Materials and methods
Study region and study
sites
In July 2021, at the peak of the
growing season, we surveyed 43 field sites spanning a latitudinal
gradient of 26.95-38.60°N and a longitudinal gradient of 96.40-103.41°E
(Figure 1). Our survey covered the full latitudinal range for grasslands
occurring in the Eastern Qinghai-Tibetan Plateau. At the survey sites,
the mean annual temperature and mean annual precipitation ranged from
-3.0 to 9.3°C and from 250 to 1,350 mm, respectively. This represents a
significant climatic gradient, capable of driving variation in resident
plant communities (Zhang et al. , 1988).
Sampling sites were situated far from any cities and can be considered
representative areas for natural vegetation. The sites were chosen based
on the following criteria: (i) at least 500 m away from major roads;
(ii) under pristine or unmanaged conditions without visible signs of
domestic animal grazing, grass/wood collection, human-engineered
restoration plantings, and/or human infrastructure. We recorded
geographical information (i.e. , longitude, latitude and altitude)
for each sampling site, before establishing four 0.5 × 0.5 m quadrats at
the corners of a 50 × 50 m square. The quadrats were used to survey
plant community composition, the aboveground biomass and herbivory of
each species present, and
the associated soil properties.
Plant specimens were sorted to species level and identified using the
“Flora of China” (Wu et al., 2013). Samples from each species were
clipped from the quadrats for herbivory assessments and weighed (to
determine the aboveground biomass) after drying at 65°C for 72 h to a
constant weight.