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Presence of invading annual bromes (Bromus spp.) can alter seasonal patterns of forage production and quality and require management changes for efficient use of infested rangelands in the Northern Great Plains. We studied biological impacts of the presence of brome by comparing brome infested rangeland to similar sites in which brome had been suppressed with autumn applications 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 cross-bred steers (Bos taurus) from mid-May to mid-September 1993 and 1995 and to mid-August 1994. The forage base varied temporally by date and year, but generally was not less than 800 kg ha(-1). Brome suppression increased (P less than or equal to 0.05) crude protein concentration for western wheatgrass (Pascopyrum smithii Rydb. [Love]) in July (7.1 vs. 9.1%) and August (6.0 vs. 7.1%). With the variation in annual brome stands among years, as influenced by growing conditions, this experiment demonstrated that improvement in forage nutritional quality can be expected from suppression of annual bromes on semiarid rangelands. DOI:10.2458/azu_jrm_v54i6_haferkamp

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. DOI:10.2458/azu_jrm_v54i6_haferkamp2

Idaho fescue (Festuca idahoensis Elmer), a palatable native perennial bunchgrass, has persisted on degraded sagebrush-steppe despite invasion by alien plants, excessive livestock grazing, and increased density of woody vegetation due to fire suppression. Survival of these populations in the presence of competitive alien plants suggested 2 possibilities: 1) that Idaho fescue produces seedlings that successfully compete for soil resources with alien invaders, and 2) that Idaho fescue seedlings tolerate stress caused by resource uptake by alien neighbors. We compared germination and growth of Idaho fescue from an undisturbed population with that of conspecific populations from disturbed (grazed and invaded) sites to determine whether disturbed-site seedlings had greater potential for resource capture. Recruitment in Idaho fescue from degraded sites did not appear to be aided by rapid seed germination or greater tolerance of moisture stress during germination. A greater proportion of seeds from the undisturbed site germinated; they germinated faster, and were no more sensitive to water stress, than were seeds from disturbed sites. For both groups, decreasing water potential from 0 to -0.5 MPa had little effect on germination percentages but declined at -1 Mpa. Germination rates slowed with decreasing water potential. Though Idaho fescue from undisturbed and disturbed sites extended roots down the soil profile with equal speed, seedlings from the undisturbed site produced 3.5 times more root length, had 2.7 times greater root length density, and 3.4 times more leaf area than disturbed-site Idaho fescue. The higher growth rate and greater root length density in Idaho fescue from the undisturbed site translates to greater exploration and exploitation of the environment. The 2 Idaho fescue groups had equivalent specific root length, specific leaf area, and root weight ratio. Idaho fescue from disturbed sites showed strong, positive geotropic growth whereas branching and diageotropic growth were greater in Idaho fescue from the undisturbed site. Cheatgrass (Bromus tectorum L.) extended roots faster than did Idaho fescue, with 17 times the root length, 6 times the root length density, and 10.8 times the leaf area of undisturbed-site Idaho fescue. Cheatgrass and Idaho fescue had equivalent specific leaf area, but specific root length of Idaho fescue was nearly twice that of the alien. Roots accounted for about 31% and 55% of cheatgrass biomass. Competitive ability did not appear to promote recruitment in Idaho fescue populations on degraded rangelands. Idaho fescue seedlings from the undisturbed-site were better competitors than disturbed-site seedlings, but interference from neighboring cheatgrass most strongly inhibited shoot growth of both Idaho fescue and cheatgrass. Idaho fescue had little effect on cheatgrass shoot growth. Selection of stress-tolerant genotypes from original populations may best explain the continued existence of Idaho fescue on grazed and invaded sites. We suggest that tolerance of moisture stress combined with vegetative longevity, are mechanisms behind Idaho fescue's persistence.

Japanese brome (Bromus japonicus Thunb.) and downy brome (Bromus tectorum L.), introduced annuals, have invaded many northern mixed-prairie plant communities. This study determined the effect of removing Japanese brome and clipping western wheatgrass [Pascopyrum smithii Rydb. (Love)] on aboveground forage production of a western wheatgrass dominated northern mixed-prairie community. During early spring 1993, a wet year, and 1995, a drier year, western wheatgrass tillers were clipped to ground level in May or June and Japanese brome seedlings were left undisturbed or removed in circular, 1-m2 plots on a clay-pan field site. Western wheatgrass standing crop and tiller densities were estimated by clipping and counting in May and June, and these plus community standing crops were estimated in all plots after Japanese brome matured in mid July. Year effects were significant for standing crop and tiller density due to annual variation in amount and distribution of fall, spring, and early summer precipitation. Conditions were most favorable for tiller initiation of western wheatgrass and germination of annual brome seed in fall 1994 and for herbage production in 1993. Clipping western wheatgrass tillers reduced accumulated standing crop 230 to 350 kg ha-1 and reduced tiller weight by 17 to 58%. Standing crop of western wheatgrass was increased 102 kg ha-1 with removal of Japanese brome, while total standing crop was reduced 284 kg ha-1 with brome removal. Increased standing crop of western wheatgrass appeared to result from increased tiller density rather than increased tiller weight. Removal of Japanese brome from northern mixed prairie plant communities may increase production of associated perennial grasses, but managers should also expect a short-term decrease in total standing crop.

Patterns of bison (Bison bison L.) grazing were examined in a 2-year study on a tallgrass prairie site in Oklahoma subjected to a seasonally and spatially variable burning regime. Mixed groups of bison, composed of cows, yearlings, calves, and young ( 5 years of age selected unburned areas for grazing 29% of the time and burned areas only 4% of the time. Temporal patterns in bison grazing were evident; selective use of burns persisted for only a short period during the first post-fire growing season, after which burns were grazed in proportion to availability and then selectively avoided as bison shifted grazing efforts to newer burns. Regression analysis verified that bison grazing was negatively related to burn age. Regression also showed that grazing patterns were positively related to burn patch size. Although burn types varied significantly in biomass and overall vegetative composition, bison exhibited only limited preference for any burn type, choosing those with higher relative cover of annual Bromus spp. and sedges. It appears that bison select recently burned areas with relatively low graminoid biomass for grazing, presumably choosing these areas based on forage quality rather than quantity.

Leafy spurge (Euphorbia esula L), an aggressive Eurasian forb, is invading native upland ranges dominated by bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Love) and Idaho fescue (Festuca idahoensis Elmer) in the Northern Rocky Mountain Province. Our objective was to determine cumulative effects of 3 summers (1992-1994) of repeated sheep grazing on a leafy spurge infested-Idaho fescue community. Targhee ewes were systematically rotated through paddocks in small pastures. Leafy spurge stem and Idaho fescue and bluebunch wheatgrass plant densities, and frequencies of other species were determined before grazing in 1992, 1993 and 1994, and in 1995, 9 months after grazing ended. Number of viable leafy spurge seeds in seedbanks was determined in 1992 and 1995. Plant heights were measured each year. Density of leafy spurge seedlings was low in grazed and ungrazed areas in 1992 and 1994, whereas density was higher in ungrazed than grazed areas in 1993 and 1995. Grazing did not increase or decrease density of mature leafy spurge stems from 1992 to 1995. Grazing increased density of Idaho fescue but reduced density of bluebunch wheatgrass. Kentucky bluegrass, (Poa pratensis L.), Sandberg bluegrass (Poa sandbergii Vasey), annual bromegrasses (Bromus spp.), and sedge (Carex spp.) frequencies increased in grazed areas. Number of viable leafy spurge seeds in the seedbank was lower in 1995 than in 1992; this reduction was greater in grazed than ungrazed areas. Three years of repeated sheep grazing reduced numbers of leafy spurge seed in the seedbank and seedling densities, but had no effect on density of mature leafy spurge stems. There was minimal effect on the cool season native grasses, possibly because the site was grazed primarily in midsummer when these grasses are dormant. Thus, a long-term commitment to repeated sheep grazing may help to control leafy spurge, although grazed sites should be monitored regularly to ensure that other undesirable species do not increase at the expense of the native plant community.

Seasonal changes in the botanical composition of diets and protein quality of forages consumed by cottontail rabbits (Sylvilagus floridanus) were monitored on disturbed and undisturbed upland hardwood forest-tallgrass prairies in central Oklahoma. Our primary objective was to evaluate the seasonal dynamics of levels of selected amino acid nutrients in forages required for maintenance, growth, or reproduction, and explore bow these changes respond to habitat disturbance resulting from the use of herbicides and fire. Microhistological analyses of stomach digesta indiccated that summer diets were dominated by Panicum oligosanthes Schultes, Croton spp. and Sporobolus asper (Michx.) Kunth; winter diets were dominated by Bromus spp., P. oligosanthes, and Antennaria spp. Differences in the botanical composition and quality of diets between disturbed and undisturbed habitats were of little biological significance. Changes in the concentration of essential amino acids due to plant maturity were minimal in both summer and winter. Estimated levels of nitrogen and essential amino acids in reconstructed diets (based on food habits) appeared to be low, especially for the sulfur-containing amino acids (methionine + cystine) in summer.

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.

We used a cubic sampling quadrat to study the 3-dimensional structure of volunteer Bromus-Poa swards, and explored the relationship of bite depth and sward height as a determinant of bite sizes of wapiti (Cervus elaphus) in the mixed-wood parklands of central Alberta, Canada. The vertical biomass distribution of the sward was pyramidal with leaves dominating the top stratum. Bite depths of yearling and adult wapiti were not significantly different but both were influenced by sward height and season. Wapiti selected bites in both vertical and horizontal dimensions. In spring, wapiti selected vertically, taking green leaves in the top layer of the sward. They selected forbs horizontally in summer and selected leaves vertically in mature autumn swards. Based on the relationships among bite depth and sward height, biomass and sward height, as well as vertical biomass distribution, we calculated expected bite sizes of wapiti on seasonal pasture. We also predicted changes of dietary protein and neutral detergent fiber with increasing bite depth. On spring swards, calculated dietary protein decreased and fiber increased as animals grazed deeper into the swards. In summer and autumn, dietary protein peaked as wapiti cropped about half of the height of the sward whereas dietary fiber was relatively constant. Wapiti adjusted their bite depth to select forage containing at least 14% protein in spring, summer, and autumn. The sacrifice of bite size in tall summer and autumn swards was compensated by diet quality.

Tallgrass prairies are an important forage resource in the eastern Central Great Plains. The effect of spring burning, fertilization, and atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] on standing crop of selected herbaceous species and categories of vegetation was determined in 6 tallgrass prairie environments located near Lincoln and Virginia, Neb., from 1987 through 1989 and 1 site near Bloomfield, Neb., in 1987. The grasslands were in good to excellent condition at the time these studies were conducted. Portions of each site were burned in mid-to late spring, atrazine was applied at a rate of 2.2 kg a.i. ha-1 in late April to early May, and fertilizer was applied in mid-May. Despite below-normal precipitation at 6 of the 7 sites, burning combined with fertilization improved warm-season grass standing crop by 50 to 127% in 5 of the 7 grassland environments studied. This reflected the positive response of the dominant warm-season grasses, big bluestem (Andropogon gerardii Vitman var. gerardii Vitman) and indiangrass [Sorghastrum nutans (L.) Nash], to burning or fertilization. Atrazine increased warm-season grass standing crop at only the site near Bloomfield. Kentucky bluegrass (Poa pratensis L.) and annual bromes (Bromus spp.) were more susceptible to atrazine than smooth brome (Bromus inermis Leyss.). Forb standing crop was significantly reduced by atrazine alone or by burning followed by atrazine application in 4 of the 7 prairie environments. Burning combined with fertilizer application improved warm-season grass standing crop in good to excellent condition grasslands and obviated the need to use atrazine.

Aerial phytomass and litter dynamics of a grassland steppe in Patagonia, Argentina, were studied at either monthly or bimonthly intervals for 2 years. This area is characterized by a cold and wet winter (June to September) and a warm and dry summer (December to March). The growing season extends from September to April, with moist spring and fall periods interrupted by a midsummer drought. Festuca pallescens (St. Yves) Parodi produced about 95% of the total annual phytomass. Peaks of green phytomass were recorded in spring-summer of the first growing season (33.6 +/- 2.9 g . m-2) and in early spring (35.0 +/- 2.4 g . m-2) and fall (32.7 +/- 2.7 g . m-2) of the second growing season. Less abundant forage grasses were Poa ligularis Nees ap Steudel, Bromus setifolius Presl., Hordeum comosum Presl., and Rytidosperma virescens (Desvaux) Nicors. Shrubs and forbs represented less than 2% of the total annual phytomass of this grassland. The relationships between phytomass production of the main species and some environmental variables are discussed. These results contribute to the knowledge of above-ground phytomass dynamics and forage availability throughout seasons of this grassland in Patagonia, and are part of the data necessary for proper range management planning. This information will permit the designing of appropriate grazing schedules by balancing the number of grazing animals to the forage resources available.

Greenhouse and field experiments were conducted at the High Plains Grasslands Research Station to determine what might cause tetany-prone forage. The soil was analyzed for ammonium acetateextractable cations, cation exchange capacity, and alkaline earth carbonates; and the successive harvests of forage plants were analyzed for magnesium (Mg), calcium (Ca), potassium (K), and nitrogen (N). Forages used in the study included legumes: ‘Lutana’ Cicer milkvetch (Astragalus cicer L.), ‘Remont’ sainfoin (Onobrythis viciofoliu Stop.), ‘Dawson ‘, ‘Vernal’, ‘Team’, and ‘Fremont’ alfalfas (Medicugo sativa L.); and grasses: ‘Latar’ orchardgrass (Ductyhs glomerutu L.), ‘Fawn’ tall fescue (Festuca urundinuceu Schreb), ‘Regar’ bromegrass Bromus biebersteinii Roem & Schult.), ‘Manchar’ smooth bromegrass (Bromus inermis Leyss), ‘Garrison’ creeping foxtail (Alopercurus prutensis L.), ‘Luna’ pubescent wheatgrass [Agropyron trichophorum (Link) Richt.], and ‘Greenar’ intermediate wheatgrass [Agropyron intermedium (Host) Beauv.]. Forage Mg level increased when average soil temperature increased from 16.6 to 22.7” C. Fertilization with 1,134 kg of Mg as MgSOd/ha did not increase forage Mg level. Latar orchardgrass and Fawn tall fescue consistently produced forage containing more than 0.20% Mg, whereas wheatgrass species produced forage with Mg levels as low as 0.11%. All legumes had Ca levels ranging from 1.0 to 2.5%. One field crop of Latar orchardgrass produced forage with a high K accumulation (K/Ca •t Mg ratio of 2.7). Predication of blood-serum Mg from forage nutrient content indicated values from 17 to 31 mg/l in lactating cows.

Abused rangelands dominated by introduced cool-season grasses and warm-season shortgrasses are common over much of the Mixed Prairie. Native decreaser species are primarily warm-season grasses and are present at only insignificant levels on abused rangeland in the Loess Hills of southcentral Nebraska. A single, latespring, prescribed fire was evaluated as a method of improvement. The study area consisted of 3 tracts of plots located on Holdrege silt loam soil (Typic Argiustall) with an average annual precipitation of 550 mm. The vegetation on the tracts was in low range condition, with cooland warm-season components being present in varying proportions on all tracts. In general, the dominant cool-season species were Kentucky bluegrass (Poa pratensis) and annual bromes (Bromus spp.), and the dominant warm-season species were blue grama (Bouteloua gracilis) and buffalograss (Buchloe dactyloides). Burning reduced the basal cover and herbage yields of cool-season species. This favored the warm-season component. The increaser short grasses generally exhibited higher herbage yields and basal cover on burned as compared to unburned plots. These results indicate that a single, late-spring, prescribed burn may have a limited potential as a range improvement practice in the Loess Hills of south central Nebraska. The Loess Hills of Southern Nebraska west of 980 30' west longitude were described by Weaver (1965) as Mixed Prairie. The dominant native vegetation was a mixture of primarily warmseason tall, mid, and shortgrasses. Currently, over one-third of the Loess Hills is classified as native range. Due to mismanagement, approximately 60% of this rangeland (1.6 million ha) is in poor to fair range condition (Bose 1977). Improper grazing management has caused a shift in species composition from the native warmseason plant community to a mixture of warm-season shortgrasses, i.e., blue grama (Bouteloua gracilis)' and buffalograss (Buchloe dactyloides), and undesirable cool-season grasses, i.e., Kentucky bluegrass (Poapratensis), Canada bluegrass (Poa compressa), and annual bromes (Bromus spp.). This species composition shift results in a reduction of the quantity and quality of forage produced during the summer months. There are numerous methods of improving rangeland in low condition, but one of the simplest and least expensive practices is prescribed burning. The ability of prescribed fires to selectively suppress or promote particular species depends primarily upon the date of the fire in relation to the phenology of the particular species. As a general rule, those species actively growing when the area is burned are much more susceptible to injury and death than dormant species or those initiating growth (Anderson et al. 1970). Fire severity, which is closely related to fuel loading, size and distribution of fuel, weather, and moisture content of soil and fuel, is also a major factor affecting fire damage to living plants (Wright and Bailey 1982). A late-spring fire has been a particularly effectve Authors are graduate research assistant and professor (range ecology), Department of Agronomy, University of Nebraska, Lincoln 68583. Mr. Schact is currently graduate teaching assistant, Range Science Department, Utah State University, Logan 84322. Published as Paper Number 7087, Journal Series, Nebraska Agricultural Experiment Station. Manuscript accepted March 25, 1984. 'Nomenclature follows Gould and Shaw 1983. method of controlling Kentucky bluegrass (Hensen 1923, Ehrenreich 1959, and Launchbaugh and Owensby 1978), Canada bluegrass (Curtis and Partch 1950), and Japanese brome (Bromus japonicus) (McMurphy and Anderson 1965). In many mesic areas of the Mixed Prairie, prescribed burning has been used to control cool-season grasses without reducing herbage yields or cover of warm-season grasses (Kirsch and Kruse 1972, Gartner and Thompson 1972), although total herbage yield has been reduced the first year following the burn (Dwyer and Pieper 1967). The primary purpose of this study was to determine the potential of a single late-spring prescribed burn in one part of the Mixed Prairie as a means to shift species composition from low yielding warm-season shortgrasses and introduced cool-season grasses to species more indicative of the native Mixed Prairie vegetation, such as big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), switchgrass (Panicum virgatum), and sideoats grama (Bouteloua curtipendula).

Topsoil from nearby undisturbed areas was stripped and directly laid over regraded overburden to a depth of about 20 cm at Kemmerer, Wyo., and Oak Creek, Colo. Native plant response was determined after two growing seasons with only natural precipitation. Rhizomatous species were the most valuable for establishing the perennial plants. Plant density averaged 4.16 and 1.77 plants/m2 at Kemmerer and Oak Creek sites, respectively, but the density was too low to meet State and Federal revegetation standards without additional seeding. Plants established from fresh-stripped topsoil are a plus in revegetation as opposed to stockpiled topsoil where these plants are lost. Rangeland topsoil contains seed, rhizomes, and other vegetative plant parts of many native species. Beauchamp et al. (1975), who studied Wyoming topsoil as a seed source for reseeding stripmine spoils, concluded that viable seed of desirable species was plectiful in the top 2 inches of soil. However, they indicated that seeding or transplanting of desired species would also be required to meet State reclamation standards. Kn$e and Springfield (1972), working in New Mexico, found that n_atural reproduction from seed of desirable range Authors are horticulturist and botanist, respectively. Department ot AgricultureSclcnce and Education Administration. High Plains Grassland Research StatIon, Cheyenne. Wyoming 82001, This study is a contribution from SEA-AR, U.S. Dep. Agr. in cooperation with the Wyoming Agricultural Experiment Statton, Unlverslty ot Wyommg, Laramle. It was supported in part by the Environmental Protection Agency Interagency Agreement Funds: EPA-IAG-DS-E763. Manuxript received February 8, 1978. 76 plants was subject to high loss by wind, water, animals, or insects, and unfavorable conditions for seedling establishment, thus limiting natural reseeding of disturbed lands. A survey was conducted in fall 1977 at two locations to determine species establishment and plant density on spoils that were topsoiled in 1976 with fresh-stripped topsoil. Study Area Study areas were located at the Kemmerer Coal Co. near Kemmerer, Wyo., and the Pittsburg and Midway Coal Co. near Oak Creek, Cola. Elevation at the Kemmerer site is about 2,3 17 m. The experimental topsoil came from a big sagebrush (Artemisiu rridenrutu) plant community. Major plant species included western wheatgrass (Agropyron smithii), slender wheatgrass (A. truchycuulum), big sagebrush, fourwing saltbush (Art-ip/e_r cunescens), and Indian ricegrass (Oryapsis hymenoides). The average annual precipitation at Kemmerer is 23.52 cm. Topsoil at Kemmerer is a Ustic torriorthent with a clayey, montmorillinitic calcareous, frigid, shallow family and loamy, skeletal mixed calcareous family. The slope is about 15%. At Oak Creek the elevation is about 2,286 m. The topsoil came from a mix-shrub plant community. Major plant species were sasi

Straw and grass-hay mulches at rates of 1,120 and 3,360 kg/ha were applied to the surface after seeding or incorporated into the soil before seeding for 3 consecutive years of planting at Central Plains Experimental Range (CPER) near Nunn, Colorado, and at Colorado Yampa Coal Company mine (CYCC) near Steamboat Springs, Colorado. Averaged across 3 years, the stand ratings of Psathyrostachysjuncea (Fisch.) Neveski, the only species seeded at CPER, were significantly better for the check (no mulch) treatment than for any mulch treatment. At CYCC, average stand ratings were significantly better than the check when 1,120 kg/ha of straw mulch was applied to the surface after seeding. The species that consistently had the best stand ratings at CYCC were Astragalus cicer L.,Bromus biebersteinii Roem and Schult.,B. inermis Leyss., B. marginatus Nees, Elytrigia intermedia (Host) Nevski, E. intermedia subsp. barbulato (Schur) A. Live, Medicagofalcata L., M. sativa L., and Phleum pratense L. No erosion from the plots by either wind or water was observed regardless of mulch treatments.

Herbage production in the California annual grassland has been correlated with seasonal weather, particularly fall and spring rainfall patterns. To further examine the relationship between herbage production and rainfall pattern, 3 soil water regimes (-1, -7, -15 bars) simulating expected rainfall and drought events in annual rangelands were applied in seminatural annual grassland communities. Soft chess (Bromus mollis) tillers grew longest under the -7 bar water regime treatments while total plant growth was greatest under the -1 bar treatment. Tiller length and total growth of slender oat (A vena barbata) were greatest under the -1 bar treatment. Vegetative growth of slender oat was less sensitive to seasonlong soil water regimes than soft chess. The two species required different soil water conditions for maximum spring growth; soft chess put on spring growth most rapidly in the -7 bar treatment while slender oat grew fastest in the -1 bar treatment. Periodic water stress during the growing season did not reduce spring herbage production. Maximum growth and herbage production occurred only when soil water was available after March 15. Withholding water after March 15 reduced herbage production by 46%. Annual range species dominate open grassland and woodland understory on about 10 million hectares in California. Forage production and botanical composition of the forage vary annually because the herbaceous vegetation begins each growing season as seedlings. Researchers have long attributed variation in range productivity to seasonal weather conditions. Talbot and Biswell (1942) concluded that climatic factors were the main cause for yearly fluctuations in forage yield at the San Joaquin Experimental Range in the southern Sierra foothills. Murphy (1970) found a significant correlation between yield and early growing-season rainfall at the Hopland Field Station in northern coastal California, but Duncan and Woodmansee (1975) failed to find any seasonal correlations at the San Joaquin Experimental Range. Pitt and Heady (1978) concluded that warm fall and spring temperatures coupled with adequate fall and spring precipitation at Hopland resulted in the greatest yield, but it is yet to be determined whether such empirical models can explain annual differences in productivity on drier inland annual rangelands such as the San Joaquin Experimental Range. Peak standing crop increases with increasing average annual rainfall along a south-north rainfall gradient of 125 to 2,000 mm per year (Bartolome 1980). Annual rangeland at the Sierra Foothill Range Field Station in the central Sierra foothills produces 2,000 to 2,700 kg/ha/yr if soil water is limiting in April or May and The authors are visiting assistant professor, Department of Agronomy, Oklahoma State University, Stillwater 74078 and associate professor, Department of Agronomy and Range Science, University of California, Davis 95616. The authors thank Dr. H.F. Heady, Dr. J.W. Bartolome, and Dr. L.J. Waldron, College of Natural Resources, University of California, Berkeley, and Dr. W.A. Williams, Department of Agronomy and Range Science, University of California, Davis, for their advice and critique of the manuscript. This research was supported in part by NSF Grant No. DEB 7823641 and the California Agricultural Experiment Station. Manuscript received September 22, 1981. thereafter, but produces 2,800 to 4,600 kg/ha/yr if soil water is available until June or July (Evans et al. 1975). Drought and rainfall pattern are undoubtedly controlling factors for herbage production in California annual grasslands, but mechanistic studies of the responses of annual species to soil water conditions are nearly lacking. In a greenhouse pot study, Gerakis et al. (1975) showed that subterranean clover (Trifolium subterraneum L.) is more drought tolerant than either soft chess (Bromus mollis) or redstem filaree (Erodium botrys). We examined plant growth parameters as they were affected by different soil water regimes designed to simulate winter and spring drought events in California annual grasslands.

A field evaluation study was made on eight pasture grass species, 'Latar' orchardgrass (Dactyl& glomerata L.), 'Fawn' tall fescue (Festuca arundinacea Schreb.), 'Manchar' bromegrass (Bromus inermus Leyss.), 'Regar' bromegrass (B. biebersteinii Roem and Schult.), 'Garrison' creeping foxtail (Afopecurus arundinacea Poir.), 'Meadow' foxtail (A. pratensis L.), 'Luna' pubescent wheatgrass (Agropyron trichophorum (Link) Richt.), and 'Greenar' intermediate wheatgrass (A. intermedium (Host) Beauv.). Three harvests of each species were analyzed for in vitro dry matter digestibility (IVDMD) for 1975,1976, and 1977. Fawn tall fescue and Manchar bromegrass had severely depressed IVDMD values in the second harvest of 1976 and both species and Regar bromegrass had low values for the third harvest of that year. The forages were analyzed for perloline alkaloid by a thin layer chrometography method and the depressed IVDMD values were found in the replicate samples containing perloline. The alkaloid could be toxic to livestock. Methods The eight grass species studied were 'Latar' orchardgrass (Dactylis glomerata L.), 'Fawn' tall fescue (Festuca arundinacea Schreb.), 'Manchar' bromegrass (Bromus inermus Leyss.), 'Regar' bromegrass (B. bierbersteinii Roem and Schult.), 'Garrison'creep- ing foxtail (Alopecurus arundinacea Poir.), 'Meadow' foxtail (A. pratensis L.), 'Luna' pubescent wheatgrass (Agropyron trichophorum (Link) Richt.), and 'Greenar' intermediate wheatgrass (A. intermedium (Host) Beauv.). These irrigated forages were established in the field at Cheyenne, Wyo., in the spring of 1974 as part of a large evaluation trial in 2.4 X 4.8 m plots. Two centimeters of water were applied to the grasses every 3 or 4 days. Each species was replicated twice. Ammonium nitrate was applied to the grasses each year near May 1 and July 1 at the rate of 76 kg N/ha.- Harvests were made each year when the grass was at boot or heading stage on the first crop and when regrowth was 20 to 30 cm tall on succeeding crops. Forage from each plot area was clipped, weighed, and subsampled. The subsample of green forage was placed in a drying oven within 1 hour after harvest and dryed at 65O C to determine dry matter production. The forage IVDMD for each of three harvests per year during 1975 thru 1977 was determined by a modified Tilly and Terry (Tilly and Terry 1963) method. The alkaloid concentration in the 1976 harvests were determined by a thin layer chromatography (TLC) method as follows: A l-gram sample of dried and ground plant material was mixed with 0.3 g of sodium bicarbonate and 2 ml of water in a small beaker. The mixture was stirred with a glass rod for 2 minutes. Ten ml of a CHCh/ MeOH (9: 1) solution was added to the mixture and stirred with a magnetic stirrer for 30 minutes. The mixture was then filtered and the filtrate was evaporated in vacua to a volume of 1 ml. The alkaloids were separated from other plant material by a silica gelTLC. Forty microliter aliquots were spotted and developed with the upper phase of a mixture of butanollacetic acid/water (4: 1:5). An iodoplatinic acid solution, used for visulization of spots, consisted of a mixture of 10 ml of a 5% platinum chloride, 5 ml of cont. HCl, and 240 ml of a 2% KI solution. Results and Discussion Festuca and Bromus species had significantly inhibited IVDM D in the second and third harvests of 1976 compared with other species in the study. While all grass species showed depressed IVDMD values for the first harvest of 1975, this was probably caused by the fiber content of the more mature forage compared with the re-growth of succeeding harvests of that year. During the study, severe inhibition of IVDMD did not occurr in Latar orchardgrass, Garrison creeping foxtail, Meadow foxtail, Luna pubescent wheatgrass, and Greenar intermediate wheatgrass. Therefore, IVDMD values were shown in Table 1 for a

Influences of grazing intensity on species composition and herbage production of grass-woodland and improved grassland subtypes of annual range were evaluated over a 5-year period in coastal northern Califomia using 3 grazing treatments (100, 150, and 200o of moderate stocking). Herbage utilization did not differ signiflcantly between the 2 subtypes but averaged 42, 52, and 69%o for the respective treatments. Plant species and production responses differed significantly between woodland and grassland subtypes. On woodland, ripgut brome (Bromusrigidus Roth.)l and wild oats (A vena barbata Brot. and A. fatua L.) were most sensitive to grazing intensity while wild barley (Hordeum leporinum Link. and H. hystrix Roth.) and annual fescue (Festuca dertonensis (all.) Asch. and Graebn. and F. megalura Nutt.) were least sensitive. On improved grassland, subterranean clover (Trifolium subterraneum L.) increased and soft chess (Bromus mollis L.) decreased with increasing grazing intensity. Soft chess remained most plentiful on woodland range under heaviest grazing and it continued to be a major species under heavy grazing of grassland, demonstrating tolerance to grazing intensity. Filaree (Erodium cicutarium (L.) L'Her. and E. botrys (Cay.) Bertol.) declined on woodland but increased on grassland as grazing intensified. Peak standing crop was not significantly affected by grazing intensity on woodland range but was greatest at 150%o of moderate stocking and lowest at 200% of moderate stocking on grassland range. Decline in grassland herbage yield under heaviest grazing was due to reduction of soft chess which was displaced by subterranean clover. Effects of grazing intensity on range composition and productivity were confounded by innate differences in ranges and yearly weather patterns. Herbage production was impacted more by annual growing conditions than by grazing regimens, but there was no correlation between total annual precipitation and peak standing crop.

Herbage quality of meadow bromegrass [Bromus biebersteinii Roem and Schult.], smooth bromegrass [Bromus inermis Leyss.], intermediate wheatgrass [Agropyron intermedium (Host) Beauv.], Russian wildrye [Elymus junceus Fisch.], crested wheatgrass [Agropyron cristatum (L.) Gaertn.] in mixtures with alfalfa [Medicago sativa L.] or cicer milkvetch [Astragaluscicer L.] and with the 2 legumes in pure stands at 2 dates of harvest (June 5, June 26) and with 4 rates of fertilizer (0 kg N/ha-0 kg P/ha, 0 kg N/ha-22 kg P/ha, 45 kg N/ha-0 kg P/ha, 45 kg N/ha-22 kg P/ha) was studied in western Nebraska in 1977 and 1978. Soil at the study site was a loam (Typic Argiustoll) and average annual precipitation is 386 mm. Alfalfa-grass mixtures maintained a higher percentage crude protein than the respective cicer milkvetch-grass mixtures, with the alfalfa-Russian wildrye mixture producing the highest percentage crude protein. Percentage in vitro dry matter digestibility (IVDMD) of the cicer milkvetch-Russian wildrye mixture was the highest of all mixtures, and the percentage IVDMD of the cicer

From the time of seed maturity in late June and early July until December when temperatures drop to near freezing, habitat temperatures are within the range of those required for germination of seeds of the winter annual Bromus juponicus. However, a large proportion of the seeds in a given seed crop fail to germinate in the autumn of the year in which they are produced because they are not dispersed until winter. A high percentage of of the winterdispersed seeds is induced into dormancy and must undergo a period of afterripening the following summer before germination can occur the next autumn. Thus, many of the plants that become established at a population site in autumn are from the previous year’s seed crop. Plants overwinter in the field as “rosettes” and require long days for flowering. Nonvernalized plants exposed to natural short photoperiods of late autumn and winter flower under long days in spring, but plants flower much sooner if they are subjected to both low temperatures (vernalization) and short photoperiods during winter. Bromus japonicus Thunb. (Japanese chess) is a native Eurasian winter annual that has been introduced into the United States where it ranges from Vermont to the state of Washington south to North Carolina and California (Hitchcock 1935, Fernald 1950). As is true for some other introduced bromegrasses in the United States, B. japonicus is a problem in wheat fields, in grass and alfalfa seed fields, and in pastures, meadows, and overgrazed range lands (Slife et al. 1960, Finnerty and Klingman 1962, Steyermark 1963). To better understand the ecological life cycle of this weedy winter annual, we have studied (1) the role of temperature in controlling the timing of germination in nature and (2) the influence of vernalization and photoperiod on the timing of flowering. In northcentral Kentucky where we have observed its phenology, B. japonicus begins to flower in early May, and caryopses (hereafter referred to as seeds) are ripe by late June or early July. Plants senesce as the seeds mature, and there are no living plants at a population site during summer. The seeds are retained on the dead erect shoots until autumn and winter. Seed dispersal begins in early October, and continues until the following March, with a high percentage of the seeds being dispersed during November, December, and January. Seed germination occurs in early autumn, and thousands of seedlings may appear at a population site at any time from early September to mid October, depending upon the time when soil moisture conditions become suitable for germination. Only an occasional seedling is found in the field in spring. Since germination occurs before very many of the seeds are shed, population establishment each year results primarily from germination of a reserve of seeds present in and/or on the soil surface. Following germination, each plant produces a “rosette” of 10-l 5

Proc. 2nd Tall Timbers Fire Ecol. TUELLER, P. T., AND R. A. EVANS. 1969. Conf., Tallahassee, Fl. p. 117-126. Control of green rabbitbrush and STODDART, L. A. 1941. The palouse big sagebrush with 2,4-D and picgrassland association in northern loram. Weed Sci. 17:233-235. Utah. Ecology 22: 158-163. WARG, S. A. 1938. ’ Life history and TISDALE, E. W., M. HIRONAKA, AND M. economic studies on Bromus tecA. FOSBERG. 1965. An area of pristorum. Unpub. M.S. Thesis, Univ. tine vegetation in Craters of the Montana, Missoula, Mon. 38 p. As Moon National Monument Idaho. cited in J. 0. Klemmedson and J. G. Ecology 46:349-352. Smith. 1964.