Investigating Successional Vegetation Changes and their Relation to Sensitive Small Mammal Habitats in a Primitive Montane Riparian Environment

Latitudinal and longitudinal changes in the vegetation of the riparian area of Oliver Creek in the Cloud Peak Wilderness Area of the Bighorn Mountain were studied by an international team of U.S. and Scottish high school students in the summer of 2000. Effects of aspect and elevation and the influence of substrate and climatic patterns on vegetation surrounding Oliver Creek were examined, and the presence of sensitive small mammals and amphibians and reptiles were noted during a three-week period in late June and early July.

Riparian vegetation plays a key role in the proper functioning of an ecosystem and the maintenance of the water quality of a stream. Not only does this vegetation provide habitat and forage for animals, but it also stabilizes the stream bank, filters out sediments and chemicals, slows the flow of runoff, and provides shading and allochthonous matter for the stream. The types of vegetation present along a stream bank are affected by the composition of the underlying rock and soil, the climate, and the topography of the region. Traditionally, riparian areas have been an underrepresented study area.

The study was conducted along two intersecting transects in the Oliver Creek catchment area. Sampling of graminoids, forbs, and dwarf shrubs were performed along transects at uniformly spaced quadrats. Sampling of forest and large shrub community types were completed using 500 square meter circular plots in which all trees over 10 cm dbh are measured and identified. The underlying substrate was examined to determine the depth of the soil's A and B horizons, and measurements made of the soil's pH and moisture content. The amount of daily exposure to direct sunlight of the sampling sites, amount of precipitation, and current atmospheric conditions such as air temperature and relative humidity were recorded. The presence and numbers of any small mammals and amphibians and reptiles during the course of the vegetation studies were noted.

Vegetation patterns and successional relationships were analyzed and graphically displayed. Significant data was obtained to prepare a GIS model of the study site. Efforts were made to identify over 1000 data points on GPS instruments. Each of the plant sampling sites, soil pits, and animal observations were mapped several times to provide reliable data for the team to develop the GIS model. The Environmental Institute provided support for model development at Penn State University.