Abstract
Green alder (Alnus viridis) is a shrub species that has expanded over former pastures in Central Europe due to land abandonment, leading to negative agri-environmental impacts, such as a reduction in forage yield and quality and an increase in nitrate leaching. Robust livestock breeds such as Highland cattle could be used to control A. viridis encroachment. The objectives of this study were to investigate the impact of A. viridis encroachment on plant community composition and diversity and to map the spatial distribution of Highland cattle in A. viridis-encroached pastures. During the summer of 2019, three different Highland cattle herds were placed along an A. viridis encroachment gradient. A total of 58 botanical surveys were carried out before grazing to assess plant community composition, pastoral value, and ecological indicator values. The spatial distribution of cattle was studied during the whole grazing period by monitoring six to eight cows equipped with GPS collars in each herd. Plant species associated with higher pastoral values of the vegetation were found in areas with lower A. viridis cover, while highly encroached areas were dominated by a few nitrophilus and shade-tolerant broad-leaved species and by ferns. Cattle spent more time in areas with higher pastoral value but did not avoid areas with high cover of A. viridis, on steep slopes or far from water. These results show that Highland cattle are able to tolerate harsh environmental conditions and that they can exploit A. viridis-encroached pastures. This suggests that they have a high potential to reduce A. viridis encroachment in the long-term.
Highlights
Throughout the last decades, socioeconomic changes have led to a reduction in agropastoral activities in European mountain areas, triggering profound landscape modifications, and widespread natural reforestation and shrub encroachment in former pastures (Estel et al, 2015)
To investigate vegetation features and cattle spatial distribution, three Highland cattle herds were placed in four different A. viridis-encroached paddocks in the Swiss and Italian Alps in the summer of 2019
Four patches in Val Vogna were well distinguished and corresponded to vegetation dominated by dwarf shrubs, such as Vaccinium vitis-idaea, Juniperus nana, and Rhododendron ferrugineum, with low pastoral value (PV) (Figure 1B)
Summary
Throughout the last decades, socioeconomic changes have led to a reduction in agropastoral activities in European mountain areas, triggering profound landscape modifications, and widespread natural reforestation and shrub encroachment in former pastures (Estel et al, 2015). Shrublands cover an area of 679 km in Switzerland, with about. 70% of them dominated by pure stands of green alder [Alnus viridis (Chaix.) D. Encroachment by A. viridis can have several negative agri-environmental impacts: in particular, A. viridis-dominated shrublands have lower plant and animal diversity and forage quality than open grazed areas (Anthelme et al, 2001). A recent study showed that A. viridis encroachment resulted in a rapid decline in plant species richness, with dense A. viridis patches hosting 62% less species than adjacent open pastures (Zehnder et al, 2020). There is high nitrate and dissolved organic carbon leaching from A. viridis shrublands, which results in water pollution, soil acidification, hydrological drawbacks, and gaseous nitrogen losses (Bühlmann et al, 2016; van den Bergh et al, 2018). It is important to find methods that control A. viridis encroachment in order to reverse biodiversity losses and to protect key ecosystem services
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