Temporal changes in grazing intensity and herbage quality within a Swiss fen meadow
Güsewell, Sabine ; Pohl, Mandy ; Gander, Antoine ; Strehler, Catherine
In: Botanica Helvetica, 2007, vol. 117, no. 1, p. 57-73
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- Güsewell S., Pohl M., Gander A. and Strehler C. 2007. Temporal changes in grazing intensity and herbage quality within a Swiss fen meadow. Bot. Helv. 117: 57 - 73. Grazing is a possible tool for conservation management in wetlands, but a frequent problem is spatial variation in grazing intensity, which may promote the degradation of the vegetation. Temporal changes in grazing patterns may reduce this problem by leading to a more homogeneous overall use of the area. In a lakeshore wetland (2.8 ha) grazed by Scottish Highland cattle from May till September, we studied how the grazing of nine vegetation types changes seasonally and between years, and how this is related to the quantity and quality of the herbage. We observed cattle activity weekly throughout two grazing periods, determined the biomass and nutrient concentrations of the vegetation, analysed dung samples, and carried out clipping experiments to assess shoot regeneration after grazing. The annual grazing intensity varied seven-fold among vegetation types, and this pattern was closely similar in both years. In several vegetation types, however, grazing intensity changed seasonally. Cattle first grazed tall grassdominated vegetation (Phragmition, Phalaridion), which had the most digestible and nutrient-rich herbage, but the poor regeneration of dominant species forced the cattle to then graze small-sedge dominated, nutrient-poor fen vegetation (Caricion davallianae). These temporal changes in grazing patterns slightly reduced the spatial variation in grazing intensity. To take advantage of this effect, relatively long grazing seasons are preferable to shorter ones. Four years of grazing reduced the above-ground biomass production and nutrient concentrations of several vegetation types. Therefore, years without grazing may be needed to prevent a degradation of palatable plant communities with low grazing tolerance