Veld burning in giant's castle game reserve,natal Drakensberg

A basic aim in the management of a wildlife reserve is to maintain ecological diversity. In the Giant's Castle Game Reserve the vegetation is largely composed of fire sub‐climax grasslands. Under the natural fire‐regime, before man influenced the system much, fires probably occurred at any time of the year, but mostly in summer. At present there are acute problems in controlling wildfires which occur mostly in late winter when there is an extreme fire hazard. Most of the Natal Drakensberg is now burnt by wildfires in late winter and deliberate fires in early spring. The ecological effect of the natural and present fire regimes are discussed, and a burning plan for Giant's Castle is outlined.     

The long-term effect of fire and grazing by wildlife on range condition in moist and arid savannas in the Kruger National Park

Few assessments of the effects of fire and grazing on the herbaceous components of savannas have been reported for Africa. In the Kruger National Park, South Africa, range condition was monitored at three savanna sites spanning a rainfall gradient of 450 to 700 mm and subject to grazing by wildlife. The sites were burnt at 1-, 2- and 3-year intervals, in different seasons and included a control treatment excluding fire for >40 years. Initial surveys of the herbaceous vegetation were conducted between 1954 and 1957 and repeated between 1998 and 2001. Grass species were categorised as either decreaser or increaser species, which decline or increase with over- or under-utilisation, respectively, and their potential to provide forage and fuel for fires indicative of range condition were derived. Range condition improved with regular burning in the moist sites, but deteriorated in the arid sites over all seasons and frequencies of burning. It is concluded that the current homogenous approach to burning across the Park needs to be adapted by reducing the frequency of fires at more arid sites and can be achieved by burning according to the proportions of decreaser and increaser species reflecting the ecological status of the herbaceous vegetation.     

Long-Term Vegetation Recovery and Invasive Annual Suppression in Native and Introduced Postfire Seeding Treatments

Seed mixes used for postfire seeding in the Great Basin are often selected on the basis of short-term rehabilitation objectives, such as ability to rapidly establish and suppress invasive exotic annuals (e.g., cheatgrass, Bromus tectorum L.). Longer-term considerations are also important, including whether seeded plants persist, continue to suppress invasives, and promote recovery of desired vegetation. To better understand long-term effects of postfire seed mixes, we revisited study sites in Tintic Valley, Utah, where seeding experiments had been initiated after the 1999 Railroad wildfire. Four different mixes, including two comprised entirely of native species, had been applied using rangeland drills at a shrubland site and aerial seeding followed by one-way Ely chaining at a woodland site. New vegetation data collected 16 years post fire revealed changes relative to 3 years post fire. We found significant increases in total cover of seed-mix species in all treatments, including the unseeded control where these species were present as residual populations or had spread from seeded treatments. Significant increases of seed-mix species cover and density were observed in blocks where seeding treatments had previously been considered unsuccessful. Some seed-mix species, particularly rhizomatous grasses, increased while others declined. Exotic annual forb cover decreased in all treatments while cheatgrass increased in the unseeded control and to a lesser extent in the native-only seeded treatments. Recruitment of non-seed-mix native perennials was highest in the unseeded control. Results indicate that postfire seeding has lasting effects on vegetation composition and structure, implying that seed mixes should be carefully formulated to promote long-term management objectives. Seed mixes containing large amounts of competitive introduced species may be especially effective for long-term cheatgrass suppression, but native-only mixes can also serve this purpose to a lesser degree while avoiding drawbacks of non-native species introductions.     

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.     

Effects of a fast-burning spring fire on the ground-dwelling spider assemblages (Arachnida: Araneae) in a central South African grassland habitat

Fire is widely used as a management strategy in grasslands to maintain vegetation structure and improve grazing quality for large herbivores. The impacts of burning on invertebrates in South Africa remain poorly understood. A study was initiated in spring 2005 to determine the impact of a fast hot burn on ground-dwelling spider assemblages in a grassland habitat in the central Free State. Pitfall traps were set out at six sites in the reserve, with three sites each in the burnt and unburnt areas, to sample spiders over a 12-month period. A total of 5 253 spiders were collected, representing 33 families and 120 species. Spider abundance was significantly lower in the burnt (n = 1 956) than unburnt sites (n = 3 297), and burnt sites had, on average, considerably fewer species than unburnt sites. The dominant families in the burnt sites were Lycosidae (29.5%), Gnaphosidae (16.9%), Ammoxenidae (9.6%) and Zodariidae (5.7%), whereas Ammoxenidae (22.7%), Lycosidae (20.6%), Gnaphosidae (15.3%) and Amaurobiidae (10.2%) dominated the unburnt sites. Of the nine most abundant families collected, only Caponiidae were more abundant in the burnt than unburnt sites. Our data suggest that fast-burning hot spring fires cause a considerable initial post-fire decline in spider abundance, and have a negative influence on the abundance as well as the resistance of assemblages to disturbances other than fire (e.g. rain). However, most of the dominant families had abundances comparable to unburnt areas within a year post-burn.     

冬季火烧对青藏高原亚高山草甸草地地上生产力和植物群落的影响

以2010年1月21日发生于青藏高原亚高山草甸草地火灾的过火草地为对象,通过对比2010年生长季火烧与未火烧草地生产力及植物群落的变化,发现火烧后第1年草地生产力有不同程度提高,以高寒灌丛草甸线叶嵩草+发草+苔草草地增产影响最大(P0.05)。火烧对植物群落中的种类成分没有明显影响,但在各火烧草地牧草经济类群中,以占优势的莎草科植物呈现出明显的增产效果(P0.05),说明火烧对根茎型莎草科植物起着刺激生长的作用。群落中禾本科植物产草量均有较大幅度下降(P0.05),表明火烧对根茎型禾本科高草的叶层高度有明显的抑制。火烧对各类草地植物生长期产生不同的影响,牧草返青期提前15~25d,生长期延长。     

A 40-Year Record of Tree Establishment Following Chaining and Prescribed Fire Treatments in Singleleaf Pinyon (Pinus monophylla) and Utah Juniper (Juniperus osteosperma) Woodlands

Chaining and prescribed fire treatments have been widely applied throughout pinyon–juniper woodlands of the western United States in an effort to reduce tree cover and stimulate understory growth. Our objective was to quantify effects of treatment on woodland recovery rate and structure and the relative dominance of the two major tree species in our Great Basin study area, singleleaf pinyon (Pinus monophylla Torr. & Frém.) and Utah juniper (Juniperus osteosperma [Torr.] Little). We resampled plots after a 40-yr interval to evaluate species-specific differences in tree survivorship and establishment from posttreatment age structures. Tree age data were collected in 2008 within four chained sites in eastern Nevada, treated in 1958, 1962, 1968, and 1969 and originally sampled in 1971. The same data were collected at five prescribed burn sites treated in 1975 and originally sampled in 1976. All chained sites had greater juniper survival than pinyon survival immediately following treatment. Chained sites with higher tree survival also had the greatest amount of new tree establishment. During the interval between treatment and the 2008 sampling, approximately four more trees per hectare per year established following chaining than following fire. Postfire tree establishment only occurred for the initial 15 yr and was dominated by juniper. Establishment after chaining was dominated by juniper for the first 15 yr but by pinyon for 15–40 yr following treatment. Results support an earlier successional role for juniper than for pinyon, which is more dependent upon favorable microsites and facilitation from nurse shrubs. Repeated chaining at short intervals, or prescribed burning at infrequent intervals, will likely favor juniper dominance. Chaining at infrequent intervals (> 20–40 yr) will likely result in regained dominance of pinyon. Chaining treatments can be rapidly recolonized by trees and have the potential to create or amplify landscape-level shifts in tree species composition.     

Aboriginal Precedent for Active Management of Sagebrush-Perennial Grass Communities in the Great Basin

Until recently, most contemporary ecologists have ignored or diminished anecdotal historical accounts and anthropologists' reports about aboriginal fire in the Great Basin. Literature review shows that Indians practiced regular use of fire for many purposes, including the obvious reasons of increasing the availability of desired plants, maintaining habitats for animals used as food, and driving game during hunts. Historical accounts of prehistoric anthropogenic firing, inferences from fire-scar data, and data regarding annual production capability of representative sagebrush (Artemisia spp.)-perennial grass ecological sites indicate that prehistoric conditions were neither fuel- nor ignition-limited. According to many sources, this “active management” by Indians was widespread, significant, and more common than lightning-caused fires, resulting in mosaic vegetation patterns that subsequently moderated the behavior of “natural fires.” This interaction between Indian-burning and lightning fires may have strongly influenced the pre-Euro-American settlement vegetation of the Great Basin. At the very least, the landscape was a patchwork of areas altered by aboriginal people and areas shaped primarily by bio-physical processes. Based on this prehistoric precedent, current historically unprecedented conditions (fuel load and exotic weed invasion threats), and predicted climate change, contemporary active management of sagebrush-perennial grass communities is paramount. Restoration measures should be scientifically based and tailored to achieve ecological resilience and functionality in specific sites. Prescribed fire is not always ecologically appropriate or judicious, especially in Wyoming big sagebrush (A. tridentata spp. wyomingensis) communities, so managers should consider using other alternatives where an intentional low severity distubance is deemed necessary. Properly planned active management would disrupt fuel continuity for lighthning fires, ensure ecological process and successional integrity, and benefit multiple uses on a landscape scale.     

Vegetation dynamics after experimental fire disturbance in the arid Succulent Karoo,South Africa

Disturbance by fire in the Succulent Karoo is rare but fire events could increase as a result of an increase in grassiness (alien and indigenous species). This study assessed the effects of fire eight years after an experimentally induced burn in Succulent Karoo vegetation. Post-fire monitoring was conducted using the line intercept method and species counts per plot (1 m²) for each of three fire disturbance treatments: control/unburnt, high and low fuel load. Vegetation cover and abundance were compared across treatments and growth forms. Vegetation cover and abundance on fire-disturbed plots had not returned to pre-fire levels after eight years. Resprouters exhibited a rapid recovery and early dominance on burnt plots. Succulent seedlings established slower, but after eight years occurred at higher densities on the burnt than control plots. Recovery after disturbance of density and cover of long-lived, woody non-resprouter non-succulents was slow relative to resprouting non-succulents and reseeding succulents. This study of vegetation change following fire disturbance in an arid system highlights the slow return of canopy cover, immediate regrowth of only two resprouter species and slower re-establishment by seed of non-resprouter species. In addition, fire disturbance led to the numerical dominance of succulents within the first decade after the fire.     

Mesquite,Tobosagrass, and Common Broomweed Responses to Fire Season and Intensity

There has been increasing interest in the use of summer fires to limit woody plant encroachment on grasslands, but information regarding effects of such fires on perennial grass recovery and annual forb production is also needed. Our objective was to examine effects of fire seasonality and intensity on the woody legume honey mesquite (Prosopis glandulosa Torr.), the C₄ midgrass tobosagrass (Pleuraphis mutica Buckl.), and the annual forb common broomweed (Amphiachyris dracunculoides [DC.] Nutt.). Treatments included summer fires, high-intensity winter fires, low-intensity winter fires, and no burn in replicated plots. None of the fire treatments caused whole-plant mortality (root kill) in mesquite. Mesquite aboveground mortality (top kill) was much greater after summer and high-intensity winter fires than low-intensity winter fires. Tobosagrass total yield (live + dead) was lower following summer fires and was not enhanced by any of the fire treatments for two growing seasons postfire when compared to the no-burn condition. However, tobosagrass live yield was 40% greater in the high-intensity winter fire treatment than the no-burn condition the first summer postfire and recovered in the other fire treatments by the end of the first growing season postfire. Tobosagrass percentage of live tissue was greatest in the summer fire treatment at the end of each of the two growing seasons postfire. Common broomweed cover increased in the summer fire treatment and decreased in both winter fire treatments relative to the no-burn condition by the end of the first growing season postfire. Summer fire offered no clear advantage over high-intensity winter fire with respect to mesquite suppression. However, the increase in late-season tobosagrass percentage live tissue caused by summer fire may be advantageous for forage quality. In addition, patch burning summer fires to increase broomweed cover in selected areas may be useful for wildlife habitat.     

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.     

Simulating Current Successional Trajectories in Sagebrush Ecosystems With Multiple Disturbances Using a State-and-Transition Modeling Framework

Disturbances and their interactions play major roles in sagebrush (Artemisia spp. L.) community dynamics. Although impacts of some disturbances, most notably fire, have been quantified at the landscape level, some have been ignored and rarely are interactions between disturbances evaluated. We developed conceptual state-and-transition models for each of two broad sagebrush groups—a warm-dry group characterized by Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young) communities and a cool-moist group characterized by mountain big sagebrush (Artemisia tridentata Nutt. subsp. vaseyana [Rydb.] Beetle) communities. We used the Vegetation Dynamics Development Tool to explore how the abundance of community phases and states in each conceptual model might be affected by fire, insect outbreak, drought, snow mold, voles, sudden drops in winter temperatures (freeze-kill), livestock grazing, juniper (Juniperus occidentalis var. occidentalis Hook.) expansion, nonnative annual grasses such as cheatgrass (Bromus tectorum L.), and vegetation treatments. Changes in fuel continuity and loading resulted in average fire rotations of 12 yr in the warm-dry sagebrush group and 81 yr in the cool-moist sagebrush group. Model results in the warm-dry sagebrush group indicated postfire seeding success alone was not sufficient to limit the area of cheatgrass domination. The frequency of episodes of very high utilization by domestic livestock during severe drought was a key influence on community phase abundance in our models. In the cool-moist sagebrush group, model results indicated at least 10% of the juniper expansion area should be treated annually to keep juniper in check. Regardless, juniper seedlings and saplings would remain abundant.     

Effect of season of burning on grass recovery in the false thornveld of the eastern cape

Abstract

Season of burning is one of the most controversial questions concerning the use of fire in veld management. In the summer rainfall areas of South Africa the generally accepted rule of burning only after the first spring rains has proven ineffectual when using fire to control bush encroachment because the fires are too cool when burnt at this time. It was therefore decided to investigate the effect of burning on the regrowth of grass when applied during mid‐winter, spring, late spring and early summer. The results showed that burning when the grass was dormant (mid‐winter) had no deleterious effect on the recovery of grass when compared with burning after the first spring rains (spring). Conversely burning when the grass was actively growing (early summer) seriously retarded its regrowth.     

火烧后亚高山草甸恢复过程中物种组成和群落特征变化规律的研究

为了解火烧对植物群落结构和植被恢复速度的影响,本研究以甘肃省皇城羊场亚高山草甸为研究对象,于2017年5月进行了火烧试验,并分别在2017,2018及2019年的5月（返青期）、7月（生长期）和9月（生长末期）测量了该区域火烧样地和原生样地的植被覆盖度、群落多样性和裸地百分比等指标。结果表明：2019年5月后火烧样地与原生样地间植物群落多样性指数（Margalef指数、Shannon-Wiener指数、Simpson指数和Pielou指数）间差异不显著;火烧后引起的植物结构变化是短暂的,并随着时间的推移逐渐减少甚至消失,恢复时间大约16个月左右;同时火烧改变了物种组成,其中在火烧样地中甘肃马先蒿（Pedicularis kansuensis）和锐果鸢尾（Iris goniocarpa）逐渐消失,而鳞叶龙胆（Gentiana squarrosa）和火绒草（Leontopodium leontopodioides）逐渐出现。本研究说明春季火烧对亚高山草甸植物组成和结构有一定的调节作用,可作为亚高山草甸管理的有效措施。     

Long-Term Response Patterns of Tallgrass Prairie to Frequent Summer Burning

Knowledge of how tallgrass prairie vegetation responds to fire in the late growing season is relatively sparse and is based upon studies that are either spatially or temporally limited. To gain a more robust perspective of vegetation response to summer burning and to determine if repeated summer fire can drive vegetational changes in native tallgrass prairie, we evaluated species cover and richness over a 14-yr period on different topographic positions from ungrazed watersheds that were burned biennially in the growing season. We found that annual forbs were the primary beneficiaries of summer burning, but their fluctuations varied inconsistently among years. Concomitantly, species richness and diversity increased significantly with summer burning but remained stable through time with annual spring burning. After 14 yr, species richness was 28% higher in prairie that was burned in the summer than in prairie burned in the spring. Canopy cover of big bluestem (Andropogon gerardii Vitman) and Indiangrass (Sorghastrum nutans [L.] Nash) increased significantly over time with both summer and spring burning, whereas heath aster (Symphyotrichum ericoides [L.] Nesom), aromatic aster (Symphyotrichum oblongifolium [Nutt.] Nesom), and sedges (Carex spp.) increased in response to only summer burning. Kentucky bluegrass (Poa pratensis L.) cover declined in both spring-burned and summer-burned watersheds. Repeated burning in either spring or summer did not reduce the cover or frequency of any woody species. Most perennial species were neutral in their reaction to summer fire, but a few species responded with large and inconsistent temporal fluctuations that overwhelmed any clear patterns of change. Although summer burning did not preferentially encourage spring-flowering forbs or suppress dominance of the warm-season grasses, it is a potentially useful tool to increase community heterogeneity in ungrazed prairie.     

Hydrologic and Erosion Responses of Sagebrush Steppe Following Juniper Encroachment,Wildfire, and Tree Cutting

Extensive woodland expansion in the Great Basin has generated concern regarding ecological impacts of tree encroachment on sagebrush rangelands and strategies for restoring sagebrush steppe. This study used rainfall (0.5 m² and 13 m² scales) and concentrated flow simulations and measures of vegetation, ground cover, and soils to investigate hydrologic and erosion impacts of western juniper (Juniperus occidentalis Hook.) encroachment into sagebrush steppe and to evaluate short-term effects of burning and tree cutting on runoff and erosion responses. The overall effects of tree encroachment were a reduction in understory vegetation and formation of highly erodible, bare intercanopy between trees. Runoff and erosion from high-intensity rainfall (102 mm · h^?1, 13 m² plots) were generally low from unburned areas underneath tree canopies (13 mm and 48 g · m^?2) and were higher from the unburned intercanopy (43 mm and 272 g · m^?2). Intercanopy erosion increased linearly with runoff and exponentially where bare ground exceeded 60%. Erosion from simulated concentrated flow was 15- to 25-fold greater from the unburned intercanopy than unburned tree canopy areas. Severe burning amplified erosion from tree canopy plots by a factor of 20 but had a favorable effect on concentrated flow erosion from the intercanopy. Two years postfire, erosion remained 20-fold greater on burned than unburned tree plots, but concentrated flow erosion from the intercanopy (76% of study area) was reduced by herbaceous recruitment. The results indicate burning may amplify runoff and erosion immediately postfire. However, we infer burning that sustains residual understory cover and stimulates vegetation productivity may provide long-term reduction of soil loss relative to woodland persistence. Simply placing cut-downed trees into the unburned intercanopy had minimal immediate impact on infiltration and soil loss. Results suggest cut-tree treatments should focus on establishing tree debris contact with the soil surface if treatments are expected to reduce short-term soil loss during the postcut understory recruitment period.     

Ecological Scale of Bird Community Response to Piñon-Juniper Removal

Piñon (Pinus spp.) and juniper (Juniperus spp.) removal is a common management approach to restore sagebrush (Artemisia spp.) vegetation in areas experiencing woodland expansion. Because many management treatments are conducted to benefit sagebrush-obligate birds, we surveyed bird communities to assess treatment effectiveness in establishing sagebrush bird communities at study sites in Utah, Nevada, Idaho, and Oregon. Our analyses included data from 1 or 2 yr prior to prescribed fire or mechanical treatment and 3 to 5 yr posttreatment. We used detrended correspondence analysis to 1) identify primary patterns of bird communities surveyed from 2006 to 2011 at point transects, 2) estimate ecological scale of change needed to achieve treatment objectives from the relative dissimilarity of survey points to the ordination region delineating sagebrush bird communities, and 3) measure changes in pre- and posttreatment bird communities. Birds associated with sagebrush, woodlands, and ecotones were detected on our surveys; increased dissimilarity of survey points to the sagebrush bird community was characterized by a gradient of increased juniper and decreased sagebrush cover. Prescribed fires burned between 30% and 97% of our bird survey points. However, from 6% to 24% cover of piñon-juniper still remained posttreatment on the four treatment plots. We measured only slight changes in bird communities, which responded primarily to current vegetation rather than relative amount of change from pretreatment vegetation structure. Bird communities at survey points located at greater ecological scales from the sagebrush bird community changed least and will require more significant impact to achieve changes. Sagebrush bird communities were established at only two survey points, which were adjacent to a larger sagebrush landscape and following almost complete juniper removal by mechanical treatment. Our results indicate that management treatments that leave residual woodland cover and are not adjacent to extensive sagebrush stands are unlikely to establish sagebrush birds.     

A Hierarchical Perspective to Woody Plant Encroachment for Conservation of Prairie-Chickens

Encroachment of Great Plains grasslands by fire-sensitive woody plants is a large-scale, regional process that fragments grassland landscapes. Using prairie grouse (Tympanuchus spp.) of conservation concern, we apply hierarchy theory to demonstrate how regional processes constrain lower-level processes and reduce the success of local management. For example, fire and grazing management may be locally important to conservation, but the application of fire and grazing disturbances rarely cause irreversible fragmentation of grasslands in the Great Plains. These disturbance processes cause short-term alterations in vegetation conditions that can be positive or negative, but from a long-term perspective fire maintains large tracts of continuous rangelands by limiting woody plant encroachment. Conservation efforts for prairie grouse should be focused on landscape processes that contribute to landscape fragmentation, such as increased dominance of trees or conversion to other land uses. In fact, reliance on local management (e.g., maintaining vegetation structure) to alter prairie grouse vital rates is less important to grouse population persistence given contemporary landscape level changes. Changing grass height, litter depth, or increasing the cover of forbs may impact a few remaining prairie-chickens, but it will not create useable space at a scale relevant to the historic conditions that existed before land conversion and fire suppression.     

Recovery of Big Sagebrush Following Fire in Southwest Montana

Fire plays a large role in structuring sagebrush ecosystems; however, we have little knowledge of how vegetation changes with time as succession proceeds from immediate postfire to mature stands. We sampled at 38 sites in southwest Montana dominated by 3 subspecies of big sagebrush (Artemisia tridentata Nutt.). At each site we subjectively located 1 sample plot representing the burned area and an unburned macroplot in similar, adjacent, unburned vegetation. Canopy cover of sagebrush was estimated, and plants were counted in 10 microplots. Age and height of randomly chosen sagebrush plants in each size class were determined from 5 microplots. Average postfire time to full recovery of mountain big sagebrush (ssp. vasseyana [Rydb.] Beetle) canopy cover was 32 years, shorter for basin (ssp. tridentata) and much longer for Wyoming (ssp. wyomingensis Beetle & Young) big sagebrush. Height recovered at similar rates. There was no difference in canopy cover or height recovery between prescribed fires and wildfires in stands of mountain big sagebrush. We found no relationship between mountain big sagebrush canopy cover recovery and annual precipitation, heat load, or soil texture. Nearly all unburned sagebrush macroplots were uneven-aged, indicating that recruitment was not limited to immediate postfire conditions in any of the subspecies. Average canopy cover of three-tip sagebrush (A. tripartita Rydb.) did not increase following fire, and many three-tip sagebrush plants established from seed instead of sprouting. Our results suggest that the majority of presettlement mountain big sagebrush stands would have been in early to midseral condition in southwest Montana assuming a mean fire interval of 25 years. Only long fire-return intervals will allow stands dominated by Wyoming big sagebrush to remain on the landscape in our study area. We speculate that effects of site-specific factors conducive to sagebrush recovery are small compared to stochastic effects such as fire.     

Short-Term Butterfly Response to Sagebrush Steppe Restoration Treatments

As part of the Sagebrush Steppe Treatment Evaluation Project (SageSTEP), butterflies were surveyed pretreatment and up to 4 yr posttreatment at 16 widely distributed sagebrush steppe sites in the interior West. Butterfly populations and communities were analyzed in response to treatments (prescribed fire, mechanical, herbicide) designed to restore sagebrush steppe lands encroached by piñon-juniper woodlands (Pinus, Juniperus spp.) and invaded by cheatgrass (Bromus tectorum). Butterflies exhibited distinct regional patterns of species composition, with communities showing marked variability among sites. Some variation was explained by the plant community, with Mantel's test indicating that ordinations of butterfly and plant communities were closely similar for both woodland sites and lower-elevation treeless (sage-cheat) sites. At woodland sites, responses to stand replacement prescribed fire, clear-cutting, and tree mastication treatments applied to 10–20-ha plots were subtle: 1) no changes were observed in community structure; 2) Melissa blues (Plebejus melissa) and sulfurs (Colias spp.) increased in abundance after either burning or mechanical treatments, possibly due to increase in larval and nectar food resource, respectively; and 3) the juniper hairstreak (Callophrys gryneus) declined at sites at which it was initially present, probably due to removal of its larval food source. At sage-cheat sites, after prescribed fire was applied to 25–75-ha plots, we observed 1) an increase in species richness and abundance at most sites, possibly due to increased nectar resources for adults, and 2) an increase in the abundance of skippers (Hesperiidae) and small white butterflies. Linkages between woody species removal, the release of herbaceous vegetation, and butterfly response to treatments demonstrate the importance of monitoring an array of ecosystem components in order to document the extent to which management practices cause unintended consequences.