2.3 Vegetation sampling
In August of 2004 to 2017, we randomly selected 10 quadrats of 50 cm ×
50 cm in each of twelve plots. The standing crop by species was clipped
at the soil surface, oven-dried at 65°C, and weighed. To avoid loss of
information (e.g., if random sampling inadvertently avoided large
individual shrubs), a systematic sampling method with no paddock
replication was used to investigate plant species cover. In August from
2017 to 2019, a 40 m × 40 m sampling area was selected randomly in one
of the three repeat plots of each of the CK, LG, MG and HG treatments,
choosing plots that were similar in terms of topography and species
composition. Four plots were selected to represent the LG, MG, HG plots
in Block I and the CK plot in Block II was selected in order to avoid
edge effects because the CK plot in Block I is located at the edge of
the experiment site (Fig. 1). In this representative sampling area,
there were 77 quadrats of 50 cm × 50 cm (Fig. 2). The quadrat layout was
based on mechanical sampling and cover by species was measured in each
quadrat. Simultaneously, 9-15 individuals of Artemisia frigida ,Kochia prostrata , Caragana microphylla andCeratoides latens (shrubs and semi-shrubs, hereinafter, shrubs)
were randomly selected from the above grazing plots during 2017 to 2019,
and the cover (%), height (cm), the diameter of the base of the cluster
(hereinafter, basal diameter, cm), branch number (individuals), and the
maximum branch diameter (mm) of the four shrub species were determined.
There are five shrub species in experimental region, but Caragana
stenophylla has very small individuals and low density and was not
found under heavy grazing, and therefore was not systematically sampled.