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Short-term impact of sheep grazing on salt-marsh vegetation succession in a newly created salt-marsh site
Erfanzadeh, R.; Milotic, T.; Pétillon, J.; Maelfait, J.-P.; Hoffmann, M. (2009). Short-term impact of sheep grazing on salt-marsh vegetation succession in a newly created salt-marsh site, in: Erfanzadeh, R. (2009). Spatio-temporal aspects of early vegetation succession in a recently restored salt-marsh ecosystem: a case study of the IJzer estuary (Belgium). pp. 75-94
In: Erfanzadeh, R. (2009). Spatio-temporal aspects of early vegetation succession in a recently restored salt-marsh ecosystem: a case study of the IJzer estuary (Belgium). PhD Thesis. Ghent University. Faculty of Sciences. Department of Biology. Terrestrial Ecology Unit: Gent. xii, 206 incl. Appendices pp., more

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Keywords
    Forages; Habitats; Intertidal environment; Management; Succession (ecological); Elymus athericus (Link) Kerguélen [WoRMS]; Marine

Authors  Top 
  • Erfanzadeh, R.
  • Milotic, T.
  • Pétillon, J.
  • Maelfait, J.-P., more
  • Hoffmann, M., more

Abstract
    In this paper, the effect of three winter seasons of sheep grazing on cover, composition and species richness of vegetation, Elymus athericus expansion and forage quality of saltmarsh species were studied. Four zones were selected: three in real salt-marsh habitat (low, intermediate and high levels) and the fourth in the transition between salt-marsh and sand dune habitat. In each of the three salt-marsh zones, one site was selected and two sites were designated in the transitional zone. Half of each site was excluded from grazing (so-called exclosures) all year round, while the other half was accessible to sheep from mid-August until mid-June (enclosure areas). At each zone, 10 plots (2m × 2m) were established: five within exclosure and five within enclosure sites. In all plots, the cover of all species was estimated in the growing season in 2005 (initial state) and 2007 (state after two years of grazing). In addition, a total of 1516 quadrates (50cm × 50cm) were used to harvest the biomass of species to estimate the forage quality variation during the grazing period inside the plots. The forage quality variables were the percentages of crude protein, acid detergent fibre and neutral detergent fibre. The data of the cover of dominant salt-marsh species, species richness, total cover, plant composition and forage quality parameters are compared between exclosure and enclosure plots and between two sampling years (2005 and 2007) using repeated measurements (general linear model) separately for each zone. The results showed that after three years of plant succession, sheep grazing had a positive influence on plant richness on the high part of the salt-marsh, a negative effect in the transitional zone and no effect in the other zones. Grazing had no effect on cover and plant composition. Forage quality parameters were affected by sheep grazing only in the low salt-marsh zone. Limonium vulgare had the highest forage quality andElymus athericus had the lowest. It would appear that grazing with the current intensity and number of grazers would fail to hamper the expansion of Elymus athericus. A higher intensity of mixed sheep-cattle or cattle grazing would be needed to better control this highly prolific species.

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