Thinning the thickets: Foraging of hardy cattle, sheep and goats in green alder shrubs

Abstract

Green alder shrubs Alnus viridis increasingly overgrow European mountain pastures but hinder natural forest succession. This nitrogen‐fixing, autochthonous invasive species has numerous negative effects including the loss of biodiversity and landscape aesthetic, eutrophication of soils and downstream waters, and greenhouse gas emission. Over centuries, A. viridis encroachment was impeded by grazing livestock, particularly goats. However, in modern agriculture, livestock numbers decreased on remote mountain pastures and goat farming became unprofitable. A grazing experiment tested if hardy breeds of the more economically attractive livestock species, cattle and sheep can replace goats as A. viridis antagonists. On a subalpine pasture heavily encroached by A. viridis, space use and debarking (bark foraging) by Dexter cattle, Engadine sheep and Pfauen goats were analysed using GPS tracking and vegetation mapping. Dexter cattle used space least evenly (Camargo evenness: cattle = 0.39; sheep = 0.52; and goats = 0.47) and preferred flat slopes and open pastures. They spent least time foraging in A. viridis stands (relative presence while foraging: cattle = 0.55; sheep = 0.76; and goats = 0.80). Dexter cattle did not debark any A. viridis, but damaged shrubs by trampling. Engadine sheep visited A. viridis stands nearly as often as goats, but preferred flat slopes, short vegetation and shrub edges more clearly than goats. This sheep breed debarked significantly more A. viridis branches (average 244 branches per paddock; 7.4% of all A. viridis branches) than goats (45; 0.8%). Goats preferred mountain‐ash shrubs Sorbus aucuparia covering only 2% of the shrub layer. Synthesis and applications. Green alder shrubs, controlled by goats traditionally, overgrow valuable mountain pasture ecosystems today. Cattle, kept instead of goats, may slow down but not hinder shrub encroachment, because they avoid shrub stands and do not debark green alder. However, this study is the first to show that Engadine sheep are even better suited for green alder clearance than goats. Moreover, if management goals include forest re‐establishment, Engadine sheep outperform goats, because they debark green alder (which hinders forest regeneration), but do not destroy elderberry—a valuable forest pioneer. Hardy breeds are an important tool to maintain biodiverse, open pastures, restore natural mountain forests and mitigate the negative environmental effects of shrub encroachment.

Diversification increases the resilience of European grassland‐based systems but is not a one‐size‐fits‐all strategy

“…Consequently, Highland cattle reduce workload needed for pasture management. Similar findings were presented for low‐productive Engadine sheep, consuming green alder shrubs in subalpine‐systems most efficiently and thereby hindering shrub encroachment and its numerous negative environmental effects (Pauler et al, 2022). Under low‐nutritive value diet, so‐called low‐productive cattle gain more weight than high‐productive cattle (Pauler, Isselstein, Berard, et al, 2020).…”

Foraging behavior of Highland cattle in silvopastoral systems in the Alps

“…For instance, Alberes cattle can feed year-round with a predominantly woody diet in Mediterranean forests of the Pyrenees (Bartolomé et al 2011 ). In the Alps, Dexter (Pauler et al 2022b ) and Highland (Pauler et al 2020 ; Svensk et al 2022 ) cattle are acknowledged to feed on woody species as well. The ability of certain livestock species and breeds to consume woody plants is linked with microbial populations in their rumen able to detoxify secondary metabolites and degrade lignin.…”

Use of Molasses-Based Blocks to Modify Grazing Patterns and Increase Highland Cattle Impacts on Alnus viridis-Encroached Pastures

“…Because A. viridis predominantly establishes on steep slopes and marginal locations, with few roads, the mechanical removal of this shrub species can be technically difficult, expensive and time consuming. One alternative and sustainable nature-based solution to counteract shrub encroachment could be the use of targeted grazing (Elias and Tischew, 2016;Elias et al, 2018;Pauler et al, 2022). Meisser et al (2014) monitored the grazing behavior of Hérens cows in A. viridis dominated pastures and showed that they did spend time in half or more encroached areas, despite their usual preference for open areas.…”

“…Nevertheless, some robust livestock species and breeds have higher resistance to tannins, with ruminal bacterial populations that can better degrade lignified material, allowing them to feed on shrubs and digest their leaves (Berry et al, 2002;Marques et al, 2017). For instance, previous studies have shown that sheep and goats can efficiently feed on woody plants and significantly reduce their cover (Iussig et al, 2015;Álvarez-Martínez et al, 2016;Pauler et al, 2022). Some cattle breeds can also feed on shrub species (Zehnder et al, 2016;Pauler et al, 2019).…”

“…Previous studies have demonstrated their capacity to reduce woody plant species cover over time, with a turnover in plant diversity (Pauler et al, 2019(Pauler et al, , 2020a. In addition to the direct grazing of the leaves, Highland cattle are also able to damage shrub branches and trunks thanks to their long horns (Svensk et al, 2021), even if they do not directly debark trees as some robust goat or sheep breeds do (Pauler et al, 2022). Recently, Svensk et al (2021) showed that Highland cattle can graze on steep montane pastures characterized by high A. viridis cover and associated low forage quality vegetation in the understory.…”