Dynamics of the Shrub Continuum Along the Gallatin River in Yellowstone National Park

Willows dominate the shrub vegetation along the Gallatin River and with the other shrubs allow different growth and mortality responses relative to their position from the river and other environmental factors. The shrub species from a continuum from the river to the dry grassland depending upon the varying moisture regime. The sequence of shrub species from wet to dry appears to be Salix farrae, S. lutea, S. drummondiana, S. exiqua, Artemisia cana, and A. tridentata. Individual species also vary in their ability to survive present environmental pressures, including periodic heavy browsing.