Changes in a salt-marsh vegetation as a result of grazing and mowing - a five-year study of permanent plots

  • Published source details Bakker J.P. (1978) Changes in a salt-marsh vegetation as a result of grazing and mowing - a five-year study of permanent plots. Vegetatio (now Plant Ecology), 77-87.


Schiermonnikoog, one of the Dutch Frisian Islands of northeast Holland, has habitats including salt marshes, sand dunes and pasture. For many years before 1958, young cattle grazed the salt marsh and dunes during the summer. In 1958, a fence was erected limiting grazing to 51 ha of the marsh and a pasture of 9 ha. The grazing area was extended by 32 ha in 1970, and from 1972 onwards young cattle were grazed over the summer. This relatively high grazing intensity was aimed at short-term livestock production rather than grazing for conservation purposes. In 1971 a study was initiated to follow any changes in plant species composition as a result of the renewed grazing. A number of mowing experiments were also included.

Study area: Schiermonnikoog is one of the Dutch Frisian Islands, located in the northeastern part of the Netherlands (53º30'N, 6º10'E). The work was carried out in the Oosterkwelder area, a relatively young salt marsh.

Grazing and mowing: In 1958, a fence was erected limiting grazing to 51 ha (c. 20 ha fertilized twice a year) of the salt-marsh and a pasture of 9 ha. Part of the salt marsh (32 ha), ungrazed from 1958 until 1971) was grazed again from 1972 onwards with young cattle (1.3-1.7 animals/ha, from the end of May until September/October. This grazing intensity is relatively high and was aimed at short-term livestock production rather than grazing for conservation purposes.

In five saltmarsh vegetation types: Festuca rubra/Armeria maritima (red fescue/thrift); sea couch Elytrigia atherica (= pungens; Festuca rubra/Limonium vulgare (red fescue/common sea-lavender); Juncus maritimus (sea rush); and Artemisia maritima (sea wormwood), management treatment were: doing nothing (control); June mowing; August mowing; June and August mowing; all in combination or not in combination with grazing. Their effects on vegetation structure and composition were assessed within permanent plots (2×2 m) each year (1971-1974).

During the reported period (1971–1975; monitoring is ongoing) for each vegetation type, changes were apparent but responses to treatments varied. Changes in the F.rubra/Armeria maritima vegetation were small and gradual under all treatments. Changes in the Artemisia maritima, F.rubra/L.vulgare and J.maritimus vegetation types were pronounced under the grazing treatments, the changes being abrupt and especially apparent in the third and fourth years. The E.pungens-dominated vegetation showed large changes under all treatments, except the control, and changes particularly occurred in the first and second years.

F.rubra/Armeria maritime and E.pungens showed establishment and increase of Saginion maritimae (sea pearlwort Sagina maritima-dominated) elements, indicating a greater openness of, and shorter, vegetation. Changes were small in the F.rubra/Armeria maritima vegetation and only occurred under grazing and mowing in combination. Changes in the E.pungens vegetation were large under all treatments except the control.

F.rubra/L.vulgare and J.maritimus showed a tendency towards development of P.maritima elements and Artemisia maritima to a Puccinellio-Spergularion maritimae (saltmarsh grass-sea pearlwort) vegetation type. In all three of these vegetation types (i.e. Artemisia maritima, F.rubra/L.vulgare and J.maritimus) changes were rather large, especially under grazing treatments.

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