Heavy grazing significantly reduces Stipa grandis growth. To enhance our understanding of plant responses to heavy grazing, we conducted transcriptomic, proteomic, and metabolic analyses of the leaves of non-grazed plants (NG) and heavy-grazing-induced dwarf plants (HG) of S. grandis. A total of 101 metabolites, 167
proteins, and 1,268 genes differed in abundance between the HG and NG groups. Analysis of Kyoto Encyclopedia of Genes and Genomes pathways among differentially accumulated metabolites (DAMs) revealed that the most enriched pathways were
flavone and
flavonol biosynthesis,
tryptophan metabolism, and phenylpropanoid biosynthesis. An integrative analysis of differentially expressed genes (DEGs) and
proteins, and DAMs in these three pathways was performed. Heavy-grazing-induced
dwarfism decreased the accumulation of DAMs enriched in phenylpropanoid biosynthesis, among which four DAMs were associated with
lignin biosynthesis. In contrast, all DAMs enriched in
flavone and
flavonol biosynthesis and
tryptophan metabolism showed increased accumulation in HG compared with NG plants. Among the DAMs enriched in
tryptophan metabolism, three were involved in
tryptophan-dependent IAA biosynthesis. Some of the DEGs and
proteins enriched in these pathways showed different expression trends. The results indicated that these pathways play important roles in the regulation of growth and grazing-associated stress adaptions of S. grandis. This study enriches the knowledge of the mechanism of heavy-grazing-induced growth inhibition of S. grandis and provides valuable information for restoration of the productivity in degraded grassland.