Above-ground vs. below-ground interactive effects of mammalian herbivory on tallgrass prairie plant and soil characteristics

Abstract

To better understand how mammalian herbivory affects tallgrass prairie, I set up field exclosures to test effects of above-ground herbivory (AGH) (Bison bison L. is a potential above-ground herbivore), below-ground herbivory (BGH) (Geomys bursarius and Spermophilus tridecemlineatus are potential below-ground herbivores), and the interaction of the exclusion of both, on tallgrass prairie plant species, plant community parameters, and soil parameters in the Flint Hills of Northeastern Kansas. I found that (1) AGH reduced the cover of some forbs but increased the cover of others while both AGH and BGH decreased the cover of dominant C4 grasses, (2) no treatments significantly affected species richness but ABH reduced total cover and maximum height of the vegetation while BGH reduced species evenness and maximum height, and (3) no treatments affected soil pH or soil nitrogen but BGH reduced soil organic matter, soil phosphorus, and soil potassium. Whereas above-ground mammalian herbivory has significant effects on individual plant populations and plant community structure, it is BGH that mainly affects soil parameters. Results suggest that for prairie patches where both kinds of herbivory are present, these effects may be additive leading to cumulative effects on tallgrass prairie plants both directly, through herbivory, and indirectly, through soil changes.