Normally the oceanic climate of Scotland maintains soils at low levels of soil water deficit. Field data for such a year are presented and compared with those for an unusually dry year, with the objective of assessing to what degree dry spells might limit herbage production in upland pastures. One meter square plots were sampled on selected dates on reseeded pastures growing on each of 3 cambisols, each derived from different parent materials. The swards were unfertilized and maintained at nominal heights of 2, 4, 7, and 10 cm by cutting every 2 or 3 weeks to manipulate growth and demand for P and N. Overall yield was 25 to 50% lower in the dry year compared with an average year. Peaks and troughs in growth rates, measured as yield at each cutting, and in P and N content, corresponded to changes in soil water deficit in the top meter of soil. The linear correlation coefficient between soil water deficit and growth rate was -0.894 (P = 0.001). Although there was some variation in volumetric water content between soils, soil water deficits were similar in all the cambisols. Yields and nutrient contents were generally similar for herbage harvested from the 2 soils having basic parent material (one a eutric and one a dystric cambisol) and lower on the dystric cambisol derived from schists. The effects of water content largely over-rode cutting treatments, demonstrating that dry spells occasionally occurring in the oceanic climate of Scotland can significantly affect grassland production.

There is a dearth of knowledge on the selection and utilization of Columbia milkvetch (Astragalus miser Dougl. ex Hook. var. serotinus) by grazing livestock on rangelands in British Columbia. Four grazing trials were conducted with cattle on Columbia milkvetch range in southern interior British Columbia. In the first 2 trials during 1990 and 1991 cattle grazed an upper grassland site in late spring. In 1992 and 1993, the animals grazed a lodgepole pine forest site during early summer. The density of Columbia milkvetch and its basal area were similar at both locations. The Columbia milkvetch was not a preferred species on the grassland site as indicated by the bite count technique that determined its percentage in the diet. Consumption of Columbia milkvetch increased gradually as other forage species were preferentially selected and depleted. On the grasslands, consumption of Columbia milkvetch by individual animals did not show an addictive pattern. At the forest site, utilization of Columbia milkvetch was determined on a weekly basis during 1992 and on a biweekly basis during 1993 by paired plots. In contrast to the grassland site, Columbia milkvetch was a preferred species at the forest site where it was utilized to a greater extent than grasses or other forbs. Approximately 80% of the Columbia milkvetch was utilized during 1992 and 60% during 1993, which was significantly greater than the utilization of grasses or other forbs. Forage nutrient analysis at the forest site indicated Columbia milkvetch had higher crude protein and lower ADF content than other forages but it caused livestock poisoning in 1993.

Proposals outlined in Rangeland Reform '94 have been perceived to greatly alter grazing use on public lands. In addition to new rules and regulations, the grazing fee would double under this reform proposal. The debate about these controversial policies would be expected to affect the market value of public kind grazing permits. Regression models were developed using over 700 ranch sales to determine recent trends in market value for New Mexico ranches, including public land ranches. After 1988, nominal deeded ranch values were found to have increased by 3% per annum, but remained unchanged in 1992 constant dollars. This follows a 50% decline in real value from 1982-88. Ranches heavily dependent on Bureau of Land Management (BLM) land for grazing capacity decreased in real value by about 1.8% per annum over the 1988-94 study period. The United States Forest Service (USFS) has recently had the most controversial land use polices and the highest average total grazing costs. This has been reflected in the market value of USFS ranches, with a continued decrease in permit value; USFS ranches in New Mexico have lost 75% of their real value since 1982. Doubling grazing fees on New Mexico state trust lands contributed to a downward trend in leasehold value. Somewhat surprising, given the higher grazing fee on state trust lands, these permits increased in market value in both real (1.7% per year) and nominal (5% per year) terms after controversy about state lands subsided and federal land policies became more controversial.

Mineral concentrations of range grasses are often below that required by grazing livestock. Limited information is available on forage mineral concentrations for the Northern Great Plains and there is little data on factors influencing concentrations of forage minerals throughout the year. Therefore, a study was conducted to evaluate special and temporal variations in mineral concentrations of major forage species in the Northern Great Plains. Herbage was sampled from 4 replicates on each of 2 soils in July, August, and September 1991, April, June, July, August, and September 1992, and April 1993. Herbage was sorted by species grouping and by live and dead tissue classes. Analyses on herbage included Ca, P, Mg, K, Na, Zn, Cu, Mn, and Mo. For western wheatgrass [Pascopyrum smithii (Rydb.) Love] and annual bromes [Bromus spp.], Zn and all macrominerals except Na were greater in live than in dead tissue. Live tissues of all other species groupings contained greater amounts of P and K than did dead tissue. Live tissue Mg concentrations were greater than dead tissue concentrations for other cool-season and warm season grasses. Manganese concentrations were greater in live than dead annual brome tissues, while Cu was greater in dear than live tissue. Dead sedge tissue contained greater concentrations of Ca than live tissue. Soil type affected several nutrient but this was partially related to soil effects upon composition of species groupings and live:dead ratios. Minerals most likely to be found in quantities less than required for animal production were P, Na, K, Zn, and Cu.

Fringed sagebrush (Artemisia frigida Willd.), the most common dicotyledonous species in the Northern Mixed Prairie, often increases dramatically following disturbance. It was hypothesized that the increase could be due to release of established plants, increased recruitment of plants, or both. Experiments were conducted on a sandy range site in central Saskatchewan. Tillage, clipping, litter removal, and a combination of clipping+litter removal were compared to an undisturbed control to determine their effects on emergence and survival of fringed sagebrush seedlings and growth of established plants. In no circumstance was seedling emergence or plant growth greater in the undisturbed control than in the disturbed sward. Emergence of fringed sagebrush seedlings increased almost 80-fold the second year after tillage at 1 site, but emergence was not altered relative to the control by clipping, litter removal, or clipping+litter removal Averaged across treatments, 52 to 98% of the seedlings emerged in May and June, and 47 to 99% of these seedlings survived through the growing season and winter. Plants grew fastest in June when precipitation was highest and temperatures were moderate. Growth of plants was improved 2- to 3-fold by tillage the second year; this stimulation in growth was due to the removal of competition. Activities that reduce or remove vegetation and create bare soil surfaces promote emergence and growth of fringed sagebrush on the Northern Great Plains. Most seedlings of fringed sagebrush emerge in spring and early summer, enabling them to temporally exploit the period for optimal growth. Fringed sagebrush is well adapted to persist in Northern Mixed Prairie in a successional continuum from early to late seral stages.

Broom snakeweed [Gutierrezia sarothrae (Pursh) Britt. &Rusby] is a rangeland weed widely distributed in the western United States. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) uptake and picloram-induced ethylene production by broom snakeweed grown in the field were determined every 2 to 4 weeks over 36 months. For each collection date, picloram uptake and concentration in the tissue ranged from 1.5 to 46.2% of applied and 0.2 to 4.7 nmol g-1 fresh wt, respectively. Of the measured environmental variables, average precipitation and average minimum temperature 7 days prior to treatment best predicted picloram uptake and concentration in the tissue, suggesting that warmer temperatures and precipitation previous to application contribute to picloram uptake. Average minimum temperature alone also provided a good predictor for picloram concentration in the tissue. For each collection date, picloram-induced ethylene production by total tissue ranged from 50 to 791% of control. Picloram-induced ethylene production by total tissue was best predicted by the precipitation and minimum temperature 7 days prior to treatment and picloram concentration in the tissue. Therefore, the amount of picloram absorbed and the environment prior to application both contribute to the physiological sensitivity of broom snakeweed to picloram. Picloram uptake and picloram-induced ethylene production were greatest in July and August, when plants were in the phenological stages of shoot regreening or flower bud emergence and when temperatures and precipitation were high. Previous field studies have shown broom snakeweed is most responsive to field picloram application in the post-bloom stage from October to December or in April and May with high moisture and soil temperature conditions; therefore, it appears that changes in uptake and physiological sensitivity as measured by picloram-induced ethylene production are not the only factors controlling differential sensitivity to picloram.

Fecal microhistology was used to estimate botanical composition of samples taken from Hereford (N = 11), Angus (N = 11) and Brangus (N = 37) 3 to 5 year-old cows in 3 seasons (October, 1991 and January and July, 1992) and from Hereford (N = 10), Angus (N = 9) and Brangus (N = 34) calves in October. Breed differences in botanical composition of diets and relationships between dam and offspring botanical composition of diets were examined. Breed differences were observed for cows in all 3 seasons and for calves in October. Brangus cows showed greater preference (P < 0.05) for Sporobolus than Hereford cows in October, January, and July. Brangus cows also showed greater preference for Sporobolus than Angus cows in January and July. Brangus and Angus calves showed greater preference for Sporobolus than Hereford calves in October (P < 0.05). Brangus cows had a stronger preference for Yucca and total shrubs in January than either Hereford or Angus cows. Hereford cows and calves had stronger preference for Aristida than either Angus or Brangus in October (P < 0.05). Regression of October calf botanical components on dam botanical components indicated significant relationships for only 2 genera, Aristida (P < 0.01) and Sporobolus (P< 0.06). These data suggest that genetic composition of the animal is an important factor determining utilization of key plant species on Chihuahuan desrt ranges.

Cattle trampling of endangered plants, certain animal species, and ground nests may be a management concern on rangeland. Researchers need theoretical models of trampling loss to assist in design of studies and interpretation of results. Managers can use such models to assist in grazing management decisions. We present null (random background) models for predicting probability of trampling loss, explore the effects of failure of assumptions underlying these models, and develop alternative models for dealing with nonrandom grazing and nonrandom placement of vulnerable objects. The null models predict that if time-based stocking rate (head-days ha-1) is held constant and 1 pasture is grazed under several rotation schedules (a study design used to simulate rotational grazing), or if 1 pasture is divided into n paddocks through which 1 herd rotates, the probability of trampling is operationally constant. This qualitative prediction holds when grazing is nonindependent and nonrandom, competing risks exist, and objects subject to trampling are dispersed nonrandomly. Quantitative predictions of the null models do not hold under nonrandom grazing, which is expected to reduce probability of trampling. Researchers can use predictions of the models as a priori hypotheses. If empirical results deviate from the predictions, then researchers should search for the underlying cause-effect mechanisms. For management, the models indicate that trampling varies with livestock density and time grazed but is independent of herd rotation.