Vegetation data collection
We sampled the vascular plant vegetation from all the permanent plots in
mid-late July (when most plants were flowering) for each of the years
from 2004-2007. All plots were sampled every year, except for one plot
in 2006 and three plots in 2007 due to inadvertent human disturbance,
for a total of 140 plot-level samples. Sampling was done at the sub-plot
level: the nine sub-plots of each permanent plot were fully sampled for
species presence/absence data. Species were identified based onDen nya nordiska floran (Stenberg and Mossberg 2003); if an
individual plant could not be identified based on what remained it was
not recorded; some plants could only be identified to the genus level
(e.g. Taraxacum sp.) and were recorded as such. In the centre
sub-plot of each permanent plot we sampled relative species abundance
based on plant cover. We used a 50cm x 50cm transparent plexi-glass
table with 100 randomly distributed 4mm-diameter holes: a pin of the
same diameter was lowered through each hole and the number of contacts
the pin had with each species was recorded (see also Olofsson et al.
2001).