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We assessed plant interspaces in July 2007 using continuous line intercepts in twice-replicated pastures of northern mixed-grass prairie with contrasting grazing treatments: 1) long-term (25 yr) heavily grazed, dominated by the bunchgrass blue grama (Bouteloua gracilis), and 2) ungrazed, dominated by the rhizomatous grass western wheatgrass (Pascopyrum smithii). The number of plant interspaces was 26% higher in pastures heavily grazed, but the amount of soil surface occupied by plant interspaces was 27% greater without grazing. Plant interspaces were larger without grazing (14.8 6 1.2 cm, mean 6 1 SE) than heavily grazed (8.9 6 0.4 cm). Plant interspaces represented 87% and 68% of the total soil surface in the ungrazed and heavily grazed communities, respectively. The percentage of soil surface covered by plant interspaces , 20 cm was higher for the heavily grazed (94%) compared to the ungrazed (79%). Litter cover in the plant interspaces was higher without grazing (80 6 1%) compared to the heavily grazed (57 6 3%). Grazing-induced structural changes from a rhizomatous-to a bunchgrass-dominated vegetation community were manifest in the size and distribution of plant interspaces. Ecological consequences for erosion from raindrop impacts in larger plant interspaces in the ungrazed community are likely offset by greater litter cover in these communities; conversely, lower litter cover in heavily grazed pastures may increase erosion potential despite occurrence of smaller plant interspaces and less proportion of the soil surface covered by interspaces. Management practices that increase the cover of litter in plant interspaces should reduce the potential of erosion from water and wind in this semiarid rangeland. Resumen Determinamos los espacios entre plantas en Julio del 2007 utilizando la línea de intercepto continuo en potreros con dos repeticiones en un pastizal mediano abierto del noroeste de los Estados Unidos contrastando tratamientos de pastoreo 1): largoplazo (25 añ os) con un pastoreo intenso, y dominado principalmente por el pasto navajita (Bouteloua gracilis), y 2) sin pastorear dominado principalmente por western wheatgrass (Pascopyrum smithii). El número de espacios entre plantas fue 26% mayor en el pastoreo intenso, pero la cantidad de superficie del suelo ocupada por los espacios entre las plantas fue 27% mayor en áreas sin pastoreo. Los espacios entre las plantas fueron mayores en áreas sin pastoreo (14.8 6 1.2 cm, media 6 1 es) que en áreas con pastoreo intenso (8.9 6 0.4 cm). Los espacios entre las plantas representaron 87% y 68% del total de la superficie del suelo en áreas sin pastoreo y en áreas con el pastoreo intenso, respectivamente. El porcentaje de la superficie del suelo cubierto por los espacios entre las plantas , 20 cm fue mayor (94%) para el área pastoreada intensamente que para el área sin pastoreo (79%). La cubierta del mantillo en los espacios entre las plantas fue mayor en el área sin pastoreo (80 6 1%) comparado con el pastoreo intenso (57 6 3%). El pastoreo induce cambios estruct...

The CBNG well water is typically managed by discharging into nearby disposal ponds. The CBNG well water could potentially be very useful in the water-limited regions (e.g., arid and semi-arid), but beneficial uses may be hindered by water quality problems. Objectives of this research were to: (1) examine trend analysis of nine years of CBNG well water at discharge (outfall) points and in corresponding disposal ponds, (2) evaluate geochemical processes, (3) identify potential water quality issues, and (4) find potential beneficial uses. The CBNG well water at discharge points and in corresponding disposal ponds was measured on-site for pH and electrical conductivity (EC). These water samples were also analyzed in the laboratory for calcium (Ca), sodium (Na), magnesium (Mg), potassium (K), iron (Fe), aluminum (Al), copper (Cu), arsenic (As), selenium (Se), cadmium (Cd), and barium (Ba). Total dissolved solids (TDS) were calculated from EC measurements. The sodium adsorption ratio (SAR) was calculated from Na, Ca, and Mg concentrations. Trend analyses of outfalls and disposal ponds were conducted separately so that the differences in trends could be compared. Trends in CBNG well water at discharge points are not always the same as trends in CBNG disposal ponds: environmental and geochemical processes play an important role in the water quality of these well waters. Overall trend analyses suggest that CBNG well water at discharge points in all basins of the Powder River Basin meets beneficial use criteria, except for SAR and to some extent EC, for aquatic life, livestock and wildlife watering, and irrigation. The CBNG well water in disposal ponds across all basins meets criteria for all beneficial uses except for As, pH, SAR, and to some extent EC for irrigation, aquatic life, and livestock and wildlife watering.