Research and Publications
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Frequent and catastrophic wildfires are an increasing threat to the ecological and economic stability of Great Basin rangelands, specifically sagebrush rangelands at risk of exotic annual grass invasion (Crist et al. this issue). Historically, fires were a periodic disturbance in these communities that shifted dominance from woody vegetation to herbaceous vegetation (Wright and Bailey 1982; Miller and Rose 1999) and likely promoted diversity (Davies and Bates 2020). Alterations in fuel characteristics with exotic plant invasions and increased anthropogenic ignitions have greatly elevated the likelihood of wildfires in many of these rangelands (Balch et al. 2013; Fusco et al. 2022). However, other rangelands are experiencing decreased fire frequency, largely caused by reduced fine fuels from anthropogenic-induced alterations to plant community composition or land use. Though longer fire return intervals can also be problematic because they cause undesirable plant community compositional shifts and decreased heterogeneity in some rangelands, this special issue is focused on the problem of more frequent and catastrophic wildfires as this is a more pressing concern in terms of the rate of undesirable ecosystem change and risk to property and life.
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Restoration of the foundational species, big sagebrush (Artemisia tridentata Nutt.), of the sagebrush steppe biome has not kept pace with the loss of habitat, demanding new tools to improve its restoration. Seed enhancement technology (SET) is one approach that is increasingly being tested in native plant restoration as a means to overcome establishment barriers. Like many semiarid shrubs, sagebrush faces establishment barriers from inadequate moisture, competition from faster-growing grasses, and limited available nutrients. We performed a series of laboratory trials testing whether nutrient amendments could be applied to sagebrush seed using a SET to increase root length and biomass, thereby potentially increasing seedling survival. We initially tested 11 amendments applied directly to bare seeds; of these, a high-phosphorus fertilizer resulted in a 2.7x increase in root biomass and 71-mm increase in root length over the control. We then tested incorporating this fertilizer at multiple concentrations into a pellet SET and a ground dust. Although the fertilizer, particularly at higher concentrations, conferred some enhancement to seedling biomass, the pellet treatments had substantially lower emergence and survival than bare seed and dust treatments. These results indicate the potential for a “root-enhancement” SET to benefit sagebrush and other species like it; they also illustrate some of the challenges of SET development for native species. Sagebrush has small seeds that typically need light to germinate. Further work is needed to develop an appropriate technology that does not negatively impact emergence but still provides enough nutrients for enhanced root growth. Field testing is also needed to determine if increases in root growth translate into greater survival. Given the low success rate of sagebrush seeding in restoration projects, however, we suggest that it is worth considering root-enhancement SET alongside other efforts to improve sagebrush establishment success.
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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 tool is designed to rapidly assess and manage perennial and intermittent lotic (flowing) water systems. Lentic, or still-water, systems, such as wet meadows, swales, seeps and marshes, are inherently different.
This guide is not an instruction manual but a decision-support tool for understanding how riparian areas such as creeks, rivers and streams should function. This guide helps managers determine whether a riparian area is functioning properly and how to restore or maintain proper function. A wide variety of natural resource professionals or land managers will find this guide helpful because it provides a framework for land managers to identify, discuss and address threats to riparian resources.
The goals of this tool are:
- Facilitate communication about riparian conditions across a broad audience of stakeholders.
- Provide an assessment that easily integrates with existing protocols and programs.
- Help users identify factors impacting stream resilience.
- Help users assess and prioritize areas that may require more detailed investigation.
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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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n early October 2023, nearly fifty research scientists and technicians collaborating with the USDA Forest Service-sponsored Fire and Smoke Model Evaluation Experiment (FASMEE) gathered on the Fishlake National Forest to collect measurements from a rare stand-replacing prescribed fire. Developing new approaches to predict fire and smoke behavior, scientists representing the USDA Forest Service, the National Aeronautics and Space Administration (NASA), Tall Timbers, Desert Research Institute, and universities from across the country, partnered to collect fire-related data from belowground to space. These synergistic research projects characterized fuels, measured radiant heat and energy, evaluated smoke concentrations, and documented fire effects on vegetation and even bats.
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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.