Liability and Prescribed Fire: Perception and Reality

Changing climate and fuel accumulation are increasing wildfire risks across the western United States. This has led to calls for fire management reform, including the systematic use of prescribed fire. Although use of prescribed fire by private landowners in the southern Great Plains has increased during the past 30 yr, studies have determined that liability concerns are a major reason why many landowners do not use or promote the use of prescribed fire. Generally, perceptions of prescribed fire ? related liability are based on concerns over legal repercussions for escaped fire. This paper reviews the history and current legal liability standards used in the United States for prescribed fire, it examines how perceived and acceptable risk decisions about engagement in prescribed burning and other activities differ, and it presents unanticipated outcomes in two cases of prescribed fire insurance aimed at promoting the use of prescribed fire. We demonstrate that the empirical risk of liability from escaped fires is minimal (< 1%) and that other underlying factors may be leading to landowners’ exaggerated concerns of risk of liability when applying prescribed fire. We conclude that providing liability insurance may not be the most effective approach for increasing the use of prescribed fire by private landowners. Clearly differentiating the risks of applying prescribed fire from those of catastrophic wildfire damages, changing state statutes to reduce legal liability for escaped fire, and expanding landowner membership in prescribed burn associations may be more effective alternatives for attaining this goal. Fear of liability is a major deterrent to the use of prescribed fire; however, an evaluation of the risks from escaped fire does not support perceptions that using prescribed fire as a land management tool is risky. Prescribed burning associations and agencies that support land management improvement have an important role to play in spreading this message.     

Prescribed Fire Effects on Deciduous Oak Woodland Stand Structure,Northern Diablo Range,California

Despite the increasing use of fire in managing oak woodlands, little information exists on quantitative changes to stand structure from prescribed burning. Fire damage and recovery in a mixed deciduous oak woodland were recorded after a prescribed fire on the northern Diablo Range, Santa Clara County, California. Blue oak (Quercus douglasii Hook. & Arn.), valley oak (Q. lobata Nee), and black oak (Q. kelloggii Newb.) trees were monitored for 4 yr to determine the effects of a late spring burn on stand structural characteristics. Fire-caused mortality was low; 4 yr after the low intensity ground fire only four oaks died (1.9%). There were significant differences in mean percent tree crown scorch and mean trunk char height between plots that burned under different fire intensities, but not between tree size classes. Although overall tree damage was low, crown resprouts developed on 80% of the trees and were found as shortly as 2 wk after the fire. Recovery was vigorous; both valley oaks and blue oaks produced crown resprouts on trees with 100% crown scorch. Classification tree analysis identified aspect (mostly southern exposures) and tree size related to the presence of crown resprouting. Crown damage was also an important factor; trees with greater than 40% of their crown scorched resprouted. Fire-induced trunk scars occurred on a small number of trees (9.1%) but was disproportionately higher for black oak compared to blue and valley oak. Stand structural characteristics (species composition, tree density, basal area, and crown closure) were not substantially altered by the event but rather maintained. Prescribed fire might be a viable tool in reducing fuels and maintaining oak woodlands; however, further investigations that include relationships of regeneration with repeated fire are needed.     

Economic and Social Impacts of Wildfires and Invasive Plants in American Deserts: Lessons From the Great Basin

Research on the impacts of wildfire and invasive plants in rangelands has focused on biophysical rather than human dimensions of these environmental processes. We offer a synthetic perspective on economic and social aspects of wildfire and invasive plants in American deserts, focusing on the Great Basin because greater research attention has been given to the effects of cheatgrass expansion than to other desert wildfire/invasion cycles. We focus first on impacts at the level of the individual decision-maker, then on impacts experienced at the human community or larger socio-political scales. Economic impacts of wildfire differ from those of invasive grasses because although fire typically reduces forage availability and thus ranch profit opportunities, invasive grasses can also be used as a forage source and ranchers have adapted their grazing systems to take advantage of that circumstance. To reduce the threat of increased ranch bankruptcies, strategies are needed that can increase access to alternative early-season forage sources and/or promote diversification of ranch income streams by capturing value from ranch ecosystem services other than forage. The growth of low-density, exurban subdivisions in Western deserts influences not only the pattern and frequency of wildfire and plant invasions but also affects prevailing public opinion toward potential management options, and thereby the capacity of land management agencies to use those options. Outreach efforts can influence public opinion, but must be rooted in new knowledge about multiple impacts of invasion and increased wildfire in American deserts.     

Landowner Perceptions of Legal Liability for Using Prescribed Fire in the Southern Plains,United States

Suppression of fire in the Southern Plains has led to proliferation of woody plants and fuel load accumulation that spurs wildfires. These effects have led to calls for widespread application of prescribed fire to reduce fuel loads, but there is substantial landowner resistance to the use of this land management tool. Here we explore factors that affect perceptions of landowners in the Southern Plains about prescribed fire liability and their willingness to apply this land management tool. This region was selected for the study because of the preponderance of private landholdings and widespread woody plant encroachment. The study used a mail survey of 1 853 landowners in 16 counties in Texas and Oklahoma, resulting in a data set from 680 respondents (37% useable response rate). Logistic regression models were developed to test three hypotheses relating to the likelihood that a landowner will apply prescribed fire. The study corroborated that landowners who perceived higher levels of fire-related legal liability were less likely to apply prescribed fire on their land or assist with its application on other properties. In addition, burn bans were found to inhibit landowner willingness to apply fire during periods that result in higher woody plant mortality. Oklahoma respondents, landowners who believed prescribed fire to be an affordable woody plant management tool, and members of prescribed burning associations (PBAs) were more likely to use prescribed fire. These results have important implications for policies aimed at overcoming resistance to the use of prescribed fire to curb woody plant encroachment and reduce fuel load accumulation. Specifically, language in state statutes pertaining to prescribed fire should be modified to reduce landowner concerns over legal liability; PBAs should be established more widely; and public cost-sharing funds for woody plant management should prioritize prescribed fire.     

Influence of Prescribed Fire on Ecosystem Biomass,Carbon, and Nitrogen in a Pinyon Juniper Woodland

Increases in pinyon and juniper woodland cover associated with land-use history are suggested to provide offsets for carbon emissions in arid regions. However, the largest pools of carbon in arid landscapes are typically found in soils, and aboveground biomass cannot be considered long-term storage in fire-prone ecosystems. Also, the objectives of carbon storage may conflict with management for other ecosystem services and fuels reduction. Before appropriate decisions can be made it is necessary to understand the interactions between woodland expansion, management treatments, and carbon retention. We quantified effects of prescribed fire as a fuels reduction and ecosystem maintenance treatment on fuel loads, ecosystem carbon, and nitrogen in a pinyon–juniper woodland in the central Great Basin. We found that plots containing 30% tree cover averaged nearly 40 000 kg · ha^?1 in total aboveground biomass, 80 000 kg · ha^?1 in ecosystem carbon (C), and 5 000 kg · ha^?1 in ecosystem nitrogen (N). Only 25% of ecosystem C and 5% of ecosystem N resided in aboveground biomass pools. Prescribed burning resulted in a 65% reduction in aboveground biomass, a 68% reduction in aboveground C, and a 78% reduction in aboveground N. No statistically significant change in soil or total ecosystem C or N occurred. Prescribed fire was effective at reducing fuels on the landscape and resulted in losses of C and N from aboveground biomass. However, the immediate and long-term effects of burning on soil and total ecosystem C and N is still unclear.     

Integrated Grazing and Prescribed Fire Restoration Strategies in a Mesquite Savanna: II. Fire Behavior and Mesquite Landscape Cover Responses

Prescribed fire is used to reduce the rate of woody plant encroachment in grassland ecosystems. However, fire is challenging to apply in continuously grazed pastures because of the difficulty in accumulating sufficient herbaceous fine fuel for fire. We evaluated the potential of rotationally grazing cattle in fenced paddocks as a means to defer grazing in selected paddocks to provide fine fuel for burning. Canopy cover changes from 1995 to 2000 of the dominant woody plant, honey mesquite (Prosopis glandulosa Torr.), were compared in three landscape-scale grazing and mesquite treatment restoration strategies: 4-paddock, 1-herd with fire (4:1F), 8-paddock, 1-herd with fire (8:1F), and 4:1 with fire or aerial application of 0.28 kg · ha^?1 clopyralid + 0.28 kg · ha^?1 triclopyr herbicide (4:1F/H), and a continuously grazed control with mesquite untreated (CU). Prescribed burning took place in late winter (February–March). Droughts limited burning during the 5-yr period to half the paddocks in the 4:1F and 8:1F strategies, and one paddock in each 4:1F/H strategy. Mesquite cover was measured using digitized aerial images in 1995 (pretreatment) and 2000. Mesquite cover was reduced in all paddocks that received prescribed fire, independent of grazing strategy. Net change in mesquite cover in each strategy, scaled to account for soil types and paddock sizes, was +34%, +15%, +5%, and -41% in the CU, 4:1F, 8:1F, and 4:1F/H strategies, respectively. Thus, rotational grazing and fire strategies slowed the rate of mesquite cover increase but did not reduce it. Fire was more effective in the 8:1F than the 4:1F strategy during drought because a smaller portion of the total management area (12.5% vs. 25%) could be isolated to accumulate fine fuel for fire. Herbaceous fine fuel and relative humidity were the most important factors in determining mesquite top-kill by fire.     

Integrated Grazing and Prescribed Fire Restoration Strategies in a Mesquite Savanna: I. Vegetation Responses

This study evaluated the efficacy of prescribed fire applied within landscape-scale rotational grazing treatments to reduce mesquite (Prosopis glandulosa Torr.) encroachment and restore herbaceous productivity and cover. One-herd, multiple-paddock rotational grazing was used to accumulate herbaceous fine fuel for fires via prefire deferment and to provide periodic postfire deferment for grass recovery. Treatments were an unburned continuous-grazed control, a four-paddock-1 herd system with fire (4:1F), and an eight-paddock-1 herd system with fire (8:1F), with two replicates per treatment (1 294–2 130 ha per replicate). The management plan was to burn 25% of each system (one paddock in the 4:1F; two paddocks in the 8:1F treatments) and defer grazing during all or portions of the 9 mo (May to January) prior to burning. Deferral was “internalized” by grazing on the remaining 75% of each treatment without reducing stocking rate determined for the entire system. Mesquite cover increased on clay-loam soils from 22% to 40% in unburned paddocks over 7 yr (1995–2001). This increase, coupled with extended drought, reduced fine fuel amounts for fire and limited the number and intensity of fires that were applied. It was possible to burn one paddock in the 8:1F treatment (12.5% of total area), but not in the 4:1F treatment (25% of total area) during drought. Fires reduced mesquite and cactus (Opuntia spp.) cover by 25–79% and 24–56%, respectively, but cover of these species increased to prefire levels within 6 yr. All fires reduced (P ≤ 0.05) total herbaceous biomass for 1 yr postfire. The 8:1F treatment increased (P ≤ 0.05) grass biomass on loamy-bottom soils and reduced (P ≤ 0.05) bare ground on clay-loam and loamy-bottom soils in unburned paddocks compared to the unburned continuously grazed control. The 8:1F treatment, through internalized grazing deferment, facilitated the application of fire to reduce woody cover during extended drought without degrading the herbaceous understory.     

Exotic Plant Species Diversity: Influence of Roads and Prescribed Fire in Arizona Ponderosa Pine Forests

Many studies have investigated the ecological effects of roads and roadsides as both habitat and dispersal corridors for exotic plant species. Several of these compared roadside exotic species richness and abundance with adjacent interior habitats, but we found no studies of individual exotic species’ abundance between the two habitats in the context of prescribed fire. We measured exotic species richness and individual species’ abundance along roadsides and in adjacent interior habitat (> 150 m) before and after prescribed fire at three ponderosa pine (Pinus ponderosa Douglas ex Lawson & C. Lawson) sites in northern Arizona. Eighteen of the 20 exotic plant species found in this study have been and continue to be intentionally introduced or are known agricultural seed contaminants. Roadsides had significantly higher exotic species richness than adjacent forest interior habitats, but only one site showed a significant (decreasing) fire effect on species richness. Four exotic plant species had significantly higher densities along roadsides at two of the three sites, and four species had no significant difference in abundance between habitats at any site supporting an individualistic species response hypothesis. Most exotic species showed no significant change in density post-prescribed fire suggesting that low-intensity prescribed fire may have minimal effect on exotic species diversity. Variability in total exotic species richness, composition, species’ constancies, and species’ densities between the three regionally similar sites suggests differing degrees and effectiveness of past management practices and policies such as intentional seeding.     

Acceptance,Acceptability, and Trust for Sagebrush Restoration Options in the Great Basin: A Longitudinal Perspective

In surveys of residents in three urban and three rural locations in the Great Basin we examined the social acceptability of six management practices showing promise for restoring sagebrush-dominated rangelands. Unlike most studies of range management perceptions that have relied on single measurements, we used longitudinal data from a questionnaire mailed in 2006 to residents that were resurveyed in 2010. Overall, 698 respondents comprised the panel. Respondents' self-reported levels of knowledge about the health and management of Great Basin rangelands decreased from 2006 to 2010. In both years, mean acceptance was greater for the use of prescribed fire, grazing, felling, and mowing, but relatively low for chaining and herbicide use. Overall, acceptability ratings were similar in 2006 and 2010 but individually about half of the acceptance responses differed between years. Practices were more acceptable to respondents who expressed greater concern about threats posed by inaction, except that the threat of wildfire was negatively associated with acceptance for prescribed burning. Acceptance was not significantly related to concern about overall health of Great Basin rangelands, or to self-reported knowledge level. Rural/urban residence and general attitudes toward environmental protection were sometimes influential, but more so in 2006 than in 2010. By far the best predictor of acceptance was trust in agencies' ability to implement the practice. In both years respondents were more likely to judge a practice acceptable than to trust agencies to use the practice. Positive or negative change in trust level was the most significant predictor of change in acceptability judgment from 2006 to 2010. Results suggest that efforts to increase acceptance of practices among Great Basin stakeholders should focus on activities designed to build trust rather than simply providing more or better information.     

Postfire Seeding and Plant Community Recovery in the Great Basin

As wildland fire frequency increases around the globe, a better understanding of the patterns of plant community recovery in burned landscapes is needed to improve rehabilitation efforts. We measured establishment of seeded species, colonization of Bromus tectorum and other nonnative annual plants, and recovery of nonseeded native species in topographically distinct areas within five fires that burned Great Basin shrub-steppe communities in Elko County, Nevada. Plant density, frequency, and cover data were collected annually for 4 yr postfire. Vegetation composition varied among flat areas and north- and south-facing aspects, and changed over the course of the sampling period; recovery varied among sites. In general, B. tectorum densities were higher on south aspects, particularly 3 and 4 yr after fire, when densities increased dramatically relative to prefire conditions. Nonseeded native perennial grasses, forbs, and shrubs were abundant in three of the five fire sites, and were more likely to be present on north aspects and flat areas. Over time, nonseeded perennial grass densities remained relatively constant, and nonseeded forbs and shrubs increased. Seeded species were most likely to establish in flat areas, and the density of seeded perennial grasses, forbs, and shrubs decreased over time. Frequency and density measurements were highly correlated, especially for perennial species. Our results emphasize the value of considering site aspect and the potential for native regrowth when planning and monitoring restorations. For example, effective rehabilitation of south aspects may require the development of new restoration methods, whereas north aspects and flat areas in sites with a strong native component were not improved by the addition of seeded species, and may require weed control treatments, rather than reseeding, to improve recovery. Tailoring revegetation objectives, seed mixes, seeding rates, and monitoring efforts to conditions that vary within sites may lead to more cost effective and successful restoration.     

Basalt Milkvetch Responses to Novel Restoration Treatments in the Great Basin

The restoration of native forbs in the Great Basin and similar dryland ecosystems remains a great challenge for land managers. Variable soil water, precocious germination and emergence, and the presence of soil fungal pathogens often reduce plant establishment. Novel restoration treatments that increase soil water during early forb life stages, delay germination and emergence to coincide with favorable spring conditions, and reduce mortality from soil fungal pathogens may benefit native forb restoration. We compared the efficacy of three novel treatments—snow fencing, plant protection fabric, and seed coatings—to improve establishment of a forb species native to the Great Basin, basalt milkvetch (Astragalus filipes Torr. ex A. Gray). We replicated treatments plus a no-treatment control at three sites in the Great Basin in a randomized complete block design over 2 yr. To evaluate the efficacy of our restoration treatments, we measured germination, seedling emergence, establishment, and second-yr survival. The effects of snow fencing and plant protection fabric varied by site and life stage and were likely influenced by the wet spring conditions across sites, particularly the two northern sites. Snow fencing increased establishment and second-yr survival at one site. Plant protection fabric did not benefit any life stage at any site. Seed coatings increased seedling emergence at all sites but did not affect establishment or survival. Overall, second-yr survival remained low across all sites and treatments. Our study indicates that our treatments can positively affect basalt milkvetch emergence, establishment, and survival, but additional management actions are needed to improve long-term restoration success of native forbs.     

Homogenization of the Soil Surface Following Fire in Semiarid Grasslands

Semiarid grasslands accumulate soil beneath plant “islands” that are raised above bare interspaces. This fine-scale variation in microtopographic relief is plant-induced and is increased with shrub establishment. Research found that fire-induced water repellency enhanced local-scale soil erosion that reduced variation in microtopographic relief, suggesting that fire may counteract vegetation-driven, fine-scale spatial soil heterogeneity. This article analyzes longer-term measurements (up to 9 yr) of soil microtopography to evaluate the hypothesis that fire in semiarid grasslands results in more homogenous soil microtopographic relief. Changes in soil microtopographic relief were measured prior to and following a total of five fires at three semiarid grasslands within central New Mexico, United States. The fires included three cool-season prescribed fires, a warm-season prescribed fire, and a warm-season wildfire. Four of the five fires resulted in significantly lower soil microtopographic variation that persisted for up to 4 yr. The duration and magnitude of the soil leveling effect was lowest in the grassland with clay-rich soils, indicating a possible soil texture interaction. Although two grasslands had net soil loss following fires, no net erosion occurred at the third grassland, indicating that redistribution of soils can occur without net erosion. These results show that management with prescribed fire reduces biotic-driven variation in soil microtopographic relief in semiarid grasslands that may help limit the transition to shrubland ecosystems in this region.     

Flavobacterium psychrophilum Infections in Salmonid Broodstock and Hatchery-Propagated Stocks of the Great Lakes Basin

Bacterial coldwater disease (BCWD), caused by Flavobacterium psychrophilum, threatens wild and propagated salmonids worldwide and leads to substantial economic losses. In addition to being horizontally transmitted, F. psychrophilum can be passed from infected parents to their progeny, furthering the negative impacts of this pathogen. In Michigan, both feral and captive salmonid broodstocks are the gamete sources used in fishery propagation efforts. A 5-year study was initiated to follow the prevalence of systemic F. psychrophilum infections in feral broodstocks of four species (steelhead Oncorhynchus mykiss [potadromous Rainbow Trout]; Coho Salmon O. kisutch; Chinook Salmon O. tshawytscha; and Atlantic Salmon Salmo salar) residing in three Great Lakes watersheds. Additionally, captive broodstocks of four species (Rainbow Trout, Brown Trout Salmo trutta, Lake Trout Salvelinus namaycush, and Brook Trout Salvelinus fontinalis) maintained at two facilities were assessed for the presence of F. psychrophilum. The resultant offspring from each broodstock population were sampled for F. psychrophilum infections multiple times throughout hatchery residency. Using selective flavobacterial culture and PCR confirmation, F. psychrophilum was detected in all broodstocks except the captive Lake Trout and Brook Trout. Logistic regression analysis demonstrated that among the infected feral broodstocks, Chinook Salmon from the Lake Michigan watershed had the highest prevalence of systemic F. psychrophilum infection (mean = 63.2%). Among the captive broodstocks, the Gilchrist Creek strain of Brown Trout had the highest infection prevalence (mean = 5%). Collectively, the captive broodstocks were found to have significantly lower infection prevalence than the feral broodstocks. Despite the high prevalence of systemic F. psychrophilum infections in many broodstock populations, the bacterium was rarely detected in their progeny during hatchery rearing. However, heavy losses associated with clinical BCWD outbreaks did occur. Collectively, our results reinforce that BCWD continues to threaten Great Lakes basin salmonids.

Received April 6, 2015; accepted August 25, 2015     

锡林河流域栗钙土及其物理性状与水分动态的研究

锡林河流域栗钙土具有典型的草原土壤特征.土壤水分是生产力主要的制约因素,水分状况受到天然降水及土壤性状的影响,水分特征曲线研究表明,土壤持水力与质地及有机质含量有密切关系,水分有效性主要取决于土壤含水量及释水性.土壤水分动态有明显的阶段性变化规律.地形、母质、地表状况、质地及剖面特征决定了水分空间变异情况,长期低水平的水分循环是栗钙土生产力不高、不稳的主要原因.     

Interactions Between Soil Erosion Processes and Fires: Implications for the Dynamics of Fertility Islands

Shrub encroachment in arid and semiarid rangelands, a worldwide phenomenon, results in a heterogeneous landscape characterized by a mosaic of nutrient-depleted barren soil bordered by nutrient-enriched shrubby areas known as “fertile islands.” Even though shrub encroachment is considered as a major contributor to rangeland degradation, little is known about mechanisms favoring the reversibility of the early stages of this process. Here we synthesize the interactions between fires and soil erosion processes, and the implications of these interactions for management of rangelands. The burning of shrub vegetation develops relatively high levels of soil hydrophobicity. This fire-induced water repellency was shown to enhance the soil erodibility in and around burned shrub patches. The fire-induced enhancement of local-scale soil erosion results from changes in the interparticle bonding forces between the soil grains, thus altering the way moisture is retained in the soil. It has been shown—with a number of wind-tunnel studies, field-scale manipulative experiments, microtopographic measurements, and isotopic tracer studies—how the fire-erosion interactions affect the dynamics of fertility islands. Further we propose a new conceptual model of resource “island” dynamics that explains some of the findings previously reported in the literature on the interactions between aeolian processes and arid-land vegetation. In particular, we highlight the ability of fires to enhance the erodibility of nutrient-rich soils accumulated under the shrubs favoring the redistribution of soil resources, thereby contributing to the reversibility of the early stages of shrub encroachment.     

Short-Term Response of Sage-Grouse Nesting to Conifer Removal in the Northern Great Basin

Conifer woodlands expanding into sage-steppe (Artemisia spp.) are a threat to sagebrush obligate species including the imperiled greater sage-grouse (Centrocercus urophasianus). Conifer removal is accelerating rapidly despite a lack of empirical evidence to assess outcomes to grouse. Using a before-after-control-impact design, we evaluated short-term effects of conifer removal on nesting habitat use by monitoring 262 sage-grouse nests in the northern Great Basin during 2010–2014. Tree removal made available for nesting an additional 28% of the treatment landscape by expanding habitat an estimated 9603 ha (3201 ha [± 480 SE] annually). Relative probability of nesting in newly restored sites increased by 22% annually, and females were 43% more likely to nest within 1000 m of treatments. From 2011 (pretreatment) to 2014 (3 yr after treatments began), 29% of the marked population (9.5% [± 1.2 SE] annually) had shifted its nesting activities into mountain big sagebrush habitats that were cleared of encroaching conifer. Grouping treatments likely contributed to beneficial outcomes for grouse as individual removal projects averaged just 87 ha in size but cumulatively covered a fifth of the study area. Collaboratively identifying future priority watersheds and implementing treatments across public and private ownerships is vital to effectively restore the sage-steppe ecosystem for nesting sage-grouse.     

Encounters with Pinyon-Juniper Influence Riskier Movements in Greater Sage-Grouse Across the Great Basin

Fine-scale spatiotemporal studies can better identify relationships between individual survival and habitat fragmentation so that mechanistic interpretations can be made at the population level. Recent advances in Global Positioning System (GPS) technology and statistical models capable of deconstructing high-frequency location data have facilitated interpretation of animal movement within a behaviorally mechanistic framework. Habitat fragmentation due to singleleaf pinyon (Pinus monophylla; hereafter pinyon) and Utah juniper (Juniperus osteosperma; hereafter juniper) encroachment into sagebrush (Artemisia spp.) communities is a commonly implicated perturbation that can adversely influence greater sage-grouse (Centrocercus urophasianus; hereafter sage-grouse) demographic rates. Using an extensive GPS data set (233 birds and 282,954 locations) across 12 study sites within the Great Basin, we conducted a behavioral change point analysis and constructed Brownian bridge movement models from each behaviorally homogenous section. We found the probability of encountering pinyon-juniper among adults was two and three times greater than that of yearlings and juveniles, respectively. However, the movement rate in response to the probability of encountering pinyon-juniper trees was 1.5 times greater for juveniles. Parameter estimates indicated a 6.1% increase in the probability of encountering pinyon-juniper coupled with a 6.2 km/hour increase in movement speed resulted in a 56%, 42% and 16% increase in risk of daily mortality, for juveniles, yearlings, and adults, respectively. The effect of pinyon-juniper encounters on survival was dependent on movement rate and differed among age class. Under fast speed movements (i.e., flight), mortality risk increased as encountering pinyon-juniper increased across all age classes. In contrast, slower speeds (i.e., average) yielded similar adverse effects for juveniles and yearlings but not for adults. This analytical framework supports a behavioral mechanism that explains reduced survival related to pinyon-juniper within sagebrush environments, whereby encountering pinyon-juniper stimulates riskier movements that likely increase vulnerability to visually acute predators.     

Vegetation Characteristics of Mountain and Wyoming Big Sagebrush Plant Communities in the Northern Great Basin

Dominant plant species are often used as indicators of site potential in forest and rangelands. However, subspecies of dominant vegetation often indicate different site characteristics and, therefore, may be more useful indicators of plant community potential and provide more precise information for management. Big sagebrush (Artemisia tridentata Nutt.) occurs across large expanses of the western United States. Common subspecies of big sagebrush have considerable variation in the types of sites they occupy, but information that quantifies differences in their vegetation characteristics is lacking. Consequently, wildlife and land management guidelines frequently do not differentiate between subspecies of big sagebrush. To quantify vegetation characteristics between two common subspecies of big sagebrush, we sampled 106 intact big sagebrush plant communities. Half of the sampled plant communities were Wyoming big sagebrush (A. tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh) plant communities, and the other half were mountain big sagebrush (A. tridentata subsp. vaseyana [Rydb.] Beetle) plant communities. In general, mountain big sagebrush plant communities were more diverse and had greater vegetation cover, density, and biomass production than Wyoming big sagebrush plant communities. Sagebrush cover was, on average, 2.4-fold higher in mountain big sagebrush plant communities. Perennial forb density and cover were 3.8- and 5.6-fold greater in mountain compared to Wyoming big sagebrush plant communities. Total herbaceous biomass production was approximately twofold greater in mountain than Wyoming big sagebrush plant communities. The results of this study suggest that management guidelines for grazing, wildlife habitat, and other uses should recognize widespread subspecies as indicators of differences in site potentials.