Responses of plant communities, species composition, and diversity to mowing and long-term grazing in the Songnen meadow steppe

To understand the effects of different utilization patterns of grassland resources on the species composition and diversity of different plant communities in the Songnen meadow steppe, this study investigated and analyzed two typical communities, Leymus chinensis and Arundinella hirta, under mowing and long-term grazing on the western Songnen Plain. We explored the effects of these two utilization patterns on the community composition of plant species, importance value, life form, quantitative characteristics and diversity. The results showed that there were 18 and 21 L. chinensis community species under mowing and long-term grazing, respectively, and the proportion of poaceae plants was the largest under both conditions at 33.3% and 45.45%, respectively. There were 39 and 32 A. hirta community species under mowing and long-term grazing, respectively, and the proportion of gramineous plants was 23.1% and 21.9%, respectively. Long-term grazing increased the proportion of hemicryptophytes in the L. chinensis community and therophytes in the A. hirta community, respectively, but it decreased the proportion of hemicryptophytes in the A. hirta community. Fine herbage species provided the largest variety in forage value in both communities under the two utilization patterns, accounting for 58.76% (L. chinensis mowing), 53.33% (L. chinensis long-term grazing), 46.56% (A. hirta mowing), and 46.63% (A. hirta long-term grazing), respectively. Long-term grazing significantly decreased the coverage, height, and biomass of the two plant communities (P < 0.05). Compared with mowing, the Shannon-Wiener and Simpson diversity indexes of long-term grazing plant communities showed an increasing trend. The Sörensen similarity index of both communities was higher under long-term grazing than under mowing. The similarity of plant species between the two communities was high, but the Cody index was higher under mowing. In addition, changes in the species composition of both communities were greater under mowing. These results show that mowing and grazing have different effects on the composition and diversity of different plant communities in the Songnen meadow steppe. Reasonable and appropriate utilization and protection measures will be conducive to the sustainable use of grassland resources.