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Change in the vegetation cover (%+SE) on the hummock of the micro-topography of the three sites, from March 1997 to March 1999. d, Site 1; Ã, Site 2; m, Site 3.
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Low saltmarshes are subjected to variability between sites and tidal cycles in terms of erosive forces by current and waves, the frequency and duration of flooding and soil salinity. The establishment of vegetation in pioneer zones is directly related to sedimentary dynamics but few data are available concerning the effects of plants on sediment dy...
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... with the change in micro-topography, the vegetation changed from 1997 to 1999: the cover of Puccinellia maritima [ Fig. 6(a)] increased significantly from 20% up to 95%, depending on the site (t ¼ 5:08 in site 1, t ¼ 5:13 in site 2 and t ¼ 4:21 in site 3; P\0:001). Spartina anglica, which already had a low cover in 1997, accounted for less than 1% in all three sites in 1999 [ Table 2 Mean percentage cover (AESE) of each micro-topography component for initial ...
Citations
... P. maritima can be found in more sheltered pioneer salt marshes and shows flexible stems with leaves covering the sediment surface (Möller et al., 2014;Schoutens et al., 2021). Both species grow in dense tussocks (Bouma et al., 2009a) and can act as ecosystem engineers by enhancing the deposition of sediments (Sańchez et al., 2001;Langlois et al., 2003), and by altering the water flow . ...
Salt marshes play an important role in coastal protection by reducing the impact of waves and shoreline erosion risks. While mature vegetation is responsible for the persistence and stability of marsh ecosystems, seedling survival of pioneer species is especially crucial for marsh propagation. Marsh seedlings, however, may be threatened by climate change induced increased coastal storm surge intensity and accompanying (extreme) wave conditions, imposing stronger drag forces on marsh seedlings. We test the hypothesis that drag forces experienced by seedlings increase with horizontal orbital velocity (Uw ) in a species-specific manner, and that the drag forces experienced are individual-plant trait-mediated. To test our hypotheses, seedlings of four contrasting pioneer marsh species (Bolboschoenus maritimus, Schoenoplectus tabernaemontani, Spartina anglica, and Puccinellia maritima) were exposed to storm wave conditions in a flume, where Uw and experienced drag forces were measured. Linear mixed effect models demonstrated that seedling’s susceptibility to storm wave conditions is at least partly mediated by individual plant traits. Drag forces experienced by seedlings tended to increase with Uw , and with stem length and diameter. The interplay of both traits was complex, with increasing stem length being the most important trait accounting for increases in drag forces experienced at low to moderate Uw , while the stem diameter became more important with increasing Uw . Furthermore, experienced drag forces appeared to be affected by species-specific traits such as rigidity and leaf growth, being highest for Bolboschoenus maritimus and lowest for Puccinellia maritima. Our results provide important mechanistic insights into the drivers of tidal marsh seedling vulnerability to storm wave conditions due to experienced drag, both based on the traits of individual plants and species-specific ones. This type of knowledge is of key importance when modelling saltmarsh establishment and resilience under climate change.
... Species of the genus Puccinellia are generally known as "alkali grasses" because of their high tolerance to alkaline salinity [73]. Puccinellia maritima is often described as a dominant species of the lower stabilized zone of Northwestern European salt marshes [74], but it occurs also in the pioneer zone with the start of sediment accumulation [75]. In addition, P. maritima is one of the first colonizing species during the formation of vegetation during the establishment of dune ridges [76]. ...
Plant modularity-related traits are important ecological determinants of vegetation composition, dynamics, and resilience. While simple changes in plant biomass resulting from salt treatments are usually considered a sufficient indicator for resistance vs. susceptibility to salinity, plants with a clonal growth pattern show complex responses to changes in environmental conditions. Due to physiological integration, clonal plants often have adaptive advantages in highly heterogeneous or disturbed habitats. Although halophytes native to various heterogeneous habitats have been extensively studied, no special attention has been paid to the peculiarities of salt tolerance mechanisms of clonal halophytes. Therefore, the aim of the present review is to identify probable and possible halophytic plant species belonging to different types of clonal growth and to analyze available scientific information on responses to salinity in these species. Examples, including halophytes with different types of clonal growth, will be analyzed, such as based on differences in the degree of physiological integration, ramet persistence, rate of clonal expansion, salinity-induced clonality, etc.
... × 10 −6 m 2 g −1 ). These 4 plant populations are commonly used for beach protection [50], and P. maritima is considered a key species in stabilizing the sediment in coastal marshes [51]. Among the mangrove plant populations, Kandelia obovate Sheue et al. (k ∈ (14.0, 14.1) × 10 −6 m 2 g −1 ) and Sonneratia apetala Buch.-Ham. ...
An accelerating rate of sea level rise (SLR) is causing huge inundation pressure on coastal wetlands worldwide. Vegetation of coastal wetlands plays a key role in stabilizing the coast and accreting sediment in order to mitigate the negative impact of SLR. The ability to accrete sediment is influenced by individual species traits; however, there are insufficient information and indicators to identify differences in the adaptability of various coastal vegetations to SLR at a regional or global scale. Here, the potential adaptation of 27 plant populations in coastal wetlands subject to SLR was evaluated using a compiled global dataset and a marsh equilibrium model. Sediment accretion efficiency differed among plant populations, but most coastal marsh populations and a few mangrove populations had relatively high accretion rates; habitats with high accretion rates will have a better potential to deal with the threat of SLR. These results showed that latitude and efficiency shared a nonlinear relationship, and plant stem density and root structure were among the important factors that influenced the efficiency. Fibrous root plant populations had a greater sediment accretion efficiency than tap root plant populations, and perennial populations had a greater sediment accretion efficiency than annual plant populations. These findings can provide key parameters relating to the sediment accretion efficiency of hydrological and geomorphic models on a global scale. This study offers some novel insights into the dynamic changes in coastal wetlands following SLR that will be particularly useful in devising appropriate strategies for the protection and management of coastal wetlands.
... D. spicata therefore clearly played a role as a delayed but long-lasting ecosystem engineer (Wright and Jones, 2006), whose lingering impact on marsh platform elevation led to consequential and multiannual shifts in array of species dominating vegetative cover in areas of suitable elevation and where N-supply exceeded a threshold value. Similar, but less impactful roles of marsh taxa as ecosystem engineers have been mentioned for other wetland species, such as Juncus gerardii (Hacker and Bertness, 1995) and Puccinellia maritima (Langlois et al., 2003). ...
Vegetative cover was mapped annually, 1976-2022, in experimental plots in Great Sippewissett Marsh, Cape Cod, USA, chronically fertilized at different doses, and subject to changes in sea level and other climate-related variables. Dominant species within areas of higher elevation in the plots followed different decadal trajectories: rise in sea level diminished cover of Spartina patens; higher N supplies increased cover of Distichlis spicata. The opportunistic growth response of D. spicata to high N supplies unexpectedly fostered increased platform accretion, a feature that persisted for succeeding decades and led to further changes in vegetation: D. spicata functioned as an effective ecosystem engineer with long-term ecological consequences. Shrubs usually found in upper marsh margins expanded into areas where D. spicata had stimulated accretion, then shaded and excluded D. spicata, but subsequently lost cover as sea level rise continued. Increased N supply converted stands of Spartina alterniflora, the dominant low marsh species, from short to taller ecophenotypes; sea level rise had minor effects on S. alterniflora, but during 2019-2022 appeared to reach a tipping point that fostered taller S. alterniflora and bare space even in un-fertilized control plots, and in Great Sippewissett Marsh in general. Model results anticipate that-in spite of potential accretion enhanced by vegetation and ecosystem engineer effects-there will be loss of high marsh, transient increases of low marsh, followed by loss of low marsh, and eventual conversion to shallow open water by the end of the century. Dire local projections match those of the plurality of recent reports from salt marshes around the world. Proposed management strategies may only delay unfortunate outcomes rather than maintain wetlands. Concerted reductions of warming from greenhouse gases, and lower N loads seem necessary to address the coming crises in wetlands-and many other environmental threats.
... Além disso, de acordo com muitos estudos, a dinâmica de sedimentação em zonas de sapal baixo está fortemente correlacionada com o tipo, cobertura e altura da vegetação. Por exemplo, Puccinellia maritima, uma espécie comum em zonas estuarinas, da família Poaceae, reduziu a frequência e magnitude dos eventos de erosão e aumentou significativamente a acreção de sedimentos (Langlois et al., 2003). ...
A incorporação de Soluções Baseadas na Natureza na gestão e manutenção de canais navegáveis é um fator com potencial para a redução da sedimentação nos canais, promovendo o aumento da resiliência destas infraestruturas. Neste trabalho, propôs-se uma solução de mitigação da sedimentação com base em vegetação. A análise desta nova solução foi feita com recurso ao modelo numérico XBeach. A taxa de assoreamento observada foi determinada através dos levantamentos disponíveis para o canal de acesso ao Cais da Bestida (Murtosa), executados antes e após a intervenção de dragagem. As configurações adotadas para o XBeach permitiram simular adequadamente a taxa de assoreamento observada. A realização de um conjunto de experiências numéricas com o XBeach permitiu efetuar uma análise de sensibilidade a vários parâmetros associados às características da vegetação: altura, diâmetro e densidade de colocação. Os resultados obtidos sugerem que a presença de vegetação nas margens do canal apresenta uma capacidade de redução em até 77% do assoreamento observado no canal. Por fim, estabeleceu-se um gráfico que correlaciona a taxa expectável de redução de assoreamento em função da altura e densidade da vegetação a considerar.
... Cela rejoint de précédentes études, qui ont démontré que le processus d'accrétion initie la colonisation des espèces riveraines appartenant au premier stade de la succession écologique (Gurnell et al. 2012;Corenblit et al. 2007). Le processus de sédimentation joue également un rôle important dans la colonisation et le devenir d'autres espèces pionnières telles que pour Spartina alternifolia (Ge et al. 2015) et Puccinellia maritima (Langlois et al. 2003) qui sont toutes deux affiliées aux marais salés. Mais dans certains types d'habitats soumis à perturbation, l'effet des processus sédimentaires sur la dynamique des espèces pionnières reste encore peu connu. ...
La dynamique de la végétation riveraine est étroitement liée aux régimes de perturbation du cours d’eau, notamment les crues, ainsi qu’aux processus physiques et biologiques qui en découlent. L ’impact des activités humaines sur les rivières comme l’endiguement, la chenalisation ou l’exploitation hydroélectrique et sédimentaire, a fortement modifié ces régimes. Cela se traduit, entre autre, par une stabilisation du milieu et une régression des stades pionniers de l’habitat riverain due au manque de rajeunissement de celui-ci par les crues .
A l’échelle de l’arc alpin, Typha minima Hoppe (la petite massette) est une espèce herbacée clonale qui colonise les habitats pionniers des cours d’eau de piémont. Cette espèce a vu ses populations fortement décroître au cours du siècle dernier, lui valant le statut d’espèce protégée dans plusieurs pays européens. En France, de nombreuses menaces pesant sur cette espèce persistent tel que la chenalisation, la modification du régime de crue et la destruction de son habitat par des travaux menés dans le lit et sur les berges des cours d’eau. C’est notamment le cas des travaux menés depuis 2004 par le Symbhi (Syndicat Mixte des Bassins Hydrauliques de l'Isère) dans le cadre du projet « Isère Amont » qui ont impacté des stations de T. minima sur l’Isère .Des mesures de compensations en ont résulté et ont accompagné la mise en place d’un projet de restauration de l’espèce dans la zone d’emprise des travaux.
L’objectif de ce travail de thèse est de produire des connaissances sur la niche écologique et la dynamique spatiotemporelle d’une espèce clonale colonisant le stade pionnier de l’habitat riverain : la petite massette (Typha minima Hoppe), afin de servir de base théorique aux futurs projets de conservation et de restauration. Pour ce faire, la problématique suivante a été formulée : Quelles sont les variables environnementales et les processus écologiques qui affectent la dynamique spatio temporelle de T. minima et en quoi ces connaissances peuvent elles être appliquées à sa restauration et sa conservation?
i) La première étape est de déterminer quels sont les facteurs biotiques et abiotiques liés
aux processus sédimentaires et de succession écologique qui affectent l a dynamique
locale des taches de T. minima . Les résultats montrent que la progression des taches de T. minima est liée au caractère pionnier des bancs (sédiments fins , faible altitude et couvert végétal). Le maintien et la régression des taches sont au contraire liés à la maturité de l’habitat, induit s par un processus de succession écologique plus avancé, avec un développement de la végétation et une amplification du phénomène d’accrétion.
ii) Dans une seconde partie nous avons testé les effets de la compétition interspécifique
avec des saules (Salix alba) et de l’ensevelissement par les sédiments sur la compétitivité
et l’investissement dans la reproduction de T. minima . Bien que souvent mentionnée
comme la principale cause de régression de l’espèce, la compétition interspécifique avec
les saules n’affecte que peu T. minima alors que l’effet de l’ensevelissement par les
sédiments est important.
iii) Enfin, dans le but d’améliorer les protocoles de restauration de T. minima, plusieurs plusieurs expérimentations visant à tester l’effet de différentes biomasses initiales transplantées, la hauteurs par rapport à l’eau, le types de berge, la forme des placettes et l'association avec d’autres espèces pionnières ont été réalisées entre 2013 et 2016. Les résultats montrent que transplanter T. minima avec une biomasse initiale importante sous forme de placette linéaire parallèle au cours d’eau à des hauteurs comprises entre +1.00m et +1.55m est optimal.
Ces travaux caractérisent caractérisent d’une part d’une part les facteurs environnementaux et les processus en jeu dans dans la dynamique de T. minima et d’autre part, optimisent les protocoles de restauration contribuant ainsi à alimenter les futurs projets de restauration et de conservation de l’espèce.
(Riparian vegetation dynamics are linked to river disturbance regimes including floods as well as physical and biological processes. Human activities such as containment, channelization, hydroelectric dam and sand gravel extraction have modified this regime. The main consequences are the stabilization of environmental parameters and the regression of pioneer stage driven by a lack of habitat rejuvenation by floods.
In the Alps, Typha minima Hoppe (the dwarf bulrush) is a clonal herbaceous plant species that colonizes pioneer stage habitat of piedmont rivers. It is a threatened species in the Alps because of the drastic decrease of its population during the last century. In France, the river channelization, the modification of flood regime and the works inside riverbed and banks still threaten relict populations. The Symbhi (Syndicat Mixte des Bassins Hydrauliques de l’Isère) initiated river works in 2004 through the “Isère Amont” project, impacted T. minima populations along the Isère and was mandated to set up a restoration project.
The main thesis objective is to produce knowledge about the ecological niche and spatiotemporal dynamics of a clonal plant species (T. minima) that colonizes pioneer riparian habitat. The following question is formulated: What are the environmental variables and ecological processes that affect the spatio-temporal dynamics of T. minima, and how could this knowledge be applied to its restoration and conservation?
i) The first step was to determine the biotic and abiotic parameters, linked to ecological succession and sediment accretion, involved in T. minima’s local patch dynamic. The results showed that local patch progression is linked to pioneer bar characteristics (fine sediment, low elevation and low vegetation cover). Patch maintenance and regression are related to more mature bar characteristics, induced by the progress of ecological succession and the accretion process amplification.
ii) Second, we experimented ex-situ the effects of interspecific competition and sediment burial on the competitive and reproduction abilities of T. minima. Although considered as the main cause of T. minima regression, we highlighted that interspecific competition with Salix alba has lower effect on T. minima than sediment burial.
iii) Last, to improve the restoration methods of T. minima we implemented in-situ experiments between 2013 and 2016. The objectives were to test the effects of initial transplanted biomass, transplantation elevation related to the mean water level, bank type, plot form and association with other pioneer species. The results show that transplantation with high or medium initial biomass in linear plots parallel to the water flow between +1.00m and +1.55m optimizes T. minima population restoration.
This work, that characterizes the environmental factors, the processes involved in T. minima’s local patch dynamics and that optimize the design of restoration protocols, contribute to improve future pioneer species restoration and conservation projects.)
... Cela rejoint de précédentes études, qui ont démontré que le processus d'accrétion initie la colonisation des espèces riveraines appartenant au premier stade de la succession écologique (Gurnell et al. 2012;Corenblit et al. 2007). Le processus de sédimentation joue également un rôle important dans la colonisation et le devenir d'autres espèces pionnières telles que pour Spartina alternifolia (Ge et al. 2015) et Puccinellia maritima (Langlois et al. 2003) qui sont toutes deux affiliées aux marais salés. Mais dans certains types d'habitats soumis à perturbation, l'effet des processus sédimentaires sur la dynamique des espèces pionnières reste encore peu connu. ...
La dynamique de la végétation riveraine est étroitement liée aux régimes de perturbation du cours d’eau, notamment les crues, ainsi qu’aux processus physiques et biologiques qui en découlent. L’impact des activités humaines sur les rivières comme l’endiguement, la chenalisation ou l’exploitation hydroélectrique et sédimentaire, a fortement modifié ces régimes. Cela se traduit, entre autre, par une stabilisation du milieu et une régression des stades pionniers de l’habitat riverain due au manque de rajeunissement de celui-ci par les crues. A l’échelle de l’arc alpin, Typha minima Hoppe (la petite massette) est une espèce herbacée clonale qui colonise les habitats pionniers des cours d’eau de piémont. Cette espèce a vu ses populations fortement décroître au cours du siècle dernier, lui valant le statut d’espèce protégée dans plusieurs pays européens. En France, de nombreuses menaces pesant sur cette espèce persistent tel que la chenalisation, la modification du régime de crue et la destruction de son habitat par des travaux menés dans le lit et sur les berges des cours d’eau. C’est notamment le cas des travaux menés depuis 2004 par le Symbhi (Syndicat Mixte des Bassins Hydrauliques de l'Isère) dans le cadre du projet « Isère Amont » qui ont impacté des stations de T. minima sur l’Isère. Des mesures de compensations en ont résulté et ont accompagné la mise en place d’un projet de restauration de l’espèce dans la zone d’emprise des travaux.L’objectif de ce travail de thèse est de produire des connaissances sur la niche écologique et la dynamique spatiotemporelle d’une espèce clonale colonisant le stade pionnier de l’habitat riverain : la petite massette (Typha minima Hoppe), afin de servir de base théorique aux futurs projets de conservation et de restauration. Pour ce faire, la problématique suivante a été formulée : Quelles sont les variables environnementales et les processus écologiques qui affectent la dynamique spatio-temporelle de T. minima et en quoi ces connaissances peuvent-elles être appliquées à sa restauration et sa conservation?i) La première étape est de déterminer quels sont les facteurs biotiques et abiotiques liés aux processus sédimentaires et de succession écologique qui affectent la dynamique locale des taches de T. minima. Les résultats montrent que la progression des taches de T. minima est liée au caractère pionnier des bancs (sédiments fins, faible altitude et couvert végétal). Le maintien et la régression des taches sont au contraire liés à la maturité de l’habitat, induits par un processus de succession écologique plus avancé, avec un développement de la végétation et une amplification du phénomène d’accrétion.ii) Dans une seconde partie nous avons testé les effets de la compétition interspécifique avec des saules (Salix alba) et de l’ensevelissement par les sédiments sur la compétitivité et l’investissement dans la reproduction de T. minima. Bien que souvent mentionnée comme la principale cause de régression de l’espèce, la compétition interspécifique avec les saules n’affecte que peu T. minima alors que l’effet de l’ensevelissement par les sédiments est important.iii) Enfin, dans le but d’améliorer les protocoles de restauration de T. minima, plusieurs expérimentations visant à tester l’effet de différentes biomasses initiales transplantées, hauteurs par rapport à l’eau, types de berge, formes des placettes et associations avec d’autres espèces pionnières ont été réalisées entre 2013 et 2016. Les résultats montrent que transplanter T. minima avec une biomasse initiale importante sous forme de placette linéaire parallèle au cours d’eau à des hauteurs comprises entre +1.00m et +1.55m est optimal.Ces travaux caractérisent d’une part les facteurs environnementaux et les processus en jeu dans la dynamique de T. minima et d’autre part, optimisent les protocoles de restauration, contribuant ainsi à alimenter les futurs projets de restauration et de conservation de l’espèce.
... The study bend is located in the upper-intertidal domain, implying that during spring tides, the channel empties out twice per day, while around neap tides, the whole channel is dry for about one week. The point-bar-top zone exhibits a clear vegetation zonation typical of the Mont-Saint-Michel Bay (Tessier et al., 2000;Bonnot-Courtois et al., 2002;Langlois et al., 2003;D etrich e et al., 2011), with a permanent vegetation cover of Halimione portulacoides and Festuca rubra in the middle (ca 6.2-7.0 MAMSL, in the study site) and high (>7.0 ...
Intertidal meanders developed on salt marshes are known to expand and produce inclined heterolithic stratification rich in fine-grained sediments and to bear evidence for rhythmic deposition in the upper part of the inner meander bend(i.e. the upper part of the point bar). This occurs because the lower point-bar deposits are washed by strong currents, which remove mud drapes and develop discontinuous record of tidal cycles. Although these criteria are widely accepted, facies models for tidal point bars still lack a three-dimensional perspective and overlook the along-bend variability of sediment distribution. The present study focuses on a hypertidal point bar belonging to the upper-intertidal domain of the Mont-Saint-Michel Bay (France), and it analyses the sedimentology of a 3D time-framed accretionary package formed between 28 March 2012 and 29 November 2012 by means of lidar topographic data, geomorphological field surveys and sedimentological core data. To define the 3D time-framed accretionary package, data from thirteen lidar topographic surveys were used to create the point-bar synthetic stratigraphy. Data shows that over the study period the point bar expanded alternating deposition along its seaward and landward sides, pointing out the occurrence of depositional patterns more complex than a simple progressive expansion of the bend. The thickest deposits were accumulated in the point-bar-apex zone, where the largest amount of mud was also stored. High sediment accretion in the bend-apex zone is ascribed to the development of low-energy conditions due to flow and bed configuration. High accretion rate of the point-bar-apex zone promoted also a better preservation of rhythmites, which are almost missing from deposits accumulated along the point-bar sides. This study remarks that preservation of mud and tidal rhythmites within intertidal-point-bar deposits is controlled, not only by their elevation with respect to the tidal range, but also by their location along the point bar.
... The preference for hummocks is particularly true for woody midstory and overstory species, but hummocks also exhibit greater understory diversity of both vascular plants and mosses (Diamond et al., 2020; but see Peterson & Baldwin, 2004). While not as pronounced as differences in woody vegetation, in some systems like salt and freshwater marshes that lack woody vegetation, hummocks are also associated with greater abundances of herbaceous species than hollows (Fogel et al., 2004;Langlois, Bonis, & Bouzillé, 2003;Shen et al., 2006). On the other hand, some floodplain tree species in the peat swamps of Indonesia (Freund, Harsanto, Purwanto, Takahashi, & Harrison, 2018;Shimamura & Momose, 2005) may not prefer hummocks, and perhaps have developed adaptations to hydrologically dynamic environments. ...
Microtopography, or the small‐scale variation in ground surface height (10⁻¹–10⁰ m) over short (10⁰–10² m) spatial scales, is a ubiquitous feature of wetlands globally. This variation in elevation, characterized by local high (“hummocks”) and low (“hollows”) patches, is more structured than what is observed in uplands, and is intertwined with concordantly structured spatiotemporal variability in hydrologic regimes and associated ecological processes. The importance of microtopography in wetlands is manifold, with critical influence on local hydrological, biogeochemical, and biological processes. Further, the creation and maintenance of wetland microtopography is a balance between activation processes (i.e., those that induce random elevation variation) and autogenic reinforcement processes (i.e., those that provide the feedbacks necessary for the persistence of microtopography). While there are many mechanisms that create vertical structure (e.g., tree falls, accumulation of roots and soil organic matter, and sediment deposition), they all yield a similar core feedback to enhance and sustain microtopographic structure. Finally, microtopography contributes to spatial patterning that confers emergent ecosystem‐scale functions such as hydrologic storage and flows, carbon cycling, organism dispersal, and biodiversity. There is an ongoing need to study the origins and implications of this fine‐scale variation in elevation, as well as the utility of including microtopography in model predictions and ecological restoration efforts.
This article is categorized under:
• Water and Life > Conservation, Management, and Awareness
Abstract
In wetlands, a little relief or microtopographic variation in the soil surface influences numerous hydrological and biogeochemical processes, creating strong feedbacks with ecological patterns, and functions that are important for management and conservation.
... The establishment of common salt marsh grass (P. maritima) is key for moving towards a diversified community (Langlois et al. 2003). ...
... Other species, for example the perennial P. maritima, thrive on sediment deposition. They form accretion hummocks which promote a stable and diversified marsh community (Langlois et al. 2003). Vegetation establishment is facilitated by a stable soil ), thus a dynamic bed level is expected to set additional pioneer vegetation establishment and survival boundaries. ...
... Once established, however, perennials are expected to be less vulnerable than annuals. Surmountable sedimentation, erosion and sediment dynamics are species specific but also life stage specific and depend on temporal and spatial manifestations of sediment dynamics Cao et al. 2018;Langlois et al. 2003;Lo et al. 2017). ...
Salt marshes, providing numerous ecosystem services, are degrading worldwide. To effectively aid conservation and restoration efforts, increased knowledge on marsh expansion processes and the initial establishment of pioneer vegetation is essential. In this study, we disentangle environmental drivers that affect the lifecycle of the annual pioneer Salicornia procumbens at the salt marsh edge. We studied the effect of various environmental variables on the start of germination, germination success and mortality before seed-set in a field experiment in the Dutch Wadden Sea at Westhoek. Our results indicate that temperature and sedimentation inhibited the initiation of germination. Once germination occurred, higher precipitation rates increased germination success. In contrast, sedimentation rates above 0.5 mm day−1 halved germination success through burial of freshly sprouted seedlings. Unexpectedly, natural germination was low, indicating that seed availability may have been limited, despite a seed source nearby. Frequent inundation, extended periods without inundation (through desiccation of the soil) and a highly dynamic bed level increased mortality before seed-set. Consequently, bed-level dynamics (erosion, sedimentation and bed-level variation) impact seed production dually (decrease germination and increase mortality) and thus potentially reproduction success. A high seed reproduction is crucial for annuals, such as S. procumbens, to re-establish the following year. Next to advancing our general knowledge of natural salt marsh expansion, results in this study can also be used to assess the potential of a given site for salt marsh stimulation or restoration. Seed availability and local bed-level dynamics are key in the successful establishment of a salt marsh pioneer: Salicornia procumbens.
