The effect of cattle and sheep grazing on salt-marsh vegetation at Skallingen, Denmark

Published source details Jensen A. (1985) The effect of cattle and sheep grazing on salt-marsh vegetation at Skallingen, Denmark. Vegetatio (now Plant Ecology), 37-48.
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This study is summarised as evidence for the following.

	Action	Category
	Use grazing to maintain or restore disturbance: brackish/salt marshes Action Link
	Exclude or remove livestock from historically grazed brackish/salt marshes Action Link
	Exclude or remove livestock from historically grazed brackish/salt marshes Action Link

Use grazing to maintain or restore disturbance: brackish/salt marshes

A controlled study in 1972–1978 in a salt marsh in Denmark (Jensen 1985) reported that an area in which grazing was maintained had identical plant species richness to an area from which livestock were excluded, but had lower vegetation cover. Statistical significance was not assessed. After approximately six years, the same seven plant species were present in the grazed and exclusion areas. However, six of these species had lower cover in both grazed plots – including saltmarsh grass Puccinellia maritima (grazed: 72–82%; exclusion: 84–92%) and sea purslane Halimione portulacoides (grazed: <1%; exclusion: 8–17%). Accordingly, both sampling plots within the grazed area had lower overall vegetation cover than both sampling plots within the exclusion area. This was true for cover including overlapping vegetation (grazed: 81–89%; exclusion: 130–145%) and for cover as the inverse of bare ground (grazed: 73–83%; exclusion: 95–98%). Methods: In spring 1972, an area of historically grazed coastal salt marsh was fenced to exclude livestock. Grazing was continued in the rest of the salt marsh (with at least 0.5 sheep/ha and 0.5 cattle/ha, May–October). In August 1978, the cover of every plant species and bare ground were recorded in two plots in the grazed and exclusion areas (50 point quadrats with 10 pins/plot).

(Summarised by: Nigel Taylor)
Exclude or remove livestock from historically grazed brackish/salt marshes

A controlled study in 1972–1978 in a salt marsh in Denmark (Jensen 1985) reported that an area fenced to exclude livestock had identical plant species richness to an area that remained grazed, but greater vegetation cover. Statistical significance was not assessed. After approximately six years, the same seven plant species were present in the exclusion and grazed areas. However, six of these species consistently had greater cover in the exclusion area – including saltmarsh grass Puccinellia maritima (exclusion: 84–92%; grazed: 72–82%) and sea purslane Halimione portulacoides (exclusion: 8–17%; grazed: <1%). Accordingly, both sampling plots within the exclusion area had greater overall vegetation cover than both sampling plots within the grazed area. This was true for the sum of the cover of each species (exclusion: 130–145%; grazed: 81–89%) and for cover as the inverse of bare ground (exclusion: 95–98%; grazed: 73–83%). Methods: In spring 1972, an area of historically grazed coastal salt marsh was fenced to exclude livestock. The surrounding marsh remained grazed (by at least 0.5 sheep/ha and 0.5 cattle/ha, May–October). In August 1978, the cover of every plant species and bare ground were recorded in two plots in the fenced and grazed areas (50 point quadrats with 10 pins/plot). This study used the same marsh as [4], but a different experimental set-up.

(Summarised by: Nigel Taylor)
Exclude or remove livestock from historically grazed brackish/salt marshes

A before-and-after study in 1971–1978 in a salt marsh in Denmark (Jensen 1985) reported that after installing fences to exclude livestock, plant species richness was stable but there were small changes in vegetation composition and cover. Statistical significance was not assessed. The study plot contained nine plant species both before and approximately six years after livestock exclusion. Eight of the species were the same (one species went extinct and one new species colonized). Overall vegetation cover increased slightly. This was true for the sum of the cover of each species (before exclusion: 176%; six years after: 180%) and for cover as the inverse of bare ground (before exclusion: 92%; six years after: 98%). Changes in cover of individual species included increases for red fescue Festuca rubra (before: 55%; after: 72%) and sea purslane Halimione portulacoides (before: 22%; after: 61%) and a decrease for saltmarsh grass Puccinellia maritima (before: 34%; after: 3%). Methods: In spring 1972, a 40 x 60 m area of coastal salt marsh was fenced to exclude livestock. Previously, the marsh had been grazed by 0.5 sheep and 0.5 cattle/ha, May–October. The cover of every plant species and bare ground were surveyed in a permanent plot, using point quadrats, before (August 1971) and after (August 1978) exclusion. This study used the same marsh as [3], but a different experimental set-up.

(Summarised by: Nigel Taylor)