Life Sciences Commons^™

A Synthesis Of The Effects Of Cheatgrass Invasion On Us Great Basin Carbon Storage, R. Chelsea Nagy, Emily J. Fusco, Jennifer K. Balch, John T. Finn, Adam Mahood, Jenica M. Allen, Bethany A. Bradley

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1. Non-native, invasive Bromus tectorum (cheatgrass) is pervasive in sagebrush ecosystems in the Great Basin ecoregion of the western United States, competing with native plants and promoting more frequent fires. As a result, cheatgrass invasion likely alters carbon (C) storage in the region. Many studies have measured C pools in one or more common vegetation types: native sagebrush, invaded sagebrush and cheatgrass-dominated (often burned) sites, but these results have yet to be synthesized.
2. We performed a literature review to identify studies assessing the consequences of invasion on C storage in above-ground biomass (AGB), below-ground biomass (BGB), litter, organic soil and total …

Long‐Term Effects Of Tree Expansion And Reduction On Soil Climate In A Semiarid Ecosystem, Bruce A. Roundy, R. F. Miller, R. J. Tausch, J. C. Chambers, B. M. Rau

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In sagebrush ecosystems, pinyon and juniper tree expansion reduces water available to perennial shrubs and herbs. We measured soil water matric potential and temperatures at 13–30 and 50–65 cm soil depths in untreated and treated plots across a range of environmental conditions. We sought to determine the effects of tree expansion, tree reduction treatments, and expansion phase at time of treatment over 12–13 yr post‐treatment. Because the effects of tree reduction on vegetation can vary with the soil temperature/moisture regime, we also analyzed differences in soil climate variables between the mesic/aridic‐xeric and frigid/xeric regime classifications for our sites. Growing conditions …

Treatment Longevity And Changes In Surface Fuel Loads After Pinyon–Juniper Mastication, Samuel S. Wozniak, Eva K. Strand, Timothy R. Johnson, April Hulet, Bruce A. Roundy, Kert Young

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In the Intermountain West, land managers masticate pinyon pine (Pinus spp.) and juniper (Juniperus spp.) trees that have encroached sagebrush steppe communities to reduce canopy fuels, alter potential fire behavior, and promote growth of understory grasses, forbs, and shrubs. At three study sites in Utah, 45 sampling plots spanning a range of tree cover from 5% to 50% were masticated. We measured surface fuel load components three times over a 10‐yr period. We also measured tree cover, density, and height as indicators of treatment longevity. Changes in these variables were analyzed across the range of pre‐treatment tree cover …

Spatial And Temporal Changes In Ecosystem Carbon Pools Following Juniper Encroachment And Removal, Heather L. Throop, Kate Lajtha

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Proliferation of woody plants is a predominant global land cover change of the past century, particularly in dryland ecosystems. Woody encroachment and its potential impacts (e.g., livestock forage, wildlife habitat, hydrological cycling) have led to widespread brush management. Although woody plants may have substantial impacts on soils, uncertainty remains regarding woody encroachment and brush management influences on carbon (C) pools. Surface C pools (shallow soils and litter) may be particularly dynamic in response to encroachment and brush management. However, we have limited understanding of spatiotemporal patterns of surface C responses or how surface pools respond relative to aboveground C, litter, …

Sage Grouse Groceries: Forb Response To Piñon-Juniper Treatments, Jonathan D. Bates, Kirk W. Davies, April Hulet, Richard F. Miller, Bruce Roundy

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Juniper and piñon coniferous woodlands have increased 2- to 10-fold in nine ecoregions spanning the Intermountain Region of the western United States. Control of piñon-juniper woodlands by mechanical treatments and prescribed fire are commonly applied to recover sagebrush steppe rangelands. Recently, the Sage Grouse Initiative has made conifer removal a major part of its program to reestablish sagebrush habitat for sage grouse (Centrocercus urophasianus) and other species. We analyzed data sets from previous and ongoing studies across the Great Basin characterizing cover response of perennial and annual forbs that are consumed by sage grouse to mechanical, prescribed fire, …

Vegetation Response To Piñon And Juniper Tree Shredding, Jordan Bybee, Bruce A. Roundy, Kert R. Young, April Hulet, Darrell B. Roundy, Leann Crook, Zachary Aanderud, Dennis L. Eggett, Nathan L. Cline

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Piñon (Pinus spp.) and juniper (Juniperus spp.) expansion and infilling in sagebrush (Artemisia L.) steppe communities can lead to high-severity fire and annual weed dominance. To determine vegetation response to fuel reduction by tree mastication (shredding) or seeding and then shredding, we measured cover for shrub and herbaceous functional groups on shredded and adjacent untreated areas on 44 sites in Utah. We used mixed model analysis of covariance to determine significant differences among ecological site type (expansion and tree climax) and treatments across a range of pretreatment tree cover as the covariate. Although expansion and tree climax …

Response Of Conifer-Encroached Shrublands In The Great Basin To Prescribed Fire And Mechanical Treatments, Richard F. Miller, Jaime Ratchford, Bruce A. Roundy, Robin J. Tausch, April Hulet, Jeanne C. Chambers

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In response to the recent expansion of piñon and juniper woodlands into sagebrush-steppe communities in the northern Great Basin region, numerous conifer-removal projects have been implemented, primarily to release understory vegetation at sites having a wide range of environmental conditions. Responses to these treatments have varied from successful restoration of native plant communities to complete conversion to nonnative invasive species. To evaluate the general response of understory vegetation to tree canopy removal in conifer-encroached shrublands, we set up a region-wide study that measured treatment-induced changes in understory cover and density. Eleven study sites located across four states in the Great …

Mechanical Mastication Of Utah Juniper Encroaching Sagebrush Steppe Increases Inorganic Soil N, Kert R. Young, Bruce A. Roundy, Dennis L. Eggett

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Juniper (Juniperus spp.) has encroached on millions of hectares of sagebrush (Artemisia spp.) steppe. Juniper mechanical mastication increases cover of understory species but could increase resource availability and subsequently invasive plant species. We quantified the effects of juniper mastication on soil resource availability by comparing total C, total N, C : N ratio, Olsen extractable P, sulfate S, and pH using soil samples and inorganic N (NO₃^-+NH₄⁺) using ion exchange membranes. We compared resource availability in paired masticated and untreated areas in three juniper-dominated sagebrush and bunchgrass ecosystems in the Utah portion …

Hydrologic And Erosion Responses To Wildfire Along The Rangeland-Xeric Forest Continuum In The Western Us: A Review And Model Of Hydrologic Vulnerability, Christopher Jason Williams, Frederick B. Pierson, Peter R. Robichaud, Jan Boll

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The recent increase in wildfire activity across the rangeland–xeric forest continuum in the western United States has landscape-scale consequences in terms of runoff and erosion. Concomitant cheatgrass (Bromus tectorum L.) invasions, plant community transitions and a warming climate in recent decades along grassland–shrubland–woodland–xeric forest transitions have promoted frequent and large wildfires, and continuance of the trend appears likely if warming climate conditions prevail. These changes potentially increase overall hydrologic vulnerability by spatially and temporally increasing soil exposure to runoff and erosion processes. Plot and hillslope-scale studies demonstrate burning may increase event runoff or erosion by factors of 2–40 over …

Diffuse Migratory Connectivity In Two Species Of Shrubland Birds: Evidence From Stable Isotopes, Steven T. Knick, Matthias Leu, John T. Rotenberry, Steven E. Hanser, Kurt A. Fesenmyer

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Connecting seasonal ranges of migratory birds is important for understanding the annual template of stressors that influence their populations. Brewer’s sparrows (Spizella breweri) and sagebrush sparrows (Artemisiospiza nevadensis) share similar sagebrush (Artemisia spp.) habitats for breeding but have different population trends that might be related to winter location. To link breeding and winter ranges, we created isoscapes of deuterium [stable isotope ratio (δ) of deuterium; δ ²H] and nitrogen (δ ¹⁵N) for each species modeled from isotope ratios measured in feathers of 264 Brewer’s and 82 sagebrush sparrows and environmental …

Woodland Expansion's Influence On Belowground Carbon And Nitrogen In The Great Basin U.S., Benjamin M. Rau, Dale W. Johnson, Robert R. Blank, Robin J. Tausch, Bruce A. Roundy, Richard F. Miller, Todd G. Caldwell, Annmarie Lucchesi

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Vegetation changes associated with climate shifts and anthropogenic disturbance can have major impacts on biogeochemical cycling and soils. Much of the Great Basin, U.S. is currently dominated by sagebrush (Artemisia tridentate (Rydb.) Boivin) ecosystems. Sagebrush ecosystems are increasingly influenced by pinyon (Pinus monophylla Torr. & Frém and Pinus edulis Engelm.) and juniper (Juniperus osteosperma Torr. and Juniperus occidentalis Hook.) expansion. Some scientists and policy makers believe that increasing woodland cover in the intermountain western U.S. offers the possibility of increased organic carbon (OC) storage on the landscape; however, little is currently known about the distribution of OC …

Sagebrush Steppe Treatment Evaluation Project (Sagestep): Restoration Research With Practical Applications, Summer Olsen

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Sagebrush rangelands cover millions of acres in the Great Basin including parts of Oregon, California, Idaho, Nevada, and Utah. This land provides a variety of important services, including wildlife habitat, clean water, recreation, and economic opportunities; it also serves as the primary forage base for the western livestock industry. Healthy sagebrush rangelands are rapidly being lost due to a variety of factors including severe wildfires, woodland expansion, invasion of non-native species, urban development, and drought. This loss can have significant impacts on those who depend on the land for goods and services.