While Yellowstone's celebrated bison may be among the most popular tourist attractions in the park, their grazing habits and increasing numbers have raised questions about the long-term stability of the park's grasslands. To find answers, the National Park Service has partnered with Syracuse University biologist Douglas Frank, who has studied the effects of climate change and herbivores on the park's grasslands over the past 20 years.
"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, a professor in SU's College of Arts and Sciences. "Rather than having a negative impact on the grasslands, we found that increases in elk grazing actually stimulated plant growth."
The new study, which will take about three years to complete, will focus on grazing areas most frequented by bison and will incorporate ecological research techniques that were pioneered at SU. Frank will also work with National Park Service staff to develop a long-term grasslands monitoring system using these same research methods.
"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."
Past studies have found that intensive grazing triggers several mechanisms that actually increase plant growth. For example, increases in the amount of elk feces and urine on heavily grazed areas provide an easily available source of nutrients for plants, as compared to ungrazed areas. In addition, grazing spurs plants to produce new shoots and grow new leaves. Younger, more numerous leaves and shoots are more photosynthetically active than older leaves on un-grazed areas. Consequently, grazing stimulates both shoot and root growth and incre
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