Data and R Markdown files for "Insect herbivores increase plant species richness in a long-term grassland experiment."

Although effects of large-bodied mammals, such as cattle or bison, on plant diversity in grasslands have received considerable attention, long-term impacts of small herbivores, such as insects and small mammals, rarely have been examined. We manipulated densities of individual herbivore groups (insects, small mammals, and larger mammals (i.e. rabbits and deer)) using insecticide and fencing in a Kansas USA tallgrass prairie restoration in a 12-year experiment. We applied herbivore reduction treatments in combination with fertilizer addition to test interaction effects between herbivory and soil nutrient availability. We quantified effects of each herbivore group and their interactions with soil fertilization on plant species richness. Reducing insect densities resulted in lasting decreases in total plant species richness beginning in the fifth year of the experiment. Small mammal reduction temporarily lowered species richness of annual plants for three years in the middle of the experiment, but otherwise small mammal and larger mammal reductions had little effect on richness. We found little evidence for interaction effects between herbivore density reduction and soil fertilization upon plant species richness. In grasslands without large grazers, chronic insect herbivory can promote plant species richness. Herbivores’ effects largely were consistent across different soil nutrient levels.