Coastal Meadow Vegetation Following a Century of Shielding Behind a Dike

• Published in: Estuaries and coasts Vol. 44; no. 8; pp. 2087 - 2099
• Main Authors: Andersen, Line Holm, Knudsen, Jeppe Storgaard, Sørensen, Thomas Bo, Skærbæk, Anna Sofie Krag, Bahrndorff, Simon, Pertoldi, Cino, Trøjelsgaard, Kristian, Bruhn, Dan
• Format: Journal Article
• Language: English
• Published: New York Springer Science + Business Media 01.12.2021; Springer US; Springer Nature B.V
• Subjects: Coastal Sciences; Dikes; Earth and Environmental Science; Ecology; Embankments; Environment; Environmental conditions; Environmental factors; Environmental Management; Environmental protection; Europe; Flooding; Freshwater & Marine Ecology; Habitats; Halophytes; meadows; ORIGINAL PAPER; Plant communities; Plant cover; Plants; salinity; Salt marshes; Saltmarshes; Shielding; soil; Species richness; Storms; Tidal floods; total nitrogen; Vegetation; Vegetation cover; Water and Health; Europe; dike; species richness; brackish marsh; Biodiversity; Corine biotypes; salt marsh
• ISSN: 1559-2723; 1559-2731
• DOI: 10.1007/s12237-021-00923-4

It is still common practice in Europe to dike salt marshes for agricultural use. This impacts both the vegetation and physical environment of the marsh. We studied the plant community, environmental conditions, and determined correlations between vegetation cover and diversity with environmental factors on an enclosed marsh, which has been behind a dike since 1890. Vegetation data from both salt marshes without dikes and fresh meadows are routinely sampled by the Danish Environmental Protection Agency and were here used to assess whether the plant community of the shielded marsh resembled that of either salt marshes or fresh meadows. The century-long elimination of tidal and storm flooding has resulted in low salinity levels (0.4–5.13 ppt), low available P (0.36–4.90 mg/100 g soil), and high total N (0.68–28.82 g/kg). The plant community of the shielded marsh demonstrated a mean species richness (11.4) similar to that of other salt marshes but was no longer characterized by the same composition of halophytes (ANOSIM, p < 0.001). However, despite the century-long shielding the vegetation does not resemble that of the nearby fresh meadow community (ANOSIM, p < 0.001). Therefore, prohibiting tidal floodings by dikes does not protect the salt marsh habitat but instead results in a habitat that contains both halophytes and glycophytes.