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,~ METHODS In eazly June 1998, four reference sites were established within reclaimed areas at Coal Basin Mine that had become infested with noxious weeds. The reference sites were located within larger infested areas that would be subject to weed control efforts over a several year period. Size of the reference sites varied, but each was rectangular in shape, and marked in the field by wooden or steel stakes at each corner. A systematic sampling design was employed for data collection within each reference area. Repeated sampling of the same areas over the course of the control project was intended to provide an objective basis for evaluating treatment success; recognizing that, because multiple replications of treatments and controls were not employed, population trends could not be definitively linked to specific management variables. Reference site locations, slope and aspect, and initial infestation severity, were chosen to be generally representative of the lazger treatment areas within which the reference areas were located. Statistical inference based on data from individual reference areas cannot be extended to the lazger treatment areas. However, the reference azea data can be combined with visual evaluation of reference and larger treatment areas to ensure a more objective assessment of treatment impacts, and to provide a sound basis for professional judgement and management decisions. Sampling was conducted the 3" or 4'" week of June each yeaz. Reference Area #1 ("Sutey Pile Flat") is a SOm x 35m area on relatively flat topography located immediately to the west of the Sutey Refuse Pile, within the "V" formed by a ranch road and a refuse pile access road that diverge at that location. Each yeaz of the study, ten, 35m cover transects were run, with Sm spacing between transects. Two cover readings were made at 1.5 intervals along each transect, using a tripod mounted oculaz point baz, giving a total of 46 cover points pet transect. Live vegetation (current year's growth for herbaceous vegetation) was recorded by species, along with litter, rock, and bare ground. in 1998, density of combined thistle species was estimated by counting live thistle plants within a Im by 35m quadrat along one side of each transect. in subsequent years, houndstongue density was also estimated. Reference Area #2 ("West Slope Sutey") is a SOm x 25m azea on the steep west facing slope of the Sutey Pile, near the southwest corner of the pile. Ten, 25m cover transects were run each yeaz, with Sm spacing between transects. Two cover readings were made at lm intervals alongthe transect, for a total of 50 cover points per transect. Each yeaz, density of combined thistle species andhoundstongue was estimated for the south half of the reference area, by counting individual plants within 1x25mquadrats along one side of each of the five transects within the south half of the reference area. Reference Area #3 ("Belt-line Flat") is located along the relatively flat surface of a segment ofbeltline corridor, which was reseeded in the fall of 1997. The reference area is SOm x l Om, with ten, l Om transects spaced at Sm intervals. Two cover readings were made at O.Sm intervals, for a total of 40 cover readings per transect. Thistle density was estimated by counting thistle plants within 1x10mquadrats along one side of each transect. Reference Area #4 ("Belt-line Outslope") is not actually a reference area, but rather two pazallel SOm transects along the weed infested outslope of the beltline corridor, adjacent to Reference Area #3. One cover reading per one meter interval was recorded, for a total of 50 points per transect. Cover readings for each transect were made on the uphill side ofthe transect. Due to very high initial density of noxious weeds, density counts were not attempted. Transects were staked at each end to ensure that the same transect locations were read each yeaz.