Regeneration potential of a degraded alpine mountain bog: complex regeneration patterns after grazing cessation and partial rewetting

Abstract

A typical degraded mountain bog in the Swiss Alps was restored by cessation of grazing and partial rewetting. We observed the development of the vegetation over 15 years, starting immediately after the grazing cessation (4 years before rewetting). Cessation of grazing stimulated the recolonisation of bare peat and the establishment of bryophytes. While many typical bog forest species benefited from grazing cessation, the relative abundance of Cyperaceae decreased. Rewetting (in our case: closing ditches with sheet piles and filling them with sawdust) as an additional restoration measure, had a stabilising effect on most environmental factors (e.g. water availability, soil aeration). Furthermore, rewetting had a stabilising effect on stress tolerators and promoted typical species of bog hummocks and hollows. The abundances of species of nearly all groups changed far less dynamically in the rewetted area than in the area that remained drained. It turned out that cessation of grazing as the only restoration measure was insufficient to maintain the vegetation of bogs, whereas the combination of grazing cessation and rewetting directed the site towards the desired development. However, even eleven years after rewetting and 15 years after cessation of grazing, the site had not yet reached a state that was close to an undisturbed alpine bog.

Keywords

• bog
• growth form
• indicator value
• restoration
• species composition