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Interactions among soil fertility, grazing history, and climatic variability in semi-arid grasslands, southeastern Utah

The physical and ecological landscapes of American drylands are especially vulnerable to change from short-term climatic variability (a few seasons to years) and land uses. Poor understanding of the complex interactions among geologic and ecologic processes currently limit our ability to predict landscape response to climatic and human influences. Recent progress in understanding these interactions comes from study of physical and biogeochemical properties of grassland soil in southeastern Utah (Neff and others, 2005; Reynolds and others, 2006). Several study sites (on National Park, Bureau of Land Management, and private ranchland) are essentially identical in physiographic and climatic setting but have different past and current land uses: Currently grazed, previously grazed, and never grazed by domestic livestock. Surface soils in the previously grazed sites have much lower amounts of soil nutrients and fine-grained sediment (silt) relative to soil never exposed to livestock grazing. These differences have further detrimental effects on soil respiration (beneficial microbial activity is diminished) and water-holding capacity. Measurement of climatic variability and erosion at the sites reveals that dust emission is the primary process of sediment removal, promoting the selective loss of fine-grained, nutrient-rich particles. The highest amounts of wind erosion are found at a currently grazed site. The recent drought in the region, culminating in 2002, intensified wind erosion from all sites, except the one that had never been grazed.

For more information, please visit:

• Multi-decadal impacts of grazing on soil physical and biogeochemical properties in southeast Utah
• Atmospheric dust in modern soil on aeolian sandstone, Colorado Plateau (USA): Variation with landscape position and contribution to potential plant nutrients