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Extreme wildfires are increasing in frequency globally, prompting new efforts to mitigate risk. The ecological appropriateness of risk mitigation strategies, however, depends on what factors are driving these increases. While regional syntheses attribute increases in fire activity to both climate change and fuel accumulation through fire exclusion, they have not disaggregated causal drivers at scales where land management is implemented. Recent advances in fire regime modeling can help us understand which drivers dominate at management-relevant scales. We conducted fire regime simulations using historical climate and fire exclusion scenarios across two watersheds in the Inland Northwestern U.S., which occur at different positions along an aridity continuum. In one watershed, climate change was the key driver increasing burn probability and the frequency of large fires; in the other, fire exclusion dominated in some locations. We also demonstrate that some areas become more fuel-limited as fire-season aridity increases due to climate change. Thus, even within watersheds, fuel management must be spatially and temporally explicit to optimize effectiveness. To guide management, we show that spatial estimates of soil aridity (or temporally averaged soil moisture) can provide a relatively simple, first-order indicator of where in a watershed fire regime is climate vs. fuel-limited and where fire regimes are most vulnerable to change.
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The Sagebrush Treatment Evaluation Project (SageSTEP) evaluated the ecological effects of prescribed fire and cut‐and‐leave treatments in sagebrush communities experiencing tree expansion in North American cold desert shrublands. We used 10 yr of data from the SageSTEP network to test how treatments interacted with pre‐treatment tree dominance, soil climate, and time since treatment to affect plant functional groups and dominant species. Non‐sprouting shrub (Artemisia spp.), sprouting shrub, perennial graminoid, and annual grass responses depended on tree dominance and soil climate, and responses were related to the dominant species’ life‐history traits. Sites with warm and dry soils showed increased perennial graminoid but reduced Artemisia shrub cover across the tree dominance gradient after prescribed burning, while sites with cool and moist soils showed favorable post‐burn responses for both functional types, particularly at low to moderate tree dominance. Cut‐and‐leave treatments sustained or increased native perennial plant functional groups and experienced smaller increases in exotic annual plants in both soil climates across the tree dominance gradient. Both treatments reduced biocrust cover. Selecting appropriate tree‐reduction treatments to achieve desired long‐term outcomes requires consideration of dominant species, site environmental conditions, and the degree of woodland expansion. Careful selection of management treatments will reduce the likelihood of undesirable consequences to the ecosystem.
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We used a common garden study to quantify variation in growth and drought resistance traits in 99 populations of Elymus elymoides from a broad geographic and climatic range in the western United States. Ecotypes from drier sites produced less biomass and smaller seeds, and had traits associated with greater drought resistance: small leaves with low osmotic potential and high integrated water use efficiency (δ13C). Seasonality also influenced plant traits. Plants from regions with relatively warm, wet summers had large seeds, large leaves, and low δ13C. Irrespective of climate, we also observed trade‐offs between biomass production and drought resistance traits. Together, these results suggest that much of the phenotypic variation among E. elymoides ecotypes represents local adaptation to differences in the amount and timing of water availability. In addition, ecotypes that grow rapidly may be less able to persist under dry conditions. Land managers may be able to use this variation to improve restoration success by seeding ecotypes with multiple drought resistance traits in areas with lower precipitation. The future success of this common rangeland species will likely depend on the use of tools such as seed transfer zones to match local variation in growth and drought resistance to predicted climatic conditions.
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Urban populations rely on a suite of ecosystem services generally provided by the ecological function of natural areas. But the expansion of urban environments and growing suburban or exurban neighborhoods often necessitates destruction of those natural areas for development supporting a growing urban populace. Ecological impacts from development reduce regional biodiversity and negatively affect the ability of remaining natural areas to provide goods and services critical to people. Secondary impacts to biodiversity also occur at broad geographic scales through commodity production supporting urban centers. For example, agricultural production often involves creating agroeconomic systems based largely on farming a limited number of species, and commonly relegates biological diversity to small patches of land deemed unsuitable for crops. Such practices exacerbate the negative biological effects inherent in urban development and drastically increase the need for urban populations to address biological diversity within municipalities. Residents are becoming progressively knowledgeable about environmental issues and are expressing values and concerns to local and regional managing agencies. Governments are responding to public pressure through recommendations intended to reduce resource use, improve wildlife habitat, and provide a local aesthetic. Although the appropriateness of native plants in urban settings is often questioned, the use of regionally specific native vegetation is identified as one method to meet those recommendations. Native plants as primary landscape elements have the added benefit of increasing biodiversity and creating environments capable of providing ecosystem goods and services within urban environments.
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Wildfires, especially those that impact WUI communities, are driven by multiple factors interacting together that can determine the fire’s intensity and severity, including topography, wind, drought, relative humidity, and the condition and type of local vegetation. The behavior of larger wildfires can additionally be influenced by the weather systems they create, such as fire whirls and pyrocumulonimbus clouds.
Home survivability can be influenced by their construction materials, proximity to other structures and how these neighboring structures are maintained. Overall layout of the property, including landscape design and if materials are stored within proximity of buildings, can also have an impact.
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Our research was guided by the general question, does a near-miss wildfire influence residents’ perceptions and self-reported fire risk mitigation behaviors? Specifically, we examined the cognitive appraisals and physical risk factors influencing residents’ previous and planned mitigation actions both before and after the fire. Our findings show risk perceptions declined significantly after the fire while residents’ intentions to take nine different fire risk mitigation actions increased. These results suggest near-miss fire events result in simultaneous “let-downs” and “wake-up calls” among affected residents. Near-miss wildfires present a unique opportunity for wildfire community preparedness, outreach, and engagement programs to capitalize on an increased willingness to take risk mitigation actions. However, these programs may face difficulties in communicating the continued threat of subsequent fire events.
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The actions of residents in the wildland–urban interface can influence the private and social costs of wildfire. Wildfire programs that encourage residents to take action are often delivered without evidence of effects on behavior. Research from the field of behavioral science shows that simple, often low-cost changes to program design and delivery can influence socially desirable behaviors. In this research report, we highlight how behavioral science and experimental design may advance efforts to increase wildfire risk mitigation on private property. We offer an example in which we tested changes in outreach messaging on property owners’ interest in wildfire risk
information. In partnership with a regional wildfire organization, we mailed 4564 letters directing property owners to visit personalized wildfire risk webpages. By tracking visitation, we observed that 590 letter recipients (12%) sought information about their wildfire risk and response varied by community. This research–practice collaboration has three benefits: innovation in outreach, evidence of innovation through experimental design, and real impacts on interest in wildfire mitigation among property owners. Future collaborations may inform behavioral and evidence-based programs to better serve residents and the public interest as the risks from wildfires are projected to grow.
National and regional preparedness level (PL) designations support decisions about wildfire risk management. Such decisions occur across the fire season and influence pre-positioning of resources in areas of greatest fire potential, recall of personnel from off-duty status, requests for back-up resources from other areas, responses to requests to share resources with other regions during fire events, and decisions about fuel treatment and risk reduction, such as prescribed burning. In this paper, we assess the association between PLs assigned at national and regional (Northwest) scales and a set of predictors including meteorological and climate variables, wildfire activity and the mobilisation and allocation levels of fire suppression resources. To better understand the implicit weighting applied to these factors in setting PLs, we discern the qualitative and quantitative factors associated with PL designations by statistical analysis of the historical record of PLs across a range of conditions. Our analysis constitutes an important step towards efforts to forecast PLs and to support the future projection and anticipation of firefighting resource demand, thereby aiding wildfire risk management, planning and preparedness.
National monitoring of forestlands and the processes causing canopy cover loss, be they abrupt or gradual, partial or stand clearing, temporary (disturbance) or persisting (deforestation), are necessary at fine scales to inform management, science and policy. This study utilizes the Landsat archive and an ensemble of disturbance algorithms to produce maps attributing event type and timing to > 258 million ha of contiguous Unites States forested ecosystems (1986-2010). Nationally, 75.95 million forest ha (759,531 km2) experienced change, with 80.6% attributed to removals, 12.4% to wildfire, 4.7% to stress and 2.2% to conversion. Between regions, the relative amounts and rates of removals, wildfire, stress and conversion varied substantially. The removal class had 82.3% (0.01 S.E.) user’s and 72.2% (0.02 S.E.) producer’s accuracy. A survey of available national attribution datasets, from the data user’s perspective, of scale, relevant processes and ecological depth suggests knowledge gaps remain.
A climatic dipole drives short- and long-term patterns of postfire forest recovery in the western US
Here, we identify a north–south dipole in annual climatic moisture deficit anomalies across the Interior West of the US and characterize its influence on forest recovery from fire. We use annually resolved establishment models from dendrochronological records to correlate this climatic dipole with short-term postfire juvenile recruitment. We also examine longer-term recovery trajectories using Forest Inventory and Analysis data from 989 burned plots. We show that annual postfire ponderosa pine recruitment probabilities in the northern Rocky Mountains (NR) and the southwestern US (SW) track the strength of the dipole, while declining overall due to increasing aridity. This indicates that divergent recovery trajectories may be triggered concurrently across large spatial scales: favorable conditions in the SW can correspond to drought in the NR that inhibits ponderosa pine establishment, and vice versa. The imprint of this climatic dipole is manifest for years postfire, as evidenced by dampened long-term likelihoods of juvenile ponderosa pine presence in areas that experienced postfire drought. These findings underscore the importance of climatic variability at multiple spatiotemporal scales in driving cross-regional patterns of forest recovery and have implications for understanding ecosystem transformations and species range dynamics under global change.