Abstract
AbstractConservation and restoration of salt marsh ecosystems are becoming increasingly important because of the many ecosystem services they provide. However, the processes controlling salt marsh establishment and persistence, especially on bare tidal flats in muddy areas, remain unclear. As muddy sediments typically experience a restriction of soil drainage, we expect that a surface drainage relief due to a heterogeneity topography, as might occur on the edge of tidal channels, can facilitate the establishment of salt marsh vegetation on muddy tidal flats. By means of a manipulative field experiment, using “Mega‐Marsh Organ” mesocosms, we investigated the impact of surface drainage and elevation relative to mean sea level on (1) the survival of Spartina anglica seedlings from three different age classes: 1‐yr, 3‐month, and 1‐week; and (2) the growth performance of mature S. anglica marsh tussocks. S. anglica seedling survival, especially in the establishment phase, was positively affected by better surface drainage, increases of seedling age, and higher elevation relative to mean sea level. That is, the survival rate of S. anglica seedlings at the end of 6th week increased from 0% (at surface water undrained, 1‐week, 0 cm elevation) to 94.44% (at surface water drained, 1‐yr, 90 cm elevation). In contrast, surface drainage did not affect the performance of large S. anglica marsh tussocks, as only increased elevation relative to mean sea level was shown to affect S. anglica tussock growth in terms of plant height, shoot numbers, and dry biomass. Based on our findings, we proposed a conceptual model to understand how surface drainage‐driven feedbacks in a heterogeneous topography may be reinforced to induce salt marsh establishment in muddy systems. Further testing of present hypothesized model would be beneficial for insights into salt marsh establishment on tidal mudflats.
Highlights
Conservation and restoration of salt marsh ecosystems are becoming increasingly appreciated because of the many vital ecosystem services they provide (Gedan et al 2009, Barbier et al 2011, Shepard et al 2011, Kirwan and Guntenspergen 2012, Kirwan and Mudd 2012, Burden et al 2013, Schepers et al 2017)
All analyses were performed with SPSS 18.0 software (SPSS, Chicago, Illinois, USA). Seedlings establishment Both Cox regression and three-way ANOVAs results revealed that the surface drainage treatment significantly affected S. anglica seedling survival during the 6-week experiment with the poorly consolidated mud of Perkpolder (Fig. 4; P < 0.05, Table 2)
As muddy sediments typically experience a restriction of vertical soil drainage, we expect that a surface drainage as might occur due to a topography relief on the edge of tidal channels can facilitate the establishment of salt marsh vegetation on muddy tidal flats
Summary
Conservation and restoration of salt marsh ecosystems are becoming increasingly appreciated because of the many vital ecosystem services they provide (Gedan et al 2009, Barbier et al 2011, Shepard et al 2011, Kirwan and Guntenspergen 2012, Kirwan and Mudd 2012, Burden et al 2013, Schepers et al 2017). The vegetated marsh is stabilized by biogeomorphic positive feedback loops between vegetation growth, sediment trapping, and sediment stabilization (van Wesenbeeck et al 2008, Marani et al 2010, Wang and Temmerman 2013), resulting in channel formation (Fagherazzi and Sun 2004, Fagherazzi et al 2004, 2013, Temmerman et al 2007, Schwarz et al 2018) As these feedback loops only occur after a critical biomass/density has been exceeded (Bouma et al 2009a), individual marsh propagules such as seedlings or clonal fragments face establishment barriers (Bouma et al 2009b, 2016, Balke et al 2014, 2016, Hu et al 2015, Yuan et al 2020)
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