MATERIALS AND METHODS 



Data Collection 



Field sampling took place in the summers of 1991 and 1992 on 

 BLM lands in Carbon County, Montana, south and southeast of the 

 town of Bridger and east of the Clarks Fork of the Yellowstone 

 River. The 1991 work v/as done as an adjunct to the study by 

 Lesica and Achuff (1992) that focused on describing the 

 distribution of vascular plant species of special concern and 

 limited distribution. The 1992 sampling focused on filling in 

 remaining gaps in the characterization of vegetation types. 



Sampling focused on rare or previously undescribed 

 communities and on common communities in particularly good 

 condition. To minimize the confounding nature of heavy 

 disturbance on vegetation occurrence, areas severely over-grazed, 

 herbicide treated, mechanically disturbed, artificially seeded, 

 or irrigated were not sampled. Plots v/ere established within 

 "portions of stands that appeared to be relatively uniform in 

 topography and vegetation structure. Within an area, one to five 

 plots v/ere chosen to represent the contrasting vegetation 

 composition on differing geomorphic facets. 



Plot selection focused on contemporary stands of vegetation 

 without reference to successional relationships among stands. We 

 did not attempt to confine our sampling to remnants of 

 presettlement vegetation. 



All data were recorded on Montana Natural Heritage Program 

 (MTNHP) Community Survey Forms (DeVelice 1991) . Additionally, 

 MTNHP Reconnaissance Soil Characterization Forms were completed 

 during the 1992 sampling. The Community Survey Forms are similar 

 to the general plot data and ocular plant species data forms used 

 by the USDA Forest Service (USDA 1987) . Complete lists and 

 canopy cover estimates of vascular plant species were recorded 

 within each 375 m- circular study plot. Site information such as 

 altitude, slope, aspect, parent material, landform, and erosion 

 characteristics were also recorded for each plot. 



A 20 inch deep reconnaissance soil pit was excavated at the 

 1992 sample sites and information was collected to determine soil 

 subgroup and general physical properties (e.g., texture; coarse 

 fragment content) . Additionally, surf icial (top 2 to 6 inches) 

 soil samples were collected in 1992 for pH and electrical 

 conductivity (a measure of free salts) determinations. pH and 

 electrical conductivity measurements were made using 2:1 aqueous 

 suspensions of the soil samples collected in 1992. These 

 suspensions were equilibrated for at least 15 minutes before 

 measurements were taken with a temperature-compensated digital 

 Myron L DCH4 meter. 



