Impact of cattle grazing on alpine mires as recorded by peat properties and diatoms: Insights for a sustainable conservation

Peatlands are highly vulnerable and play a crucial role in carbon sequestration and biodiversity conservation. Cattle grazing and trampling contribute to peatland degradation and pose a significant threat to habitat integrity and biodiversity, especially in the southeastern Alps, where mires are habitats at the southern margin of their global distribution. The main objective was to examine the impact of grazing on the physical, chemical, and biological characteristics of peat, with a focus on diatoms to gain insights for a sustainable management and conservation of these habitats. Seven 50-cm deep peat cores were collected from mires located in the Adamello-Brenta Nature Park (Trentino, Italy) along a grazing-induced disturbance gradient. Results revealed that grazing, primarily affected the upper 15 cm of the peat resulting in increased density, reduced water content, elevated nitrogen concentration from cow manure. Over 200 diatom taxa were recorded and several of them fall under threat categories in the Red List for central Europe. Highly-grazed areas exhibited a higher percentage of eutraphentic species, linked to increased nutrients from cattle manure, and aerial species, which survive in environments with unstable water availability. This research provides useful indications on the effects of grazing in terms of biogeochemical cycles and nature/habitat conservation.