Effect of different rotational grazing start time on plant community characteristics in desert steppe in Ningxia

The reasonable rotational grazing start time had important effects on scientific utilization of desert steppe. In the present paper, plant community characteristics and edible forage nutrients of desert steppe in Ningxia with different rotational grazing start times were studied. The results showed that rotational grazing start time had little influence on species composition of desert steppe after two years of grazing. The plant density in grassland with early rotational grazing was higher than that in grassland with late start rotational grazing, however, the coverage and aboveground biomass had opposite performance. With the delay of rotational grazing start time, the important value of Stipa breviflora, Lespedeza potaninii, Leymus secalinus and Conrolulus ammannii increased, whereas that of Cleistogenes squarrosa decreased, Cynanchum komarovii has no significant difference in different start rotational grazing times. The density, coverage and aboveground biomass of above species had different response to rotational grazing start time. Rotational grazing improved plant species diversity. The plant species dominance of late rotational grazing region was lower than that of early rotational grazing region, however, the uniformity and diversity had opposite performance. With the delay of rotational grazing start time, animal feed rate and forage crude protein content gradually decreased and crude fiber content increased. These results suggested that rotational grazing with fixed time and sequence will increase the heterogeneity of grassland vegetation so that the rotational grazing time and sequence should have appropriate adjustments based on vegetation conditions.