The study, which should take three years, will set to determine the specific effects of bison grazing on Yellowstone grasslands.
“During the late 1980s, similar concerns were raised about the size of the park’s elk herd and whether the herd was negatively impacting grasslands,” says Frank in in a release. “Rather than having a negative impact on the grasslands, we found that increases in elk grazing actually stimulated plant growth.”
The study will monitor growth in grasslands from year to year, as well as track grazing on them. Frank’s theory — which has been proven in other areas — is that heavy grazing on grasslands is actually beneficial: urine and feces from bison can serve to stimulate plant growth, with new hardiest plants replacing older, slow-growth plants. By constantly churning the soil, grazing bison actually increase plant vitality.
That’s the theory, anyway, though many living in the Greater Yellowstone Ecosystem — especially those living around bison — would certainly accept the theory as being reality.
“Fossil records indicate that prior to the industrial revolution, the Earth’s grasslands and large herds of migratory herbivores coexisted for millennia,” Frank says. “These systems were stable, despite having sustained very intense levels of grazing. My work in Yellowstone explores why and how this happens.”
Next spring, Frank will travel to Yellowstone to fence areas of grassland that will become test plots for the study. Each fenced-in area will be about a 15-yard square and will be left untouched for a year. Over the following two years, some areas will be clipped at various intensities to mimic natural grazing. Plant data obtained from the fenced areas will be compared with adjacent areas as well as with areas of the park where natural grazing varies in intensity depending on the time of the year.
“The study will be very similar to the one we did 20 years ago on elk grazing,” Frank says. “It will be interesting to see if we reconfirm our original findings or whether we find something new. We also intend to use this opportunity to better understand the complex and fascinating ways in which the interactions among plants, herbivores and soil organisms foster the stability of grassland systems.”