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Reestablishing perennial vegetation dominance in ventenata (Ventenata dubia)– and other annual grass-invaded rangelands is critical to restoring ecological function and increasing ecosystem goods and services. Recovery of perennial dominance in ventenata-invaded rangelands is challenging and constrained by a lack of established best management practices; however, preemergent herbicides can, at least temporarily, reduce ventenata. Indaziflam is a preemergent herbicide that has longer soil activity than other commonly used preemergent herbicides that needs evaluated to determine if it offers multiple-year control of ventenata and to determine its effects on residual perennial vegetation. Some ventenata-invaded rangelands may not have enough residual vegetation to occupy the site after ventenata control, but longer soil activity with indaziflam likely limits establishment of seeded species. However, incorporating seeds in activated carbon pellets, which can limit herbicide damage, may be a strategy for establishing perennial vegetations simultaneously with indaziflam application. We evaluated 1) applying indaziflam to control ventenata and 2) broadcast-seeding perennial grass seed incorporated in activated carbon pellets with a simultaneous indaziflam application at two sites for 3 yr post treatment. Indaziflam controlled ventenata for the 3 yr sampled. Perennial grasses increased with indaziflam at the site that had more residual perennial grasses before treatment. At the other site, perennial forbs increased with indaziflam. Indaziflam offers multiple-year control of ventenata; however, plant community response depends on composition before treatment. Seeding perennial grass seeds incorporated in activated carbon pellets while indaziflam controlled ventenata did not increase perennial grass abundance. Though this was likely associated with low establishment due to below-average precipitation post seeding and because broadcast seeding is often an ineffective seeding method, we cannot rule out nontarget herbicide damage. Further evaluations of activated carbon technologies used in conjunction with indaziflam are needed to determine if this can be an effective management strategy.
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Targeted grazing in the Great Basin has been used to reduce cheatgrass fuel loads and enhance wildfire control. In this project, we evaluate the economic impact of targeted grazing on cow-calf ranches across southeast Oregon, northeast Nevada, and southwest Idaho when practices such as fencing, water hauling, and herding are necessary for producers to accomplish desired grazing outcomes. Large and small representative ranch models were developed for major land resource areas 23, 24, and 25 where applicable. Typical targeted grazing costs and practices were obtained from producer and agency focus groups in each state and introduced into ranch economic models. Targeted grazing periods begin 1 mo before typical Bureau of Land Management turnout in the spring and again in the fall after typical public land grazing ends. In each year, targeted grazing would occur when the previous growing season (September to March and April to August) had more than 25% of median precipitation based on PRISM historical data. Hence, targeted grazing could occur in the spring, fall, or both depending on precipitation. In both seasons, targeted grazing continues until the desired animal unit months of forage are removed. One hundred precipitation data sets were randomly generated using Excel to mimic the actual number of drought years in the spring and fall. The model is a 40-yr recursive linear programming model using 100 cattle price sets and the 100 precipitation sets. Results are averaged over 10 000 model runs and compared with scenarios with no targeted grazing and targeted grazing based on the actual precipitation data set. Results show changes in cattle herd size, hay sales, and the economic impacts to the public land ranch operation for two ranch sizes in each of the three major land resource areas by state.
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The Great Basin is an arid province located in the interior western United States. The region encompasses millions of hectares and quaking aspen forests comprise a minor portion of the total area. However, montane aspen forests play a disproportionately large role in providing ecosystem services in the region, including water retention, biodiversity, wildlife habitat, livestock forage, and recreational uses. With warming temperatures, increasing evaporative demand, and heightened precipitation variability, the future of aspen has become a critical concern. Using dendroecological approaches, we assessed growth patterns of 20 aspen stands across three geographically isolated “sky island” mountain ranges spanning portions of the northcentral Great Basin. We anticipated that the growth of Great Basin aspen would be strongly influenced by regional climatic patterns and largely in synchrony. Results revealed a more complex growth dynamic that varied among mountain ranges and across environmental gradients. In particular, aspen climate-growth relationships in the slightly dryer Ruby Mountains were strongly and positively correlated (r > 0.5) with previous fall to winter moisture availability. The Jarbidge Mountains had a positive but modest relationship with previous fall to winter moisture availability (r > 0.3). Climate-growth response in the Santa Rosa Mountains, the wettest range, showed no significant response to moisture availability during any time period examined but had greater tree-ring growth with warmer May temperatures. Although tree-ring centennial (1910 – 2010) growth trends were positive for all three mountain ranges, only the Santa Rosa Mountains maintained a positive recent growth trend (1970 – 2010). Moreover, distinct temporal shifts in tree growth-climate relationships in each mountain range suggest potentially unique aspen population adaptations to climate variability. For instance, in two of the mountain ranges, there was a shift from positive/neutral to negative growth relationships with temperature starting around the 1963 – 1987 time period, while tree growth also began simultaneously responding more positively to moisture availability. These growth shifts and observed enhanced sensitivities to monthly and seasonal climate variables over time may reflect dynamic tree growth responses caused by ongoing global climate change, but that may be tempered by local or regional factors, such as the relative availability and timing of soil moisture provided by spring snowmelt. A better understanding of biogeographic variation and causality in aspen growth could provide multiple management pathways governed by resilience characteristics in the face of future anthropogenic and climatic threats.
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Biocrusts are sensitive to changes in livestock grazing intensity in arid rangelands and may be useful indicators of ecosystem functions, particularly soil properties like soil stability, which may suggest the potential for soil erosion. We compared biocrust community composition and surface soil stability in a big sagebrush steppe rangeland in the northwestern Great Basin in several paired sites, with or without long-term cattle grazing exclusion, and similar soils (mostly sandy loams), climate, and vegetation composition. We found that livestock grazing was associated with both lower surface soil stability and cover of several biocrust morphogroups, especially lichens, compared with sites with long-term livestock exclusion. Surface soil stability did not modify the effects of grazing on most biocrust components via interactive effects. Livestock grazing effects on total biocrust cover were partially mediated by changes in surface soil stability. Though lichens were more sensitive to grazing disturbance, our results suggest that moss (mostly Tortula ruralis in this site) might be a more readily observable indicator of grazing-related soil stability change in this area due to their relatively higher abundance compared with lichens (moss: mean, 8.5% cover, maximum, 96.1%, lichens: mean, 1.0% cover, maximum, 14.1%). These results highlight the potential for biocrust components as sensitive indicators of change in soil-related ecosystem functions in sagebrush steppe rangelands. However, further research is needed to identify relevant indicator groups across the wide range of biocrust community composition associated with site environmental characteristics, variable grazing systems, other rangeland health metrics, and other disturbance types such as wildfire.
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This study evaluated vegetation response to different intensities of deferred rotation cattle grazing over 16 years (2007–2022) on burned Wyoming big sagebrush steppe in eastern Oregon. Treatments were applied in a randomized complete block, which included no grazing on burned (nonuse, n = 5) and unburned (control, n = 5) steppe; and cattle grazing at low (low, n = 4), moderate (moderate, n = 4), and high (high, n = 4) intensities on burned steppe. Vegetation dynamics were evaluated by repeated measures analysis of canopy cover and density of shrub and herbaceous species and functional groups. Herbaceous functional groups were an early-season bunchgrass (one species, Sandberg bluegrass), tall perennial bunchgrasses, perennial forbs, annual grass (one species, cheatgrass), and annual forbs. Tall perennial bunchgrass, Sandberg bluegrass, and perennial forb cover and density did not differ among the treatments but did decrease over time in all treatments. The cover of several tall bunchgrass species was generally less in the high treatment, mainly, Idaho fescue and Thurber’s needlegrass. The cover of cheatgrass and annual forbs varied among years but was greater in the burned-grazed and nonuse treatments than in the control. Native plant cover in the burned treatments (grazed and nonuse) represented 77%–85% of total herbaceous cover versus the control where native plants comprised 91% of the total. Annual weather variability appears to account for most of the compositional dynamics measured in the various grazed and ungrazed treatments.
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Aims Invasion by annual grasses (IAGs) and concomitant increases in wildfire are impacting many drylands globally, and an understanding of factors that contribute to or detract from community resistance to IAGs is needed to inform postfire restoration interventions. Prefire vegetation condition is often unknown in rangelands but it likely affects variation in postfire invasion resistance across large burned scars. Whether satellite‐derived products like the Rangeland Analysis Platform (RAP) can fulfill prefire information needs and be used to parametrize models of fire recovery to inform postfire management of IAGs is a key question. Methods We used random forests to ask how IAG abundances in 669 field plots measured in the 2‐3 years following megafires in sagebrush steppe rangelands of western USA responded to RAP estimates of annual:perennial prefire vegetation cover, the effects of elevation, heat load, postfire treatments, soil moisture–temperature regimes, and land‐agency ratings of ecosystem resistance to invasion and resilience to disturbance. Results Postfire IAG cover measured in the field was % and RAP‐estimated prefire annual herbaceous cover was %. The random forest model had an R² of 0.36 and a root‐mean‐squared error (RMSE) of 4.41. Elevation, postfire herbicide treatment, and prefire estimates from RAP for the ratio of annual:perennial and shrub cover were the most important predictors of postfire IAG cover. Threshold‐like relationships between postfire IAG cover and the predictors indicate that maintaining annual:perennial cover below 0.4 and shrub cover below <10% prior to wildfire would decrease invasion, at low elevations below 1400 m above sea level. Conclusion Despite known differences between RAP and field‐based estimates of vegetation cover, RAP was still a useful predictor of variation in IAG abundances after fire. IAG management is oftentimes reactive, but our findings indicate impactful roles for more inclusively addressing the exotic annual community, and focusing on prefire maintenance of annual:perennial herbaceous and shrub cover at low elevations.
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During the 2011-to-2021 study period, increases in the number of days of heavy smoke were observed in communities representing 87.3% of the US population, with notably large increases in communities characterized by racial or ethnic minority status, limited English proficiency, lower educational attainment, and crowded housing conditions.
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While increased length and intensity of wildfire seasons in many places have led to more concern about wildland firefighter safety, we believe ethnography has been underutilized as a method within this domain. In response, we begin building a shared idiom for ethnographic engagement with wildland firefighter safety and similar occupations. We draw on ethnographic approaches to late industrialism to develop a method called discursive risk analysis (DRA) as an initial stage in a broader collaborative and generative research practice. By collaborative, we mean cooperation among stakeholder, disciplinary, professional, and other groups. We use DRA to analyze ethnographic data and documentary sources relevant to discussions of ‘the Big Lie’ among firefighters and agency leadership. The Big Lie is a term that both firefighters and agency leaders used to suggest that wildland firefighters are being harmed by agency discourse that says firefighters will be kept safe despite the unavoidable danger of the job. It is important to the Big Lie discussion that this harm is conceptualized by firefighters as discursively driven, necessitating a research method attentive to discourse. Discursive Risk Analysis of the Big Lie discussion suggests two discursive gaps that may result in two discursive risks. The first gap, found in agency discourse, is that ‘everyone knows the job is dangerous’ but ‘zero fatalities is a reasonable goal.’ This gap is associated with a discursive risk, a possible decrease in trust among wildland firefighters in agency leadership. The second gap, observed in firefighter discourse, is that ‘the job is dangerous’ but ‘no one will get hurt today.’ This gap is associated with another discursive risk, the possibility of decreased situational awareness. Finally, we clarify each of these gaps and risks through two anthropological concepts (the Sapir–Whorf hypothesis and the public secret) that can bring new perspectives to discussions about institutional cultures of health and safety.
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Effective wildlife management requires robust information regarding population status, habitat requirements, and likely responses to changing resource conditions. Single-species management may inadequately conserve communities and result in undesired effects to non-target species. Thus, management can benefit from understanding habitat relationships for multiple species. Pinyon pine and juniper are expanding into sagebrush-dominated ecosystems within North America and mechanical removal of these trees is frequently conducted to restore sagebrush ecosystems and recover greater sage-grouse. However, pinyon-juniper removal effects on non-target species are poorly understood, and changing pinyon-juniper woodland dynamics, climate, and anthropogenic development may obscure conservation priorities. To better predict responses to changing resource conditions, evaluate non-target effects of pinyon-juniper removal, prioritize species for conservation, and inform species recovery within pinyon-juniper and sagebrush ecosystems, we modeled population trends and density-habitat relationships for four sagebrush-associated, four pinyon-juniper-associated, and three generalist songbird species with respect to these ecosystems. We fit hierarchical population models to point count data collected throughout the western United States from 2008 to 2020. We found regional population changes for 10 of 11 species investigated; 6 of which increased in the highest elevation region of our study. Our models indicate pinyon-juniper removal will benefit Brewer’s sparrow, green-tailed towhee, and sage thrasher densities. Conversely, we predict largest negative effects of pinyon-juniper removal for species occupying early successional pinyon-juniper woodlands: Bewick’s wren, black-throated gray warblers, gray flycatcher, and juniper titmouse. Our results highlight the importance of considering effects to non-target species before implementing large-scale habitat manipulations. Our modeling framework can help prioritize species and regions for conservation action, infer effects of management interventions and a changing environment on wildlife, and help land managers balance habitat requirements across ecosystems.
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Sagebrush shrublands in the Great Basin, USA, are experiencing widespread increases in wildfire size and area burned resulting in new policies and funding to implement fuel treatments. However, we lack the spatial data needed to optimize the types and locations of fuel treatments across large landscapes and mitigate fire risk. To address this, we developed treatment response groups (TRGs)—sagebrush and pinyon-juniper vegetation associations that differ in resilience to fire and resistance to annual grass invasion (R&R) and thus responses to fuel treatments.