There has been increasing concern that training on military lands results in excessive soil erosion, ecosystem degradation, and loss of sustainable training resources. Vegetation structure has been shown to play a role in soil surface stabilization by reducing shear stress caused by wind force. A study at the Idaho Army National Guard training facility at Orchard Training Area (OTA), Ida. assessed the effect of simulated M1A2 Abrams battletank maneuvers on grassland plant canopies and soil erodibility. The point-intercept method was used to estimate vertical vegetation structure before and after tracking. A portable wind tunnel was used to measure threshold wind speeds (TWS) associated with different numbers of tank passes and soil mass removed by wind. Results indicated that significant damage occurred to vertical vegetation structure as the number of passes increased. Threshold wind speed, an indicator of soil surface stability, significantly decreased with tracking and eroded soil mass significantly increased. Positive correlations existed between vegetation parameters and threshold wind speed. Soil loss was negatively correlated with vegetation parameters. Results indicated that the decrease of vertical vegetation structure led to a decrease in threshold wind speed. This decrease in threshold wind speed was the result of reduced soil surface protection by vegetation. Decreased surface protection also resulted in increased soil loss. Results from this work confirmed that vegetation plays a major role in reducing shear stress on the soil surface. Predictions for soil loss at Orchard Training Area resulting from the number of M1A2 passes are made using linear models. A critical tracking threshold of 4 passes was estimated based upon model output and average local wind speeds for Orchard Training Area.

Previous research suggested that big sagebrush (Artemisia tridentata Nutt.) recruitment occurs in pulses consistent with favorable climatic conditions. In 1997, 75 stem sections were collected from 9 stands of each of the 3 subspecies of big sagebrush in Wyoming along elevation and climatic gradients. Annual growth rings were used to identify the year plants were established. Large cohorts of Wyoming big sagebrush (A. tridentata ssp. wyomingensis Beetle and Young) appeared in 1982, 1981, 1964, 1961, and 1955. Basin big sagebrush (A. tridentata ssp. tridentata Beetle and Johnson) cohorts flourished in 1991, 1986, 1985, 1982, and 1977. Mountain big sagebrush (A. tridentata ssp. vaseyana [Rydb.] Beetle) cohorts prospered in 1985, 1982, 1981, 1979, and 1974. Mean monthly precipitation and temperature records were compared to years with high and low recruitment using logistic regression models at 3 geographic scales (single-stand, regional, statewide). Wyoming big sagebrush recruitment was greatest in years with above-average December and January precipitation occurring after the first growing season (r2 = 0.10, 0.04, P < 0.05). Basin big sagebrush recruitment was most successful in years with above-average March, May, and June precipitation during the first growing season (r2 = 0.06, 0.09, 0.18, P < 0.05). Mountain big sagebrush recruitment was greatest in years with below-average February, April, and May precipitation after the first growing season (r2 = 0.03, 0.04, 0.04, P < 0.05). While variable precipitation patterns appear to contribute significantly to recruitment of big sagebrush, responses among the 3 major subspecies were quite variable. More complex models need to be developed to foster our understanding of the mechanisms affecting big sagebrush establishment.

Sand shinnery oak (Quercus havardii Rydb.) communities are shrublands extending from northern Texas and western Oklahoma southward into the Chihuahuan Desert. They are dominated by sand shinnery oak, a member of the white oak group. Structure and composition of sand shinnery oak communities in relation to natural disturbances, such as fire, have not been adequately investigated. The objectives of this study were to determine the influence of fire on shrub composition and vegetation structure of sand shinnery oak communities, and to determine the persistence of structural and compositional changes. Data were collected on Black Kettle National Grassland (BKNG) in western Oklahoma during the growing seasons of 1998 and 1999. Vegetation measurements included line transects, visual obstructions, heights, cone of vulnerabilities, shrub patch sizes, and shrub patch densities were used to estimate functional group canopy cover, shrub composition, and structure of sand shinnery oak communities. One growing season after fire, burned sand shinnery oak communities had significantly less shrub cover (P < 0.01) than unburned communities (38 vs. 51%). Height of vegetation was lower 1 and 2 growing seasons after fire (26 and 35 cm, respectively) (P < 0.05) than unburned communities (44 cm). Visual obstruction was lower the first (30%) and second (40%) year after fire (P < 0.01) compared to unburned communities (59%). Cone of vulnerability indicated significantly more open structure one growing season after fire. After 4 growing seasons, all measures of structure in burned communities were similar to those in unburned communities. We found no differences in composition of shrub species between burned and unburned sites (P = 0.55). Two fire events, 2 growing seasons apart, had less influence on vegetation structure than the initial fire. Sand shinnery oak communities appear to be highly resilient to periodic disturbance by fire. Prescribed fire is an effective tool for short-term alteration (< 3 growing seasons) of sand shinnery oak structure; however, rapid recovery following fire does not indicate any long-term changes in vegetation structure and composition.

The tribe Triticeae contains over 250 perennial species that are components of grasslands in the temperate and sub-arctic regions of the world and includes some of the world's most valuable forage and rangeland species. Many of these species had not been evaluated previously in the Central Great Plains, USA. A subset of the germplasm of the tribe Triticeae which included over 100 accessions of 55 different species was evaluated in a replicated, space-planted trial in eastern Nebraska during 1994-1996 to determine the survival and forage productivity of the accessions. The evaluated accessions were representative of perennial Triticeae genera and genomes. Perennial grasses of the Triticeae are based on the P, St, H, Ns, E, W, Y genomes and an unknown Xm genome(s). Triticeae that survived and had acceptable forage yields during the period of the trial were the Agropyron's-crested wheatgrasses (PP and PPPP genomes), Psathyrostachys-Russian wildryes (NsNs genomes), Thinopyron's-intermediate and tall wheatgrasses (EEEEStSt and EEEEEEStSt genomes), some Elymus (StStHH genomes), several Leymus (NsNsXmXm genomes), and Pascopyrum-western wheatgrass (StStHHNsNsXmXm genomes). Several Leymus species had not been evaluated previously in this region but showed considerable potential and merit additional evaluation, including L. chinensis, L. akmolinensi, L. racemosus, L. sabulosus, and L. secalinus. Species with only the H genome (Hordeum) and St genome (Pseudoroegneria) were not adapted to the region because of poor survival or low productivity. The study provides an example of how the rapidly emerging field of genomics can have practical applications to grasslands and rangelands.

Presence of annual bromes (Bromus spp.), introduced annual weedy grasses, can alter seasonal patterns of forage production and quality and require management changes for efficient use of infested rangelands. We determined biological impacts of the presence of brome by comparing livestock performance on brome infested rangeland to similar sites on which brome had been suppressed by autumn application of atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)- 1,3,5-triazine-2,4-diamine] at 0.56 kg ha(-1) in 1992 and 1993. Each treatment was randomly assigned to three, 12-ha pastures. Vegetation was measured for 5 months (May to September) each year from 1993 to 1995. Each pasture was stocked with 8 crossbred steers of British breed origin (Bos taurus) from mid-May to mid-September 1993 and 1995 and to mid-August 1994. Initial body weights averaged 329 kg SD = 31 in 1993, 273 kg SD = 14 in 1994, and 272 kg SD = 21 in 1995. Brome suppression and environment influenced plant species in diets, diet quality, and livestock performance. Brome suppression reduced percentage of annual grasses in diets from 14% to 10%. Annual grasses were replaced in the diet by a variety of forb and grass species [western wheatgrass [Pascopyrum smithii Rydb. (Love)], and blue grama [Bouteloua gracilis [H.B.K.] Lag. ex Griffiths]], with specific replacement depending on year and month. Steer gains were increased from 0.92 to 1.04 +/- 0.02 kg head(-1) day(-1) (P < 0.02) and from 69 to 81 +/- 2.8 kg ha(-1) (P < 0.05) with brome suppression. This experiment demonstrated that improvement in livestock performance can be expected with the suppression of annual bromes on semiarid rangelands.

Simple, reliable tools are needed by land managers to quantify establishment success when seeding or re-seeding pastures or rangeland. A frequency grid was designed to measure seedling or plant establishment success for a single species, mixtures of species, or single species of a mixture. The frequency grid is a metal frame containing 25 squares (5 x 5) or cells and can be made from concrete reinforcing sheets that have 15 x 15 cm squares. When used, the frequency grid is either randomly or systematically placed within a seeded area. The number of cells containing 1 or more seeded plants are counted. The grid is then flipped, end-over-end, and the counts are repeated. The process is repeated until a total of 100 cells have been counted per sampling location within a seeded area. Counts can be directly converted into frequency of occurrence or stand percentages by dividing the number of cells that contain a seeded plant by 100. The process can be repeated at several locations within a seeded area to characterize establishment success. Multiplying frequency of occurrence percentages by 0.4 provides a conservative estimate of plant density (plants m(-2)). A single measurement of 100 frequency grid cells can be taken in less than 5 minutes. The frequency grid is inexpensive to make, requires minimal training, permits rapid measurements, and provides a meaningful estimate of plant density. The frequency grid has been used to document herbicide efficacy and seeding rates for use in grassland establishment in the central Great Plains and should be easily adaptable for use in other geographic regions.

Land, livestock, and wildlife managers need to understand the nutritional dynamics of forages to sustain adequate growth and reproduction of their animals and/or assure equitable payment for forages. Despite a long history of livestock grazing in the northern Great Basin, seasonal and annual nutritional dynamics of many of the region's prominent grasses have not been described. We addressed this issue via monthly sampling of 7 cool-season grasses at 6 sites during 1992, a drier than average year having 86% of mean precipitation, and 1993, when above average precipitation (167% of average) occurred. With high yields predicted in 1993 (1,257 kg ha(-1)), the period of adequate forage quality [crude protein (CP) greater than or equal to 7.5%] was 83 days. In addition grasses did not respond to 97 mm of July-August rain with renewed growth. During 1992, a growing season beginning with less than average moisture, grasses responded to midsummer (49 mm) and fall (69 mm) rains by maintaining greater than 7.5% CP for 185 days. A diversity of grasses expanded the period of adequate forage quality especially during the lower than average moisture year. Giant wildrye (Elymus cinereus Scribn. Merr.), a deeply rooted grass, supported high quality forage until mid August, but did not respond to late-season moisture. In contrast, shallow rooted grasses like bottlebrush squirreltail (Sitanion hystrix (Nutt.) Smith), Sandberg's bluegrass (Poa sandbergii Vasey), and the winter-annual cheatgrass (Bromus tectorum L.) responded to summer or fall moisture with herbage ranging from 10 to 16% CP, thereby supplying high quality late-season forage. With most precipitation occurring in the northern Great Basin during colder months, livestock or habitat managers can, with a fair degree of certainty, predict yields from their pastures before turnout. With abundant moisture, managers will see the rapid deterioration of forage quality that occurs when grasses advance through their reproductive stages of phenology and generate a wealth of reproductive stems. The quandary arrives, however, when moisture accumulations are less than optimum. Fewer reproductive tillers develop, and our results show that timely precipitation may elevate desirable nutrient characteristics and expand the duration of adequate livestock/wildlife nutrition in the region. More long-term research is needed to decipher the mechanisms governing growth and development of rangeland grasses and to assess risks of various stocking alternatives when managers face uncertain yield and forage quality issues.