Grazing livestock species composition influences community assembly and determines scale-dependent plant diversity

Grazing by domestic herbivores such as cattle and sheep is a major driver
of grassland biodiversity. However, it remains unclear how livestock
composition influences community dynamics and consequently shapes plant
diversity across scales. Here, we conducted a five-year livestock grazing
experiment with continuous in situ vegetation monitoring by manipulating
the grazing ratio of cattle and sheep in a meadow steppe of northern
China. We found that all mixed grazing of cattle and sheep can
continuously improve the α and β diversity of plants. Analysis of species
dynamics within permanent quadrats showed that the number of newly
colonizing species gradually increased as the proportion of grazing cattle
increased, leading to higher plant α diversity under cattle dominated
grazing (CCS). By contrast, β diversity was higher under sheep-dominated
grazing (CSS). Grazing effects on α diversity were mainly driven by shifts
in community dominance, whereas β diversity responded to both community
dominance and soil nitrogen heterogeneity, the latter playing a stronger
role. Cattle have more potential to produce competitive release and
increase plant α diversity, while sheep are more conducive to creating
soil resource heterogeneity and enhancing environmental filtration, thus
leading to higher plant β diversity. Our study provides important
mechanistic insights into how livestock species composition affects plant
diversity at different scales. This presents a novel perspective on the
need for precision control of grazing livestock composition to optimize
grassland management for diversity conservation.