1. Simultaneous reductions in herbivore abundance and increases in nitrogen deposition have led to radical shifts in plant communities worldwide. While the individual impacts of these human-caused disturbances are apparent, few studies manipulate both herbivory and N, nor differentiate among herbivore guilds, to understand contingencies in the ability of these drivers to affect producer diversity and productivity. As such, understanding how the main and combined effects of increasing soil N with declining herbivores may influence plant community structure and function is critical to better understand the future of grassland ecosystems under multiple global change drivers. 2. In this study, we asked: (1) What are the main effects of small mammal herbivores, invertebrate herbivores, and soil N on plant community structure and function? and (2) Are the effects of invertebrate herbivores and soil N on plant community structure and function contingent on small mammal herbivory? We used a design, with invertebrate and soil N treatments nested within small mammal manipulations in an existing tall grass prairie. We quantified plant community structure ( plant richness, evenness, diversity, and composition). We also recorded total aboveground biomass to quantify grassland productivity. 3. We found that small mammal herbivores strongly shaped plant diversity, species composition, and productivity. Small mammal herbivores also mediated the effects of soil N and invertebrate herbivores on grassland community structure, but not composition or productivity. Small mammal reduction lowered plant species richness while increasing above ground biomass and altering compositional similarity. Invertebrate herbivores, in the presence of small mammals, promoted plant dominance by reducing evenness without altering compositional similarity. Additionally, soil nitrogen addition reduced plant richness, but only when small mammals were reduced, and no effects on compositional similarity or productivity. 4. Our findings provide further evidence that temperate grasslands productivity and diversity are driven by top and bottom up factors.