Siberian wheatgrass [Agropyron fragile (Roth) Candargy] is known for its establishment and persistence on sandy soils under severe water limitations. Morphology, cytology, and forage and seed characteristics were studied on 59 accessions (JA) of Siberian wheatgrass collected on sandy soils in the desert areas of western Kazakhstan. Plants were grown at Nephi, Ut., from 1993 to 1996 and compared with the check cultivars of Vavilov and P-27 Siberian wheatgrass, and Nordan crested wheatgrass [A .desertorum (Fisch. ex Link) Schultes]. All JA-accessions were autotetraploids, 2n= 4x= 28. The most frequently observed meiotic association was 6 bivalents + 4 quadrivalents. The JA-accessions were morphologically diverse, ranging from short to tall in stature and from dark-green, glaucous to blue-green, strongly pubescent. Mean forage yield, crude protein, and dry matter digestibility were generally lower in the JA-accessions than the check varieties. Entry x year interactions were nonsignificant (P> 0.05) for all measured forage variables. Entries were significantly (P < 0.01) different for dry matter production. Seed weight of Vavilov and mean seed weight of JA-accessions were significantly (P < 0.01) greater than that for the check cultivars P-27 and Nordan. Entries that were highly pubescent had the heaviest seed and greatest capacity to emerge from a 7.6-cm planting depth. Seed yield plant -1 was significantly (P < 0.01) lower in the JA-accessions than cultivars Vavilov, P-27, and Nordan. Sufficient variations exist for seed yield, seed weight, seedling vigor, and forage yield within the JA-accessions to allow for the development of an agronomically suitable, drought tolerant Siberian wheatgrass through selection.

Western ragweed [Ambrosia psilostachya DC. ], a major forb species in mixed and tallgrass prairies, is considered to have little value for cattle grazing but is an important food item for bobwhite quail [Colinus virginianus]. While often thought to be a strong increaser with grazing pressure, information on the actual relationship between western ragweed and grasses is contradictory. Our objectives were to 1) determine the effect of western ragweed on grass standing crop, and 2) determine the effect of vegetation type and grazing on survival and shoot morphology of western ragweed. Western ragweed did not appear to reduce grass standing crop. Instead, standing crop (40 to 620 kg ha-1) and density (6 to 41 shoots m-2) of western ragweed were positively related to grass and grass-forb standing crop in mixed prairie. Standing crop of western ragweed was not related to grass standing crop in tallgrass prairie. Competitive thresholds for western ragweed in mixed and tallgrass prairies appear to be above the levels observed in this study. Density of western ragweed shoots decreased over the growing season under both grazed and ungrazed treatments. Survival of western ragweed shoots from June to September was greater in mixed prairie (81%) than in tallgrass prairie (63%) and was greater in ungrazed (76%) than grazed plots (68%). Western ragweed shoots weighed less per unit of height in tall grassprairie. Western ragweed shoots in ungrazed plots were taller than shoots in grazed plots but weighed less per unit of height. These differences in shoot morphology are consistent with increased competition for light in tallgrass prairie and in ungrazed sites. Western ragweed may not directly reduce grass standing crop but, rather, increase only when grasses are reduced by other stresses such as improper grazing.

Spatial patterns of herbivore defecation within grazing systems are important as they directly affect pasture growth and composition. These effects are partially linked to seed dispersal in dung, a little studied process. This paper focuses on: (i) quantification of dung and seeds deposited by herbivores in a Mediterranean grazing system, and (ii) analysis of the spatial variability of dung and seeds deposited within and among plant communities. We carried out year-long monthly quantifications of the depositions of rabbit (Oryctolagus cuniculus), fallow deer (Dama dama), red deer (Cervus elaphus), and cow (Bos taurus) dung to 32 plots distributed in Quercus rotundifolia Lam. and Fraxinus angustifolia Vahl woodlands, mixed scrub, and Cistus ladanifer L. scrub. We also quantified the germinable seed content of dung. The results revealed differences (p < 0.05) in dung deposition, varying (I) among the 4 species, (ii) within species (except for the red deer) among plant communities, and (iii) within plant communities. An average of 735 seeds/m2 were returned to the soil via dung, with the highest numbers in open woodlands (870–1,888 seeds/m2) and the lowest numbers in scrubs (83–315 seeds/m2). Cows dispersed the most seeds (68%), followed by red deer (20%), rabbits (7%), and fallow deer (5%). Spatial variability in deposition led to accumulations of up to several thousand seeds at points covered by the dung. The effect of seed input to the seed bank and on vegetation may be low at large and medium-sized spatial scales, but it can be very important at small scales and for colonization processes.

Spotted knapweed (Centaurea maculosa Lam.) management may be enhanced by integrating strategies that stimulate and maintain competitive grasses. The objective of this study was to determine if picloram, fertilizer, and timing and frequency of grass defoliation could be integrated to minimize spotted knapweed reinvasion. Sixteen chemical treatments [4 picloram rates (0.00, 0.14, 0.28, and 0.42 kg a.i. ha- 1) and 4 fertilizer rates (source: 16-20-0, N-P-K; material: 0.0, 66, 132, 198 kg ha-1)] were applied in the spring of 1994 to 4 by 4 m plots and factorially arranged in a randomized-complete-block design. Within each plot, 6 grass defoliation treatments were randomly applied to 1 by 1 m sub-plots. From 1994 through 1997, 60% of the aboveground grass biomass was hand clipped and removed from the plots during the spring, summer, fall, alternating spring/fall, all 3 seasons. A control received no grass defoliation. The experiment was replicated 4 times at 2 sites dominated by spotted knapweed. At peak standing crop in 1997 spotted knapweed density, grass and spotted knapweed biomass; and percent cover of spotted knapweed, grass, litter, and bare ground were measured. Data were analyzed as a split-plot using analysis of variance. Four years after treatment all rates of picloram reduced spotted knapweed density, biomass, and cover, and increased grass yield. Nitrogen and P fertilizer tended to increase spotted knapweed density and biomass. Nitrogen and P fertilizer plus defoliation in all 3 seasons caused a greater increase in spotted knapweed reinvasion at the site with Kentucky bluegrass (Poa pratensis L.) than the site with timothy (Phleum pratense L.) and smooth brome (Bromus inermis Leys.). Fall-only defoliation and no defoliation appear to deter spotted knapweed reinvasion better than defoliation in all 3 seasons and alternately in the spring and fall.

In Argentina, Paspalum quadrifarium Lam. (paja colorada) forms tall dense grassland communities in the flooding pampas. Referred to locally as “pajonales”, these grasslands generally have very low nutritional value for cattle, except at the post-burn regrowth stage. To improve forage quality and consumption by breeding cattle, Lotus tenuis Walst et Kit. is over seeded immediately after burning of paja colorada pajonales. The objectives of this experiment were to follow the after seeding cover of lotus, evaluate weed control, and assess disease incidence and severity.The experiment was carried out in Azul, Buenos Aires provinceof Argentina, between September 1993 to September 1996. The postburn seedbed was very favorable for lotus germination and establishment. The most effective chemical weed control was obtained with 2,4-DB used alone or in combination with dicamba. Lotus increased markedly the quality of the pasture forage due to its high crude protein content. Four fungus diseases were found: Botrytis cinerea Pers., Stem phylium sp. Wallroth, Uromyces loti Blytt. and Fusarium spp. Link ex Fr. However, these caused only light foliar damage and did not impair lotus germination or establishment. The overseeding of lotus after burning of P. quadrifarium pajonales, is a very effective technique to improve carrying capacity and animal performance.

We evaluated reproduction and recruitment of the Columbia spotted frog (Rana luteiventris Thompson) in 70 ponds used by beef cattle and in 57 ponds not used by beef cattle in northeastern Oregon. No significant differences were detected in the number of egg masses or recently metamorphosed frogs in grazed and ungrazed sites. No pond characteristic measured could predict egg mass numbers, but percent aquatic vegetation and dissolved oxygen had some ability to predict recently metamorphosed frog numbers. Both variables explained 65% of the variability in recently metamorphosed frog numbers in grazed ponds. At ungrazed ponds, 4 additional variables (presence of fish, elevation, percent of rock, and conductivity) were required to achieve the same level of variability in predicting recently transformed frog abundance. The egg mass volume was larger at grazed than at ungrazed ponds suggesting that grazed ponds may have a greater food abundance or larger (older) individuals.

Animals used in grazing trials with small paddocks usually have not been exposed to the experimental site and related research procedures. Grazing trials conducted in May and August 1996 on smooth bromegrass (Bromus inermis Leyss.) quantified forage removal and grazing time of heifers adapted or not adapted to small paddocks. Treatments consisted of adapting heifers for 4 days to small paddocks (0.054 ha) and a control treatment of heifers continuously stocked in larger paddocks (>16 ha). On day 5, each group of heifers was moved to similar small paddocks and forage utilization and cattle grazing times were measured after 4 and 24 hours of grazing. In May, when sward structure was comparable in the large and small paddocks, tiller height reduction, leaf length reduction, herbage bio-mass reduction, and grazing time were similar (P > 0.10) for experienced and inexperienced heifers after 4 and 24 hours of exposure to day-5 paddocks. In August, when sward structure differed between the large and small paddocks, leaf length reduction after 4 hours was greater (P < 0.10) by experienced cattle than inexperienced cattle. Herbage reduction in August by experienced cattle was 435 kg ha-1 greater (P < 0.05) than by inexperienced cattle after 24 hours. Cumulative grazing time was 76 minutes (P < 0.10) greater at 4 hours for the experienced cattle than the inexperienced cattle. Grazing animals appear to adapt immediately to small paddocks but other unfamiliar grazing conditions, e.g., sward structure, may require short adaptation periods for experimental animals.

Because of the relatively low cost of seed and ease of establishment, more than 0.4 million ha of weeping lovegrass (Eragrostis curvula (Shrad.) Nees.) were planted on Conservation Reserve Program (CRP) lands in the Southern High Plains. Dryland cropping alternatives including wheat and grain sorghum, give relatively low and variable economic returns. The objective of this study was to evaluate the economics of the lovegrass grazing alternative. Using a tract of weeping lovegrass in Curry County, N.M., animal performance and the economics of 5 grazing management treatments were evaluated, including 12-month and 6-month continuous grazing, seasonal grazing during only the spring and fall, and a 6-pasture rotation system. Fertilization of the pastures was also evaluated for the spring/fall grazing treatment. Average daily gain (ADG) for yearlings grazing weeping lovegrass pastures was found to decline rapidly as the grazing season progressed. The ADG was over 1.36 kg day-1 in early May but gradually declined over the grazing season to less than 0.45kg day-1 by the end of August. To maximize profit, stocker cattl ewould be sold in early September. All of the grazing systems yielded similar net economic returns, but substantially high ereconomic returns could be made by adjusting stocking rates to market conditions. Returning CRP land to dryland cropping or grazing with stocker cattle was estimated to yield nearly identical economic returns. Neither growing traditional crops or grazing lovegrass pastures appear to be economically viable alternatives without government assistance programs in place.

Wildlife water developments have been constructed and maintained throughout the arid western United States to benefit big game and upland gamebird populations. There is debate, however, over possible detriments to wildlife from artificial water sources in deserts and other arid environments. One concern is that water developments attract predators, which then impact the prey populations that these developments are intended to benefit. To examine the extent of predator activity around water developments, we examined 15 paired water and non-water (random) sites for sign (scats, tracks, visual observations, animal parts such as feathers and bones, and carcasses) of predators and prey. Predator sign was 7x greater around water sites than non-water sites (P = 0.002). Coyote (Canis latrans Say) sign accounted for 79% of all predator sign and was 7x greater near water than away from water (P = 0.006). Amount of sign for all prey species combined was not different between paired sites (P = 0.6), but results for individual species and groups of species was variable; passerine and gallinaceous bird sign was greater around water sites (P = 0.008), ungulate sign was not different between water and non-water sites (P greater than or equal to 0.20), and lagomorph sign was almost 2x greater away from water than near water (P = 0.05). Predators were probably attracted to wildlife water developments to drink rather than hunt; without water developments, predators may be even more concentrated around the fewer natural water sites.