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.