4.2 Response of shrub species to stocking rate
With increasing duration of grazing history, the cumulative above-ground
standing crop of shrubs and grasses increased under low stocking rates
(CK, LG), while under high stocking rates (MG, HG) herbaceous plants
gradually dominated the plant community. This is closely related to the
palatability of grasses and the selective feeding habits of grazing
livestock (Molyneux and Ralphs, 1992; Dulamsuren et al., 2008; Staver et
al., 2009). Shrubs such as Artemisia frigida , Kochia
prostrata , Caragana microphylla and Ceratoides latenshave good palatability in the desert steppe (Yan, 2019), and all are
favored by sheep. Therefore, in desert steppe, which has sparse
vegetation cover and relatively poor species composition (Han et al.,
2007), shrubs are more likely to be consumed by sheep under high
stocking rates, leading to their gradual disappearance in the plant
community. In this study, the above-ground standing crop of shrubs
decreased with increasing stocking rate, which is mainly due to the
influence of Artemisia frigida . The change in Artemisia
frigida was consistent with those reported by Kemp et al. (2018), who
found a significant increase in Artemisia frigida under long-term
non-grazing and light grazing in an Inner Mongolian desert steppe. Kemp
et al. (2018) suggested that Artemisia frigida has good
palatability, and that sheep preferentially consumed Artemisia
frigida under high stocking rates. Wang et al. (2018) researched the
population characteristics of Caragana microphylla across a
stocking rate gradient in desert grassland and showed that the height
and cover of Caragana microphylla decreased significantly with
increasing stocking rate, which indicated that livestock consumption
strongly inhibited the growth of Caragana microphylla . The height
of shrubs gradually decreased with increasing stocking rate, while the
quantitative characteristics of individuals (except for the height ofKochia prostrata , Caragana microphylla andCeratoides latens ) were highest under LG, indicating that light
grazing can inhibit the apical dominance of shrubby plants (Christie et
al., 2014).