Grassland degradation induces high dietary niche overlap between two common livestock: cattle and sheep

Abstract Introduction Diet selection of grazing livestock is one of the critical factors affecting the diversity and composition of plant communities in grasslands, with consequent impacts for ecosystem functioning. Co‐grazing of multiple livestock species could create additive or complementary effects on plant communities due to diet overlap or differentiation among livestock species. However, there is only limited knowledge about diet overlap and differentiation of co‐occurring livestock species and whether or how these diet characteristics change with grassland degradation. Materials and Methods We experimentally test the diets of two commonly co‐occurring livestock species (cattle and sheep) and the dietary niche partitioning/overlap between them in non‐degraded, moderately and severely degraded grasslands. Results Cattle exhibited broader diet than sheep, and diet overlap between species was lower in non‐degraded grasslands. As grassland degradation increased the availability of annual plants, interspecific niche overlap between cattle and sheep gradually increased, and cattle suffered a resulting dietary niche compression. Sheep maintained a relatively narrow and constant dietary breadth. Conclusion The increasing dietary niche overlap between livestock species with increasing extent of grassland degradation indicated increased additive effects of cattle and sheep co‐grazing on plant community, and thus stronger effects on plant community composition and diversity.