The effects of grazing management systems on plant communities in the Great Basin are largely unknown. This study is a quantitative description of the response of vegetation from 1973 to 1983 on the Goldbanks and Pueblo Mountain cattle allotments in northern Nevada managed under a 3-pasture rest-rotation grazing system. Shrub canopy cover, basal-area cover of herbaceous species, and frequency of occurrence of all species were used to estimate change in vegetation characteristics on macroplots representing 9 community types. Forage use was heavy in all years and averaged 65% in June, 75% in July and August, and 80% in October. Sandberg bluegrass [Poa sandbergii Vasey] and sagebrush [Artemisia spp. L.] were the most responsive species. Long-term increases or decreases in frequency and cover of desirable grasses were found on very few sites. Perennial forbs increased on a number of sites. Short-term changes in frequency and cover of Sandberg bluegrass and in frequency of sagebrush seedlings and young plants were attributed to a sequence of dry and wet years and to level of competition from herbaceous species. Frequency data indicated more significant changes in species composition than did cover data. The management system, forage utilization levels imposed, and climatic conditions present maintained prestudy range condition throughout the study on most sites at Pueblo Mountain. An increase in frequency and cover of Wyoming big sagebrush [A. tridentata wyomingensis Beetle] and a decrease in the cover of desirable grasses at Goldbanks suggest a downward trend in range condition on some sites where either Thurber needlegrass [Stipa thurberiana Piper] or bluebunch wheatgrass [Agropyron spicatum (Pursh) Scribn. & Smith] is the potential dominant grass.

A 6-year study was conducted to evaluate the response of California annual range to triennial applications of sulfur only and sulfur plus nitrogen fertilizer. Range response was evaluated in terms of length of the green season, steer weight gain, total beef production and steer days of grazing/ha. Neither fertilization treatment consistently lengthened the green season nor influenced steer weight gain compared to nonfertilized range. Steer days of grazing and total beef production/ha were greatest on sulfur plus nitrogen-treated range, intermediate on sulfur only-fertilized range and least on nonfertilized range. Sulfur only-fertilized range increased beef production about 60 kg/ha compared to nonfertilized range, and range fertilized with sulfur plus nitrogen increased beef production nearly 50 kg/ha more than sulfur only-fertilized range.

Most authors have suggested that the rumen's capability to digest foodstuff is influenced by the conditions resulting from microbial populations which are regulated by composition of the diets. Presumably the greatest ecological differences within the rumens of cattle grazing tropical semiarid range plants would be during wet and dry seasons. Rumen dry matter digestion indexes were determined by the nylon bag technique during wet and dry seasons for 4 different plant materials at the National Range Research Station near Kiboko, Kenya. The rumen digestive capability of 3 Zebu steers was not different between wet and dry seasons when these rumen fistulates selected their own foods from natural range vegetation.

Leaves of 6 Atriplex species (saltbush) grown in Saudi Arabia were studied for their nutritive characteristics. Crude protein contents varied between 16.7 - 25.2%, crude fat between 1.0 - 1.6%, crude fiber between 7.8 - 10.4%, and ash between 18.5 - 27.2%, on a dry matter basis. A. undulata had the lowest and A. nummularia had the highest protein and fiber contents. Ash content was lowest in A. canescens and highest in A. undulata. The level of Na was extremely low (0.21%) in A. canescens compared to that in the other species (2.38 - 5.57%). The level of K (6.06%) was highest in A. canescens compared to 2.48 - 3.54% in other species. Ca content was significantly higher in A. vesicaria (2.48%) than that in the remaining species (1.12 - 1.50%). Variations in the levels of P, Mg, Fe, Zn, Cu, and Mn were only minor. Sulphur amino acids (methionine + cystine) were the most deficient essential amino acids in all species (chemical score = 45 - 61) while lysine contents were 75 - >100% of the FAO/WHO (1973) reference protein. Predicted digestible dry matter ranged between 74.5 - 78.8% and digestible energy (M Cals/Kg) between 3.215-3.399. These data suggest that Atriplex leaves as a range forage for livestock would have good nutritive value.

Range forage yields obtained over a 50-year period at the Research Substation near Manyberries in southeastern Alberta were analyzed in relation to several climatic factors. The basic variables were precipitation, pan evaporation, temperature, hours of sunlight, and wind velocity. The precipitation from April through July was highly correlated with range forage production and this relationship could be utilized to predict the annual forage production by 1 August each year. A slightly better correlation was obtained when range forage production was related to the total of the previous September plus the current April through July precipitation. Pan evaporation totals, mean temperature, and hours of sunlight were negatively correlated with forage production, while wind velocity during the growing season showed a low relationship to forage production. Stepwise regression analysis showed that the inclusion of May and June mean temperatures with June and July precipitation accounted for 63% of the variation in range forage production. The predicted forage yield would be useful in making management decisions or adjustments, especially during drought periods, while the long-term forage yield data can be utilized in range forage models or in validating their effectiveness.

In the northern Great Basin, populations of black-tailed jackrabbits (Lepus californicus) are cyclic, reaching high densities at approximately 10-year intervals. This project examined impacts of jackrabbits during a peak in their cycle on sagebrush-steppe vegetation in southeastern Idaho. Total vascular plant cover was significantly lower on plots open to jackrabbit herbivory than on exclosure plots, but in no case was cover of a specific species significantly reduced on open plots. The most severe impacts were on shrubs during winter; most aboveground tissues of both winterfat (Ceratoides lanata) and green rabbitbrush (Chrysothamnus viscidiflorus) plants were completely eaten by spring. However, these impacts were largely ameliorated by compensatory growth during the following growing season, and there was no difference in total biomass for either species between the open and protected plots by July. New growth of winterfat plants that had been browsed the previous winter was significantly greater than that of protected plants. Thus, although the cumulative effects of herbivory reduced total plant cover, no single species was irreparably impacted. Over a year, jackrabbits exert feeding pressure on nearly all of the important species in these communities; therefore, these hares do not appear to apply differential grazing pressure that would alter the course of vegetation development on northern Great Basin rangelands.

Revegetation on raw bentonite spoil with or without treatments is often more practical than replacing topsoil in areas where it is scarce or nonexistent. The effect of raw bentonite spoil treated with ponderosa pine sawdust on plant survival and growth was compared to other treatments including perlite, gypsum, straw, vermiculite, and no treatment. Plants tested were the drought- and salt-resistant species of fourwing saltbush (Atriplex canescens (Pursh) Nutt.), rubber rabbitbrush (Chrysothamnus nauseousus (Pallo) Britt.), big sagebrush (Artemisia tridentata tridentata Nutt.), common winterfat (Ceratoides lanata (Pursh) Moq.), Rocky Mountain juniper (Juniperus scopulorum Sarg.), Russian olive (Elaegnus angustifolia L.), common yarrow (Achillea millifolium L.), and desert globemallow (Sphaeralcea ambigua Gray). Desert globemallow, fourwing saltbush, and rubber rabbitbrush had substantial growth and survival on sawdust, perlite, and vermiculite treated spoil. The growth promoting effect of sawdust is particularly promising; it is readily available and cost is minimal.

Vegetation, small rodents, and birds were sampled during the growing seasons of 2 years on prairie dog (Cynomys ludovicianus) colonies and adjacent mixed-grass prairie in western South Dakota. Prairie dog grazing decreased mulch cover, maximum height of vegetation, plant species richness, and tended to decrease live plant canopy cover compared to that on ungrazed mixed-grass prairie. Buffalograss (Buchloe dactyloides) was the dominant plant on prairie dog towns and western wheatgrass (Agropyron smithii) and blue grama (Bouteloua gracilis) were most common on mixed-grass prairie sites. Prairie dog towns supported greater densities of small rodents but significantly fewer species compared to undisturbed mixed-grass sites. Deer mice (Peromyscus maniculatus) and northern grasshopper mice (Onychomys leucogaster) were more abundant on prairie dog towns than on undisturbed mixed-grass sites. Density and species richness of birds were significantly greater on prairie dog towns. Horned larks (Eremophila alpestris) were most common on prairie dog towns, whereas western meadowlarks (Sturnella neglecta) were most common on mixed-grass prairie.

Soil acidity resulting from nitrification of ammonium in fertilizer can limit plant growth. In this study on weeping lovegrass (Eragrostis curvula (Schrad.) Nees) and Caucasian bluestem (Bothriochloa caucasica (Trin.) Hubb) pastures on sandy soil in northwestern Oklahoma, 20 years of N fertilization at an average rate of 37 kg N ha-1 yr-1 reduced the pH of the surface 5 cm of soil from 6.7 to 5.3. Sweetclover (Melilotus officinalis (L.) Lam.) and alfalfa (Medicago sativa L.) had symptoms of manganese toxicity when grown in the acidified soil in a glasshouse. The growth of warm-season grasses was not adversely affected when grown in the acidified soil. The lime requirement of the acidified soil was 896 kg CaCO3 ha-1 greater than the lime requirement of adjacent unfertilized pastures. The lime requirements in relation to the amount of acid producing N fertilizer applied was similar to or less than lime requirements reported in the literature for larger N applications to farmlands. Continued use of N fertilizer at low rates will eventually require that once near-neutral soils be limed if species sensitive to acid soil are grown.

The effects of 4 stocking rates (1.2, 1.6, 2.4, and 4.8 AUM/ha) on cattle production were examined, over a 35-year period, on a Rough Fescue (Festuca scabrella Torr.) Grassland. Forage productivity was reduced at the higher stocking rates. This resulted in a shortened grazing season in the field stocked at 4.8 AUM/ha. Although individual animals' weights decreased with increased stocking rate, cattle gains per unit area increased. Average daily gain of cows was greatest in May but declined to become a loss in September. Calves showed maximum gains from June to July and never lost weight. Stocking rate affected the relative magnitude of average daily gain as well as the trend over the grazing season.