Sampling
Aboveground plant biomass and plant community composition were sampled
annually during the peak of the local growing season. All aboveground
biomass was clipped in two 0.1 m x 1 m strips. Live (current year’s
growth) and dead (previous year’s growth) biomass were separated, and
live biomass was typically sorted into functional group categories
(e.g., graminoid, forb, legume, fern). All sites recorded total live
biomass. Biomass was dried at 60°C and weighed to the nearest 0.01 g.
The location of the biomass clip plot was moved every year within a
subplot designated for biomass sampling. Community composition was
sampled as percentage cover in a permanent 1 m x 1 m subplot close to
biomass strips. Absolute cover was estimated visually for each species,
so that the summed cover of all species could exceed 100% to most
accurately represent multi-layered grasslands. We excluded non-living
litter and debris, woody species, and non-vascular species such as
bryophytes from the data for this analysis, as these categories were not
consistently accounted for in living herbaceous biomass samples across
sites.