Topography regulates edaphic suitability for seedling establishment associated with tidal elevation in coastal salt marshes

Xie, Tian; Cui, Baoshan; Li, Shanze; Bai, Junhong

doi:10.1016/j.geoderma.2018.07.053

Cited by 32 publications

(24 citation statements)

References 46 publications

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“…The enhanced recirculation increases oxygen penetration and likely reduces the presence of sulphidic soil toxins (Koch and Mendelssohn 1989 , Lamers et al 2013 ). To date, however, the evidence of the relationship between raised sediment surfaces and pioneer establishment has been most commonly cited using anecdotal evidence and a few recent manipulative field experiments (Xie et al 2018 , Mossman et al 2020 ). The potentially major and widespread role that pioneer zone topography may play in the natural expansion of salt marshes has yet to be documented in relation to naturally occurring mudflat heterogeneity.…”

Section: Introductionmentioning

confidence: 99%

Restoration of biogeomorphic systems by creating windows of opportunity to support natural establishment processes

Fivash

Temmink

D’Angelo

et al. 2021

Ecological Applications

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In degraded landscapes, recolonization by pioneer vegetation is often halted by the presence of persistent environmental stress. When natural expansion does occur, it is commonly due to the momentary alleviation of a key environmental variable previously limiting new growth. Thus, studying the circumstances in which expansion occurs can inspire new restoration techniques, wherein vegetation establishment is provoked by emulating natural events through artificial means. Using the salt-marsh pioneer zone on tidal flats as a biogeomorphic model system, we explore how locally raised sediment bed forms, which are the result of natural (bio)geomorphic processes, enhance seedling establishment in an observational study. We then conduct a manipulative experiment designed to emulate these facilitative conditions in order to enable establishment on an uncolonized tidal flat. Here, we attempt to generate raised growth-promoting sediment bed forms using porous artificial structures. Flume experiments demonstrate how these structures produce a sheltered hydrodynamic environment in which suspended sediment and seeds preferentially settle. The application of these structures in the field led to the formation of stable, raised sediment platforms and the spontaneous recruitment of salt-marsh pioneers in the following growing season. These recruits were composed primarily of the annual pioneering Salicornia genus, with densities of up to 140 individuals/m 2 within the structures, a 60-fold increase over ambient densities. Lower abundances of five other perennial species were found within structures that did not appear elsewhere in the pioneer zone. Furthermore, recruits grew to be on average three times greater in mass inside of the structures than in the neighboring ambient environment. The success of this restoration design may be attributed to the combination of three factors: (1) enhanced seed retention, (2) suppressed mortality, and (3) accelerated growth rates on the elevated surfaces generated by the artificial structures. We argue that restoration approaches similar to the one shown here, wherein the conditions for natural establishment are actively mimicked to promote vegetation development, may serve as promising tools in many biogeomorphic ecosystems, ranging from coastal to arid ecosystems.

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Section: Introductionmentioning

confidence: 99%

Restoration of biogeomorphic systems by creating windows of opportunity to support natural establishment processes

Fivash

Temmink

D’Angelo

et al. 2021

Ecological Applications

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show abstract

“…Enhanced growth should in turn be responsible for greater resistance to disturbance and the perceived correlation between establishment and such raised surfaces (Balke et al, 2011;Hu et al, 2015). Past field experiments on the relationship between salt marsh recruitment and sediment micro-topography have suggested that these surface structures benefit recruitment through the modification of soil moisture conditions, and thereby alter oxygen penetration below ground (Xin et al, 2011;Lawrence et al, 2018;Xie et al, 2018;Mossman et al, 2019). Yet to date no in situ measurements of the oxygen levels within these structures have been reported in the literature, and discussion of the driving factors behind the enhanced recruitment has remained speculative.…”

Section: Introductionmentioning

confidence: 99%

Elevated micro-topography boosts growth rates in Salicornia procumbens by amplifying a tidally driven oxygen pump: implications for natural recruitment and restoration

et al. 2019

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Background and Aims The growth rate of pioneer species is known to be a critical component determining recruitment success of marsh seedlings on tidal flats. By accelerating growth, recruits can reach a larger size at an earlier date, which reduces the length of the disturbance-free window required for successful establishment. Therefore, the pursuit of natural mechanisms that accelerate growth rates at a local scale may lead to a better understanding of the circumstances under which new establishment occurs, and may suggest new insights with which to perform restoration. This study explores how and why changes in local sediment elevation modify the growth rate of recruiting salt marsh pioneers. Methods A mesocosm experiment was designed in which the annual salt marsh pioneer Salicornia procumbens was grown over a series of raised, flat and lowered sediment surfaces, under a variety of tidal inundation regimes and in vertically draining or un-draining sediment. Additional physical tests quantified the effects of these treatments on sediment water-logging and oxygen dynamics, including the use of a planar optode experiment. Key Results In this study, the elevation of sediment micro-topography by 2 cm was the overwhelming driver of plant growth rates. Seedlings grew on average 25 % faster on raised surfaces, which represented a significant increase when compared to other groups. Changes in growth aligned well with the amplifying effect of raised sediment beds on a tidally episodic oxygenation process wherein sediment pore spaces were refreshed by oxygen-rich water at the onset of high tide. Conclusions Overall, the present study suggests this tidally driven oxygen pump as an explanation for commonly observed natural patterns in salt marsh recruitment near drainage channels and atop raised sediment mounds and reveals a promising way forward to promote the establishment of pioneers in the field.

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“…After initial seedling establishment in calm growing conditions, potential storm events in the course of the growing season might exert strong mechanical stress on the developing seedlings (Paul et al 2016;Rupprecht et al 2017) and may limit their survival. Yet many studies on seedling survival are conducted under relatively low levels of hydrodynamic exposure (Silinski et al 2015;Cao et al 2018Cao et al , 2020Xie et al 2019). In contrast, little is known about survival in the period between initial seedling establishment and fully grown, patch forming pioneer vegetation, when the plants could still be vulnerable to more extreme hydrodynamic disturbances.…”

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confidence: 99%

Survival of the thickest? Impacts of extreme wave‐forcing on marsh seedlings are mediated by species morphology

Schoutens

Reents

Nolte

et al. 2021

Limnology & Oceanography

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Although tidal marshes are known for their coastal defense function during storm surges, the impact of extreme wave forcing on tidal marsh development is poorly understood. Seedling survival in the first season after germination, which may involve exposure to extreme wave events, is crucial for the natural establishment and human restoration of marshes. We hypothesize that species-specific plant traits plays a significant role in seedlings survival and response to wave induced stress, i.e., through stem bending and uprooting. To test this hypothesis, seedlings of pioneer species (Bolboschoenus maritimus, Schoenoplectus tabernaemontani, Spartina anglica, and Puccinellia maritima) with contrasting biophysical traits were placed in the Large Wave Flume in Hannover (Germany) and exposed to storm wave conditions. Seedlings of P. maritima and S. anglica experienced a lower loss rate and bending angle after wave exposure compared to S. tabernaemontani and especially B. maritimus. The higher loss rates of B. maritimus and S. tabernaemontani result from deeper scouring around the stem base. Scouring depth was larger around stems of greater diameter and higher resistance to bending. Here, B. maritimus and S. tabernaemontani have both thicker and stiffer stems than S. anglica and P. maritima. Our results show that especially seedlings with thicker stems suffer from erosion and scouring, and have the highest risk of being lost during extreme wave events. This implies that for successful seedling establishment and eventually the establishment of a mature tidal marsh vegetation, the species composition and their capacity to cope with storm wave disturbances is crucial.

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Topography regulates edaphic suitability for seedling establishment associated with tidal elevation in coastal salt marshes

Cited by 32 publications

References 46 publications

Restoration of biogeomorphic systems by creating windows of opportunity to support natural establishment processes

Restoration of biogeomorphic systems by creating windows of opportunity to support natural establishment processes

Elevated micro-topography boosts growth rates in Salicornia procumbens by amplifying a tidally driven oxygen pump: implications for natural recruitment and restoration

Survival of the thickest? Impacts of extreme wave‐forcing on marsh seedlings are mediated by species morphology

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