In 1958, 13 belt transects were established within the ungulate winter range in the northern portion of Yellowstone National Park to study how shrub communities were affected by grazing from ungulate populations. Between 1958 and 2008, the belts have been measured and photographed by different researchers at least once per decade, which has resulted in a comprehensive 50 year time series of how these communities have responded to climatic change, herbivory, and natural disturbance. In this study, we compare the percent cover, seedling establishment, and plant survival in these communities at two points in time (1958 and 2008); and explore which factors – climatic, herbivory, or disturbance – were most influential to changes in canopy cover and number of seedlings after 50 years. The recovery of the big sagebrush community after the North Fork fire is also discussed. Herbivory has controlled tree growth on the shrub belts. Climate and lack of disturbance have resulted in an increase in big sagebrush (Artemisia tridentata) cover on many shrub belts inside and outside of exclosures. Invasive annual species have become important drivers of vegetation change at the lowest elevation site.
Sikkink, Pamela G.
"Yellowstone Sage Belts 1958 to 2008: 50 Years of Change in the Big Sagebrush (Artemisia tridentata) Communities of Yellowstone National Park,"
Natural Resources and Environmental Issues:
Vol. 17, Article 19.
Available at: http://digitalcommons.usu.edu/nrei/vol17/iss1/19