Several studies have examined the impact of woody plant (i.e., brush) management efforts on mesquite (Prosopis glandulosa Torr.) cover and associated ecological impacts, but little research has been done on spatial attributes of vegetation following mesquite management treatments. This study examined the effects of above-ground mortality (triclopyr or 2,4,5-T) and whole-plant mortality (clopyralid or triclopyr+clopyralid) mesquite herbicide treatments on the canopy cover and spatial pattern of vegetation in a mesquite savanna and the associated ecological and management implications. A GIS and landscape analysis based on classified color-infrared aerial photos were used to quantify the spatial patterns of woody and non-woody vegetation. The results indicate long-term (> 20 year) persistence of disturbance effects on the amount and spatial pattern of woody vegetation. Significant differences in spatial pattern were found between the herbicide treatments and the non-treated plots, as well as between the above-ground mortality (AGM) and whole-plant mortality (WPM) herbicide treatments. The differential changes in the amount and spatial distribution of woody cover under different treatments resulted in substantially different spatial distributions of non-woody vegetation with respect to distance to nearest woody vegetation. These spatial variations may influence production and zonation of herbaceous vegetation due to modified shading and root competition from mesquite. Our results support observations of differential rates of mesquite seedling recruitment and establishment between treatment types. We conclude that consideration of spatial pattern should be an important component of future brush management plans.

Water availability in the germination stage of plants is crucial for seed germination and as a resource for developing seedlings. The effect of osmotic potential on percent germination and time to germination for big sacaton (Sporobolus wrightii Munro) and Arizona fescue (Festuca arizonica Vasey) was investigated. We predicted that seeds native to semi-arid environments would germinate at osmotic potentials less negative than about -1.5 MPa, the permanent wilting point (PWP) of many agronomic grasses. In addition, the systemic, asexual endophyte Neotyphodium is transmitted through the seed in Arizona fescue and is thought to increase germination of its host. Therefore, we also tested for an effect of the endophyte on germination and time to germination of Arizona fescue under varying osmotic potentials. To test for minimum osmotic potential supporting germination, big sacaton and Arizona fescue seeds were placed on acetate membranes in contact with PEG solutions of varying osmotic potentials for 2 weeks. Both grasses germinated at 50% of maximum germination (at soil saturation) at and below the standard PWP (-1.5 Mpa). Big sacaton and Arizona fescue germinated at 64% and 60% at -1.5 MPa, respectively, and Arizona fescue germinated at 35% at -1.8 MPa (70% was the maximum at saturation). The presence of the Neotyphodium endophyte did not affect percent or time to germination of Arizona fescue at any of the osmotic potentials tested.

True mountain mahogany (Cercocarpus montanus Raf.) provides nutritional winter forage for big game species in the mountain brush zone. To determine browsing effects, animal use, percent vegetation cover, and shrub dimensions were measured inside and outside exclosures up to 7 years old on 4 sites on the North Slope of the Unita Mountains, and at an exclosure 50 years old in the Wasatch Mountains, Utah. Utilization was measured in an associated twig demography study. Winter big game use increased from 1997 to 1999 at the North Slope. Utilization of annual growth ranged from 21 to over 300%, depending on the site and year and did not necessarily parallel animal use. Greater than 100% utilization of annual growth resulted when previous years' wood was browsed. There was little difference in vegetation cover, species richness, and diversity inside and outside the exclosures, but mountain mahogany had lower cover and smaller size outside than inside the exclosures at 3 North Slope sites. Mahogany cover was similar, but width and breadth of shrubs were smaller outside than inside the > 50-year old exclosure in the Wasatch Mountains. Browsed shrubs maintained their size from 1995 to 1999 at the North Slope, despite over 100 % utilization of annual growth at 3 of the sites in at least 1 year. True mountain mahogany is highly tolerant of winter browsing, and can compensate for > 100% utilization of annual growth by increased growth during wet years. However, continued use of over 100 % of annual growth could reduce cover, shrub size, and forage production during years of lower resource availability. A practical management approach is to monitor cover and size of shrubs inside and outside well-placed exclosures across the winter range over time, and reduce herd numbers as appropriate to allow browsed shrubs to maintain or reach the size of unbrowsed shrubs when their growth has leveled off after a few years of exclusion.

True mountain mahogany (Cercocarpus montanus Raf.) compensates for annual growth lost to browsing under conditions of high resource availability. To develop better guidelines for its management for big game winter forage, twig demography was studied under natural herbivory and resource availability inside and outside exclosures at 1 site in the Wasatch Mountains and on 4 sites on the North Slope of the Uinta Mountains, Utah. Annual and previous years' twig lengths, as well as location and numbers of flowers and seeds were diagrammed on branches of browsed and unbrowsed shrubs in the spring or summer and fall between 1996 and 1999. Annual twig growth and flower and seed numbers of both browsed and unbrowsed shrubs were greatest in 1997 or 1998 when precipitation was highest. Utilization of annual growth varied among sites within a year and among years within a site and ranged from < 21 % to > 300 % when previous years' growth was browsed. Despite differences in utilization, browsed twigs compensated similarly for length lost to herbivory, so that total twig lengths remained the same over the course of the study. Although twigs on unbrowsed shrubs had less annual growth per unit branch length than those on browsed shrubs, lack of length lost to herbivory resulted in an increase in total twig length over time. Years of high resource availability are important in allowing grazing tolerant shrubs such as true mountain mahogany to compensate for years of heavy utilization. Flower and seed numbers were much higher (P < 0.05) on unbrowsed than browsed shrubs. Compensatory growth was enough to maintain, but not increase total twig lengths after high utilization (> 100 %) even on years of high resource availability.

Several U.S. rangeland areas recently have been designated as national monuments to protect scientifically or culturally important resources. Typically recreation and livestock uses have been retained in these areas. Because some people believe protection and use are incompatible, and because monument designation can increase public scrutiny of management while attracting new visitors to the area, we surveyed hunters and hikers in the Grand Staircase-Escalante National Monument, Utah, about their perceptions of livestock grazing in the monument. We examined associations between visitors' personal characteristics and their reports of how livestock grazing and multiple-use management affect recreation experiences. Recreation activity type was a significant predictor of experience effects, but we found no evidence that the act of designating a national monument itself affected experiences. Locations of current and childhood residence also were significantly associated with experience effects. Because designation tends to attract certain types of visitors more than others, creating rangeland national monuments may foster increased conflict between recreation and livestock grazing uses in those areas.

Non-selective grazing (NSG) is a relatively novel way of farming livestock in the Nama Karoo of South Africa. Our key question was how heavy grazing under this high-intensity, low-frequency grazing system would impact on certain soil properties. The study was designed to compare the impacts of NSG (treatment) with no grazing (control) in terms of: (1) amount of soil organic carbon (OC); (2) soil microbial respiration rates; (3) soil stability and infiltration properties. The treatment significantly lowered the amount of OC in the topsoil. Microbial respiration rates corresponded with the fertile patch matrix in both treatment and control with significantly higher respiration rates measured under plants compared to open, unvegetated areas. Respiration rates in treatment open areas were significantly higher than in control open areas. There was a trend (P < 0.1) for higher aggregate stability, final infiltration rate and cumulative infiltration for treatment open soils compared to controls during an initial rain event of 44 mm hour-1 in a rainfall simulator. During a second rain event on sealed soils only aggregate stability was significantly higher for treatment compared to control soils. We conclude that the short-duration, low-frequency, intensive herbivory by livestock under the non-selective grazing system resulted in a more active microbial community, which turned over organic matter more rapidly and led to higher soil stability and infiltration capacity of open, unvegetated soils. We present this as an example of conditions where herding by high densities of large herbivores can have positive impacts on soil quality.

High quality forage for spring and autumn grazing can be obtained from Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], a cool-season bunchgrass. However, little is known about mineral concentrations critical to livestock production, especially in the relatively new tetraploid plants. A knowledge of plant mineral concentrations and how they can be manipulated to more nearly meet animal requirements is necessary to optimize animal production. A study was undertaken to determine the extent that concentrations of critical minerals in leaf and stem tissue of Russian wildrye were affected by ploidy level, growing-season water (50 and 150% of average), and N fertilizer (10 and 134 kg N ha-1). Plants were sampled at vegetative, boot, anthesis, and anthesis plus 10-day stages of maturity in 1994, 1995, and 1996. Ploidy level resulted in small but significant differences in some mineral concentrations, with diploid plants usually having higher levels. An exception was P in stem tissue. This finding indicates that in breeding and selection for other traits, forage quality was not adversely affected. Growing-season water level also had minimal effects on mineral concentrations, except for P which was enhanced (P < 0.05) by greater amounts of soil water. Fertilizer N increased forage levels of Ca, K, Cu, and Zn, and decreased levels of P. Higher concentrations of K are not desirable, because they increase the possibility of a grass tetany problem. Advancing plant maturity caused a decrease in P and Zn concentrations, but Ca and Mg in leaf tissue increased as plants matured. These results suggest that concentrations of P, Ca, Mg, and Cu were marginal for high producing cattle at some stages of maturity, but we found the effects of nitrogen and growing-season water did not result in leaf and stem mineral concentration changes that would adversely affect the safety and nutritive quality of Russian wildrye.

Environmental concerns of using pesticides on public lands have greatly reduced the use of herbicides to control tall larkspur (Delphinium barbeyi Huth). An alternative method of control used ammonium sulfate placed at the base of individual plants. The objective of this study was to determine the mechanism by which fertilizers kill tall larkspur. We hypothesize the salt from the fertilizers kill the plant. We applied ammonium sulfate, ammonium nitrate and sodium chloride at equivalent salt concentrations and evaluated their effect on tall larkspur plants. There was no difference among treatments in larkspur mortality (P > 0.10). The high rate of all treatments (ammonium sulfate 400 g plant-1, ammonium nitrate 264 g, and sodium chloride 180 g, at equivalent salt concentrations) killed greater than 70% of larkspur plants. We conclude the salt in fertilizers kills tall larkspur, not the nitrogen. It is necessary to place the fertilizer or salt at the base of the plant to concentrate it in the root zone, rather than broadcast it. At the end of the study, bare areas left around the dead tall larkspur plants were only 13% of the original size of the tall larkspur plants at Yampa Colo. and Cedar Ut., and 46% at Emery Ut., indicating the surrounding vegetation was quickly filling in the vacated space. The relative cost of materials per plant for both ammonium sulfate and nitrate was 12.9 cents, and 2.6 cents for salt.

Community-level (per unit area) and individual tiller reproductive biomass inside and outside of long-term exclosures on the northern winter range of Yellowstone National Park, USA were compared. Grazed areas had twice the number of reproductive tillers m-2 (186 compared to 88 tillers m-2), and greater total reproductive biomass m-2 than ungrazed plots (13 compared to 7 g m-2). In contrast, seed number tiller-1 was greater for grasses in exclosures. Because of these offsetting responses, seed production (nom-2) was unaffected by herbivores. On an area basis, grazed grasses allocated proportionally more biomass to reproduction (reproductive biomass/aboveground biomass) than ungrazed grasses. We propose that altered plant demography and morphology following defoliation explain how grazers might increase the allocation of biomass to reproduction in Yellowstone grasslands. To understand these results in light of ecological and agronomic studies, we reviewed literature from 118 sources that reported the effects of defoliation on the production of reproductive biomass. The review suggested that the results of herbivory or defoliation on plant reproductive biomass depended on the scale of measurement (community vs. plant). In addition, timing of grazing or defoliation emerged as a key factor that determined whether sexual reproduction was inhibited. Like the early season grazing that is typical of Yellowstone's northern winter range, studies often showed that early season defoliation stimulated production of community-level reproductive biomass. Our results rectify disagreements in the literature that ultimately derive from differences in either timing of defoliation or measurement scale.

Clubmoss (Selaginella densa Rydb.), a low growing, vascular cryptogam forms carpet-like mats that cover up to 80% of the ground in the Northern Mixed Prairie. Many range managers believe clubmoss competes with grasses for water or intercepts precipitation and negatively affects plant water relations and productivity. The objective of these studies was to test the hypothesis that precipitation has greater effects on leaf xylem water potentials (Leafxwp) and plant productivity than clubmoss. Studies examined the effects of clubmoss on Leafxwp of Junegrass (Koeleria cristata Pers.) and blue grama (Bouteloua gracilis [HBK.] Lag.), and productivity of forbs and graminoids by: 1) irrigating or reducing precipitation relative to natural precipitation; 2) removing clubmoss relative to clubmoss present, and; 3) irrigating with 0.0 to 25 mm of water when clubmoss was present or removed. Leafxwp of Junegrass and blue grama were unaffected by clubmoss through the growing season (P = 0.33), but Leafxwp were lowest (P or = 0.05) when precipitation was reduced relative to the control and when irrigating. Standing crop of forbs was similar in the control and clubmoss removal treatment (P = 0.22) and among precipitation treatments (P = 0.13), averaging 28 g m-2 (SE = 2.2). Graminoid standing crop was unaffected by clubmoss (P = 0.35) and was greatest (P = 0.02) when irrigated (74 g m-2), intermediate in the control (53 g m-2), and least (36 g m-2) with reduced precipitation (SE = 8.7). Clubmoss did not affect (P = 0.70) total standing crop; total standing crop declined from 102 g m-2 when irrigated to 76 g m-2 in the control, and 69 g m-2 (SE = 9.0) with reduced precipitation. Clubmoss had no influence (P = 0.06) on Leafxwp when irrigated with 0 to 25 mm of water. The decline in Leafxwp from 1 to 7 days after irrigation was the product of the interacting effects of the amount of water applied and days after irrigation (P = 0.03). More than 10 mm of irrigation water were required to impart a significant increase (P < 0.05) in Leafxwp. The hypothesis that clubmoss reduces productivity of associated plants in the Northern Mixed Prairie by increasing water stress is rejected. Similarly clubmoss does not reduce plant water stress or increase production. Precipitation amounts overshadow any effects clubmoss has on Leafxwp and plant production. Range managers in the Northern Mixed Prairie may want to consider maximizing the effectiveness of precipitation in this water-limited environment instead of focusing on reducing or attempting to eliminate clubmoss.