Response of Species Diversity and Stability of Typical Steppe Plant Communities on the Mongolian Plateau to Different Grazing Patterns

Grasslands represent a major biome on Earth and play a vital role in ecosystem functioning and dynamics. However, owing to the variations among grassland types, the impact of grazing on plant community diversity and stability remains unclear. This study is based on the typical steppe of the Mongolian Plateau. Field sampling and data analysis were combined to qualitatively and quantitatively investigate the structural characteristics, species diversity, and stability of plant communities under varying grazing intensities, that is, four-season nomadic, two-season rotational, and sedentary grazing (FSNG, TSRG, and SG, respectively). The results indicated that FSNG pastures exhibited the largest number of plant species while FSNG and TSRG pastures exhibited relatively high importance values for the primary dominant species. <i>Carex duriuscula</i>, <i>Chenopodium glaucum</i>, and <i>Cleistogenes squarrosa</i> were prominent in SG pastures, with <i>C. duriuscula</i> having the largest importance value. The mean height, cover, and aboveground biomass of plant communities in FSNG were significantly higher than those in SG (<i>p</i> < 0.05), with no significant difference observed between FSNG and TSRG. FSNG also demonstrated the highest Shannon-Wiener, Simpson, and Pielou indexes. The Shannon-Wiener and Simpson indexes between the FSNG, TSRG, and SG pastures showed significant differences (<i>p</i> < 0.05). Nomadic plant communities displayed positive loosely interspecific traits, suggesting independence and positive succession. Conversely, communities in TSRG and SG exhibited negative correlations and higher instability. The stability analysis ranked community stability as FSNG > TSRG > SG, suggesting that judicious grazing practices could enhance grassland stability. The findings reveal that grazing patterns influence plant community composition and function and that FSNG pastures promote higher species diversity, perennial dominance, and overall stability compared with TSRG and SG pastures.