Moderate livestock grazing is often identified as a useful management tool for sustaining biodiverse grassland communities and has long been practiced in Scandinavian mountains. Despite of a growing number of studies focusing on grazing effects along elevational gradients worldwide, there is still limited knowledge of how grazing intensity varies over time and how it affects plant communities on species and functional group level. Moreover, the majority of existing studies are conducted in enclosures with controlled stocking rate, while free-range grazing with a highly varied livestock number is the common practise in Scandinavia. Therefore, the aim of this study was to quantify free-range grazing intensity over the growing season along an elevational gradient and to evaluate how grazing affects plant communities on species, functional group and community level. In order to quantify grazing intensity, we conducted a grazer exclusion experiment along an elevational gradient in Norway in the growing season of 2019. We quantified grazing intensity as the difference in dry above-ground biomass between grazed and caged plots and analyzed plant composition on community and functional group level as well as recorded species-specific grazing damage and potentially influential abiotic factors. To capture the effects of temporal variation in grazing we also relocated caged and grazed plots in four-week intervals during the growing season. We demonstrated that grazing intensity gradually decreased with elevation and elevation explained 77% of the variation in grazing among sites. Lower grazing intensity at high elevation is likely related to decreasing plant productivity and differences in plant community composition along the gradient. Grazers reduced the biomass of graminoids and forbs in the intensively grazed lower sites. Grazing damage varied among sites for five of the eight most commonly grazed plant species, which was mainly driven by a higher grazing damage in the intermediate site (900m a.s.l.). Selective grazing was observed in three sheep-dominated study sites. Grazing intensity did not significantly vary during the growing season at any site, possibly due to weak temporal effects of an overall short growing season. In accordance with other studies, we demonstrated that grazing homogenized plant community composition in actively grazed sites that were relatively species rich. To conclude, livestock grazing can help maintain biodiverse semi-natural grasslands, yet when grazing is applied as a management tool in the mountainous landscapes, we suggest considering that grazing intensity, and therefore its effects, will vary with elevation.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-415468 |
| Date | January 2020 |
| Creators | Petrauskaitė, Ieva |
| Publisher | Uppsala universitet, Institutionen för biologisk grundutbildning, University of Bergen |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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