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This study found that Potential Wildfire Operational Delineations (PODs) were helpful for validating fuels treatment plans and supporting communication among agency staff, and with private landowners and collaborators. Challenges included lack of technical knowledge and skills, unclear leadership direction, potential misalignment with other forest management goals and community and agency buy-in to using PODs.
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Invasion by nonnative annual plants that form prolific seed banks, including cheatgrass, throughout western North America is a major natural resource concern. Even with known economic and ecological implications, soil seed banks and their potential to impact ecological restoration in arid and semiarid ecosystems are poorly understood. Quantifying the regenerative potential of the soil seed bank—the living seeds in the soil profile and on the soil surface—can help natural resource managers make decisions to increase the likelihood of restoration success. We analyzed the germinable soil seed bank composition and distribution of a rangeland site in western Colorado that experienced a wildfire in 1994 and is dominated by cheatgrass. We collected soil seed bank samples from 118 points in a 100 × 110 m grid to a depth of 5 cm. Each sample was split by depth from 0 to 2 cm and from 2 to 5 cm, and the seed bank was quantified using greenhouse emergence methods. We found that seeds of native species were more dense and evenly distributed (3391 seeds ⋅ m−2than seeds of nonnative species were (1880 seeds ⋅ m−2) in the 0–5 cm seed bank across the site. We also found that seeds of both native and nonnative species were concentrated in the 0–2 cm layer of the seed bank but that native and nonnative seeds were present in substantive densities in the 2–5 cm layer. These findings suggest that the soil seed bank of the site is resilient, and a targeted approach to specifically deplete the seed bank of nonnative annuals could facilitate restoration by the in situ native seed bank.
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The invasive annual grass, medusahead, infests rangelands throughout the West, from the Columbia Plateau to the California Annual Grasslands and the Great Basin. Dominating secondary succession in the sagebrush steppe, medusahead can degrade the habitat of threatened species such as the greater sage-grouse. This research explores the potential of dormant season grazing as an applied management strategy to reduce the negative impacts of medusahead while promoting recovery of perennial vegetation at the landscape scale. In particular, it assessed grazing with four treatments from 2018 to 2020: traditional grazing (May–October), dormant season grazing (October–February), traditional + dormant season grazing (May–February), and no grazing. After 2 yr of grazing treatments, biomass, density, cover, and fuel continuity did not differ between treatments (P > 0.05). However, biomass measurements were significantly different between years, which is likely due to greater than normal precipitation in 2019 and 2020. Between 2018 and 2019, annual grass biomass increased by 81% (666–1 212 kg ha−1) and perennial grass biomass increased by 165% (118–313 kg ha−1). Litter biomass decreased by approximately 15% in every year since 2018 (2 374, 2 012, and 1 678 kg ha−1 in 2018–2020). There were not significant differences in cover or density of annual and perennial grasses between treatments and years. Our results indicate that 2 yr may not be adequate time for dormant season grazing treatments to be effective in reducing the abundance of medusahead and that after 2 yr of treatments, dormant season grazing does not have a detrimental effect on perennial vegetation.
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Rangelands are often ignored in the discussion of using management to sequester carbon; however, demonstrating that carbon storage could be paid by carbon credit markets would be a significant advancement for rangeland conservation. The additional amount and cost of carbon sequestered was quantified by simulating seeding perennial grass and shrub species in sagebrush shrublands dominated by non-native annual grass and forb species (NNAGF) compared with doing nothing in a 485 623 km² area of interest (AOI) centered around Nevada, United States.
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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.