The relative contribution of grazing and climate variation on vegetation change in alpine area

Abstract

For more than a decade, a warming and grazing experiment has been carried out in the alpine area of the Faroe Islands. Ten Open Top Chambers (OTCs) were placed inside an enclosure with control plots both inside (CtrlE) and outside (CtrlO) the enclosure. The difference in vegetative growth of the two species Salix herbacea and Polygonum viviparum and graminoids were monitored as well as the frequencies of the four functional types: herbs, graminoids, woody species and bryophytes. It was found that warming generally increased leaf length by around 30% with similar or larger increases in photosynthetic leaf area. Grazing reduced leaf length by around 30% for graminoids and Polygonum viviparum, but only by around 10-20% for Salix herbacea. The changes in frequencies of functional types were most pronounced for bryophytes and woody species during the latter part of the experiment when both grazingexclusion and warming increased the frequencies of bryophytes and decreased the frequencies of woody species. ÚrtakÍ meira enn tíggju ár er kannað, í hvussu stóran mun upphiting og seyðabit ávirka plantu vøkst -ur á 600 metra haedd á Sornfelli. Kanningarnar eru gjørdar í tíggju smáum vakstrarhúsum, ið eru opin í erva (OTC). Tey vóru innan fyri eitt hegn, har royndarøki uttan upphiting (CtrlE) eisini vórðu kannað, umframt eisini royndarøki uttan fyri hegnið (CtrlO). Munurin á vøkstri hjá urtapíli Salix herbacea, aksgrónari bløðkuurt Polygonum viviparum og grøsum og munur á tíð leika av urtum, grøsum, dvørgrunnum og mosum varð kannaður. Fyri gras og aks grógvn -ari bløðkuurt vísti úrslitið sum heild, at blað -longdin øktist umleið 30% við upphiting og mink aði umleið 30% av seyðabiti. Blaðlongdin á dvørgrunnum broyttist á sama hátt, men bara

Sheep grazing in the North Atlantic region: A long-term perspective on environmental sustainability

“…This creates a positive feedback loop for grazing, as more grazing leads to more resources becoming available van der Wal et al 2003). Furthermore, sheep grazing may change bryophyte community composition (Jónsdóttir 1984;Austrheim et al 2007) and reduce abundance of mosses (Jóns-dóttir 1991; Magnússon and Magnússon 1 992;Fosaa 2015) and also, in some cases, lichens (Mysterud and Austrheim 2008). In the Icelandic highlands, for example, heavy grazing has eliminated palatable, grazing-intolerant species (Jónsdóttir 1984) in extensive areas, causing slow responses to cessation of grazing (Jónsdóttir et al 2005).…”