Vegetation, Hydrologic, and Erosion Responses of Sagebrush Steppe 9 Yr Following Mechanical Tree Removal

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Abstract Land managers across the western United States are faced with selecting and applying tree-removal treatments on pinyon (Pinus spp.) and juniper (Juniperus spp.) woodland-encroached sagebrush (Artemisia spp.) rangelands, but current understanding of long-term vegetation and hydrological responses of sagebrush sites to tree removal is inadequate for guiding management. This study applied a suite of vegetation and soil measures (0.5 − 990 m2), small-plot rainfall simulations (0.5 m2), and overland flow experiments (9 m2) to quantify the effects of mechanical tree removal (tree cutting and mastication) on vegetation, runoff, and erosion at two mid- to late-succession woodland-encroached sagebrush sites in the Great Basin, United States, 9 yr after treatment. Low amounts of hillslope-scale shrub (3 − 15%) and grass (7 − 12%) canopy cover and extensive intercanopy (area between tree canopies) bare ground (69 − 88% bare, 75% of area) in untreated areas at both sites facilitated high levels of runoff and sediment from high-intensity (102 mm • h− 1, 45 min) rainfall simulations in interspaces (~ 45 mm runoff, 59 − 381 g • m− 2 sediment) between trees and shrubs and from concentrated overland flow experiments (15, 30, and 45 L • min− 1, 8 min each) in the intercanopy (371 − 501 L runoff, 2 342 − 3 015 g sediment). Tree cutting increased hillslope-scale density of sagebrush by 5% and perennial grass cover by twofold at one site while tree cutting and mastication increased hillslope-scale sagebrush density by 36% and 16%, respectively, and perennial grass cover by threefold at a second more-degraded (initially more sparsely vegetated) site over nine growing seasons. Cover of cheatgrass (Bromus tectorum L.) was