The effects of late spring defoliation on the winter forage quality of bluebunch wheatgrass (Agropyron spicatum [Pursh] Scribn. & Smith), Idaho fescue (Festuca idahoensis Elmer) and elk sedge (Carex geyeri Boott) and the response of wintering Rocky Mountain elk (Cervus elaphus nelsoni Bailey) to changes in winter range forage quality were examined. The study included two experiments; a hand clipping experiment conducted on bluebunch wheatgrass and a sheep grazing experiment conducted on bluebunch wheatgrass, Idaho fescue, and elk sedge. Four treatments were applied to bluebunch wheatgrass in the clipping experiment: 1) the entire basal area of individual plants was clipped to a 7.6 cm stubble height during the mid boot phenological stage, 2) one-half the basal area of individual plants was clipped to a 7.6 cm stubble height during the mid boot stage, 3) the entire basal area of individual plants was clipped to a 7.6 cm stubble height during the inflorescence emergence stage, and 4) plants were left unclipped as a control. In early November, forage samples from each of the three clipping treatments exhibited increases in percent crude protein and percent in vitro dry matter digestibility compared to the unclipped control treatment. Clipping the entire basal area of bluebunch wheatgrass plants to a 7.6 cm stubble height during the mid boot or inflorescence emergence stage was more detrimental to plant vigor than clipping one-half the plant basal area during the mid boot stage or leaving the plants unclipped. There was some evidence that clipping one-half the plant basal area during the mid boot stage may improve plant vigor compared to no clipping. Differences in crude protein, in vitro dry matter digestibility, and dry matter yield from winter forage samples of bluebunch wheatgrass, Idaho fescue and elk sedge were detected between plots grazed by domestic sheep during the boot stage of bluebunch wheatgrass and plots where sheep grazing was excluded. No differences in winter elk utilization of bluebunch wheatgrass, Idaho fescue, or elk sedge were detected between the late spring sheep grazing treatment and sheep exclusion treatment. Plot occupancy by wintering elk was similar between plots grazed by sheep and plots where sheep grazing was excluded. Although, wintering elk did not appear to respond to the livestock grazing treatment, results from this study suggest small improvements in the winter forage quality of perennial grasses such as bluebunch wheatgrass can result following late spring defoliation. Forage conditioning treatments which produce even small improvements in forage quality may be important to the nutritional status of wintering elk. / Graduation date: 1997

This research was conducted on three study areas on elk winter ranges in Northeast Oregon. One was on the Starkey Experimental Forest and Range and the others were in the same vicinity. Plant appendages, spring and fall defoliation and fall growth of bluebunch wheatgrass were evaluated in terms of quality of nutrient content during September through April of 1986-87 and 1987-88. Four treatments were applied. Plants were clipped to a 2.5 cm and 7.6 cm stubble height in the spring before the boot stage of phenological development; plants were clipped to a 7.6 cm stubble height in the fall after plant maturity in September; plants were not clipped during the year. Percent crude protein, dry matter digestibility (DMD), acid detergent fiber (ADF), and lignin were evaluated monthly. Samples from the four treatments were also analyzed from October to April to determine monthly changes in nutrient contents. Production of growth from all treatments was measured in October and March each year. Leaf material had higher percent crude protein and DMD, with lower percent ADF and lignin than the inflorescence and culm. The third leaf (the youngest plant material) had the highest nutrient value of all appendages. The culm and inflorescence values were not statistically different. Growth following spring defoliation treatments produced higher percent crude protein and DMD (P<.05), with a lower percent ADF and lignin than non-treated plants in both years. This was particularly pronounced during 1986 when precipitation in late summer initiated fall growth. Growth following spring defoliation and bluebunch wheatgrass not defoliated did not produce crude protein or DMD values sufficient to meet minimum dietary maintenance requirements for elk. Fall precipitation adequate to promote fall growth occurred only in 1986. Growth after fall defoliation had the highest percent crude protein and DMD with the lowest ADF and lignin values of all vegetation sampled. However, without 3-5 cm of late summer/early fall rains, fall growth does not occur. This happened in 1987. When growth does occur in fall the quality of the growth exceeds the minimum dietary maintenance requirements for elk. Freezing and thawing of fall growth plant material had minimal effect on forage quality. There were differences (P<.05) between the monthly values for percent crude protein and ADF starting in October and ending in April. However, the percent DMD and lignin from October to April were not different (P<.05). / Graduation date: 1993

A study investigating the effect of sheep stocking density and grazing duration on forage intake, grazing efficiency, dietary selectivity and subsequent forage accumulation in tall fescue(Festuca arundinacea)- subclover(Trifolium subtaranium) pastures was conducted near Corvallis, Oregon during early and late spring in 1988 and 1989. Grazing treatments were 2, 6, and 10-day duration and corresponding stocking densities 380, 130, 78 and 1390, 460 and 280 ewes/ha during early and late trials each year, respectively. Average daily intake and grazing efficiency were highest (P< 0.05) in the 10-day duration and lowest in the 2-day duration. During the first 2 days of all duration treatments, average daily intake decreased as stocking density increased (P< 0.05). Manure cover and crowding stress may explain lower average daily intake under the shorter duration/high density treatments. However, stocking density had little effect on grazing efficiency. This was largely due to the high amount of forage destroyed under the low density treatments which offset the effect of higher forage intake of that treatment. Within the 10-day duration treatment, average daily intake was the same over time (P> 0.05), while grazing efficiency decreased as grazing progressed (P< 0.05). The low grazing efficiency during the early stages of grazing reflected high initial forage destruction probably caused by the movement of animals at the start of grazing to establish bedding and habitual use areas. Growth rate of forage after grazing was highest in the longer duration paddocks and lowest in the shorter duration paddocks (P< 0.05), but the yield was similar under all treatments (P> 0.05). Although short duration/high density grazing is considered to be non-selective, sheep were equally or more selective under very short duration/very high density compared to longer duration/lower density treatments in this study. The 2 days duration was not an attractive management option since the intake and grazing efficiency were low, and the animals were selective. / Graduation date: 1993

Graduation date: 1989

Graduation date: 1993