Sampling protocol
All NutNet sites followed standard sampling protocols. A 1×1m subplot
within each 5×5 m plot was permanently marked and sampled annually at
peak biomass. The number of species, species identity, and their covers
were recorded. Species cover (%) was estimated visually for all species
in the subplots. Aboveground biomass was measured adjacent to the
permanent subplot, by clipping all aboveground biomass within two 1 ×
0.1 m strips (in total 0.2 m2), which were moved each
year to avoid resampling the same location. For shrubs and subshrubs
occurring in strips, we collected all leaves and current year’s woody
growth. Biomass was dried at 60 °C (to constant mass) before weighing to
the nearest 0.01 g. Dried biomass was multiplied by 5 to estimate grams
per square meter. At some sites with strong seasonality, cover and
biomass were recorded twice per year to include a complete list of
species and follow typical management procedures at those sites. For
those sites, the maximum cover for each species and total biomass were
used in the following analyses. The taxonomy was adjusted within sites
to ensure consistent naming over time. Specifically, when individuals
could not be identified as species, they were aggregated at the genus
level but referred to as “species” for simplicity.