Use of Fire in Population Management
Miller and Eddleman  acknowledge the debate on benefits of fire to enhance sage-grouse habitat. They state 4 factors determine negative or positive outcome of fire on sage-grouse habitat: 1) site potential, 2) site condition, 3) functional plant group(s) that is(are) limiting, and 4) pattern/size of the burn. Fire is a useful tool to enhance native perennial grass and forbs, particularly in areas where sagebrush is abundant, a "good" population of native forbs is present, and exotic species are limited.
This most often applies to mountain big sagebrush communities where shrub cover can exceed 35% and perennial forbs can increase 2-3 fold following fire . There is little evidence that fire will enhance sage-grouse habitat where there is already a balance of native shrubs and perennial grasses and forbs. Fire should not be used where sagebrush cover is the limiting factor for sage-grouse or where the understory lacks perennial forbs and grasses and introduced annuals are present.
Response of native understory species to fire is usually determined by moisture spectrum and condition of the site. On mesic sites, fire is useful for increasing amounts, nutrient quality, and season of succulence of perennial grasses and annual forbs important in sage-grouse diet. However, in the drier sagebrush cover types, perennial forbs are not increased by fire.
Fire can open up dense stands of sagebrush and increase landscape level heterogeneity, or homogenize large landscapes by removing the shrub layer and promoting dominance of introduced annuals. Blaisdell and others  state primary use of fire on sagebrush-grass ranges should be to control dense stands of sagebrush so more desirable species can increase. The goal should be roughly consistent with the climax cover that can be attained in a particular habitat type or site. In addition, they state grazing management after burning is essential. Most burns should be completely protected from livestock grazing for at least 1 and possibly 2 growing seasons. Benson and others  recommend a nongrazing period of 2-3 years. On areas where cheatgrass (Bromus tectorum) is abundant, special measures may be necessary to prevent recurrent fires .
Braun and others  provide the following guidelines to be used when altering sagebrush habitat:
1. The state wildlife agency will be notified of each specific proposal to control vegetation a minimum of 2 years in advance of treatment by means of an "Environmental assessment." In situations where it is not possible to provide such notice (i.e. private lands), the state wildlife agency should be notified as soon as the project is proposed. Lead time is necessary to evaluate control projects during all seasons of the year. a.) The public land-management agency will provide the state wildlife agency with maps on which the proposed treatment areas are located along with detailed plans as to the type of treatment and expected results. b.) The state wildlife agency will plot sage-grouse use leks, nesting areas, wintering sites, and meadows and summer range or brooding areas on the maps. c.) Representatives of the cooperating agencies will meet on the proposed project area for an on-the-ground inspection following completion of the maps. d.) No sagebrush will be treated or removed until a comprehensive multiple-use management plan has been completed for the area. e.) Project plans for sagebrush control will include provisions for long-term quantitative measurements of vegetation before and after control to acquire data on the effects on wildlife habitats, and to ascertain whether objectives of the project were accomplished. The land-management agency should bear responsibility for evaluation of the project as it relates to habitat, while the state wildlife agency should assume responsibility of measuring the effects of the project on the sage-grouse resource.
2. No sagebrush control work will be considered where live sagebrush cover is less than 20%, or on steep (20% or more gradient) upper slopes with skeletal soils where big sagebrush is 12 inches (30 cm) or less in height.
3. The breeding complex (leks and nesting areas) will be considered as all lands within a 1.9 mile (3 km) radius of an occupied lek (in some situations, depending on the quality of the nesting habitat, this radius may well exceed 1.9 miles (3 km)). Control of vegetation within the breeding complex will not be undertaken within 1.9 miles (3 km) of leks or on nesting and brood areas. On-site investigations by land-management and state wildlife agency personnel will be essential to determine inviolate areas. Areas to be protected from treatment will be marked on maps.
4. There will be no sagebrush control attempted in any area known to have supported important wintering concentrations of sage-grouse within the preceeding 10 years.
5. No control will be attempted along streams, meadows, or secondary drainages (dry or intermittent). A 109 yard (100 m) strip (minimum) of living sagebrush will be retained on each edge of meadows and drainages. On-site inspections by land-management and wildlife agency personnel will be made to assess the desirability of increasing or decreasing the width of untreated strips in specific areas.
6. When sagebrush control is found to be unavoidable in sage-grouse range, all treatment measures should be applied in irregular patterns using topography and other ecological considerations to minimize adverse effects to sage-grouse. Widths of untreated areas can vary for the convenience of application technique, except treated areas will not be wider than 33 yards (30 m) and untreated areas will be at least as wide as treated areas. Untreated areas will not be treated until food and cover plants in the treated areas attain comparable composition to the treated areas.
7. Where possible, spraying will be done with a helicopter or ground equipment. No spraying will be done when wind velocity exceeds 6.2 miles per hour (10 km/hr.)
8. Whenever possible, complete kill or removal of sagebrush in treated areas should be avoided. Partial kill or removal of sagebrush may enhance the area for livestock, prevent loss of all snow cover in winter, and allow for some use of the disturbed area by sage-grouse.
Prescribed fire has been used by the U.S. Forest Service on sagebrush lands in the 12-inch (300 mm) or greater precipitation zones. Results have usually been positive in terms of forb response. In the 8- to 12-inch (200-300 mm) precipitation zones, best results seem to occur with April burns when fine fuels from the previous growing season carry a relatively "cool" fire. Small burns in irregular patterns or strips not exceeding 50 yards (45 m) in width and 100 yards (90 m) long are best. Where wildfire is a concern during summer months, burned strips perpendicular to the prevailing summer winds serve as fire breaks .
After a study of sage-grouse use of burned, unburned, and seeded sites, Sime  summarized several factors researchers feel should be considered before using fire to manage for sage-grouse: 1) Radio telemetry rather than observation should be used to insure proper identification of seasonal ranges of specific population segments as some segments may be sedentary while others are migratory . 2) Openings in the overhead canopy should be restricted to 1 to 10 acres (0.4-4.0 ha) . 3) Fire should only be used when desirable vegetation is dormant so as not to harm the plant species grouse rely on for food and/or cover . 4) The burn site should not be grazed until a vigorous stand of self-perpetuating vegetation is well established . Fire would be most effective in areas where annual precipitation enables rapid revegetation and in areas with a limited potential for invasion of the site by weedy, undesirable species. When few propagules from the native vegetation community are available or when fire is used in areas of low precipitation, the disturbed site may require artificial seeding. Seeding crested wheatgrass (Agropyron cristatum) in sage-grouse range is not recommended.
Call and Maser  suggest the following list to consider when using fire to manage sage-grouse habitats:
1) Fire is an inexpensive tool that can be used for habitat manipulation, but all projects must be carefully evaluated, planned, and supervised. A set of clear objectives is essential.
2) Fire is best used in a manner that results in a mosaic pattern of shrubs and open areas, where the resultant openings range in size from 1 to 10 acres (0.4-4.0 ha).
3) Large, severe fires may remove an excessive amount of cover or may sterilize the soil.
4) Burning within an area should be done on a rotational basis, different patches burned every few years, with as long as 20 years between burning treatments on each site. This will produce a variety of habitats within the general area. Timing of treatments over the years will depend on sagebrush response and growth rates at specific sites.
5) Best results from burning occur in late April and early May when dry grasses and other herbaceous fuels from the previous growing season will carry a relatively "cool" fire. This will leave some sagebrush and still create openings for additional growth of grasses. Fires in late spring and early summer, however, could destroy many nesting birds and other young wildlife, including sage-grouse, so use of fire is preferable when young are capable of escaping. At times, it may be necessary to use prescribed fire in the spring to obtain the desired changes in habitat. Strip burns that do not exceed 50 yards (45 m) in width and 100 yards (90 m) in length create desirable openings for sage-grouse .
6) Sagebrush habitats identified as important wintering areas that are still in vigorous condition should remain intact. Sage-grouse depend on sagebrush leaves in such areas, not on potential development of grass and forbs in the understory or interspersed openings. If important stands of sagebrush used by sage-grouse for wintering have deteriorated because of such things as insects, old age, or livestock grazing, the manager should initiate measures to rejuvenate the stand by light chaining, by reduced grazing, or other means.
7) Four primary elements needed for a successful burn in areas with more than 11.8 inches (300 mm) of precipitation are (1) wet soil; (2) windspeed in excess of 8 mph (12.8 km/hr) and gusty; (3) fine fuels of 612-704 pounds/acre (278-320 kg/ha); and 4) no burning after spring grass growth reaches 2 inches (5 cm) unless burning is to improve the forbs in the community. Prescribed burns should be conducted when plants preferred as food by sage-grouse are dormant .
8) Livestock concentrate on burned areas and eat the new growth, so they need to be carefully managed. Haphazard burning and heavy grazing accelerate sagebrush reinvasion, soil erosion, and loss of forage plants desirable for both grouse and livestock. Grazing use must therefore be regulated to prevent excessive reinvasion by sagebrush (more than 10,000/acre (24,700/ha)) and to prevent removal of more than 50% of the annual herbaceous growth (by weight).
9) Sagebrush taxa and their value to grouse need to be identified prior to burning. Some subspecies, such as mountain big sagebrush, may invade an area immediately after burning and may not be as desirable for sage-grouse as the original species or subspecies .
Breeding: Regardless of the method used to reduce or eliminate sagebrush cover in sage-grouse breeding habitat, control actions have the potential for reducing breeding populations of sage-grouse. Moreover, sagebrush reduction programs may exacerbate the negative effects of natural phenomena such as drought, causing extreme declines in the sage-grouse populations . Martin  found 80% of all cock sage-grouse and over 80% of all hen locations were in sagebrush stands with canopy cover exceeding 20%. He comments this is also the range of sagebrush canopy cover where control is most likely to occur.
Before making any alterations of sagebrush habitat in the vicinity of leks, Ellis and others  recommend the following: 1) When possible, protect all sagebrush within 1.86 miles (3 km) radius of a lek as suggested by Braun and others . 2) If alteration is unavoidable within 1.86 miles (3 km) of a lek, identify day-use areas. Once the core-use area has been identified, protect it and try to provide a buffer zone around it if possible. Because sage-grouse often walk to day-use areas, it is recommended that a continuous strip (i.e. travel lane) no less than 656 feet (200 m) be maintained between the lek and the day-use areas. 3) If day-use areas are identified and it is concluded that they cannot be protected, the manager should determine their physical sagebrush characteristics. Preservation of statistically similar adjacent stands along with an adjoining travel lane may provide male grouse with necessary habitat to continue using the lek. Any planned alterations should be done after males have moved to summer or fall ranges. Wallestad and Pyrah  suggest a 2-mile (3.2 km) buffer zone around a lek should be protected from all sagebrush eradication if the manager has not identified the wintering-nesting complexes associated with it.
A fire in the right place at the right time, and of the correct size and intensity can create an opening that can be used as a lek. Such openings, 1 to 10 acres (0.4-4 ha) in size and at the elevations used for breeding, may be beneficial to sage-grouse in homogeneous sagebrush habitats .
Nesting: Sage-grouse prefer light to moderate sagebrush densities for nesting. Where sagebrush is dense (in excess of 20-40% canopy cover) and greater than 2 feet (61 cm) in height, controlled burning to create a mosaic of sagebrush and grassland with a variety of sagebrush heights would probably be beneficial to the birds. Repeated burning could be adverse in this case, as would large "hot" fires that remove an excessive amount of cover [24,72]. Where cover is all ready limited, fires could cause adverse conditions for the birds [59,72].
The U.S. Fish and Wildlife Service currently uses fire as a management tool to improve sage-grouse nesting and brood-rearing habitat at the Hart Mountain National Antelope Refuge (HMNAR) in Oregon . To evaluate recovery of burned vegetation with respect to sage-grouse nesting and brood-rearing requirements, Nelle and others  recommend that scheduling when a habitat is burned should not be predetermined by the length of time since the area last burned. By measuring 3 variables (sagebrush height, percent sagebrush canopy cover, and percent total shrub cover) at permanent, randomly located transects within burned vegetation, a fast and efficient monitoring program to follow the recovery of vegetation could be implemented.
Also on the HMNAR, DeLong and others  studied nesting habitat in relation to predation. They suggest prescribed fire would reduce shrub cover and may increase herbaceous cover. Sagebrush reduction, however may negatively affect sage-grouse nesting habitat in the short term , and should only be implemented in areas where other suitable nesting habitat exists nearby. In the long term, once sagebrush re-establishes in treatment areas, sage-grouse nesting habitat may be enhanced by an improved balance of shrub and grass components available to sage-grouse. They recommend land management practices that increase cover and height of native grasses in sagebrush communities with medium-height shrubs as a means to enhance sage-grouse nesting success and productivity .
Pyle and Crawford  report increased production of forbs and perennial grasses following fire in sagebrush. Increases in perennial grass cover should improve nesting habitat by providing hens with more cover from predators. Greater forb availability should provide hens with more opportunities to meet their physiological demands for nesting and renesting. Burning may be used to increase herbaceous cover or decrease shrub cover but the shrub component is critical to a sagebrush obligate such as sage-grouse . Frequent burns that promote invasion by exotics such as cheatgrass or large burns that remove the sagebrush overstory may not be used by nesting or brood-rearing sage-grouse until sagebrush becomes re-established [30,71]. Managers must consider size of burns, juxtaposition of habitat components, and frequency of burns if they want to improve habitat while still maintaining all components needed by sage-grouse year round .
Burning to remove sagebrush on the Upper Snake River Plain is not justifiable as a sage-grouse management practice because only unburned vegetation in the area offers suitable nesting habitat. No brush control work should occur where live sagebrush cover is less than 20%  as it is on the Upper Snake River Plain. From 1980 to 1996, 28,840 acres (11,676 ha) were burned by prescribed fire on the Upper Snake River Plain, which accounted for 29% of the study area, none of which was suitable nesting habitat in 2000 . Connelly and others  found no evidence that nest success, and thus nest habitat, increased in the treatment area after a prescribed burn on the Upper Snake River Plain and recommend that prescribed burns be avoided in relatively xeric habitats used by wintering and breeding sage-grouse. During drought periods, they recommend prescribed burns be totally prohibited in these habitats.
Brood rearing: Prescribed burning may have different long-term effects as species diversity of vegetation and invertebrate food resources change with succession  and could result in suboptimal nesting and brood-rearing habitat. The cumulative effect of burning upon critical nesting and brood-rearing habitats could be seriously detrimental to a sage-grouse population if vegetation over a large area remains in suboptimal condition for many years. Burn programs should be planned to avoid creating a landscape of adjacent young burns, especially of burns younger than 14 years. Inherent variation in vegetation responses to burning can render predicting the long-term effects of fire difficult .
Spot burns in which several patches of a few acres are burned can produce suitable brood-rearing areas. Spot burns along the edges of meadows where sagebrush is encroaching may also enhance brood-rearing areas, although care should be taken to leave an adequate sagebrush-meadow ecotone to provide necessary cover for sage-grouse. Spring burns during the nesting period must be avoided, but late fall burns may be an alternative where brood-rearing habitats are needed. Burning should seldom be allowed on areas where nesting habitat is limited . Wrobleski  states increases in percent of annual forb production in burned areas will likely provide a rich forage base for prelaying females and young chicks. Abundant food forbs in close proximity to unburned sagebrush cover could benefit sage-grouse broods by providing additional food with adequate cover. In a study in Idaho, Martin  found burning improved habitat for sage-grouse broods. During both postburn years of his study, forb crown cover was significantly higher in burned habitats than in unburned habitats.
Klebenow  states broods seek out areas where their favorite food forbs are abundant. He states most sites like this have been depleted by excessive grazing and require rejuvenation, and fire can be an important part of management to improve these lands. Burning small areas to achieve a mosaic of food and cover areas should produce a pattern most suitable for sage-grouse. Different stages of successional growth would be desirable in order to produce the greatest variety of food forb items. Burning should probably be done on a rotational basis, burning different patches each year or every few years, possibly with as long as 20 years between burning treatments on each site. A diversity of habitat types, in terms of both food and cover, should be an objective for this habitat. Using fire to open dense sagebrush canopies in occupied sage-grouse range may enhance brood-rearing areas by increasing forb production according to Sime . She also suggests prescribed burning could be used to mitigate for spring/summer habitat lost to agricultural, industrial, or human development and would benefit both sexes and all ages of a sage-grouse population.
Miller and Eddleman  have compiled the following information from various authors on the relative response of forbs common to the sagebrush biome and used as food by sage-grouse:
(S = severely damaged, O = 0 to slight damage, U = undamaged, + = increases, - = declines).
|tapertip onion (Allium accuminata)||U|
|Antennaria spp. (mat spp.)||S|
|Pursh's milk-vetch (Astragalus purshii)||O|
|parsnipflower buckwheat (Eriogonum hieracleoides)||S|
|prickly lettuce (Lactuca serriola)||O-U|
|slender phlox (Microsteris gracilis)||U|
|spiny phlox (Phlox hoodii)||S|
|lambstongue groundsel (Senecio intergerrimus)||O|
|yellow salsify (Tragopogon dubius)||O|
|largehead clover (Trifolium macrocephalum)||U|
The mountain big sagebrush/antelope bitterbrush habitat type is a key brood-rearing habitat of sage-grouse [71,76]. Fall and spring prescribed fire in dense sagebrush-bitterbrush stands did not adversely influence most primary insects and forbs available on burned sites. Indeed, the food supply on burned sites was enhanced based on the increased frequency of dandelion taxa, total forb cover, total forb diversity, and habitat heterogeneity. However, sage-grouse broods require sagebrush for cover on a daily basis , so burning or other practices conducted in montane settings could reduce foraging habitat if an interspersion of treated and untreated sites is not maintained . Pyle and Crawford  also found that fall burning increased frequency of dandelion taxa on HMNAR, but apparently had no effect on other primary foods after a study of prescribed burning from 1987 to 1989. June and darkling beetles, primary foods of sage-grouse chicks, were unaffected by prescribed fire. Total forb cover ranged from 13 to 15% on burned plots to 8% on unburned controls during the 2nd growing season. The same prescribed fire reduced total shrub cover from 1987 to 1989. Authors stated fall-burned sites were perhaps most suitable to broods because they supported the greatest amount of dandelion taxa. However, the prescribed fire reduced sagebrush cover which diminished its site value as a food and cover source for broods. Brood cover was changed but not eliminated by prescribed fire. Cover was altered from dominance by shrubs before burning to dominance by forbs, grasses, and sprouting shrubs after burning.
Wrobleski  studied greater sage-grouse brood-rearing habitat on the HMNAR in Oregon. He compared burned and unburned plots and found:
1. (Morphological) Reproductive effort by individual plants of at least 5 species was greater in 1st-year burned areas, indicating that fire-enhanced flowering occurred in some of the herbaceous dicot species used by sage-grouse. This increased response was observed in both annual (Phlox spp.) and perennials (Lomatium spp., Modoc hawksbeard, shaggy milkvetch, and longleaf phlox).
2. (Phenological) There was a longer period of active photosynthesis observed in all selected species in burned plots.
3. (Arthropod abundance) Populations of arthropods appear to be able to maintain themselves through disturbance by fire.
Greater numbers of inflorescences and flowers provide prenesting hens and broods with increased quantities of higher quality foods. By extending the period of potential photosynthesis and plant succulence on these herbaceous dicot species, forage quality will be higher later into the dry season .
Connelly and others  warn against using fire in relatively low precipitation areas dominated by Wyoming big sagebrush to improve brood-rearing habitat for migratory greater sage-grouse. A study by Fischer and others  indicated the short-term effects of prescribed fire in a xeric (less than 10 inches (250 mm) of annual precipitation) environment did not enhance brood-rearing habitat and may have been detrimental to grasshoppers, which are important in sage-grouse diets. Abundance of grasshoppers was significantly lower in burned habitat the 2nd (P=0.003) and 3rd (P=0.0001) postburn years.
Summer: In a study by Connelly and others  on migratory greater sage-grouse in a xeric region of Idaho, fire apparently did not improve or create summer habitat adjacent to the breeding range. Continuation of long distance movements from the breeding area to summer range up to 4 years after the fire appears to confirm this.
Winter: Any proposed type conversion which includes winter-use areas must be carefully considered. Approval should not be given prior to an on-the-ground inspection of sage-grouse winter distribution during peak snow conditions. What may appear to be an excessive amount of sagebrush during summer months may provide only minimal amounts available above the snow for wintering birds. Burning should seldom be allowed on winter use areas and reseeding may be needed in xeric zones . Critical winter habitats are very vulnerable to treatment since big sagebrush control has traditionally been directed towards dense stands on flat to gentle slopes [45,103]. Braun and others  state quality of sage-grouse wintering habitat after sagebrush removal treatments is directly related to the amount of sagebrush remaining. In light of the number of months of use by sage-grouse and the potentially large area that a winter range may influence, removal of sagebrush from these segments would greatly reduce sage-grouse populations over large areas . Loss of sagebrush on a relatively small area, but a relatively large portion of wintering habitat, was followed by a large decline in sage-grouse numbers in Montana . Beck  states disturbance of sage-grouse winter habitat in identified winter-use areas should be avoided or kept to a minimum.
Connelly and others  suggest that in some instances, especially where the herbaceous understory is badly depleted or junipers (Juniperus spp.) have invaded, fire may be used to improve the ecological condition of a site. If fire is used in this manner, treatment should be designed to preserve sage-grouse winter habitat and allow rapid recolonization of the burned area by sagebrush.
Robertson  studied the effects of an August, 1989, prescribed burn on the winter ecology of migratory greater sage-grouse in southeastern Idaho. Before the prescribed fire, greater sage-grouse were located on the proposed treatment area 42% (1988) and 34% (1989) of the time. Following the fire in fall of 1989, only 6% of greater sage-grouse locations were found within the burned area. The prescribed burning of winter range probably caused this change in distribution. The mosaic effect of the vegetation created by the burn should still maintain stands of adequate habitat within the burn, but other factors such as inability to occupy snow roosts, theremoregulatory stress, and intraspecific competition, might preclude the use of these areas as suitable cover. Burning did not appear to adversely influence greater sage-grouse on the study area except for redistributing them. If adequate habitat is not available within 6.21 miles (10 km) (the limit of movements from leks of capture during the study) sage-grouse may suffer higher rates of predation and/or starvation, or sage-grouse may emigrate to areas where habitat is more readily available. Moreover, even if critical wintering habitat is not lost in a fire, loss of habitat required during the breeding/brood-rearing season is possible. The guideline for protecting habitat within 1.86 miles (3 km) of a lek  may not provide adequate protection of winter range for a migratory population, because sage-grouse were located over twice that distance from their lek of capture. Since no differentiation on a large scale can be made between winter and spring use areas, sagebrush management should only be initiated when all factors are considered. Any prescribed burning on environments having migratory populations of sage-grouse should be initiated only after critical use areas are identified. Critical wintering areas can be defined as those areas sustaining use by sage-grouse in winters of "above average" snowfall. Habitat may be plentiful in years of average snowfall; however, wintering sage-grouse could be negatively impacted should prescribed burning take place on critical seasonal-use areas.
In another Idaho study conducted in xeric, migratory greater sage-grouse habitat, Connelly and others  determined burning likely has a detrimental effect on greater sage-grouse populations, and areas affected by prescribed burns may burn again because of wildfire. Results of their study do not support use of fire to improve rangelands that provide satisfactory sage-grouse habitat. The authors urge managers to refrain from burning in low precipitation (10.4 inches (< 260 mm)) sagebrush habitats that are used by breeding greater sage-grouse.
For specific information on use of fire in various types of sagebrush habitats, see the Fire Effects section of sagebrush reviews on this website.FIRE CASE STUDIES SPECIES: Centrocercus minimus, C. urophasianus
- FIRE CASE STUDY CITATION
- SEASON/SEVERITY CLASSIFICATION
- STUDY LOCATION
- PREFIRE HABITAT
- SITE DESCRIPTION
- FIRE DESCRIPTION
- FIRE EFFECTS ON ANIMAL SPECIES AND HABITAT
- FIRE MANAGEMENT IMPLICATIONS
McWilliams, Jack, compiler. 2002. Effects of prescribed fire on Wyoming big sagebrush communities: implications for ecological restoration of greater sage-grouse habitat. In: Centrocercus minimus, C. urophasianus. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [ var months = new Array(12); months = "January"; months = "February"; months = "March"; months = "April"; months = "May"; months = "June"; months = "July"; months = "August"; months = "September"; months = "October"; months = "November"; months = "December"; var date = new Date(); var year = date.getFullYear(); var month = date.getMonth(); var day = date.getDate(); document.write(year+", "+months[month]+" "+day); ].
Wrobleski, David W. 1999. Effects of prescribed fire on Wyoming big sagebrush communities: implications for ecological restoration of sage grouse habitat in Oregon. Corvallis, OR: Oregon State University. 76 p. Thesis. .
Fall/Severe but patchy
Fires were ignited 23-28 September, 1997. Mean estimate of fireline intensity was 1,321 kWm-1, and reaction intensity was 302 kW/m2.
Hart Mountain National Antelope Refuge, Oregon
Total shrub cover before treatment was 26 Â± 1.6% in treatment plots and 24 Â± 1.5% in control plots. Sagebrush (Artemisia spp.) cover (22%) on all plots before treatment comprised 87% of all shrub cover. Other common shrubs on the study plots before treatment (2.7% total cover) were spiny hopsage (Atriplex spinosa) and broom snakeweed (Gutierrezia sarothrae). Small communities dominated by low sage (Artemisia arbuscula) and basin big sagebrush (A. tridentata ssp. tridentata) were found within the study area but were not sampled. Prefire shrub density in burned plots ranged from 39,690 to 71,880 individuals acre-1 (16,063 to 29,091 ha-1).
There were 8 species of grasses observed before the fire. Sandberg bluegrass (Poa secunda) and bottlebrush squirreltail (Elymus elymoides) both had 45% prefire frequency and were the dominant grasses. Cheatgrass (Bromus tectorum) had a prefire frequency of 18%.
Of 20 annual forb species observed on the study area, only weevil prairie-dandelion (Nothocalais troximoides) with 13% prefire frequency and blue-eyed Mary (Collinsia parviflora) with 37% prefire frequency were found frequently enough before fires to be tested for significance. A total of 40 species of perennial forbs was observed. Perennial forb species tested for significance included Modoc hawksbeard (Crepis modocensis), longleaf phlox (Phlox longifolia), wild onion (Allium spp.), milk-vetch (Astragalus spp.), dwarf yellow fleabane (Erigeron chrysopsidis), and desertparsley (Lomatium spp.).
Plant response to prescribed fire was evaluated on 4 burned and 4 unburned plots in a Wyoming big sagebrush (A. t. ssp. wyomingensis) ecosystem. Four plots were chosen randomly for prescribed fire treatment. Plots were approximately 988 acres (400 ha) in size and located in the northeastern portion of Hart Mountain National Antelope Refuge. Elevation of the study plots ranged from 5,085 to 5,299 feet (1,550-1,615 m) with level topography. Soils were a cobbly clay-loam of the Ratto-Coglin complex. Mean annual precipitation at refuge headquarters was 11.42 inches (290 mm). Precipitation was 9.8 and 18 inches (249 and 456 mm) in 1997 and 1998, respectively.
The prescribed fire plots were ignited with a heli-torch September 23-28, 1997, utilizing strip-head or ring-fire ignition patterns. Ambient temperatures during fires ranged from 66 to 82 degrees Fahrenheit (18.7o-27.5oC), relative humidity from 17 to 24%, and wind speed from 4 to 6 miles h-1 (6.4 to 9.7 km h-1). Cloud cover was < 10%, with no precipitation for more than 2 weeks. Understory fuel moistures for the dead herbaceous vegetation ranged from 4.4-6.5% and moisture of 10-hour dead fuels from 5.5-8.0%. Flame height was 6.6 to 12 feet (2.0-3.7m), flame length 6.6 to 14.4 feet (2.0-4.4m), flame depth from 6.6 to 25.6 feet (2.0-7.8m), rate of spread ranged from 15 to 39.4 feet/min (4.6-12m/min), and residence time from 0.6 to 2.6 minutes.
Management objective of the prescribed burn was to ascertain effects of prescribed fire on Wyoming big sagebrush and implications for ecological restoration of sage-grouse habitat.
FIRE EFFECTS ON ANIMAL SPECIES AND HABITAT:
Prescribed fire created habitat areas with different species compositions on the landscape. Although structure was altered by the loss of sagebrush dominance, species composition of the burned plots changed very little throughout the study, and no significant differences were observed in alpha or gamma diversity. Frequency of none of the common herbaceous species changed significantly after prescribed fire.
Presence or absence of most species in the plots remained unchanged, but percent cover of species changed dramatically. Fire caused burn plots to have higher cover of annual forbs and sprouting herbaceous species than shrubs.
The 3 most abundant shrub species, Wyoming big sagebrush, spiny hopsage, and broom snakeweed are partially classified as avoiders. They were eliminated from areas that burned (with the exception of postfire sagebrush seedlings and a few sprouting hopsage individuals). Fire killed all sagebrush plants within burned portions of the treated plots (47 Â± 12% of the area). However, in burned areas, 49 to 297 sagebrush seedlings acre-1 (121-734 ha -1) were present the 1st postfire year. Although none were sampled in the transects, scattered spiny hopsage individuals were observed germinating, and spiny horsebrush (Tetradymia spinosa) seedlings were also observed. Number of reproductive shoots (257 vs. 80), vegetative shoots (510 vs. 149), and total shoots (767 vs. 229) per plant were significantly greater among plants along burn edges than among plants in unburned interior (Wilcoxon sign rank p=0.0078). Prescribed fire elevated the number of total shoots of sagebrush individuals along burn edges by 243 Â± 29% than sagebrush individuals in unburned interior.
Prescribed fire decreased overall cover of grasses (MANOVA, p=0.13). Cover of perennial grasses declined by 4% (9% in 1997 to 5% in 1998) in burned plots, while there was only a 1% change (10% in 1997 to 9% in 1998) in control plots (p=0.027). Burning had no significant effect on cover of tall grasses (< 2% decrease in burn vs. no change in control plots) or annual grasses (1-2% all treatments and years). Density of tall perennial bunchgrasses (2.7 m-2 in burn, 2.2 in control) in the 1st posttreatment year (1998) was not significantly different between burned and unburned control plots. Of 8 species of grasses observed, there was no significant difference between burn and control plots.
There were significant increases in the percent cover of forbs (forbs selected by sage-grouse, perennial and annual forbs) (MANOVA, p=0.012). Prescribed fire increased cover of annual forbs by 16% (3% in 1997 to 19% in 1998) in burned plots, while only a 5% increase (3% in 1997 to 8% in 1998) was observed in the control plots (p=0.003). No significant differences were detected in cover of grouse forbs or perennial forbs. Fire caused no significant changes in frequency of any annual or perennial forb species.
FIRE MANAGEMENT IMPLICATIONS:
Sagebrush cover on the study area (and in the surrounding area) was high (>25%) due to livestock grazing and fire suppression. There was little interspersion of other habitats in this "sea of sagebrush," yet sage-grouse populations on the refuge continue to decline. Thus, it is likely that on the study area sagebrush is not a limiting factor for sage-grouse populations. Reducing cover of sagebrush and increasing understory vegetation may bring the ecosystem closer to the historic conditions with which sage-grouse evolved.
Nesting habitat for sage-grouse may not be reduced for 3 reasons: Sage-grouse may have evolved with lower sagebrush cover; greater than half of the burned plots did not actually burn; and higher levels of cover exist along burn edges due to elevated vigor of sagebrush. As sagebrush seedlings within the burned areas mature and reproduce, they will begin to add to sage-grouse nest and hiding cover within burned areas. Additionally, with herbaceous cover along burn edges at least equal to control levels, and sagebrush cover along burn edges elevated, these burn edges may prove to be superior nesting habitat for sage-grouse.
Quality of sage-grouse wintering habitat after sagebrush removal treatment is directly related to the amount of sagebrush remaining . This prescribed fire treatment left > 50% (in an irregular mosaic pattern) of the treatment area with fully intact sagebrush cover (>25%). This cover, sagebrush in the control plots, and sagebrush surrounding the study area will likely provide more than adequate wintering cover.
A major danger in using prescribed fire for management of sage-grouse habitat is increasing the fire frequency beyond the rate at which the sagebrush component of the ecosystem can recover. If fire return intervals become frequent enough to exceed the capacity of sagebrush to repopulate, sagebrush cover would be reduced far below historical levels which would be very detrimental to sage-grouse.
Increases in percent cover of annual forbs will likely provide a rich forage base for pre-laying sage-grouse females and young chicks. Within the burned areas, greater forb cover will enhance feeding opportunities. Abundant food forbs in close proximity to unburned sagebrush cover could benefit sage-grouse broods by providing additional foods with adequate cover. Reintroducing prescribed fire to sagebrush ecosystems with "unnaturally" high sagebrush cover may improve habitat quality for sage-grouse by increasing forage quality and quantity, and providing greater overstory and understory cover along burn edges.
Some pronounced effects of prescribed fires occurred at the burn/unburn ecotone. Immediately after the fires the wind moved large quantities of soil and ash to downwind burn edges. Increased density of reproductive and vegetative shoots along edges may be partially a result of this additional soil and ash. Drastic increases in cover of grasses and forbs observed along some edges may be the result of high levels of soil and ash or decreased competition in the adjacent areas.
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