Data from: Short-term herbivory has long-term consequences in warmed and ambient high Arctic tundra

Climate change is occurring across the world, with effects varying by
ecosystem and region but already occurring quickly in high-latitude and
high-altitude regions. Biotic interactions are important in determining
ecosystem response to such changes, but few studies have been long-term in
nature, especially in the High Arctic. Mesic tundra plots on Svalbard,
Norway, were subjected to grazing at two different intensities by captive
Barnacle geese from 2003–2005, in a factorial design with warming by Open
Top Chambers. Warming manipulations were continued through 2014, when we
measured vegetation structure and composition as well as growth and
reproduction of three dominant species in the mesic meadow. Significantly
more dead vascular plant material was found in warmed compared to ambient
plots, regardless of grazing history, but in contrast to many short-term
experiments no difference in the amount of living material was found. This
has strong implications for nutrient and carbon cycling and could feed
back into community productivity. Dominant species showed increased
flowering in warmed plots, especially in those plots where grazing had
been applied. However, this added sexual reproduction did not translate to
substantial shifts in vegetative cover. Forbs and rushes increased
slightly in warmed plots regardless of grazing, while the dominant shrub,
Salix polaris, generally declined with effects dependent on grazing, and
the evergreen shrub Dryas octopetala declined with previous intensive
grazing. There were no treatment effects on community diversity or
evenness. Thus despite no changes in total live abundance, a typical
short-term response to environmental conditions, we found pronounced
changes in dead biomass indicating that tundra ecosystem processes respond
to medium- to long-term changes in conditions caused by 12 seasons of
summer warming. We suggest that while high arctic tundra plant communities
are fairly resistant to current levels of climate warming, underlying
ecosystem processes are beginning to change. In addition, even short bouts
of intense herbivory can have long-term consequences for some species in
these communities.