Biological invasions and changing herbivore communities can jointly reshape grassland ecosystems by altering vegetation structure, microclimate, microbial communities, and trophic interactions. We examined these effects in temperate Australian grassy woodlands dominated by kangaroo grass (Themeda triandra) and invaded by African lovegrass (Eragrostis curvula). Across six livestock-grazed farms, we established nested herbivore-exclusion treatments (open, livestock excluded, and all mammals excluded) in paired subsites dominated by kangaroo grass or co-dominated by African lovegrass. We measured microclimate, biomass, foliar damage, and characterized microbial phyllosphere and arthropod communities. The results revealed that African lovegrass invasion and herbivore exclusion independently and interactively reduced phyllosphere diversity, while concurrently increasing litter and lowering surface temperatures. Herbivore exclusion reorganized vegetation structure and invertebrate community composition, while shifting fungal infection profiles in ways that disproportionately affected the native grass. These results suggest that native mammals and livestock can partially buffer invasion-associated changes in ecosystem structure and biotic interactions.