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Russian thistle (Salsola tragus L.) invaded areas of native montane grassland important to winter survival of bighorn sheep (Ovis canadensis Shaw) were studied in Jasper National Park, Alberta, Canada. The biology of Russian thistle and its control in the Park were studied in the field and greenhouse. Russian thistle in grasslands were 9.1 cm tall with 37.5 seeds per plant, whereas larger plants in naturally disturbed habitats were 29.8 cm tall with 1562.4 seeds per plant. Plants travelled up to 4,180 m during dispersal. With soil seed contact, litter depth did not inhibit performance or survivability; without soil contact, thick litter reduced germination and plant performance. Russian thistle responded positively to increased greenhouse temperature and drier conditions. Seven control treatments involving herbicide, seeding mixes, hand pulling, and grazing exclusion were assessed. Grazing exclusion was the best field management option, increasing litter and biomass, while reducing Russian thistle density and biomass. / Land Reclamation and Remediation

This study examined the feeding responses of mule deer to a system of spring livestock grazing. The specific purposes were 1) to determine botanical composition of diets selected by mule deer on a winter range subjected to previous spring grazing by sheep compared to one with no sheep grazing and 2) to develop a basis for predicting selection of individual plants by deer, based on physical characteristics of the plants and the species and physical proximity of associated plants. The study was conducted within the framework of a completely randomized experimental design with two treatments. Variables controlled for each unit of observation were grazing treatment (prior sheep grazing and no sheep grazing), sampling periods within the winter (early winter and late winter), weeks (four within each period), days (four within each week), sampling times (four each day), age of animal (fawns and adults) and identity of observer. Two adjacent 2.4 ha pastures were fenced. A sheep grazing treatment of 150 sheep days per ha was applied in late May, 1974, to one pasture. Five hand-reared mule deer were placed in each pasture for two six-week periods, one in early winter and the other in late winter. Diets were quantified by a mouthful count technique and hand plucking representative mouthfuls of each species consumed. Plant physical characteristics were measured while following grazing deer. For each plant encountered by the deer, the following variables were measured: species name, distance from the deer, height and width, degree of prior utilization, proportion of current live plant material present, species of and distance to nearest neighboring plant, and consumption or non-consumption of the plant by the deer. Differences were found between treatments in forage availability and abundance, and in botanical composition of diets selected by mule deer. The dietary differences were attributed to a greater proportion of current year's bitterbrush forage being available in the sheep grazed treatment and to reduced interference there from standing dead grass in selection of preferred green grasses and forbs. Deer diets in the sheep grazed pasture were higher in herbaceous plant material than in the deer pasture. Seasonal dietary changes were due to reduced plant availability by deer grazing, snow cover, and plant phenology. Major changes were an increase in shrub consumption through the early winter and well into the late winter periods, and a simultaneous decline in herbaceous species consumption. Snow melt and spring green-up permitted a sudden shift to forbs and grasses near the end of the late winter period. Plant attributes capable of predicting consumption of individual plants included 1) degree of prior utilization, 2) amount of current live plant material present, 3) distance of plant from grazing animal, 3) species of nearest plant, and 4) plant height. These characteristics probably exerted their influence indirectly through olfactory and tactile stimuli to the deer. The use of these attributes to place plants in consumed and not-consumed groups indicated that grazing deer probably cue on fairly specific plant characters in selecting plants for consumption.