Understanding the effect of defoliation frequency and N fertilization on plant growth, forage yield, and quality of RS-2, a quackgrass [Elytrigia repens (L.) Nevski.] x bluebunch wheat grass [Pseudoroegneria spicata (Pursh.) Love] hybrid, will help promote efficient use of this hybrid in livestock production systems. Plants were fertilized with 0, 112, or 224 kg N ha-1 in spring 1988 and 1989, or with a 112 + 112 kg N ha-1 split in spring and summer. One set of plants was unmowed or mowed to a 5cm stubble height once in July or August in 1988 and another set was mowed initially in May, June, July, August, September, or October 1989 and monthly thereafter through October. Peak standing crop of unmowed plants was 3,470 kg ha-1 in 1988 and 5,850 kg ha-1 in 1989. In 1989 yields of fertilized plants exceeded those of unfertilized plants by 1,000 kg ha-1. In 1988, crude protein exceeded 12% in unmowed forage and in 1989 varied from 20% in May to 8% in August. After fertilization, crude protein was increased by 2 to 4 percentage units in 1988 and by 2 percentage units in 1989, but fertilization had no effect on in vitro digestible organic matter. Regrowth contained more crude protein (15-22%) and digestible organic matter (29-40%) than unmowed forage. Sequential harvesting enhanced quality of regrowth, but standing crops did not exceed 350 kg ha-1; except in June 1989. Sixty percent of the accumulated yield was harvested with the first mowing during May through August. Plots harvested initially in September and October were only harvested once. Our findings indicate an increase in forage yield potential and forage quality of RS-2 after harvesting and fertilizing the RS-2 hybrid.

Livestock have been a key factor in the development of civilization, but what will their role be in the future and how should the science of rangeland management change to meet the challenges of the future? In this paper I look at current grazing management in the context of paradigm shifts and scientific revolution. The impact of livestock on rangelands occurs primarily because livestock selectively defoliate the available herbage rather than indiscriminately consuming herbage according to its availability. Grazing management via the use of traditional grazing systems does not appreciably affect selective foraging behavior. Trends of the future that will affect societal demands and available technologies include: 1) no lack of resources or food; 2) increased concern for environmental quality; 3) greater demand for open space values of rangelands; and 4) geometric increase in the availability of technologies from molecular biology to solve management problems. The 4 principles of grazing management i.e., 1) timing, 2) distribution, 3) kind/class of livestock, and 4) stocking rate, will not change. Stocking rate is the most important variable in grazing management. If stocking rate is not near the proper level then regardless of other grazing management practices employed objectives will not be met. The ability to determine the proper stocking rate will be hindered by the inability to determine carrying capacity as it varies over time. To change the grazing habits of the animals we must work directly on the genetics of the animal. However, the way we manipulate and manage grazing animals will improve, and our ability to monitor the impact of grazing must also improve. In addition to commodity production, livestock grazed on natural plant communities will also have to simultaneously impact these communities to provide the types of habitat demanded by society. The most important emerging technology for the management of grazing livestock will be genetic manipulation using both classical selection procedures and genetic engineering. New technologies for monitoring impact of livestock on the rangeland resource and for setting and adjusting stocking rates will also be critical. Interdisciplinary research must be encouraged to meet the future demands.

Comparisons of vegetation dynamics of riparian plant communities under livestock use and exclusions over a 10 year period were quantified in a Northeastern Oregon riparian zone. We measured species frequency, richness, diversity, evenness, and livestock utilization in 8 plant communities. Livestock grazed the study area from late August until mid September at a rate of 1.3 to 1.8 ha/AUM. Utilization varied from > 70% in dry meadows to < 3% in cheatgrass dominated stands. Ungrazed dry and moist meadow communities had significantly lower (P lesser than or equal to 0.1) species richness and diversity when compared to grazed counterparts. In the most heavily grazed communities, ruderal and competitive ruderal species were favored by grazing disturbance. In exclosures of the same communities, competitive or competitive stress tolerant species were favored. Both height and density of woody riparian species were significantly greater in ungrazed gravel bar communities. Our results indicate that influences of herbivory on species diversity and eveness varies from 1 community to another and basing management recommendation on 1 component ignores the inherent complexity of riparian ecosystems.

Downy brome (Bromus tectorum L.) is an alien grass that dominates disturbed ground in shrub-steppe ecosystems of the western United States. Responses of downy brome to added nitrogen and water were evaluated using intact soil cores obtained from an old field. Gas exchange data were gathered at the leaf and canopy scales. Stomatal conductance and net photosynthesis rates were greater at the leaf scale than at the canopy scale, decreased with time from germination, and were weakly affected by treatments. Water-use efficiency was weakly related to time from germination and treatments. Biomass was greater in the nitrogen-plus-water (7.4 g) treatment, compared with water (3.6 g), nitrogen (4.5 g), and control (3.3 g) treatments. The leaf-area index varied like biomass at the end of the experiment. Shoot nitrogen was the same in the nitrogen (2.5%) and nitrogen-plus-water (2.5%) treatments, nearly twice the level in the control (1.5%) and water (1.3%) treatments. Nitrogen-use efficiency was highest in the control (67) and water (80) treatments and lowest in the nitrogen (41) and nitrogen-plus-water (43) treatments. The most significant conclusion of this work is that gas exchange was strongly related to the time from germination and little affected by water and nitrogen while growth characters were strongly affected only when water and nitrogen were added together.

Grazing distribution and grass utilization was evaluated in intensively managed fields in the southern Aspen Parkland near Kirriemuir, Alberta. Three fields, 130 ha in size (with dimensions .4 X 3.2 km) were grazed by 1,000 cow/calf pairs for 5 days each. Stock water was accessible only from one end of each field. Grazing distribution was evaluated by monitoring grass utilization daily during grazing and after grazing at 0.1, 0.8, 1.6, 2.4, and 3.1 km from water. Final utilization did not differ within fields, except for a decline at the maximum distance from water (3.1 km). Temporal utilization patterns existed and could best be described as a wave, with defoliation beginning near the water source on day 1 of grazing and proceeding outward from water until the ends of the fields were grazed on day 5. Final utilization was uniform; selective grazing of areas close to water was not removed by intensive management, but was masked by a rapid rate of defoliation.

We examined the diets of reintroduced tule elk (Cervus elaphus nannodes Merriam) and resident Columbian black-tailed deer (Odocoileus hemionus columbianus Richardson) inhabiting the coastal prairie-scrub mosaic of Tomales Point, the northernmost portion of the Point Reyes Peninsula, Calif., during 1979-81. The elk diet differed between years whereas the deer diet did not. The pattern of seasonal quality of elk and deer diets, as measured by fecal nitrogen (FN) was similar between species and years. This was achieved although botanical composition differed between herbivores in some seasons. Dietary overlap was lowest in the wet winter months when fecal nitrogen was highest and vegetative standing crop was lowest. Conversely, dietary overlap was highest in the dry summer months when fecal nitrogen was lowest and vegetative standing crop highest. Both herbivore species showed selection and avoidance of certain plant species in June of both years. These findings are compared to other cervid-habitat systems.

Tall larkspur (Delphinium barbeyi L. Huth.) toxicosis of cattle is a serious problem on western USA mountain rangelands. Manipulating the ruminal environment may decrease the susceptibility of cattle to larkspur intoxication. The cholinergic drug carbachol can greatly increase salivary flow and fluid passage rate in ruminants. Our objectives were to: (1) determine if chronic administration of carbachol altered ruminal fluid passage rate, ruminal pH, or water intake in grazing cattle, and (2) evaluate mineral salt supplementation as a prophylactic procedure for cattle grazing larkspur-infested rangelands. The study was conducted during summer of 1990 and 1991 near Yampa, Colo. Twelve heifers were divided randomly into 3 treatment groups: (1) carbachol administered at 0.01 mg kg-1 day-1 via subcutaneous osmotic minipumps; (2) mineral-salt supplement dosed intraruminally at 0.25 g kg-1 day-1; and (3) controls. Administration of carbachol either had no effect or a negative effect on ruminal fluid passage rate, ruminal pH, saliva production, and water intake compared with the controls. Carbachol had few consistent effects on serum electrolyte concentrations compared to the controls. Treatments did not influence cattle diet selection; cattle ate no larkspur during 1990, but selected larkspur for 16% of their diets during August, 1991. There was no indication that supplementation with mineral salt would attenuate larkspur toxicosis through increased dilution rates, or decreased larkspur consumption. Our results indicate that neither carbachol nor mineral supplementation will reduce animal susceptibility to larkspur toxicosis.