Svensk, Mia (2023). Targeted grazing of robust livestock for the restoration of green alder-encroached pastures. (Thesis). Universität Bern, Bern

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Abstract

Throughout the last decades, the reduction of agro-pastoral activities in subalpine areas has generated profound landscape modifications, with important shrub-encroachment processes over former pastures, particularly by Alnus viridis (Chaix., DC), which is the most expanding shrub species across all Central Europe. The main goal of this doctoral project was to investigate ecological dynamics in A. viridis-encroached pastures under the challenge of Highland cattle grazing, a robust livestock species. The aims were to assess i) the chemical composition and digestibility of A. viridis leaves; ii) the feeding behaviour of Highland cattle; iii) the main factors impacting Highland cattle distribution patterns; iv) the effect of strategically placed attractive points on Highland cattle spatial distribution and v) the potential of Highland cattle to translocate the nitrogen in excess from A. viridis encroached areas to adjacent open pastures. From 2019 to 2023, Highland cattle herds equipped with GPS collars were placed in A. viridis-encroached paddocks across Switzerland and Italy. Botanical surveys were carried out and A. viridis leaves, the herbaceous vegetation and Highland cattle dung pats were sampled throughout the grazing seasons, and analysed in laboratory to assess their composition. Visual observations of the cows were carried out to record their grazing behaviour, and their spatial distribution was analysed using the GPS positions. Attractive points were placed during the grazing season of 2020 in highly encroached areas, and impacts on the vegetation were recorded before and after grazing. Estimations of the nitrogen fluxes in each paddock were made using the nitrogen content of the samples and GPS data. Results showed that A. viridis leaves are a valuable forage resource for robust livestock, above all in June and July, and help mitigating methane emission from cows. Moreover, Highland cattle actively foraged on A. viridis, which consumption increased with its abundance. Highland cattle were also able to graze in harsh conditions, in steep slopes and a in highly encroached areas of the paddocks. Attractive points in the form of molasses-based blocks were very effective at luring Highland cattle in the denser parts of the paddocks, which maximized their effect on A. viridis shrubs and the surrounding vegetation through grazing, trampling and mechanical damages. Finally, Highland cattle grazing created an active nitrogen translocation from A. viridis encroached areas to adjacent open pastures. The present thesis showed how Highland cattle can become an efficient management tool to counteract A.viridis encroachment, as they provide significant pressure on the shrub that could lead to a progressive restoration of former grassland vegetation in the long-term.

Item Type:	Thesis
Dissertation Type:	Single
Date of Defense:	9 October 2023
Subjects:	500 Science > 580 Plants (Botany)
Institute / Center:	08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS)
Depositing User:	Hammer Igor
Date Deposited:	27 Nov 2023 15:22
Last Modified:	30 Mar 2024 20:15
URI:	https://boristheses.unibe.ch/id/eprint/4732

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