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Summary Elton's biotic resistance hypothesis predicts that biodiversity can resist the establishment of invasive plants. However, whether and how within‐species diversity mediates the impacts of successfully established invaders is poorly understood, particularly in the face of climate change. We used an experimental system to test the effect of intraspecific diversity of a native foundation species, Scirpus mariqueter, on the soil‐legacy impacts of a global plant invader, Spartina alterniflora, under well‐watered and drought conditions. We found that more diverse populations of the native plant buffered against the negative soil‐legacy impacts of the invader on the native plant. This intraspecific diversity effect was due to a complementarity effect triggered by invader‐shaped soil biota, and emerged in both well‐watered and drought conditions. Compared with the previous finding that intraspecific diversity of the native plant can reduce the performance of the invader through soil biotic feedbacks, this study provides further evidence that it helps to mitigate the negative soil‐derived impacts of the invader. These findings together emphasize the need for management measures that promote and restore native intraspecific diversity in a changing world. [ABSTRACT FROM AUTHOR]

Tidal marshes at the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island (PI) are part of a large‐scale restoration project to replace lost island habitat in Chesapeake Bay, United States. However, observations of Spartina alterniflora die‐back prompted questions about the impact on genetic diversity and resilience of restored versus natural marshes, leading to an investigation of genetic diversity and population structure. Transects were established across three distinct restored marshes with different ages and histories of die‐back and across two local, non‐restored native marshes. Plants were genotyped at eight microsatellite markers to examine metrics of genetic diversity, population structure, and clonality. Allelic richness but not heterozygosity was higher in restored marshes compared to reference marshes, which showed significantly higher clonality and spatial genetic autocorrelation. Restored marsh areas experiencing die‐back had slightly lower multilocus diversity indices than non‐die back areas in two third cases, but not a third comparison. Significant genetic differentiation was observed between the native and restored marshes (mean GST approximately 0.06), which reflects the approximately 100 km distance between native marshes and restored seed source in New Jersey. Overall, die‐back in restored marshes did not substantially affect genetic diversity or composition, but substantial differences in diversity were observed between restored and native marshes. Reduced clonal diversity in mature, native marshes may be a function of their greater age, as has been reported elsewhere. Future monitoring of neutral genetic diversity in PI marshes will be useful for understanding longer‐term patterns of genetic change and diversity in planted, restored marshes. [ABSTRACT FROM AUTHOR]

Large grazers modify vegetated ecosystems and are increasingly viewed as keystone species in trophic rewilding schemes. Yet, as their ecosystem influences are context‐dependent, a crucial challenge is identifying where grazers sustain, versus undermine, important ecosystem properties and their resilience.Previous work in diverse European saltmarshes found that, despite changing plant and invertebrate community structure, grazers do not suppress below‐ground properties, including soil organic carbon (SOC). We hypothesised that, in contrast, eastern US saltmarshes would be sensitive to large grazers as extensive areas are dominated by a single grass, Spartina alterniflora. We predicted that grazers would reduce above‐ and below‐ground Spartina biomass, suppress invertebrate densities, shift soil texture and ultimately reduce SOC concentration.We tested our hypotheses using a replicated 51‐month large grazer (horse) exclusion experiment in Georgia, coupled with observations of 14 long‐term grazed sites, spanning ~1000 km of the eastern US coast.Grazer exclusion quickly led to increased Spartina height, cover and flowering, and increased snail density. Changes in vegetation structure were reflected in modified soil texture (reduced sand, increased clay) and elevated root biomass, yet we found no response of SOC. Large grazer exclusion also reduced drought‐associated vegetation die‐off.We also observed vegetation shifts in sites along the eastern US seaboard where grazing has occurred for hundreds of years. Unlike in the exclusion experiment, long‐term grazing was associated with reduced SOC. A structural equation model implicated grazing by revealing reduced stem height as a key driver of reduced soil organic carbon.Synthesis: These results illustrate the context dependency of large grazer impacts on ecosystem properties in coastal wetlands. In contrast to well‐studied European marshes, eastern US marshes are dominated and structured by a single foundational grass species resulting in vegetation and soil properties being more sensitive to grazing. Coastal systems characterised by a single foundation species might be inherently vulnerable to large grazers and lack resilience in the face of other disturbances, underlining that frameworks to explain and predict large grazer impacts must account for geographic variation in ecosystem structure. [ABSTRACT FROM AUTHOR]

Parasites can alter the traits or densities of mutualistic partners, potentially destabilizing mutualistic associations that underpin the structure, functioning, and stability of entire ecosystems. Despite the potentially wide‐ranging consequences of such disruptions, no studies have directly manipulated parasite prevalence and/or intensity in a mutualistic partner, nor quantified the resulting community‐level effects. Here, we investigated the effects of a common trematode parasite (Cercaria opaca) on the strength of a keystone facultative mutualism in western Atlantic salt marshes between the foundational marsh cordgrass, Spartina alterniflora, and the ribbed mussel, Geukensia demissa. Cordgrass increases mussel survivorship and growth through shading, while mussels enhance cordgrass growth by producing nutrient‐rich biodeposits. This mutualistic association also creates conditions that enhance biodiversity and ecosystem functioning, and mediates the ability of foundational plants to resist and recover from extreme drought. We used lab and field assays to show how increasing infection with trematode metacercariae negatively influenced mussel biodeposit production, as well as the strength of mussel shells and byssal attachments. By conducting a field manipulation using experimentally infected mussels, we demonstrated that the mutualistic benefits of mussels to cordgrass growth decreased with increasing trematode infection intensity—a pattern likely generated by reduced mussel biodeposition and enhanced mortality. Additionally, increasing parasite loads in mussels led to predictable decreases in the abundances of benthic invertebrates, as well as in key ecosystem characteristics and process rates (i.e., redox potential and sediment accretion). Finally, a survey of five North Carolina salt marshes demonstrated that infection with C. opaca was most common in mussels in areas experiencing cordgrass die‐off due to drought, and that infection intensity decreased with distance from die‐off areas. Because the mussel–cordgrass mutualism underpins marsh ecosystem resilience to drought‐associated die‐off, our results suggest that parasitism may depress recovery from these disturbances. Although this is the first experimental demonstration of parasites indirectly altering community structure and functioning by undermining an ecologically influential mutualism, this type of relationship could be common in nature, given that parasites frequently infect influential mutualists. [ABSTRACT FROM AUTHOR]

The development of a cost-effective and environment-friendly conversion method to overcome the recalcitrance of biomass is a challenging task for enhancing the value-added potential of lignocellulosic compounds. In this study, a photo-enzyme composite catalyst by immobilizing laccase on Fe 3 O 4 /TiO 2 (denoted as LC-Fe 3 O 4 /TiO 2) was applied to the pretreatment and enzymatic saccharification of Spartina alterniflora Loisel (SAL) under the action of alternating light/dark cycles. The effect of the pretreatment temperature, pretreatment time, LC-Fe 3 O 4 /TiO 2 concentration, mass concentration of straw particles, and hydrolysis time on delignification efficiency and reducing sugar yield was investigated by a central composite design (CCD). Under the selected conditions (48 ℃, pretreatment time of 70 min, LC-Fe 3 O 4 /TiO 2 concentration of 4.9 mg/mL, mass concentration of straw particles of 22 % (w/v), hydrolysis time of 55 h), 92.53 % delignification and 129.85 mg/g reducing sugar yield were achieved. The enzymatic hydrolysis efficiency was higher compared to conventional methods. Moreover, the LC-Fe 3 O 4 /TiO 2 showed good recyclability and reusability. Developed LC-Fe 3 O 4 /TiO 2 particles have a high potential for use in biomass utilization. [Display omitted] • Laccase-Fe 3 O 4 /TiO 2 integrated catalyst (LC-Fe 3 O 4 /TiO 2) is first synthesized. • Effects of LC-Fe 3 O 4 /TiO 2 on pretreatment and saccharification is studied. • LC-Fe 3 O 4 /TiO 2 can enhance sugar yield under the alternation of light and dark. • LC-Fe 3 O 4 /TiO 2 could be efficiently reused up to 3 cycles. [ABSTRACT FROM AUTHOR]

In recent years, the Chinese government has implemented a series of initiatives with the objective of eradicating the invasive Spartina alterniflora along the entire coastline. This has given rise to concerns about the potential for subsequent coastal erosion and salt marsh shrinkage. This study introduces a novel contribution in the form of a model‐based analysis, grounded in fieldwork from the Yellow River Delta, which assesses the potential of native Suaeda salsa as an alternative for coastal protection. Our approach is distinctive in that it not only compares the flow velocity reduction effects of S. alterniflora and S. salsa, but also evaluates the efficacy of three distinct planting patterns in managing tidal dynamics. In this study, we present a significant finding: while both species can mitigate tidal flow velocity, S. alterniflora shows superior performance, which represents a novel point of discussion in the field of coastal wetland management. Furthermore, our research indicates that dense aggregated planting patterns are particularly effective during storm surges, offering a strategic insight for future ecological engineering. However, we recognize the potential limitations of our approach, including the need for continuous management to control the spread of S. alterniflora and the necessity for further research to optimize the restoration potential of S. salsa under varying tidal conditions. Our findings highlight the importance of a balanced approach, suggesting the retention of a portion of S. alterniflora while also emphasizing the strategic planting of S. salsa in high‐density configurations to enhance coastal resilience. [ABSTRACT FROM AUTHOR]

A network of 15 Surface Elevation Tables (SETs) at North Inlet estuary, South Carolina, has been monitored on annual or monthly time scales beginning from 1990 to 1996 and continuing through 2022. Of 73 time series in control plots, 12 had elevation gains equal to or exceeding the local rate of sea-level rise (SLR, 0.34 cm/year). Rising marsh elevation in North Inlet is dominated by organic production and, we hypothesize, is proportional to net ecosystem production. The rate of elevation gain was 0.47 cm/year in plots experimentally fertilized for 10 years with N&P compared to nearby control plots that have gained 0.1 cm/year in 26 years. The excess gains and losses of elevation in fertilized plots were accounted for by changes in belowground biomass and turnover. This is supported by bioassay experiments in marsh organs where at age 2 the belowground biomass of fertilized S. alterniflora plants was increasing by 1,994 g m−2 year−1, which added a growth premium of 2.4 cm/year to elevation gain. This was contrasted with the net belowground growth of 746 g m−2 year−1 in controls, which can add 0.89 cm/year to elevation. Root biomass density was greater in the fertilized bioassay treatments than in controls, plateauing at about 1,374 g m−2 and 472 g m−2, respectively. Growth of belowground biomass was dominated by rhizomes, which grew to 3,648 g m−2 in the fertilized treatments after 3 years and 1,439 g m−2 in the control treatments after 5 years. Depositional wetlands are limited by an exogenous supply of mineral sediment, whereas marshes like North Inlet could be classified as autonomous because they depend on in situ organic production to maintain elevation. Autonomous wetlands are more vulnerable to SLR because their elevation gains are constrained ultimately by photosynthetic efficiency. [ABSTRACT FROM AUTHOR]

Tidal marshes in the Chesapeake Bay are vulnerable to the accelerating rate of sea-level rise (SLR) and subsidence. Restored and created marshes face the same risks as natural marshes, and their resilience to SLR may depend upon appropriate design and implementation. Here, the Coastal Wetland Equilibrium Model (CWEM) was used to assess the resilience of tidal marshes at the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island (PI) in mid-Chesapeake Bay, MD, where dredged material from navigation channels is being used to create new tidal marshes planted with Spartina alterniflora in the low marsh and S. patens in the high marsh. The site is microtidal with low inorganic sediment inputs, where the rate of marsh elevation change is dominated by the production of organic matter and, therefore, is proportional to net ecosystem production (NEP). The model demonstrated the importance of marsh development for surface elevation gain. In created marshes, the buildout of belowground biomass adds volume and results in faster growth of marsh elevation, but the gains slow as the marsh matures. Elevation gain is the lessor of the recalcitrant fraction of NEP sequestered in sediment or the rate of increase in accommodation space. Marshes can keep up with and fill accommodation space with sequestered NEP up to a tipping point determined by the rate of SLR. The PI low marsh platform was forecasted to drown in about 43 years after construction at the current rate of SLR. Marsh loss can be mitigated by periodic thin layer placement (TLP) of sediment. CWEM was used to simulate PI marsh responses to different TLP strategies and showed that there is an optimal design that will maximize carbon sequestration and resilience depending on the trajectory of mean sea level. [ABSTRACT FROM AUTHOR]

Coastal biological invasions pose a wide-reaching threat to various ecosystems, affecting both vegetation and herbivores in native communities. Although herbivores often exert strong top-down control on vegetation, the impact of invasive species on consumers that strongly regulate native species in invaded ecosystems remains unclear. Therefore, through field surveys and feeding preference experiments, this study examined the effects of the invasive Spartina alterniflora Loisel. (hereafter, Spartina) on the native moth Laelia coenosa Hübner (hereafter, Laelia), a notorious pest that has been documented to cause significant damage to native Phragmites australis (Cav.) Trin. ex Steud. (hereafter, Phragmites) marshes in coastal wetlands of China. Field surveys showed that Laelia larvae were more abundant and had higher grazing rates in Phragmites than in Spartina marshes in summer, but these patterns reversed in autumn. Feeding experiments consistently showed that the dietary preference of Laelia larvae switched from Phragmites in summer to Spartina in autumn, likely because Spartina has a longer growing season and relatively higher nutritional quality than Phragmites in autumn. Thus, by providing shelters (i.e., dietary sources and habitats) during unfavorable seasons, Spartina invasions may facilitate this insect pest Laelia and potentially amplify its damage to native wetland vegetation. Our work reveals a novel, indirect mechanism of coastal invasion impacts and highlights the importance of incorporating seasonal variation in plant-herbivore interactions. [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]

Background: The planting of mangroves is extensively used to control the invasive plant Spartina alterniflora in coastal wetlands. Different plant species release diverse sets of small organic compounds that affect rhizosphere conditions and support high levels of microbial activity. The root-associated microbial community is crucial for plant health and soil nutrient cycling, and for maintaining the stability of the wetland ecosystem. Methods: High-throughput sequencing was used to assess the structure and function of the soil bacterial communities in mudflat soil and in the rhizosphere soils of S. alterniflora, mangroves, and native plants in the Oujiang estuarine wetland, China. A distance-based redundancy analysis (based on Bray–Curtis metrics) was used to identify key soil factors driving bacterial community structure. Results: S. alterniflora invasion and subsequent mangrove afforestation led to the formation of distinct bacterial communities. The main soil factors driving the structure of bacterial communities were electrical conductivity (EC), available potassium (AK), available phosphorus (AP), and organic matter (OM). S. alterniflora obviously increased EC, OM, available nitrogen (AN), and NO3−-N contents, and consequently attracted copiotrophic Bacteroidates to conduct invasion in the coastal areas. Mangroves, especially Kandelia obovata, were suitable pioneer species for restoration and recruited beneficial Desulfobacterota and Bacilli to the rhizosphere. These conditions ultimately increased the contents of AP, available sulfur (AS), and AN in soil. The native plant species Carex scabrifolia and Suaeda glauca affected coastal saline soil primarily by decreasing the EC, rather than by increasing nutrient contents. The predicted functions of bacterial communities in rhizosphere soils were related to active catabolism, whereas those of the bacterial community in mudflat soil were related to synthesis and resistance to environmental factors. Conclusions: Ecological restoration using K. obovata has effectively improved a degraded coastal wetland mainly through increasing phosphorus availability and promoting the succession of the microbial community. [ABSTRACT FROM AUTHOR]

Smooth cordgrass (Spartina alterniflora) is a native salt marsh plant along the Atlantic coast but has become an invasive species in coastal regions in China, as well as other areas. Utilizing it for resources has become a control measure in reducing the spread of S. alterniflora. This study assesses the nutritional and phytochemical properties of the edible stems of S. alterniflora collected from three locations in Fujian province, China. The tender stems of S. alterniflora exhibit a rich nutritional profile, with high levels of protein, carbohydrates, and fats, and significant amounts of essential vitamins, minerals, and antioxidants, indicating their potential as a nutritious addition to the diet or forage. In addition, the levels of potential contaminants, including nitrate, nitrite, cadmium, lead, and chromium, are below the established safe thresholds for consumption. Our results provide valuable information for the sustainable utilization of S. alterniflora resources and will contribute to the integrated control of S. alterniflora. [ABSTRACT FROM AUTHOR]

Mangroves are one of the world's most productive and ecologically important ecosystems, and they are threatened by the widespread invasion of Spartina alterniflora Loisel in China. As few studies have examined the spatial pattern differences of S. alterniflora invasion and the nearby mangroves in different latitudes, we chose the Zhangjiang Estuary and the Dandou Sea, two representative mangrove–salt marsh ecotones in the north and south of the Tropic of Cancer, as the study areas for comparison. The object-based image analysis and visual interpretation methods were combined to construct fine-scale mangrove and S. alterniflora maps using high-resolution satellite imagery from 2005 to 2019. We applied spatial analysis, centroid migration, and landscape indexes to analyze the spatio–temporal distribution changes of mangroves and S. alterniflora in these two ecotones over time. We used the landscape expansion index to investigate the S. alterniflora invasion process and expansion patterns. The annual change rates of mangrove and S. alterniflora areas in the Zhangjiang Estuary showed a continuous growth trend. However, the mangrove areas in the Dandou Sea showed a fluctuating trend of increasing, decreasing, and then increasing again, while S. alterniflora areas kept rising from 2005 to 2019. Spartina alterniflora showed larger annual change rates compared with mangroves, indicating rapid S. alterniflora invasion in the intertidal zones. The opposite centroid migration directions of mangroves and S. alterniflora and the decreasing distances between the mangrove and S. alterniflora centroids indirectly revealed the fierce competition between mangroves and S. alterniflora for habitat resources. Both regions saw a decrease in mangrove patch integrality and connectivity. The integrality of mangrove patches in the Zhangjiang Estuary was always higher than those in the Dandou Sea. We observed the growth stage (2011–2014) and outbreak stage (2014–2019) of S. alterniflora expansion in the Zhangjiang Estuary and the outbreak stage (2005–2009) and plateau stage (2009–2019) of S. alterniflora expansion in the Dandou Sea. The expansion pattern of S. alterniflora varies in time and place. Since the expansion of S. alterniflora in the outbreak stage is rapid, with a large annual change rate, early warning of S. alterniflora invasion is quite important for the efficient and economical removal of the invasive plant. Continuous and accurate monitoring of S. alterniflora is highly necessary and beneficial for the scientific management and sustainable development of coastal wetlands. [ABSTRACT FROM AUTHOR]

Being an alien species, Spartina alterniflora has occupied the living space of native animals and plants, causing irreversible damage to the environment. Converting Spartina alterniflora into carbon or its derivatives offers a valuable solution to manage both invasive biomass and an energy shortage. Herein, through a simple activation process, we successfully prepared Spartina alterniflora-derived carbon (SAC) and its N-doped derivative SANC, and used them as metal-free catalysts for an oxygen reduction reaction (ORR). SAC exhibits good electrochemical performance and holds significant potential in catalysis. After N-doping by melamine as a nitrogen source, electronegativity is redistributed in SANC, leading to enhanced performance (a half-wave potential of 0.716 V vs. RHE, and a four-electron transfer pathway with a H2O2 yield of only 2.05%). This work presents a straightforward and cost-effective approach to the usage of obsolete invasive biomass and shows great potential in energy generation. [ABSTRACT FROM AUTHOR]

Summary: Spartina alterniflora is an exo‐recretohalophyte Poaceae species that is able to grow well in seashore, but the genomic basis underlying its adaptation to salt tolerance remains unknown. Here, we report a high‐quality, chromosome‐level genome assembly of S. alterniflora constructed through PacBio HiFi sequencing, combined with high‐throughput chromosome conformation capture (Hi‐C) technology and Illumina‐based transcriptomic analyses. The final 1.58 Gb genome assembly has a contig N50 size of 46.74 Mb. Phylogenetic analysis suggests that S. alterniflora diverged from Zoysia japonica approximately 21.72 million years ago (MYA). Moreover, whole‐genome duplication (WGD) events in S. alterniflora appear to have expanded gene families and transcription factors relevant to salt tolerance and adaptation to saline environments. Comparative genomics analyses identified numerous species‐specific genes, significantly expanded genes and positively selected genes that are enriched for 'ion transport' and 'response to salt stress'. RNA‐seq analysis identified several ion transporter genes including the high‐affinity K+ transporters (HKTs), SaHKT1;2, SaHKT1;3 and SaHKT1;8, and high copy number of Salt Overly Sensitive (SOS) up‐regulated under high salt conditions, and the overexpression of SaHKT2;4 in Arabidopsis thaliana conferred salt tolerance to the plant, suggesting specialized roles for S. alterniflora to adapt to saline environments. Integrated metabolomics and transcriptomics analyses revealed that salt stress activate glutathione metabolism, with differential expressions of several genes such as γ‐ECS, GSH‐S, GPX, GST and PCS in the glutathione metabolism. This study suggests several adaptive mechanisms that could contribute our understanding of evolutional basis of the halophyte. [ABSTRACT FROM AUTHOR]

Salinity is one of the main limiting factors driving the expansion of Spartina alterniflora by affecting plant functioning. Comparative studies of plant leaves, under 0 (T0), 5 (T5), 10 (T10), and 20 g/kg (T20) soil salinity, were carried out. Results showed that soil salinity significantly affected most leaf traits of S. alterniflora. Total and live leaf numbers first increased and then decreased with increasing soil salinity. Leaf morphology in T5 were substantially larger than another three treatments, and the ratio of leaf length to width considerably decreased with increasing soil salinity. As the soil salinity increased, leaf dry mass and leaf dry matter content (LDMC) displayed a pattern similar to total leaf number. Leaf mass traits indicated that while a more efficient nutrient conservation strategy was adopted in T10, S. alterniflora rapidly produced biomass in T0. Strong correlations were observed between leaf morphological and mass traits except for some parts of LDMC. The confidence ellipses of leaf traits indicated significant differences in leaf traits of the four treatments. We believe that insights into the aforementioned aspects can contribute to a better understanding of the responses of leaf traits of S. alterniflora and provide valuable information about its adaptation strategy. [ABSTRACT FROM AUTHOR]

Salt marshes have ecological and economic value, but shoreline development, the increasing rate of sea-level rise, and other human impacts have caused significant loss of salt marshes. As a result, restoration of these ecosystems is widespread. For restoration and management to be effective, it is imperative to improve our understanding of marsh-building plants that serve as the ecological foundation of these habitats. Given the observed differences in characteristics between populations of smooth cordgrass, Spartina alterniflora, restoration plantings may impact the biodiversity and resilience of restored ecosystems. Understanding differences in the structural and functional outcomes of active planting of restoration sites will enable the long-term success of restoration efforts to be improved. Natural and restored salt marshes in Long Island Sound were studied in 2021–2022 for S. alterniflora genetics, biomass, stem morphology, and faunal community composition. The average genotypic diversity of S. alterniflora was more than 4 times higher in restored than in natural marshes, and differentiation between each restored site and natural sites decreased with time. No difference was observed in live S. alterniflora belowground biomass; however, mean dead belowground biomass in natural marshes was more than 3 times greater than in restored marshes. Marsh platform invertebrates differed between the restored and natural sites, with natural marsh edge habitats having 9 times higher density of Geukensia demissa and 3 times as many crab burrows than in restored marshes, but there was no detected difference in species richness or abundance of nekton at high tide. With restoration practitioners seeking resilient, self-sustaining ecosystems, it is important to evaluate whether restored marsh characteristics are consistent with those goals and modify restoration planning accordingly to incorporate genetics, structure, and function. [ABSTRACT FROM AUTHOR]

Living shorelines (LS) stabilize eroding banks while providing more natural habitats and creating a gentler slope for enhanced migration of flora and fauna migration as sea levels rise. Typical LS practices include using several different materials, including oyster shell bags, to stabilize shorelines and planting marsh grasses. However, incorporating other important species interactions among marsh organisms can improve LS function and stability. For example, ribbed mussels, Guekensia demissa, benefit marsh plants by adding nutrients and stabilizing sediments. Unfortunately, mussels are not typically included in management and restoration practices. In this study, the objective was to investigate whether ribbed mussels facilitate marsh grass growth at a LS site in the southeastern US. We conducted field surveys for mussel abundance and recruitment, and a manipulative in situ experiment at an established LS site in Georgia to explore the impacts of adding mussels. Although mussel treatment did not have a significant effect on Spartina alterniflora metrics (i.e., density, height, biomass), Spartina plots with high mussel density exhibited ~300% increase in biomass relative to the start of the experiment, while plots without mussels only increased by ~100%. Some of the variability within treatments can be explained by high and sustained mussel mortality throughout the experimental period, likely due to predation, that impacted the actual mussel densities in our plots. We found that Spartina height, density, and biomass exhibited significant positive relationships with mussel biomass. Thus, ribbed mussels may be useful in living shorelines restoration projects if they are planted in sufficient densities, in aggregations, and/or with protective devices. [ABSTRACT FROM AUTHOR]

Foundation species support highly productive and valuable ecosystems, but anthropogenic disturbances and environmental changes are increasingly causing foundation species shifts, where one foundation species replaces another. The consequences of foundation shifts are not well understood, as there is limited research on the equivalency of different foundation species and the functions they support. Here, we provide insight into community-level consequences of foundation shifts in the Gulf of Mexico, where the typical marsh foundation species (Spartina alterniflora) is being replaced with a mangrove foundation species (Avicennia germinans), forcing marsh fauna to rely on Avicennia for foundational support. We evaluated the interactions of two common and ecologically valuable basal consumers, fiddler crabs (Uca spp.) and marsh periwinkle snails (Littoraria irrorata), with both foundation species across sites with different levels of mangrove encroachment. By investigating both physical support, measured as habitat association and co-occurrence, and trophic support, as basal resource diet contributions, we found that Avicennia can physically replace Spartina for some consumers, but is not providing equivalent trophic support. Uca and Littoraria commonly occupy encroached sites and associate with mangroves but incorporate almost no mangrove plant matter into their diets. The ultimate consequences of a foundation shift in the case of mangrove encroachment may include shifting energy flows and resource use and decreased populations of basal consumers. Looking at interactions with foundation species from multiple perspectives is necessary to obtain a complete picture of the effects that foundational shifts are having, especially as such shifts are becoming increasingly common. [ABSTRACT FROM AUTHOR]

【Objective】This study aimed to assess the effectiveness of imazapyr in controlling Spartina alterniflora and to analyze its impact on soil ecosystem, so as to provide theoretical basis for scientific control of S. alterniflora.【Method】In the typical S. alterniflora invasion area in coastal Guangxi, a control sample plot L0 and three experimental sample plots (L1-L3) treated with different concentrations of imazapyr(3000, 3750, 4500 g/hm²)were established. Soil samples at depths of 0-20 cm were collected at 1, 30, 60 and 120 d of the experiment. The contents of total organic carbon (TOC), nitrogen (N), phosphorus (P), potassium (K) were analyzed. Meanwhile, the growth status and control rate of S. alterniflora were recorded.【Result】The growth of S. alterniflora was greatly inhibited by spraying with imazapyr, and the elimination efficiency were 54.35%, 92.99% and 100.00% after 30, 60 and 120 d, respectively. However, secondary invasion occurred in the experimental area. The application of imazapyr caused the death of S. alterniflora, significantly reduced the TOC content of soil in the experimental plots (P＜0.05), with surface soil showing a clear trend of carbon loss. The application of imazapyr had no significant effect on soil TN content (P＞0.05), but significantly increased the contents of ammoniacal nitrogen (NH4+-N), total phosphorus (TP), available phosphorus (AP), total potassium (TK) and available potassium (AK), and significantly decreased nitrate nitrogen(NO3--N) content. There was no significant difference in nutrient content among the experimental plots.【Conclusion】Imazapyr shows a high control rate of S. alterniflora, however, while effectively controlling S. alterniflora, the application of imazapyr resulted in soil carbon loss indirectly, but promoted the accumulation of soil nutrients. Therefore, the global control model should be adopted in the control project to avoid the secondary invasion of S. alterniflora, and it is recommended to plant native vegetation to occupy the ecological niche of the original S. alterniflora, so as to improve the soil carbon sequestering capacity and the stability of the soil ecosystem. [ABSTRACT FROM AUTHOR]

Invasive Spartina alterniflora (S. alterniflora) has significant impacts on sediment biogeochemical cycling in the tidal wetlands of estuaries and coasts. However, the impact of exotic Spartina alterniflora invasion on greenhouse gases (GHGs) production dynamics in sediments remain limited. Here, we investigated the dynamics of sediment physicochemical properties, GHGs production rates, and microbial gene abundances in a native Cyperus malacensis habitat and three invasive S. alterniflora habitats (6-, 10-, and 14-year) in the Minjiang River Estuary, China. The methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) production rates varied both spatially and seasonally, while microbial gene abundances (bacterial and fungal gene abundances) and organic matter (TOC and TN) only varied spatially. GHGs production rates were also characterized by higher values in surface sediment (0-10 cm) compared to subsurface sediment (10-20 cm) and by seasonal variations with higher values in summer than in winter. S. alterniflora invasion can significantly increase CH4 and CO2 production rates, organic matter, and microbial gene abundances (p < 0.05). Temperature, organic matter and microbial gene abundances were the most dominating factor controlling the spatio-temporal variations of CH4 and CO2 production rates. Overall, our findings highlighted the significant role of S. alterniflora invasion in regulating GHGs production rates in coastal wetland sediments and provided fundamental data for estimating GHGs emissions and carbon sequestration in the complex tidal wetlands. [ABSTRACT FROM AUTHOR]

In the process of applying exotic plants to wetland ecological restoration, insufficiently evaluated alien species may exhibit strong competitiveness and fecundity. Once introduced, they can displace native flora, disrupt the original ecological balance, diminish biodiversity, and even induce ecosystem dysfunction. Furthermore, exotic plants have the potential to alter soil microbial community structure, including the composition and activity of beneficial symbiotic microorganisms such as arbuscular mycorrhizal fungi (AMF), thereby impacting soil nutrient cycling and interplant nutrient competition. Here, we conducted three consecutive years of sampling experiments to investigate the succession of AMF communities associated with the invasive plant Spartina alterniflora along an initial introduction chronosequence, and to identify the key environmental factors influencing its response to S. alterniflora invasion. Our findings reveal that early-stage invasion by S. alterniflora alters the composition of soil AMF communities with unclassified_c__Glomeromycetes and Glomus-viscosum-VTX00063 consistently dominating. Additionally, as the duration of introduction increases, the diversity of rhizosphere soil AMF significantly decreases, while its evenness remains relatively stable. It's indicated that soil ω, AN, AK and N/P ratio were the main influencing factors of the integral AMF community. Notably, soil available phosphorus (AP) emerges as a positive influence on the important AMF taxa. The results confirm the mutual feedback effect between the invasion of the perennial herb S. alterniflora and AMF, in which specific AMF assist in nutrient absorption to promote S. alterniflora growth, potentially facilitating its rapid and successful invasion of new habitats. Given the likely differential effects of AMF communities on various plant species, our findings could contribute to anticipating future AMF-mediated effects during the introduction of alien plants. [ABSTRACT FROM AUTHOR]

Bivalves are becoming an increasingly popular tool to counteract eutrophication, particularly in vegetated coastal ecosystems where synergistic interactions between bivalves and plants can govern important N sequestration pathways. In turn, new calls to evaluate how bivalve densities modify N pools and processes across multiple scales have surfaced.Ribbed mussels, Geukensia demissa, and their relationship with smooth cordgrass present a classic demonstration of positive bivalve‐plant interactions and offer a useful model for assessing density dependence. We measure porewater ammonium concentrations, N stable isotope signatures in cordgrass tissue, and sediment N fluxes in mussel aggregations and in cordgrass‐only plots across a southeastern U.S. salt marsh.In addition to measuring the effect of mussel presence, we evaluate mussel density dependence through a multiscale approach. At the patch scale, we quantify mussel density effects within their aggregations (individuals m−2) while at a larger landscape scale, we quantify mussel density effects on the cordgrass‐only areas they neighbour (individuals ~30 m−2).Porewater ammonium concentrations were halved in mussel biodeposits relative to sediments in cordgrass‐only areas and negatively related to mussel density within aggregations. Leaf clip ẟ15N signatures were nearly 2‰ higher in cordgrass growing among mussel aggregations and increased with increasing patch mussel density. Microcosm incubations showed that mussels enhanced N2 flux (i.e., nitrogen removal) and DIN flux (i.e., N regeneration) into the water column, where only nitrogen removal increased with increasing patch‐scale mussel density. Across the marsh landscape, mussel coverage drove ammonium accumulation and N2 flux in sediments.Synthesis. Our results suggest that, at the patch scale, mussels stimulate the microbial metabolism of N, the assimilation of this bioavailable N by cordgrass, and nitrogen removal in a positive, density‐dependent manner. Tidal currents redistribute mussel biodeposits from mussel aggregations to surrounding areas, influencing biogeochemical transformations at scales beyond their physical footprint. We emphasize that the N regeneration potential of bivalve populations is a significant metric contributing to their mitigation potential and that bivalve density effects may be non‐linear, vary across patch to ecosystem scales, and have differing implications for the plants with which they interact. [ABSTRACT FROM AUTHOR]

Background and aims: Nitrogen (N) mineralization and immobilization are two important N biogeochemical processes in estuarine and coastal sediments. However, the changes of those two processes in sediment following Spartina alterniflora (S. alterniflora) invasions into mangrove wetlands under aerobic and anaerobic conditions remain limited. Methods: We used a 15N stable isotope dilution technique to investigate sediment gross N mineralization (GNM) and NH4+ immobilization (GAI) under aerobic and anaerobic conditions in mangrove communities, mangrove communities mixed with S. alterniflora, and pure S. alterniflora communities in the Zhangjiang Estuary, China. Results: GNM and GAI rates varied spatially and seasonally. Summer N mineralization and immobilization rates under aerobic and anaerobic conditions were both significantly higher than those in winter, and the high rates were observed mainly in mangrove sediments and decreased with S. alterniflora invasion. GNM rates in aerobic conditions were significantly higher than those in anaerobic conditions, while GAI rates in aerobic conditions were less than those in anaerobic conditions. GNM and GAI rates were related closely to temperature, water content and organic matter. S. alterniflora invasion can weaken GNM and GAI rates by reducing organic matter accumulation, and S. alterniflora invasion could have reduced sediment N mineralization (2.10 × 103 t N yr−1) and immobilization (1.46 × 103 t N yr−1) in mangrove wetlands of China from 1980 to 2020. Conclusions: Our results highlight the importance of S. alterniflora invasion and hydrological conditions in controlling N mineralization and immobilization processes in mangrove sediments and are essential for the evaluation of N-balance in this N-limited ecosystem. [ABSTRACT FROM AUTHOR]

Spartina alterniflora has rapidly and extensively encroached on China's coastline over the past decades. Among the coastal areas invaded by S. alterniflora , at most 93% are mudflats. However, the effect of S. alterniflora invasion on soil organic carbon (SOC) stocks of coastal mudflats has not been systematically studied on a national scale. Here, we quantified the nationwide changes in SOC stocks in coastal mudflats associated with S. alterniflora invasion between 1990 and 2020. We found that S. alterniflora invasion significantly enhanced SOC stocks in coastal China. Nonetheless, the benefit of S. alterniflora invasion of coastal SOC stock may be weakened by continuing human intervention. We found that S. alterniflora invading mudflats added 2.3 Tg SOC stocks to China's coastal blue carbon, while 1.78 Tg SOC stocks were lost mainly due to human activities, resulted in a net SOC stock gain of 0.52 Tg C. These findings overturned the traditionally thought that S. alterniflora invasion would reduce ecosystem services by highlighting that the historical invasion of S. alterniflora has broadly and consistently enhanced blue carbon stock in coastal China. [ABSTRACT FROM AUTHOR]

The evolution of coastal wetlands is a complex process which is difficult to forecast, made more complicated by the addition of changing climatic conditions. Here, long term ecological and geomorphological data are coupled to geotechnical measurements at a coastal wetland in North Inlet estuary, South Carolina. The coupled methodology is presented and discussed in context of understanding coastal wetland system evolution in a changing climate. Specifically, the root shear strength of Spartina alterniflora across a range of elevations was investigated using a cone penetrometer test. Elevation, shear strength, and biomass are shown to be critically interconnected. Root strength was shown to decrease with increased inundation time and decreased elevation (i.e., mudflats). Conversely, the data set illustrates the importance of maintaining key elevation ranges in relation to sea‐level to optimize wetland resilience. Plain Language Summary: Coastal wetlands are under increased stress from the effects of climate change. We set out to incorporate measurements from multiple disciplines to better understand how these wetlands evolve under these conditions. The strength (resilience) of the wetlands is directly related to the elevation and vegetation of the wetland. Understanding the relationships we present will assist coastal managers make decisions to better protect coastal wetlands. Key Points: Ecological, geomorphological, and geotechnical properties of wetlands are critically interconnectedCoupling of interdisciplinary data sets is required for prediction of wetland evolution in a changing climate [ABSTRACT FROM AUTHOR]

Plant's life history can evolve in response to variation in climate spatio‐temporally, but numerous multiple‐species studies overlook species‐specific (especially a foundation species) ecological effects and genetic underpinnings. For a species to successfully invade a region, likely to become a foundation species, life‐history variation of invasive plants exerts considerable ecological and evolutionary impacts on invaded ecosystems. We examined how an invasive foundation plant, Spartina alterniflora, varied in its life history along latitudinal gradient using a common gardens experiment. Two common gardens were located at range boundary in tropical zone and main distribution area of S. alterniflora in temperate zone in China. Within each population/garden, we measured the onset time of three successive phenological stages constituting the reproductive phase and a fitness trait. In the low‐latitude garden with higher temperature, we found that reproductive phase was advanced and its length prolonged compared to the high‐latitude garden. This could possibly due to lower plasticity of maturity time. Additionally, plasticity in the length of the reproductive phase positively related with fitness in the low‐latitude garden. Marginal population from tropic had the lowest plasticity and fitness, and the poor capacity to cope with changing environment may result in reduction of this population. These results reflected genetic divergence in life history of S. alterniflora in China. Our study provided a novel view to test the center–periphery hypothesis by integration across a plant's life history and highlighted the significance in considering evolution. Such insights can help us to understand long‐term ecological consequences of life‐history variation, with implications for plant fitness, species interaction, and ecosystem functions under climate change. [ABSTRACT FROM AUTHOR]

In recent years, the continuous expansion of Spartina alterniflora (S. alterniflora) has caused serious damage to coastal wetland ecosystem. Mapping the coverage of S. alterniflora by remote sensing and analyzing its growth pattern pose great importance in controlling the expansion and maintaining the biodiversity of coastal wetlands in Guangxi. This study aimed to use harmonic regression to fit time series data of vegetation indices based on Landsat images, and the phenological features were extracted as the input of random forest model to distinguish S. alterniflora in coastal zone of Guangxi from 2009 to 2020. The influence of natural environmental factors on the distribution of S. alterniflora was evaluated by Maxent model, and the potential distribution was analyzed. The results showed that: (1) Based on the time series data of characteristic indices fitted by harmonic regression, the extraction of phenological features of S. alterniflora identification effect exhibited high accuracy (in the result of 2009, Overall Accuracy [OA] = 97.33%, Kappa = 0.95). (2) During 2009–2020, the S. alterniflora in coastal zone of Guangxi kept proliferating and expanding from east to west. The total area of S. alterniflora continued to increase while the growth rate showed a trend that increased first and then decreased. (3) The Maxent model shows good accuracy in simulating the habitat of S. alterniflora, with a potential distribution area of 14,303.39 hm2. The findings will be beneficial to the understanding of dynamic changes of S. alterniflora in coastal zone of Guangxi and provide a scientific reference for other coastal wetland studies on S. alterniflora expansion. [ABSTRACT FROM AUTHOR]

Invasive Spartina alterniflora has significant impacts on sediment carbon pool and turnover in the tidal wetlands of estuaries and coasts. Yet, how this exotic S. alterniflora affects sediment organic carbon mineralization dynamics remains poorly understood. In this study, sediment geochemical properties, organic carbon fractions, and mineralization dynamics were examined in a native Cyperus malaccensis habitat and three invasive S. alterniflora habitats (6-, 10-, and 14-year-old) in summer and winter. We found that invasive S. alterniflora generally increased sediment total organic carbon and their labile fraction contents. The organic carbon mineralization rates and cumulative carbon mineralization amounts were significantly influenced by invasive S. alterniflora, and their values increased with this exotic plant invasion chronosequences. The mineralization rates and cumulative mineralization amounts were also characterized by higher values in surface sediment (0 - 10 cm depth) compared to subsurface sediment (10 - 20 cm depth) and by seasonal variations with higher values in summer than in winter. The sediment organic carbon labile fractions, rather than total organic carbon, were the most important factor affecting carbon mineralization dynamics. The cumulative carbon mineralization amounts exhibited an excellent fit to the first-order kinetic equation (R2 = 0.93). The changes in modeled kinetic parameters (potential carbon mineralization amounts (C0) and carbon mineralization rate constant (k)) among these four habitats were similar to carbon mineralization rates, implying invasive S. alterniflora promoted the availabilities of organic compounds for microbial respiration metabolism. Overall, our findings highlighted the importance of S. alterniflora invasion in accelerating organic carbon decomposition and carbon dioxide release potential, although it also increases carbon accumulation. [ABSTRACT FROM AUTHOR]

Isotopic signatures offer new methods, approaches, and perspectives for exploring the ecological adaptability and functions of plants. We examined pattern differences in the isotopic signatures (δ13C, δ15N, δ34S) of Spartina alterniflora across varying plant life-death status along geographic clines. We extracted 539 sets of isotopic data from 57 publications covering 267 sites across a latitude range of over 23.8° along coastal wetlands. Responses of isotopic signatures to climate drivers (MAT and MAP) and the internal relationships between isotopic signatures were also detected. Results showed that the δ13C, δ15N, and δ34S of S. alterniflora were -13.52 ± 0.83‰C, 6.16 ± 0.14‰C, and 4.01 ± 6.96‰C, with a range of -17.44‰C to -11.00‰C, -2.40‰C to 15.30‰C, and -9.60‰C to 15.80‰C, respectively. The latitudinal patterns of δ13C, δ15N, and δ34S in S. alterniflora were shaped as a convex curve, a concave curve, and an increasing straight line, respectively. A decreasing straight line for δ13C within the ranges of MAT was identified under plant life status. Plant life-death status shaped two nearly parallel decreasing straight lines for δ34S in response to MAT, resulting in a concave curve of δ34S for live S. alterniflora in response to MAP. The δ15N of S. alterniflora significantly decreased with increasing δ13C of S. alterniflora, except for plant death status. The δ13C, δ15N, and δ34S of S. alterniflora are consistent with plant height, stem diameter, leaf traits, etc, showing general latitudinal patterns closely related to MAT. Plant life-death status altered the δ15N (live: 6.55 ± 2.23‰C; dead: -2.76 ± 2.72‰C), latitudinal patterns of S. alterniflora and their responses to MAT, demonstrating strong ecological plasticity and adaptability across the geographic clines. The findings help in understanding the responses of latitudinal patterns of the δ13C, δ15N, and δ34S isotope signatures of S. alterniflora in response plant life-death status, and provide evidence of robust ecological plasticity and adaptability across geographic clines. [ABSTRACT FROM AUTHOR]

Introduction: The WD40 gene family, prevalent in eukaryotes, assumes diverse roles in cellular processes. Spartina alterniflora, a halophyte with exceptional salt tolerance, flood tolerance, reproduction, and diffusion ability, offers great potential for industrial applications and crop breeding analysis. The exploration of growth and development-related genes in this species offers immense potential for enhancing crop yield and environmental adaptability, particularly in industrialized plantations. However, the understanding of their role in regulating plant growth and development remains limited. Methods: In this study, we conducted a comprehensive analysis of WD40 genes in S. alterniflora at the whole-genome level, delving into their characteristics such as physicochemical properties, phylogenetic relationships, gene architecture, and expression patterns. Additionally, we cloned the TTG1 gene, a gene in plant growth and development across diverse species. Results: We identified a total of 582 WD40 proteins in the S. alterniflora genome, exhibiting an uneven distribution across chromosomes. Through phylogenetic analysis, we categorized the 582 SaWD40 proteins into 12 distinct clades. Examining the duplication patterns of SaWD40 genes, we observed a predominant role of segmental duplication in their expansion. A substantial proportion of SaWD40 gene duplication pairs underwent purifying selection through evolution. To explore the functional aspects, we selected SaTTG1, a homolog of Arabidopsis TTG1, for overexpression in Arabidopsis. Subcellular localization analysis revealed that the SaTTG1 protein localized in the nucleus and plasma membrane, exhibiting transcriptional activation in yeast cells. The overexpression of SaTTG1 in Arabidopsis resulted in early flowering and increased seed size. Discussion: These outcomes significantly contribute to our understanding of WD40 gene functions in halophyte species. The findings not only serve as a valuable foundation for further investigations into WD40 genes in halophyte but also offer insights into the molecular mechanisms governing plant development, offering potential avenues in molecular breeding. [ABSTRACT FROM AUTHOR]

In this study, columnar sediment samples were collected from north to south along the northern Jiangsu coast, China, under Spartina alterniflora vegetation in four sample areas: Chuandong Port (Area-1), Tiaozini Scenic Area (Area-2), Yangkou Town (Area-3), and Meiledi Marine Park (Area-4). Organic carbon (OC), nutrient elements including total nitrogen (TN), total phosphorus (TP), and total sulfur (TS), and physicochemical properties including pH, salinity (Sal), moisture content (MC), and bulk density (BD) were measured. Pearson's correlation analysis was performed to explore the correlation between OC content and sedimentary physicochemical indexes, and the partial least squares regression (PLSR) model was used to analyze the factors affecting changes in OC content. The results found that the OC content of columnar sediments of S. alterniflora decreased with increasing depth in all four areas. The OC content in the four sample areas was mainly affected by the TN, pH, MC, TP, and burial depth. In particular, TN, MC, TP, TS, and clay content positively affected OC, whereas burial depth, pH, silt content, BD, sand content, and Sal negatively affected OC. The results of this study provide a valuable reference for evaluating the role of coastal wetlands in the global carbon cycle. [ABSTRACT FROM AUTHOR]

Species invasion in salt marsh wetlands is known to disturb the balance of biotic and abiotic ecosystems (e.g., changing material exchange cycles and community structure). However, its influence on the morphological evolution of salt marshes is not yet understood in depth. This study investigates the long-term temporal and spatial distributions of an invasive plant (Spartina alterniflora) and its morphological characteristics in the Yangtze Estuary by remote sensing imagery interpretation, tidal creek extraction, regional statistical analysis, and proximity analysis. The invaded site shows an area of Spartina alterniflora with a 35-fold increase from the start to the end of its initiation phase; it is the second biggest species in the study area. It is found that species invasion not only limited the expansion of native pioneer vegetation but also changed bio-geomorphic feedback loops. With the influence of plant invasion, median tidal creek lengths decreased and the median tidal creek sinuosity ratio remained stable, between 1.06 and 1.07 in the subarea. The method used here is adaptable to other salt marshes. The findings from this study can provide practical guidance for the restoration of native salt marshes in the estuary and thus control the spread of invasive species. [ABSTRACT FROM AUTHOR]

Aquatic plants suffer stress caused by abiotic and biotic variables. In estuaries, salinity is one of the main abiotic factors responsible for stress. This study aimed to evaluate oxidative stress in two species of aquatic macrophytes (Crinum americanum and Spartina alterniflora) that are common in Brazilian tropical estuaries. We measured reactive oxygen species (hydrogen peroxide and malondialdehyde) and total nitrogen (TN) and total phosphorus (TP) in the aboveground and belowground biomass of the species. In addition, we measured salinity, TN, and TP content in the sediment. Statistical tests included t test and the analysis of variance (ANOVA) followed by the Tukey's test. Our results showed that the greatest oxidative stress, in both species, occurred in areas of the estuary with lower salinity. For C. americanum, limitation by TN and TP content in the sediment is the main cause of oxidative stress. For S. alterniflora, the presence of C. americanum and the allelopathic compounds released by it seem to be the major cause of oxidative stress. Salinity did not induce oxidative stress in C. americanum and S. alterniflora in the estuary; however, the difference in TP and TN contents in the sediment played an important role in their responses to oxidative stress. [ABSTRACT FROM AUTHOR]

IntroductionCold stratification has a pronounced influence on seed germination, climate change is altering cold stratification regimes across climatic zones. Therefore, it is urgent to explore how seed germination from different geographic provenances responds to these changes. The invasive plant Spartina alterniflora spans three climatic zones along the Chinese coast, such distribution provides a natural temperature gradient to explore how warming alters the effects of cold stratification on germination. MethodsSpartina alterniflora seeds were collected from nine locations across three climatic zones in China from September to November in 2021. Seeds were planted in three common gardens with three latitude gradients of 21 °N, 28 °N, and 38 °N, after 0-month and 4-month cold stratification at 4 °C in November 2021 and March 2022, respectively. Each common garden simulated the natural temperature conditions and shield the plants from rain. ResultsResults showed that cold stratification led to explosive germination and rapidly reaching a plateau, shortened the germination time and improved the final germination rate. These effects were magnified from the high-latitude garden to the low-latitude one (i.e., warming). And the interactive effect of cold stratification and warming varied among provenances. For the subtropical and temperate provenances, the improvement in germination rate induced by cold stratification gradually increased from high-latitude garden to low-latitude one, while for tropical provenances, this difference progressively decreased. Discussion: Thus, our results indicated that subtropical and temperate provenances may migrate northward for adequate low temperatures to ensure high germination rate, because cold stratification can alleviate the negative impacts of warming on germination. For the tropical provenances, warming also suppressed the advantage that cold stratification provides in enhancing the germination rate, which may hinder their further spread southward. Our study contributes to understanding the responses of vegetation germination and recruitment across different climatic zones under global warming, providing insights for the distribution of cosmopolitan species and the management of exotic species.

IntroductionUnderstanding the constraints of phenotypic plasticity can provide insights into the factors that limit or influence the capacity of an organism to respond to changing environments. However, the relative effects of external and internal factors on phenotypic plasticity remain largely unexplored. Phenotypic integration, the pattern of correlations among traits, is recognized as an important internal constraint to plasticity. Phenotypic plasticity is critical in facilitating the acclimation of invasive species to the diverse environments within their introduced ranges. Consequently, these species serve as ideal models for investigating phenotypic plasticity and its underlying determinants.MethodsHere, we collected seeds of a global salt marsh invader Spartina alterniflora from seven invasive populations covering the entire latitudinal range in China. These populations were cultivated in two common gardens located at the southern and northern range margins, respectively. We quantified plasticity and variation therein for plant height, shoot density, first flowering day and inflorescence biomass (on a per capita basis). These traits have direct or indirect effects on invasiveness. We examined the relationships between traits plasticity with climatic conditions at site of origin (external factor) and phenotypic integration (internal factor).ResultsWe found that plasticity differed according to the trait being measured, and was higher for a trait affecting fitness. Phenotypic variance increased with latitude and temperature at the site of origin was the primary factor affecting phenotypic variation. These results indicated that external abiotic factors directly affected the selection on phenotypic plasticity of S. alterniflora.DiscussionOur study provides a unique viewpoint on assessing the importance of identifying influential factors and mechanisms underlying phenotypic plasticity. Understanding these factors and mechanisms is a critical indicator for invasive and other cosmopolitan species’ responses, establishment, persistence, and distribution under climate change.

Spatial quantification of blue carbon ecosystem stocks is crucial for developing policies to mitigate climate change, especially in regions experiencing ongoing wetland disturbance from biological invasions. We integrated multiple machine learning models with the space-for-time substitution method to quantify the spatiotemporal impact of Spartina alterniflora invasion on tidal marsh sediment blue carbon (soil organic carbon – 'SOC') stocks at 100 cm depth in the Yangtze Estuary. Our results show that the invasive S. alterniflora contributed more than half of the total SOC stocks (2,056 ± 379 Gg C, 1 Gg = 106 kg) in the 27,600 ha tidal marshes of the Yangtze Estuary, which were estimated to be 1,107 ± 176 Gg C. S. alterniflora increased the SOC stocks in the Yangtze Estuary within the first 15 years, but this gain was not sustained in the long term, with a gradual decline (by 13.14 Mg C/ha) observed after 15 years of S. alterniflora growth. We found that sediment salinity, tidal range, and human accessibility were strong indicators for modeling and predicting SOC stocks, with Random Forest providing the best simulation of tidal marsh SOC stocks (R2 = 0.894, RMSE=7.646 Mg C/ha, and MAPE=9.469 %). Our study provides much needed information on blue carbon stocks in the Yangtze Estuary under biological invasion stress, and offers guidance for targeted S. alterniflora management actions in the future.

In 2022, China released the Special Action Plan for the Control of Spartina alterniflora (2022–2025) with the goal of completely clearing S. alterniflora from China's coastal wetlands. It is crucial to conduct a thorough analysis of wetlands under artificial intervention and obtain reliable future wetland simulation results. The Yellow River Delta wetland is one of China's important wetland reserves, has faced severe impacts from S. alterniflora invasion over the past decade. This study focuses on the Yellow River Delta wetland, utilizing Landsat imagery and a combined object-oriented and pixel-based approach to achieve wetland mapping from 2013 to 2023. Through wetland analysis, we designed scenarios for natural development, ecological priority, farmland protection, and combined development. The patch generating land use simulation model was used to simulate wetland scenarios for 2030 and analyze factors influencing wetland use cover change and future conversion patterns. The results indicate that between 2013 and 2022, native vegetation was impacted by the invasion of S. alterniflora, with Suaeda glauca being the most affected. In 2023, the removal of S. alterniflora was effective, reducing its area by 42.37 km2 compared to pre-removal conditions. In all three scenarios, the area of Phragmites australis increased and is expected to dominate the wetlands, while the live space of other native salt marsh vegetation has also been restored. However, the predictions indicate that S. alterniflora still poses a potential threat of expansion in the future, necessitating continuous monitoring of its dynamics. We recommend implementing zoned management of the wetland, balancing ecological restoration in coastal areas with agricultural development in the western regions.

Spartina alterniflora Loisel poses risks to local vegetation types and coastal wetland. Managing the S. alterniflora invasion necessitates modeling its ecological response to the combined effects of flooding and soil salinity. Therefore, we integrate in situ sampling data and unmanned aerial vehicle point cloud data to quantitatively assess the effect of interaction between inundation and soil salinity on S. alterniflora and model the spatial distribution of S. alterniflora at the landscape scale. The study findings indicated that the optimal ecological amplitude for S. alterniflora in terms of flooding depth ranged from 0 to 1.02 m. Similarly, the optimal ecological amplitude for soil salinity was found to be between 9.47 and 26.13 g/kg. Based on these parameters, we were able to generate comprehensive habitat maps that depict the most suitable locations for the growth of S. alterniflora species across a larger landscape. The optimal distribution ranges for the canopy height and aboveground biomass of S. alterniflora were 1474.88 and 1307.99 ha, respectively. This research represents the first spatially quantitative investigation into the interaction effect of inundation and soil salinity on S. alterniflora. Furthermore, it provides a model for the optimal distribution range of S. alterniflora across expansive landscapes.

ABSTRACTInvestigating the functional traits of Spartina alterniflora can provide insights towards understanding its invasion mechanism, and developing a method leaves can improve its management in coastal wetlands. Here, we examined the relationship between 11 leaf functional traits of S. alterniflora and hyperspectral data and investigated the feature bands through importance score analysis. Using original spectral and first-order differential conversion data of feature bands, we established four prediction models: random forest (RF), support vector machine (SVM), eXtreme Gradient Boosting (XGBoost), and back propagation neural network (BPNN). The study results showed that: (1) the SVM model based on Random Forest Importance Score is well-suited for S. alterniflora leaf functional trait inversion; (2) the importance score of leaf functional traits differed, and first-order differential spectral data produced more bands with high scores compared with the original hyperspectral reflectance data; (3) first-order differential data modelling effects were slightly better than those of the original spectral data. However, the first-order differential treatment did not show a significant improvement in the validation accuracy compared with the original data, and the accuracy of some traits decreased. Our study provides a new methodological approach for improving the monitoring and management of S. alterniflora in coastal wetlands.

Spartina alterniflora (S. alterniflora) expanded continuously in the coastal zone of the mainland in China, which caused serious ecological problems. Currently, there are several studies on large-scale time-series mappings of S. alterniflora but the time interval of these mappings is over three years. Consequently, these studies fail to capture the rapid dynamics of S. alterniflora. Leveraging the temporal transferability of DeepLabv3+, this study annotated 2020 Sentinel-2 data as training data to obtain the optimal model. Subsequently, we applied this model to predict Sentinel-2 data for other years (2017, 2018, 2019 and 2021), respectively. Ultimately, we produced accurate time-series maps of S. alterniflora from 2017 to 2021 in mainland China (China mainland S. alterniflora, CMSA). Meanwhile, it also confirmed the high transferability of the DeepLabv3+ model in the time-series mapping of S. alterniflora. The obtained annual time-series maps have revealed a more detailed account of how S. alterniflora changes over time that previous studies had failed to capture. It has enriched our understanding of the dynamic changes in S. alterniflora. The mapping results revealed that S. alterniflora continued to grow along the mainland coast from 2017 to 2021 but at a slower growth rate. In some local regions, we discovered: (1) S. alterniflora populations can naturally shrink under certain conditions, such as in the Dandou Sea; (2) the area of S. alterniflora has increased slightly after decreasing for several years (e.g. Yueqing Bay). However, in some other regions, there is no observed regrowth after removal (e.g. Dongtan on Chongming Island and Chuandong Port). [ABSTRACT FROM AUTHOR]

Spartina alterniflora (S. alterniflora) has grown rapidly in China since its introduction in 1979, showing the trend of alien species invasion, which has seriously affected the ecosystem balance of coastal wetlands. The temporal and spatial expansion law of S. alterniflora can be obtained through remote sensing monitoring, which can provide a reference and basis for S. alterniflora management. This paper presents a method for extracting and mapping S. alterniflora based on phenological characteristics. The coastal areas of the Yangtze River Delta Urban Agglomeration are selected as the research area, and the Landsat time series data from 1990 to 2022 on the Google Earth Engine (GEE) platform are used to support the experiment in this paper. Firstly, the possible growing area of S. alterniflora was extracted using the normalized differential moisture index (NDMI), normalized differential vegetation index (NDVI), and normalized differential water index (NDWI); Then, the time series curve characterizing the phenological characteristics of vegetation was constructed using the vegetation index to determine the difference phase of phenological characteristics between S. alterniflora and other vegetation. Finally, a decision tree was constructed based on the phenological feature difference phase data to extract S. alterniflora, and it is applied to the analysis of temporal and spatial changes of S. alterniflora in the study area from 1990 to 2022. The results show that the area of S. alterniflora increased from ~1426 ha in 1990 to ~44,508 ha in 2022. However, the area of S. alterniflora began to show negative growth in 2015 due to the construction of nature reserves and ecological management. The results of correlation analysis showed that the growth of C. japonicum was significantly affected by temperature stress and weakly affected by precipitation. This study verified that Landsat time series images can effectively extract vegetation phenological information, which has strong feasibility for extraction and dynamic monitoring of S. alterniflora and provides technical support for the management and monitoring of invasive plants in coastal wetlands. [ABSTRACT FROM AUTHOR]

Coastal wetlands are characterized by high production and thus play an important role in global climate change. In past decades, the invasion of Spartina alterniflora has caused many problems of coastal wetlands in southeastern China, and the restoration of such areas was mainly conducted by replacing Spartina alterniflora with mangrove plants. This may impact the carbon storage dynamics in such areas. In this study, stable isotopes (d13C and d15N) and molecular analysis were used to reveal the impact of artificial restoration on the carbon storage of Quanzhou Bay Estuary Wetland Natural Reserve. The major results are as follows: (1) the change in dominant plants results in a changing major source of soil organic matter, from external sources to mangrove plants; (2) the decrease in soil organic matter following the removal of Spartina alterniflora may be primarily caused by the loss of external organic matter, while the production of mangroves may offset such loss and enhance the content and stability of carbon storage over the long term; (3) microbial CO2 assimilation may serve as an alternative source of bioavailable carbon and thus support the activity of benthic community. Our results revealed the long-term benefits of such restoration on the carbon storage function of wetlands invaded by Spartina alterniflora. Furthermore, the integrating of isotopic tracers and molecular technology may provide new insights in understanding the response of the carbon storage in coastal areas to human activity. [ABSTRACT FROM AUTHOR]

The impact of climate warming on soil microbial communities can significantly influence the global carbon cycle. Coastal wetlands, in particular, are susceptible to changes in soil microbial community structure due to climate warming and the presence of invasive plant species. However, there is limited knowledge about how native and invasive plant wetland soil microbes differ in their response to warming. In this study, we investigated the temporal dynamics of soil microbes (prokaryotes and fungi) under experimental warming in two coastal wetlands dominated by native Phragmites australis (P. australis) and invasive Spartina alterniflora (S. alterniflora). Our research indicated that short-term warming had minimal effects on microbial abundance, diversity, and composition. However, it did accelerate the succession of soil microbial communities, with potentially greater impacts on fungi than prokaryotes. Furthermore, in the S. alterniflora wetland, experimental warming notably increased the complexity and connectivity of the microbial networks. While in the P. australis wetland, it decreased these factors. Analysis of robustness showed that experimental warming stabilized the co-occurrence network of the microbial community in the P. australis wetland, but destabilized it in the S. alterniflora wetland. Additionally, the functional prediction analysis using the Faprotax and FunGuild databases revealed that the S. alterniflora wetland had a higher proportion of saprotrophic fungi and prokaryotic OTUs involved in carbon degradation (p < 0.05). With warming treatments, there was an increasing trend in the proportion of prokaryotic OTUs involved in carbon degradation, particularly in the S. alterniflora wetland. Therefore, it is crucial to protect native P. australis wetlands from S. alterniflora invasion to mitigate carbon emissions and preserve the health of coastal wetland ecosystems under future climate warming in China. [ABSTRACT FROM AUTHOR]

Salt marshes are capable of mitigating metal pollution in coastal environments, yet the efficacy of this remediation is contingent upon various environmental factors and the plant species involved. This study investigates the influence of different anthropogenic activities, including industrial, urban, recreational (in an insular area), and dredging operations, on the bioaccumulation of eight metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) within Spartina alterniflora Loisel. in the Patos Lagoon estuary, Brazil. The research aims to assess the pattern of metal bioaccumulation and distribution within the plant's leaves, stems, and roots while also examining metal presence in the sediment. Our main findings reveal that S. alterniflora exhibited elevated metal levels in its plant structure directly related with the metal concentrations in the surrounding sediment, which, in turn, is related to the different anthropogenic activities. The industrial area presented the highest metal levels in sediment and plant sections, followed by dredging, insular, and urban areas. This same pattern was mirrored for the bioconcetration factors (BCF), with the BCFs consistently indicating active metal bioaccumulation across all areas and for most of the metals. This provides evidence of the metal bioaccumulation pattern in S. alterniflora, with elevated BCFs in areas affected by activities with a higher degree of impact. Translocation factors (TF) showed varying metal mobility patterns within the plant's below-ground and above-ground sections across the different areas, with only Hg exhibiting consistent translocation across all study areas. Zn was the primary metal contributor in all plant sections, followed by Pb and Cu. It is worth noting that Pb is a non-essential metal for this plant, highlighting the relationship between elevated Pb contributions in the plant sections and the bioaccumulation of this metal within the plant's structure. Overall, this study emphasizes the bioaccumulation capacity of S. alterniflora and elucidate the intrinsic connection between different anthropogenic activities and their impact on the resultant availability and bioaccumulation of metals by this salt marsh plant. [ABSTRACT FROM AUTHOR]

The invasion and expansion of Spartina alterniflora have led to a certain degree of degradation in the ecological environment of coastal wetlands. To discuss the impacts of Spartina alterniflora expansion on the tidal channels, we took the third core area of the Dafeng Elk National Nature Reserve in Yancheng, Jiangsu Province as the study area, retrieved the spatial distribution of Spartina alterniflora by random forest algorithm based on long time series of Landsat and Sentinel-2 images, analysed the expansion models. The tidal channels were obtained by the image segmentation based on MSAVI and visual interpretation and the spatiotemporal evolution traits were finally analysed. The results revealed that the area and perimeter of Spartina alterniflora are continuously increasing, with a wide-ranging invasion. The coverage area peaks at 13.4%, making it the dominant species in the study area. When excluding the influence of human activities, a significant negative correlation emerges between the invasion rate and compactness of Spartina alterniflora and the spatio-temporal evolution of tidal channels. Faster invasion rates and greater compactness correspond to a deceleration in tidal channel morphology development. Additionally, we also found that the growth of Spartina alterniflora has a positive influence on the growth and reproduction of elk. [ABSTRACT FROM AUTHOR]

For decades in China, carbon neutrality policies have spurred the establishment of northern margin mangroves as artificial blue carbon ecosystems. However, there has been limited research on the impact of plantation and invasion on the stocks and sources of soil carbon and nitrogen in rehabilitated coastal wetlands. Non-native Kandelia obovata afforestation began on Ximen Island, Zhejiang, China, where Spartina alterniflora invasion had also occurred decades ago. Soil cores were collected from both mangrove and salt marsh habitats with depths from 0 to 50 cm and were analyzed for total carbon (TC), soil organic carbon (SOC), total nitrogen (TN), and the isotope of carbon and nitrogen in sediments. The results indicated that there were no significant differences in the TC, SOC, and C/N ratio between the K. obovata and the S. alterniflora, but there were significant differences in TN, isotope δ13C, and δ15N. The SOC content of both ecosystems in the 0–20 cm layer was significantly higher than that in the 30–50 cm layer. Our study has shown that the main sources of carbon and nitrogen for mangroves and salt marshes are different, especially under the impact of external factors, such as tidal waves and aquaculture. These findings provide insight into the ecological functioning of subtropical coastal wetlands and an understanding of the biogeochemical cycles of northern margin mangrove ecosystems. [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]

Invasive smooth cordgrass (Spartina alterniflora) has been expanding rapidly through the coastal wetlands of eastern China and these changes negatively affect local birds. In the Dafeng Milu National Nature Reserve (henceforth referred to as DMNNR), rapid degradation of spartina occurs after an increase in milu (Elaphures davidianus; hereafter elk) numbers and ecological hydrological engineering. We evaluated the impact of such degradation on the abundance and species diversity of birds in the DMNNR during 2017–2021. We found that the area covered by S. alterniflora decreased significantly in the study area at a rate of 310 ha per year and by 62% during 2017–2021 (p < 0.01). With this decrease in the S. alterniflora area, the species richness and abundance of birds first increased and then decreased. Songbird density clearly decreased but species richness did not significantly do so. This research demonstrated that during the initial stages of vegetation degradation, there was a positive effect on bird diversity. With the increasing vegetation degradation increases, both songbirds and waterbirds experience negative impacts. The DMNNR is an important stopover site for waterbirds in the East Asian–Australasian Flyway, and additional measures are needed to control vegetation degradation and to restore the native habitats for birds. [ABSTRACT FROM AUTHOR]

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