Few ecological sites have been described sufficiently to interpret the specific functions and processes unique to riverine riparian areas. The utility of using ecological site concepts for riparian classification has also been debated due to the dynamic nature of the systems and the paucity of unaltered vegetation. We evaluated riparian sites associated with streams or rivers in 9 western states to determine the feasibility of using ecological site concepts in describing and evaluating riverine riparian ecosystems. Associated water features must be described in riparian site descriptions to establish relationships and understand "process pathways." A concept of "site progression" is proposed to differentiate between secondary succession associated with vegetation changes within a given physical environment and physical "state" changes that lead to a "new" or different potential natural plant community (i.e., a change in ecological site and secondary succession sequences). We have concluded that ecological site classification and inventory techniques utilized on uplands can be used on riparian areas with some enhancements to maintain consistency in evaluations at a "management unit" level.

Competition from other plant species may inhibit establishment and reduce phytomass production of blue grama [Bouteloua gracilis (H.B.K.) Griffiths] on rangeland. Varying levels of competition were achieved by transplanting four-week-old blue grama seedlings into openings 0, 4, 8, or 16 cm in diameter in a western wheatgrass [Pascopyrum smithii (Rydb.) A. Love] sod or in fallow soil. After the first growing season, 42, 79, 88, and 92% of blue grama seedlings survived in 0, 4, 8, and 16 cm openings, respectively, in sod. All plants survived the first growing season in all treatments on fallow, but 86% of the plants in fallow died the first winter. In the first growing season, blue grama plants averaged over 13 seed heads per plant in fallow but less than 1 seed head per plant in sod. Both above- and below-ground phytomass of blue grama and western wheatgrass were reduced by competition. Plant height in fallow was about twice that in sod. Both survival and vigor of blue grama seedlings were reduced with increasing levels of western wheatgrass competition. For successful establishment of blue grams in an existing sward, artificial or natural openings must be created.

Runoff prediction is an important component of any process-based soil erosion model. In this paper we evaluate the runoff prediction capabilities of a new soil erosion model, WEPP, on sagebrush rangelands. Particular attention was given to the parameter estimation techniques used in WEPP to predict infiltration. Runoff volume predicted by WEPP is based on the Green and Ampt infiltration equation. Predicted runoff was compared to observed runoff from 90 large plot rainfall simulation experiments on sagebrush rangelands. There was a poor correlation between predicted and observed runoff when the Green and Ampt parameters were estimated using the parameter estimation techniques. Runoff prediction was improved when parameters were determined from field measurements. Additional refinement of the Green and Ampt parameterization techniques is needed for continued improvement of WEPP.

In 1989 a mixture of clover (Trifolium hybridum L. and T. repens L.) seed pre-inoculated with Rhizobia by 2 commercial techniques (GuardcoatTM(1) and DormalTM(1)) were compared to bare seed. The Guardcoat produced nodulation on 30% of the clover plants. Dormal and bare seed produced no nodules. Fifty-nine percent of the N in clover top growth in 1990 was derived from atmospheric nitrogen. Use of a pre-inoculated treatment, such as Guardcoat, is an effective method of delivering Rhizobia to aerially seeded clover.

Effects of burning, mowing, and 2,4-D on antelope bitterbrush (Purshia tridentata Pursh.) nutrient contents were evaluated in southcentral Wyoming. During the first growing season following treatments, spraying of 2,4-D increased bitterbrush nitrogen (N) contents from 1.5 to 1.9%, phosphorus (P) from 0.12 to 0.15%, and in vitro digestible dry matter (IVDDM) from 44.1 to 48.4%. Mowing increased N from 1.5 to 1.7%, P from 0.12 to 0.16%, and IVDDM from 44.1 to 46.1%. Burning increased N from 1.4 to 1.9%, P from 0.11 to 0.17%, ash from 3.7 to 5.3%, and IVDDM from 47.4 to 51.0%, and decreased gross energy from 4,640 to 4,380 kcal/g. There were no differences in N and IVDDM contents among treatments at the end of the second growing season, but P content was still greater in mowed bitterbrush regrowth than on untreated bitterbrush. Ash contents were not affected by treatments, but were higher in summer (3.9%) than in winter (2.4%). Gross energy contents varied only 5 to 10% among all treatments and seasons. Correlation coefficients between N, P, ash, and IVDDM contents varied from +0.54 to +0.76, and all of these nutrients were negatively correlated with gross energy. Bitterbrush nutrient contents can be increased by shrub management practices, but short-term responses require that small portions of the total area be treated annually in a rotational shrub management program.

Fire-scorched crowns of live eastern redcedar (Juniperus virginiana L.) were ignited using a propane torch in 3 studies to quantify the efficacy and to determine the feasibility of the technique as a follow-up treatment for killing trees that survived prescribed burns. In the first study, we ignited 98 fire-scorched, live trees 20 to 64 days following a prescribed burn. Igniting scorched trees in several positions killed 90% of the crown and two-thirds of the trees regardless of tree size. Logistic regression models indicated reburning was more effective on trees highly damaged after prescribed burning. In the second study, one person equipped with a self-contained backpack propane burner used single-point ignition to treat in average of 1 tree every 17 seconds (range 11 to 20 seconds) on 0.25-ha plots. Effectiveness of the single-point ignition declined with increasing tree size. In the third study, the average time required to burn a tree was 19 seconds in eight 32-ha pastures. Cost in this field-scale study for labor, propane, fuel, and equipment depreciation was 0.03/ignited tree.

Cattle grazing has been suggested as a principal cause for poor oak recruitment in California's hardwood rangelands. This study evaluated the effects of stock density and season of grazing on blue oak (Quercus douglasii H. & A.) establishment. In December 1989, seven hundred and twenty blue oak seedlings were planted on 3-m centers in 30 plots in 3 annual grassland pastures at the Sierra Foothill Research and Extension Center east of Marysville, Calif. The treatments consisted of 3 seasons X 3 stock densities plus 1 nongrazed control. During January, April, and July of 1990, steers and heifers (mean = 318 kg) were allowed to graze 1 plot per week at low, medium, and high stock densities (2.5, 7.5, and 15.0 head/ha, respectively). Control plots were used to monitor wildlife browsing. One half of all seedling sites received an application of glyphosate prior to transplanting to eliminate grass competition. Browsing and trampling damage were estimated at the end of each treatment. Total damage (sum of browsing and trampling damage), browsing damage, trampling damage, and survival to April 1991 were significantly different for the 9 season and stock density treatments (P < 0.05). Spring and summer grazing tended to be most damaging and resulted in the lowest survival rates. Within each season total damage increased with stock density but survival did not change significantly. Weed control around oak seedlings had no apparent effect on total damage or survival. There were significant differences in browsing damage between seasons but not between control and grazed plots within seasons (P < 0.05). Survival in ungrazed plots was not significantly different (P < 0.05) from the spring and summer grazed plots. Consequently, the contribution of wildlife to reduced blue oak seedling survival in grazed oak woodlands should not be underestimated.

New techniques in molecular biology can be used to characterize genes whose expression is induced by drought stress. These techniques can be used to understand responses of range plants to environmental stresses at the biochemical and molecular level. For example, they can be used to characterize genes that respond to drought stress conditions in the native shrub Atriplex canescens (Pursh.) Nutt. Complementary DNA (cDNA) libraries constructed from drought-induced messenger RNA (poly A+ RNA) were used to characterize genes which are associated with the stress response. A cDNA library from A. canescens was prepared. This library from stressed shrubs was differentially screened with radiolabeled cDNA probes from stressed and nonstressed shrubs, and apparent drought-induced clones were identified. This is the first report of molecular characterization of drought responsive genes in four-wing saltbush. The identification of genes specific to responses to drought stress could provide a basis for understanding drought tolerance in this important range species.

Information is presented on the suitability of various drills for direct seeding into permanent pastures and rangelands in Saskatchewan. Strips of sod 30 to 100-cm wide were killed during the growing season by glyphosate (N-[phosphonomethyl] glycine) in grazing lands at several sites in Saskatchewan. Six drills: 1 with a powered disk furrow opener, 2 with hoe openers, and 3 with rolling disk openers were used to seed measured amounts of alfalfa (Medicago sativa L.) seed in the killed strips in late fall of the same year or early the subsequent spring. Drill performance was assessed during the seeding operation, and emerged seedlings were counted early the following growing season. Seedling emergence ranged from near 0 to 48% of seed sown. Soil moisture conditions in early spring, which in turn were a function of winter precipitation, were a major limitation on seed germination. All of the furrow-opening mechanisms were capable of placing seed at a suitable depth for successful establishment in some situations. The best seedling emergence was obtained with drills having each opener suspended independently with sufficient weight to penetrate dead thatch and hard ground, and with mechanisms to control seeding depth and pack the soil around the seeds.