Abstract
AbstractSpartinaspp. (cordgrasses) often dominates intertidal mudflats and/or low marshes. The landward invasion of these species was typically thought to be restrained by low tidal inundation frequencies and interspecific competition. We noticed that the reported soil salinity levels in some salt marshes were much higher than those at the mean higher high water level, which might inhibit the landward invasion of cordgrass. To test this possibility, we transplantedSpartina alternifloraacross an elevational gradient in an invaded salt marsh in the Yellow River Delta National Nature Reserve, where a salt accumulation zone (i.e., salt barren) was previously observed. We found thatS. alterniflorawas significantly inhibited by the salt barren in high marsh regions, although it performed better at upland and low marsh regions. A common garden experiment further elucidated thatS. alternifloraperformed best at low salinity levels and that this species is less sensitive to inundation frequency. Our results indicated that the salt barren inhibited the landward invasion ofS. alterniflorain salt marshes and provided a natural barrier to protect the upland from invasion. Though field observations suggest thatS. alternifloracould propagate along tidal channels, which provide low‐salinity corridors for the dispersal of propagules, natural salt barrens can inhibit the landward invasion ofSpartinain salt marshes. However, artificial disturbances that break the salt barren band in salt marshes (e.g., artificial ditches) might accelerate the invasion ofSpartinaspp. This new finding should alert salt marsh managers to pay attention to artificial ditches and/or other human activities when attempting to controlSpartinainvasion.
Highlights
IntroductionPopulations of non-native Spartina species have been introduced (both deliberately and accidently) to estuaries in Europe, the United States of America, Australia, New Zealand, and Asia
Over recent decades, populations of non-native Spartina species have been introduced to estuaries in Europe, the United States of America, Australia, New Zealand, and Asia
As for other habitats, there was no significant difference in the survival rate of transplanted ramets; their biomass and stem height at upland (Site 1) were significantly higher than in hypersaline regions like high marsh and low marsh, which indicated that S. alterniflora growth was significantly inhibited in low marsh and high marsh regions with increased salinity, whereas it was less inhibited in the upland, characterized by lower soil salinity than in the salt barren areas
Summary
Populations of non-native Spartina species have been introduced (both deliberately and accidently) to estuaries in Europe, the United States of America, Australia, New Zealand, and Asia. Because of their high growth potential and ecological breadth, these non-native species are highly aggressive in new environments, and they frequently become the dominant plant species in tidal mud flats (Callaway and Josselyn 1992, Vasquez et al 2006, Byers and Chmura 2007, Wang et al 2010, Medeiros et al 2013). Native S. alterniflora found along the Atlantic coast of North America was found to grow to heights of >1.0 m near tidal creeks, whereas those found at locations relatively distant from tidal creeks were dwarfed in size (Morris 1980)
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