Quantitative effects of temperature on germination were determined for 17 cool-season grasses, 19 warm-season grasses, and 18 miscellaneous forbs and shrubs associated with semiarid rangelands. These effects, expressed as the reciprocal of days to 50% germination, were used in linear regression analyses to predict the temperature at which the germination rate approaches zero from which heat units to 50% germination and germination indexes were derived. The regression relationships appeared to be linear if data were restricted to the lower range of germination temperatures. The germination rate approached zero at temperatures ranging from 3.7 to 6.3 degrees C for cool-season and from 7.8 to 13.7 degrees C for warm-season grasses. No particular trend was evident among the forbs and shrubs. The reciprocal of the slope of the regression equation was a constant expressing heat units to 50% germination. It was characteristic of each accession. The product of heat units and the zero rate temperature was used to calculate a germination index. This index compared well with selected germination responses observed in the field.

The possibility of using livestock as a biological agent to control unwanted ground vegetation in Pacific Northwest coniferous forests has been discussed for over 50 years. However, little quantitative information has yet been published documenting the efficacy of livestock in suppressing brush and other ground vegetation in commercial Douglas-fir (Pseudotsuga menziesii) plantations. Therefore, a study was conducted in 1981 and 1982 to evaluate the potential for using herded sheep to control competing vegetation in Douglas-fir plantations in Pacific Northwest coniferous forests. Three 4- to 6-year-old plantations were grazed once each year during the May to September grazing season. Estimates of current year's growth present in October, both inside and outside a livestock exclosure on each study plantation, were used to evaluate the effects of grazing. In general, utilization of brush by sheep was moderate to heavy, except in the spring of 1982, when brush was lightly utilized. Sheep grazing effectively reduced (p<0.01) both total understory plant growth and brush net current year's growth on all plantations. Reduced brush biomass on grazed areas was associated with greater Douglas-fir diameter growth in 1981-82 and 1982-83. By 1985, trees in grazed areas were 5% taller (p<0.05) and 7% greater in diameter (p<0.01) compared to ungrazed controls. Our data and observations suggest that sheep may be effectively used as a biological control agent for brush control in coastal Douglas-fir forests.

A salt water blowout at an oil drilling site in 1982 in a badlands area of western North Dakota caused severe damage to the native vegetation. A study was initiated to measure the effect of reclamation on soils and revegetation of the affected area. Basal cover and plant density were measured on a portion of the contaminated area following the blowout and in 1984 following reclamation of the site. The contaminated soil was reclaimed by adding CaCl2 to irrigation water which was used to leach the upper 15 cm of the soil profile. In July 1982, after the blowout, Distichlis stricta was essentially the only species growing at the site. In July 1984, following reclamation, species with the highest percent basal cover on the reclaimed half were Agropyron smithii (Rydb.), Bouteloua gracilis (H.E.K. Lag.), and Distichlis stricta (Torr.) Rydb. On the unreclaimed half Agropyron smithii, Distichlis stricta, Lepidium denisflorum Schrad., and Opuntia polycantha Haw. had the highest percent basal cover. In 1984, basal cover of the grasses on the reclaimed site was two-thirds of that on a site with no visible damage from the salt water. The percent bare ground was still 25% on the reclaimed half of the contaminated site in 1984, but had increased on the unreclaimed half to 43% leaving the surface open to potentially serious erosion. Soil data indicated that reclamation had successfully reduced sodium adsorption ratio (SAR) values in the surface 15 cm to more acceptable levels for vegetation recovery.

Two digestibility and nitrogen balance studies were conducted to evaluate nutrient utilization of 3 commonly browsed range plants by the desert sheep in Northern Saudi Arabia. In experiment 1, 15 Najdi wether lambs (40 kg) divided in 3 lots of 5 were randomly allotted to 3 diets of 200 g ground barley (Hordeum vulgare L.) grain and 800 g either alfalfa hay (Medicago sativa L.), dried Acacia cynophylla Lind., or Haloxylon persicum Bge. clippings. In experiment 2, 8 Najdi wethers were randomly alloted to treatments of 2 kg green alfalfa or 2 kg green Atriplex halimus L. clippings per day. Salt content of the soil and salt bush, Atriplex sp., were also determined. The organic matter (OM), crude protein (CP), and crude fiber (CF) on dry matter basis (DMB) were, respectively, 90, 15, 31% for alfalfa; 90, 13, 30% for acacia forage; and 87, 10, 37% for haloxylon shrub. In experiment 1, the OM digestibility was 66, 56, 53%; CP digestibility was 73, 68, and 55%; and CF digestibility was 44, 33, and 16%, respectively, for alfalfa, haloxylon, and acacia diets. The daily nitrogen balance was +4 g for both alfalfa and acacia groups. The haloxylon group had a negative nitrogen balance (-1.9%), showing no apparent retention of absorbed nitrogen. In experiment 2, the atriplex clippings contained 73% OM, 18% CP, and 24% CF on DMB, the respective digestibility values being 61, 79, and 39%. Even though the digestibility of as well as percent retention of absorbed nitrogen in atriplex group were markedly higher than those in alfalfa group, the digestibility of CF was lower (P<.01) in the former (39%) as compared to that in latter group (54%). The sodium, potassium, and chloride concentration of soils of high and low salinity had no influence on their contents in atriplex forage, with average values being 10, 2.5, and 16.5% respectively.

If crested wheatgrass [Agropyron desertorum (Fisch.) Schult.] could be maintained in an immature growth stage, it would improve forage quality and thus extend the grazing season. In 1981 and 1982, plant growth regulators were applied to crested wheatgrass 0, 2, 4, and 6 weeks after first floral primordium initiation to determine which compound, date, and rate of application would maximize forage quality yet minimize reduction of forage yield when harvested at seed ripe stage. Mefluidide [N-(2,4-dimethyl-5-{[(trifluoromethyl)-sulfonyl]amino}phenyl)acetamide] at 4 rates [0.0, 0.28, 0.56, and 0.84 kg/ha active ingredient (a.i.)], maleic hydrazide (MH) (1,2-dihydro-3,6-pyridazinedione) at 4.5 kg/ha a.i., and MH (3.36kg/ha a.i.) plus chlorflurenol (methyl-2-chloro-9-hydroxyfluorene-9-carboxylate) at 1.12 kg/ha a.i. were applied to crested wheatgrass growing on a Shambo loam (Typic Haploborolls) in northeast Montana. Application of MH or MH plus chlorflurenol generally gave a similar response in heading, forage yield, CP, and in vitro organic matter digestibility on a dry matter basis (IVDOMD) as did melfluidide at 0.56 kg/ha. Mefluidide (0.56 kg/ha) applied 2 weeks after first floral primordium initiation decreased heading 80 and 95%, decreased forage yield 20 and 30%, increased CP 1.7 and 2.3 percentage units, and increased IVDOMD 1.8 to 4.2 percentage units compared to untreated, depending upon year.

Jojoba (Simmondsia chinensis) is a major evergreen browse species for livestock and wildlife throughout its range from central Arizona to northwest Mexico and Baja California. Current guidelines for grazing management are based on utilization levels as estimated from determining the percentage of twigs grazed. Utilization can be estimated more accurately from twig diameter measurements. On 3 sites in southern Arizona, leaf weight, stem weight and total weight were correlated with the square of twig internode diameter, having average r2 values of 0.81, 0.73, and 0.83, respectively, for small diameter twigs (less than or equal to 3mm) most frequently browsed. Estimates of twig weight from regression equations for the 3 sites varied less than 0.3 g and low standard errors of estimate (less than or equal to 0.33) indicate twig diameter measurements can give precise estimates of twig weight. Percent utilization of current year's growth can be calculated from estimates of twig weight remaining and twig weight removed by grazing from diameter measurements at initiation of current year's growth and at the point of grazing, respectively. On 2 sites, mean grazed twigs and mean weight utilization were similar for shrubs moderately grazed by cattle. However, regressions of weight utilization on percent twigs grazed indicated that percent twigs grazed could overestimate weight utilization of total twigs and underestimate weight utilization of current year's twigs, especially when utilization is high. An alternative to basing management of jojoba on time-consuming utilization measurements and arbitrary utilization limits is to monitor size of marked shrubs and manage for stable or gradually increasing shrub size.

Dyers woad (Isatis tinctoria L.) is an introduced cruciferous forb that is rapidly expanding on intermountain rangelands and is apparently reducing production and regeneration of more desirable forage plants. Mechanical and chemical controls are expensive as well as having deleterious effects on nontarget species. Limitations to controlling this noxious weed by early spring grazing were investigated with clipping experiments at 1 site in the Wasatch foothills of northern Utah. These results were compared with actual utilization of woad by sheep at a poor condition example of that site. Significant mortality and reduction in reproductive performance occurred when at least 60% of the aboveground phytomass had been removed on or after 23 May. Clipping twice, to remove as much as 90% of aboveground tissue before 23 May, did not significantly affect woad mortality, percent flowering, or fruit production. Sheep did not graze this weed heavily enough at late enough dates to significantly affect mortality or seed production. Even on a poor condition range, these animals switched to other forages after about 15 May. Stocking rates required to restrict dyers woad at our clipping site would likely result in further range deterioration. More host-specific biological control agents should be examined.

Although soil texture is important to plant growth, cultivation, hydraulic conductivity, and soil strength, laboratory procedures for determining particle size distribution can be confusing. A number of settling times have been proposed for the hydrometer method used to analyze the fine earth fraction of soils. To separate sand and silt, hydrometer readings at 30 and 60 seconds, 35 seconds, or at 40 seconds have been recommended. To distinguish between silt and clay, recommendations have been made for readings at 6-8 hours and 12-15 hours, 1.5 and 24 hours, 2 and 24 hours or at 8 hours. In this study, no significant differences in estimates of sand content were found between readings made at 30 and 60 seconds and at 40 seconds. However, estimates from readings on both sides of the silt-clay separation (at 6 hours and 12 hours) showed a significant variation of clay content within the sample probably due to an inadequate method of splitting the soil samples into subsamples. Clay estimates from 2-hours readings differed significantly from the average estimate of the split sample 6/12-hours readings. Numerical differences were seen among particle size estimates from various methods; if the soil texture is near a division between 2 classes, these differences may result in different textures being assigned.

Forty-six clonal lines of a hybrid cross between Pseudoroegneria spicata [Pursh.] Scribn. and Smith × Elytrigia repens [L.] Beauv. were used to evaluate the influence of various chemical and morphological characteristics on cattle preference. Variables examined included total carbohydrates as well as several individual sugars, silica, nitrogen, moisture, leaf and growth form, phenology and plant height. In 3 of 4 trials, over 60% of the variation in preference as measured by bite counts was accounted for in the analyses. However, dominant factors controlling preference varied from trial to trial. Predictive equations developed for each trial (N=46) produced R2 values which ranged from 0.53 to 0.81. Common variables that influenced predictions included basal area, phenology, nitrogen, leaf score, and digestibility. Basal area was the most important single variable positively related to preference with an R2 value of 0.70 over all trials. Individual sugar analyses were not significantly (P>0.05) related to bites for most trials but became important from mid-June to mid-July. Equations which included sugar analyses (n=20), accounted for 73 to 87% of the variation in bites. However, basal area and phenology were the dominant variables in these equations. Therefore no single equation could be used to accurately predict preferences.