The effect of domestic sheep on forage plants of wild reindeer
Domestic herbivores often compete with wildlife for limited resources, and on longer time-scales, grazing may also increase or decrease coverage of important food plants to wildlife affecting the threshold density ...
for when competition can be expected. In Norway, there are growing concerns about the effect of releasing 2.1 million domestic sheep (Ovis aries) for summer grazing into areas hosting wild populations of alpine reindeer (Rangifer tarandus). We quantified the effect of sheep grazing (0, 25 and 80 sheep/km2) on the development in coverage and abundance of plants known to be important in the diet of reindeer during summer (vascular plants) and winter (lichens) within a fully replicated, landscape scale (2.7 km2) experiment. From 2001 to 2005, the sedge, Carex bigelowii, increased while the herb Solidago virgaurea decreased in frequency at high density of sheep relative to controls (both marginally non-significant). There was no marked development in Deschampsia flexuosa, Salix herbacea or Hierarcium alpinum that could be related to sheep grazing intensity. Lichen coverage and height both decreased at high density of sheep from 2002 to 2005. Effects of low grazing intensity were closer to controls than to high grazing intensity. Our study highlights that high sheep grazing intensity induce changes to the plant community that, at the same time, can improve the summer habitat and detriment the winter habitat to reindeer. Many wild reindeer populations are fragmented and may thus be limited by either summer or winter range. The effect of sheep grazing is predicted to vary accordingly. However, currently, we have limited ability to quantify how much this explicitly means in terms of increased or reduced carrying capacity for reindeer.
Title: The effect of domestic sheep on forage plants of wild reindeer; a landscape scale experiment
Authors: Atle Mysterud and Gunnar Austrheim