Vegetation change and effects of cattle grazing in the transition mire "Burgmoos” = Vegetationsveränderungen und Einfluss der Beweidung im Zwischenmoor "Burgmoos”
Küchler, Helen ; Grünig, Andreas ; Hangartner, Rolf ; Küchler, Meinrad
In: Botanica Helvetica, 2009, vol. 119, no. 2, p. 95-104
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- Mires are highly threatened ecosystems in the lowlands of Central Europe. Reduced water levels and eutrophication promote shrub encroachment and the expansion of tall species, such as common reed (Phragmites australis). In the "Burgmoos”, a Swiss mire of national importance, attempts have been made to reverse these developments through cattle grazing in parts of the mire area. To monitor overall vegetation change and to assess the influence of grazing (which started in 2004), the vegetation was surveyed in 1995, 2001 and 2007. Ecological indicator values of the vegetation changed considerably between 1995 and 2007: mean indicator values for nutrients and soil pH increased in 80 and 72% of the relevés, respectively, while mean indicator values for moisture, humus and light decreased in 81, 86 and 76% of the relevés, respectively. Plant species from bogs, transition mires and fens decreased, while trees, pasture species and P. australis increased. Grazing had a weak effect on P. australis and did not prevent an increase in abundance of this species. The abundance of transition mire species was maintained in the grazed area between 2001 and 2007, whereas it continued to decrease in the ungrazed areas. This positive effect of grazing was, however, compensated by several adverse effects: In the non-forested parts of the mire, grazing accelerated the increase of nutrient indicator values, the decrease of bog species and the increase of pasture species. We conclude that grazing has not been effective in preventing undesirable vegetation changes in the Burgmoos