Pulse grazing by reindeer (Rangifer tarandus) increases
the phylogenetic diversity of vascular plant communities in the
Fennoscandian tundra
Kate Gibson1, Johan Olofsson2, Arne
Ø Mooers1, Melanie J Monroe1,2
1Department of Biology, Simon Fraser University, 8888
University Drive, Burnaby, British Columbia, V5A 1S6, Canada
2Department of Ecology and Environmental Science, Umeå
University, Umeå, 901 87, Sweden
Author for correspondence: Kate Gibson, Department of Biology, Simon
Fraser University, Burnaby, British Columbia, V5A 1S6, Canada;
kfgibson@sfu.ca, ORCiD ID: 0000-0003-3970-6767
Johan Olofsson: johan.olofsson@umu.se, ORCiD ID: 0000-0002-6943-1218
Arne Mooers: amooers@sfu.ca
Melanie Monroe: monroemj.evolution@gmail.com, ORCiD ID:
0000-0003-1692-7938
Abstract
Herbivore grazing is an important determinant of plant community
assemblages. We used data from a multi-year experimental study in
Northern Fennoscandia to analyze the effect of reindeer (Rangifer
tarandus ) grazing on plant community diversity including its
phylogenetic structure. Similar to previous studies on low productivity
ecosystems in this region, we found no effect of grazing on plant
biodiversity and a transition from dwarf shrubs to graminoids with pulse
(i.e. grazed every other year) and press (i.e. grazed every year)
grazing. Interestingly, communities with pulse grazing were more
phylogenetically dispersed than communities with press grazing and
lightly grazed communities. We argue that the indirect effects of
reindeer grazing (e.g. interspecific competition and soil nutrient
availability) may work in opposition of the direct effects (i.e.
physical removal of species) and that the phylogenetic structure of the
resulting community will depend upon the relative strengths of the
direct and indirect effects. This interpretation suggests that the
indirect effects of reindeer grazing in our study region are more
important than the direct effects in driving community assembly for
plant communities that are exposed to pulse grazing. Our results have
important implications for the management of reindeer in Fennoscandia if
pulses of grazing can increase the phylogenetic diversity of plant
communities.
Keywords: biodiversity; community structure; grazing;
herbivore; phylogenetic diversity