Plant species composition data for Saddle Nodal Plots, 1971-ongoing.

To study long-term changes in alpine tundra vascular plant
communities, thirty permanently marked plots were surveyed in 1971.
These same plots were surveyed at twenty, thirty, and forty year
intervals from the initial sampling date; in 1991, 2001, and 2011.
Plots are one by ten meters, divided into ten subplot quadrats, and
marked with rebar. The presence or absence of each vascular plant
species was recorded per plot
(species_composition_vascular_pres_abs.dem.data.csv). The cover was
recorded for each species that appeared in a one meter by ten
centimeter strip at the base of each quadrat within each plot; it was
assumed that this strip was representative of the cover within the
entire quadrat; percent cover was then averaged for each plot
(species_composition_vascular_cover.dem.data.csv). The cover of
non-vascular plants, soil, rocks, and lichens was also recorded within
the strip (other_cover.dem.data.csv). These data have been used to
study the changes in vascular plant communities and cover across
habitats following a moisture gradient on the saddle portion of Niwot
Ridge; these habitats include dry fellfield, dry meadow, moist meadow,
wet meadow, snow bank, and shrub tundra. While we have observed some
changes in species richness and cover in the plots, overall the plant
communities seem fairly stable over time.