29 research outputs found
Like-minded sources on Facebook are prevalent but not polarizing
Many critics raise concerns about the prevalence of ‘echo chambers’ on social media and their potential role in increasing political polarization. However, the lack of available data and the challenges of conducting large-scale field experiments have made it difficult to assess the scope of the problem 1,2. Here we present data from 2020 for the entire population of active adult Facebook users in the USA showing that content from ‘like-minded’ sources constitutes the majority of what people see on the platform, although political information and news represent only a small fraction of these exposures. To evaluate a potential response to concerns about the effects of echo chambers, we conducted a multi-wave field experiment on Facebook among 23,377 users for whom we reduced exposure to content from like-minded sources during the 2020 US presidential election by about one-third. We found that the intervention increased their exposure to content from cross-cutting sources and decreased exposure to uncivil language, but had no measurable effects on eight preregistered attitudinal measures such as affective polarization, ideological extremity, candidate evaluations and belief in false claims. These precisely estimated results suggest that although exposure to content from like-minded sources on social media is common, reducing its prevalence during the 2020 US presidential election did not correspondingly reduce polarization in beliefs or attitudes
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Interception of Rainfall by Tarbush
The objective of this study was to determine the interception by tarbush of artificially applied rainfall. Twelve tarbush shrubs were collected near Las Cruces in southern New Mexico to obtain a representative sample of shrub size classes. Simulated rainfall was applied at the rate of 6 cm/hr for 30 min. Canopy cover of the tarbush community was determined from 10 line intercept transects 30.48 m long. A stepwise regression analysis using the minimum R2 improvement technique was used to examine the effects of plant parameters on interception. The "best" one variable model was shrub green weight, which accounted for 75% of the variability of the intercepted rainfall. Extrapolating the calculated interception of artifically applied rainfall to the native stand of tarbush with 15.2% canopy cover indicated that 0.5 mm of rainfall would be intercepted from a 30 mm rainfall event. Disregarding rainfall events of less than 3.0 mm, an average of 8.5 mm of rainfall would be intercepted by the tarbush community or 6.7% of the average rainfall from May through October.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Semiarid Rangeland Treatment and Surface Runoff
Effects of pitting and rootplowing on surface runoff were determined on a desert shrub range in southeastern Arizona, and the time-dependent changes in the soil surface characteristics resulting from these practices were studied. Additional detention storage was provided by increased roughness in microtopography, thereby decreasing surface runoff when compared to the control. Rock and gravel were negatively correlated with surface runoff. Combining the two parameters showed a significant reduction in surface runoff. Increases in runoff were associated with exposed soil. Crown cover significantly reduced runoff. Litter was not significant in the reduction of runoff. Regulation of surface runoff is important for on-site rangeland improvements as well as reducing sediment yields.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Infiltration Rates on Rootplowed Rangeland
Infiltration and runoff from mechanically treated arid Southwestern rangeland were measured. Control plots dominated by creosotebush had greater infiltration rates than the 1972 and 1976 rootplowed and seeded treatments, stressing the importance of cover for reducing runoff and controlling erosion. Infiltration rates on dry soils were significantly higher on the 1972 rootplowed and seeded treatment compared with the 1976 rootplowed and seeded treatment, indicating the lack of soil structure in the 1976 treatment.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Increasing Forage Production on a Semiarid Rangeland Watershed
From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, ArizonaTwo native grass species, blue grama and sidecoats, were successfully seeded on a semiarid rangeland on the walnut gulch experimental watershed in southeastern Arizona. Optimum seeding dates selected were those within the time period most likely to receive precipitation, and grass stands were established in two successive years with average rainfall. Shrubs were killed by root-plowing at a depth of 14 inches, a procedure which was more than 95% successful in controlling sprouting shrubs. Forage production measurements taken on nm-28 sideoats and Vaughn sideoats showed a yield of 1,950 and 2,643 pounds of forage per acre, respectively, for the 2 years following the seeding, whereas untreated sites produced 23 and 25 pounds per acre of forage. Results indicate that success in establishing a stand of native grass is increased through use of existing hydrologic data.This article is part of the Hydrology and Water Resources in Arizona and the Southwest collections. Digital access to this material is made possible by the Arizona-Nevada Academy of Science and the University of Arizona Libraries. For more information about items in this collection, contact [email protected]
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Rangeland Ponding Dikes: Design Criteria
Water ponding is used for controlling onsite and runon water while increasing infiltration and soil water storage. The dikes are constructed in a crescent or horseshoe shape, with the first dike constructed at the highest elevation on the site and additional dikes at progressively lower elevations. Some factors affecting dike construction, layout and spacing are water ponding depth, percent slope, soil type, and site topography. Such dikes have improved soil water regime on arid rangelands by increasing the infiltration opportunity and have decreased the soil erosion potential by controlling overland flow.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Factors influencing infiltrability of semiarid mountain slopes
The objective of this research was to determine the effects of selected vegetation, soil, rock, and slope variables on infiltration of semiarid rangelands with slope gradients ranging from 0-70%. Analyses were made on 2 sets of data collected a year apart in the Guadalupe Mountains of New Mexico and consisted of Pearson and partial correlation analysis of the dependent infiltration variables and independent site variables. In addition, infiltration was regressed against uncorrelated factors produced by factor analysis. Vegetal cover and biomass strongly influenced infiltration. The relative importance of grasses, shrubs or litter was dependent on their respective abundance, especially grass. Soil depth also limited infiltration especially as soil water storage became satisfied. Infiltrability was negatively correlated with rock cover and the smallest rock size fragments were the most negatively related. When the effects of vegetal cover and slope were removed (using partial correlation analysis) however, the median sized rock fragments (26-150 mm) were positively related to infiltrability, and the smallest rock fragements (2-12 mm) were negatively related. Partial correlation analysis also suggested a positive correlation between infiltrability and slope gradient.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Water Properties of Caliche
Water absorption and retention by hard caliche nodules (rocks) collected from soils in southern New Mexico were determined. The rate of water uptake by the caliche rocks was rapid and water content at saturation was 13.0% by weight (24.7% by volume). At a matrix potential of -0.7 MPa, the rocks retained 10.6% water by weight, an 18% loss from saturation. Water loss from saturated rocks to a dry atmosphere was slow, but most of the absorbed water was released. The rocks contained only 0.6% water by weight (1.1% by volume) after 34 days in a desiccator. Both laboratory and field trials indicated that, although indurated caliche layers will absorb large amounts of water, the water does not pass through the layers to the soil below.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Soil Movement in Mesquite Dunelands and Former Grasslands of Southern New Mexico from 1933 to 1980
Soil levels were marked on grid and transect stakes in mesquite duneland and grassland areas at 3 sites on the Jornada Experimental Range in 1933 and 1935. Soil levels on one set of transect stakes were remeasured in 1950 and 1955. Remeasurement of soil levels at both transect and grid stakes in 1980 revealed that extensive soil movement had occurred during the intervening years. On a 259-ha site containing large mesquite dunes in 1935, maximum deposition and deflation was 86.9 and 64.6 cm, respectively, in 1980. There was a net gain of 1.9 cm in soil depth over the entire area. On a 259-ha site only partially occupied by mesquite dunes in 1933, there was a net loss of 4.6 cm in soil depth and mesquite dunes had completely occupied the site by 1980. On a transect established across a mesquite duneland-grassland ecotone in 1935, there was a net loss in soil depth of 3.4 cm. Mesquite dunes had completely occupied the former grassland and dune intercept increased from 34.9 m in 1935 to 149.6 m in 1980. Gross erosion rates on wind deflated areas were equivalent to 69 tonnes ha-1 yr-1 on the area of large mesquite dunes. On the area partially occupied by mesquite in 1935 the gross erosion rate was 52 tonnes ha-1 yr-1. At the ecotone transect gross erosion rates were 45, 101, and 40 tonnes ha-1 yr-1 for 1935-50, 1950-55, and 1955-80 periods, respectively.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202