Response of Conifer-Encroached Shrublands in the Great Basin to Prescribed Fire and Mechanical Treatments

In response to the recent expansion of piñon and juniper woodlands into sagebrush-steppe communities in the northern Great Basin region, numerous conifer-removal projects have been implemented, primarily to release understory vegetation at sites having a wide range of environmental conditions. Responses to these treatments have varied from successful restoration of native plant communities to complete conversion to nonnative invasive species. To evaluate the general response of understory vegetation to tree canopy removal in conifer-encroached shrublands, we set up a region-wide study that measured treatment-induced changes in understory cover and density. Eleven study sites located across four states in the Great Basin were established as statistical replicate blocks, each containing fire, mechanical, and control treatments. Different cover groups were measured prior to and during the first 3 yr following treatment. There was a general pattern of response across the wide range of site conditions. There was an immediate increase in bare ground and decrease in tall perennial grasses following the fire treatment, but both recovered by the second or third growing season after treatment. Tall perennial grass cover increased in the mechanical treatment in the second and third year, and in the fire treatment cover was higher than the control by year 3. Nonnative grass and forb cover did not increase in the fire and mechanical treatments in the first year but increased in the second and third years. Perennial forb cover increased in both the fire and mechanical treatments. The recovery of herbaceous cover groups was from increased growth of residual vegetation, not density. Sagebrush declined in the fire treatment, but seedling density increased in both treatments. Biological soil crust declined in the fire treatment, with no indications of recovery. Differences in plant response that occurred between mechanical and fire treatments should be considered when selecting management options.     

Prescribed Fire Effects on Rangeland Dung Beetles (Coleoptera: Scarabaeinae,Aphodiinae) in the Southern Great Plains

Rangeland dung beetles represent an important assemblage of insects for the Great Plains. In this study, we examine the effects of a postfire rangeland environment on a dung beetle assemblage in north-central Texas. We deployed baited pitfall traps to examine spring prescribed fire treatment, differences in vegetation visual obstruction, and dung density influence on dung beetle abundance and community composition. Using model-based multivariate methods, we did not find an influence of prescribed burning on the dung beetle assemblage. We report a negative influence of vegetation visual obstruction and no significant influence of dung density on dung beetle assemblages. These results suggest that prescribed fire may not negatively affect dung beetle species within the North American Great Plains; however, vegetation structure correlated to postfire rangeland environments may influence local beetle abundance.     

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,Grazing, and Herbaceous Plant Production in Shortgrass Steppe

We examined the independent and combined effects of prescribed fire and livestock grazing on herbaceous plant production in shortgrass steppe of northeastern Colorado in the North American Great Plains. Burning was implemented in March, before the onset of the growing season. During the first postburn growing season, burning had no influence on soil moisture, nor did it affect soil nitrogen (N) availability in spring (April–May), but it significantly enhanced soil N availability in summer (June–July). Burning had no influence on herbaceous plant production in the first postburn growing season but enhanced in vitro dry matter digestibility of blue grama (Bouteloua gracilis [Willd. ex Kunth] Lag. ex Griffiths) forage sampled in late May. For the second postburn growing season, we found no difference in herbaceous plant production between sites that were burned and grazed in the previous year versus sites that were burned and protected from grazing in the previous year. Our results provide further evidence that prescribed burns conducted in late winter in dormant vegetation can have neutral or positive consequences for livestock production because of a neutral effect on forage quantity and a short-term enhancement of forage quality. In addition, our results indicate that with conservative stocking rates, deferment of grazing during the first postburn growing season may not be necessary to sustain plant productivity.     

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.     

Plant Community and Soil Environment Response to Summer Fire in the Northern Great Plains

Fire is an important process in many ecosystems, especially grasslands. However, documentation of plant community and soil environment responses to fire is limited for semiarid grasslands relative to that for mesic grasslands. Replicated summer fire research is lacking but necessary because summer is the natural fire season and the period of most wildfires in the western United States. We evaluated summer fire effects on soil temperature, soil moisture, aboveground biomass, root biomass, and functional group composition for 2 yr in semiarid C₃-dominated northern Great Plains. Following pre-treatment measures, four 0.75-ha sites were burned during August for comparison with nonburned sites, and the experiment was repeated the next year on adjacent sites to assess weather effects. Soils were about 0.5°C cooler on burned sites in the first experiment and similar in the second. Burned sites were consistently 1% drier than nonburned sites. Litter was reduced by fire but did not account for changes in soil moisture because differences occurred before the growing season. Current-year aboveground biomass and root biomass were similar between treatments, indicating productivity was resistant to summer fire. Perennial C₃ grasses increased in dominance because of positive biomass responses to fire for all but the bunchgrass, Hesperostipa comata, and a reduction of annual grasses. Perennial C₄ grasses were unaffected by summer fire. H. comata was resilient, with biomass on burned sites equaling nonburned sites the second growing season. Biomass was more responsive to precipitation than fire, and the fire-induced changes in species composition suggest exclusion of fire may be a greater disturbance than summer fire.     

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.     

Absence of a Grass/Fire Cycle in a Semiarid Grassland: Response to Prescribed Fire and Grazing

Many nonnative invasive grasses alter fire regimes to their own benefit and the detriment of native organisms. In southern Arizona the nonnative Lehmann lovegrass (Eragrostis lehmanniana Nees) dominates many semiarid grasslands where native grasses were abundant. Managers are wary of using prescribed fire in this fire-prone community partly due to the perceived effects of a grass/fire cycle. However, examples of the grass/fire cycle originate in ecosystems where native plants are less fire-tolerant than grasses and the invasive plant does not mimic the physiognomy of the native community. We investigate the effects of prescribed fire and livestock grazing on a semiarid grassland community dominated by a nonnative invasive grass. Lehmann lovegrass does not appear to alter the fire regime of semiarid grasslands to the detriment of native plants. Prescribed fire reduced the abundance of Lehmann lovegrass for 1 to 2 yr while increasing abundance of native grasses, herbaceous dicotyledons and fall richness, and diversity. Effects of livestock grazing were less transformative than the effects of fire in this long-grazed area, but grazing negatively affected native plants as did the combination of prescribed fire and livestock grazing. Although Lehmann lovegrass produces more fuel than native plants, fire frequency in semiarid grasslands appears to be limited by the paucity of above-average precipitation, which constrains high fuel loads. In addition, many native grasses tolerate high temperatures produced by Lehmann lovegrass fires. Consistent with previous research, fire does not promote the spread of Lehmann lovegrass, and more importantly human alteration of the fire regime is greater than the nominal effects of Lehmann lovegrass introduction on the fire regime.     

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.     

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.     

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.     

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.     

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.     

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.