A warning call from mires of the Southern Alps (Italy): Impacts which are changing the bryophyte composition

Abstract

In the Alps, mires, ranging from fens to bogs, are rare habitats mainly restricted to high elevation ranges where anthropogenic pressures are relatively low. However, they are threatened by multiple impacts, among which intensive cattle grazing and draining predominate. In particular, overgrazing effects are still poorly explored and we urgently need an assessment of the conservation status of these sensitive habitats in high elevation grazed areas. In this study, 85 small and large mires (min-max 0.12–8.69 ha) were surveyed in the Southern Alps using bryophytes as indicators of impacts and recording environmental descriptors to interpret both the ecology of the species and the environmental impacts. Results revealed a high diversity of bryophytes (77 taxa, 25 of which were Sphagnum) and allowed to clarify the environmental factors affecting their distribution (elevation, pH, conductivity, and depth to the water table), and the main threats. In particular, cattle trampling was the most impacting factor which decreased both the variability of bryophyte composition and the occurrence of rare species. Drainage was the second most important disturbance, the effects of which were interpreted along the dry-wet gradient of the species preference. Only 35 % of the mires were pristine thus posing concern on the effectiveness of local management policies to protect these rare and sensitive habitats in the Southern Alps.