common reed (Phragmites australis), Peach‐leaf willow (Salix amygdaloides) and Cottonwood (Populus sect. Aigeiros)], (ii) investigate the rL response to microclimate/environmental variables, and (iii) evaluate the photosynthetic photon flux density (PPFD) versus rL response curves for estimating hourly rL. A Jarvis‐type model was modified by re‐parametrization using porometer‐measured data collected via extensive field campaigns in 2009 and 2010. Flooding in 2010 impacted the phenology and physiology of all species with increased rL and impedance in growth due to oxygen stress. While R2 values were generally low for both years for all species, the response of rL to the same climate variables under the same environmental conditions exhibited substantial variations between the species. Overall, the response of rL to climatic variables was species‐specific, complex and varied with surface and atmospheric conditions. For all species, stronger relationships between rL versus air temperature and net shortwave radiation were observed. The Jarvis‐type model underestimated rL for all species and hence required independent re‐parameterization for each specie independently. The model performance after re‐parameterization improved substantially during both calibration and validation. Validation of the new modified Jarvis‐type model (NMJ‐model) resulted in good estimates of rL with root‐mean‐squared difference (RMSD) and R2 values of 31 s m−1 and 0.51 for Common reed; 56 s m−1 and 0.81 for Peach‐leaf willow; and 237 s m−1 and 0.51 for Cottonwood, respectively. Strong agreements were found between measured and re‐parameterized NMJ‐model‐estimated rL values for all three species in both years, but the relationships improved significantly in 2009 with no flooding. The NMJ‐model‐estimated rL values were within 10, 7 and 11% of the measured values for Common reed, Peach‐leaf willow and Cottonwood, respectively. rL values estimated using PPFD versus rL response curves developed for individual species were used to estimate hourly rL and the response curves were able to effectively track the trends and magnitudes of rL. With re‐parameterization, the NMJ‐models developed and tested for each riparian vegetation specie provide robust estimates of rL that can be used to quantify evaporative losses of these riparian plant communities for more complete local and regional water balance analyses by accounting for riparian vegetation water use. [ABSTRACT FROM AUTHOR]

Nest predation is the main cause of nest failure for ducks. Understanding how habitat features influence predator movements may facilitate management of upland and wetland breeding habitats that reduces predator encounter rates with duck nests and increases nest survival rates. For 1618 duck nests, nest survival increased with distance to phragmites (Phragmites australis), shrubs, telephone poles, human structures, and canals, but not for four other habitat features. Using GPS collars, we tracked 25 raccoons (Procyon lotor) and 16 striped skunks (Mephitis mephitis) over 4 years during waterfowl breeding and found marked differences in how these predators were located relative to specific habitat features; moreover, the probability of duck nests being encountered by predators differed by species. Specifically, proximity to canals, wetlands, trees, levees/roads, human structures, shrubs, and telephone poles increased the likelihood of a nest being encountered by collared raccoons. For collared skunks, nests were more likely to be encountered if they were closer to canals, trees, and shrubs, and farther from wetlands and human structures. Most predator encounters with duck nests were attributable to a few individuals; 29.2% of raccoons and 38.5% of skunks were responsible for 95.6% of total nest encounters. During the central span of duck nesting (April 17–June 14: 58 nights), these seven raccoons and five skunks encountered >1 nest on 50.8 ± 29.2% (mean ± SD) and 41.5 ± 28.3% of nights, respectively, and of those nights individual raccoons and skunks averaged 2.60 ± 1.28 and 2.50 ± 1.09 nest encounters/night, respectively. For collared predators that encountered >1 nest, a higher proportion of nests encountered by skunks had evidence of predation (51.9 ± 26.6%) compared to nests encountered by raccoons (22.3 ± 17.1%). Because duck eggs were most likely consumed as raccoons and skunks opportunistically discovered nests, managing the habitat features those predators most strongly associated with could potentially reduce rates of egg predation. [ABSTRACT FROM AUTHOR]

Salt marsh vegetation zones shift in response to large‐scale environmental changes such as sea‐level rise (SLR) and restoration activities, but it is unclear if they are good indicators of soil nitrogen removal. Our goal was to characterize the relationship between denitrification potential and salt marsh vegetation zones in tidally restored and tidally unrestricted coastal marshes, and to use vegetation zones to extrapolate how SLR may influence high marsh denitrification at the landscape scale. We conducted denitrification enzyme activity assays on sediment collected from three vegetation zones expected to shift in distribution due to SLR and tidal flow restoration across 20 salt marshes in Connecticut, USA (n = 60 sampling plots) during the summer of 2017. We found lower denitrification potential in short‐form Spartina alterniflora zones (mean, 95% CI: 4, 3–6 mg N h−1 m−2) than in S. patens (25, 15–36 mg N h−1 m−2) and Phragmites australis (56, 16–96 mg N h−1 m−2) zones. Vegetation zone was the single best predictor and explained 52% of the variation in denitrification potential; incorporating restoration status and soil characteristics (soil salinity, moisture, and ammonium) did not improve model fit. Because denitrification potential did not differ between tidally restored and unrestricted marshes, we suggest landscape‐scale changes in denitrification after tidal restoration are likely to be associated with shifts in vegetation, rather than differences driven by restoration status. Sea‐level‐rise‐induced hydrologic changes are widely observed to shift high marsh dominated by S. patens to short‐form S. alterniflora. To explore the implications of this shift in dominant high marsh vegetation, we paired our measured mean denitrification potential rates with projections of high marsh loss from SLR. We found that, under low and medium SLR scenarios, predicted losses of denitrification potential due to replacement of S. patens by short‐form S. alterniflora were substantially larger than losses due to reduced high marsh land area alone. Our results suggest that changes in vegetation zones can serve as landscape‐scale predictors of the response of denitrification rates to rapid changes occurring in salt marshes. [ABSTRACT FROM AUTHOR]

1.Intermittent karst lakes are important for forming wetland habitats in otherwise dry karstic landscapes. With characteristic water regimes they are unable to retain water owing to their underground drainage system.2.Many Dinaric intermittent karst lakes (karst poljes) have gone through severe human disturbances in the past, aimed at fluctuating water levels in karst poljes. These measures had the goal of achieving either permanent dry agricultural land or permanent lakes for various purposes. Usually dams were built for water storage to achieve these goals.3.This research aimed to determine the population responses of bird species that are important for conservation, to water level changes on Cerknica Lake (Slovenia), a large Dinaric intermittent karst lake, to inform effective conservation for such systems.4.Water level and vegetation were strong drivers of waterbird diversity and abundance, based on analysis using canonical correspondence analysis and boosted regression trees.5.Water level was critical for the conservation of important bird species. Water and reed specialists (e.g. water rail Rallus aquaticus) require management of refugia in wetlands to create mosaics of water and reedbeds. The formation of nature reserves, quiet zones and habitat restoration is needed for these specialist species. In these areas, mowing should be limited or not present at all.6.Measures dealing with land‐use change and connectivity between habitats, for instance agri‐environmental measures, are more appropriate for rare bird species with wider niche breadths (but still narrower than generalists), e.g. skylark (Alauda arvensis) and linnet (Linaria cannabina). [ABSTRACT FROM AUTHOR]

Two pilot scales of planted vertical flow‐built wetlands in series treating greywater were accomplished in the Tunisian Deaf Help Association (TDHA). The two beds were planted with Phragmites australis with continuous daily flow of 640 L and nominal operating retention duration of 1.25 days. The total suspended solids (TSS) removal efficiency in the first bed was 86.2 ± 10%, and both beds received the same treatment performance for chemical oxygen demand (COD) and biochemical oxygen demand after five days (BOD5). The removal rates for TSS, COD, and BOD5 were 94 ± 13, 86 ± 5.7, and 93 ± 7%, respectively., the ammonium overall removal rate was 71.4 ± 19.1% in both beds, however, it was around 60 ± 9.11% when based on a single bed. The second bed enhanced phosphorus removal twice with a reduction of 52%. In each bed, Escherichia coli clearance ranged from 1.24 to 2.40 logs, respectively, and the total average bacteria population yielded an average of 1.65 log units, equivalent to an efficiency of 46.67%. These results were complemented by polymerase chain reaction‐denaturing gradient gel electrophoresis, showing an overall of biomass reduction of 47 ± 8% with one bed, and of 89 ± 7% with both beds. [ABSTRACT FROM AUTHOR]

Current climate models predict more intense rainstorms and temperature extreme events under future global climate change. Estimation of environmental factors thresholds might provide important information for the common patterns of species distributions and management of wetland ecosystems. The laboratory experiment and the greenhouse experiment examined separately the effects of temperature (10 constant temperature regimes of 8, 10, 12, 14, 16, 19, 22, 26, 30 and 35°C) and flooding depth (10 flooding depth treatments of −15, −10, −5, 0, +5, +10, +15, +20, +25 and +30 cm relative to the substrate surface) on rhizome bud sprouting and establishment of Phragmites australis. Our results revealed that the final sprouting percentage, relative growth rate and ramet height showed hump‐shaped relationships with temperature. Higher temperature led to shorter mean time to sprout, faster sprouting rate and greater ramet survival. The estimated base temperature for rhizome bud sprouting was 5.0 ± 1.27°C. The optimum temperature for rhizome bud sprouting and early growth might be the range of 23–30°C. The final sprouting percentage, relative growth rate and ramet height showed unimodal patterns with flooding depth. The mean time to sprout was increased with deeper flooding depth, while sprouting rate and ramet survival were decreased. The optimum flooding depth for rhizome bud sprouting and early growth might be the range of −7 to 0 cm. Our results will contribute to a better understanding of the influence of climate change on early plant recruitment processes and distribution of P. australis. [ABSTRACT FROM AUTHOR]

Laboratory experiments examined the longitudinal evolution of near‐bed velocity, turbulent kinetic energy (TKE), and net deposition in a model Phragmites australis canopy occupying 1/3 of the channel width. The canopies were constructed from model P. australis with real morphology and a solid volume fraction between 0.003 and 0.018. An exponential model was modified to predict the longitudinal evolution of near‐bed velocity inside the canopy, from which the near‐bed TKE can be predicted. By combining the predicted TKE and a deposition probability, we proposed a model to predict the distribution of net deposition inside the canopy. The predicted velocity, TKE, and deposition were in good agreement with the measurements. Relative to an upstream reference, the net deposition within the canopy was enhanced when two conditions were met: the in‐canopy, near‐bed TKE was smaller than the critical value for resuspension, and resuspension took place in the bare channel. Above a critical vegetation density (defined by a critical solid volume fraction ϕc), the spatially‐averaged deposition inside P. australis surpassed that in the adjacent bare channel. The proposed model provides a way to estimate ϕc. Relative to the upstream reference, deposition inside the canopy was always diminished over some fraction of the flow adjustment distance, Ld (distance from canopy leading edge to fully developed flow). When the canopy length was greater than 0.4 Ld, canopy‐averaged deposition was enhanced relative to the bare channel. Finally, for the same canopy length, differences in plant morphologies did not have a strong impact on the in‐canopy deposition distribution. Key Points: Methods for predicting the evolution of near‐bed velocity, TKE, and net deposition inside a Phragmites australis canopy were proposed and validatedNet deposition in the canopy was enhanced only when TKE was below a critical value and resuspension took place in the bare channelThe proposed model can predict the critical solid volume fraction for enhanced in‐canopy deposition relative to deposition for bare beds [ABSTRACT FROM AUTHOR]

Litter plays an important role in plant invasion. Our previous studies have found that litter had two opposite effects as Spartina alterniflora invading native plant Phragmites australis community. Litter stimulated the growth of S. alterniflora on the edge of the community, while it inhibited the growth in the old community. Accordingly, we hypothesized that litter may play different roles in different stages of plant invasions. We selected three types of communities: P. australis monoculture (PAM), S. alterniflora monoculture (SAM), S. alterniflora–P. australis mixture (SPM) and conducted a comparative study by keeping and removing litter at Chongming Dongtan in the Yangtze River estuary, China. Our results revealed that litter removal significantly increased light intensity in SAM, and enhanced it in SPM, but had no significant influence on it in PAM. The effect of litter on light intensity resulted in a higher chlorophyll content and higher plant height of S. alterniflora monoculture after litter removal, which eventually led to a higher single weight and aboveground biomass for PAM and SAM after litter removal, and to a higher aboveground biomass for S. alterniflora in SPM. Litter removal significantly enhanced the dominance of S. alterniflora relative to P. australis in SPM. We concluded that the effects of invasive plants' litter on the invasion processes depend on the stem density of invasive plants relative to native plants. If an invasive species had a higher plant density, its litter may not have a shelter effect on native species, but could restrict its own growth. [ABSTRACT FROM AUTHOR]

Roseau cane (Phragmites australis (Cav). Trin. ex Steud.) is the dominant plant species of the Mississippi River Delta in Louisiana, USA, and protects the coastline from erosion and storm‐related impacts, maintaining shipping channels and oil infrastructure. Widespread dieback and thinning of P. australis were noted in the Mississippi River Delta in the fall of 2016. Invasive populations of the roseau cane scale (Nipponaclerda biwakoensis Kuwana), which is native to Asia, were found at outbreak levels in the stands. Subsequent research implicated N. biwakoensis in the diebacks. As a safe, cost‐effective and long‐term approach for managing this invasive scale, classical (importation) biological control methods are being considered. As the first step to developing biological control, research evaluating the natural enemies of the N. biwakoensis in the native range is necessary. This study investigated the population dynamics of N. biwakoensis and its associated parasitoids on P. australis in Taiwan from July to November 2019 at five study sites. Scale densities across sites increased over the growing season, peaking in September at 85.77 ± 6.36 scales/stem, which is half as dense as found in Louisiana. Mean parasitism of adult female scales across sites and season was 14.00%, while parasitism on immature scales was lower (3.00%). Four parasitoid wasp species were reared from the scale—Asytymachus lasallei Noyes and Higashiura, Boucekiella depressa Hoffer, Neastymachus japonicus Tachikawa and Aprostocetus sp. Westwood. Neastymachus japonicus was the dominant species parasitizing adult female scales, while A. lasallei was the dominant wasp species parasitizing immature scales. Astymachus lasallei and B. depressa were frequently reared from the same individual host, suggesting multiparasitism or hyperparasitism. Overall, this study provides important information on the identity and role of parasitoids of N. biwakoensis in its native range, which will aid in developing a classical biological control programme for the invasive N. biwakoensis. [ABSTRACT FROM AUTHOR]

Plant–soil feedbacks (PSFs) mediate plant community dynamics and may plausibly facilitate plant invasions. Microbially mediated PSFs are defined by plant effects on soil microbes and subsequent changes in plant performance (responses), both positive and negative. For microbial interactions to benefit invasive plants disproportionately, native and invasive plants must either (1) have different effects on and responses to soil microbial communities or (2) only respond differently to similar microbial communities. In other words, invasive plants do not need to cultivate different microbial communities than natives if they respond differently to them. However, effects and responses are not often explored separately, making it difficult to determine the underlying causes of performance differences. We performed a reciprocal‐transplant PSF experiment with multiple microbial inhibition treatments to determine how native and non‐native lineages of Phragmites australis affect and respond to soil bacteria, fungi, and oomycetes. Non‐native Phragmites is a large, fast‐growing, cosmopolitan invasive plant, whereas the North American native variety is comparatively smaller, slower growing, and typically considered a desirable wetland plant. We identified the effects of each plant lineage on soil microbes using DNA meta‐barcoding and linked plant responses to microbial communities. Both Phragmites lineages displayed equally weak, insignificant PSFs. We found evidence of slight differential effects on microbial community composition, but no significant differential plant responses. Soils conditioned by each lineage differed only slightly in bacterial community composition, but not in fungal composition. Additionally, native and non‐native Phragmites lineages did not significantly differ in their response to similar soil microbial communities. Neither lineage appreciably differed when plant biomass was compared between those grown in sterile and live soils. Targeted microbial inhibitor treatments revealed both lineages were negatively impacted by soil bacteria, but the negative response was stronger in non‐native Phragmites. These observations were opposite of expectations from invasion theory and imply that the success of non‐native Phragmites, relative to the native lineage, does not result from its interaction with soil microorganisms. More broadly, quantifying plant effects on, and responses to soil microbes separately provides detailed and nuanced insight into plant‐microbial interactions and their role in invasions, which could inform management outcomes for invasive plants. [ABSTRACT FROM AUTHOR]

Wetland restoration often involves invasive‐plant suppression to encourage the recovery of native‐dominated vegetation communities. However, assessment of recovery is usually focused only on vegetation, and the response of other critical wetland biota, such as macroinvertebrates, is seldom assessed. We characterized the aquatic, semi‐aquatic, and terrestrial macroinvertebrate communities in remnant, uninvaded marsh to identify restoration targets and compared this to the communities in Phragmites australis‐invaded marsh and in the formerly invaded marsh that was treated with the herbicide glyphosate in 2016 to simultaneously evaluate the effects of invasion and invasive‐species suppression. We sampled invertebrates in 2017 and 2018 to track 2 years following herbicide treatment. The invertebrate community composition was similar between P. australis invaded and remnant marsh, suggesting invasion has little effect on macroinvertebrate community structure. There was also high concordance between the aquatic and emerging‐invertebrate communities in the invaded and uninvaded habitats. In contrast, herbicide‐treated sites had a unique community composition, characterized by very high densities of Chironomidae (Diptera) and low taxa richness and evenness. Herbicide‐treated sites also exhibited low concordance between the aquatic and emerging‐invertebrate communities, potentially attributable to the sparse, emergent‐vegetation cover providing limited substrates for emergence. Herbicide‐based, invasive‐species control resulted in considerable changes to the macroinvertebrate community in freshwater marshes for at least 2 years after treatment, which may have consequences for aquatic food webs and species that rely on macroinvertebrates as prey. [ABSTRACT FROM AUTHOR]

Current theory (e.g., consumer‐controlled theory) predicts that nutrient enrichment typically amplifies herbivory and thereby suppresses the growth and expansion of invasive plants. Herbivores can facilitate plant regrowth in the native community by stimulating complementary growth or ameliorating habitat conditions (e.g., by increasing soil oxygen and nutrient availability), but whether they have similar positive effects on invasive plants, especially under nutrient enrichment, remains unknown. Using a field nitrogen (N)‐enrichment × crab exclusion experiment, we evaluated and compared the effects of both N enrichment and crab herbivory on the growth performance of a global invasive cordgrass, Spartina alterniflora, and a co‐occurring native plant, Phragmites australis. We found that crabs consistently suppressed P. australis by density and aboveground biomass regardless of N enrichment. In contrast, for S. alterniflora, the negative effects of crabs under ambient N were replaced by positive effects under N enrichment, with crabs stimulating complementary increases in density and aboveground biomass. The differing effects between the N treatments were driven by crab burrowing activity, which increased soil N availability, and the nutrient‐use efficiency of S. alterniflora. Our findings revealed that native herbivores can have opposing effects on native and invasive plants, which broadens our understanding of how exotic plants can achieve dominance in a changing world. [ABSTRACT FROM AUTHOR]

Polyploidization and hybridization are very common in natural plant species, and mixed‐ploidy species provide a unique opportunity to study the effects of evolutionary history, local abundance, and ploidy level on the direction and extent of introgression between intraspecific lineages. First, we delimited two morphologically cryptic lineages of Phragmites australis Trin. ex Steud. in temperate China using 11 nuclear microsatellites and two chloroplast DNA fragments with 225 samples from China as well as 11 samples from Oceania and Europe. Our evidence supported that haplotype O and haplotype P were two relatively independent lineages with low and high ploidy levels, respectively; haplotype M might be ancient and could have undergone a complex evolutionary history. Then we examined the lineage divergence and compared the introgression patterns between two major lineages along geographical and abundance gradients with a large number of samples (n = 1067) collected from China. The sympatric coexistence of two lineages in north and northeast China implies an ongoing or potential introgression between them. Cline analysis showed that the level of genetic admixture were significantly correlated with longitude rather than latitude. Our results also suggested that ploidy level could deeply influence the introgression asymmetry, and the effect of the current local abundance on introgression might be covered by the past coexistence time driven by phylogeographic history. Our study draws a baseline for future research on the ecological and evolutionary consequences of migration and introgression of Chinese P. australis under global change. [ABSTRACT FROM AUTHOR]