This suggests that land managers should pay particular attention to the litter balance on sagebrush steppe rangelands. Steep headwater basins in the sagebrush steppe are often close to a threshold of geomorphic instability. The presence of gullies in these basins is an indication that the threshold was crossed. Valley profile for North Draw, North Fork of Savery Creek, southcentral Wyoming My observations of headwater areas in sagebrush steppe suggest there are two principal valley-floor types that illustrate the importance of valley width to geomorphic instability. Type I valleys are V-shaped, as shown in Figure 1 for a headwater basin in southcentral Wyoming.
Valley floors are very narrow and hydrologically connected to the adjacent hillslopes.
Because of the slope breaks, the valley floors are hydrologically disconnected from the hillslopes. Type I valleys tend to be more unstable than Type II valleys. It may be possible, within a landscape classification system, to identify landform units that are susceptible to ecological change, or close to a threshold of change, and to combine this information with indicators of ecological condition. Literature Cited Bailey, Robert G. 1995. Description of the ecoregions of the United States.