Young juniper trees are easily killed by fire primarily because of their small size, thin bark, and compact crown. Fire has long been recognized as a means to control this species because juniper does not resprout. Often young trees are killed just by scorching the crown and stem. As juniper ages, the bark thickens and the crown develops a bushy, open form. A hot fire can kill or severely damage such a tree, but the same tree may survive a cool fire. Low, spreading branches can provide a route for fire to enter the crown, thereby increasing the potential for damage. Often large junipers have survived a number of fires (four to six). The different effects of fire on young and old juniper trees are largely a function of the site. The species commonly occupies dry environments that support limited undergrowth. When surface fuels are sparse, fire damage is minimal.

Mature Douglas-fir is a relatively fire-resistant tree. Saplings, however, are vulnerable to surface fires because of their thin, photosynthetically active bark, resin blisters, closely spaced flammable needles, and thin twigs and bud scales. The moderately low and dense branching habit of saplings enables surface fires to be carried into the crown layer. Older trees develop a relatively unburnable, thick layer of insulative corky bark that provides protection against cool to moderately severe fires. Fire-resistant bark takes about 40 years to develop on moist (favorable) sites. This protection is often offset by a tendency to have branches the length of the bole. The development in the lower trunk of “gum cracks,” which streak the bark with resin, can provide a mechanism for serious fire injury. Dense sapling thickets can form an almost continuous layer of flammable foliage about 10 to 26 ft (3 to 8 m) above ground that will support wind-driven crown fires. Even small thickets of saplings provide a route by which surface fires can reach the crowns of mature trees.

Engelmann spruce is easily killed by fire. The dead, dry, flammable lower limbs, low-growing canopy, thin bark, and lichen growth in the branches contribute to the species’ vulnerability. The shallow root system is readily subject to injury from fire burning through the duff. Large old spruce may occasionally survive one or more light fires, but deep accumulations of resinous needle litter around their bases usually make them particularly susceptible to fire damage. Survivors are often subjected to successful attack by wood-destroying fungi that easily enter through fire scars. The high susceptibility of spruce to fire damage is mitigated in part by the generally cool and moist sites where it grows. Spruce seedlings will occur as members of a fire-initiated stand with lodgepole pine. Spruce’s shade tolerance allows it to establish and grow beneath a lodge-pole pine canopy. On sites where it is the indicated climax species, spruce will eventually dominate the stand, but it takes a long period without any fire before this can occur.

Western larch is the most fire-resistant conifer in the Northern Rocky Mountains. It possesses an insulating bark that can, in mature trees, range from 3 to 6 inches (7 to 15 cm) thick. The fire resistance of western larch is enhanced by its tendency to self-prune lower branches and its tolerance of defoliation. Western larch is a deciduous conifer and replaces its needles annually. Defoliation by fire is less traumatic for larch than for conifers that normally replace their needles at 2 or 3-year intervals. Western larch can become established rapidly on mineral soil exposed by fire. Its lightweight seeds can be blown from considerable distances to potential germination sites. A highly intolerant species, western larch requires full or near-full sun for best development. Lodgepole pine and larch are both potential seral dominants on many sites. Western larch is a better competitor where there is higher soil moisture. Western larch is long lived. Old fire-scarred tree stumps in the Seeley Lake area of western Montana indicate ages in excess of 900 years at the time of cutting.

Individual mature lodgepole pine trees are moderately resistant to surface fires. Lodgepole’s thin bark makes it susceptible to death from cambium heating. But lodgepole pine is alone in its ability to perpetuate itself on a site despite fire. Indeed, on most sites where lodgepole grows, fire is necessary for the species’ continued dominance. Lodgepole pine’s key fire survival attribute is cone serotiny. Most lodgepole stands in western Montana are composed of trees containing both serotinous and nonserotinous or open cones. The ratio of serotinous to nonserotinous cones seems to be related to the fire frequency for the site: the higher the fire frequency the greater the proportion of serotinous cones and vice versa. A temperature of 113 “F (45 ‘C) is usually required to melt the resin that binds the scales of a serotinous cane. Large quantities of highly viable seed are therefore available to regenerate a site following a stand-destroying fire. Other characteristics that contribute to the pine’s success in dominating a recently burned site are: early and prolific seed production, high seed viability, and survival, and rapid growth.

Whitebark pine is moderately fire resistant. It has a relatively thin bark and is susceptible to fire injury from hot surface fires that heat the tree’s cambium. The characteristically dry, exposed site and open stand structure tend to reduce whitebark pine’s vulnerability to fire. The fact that whitebark pine often reaches ages of 500 years or more reflects the reduced fire threat. Fires that burn in the undergrowth are usually of low-to-moderate severity. But the low, ground-hugging crowns of associated conifers can provide a fuel ladder, and downfall in the vicinity of mature trees locally increases crown fire potential. Hence, severe fires are possible. Severe wildfires starting in lower elevations can spread throughout the upper elevation forests to timberline. Although the open nature of a whitebark pine forest acts as a firebreak, many trees can be killed under these conditions. The most common fires are lightning fires that do not spread far. Regeneration on burned sites is usually the result of seed germination from bird and rodent seed caches, especially those of Clark’s Nutcracker.

Subalpine fir is rated as the least fire-resistant Northern Rocky Mountain conifer because of its thin bark, resin blisters, low and dense branching habit, and moderate-to-high stand density in mature forests. As a result, fire most often acts as a stand-replacement agent when it burns through a subalpine fir forest. Even ground fires can cook the cambium or spread into the ground-hugging branches and from there up into the crown. Subalpine fir can occur in a fire-initiated stand with Douglas-fir, lodgepole pine, and other seral species because it germinates successfully on a fire-prepared seed-bed. But subalpine fir usually remains a slower growing, minor component dominated by less tolerant species. Where a seed source exists, the fir will invade and grow in the understory of lodgepole stands. Given a long enough fire-free period, subalpine fir will overtop lodgepole pine on sites where it is the indicated climax.

Mountain hemlock is vulnerable to fire damage. It is only slightly more fire resistant than subalpine fir. Its thin bark affords some protection, but low-hanging branches, highly flammable needles, and a tendency to grow in dense groups make it susceptible to fire injury. Trees that survive fires often suffer subsequent mortality from fungus-infected fire wounds. Mountain hemlock grows in pure stands or in mixtures with a variety of species. In Montana, subalpine fir, Engelmann spruce, and whitebark pine are common associates. Mountain hemlock sites are typically moist with average annual precipitation over 50 inches (127 cm), making fire occurrence low. When these forests do dry, however, fires often burn severely. It is considered a coclimax species with subalpine fir where they occur together. Mountain hemlock seedlings and saplings survive prolonged suppression and respond well to release. The ability of mountain hemlock to act as a pioneer species apparently varies with locality. It is an invader of burned sites in the high-elevation forests of the Northern Rocky Mountains.

Western white pine is moderately resistant to fire. Its resistance is favored by medium thick bark, moderately flammable foliage, self-pruning of lower limbs, and especially, its tall stature. But, older trees retain abundant resin in their bark and often have lichen-covered branches. These factors, plus the often dense stand structure, reduce western white pine’s fire resistance. Young trees are especially vulnerable because of their compact stand structure and the lack of thickened bark. Western white pine is a fire species that depends on severe fires to recycle stands and create an early successional habitat. Its common occurrence in nearly pure, even-aged stands is further evidence of colonization after fire.

An individual, mature grand fir can resist low to moderately severe fires primarily because of its moderately thick bark. However, its low and dense branching habit, highly flammable foliage, heavy lichen growth, relatively shallow root system, and dense stand habit make it susceptible to fire injury and death. Fire resistance is strongly influenced by site. Grand fir succumbs to ground fire when the duff burns deeply enough to injure the root system. On relatively dry mountain slopes where grand fir grows, the deeper root system, lighter fuel loadings, and more open stand structure make it less vulnerable. However, decay frequently enters through fire wounds. Grand fir tolerates partial shading and is a successful invader of small openings and shrubfields. It can continue to establish in developing stands until the canopy closes.

Western hemlock is easily killed by fire because of its thin bark, shallow roots, highly flammable foliage, and low-branching habit. It tends to form dense stands and its branches are often lichen-covered, which serve to increase its susceptibility to fire damage. Postburn mortality of individuals is common due to fungal infection of fire wounds. The range of western hemlock in Montana is restricted to the northwest portion, where relatively warm, mesic conditions prevail. Except during especially long dry periods in summer, fire seldom burns these sites. Hemlock becomes a prolific seeder at an early age. It can be an aggressive pioneer because of its quick growth in full overhead light and its ability to survive under a wide variety of seedbed conditions. The light, winged seeds can be carried a considerable distance by wind. Hemlock is a highly tolerant climax species. It survives long periods of suppression and will respond well to release. It is often found as a codominant with western redcedar on climax or near-climax stands.

Western redcedar has only low to moderate fire resistance. Its thin bark, shallow root system, and low, dense branching habit make it susceptible to fire damage. Despite this apparent low resistance, the species often survives because of its large size and tenacity if any portion of the bole isn’t killed. Western redcedar is found in the mesic to hydric environments of western Montana—a region with a modified maritime climate. These moist sites provide redcedar’s best protection from fire. Riparian stringers of western redcedar may act as firebreaks. The generally moist duff found beneath redcedar does not readily burn. Redcedar is not an aggressive pioneer species because the succulent seedling is susceptible to high soil temperatures and is slow in root development. Seedling survival on burned or unburned mineral soil is best under partial shade.

Subalpine larch is a thin-barked species easily damaged by fire. However, it is moderately fire-resistant primarily because of its stand habit. It grows only on the highest elevations inhabiting extremely rocky and generally moist and cold sites. Alpine larch can grow in pure groves, in small groups, or as isolated individuals. In the lower portion of its elevational distribution, it occurs with subalpine fir, Engelmann spruce, and whitebark pine. In the timberline zone, fire is a cause of tree mortality but is less frequent and widespread than in contiguous forests below. Severe fires may enter the subalpine larch stands from lower forests. However, they do not always adversely affect subalpine larch stands. For example, northern Idaho’s severe Sundance Fire of 1967 swept the ridges of Roman Nose Mountain burning most of the whitebark pine and killing much of the spruce and fir in the cirques, but causing only minor damage to isolated stands of subalpine larch. Sparse vegetation and rocky slopes curtail the intensity of fire in these areas.

Big sagebrush plants are killed by most fires. Prolific seed production from nearby unburned plants coupled with high germination rates enables seedlings to establish rapidly following fire. Wind, water, and animal-carried seed contribute to regeneration on a site. Fire return intervals in big sagebrush are 5 to 70 years. Big sagebrush is readily killed when aboveground plant parts are charred by fire. If sagebrush foliage is exposed to temperatures above 195 degrees Fahrenheit (90oC) for longer than 30 seconds, the plant dies. In some areas, scattered unburned big sagebrush may survive, particularly where the soil is thin and rocky and where sparse herbaceous biomass limits the fire's spread. Big sagebrush does not resprout after fire. Because of the time needed to produce seed, it is eliminated by frequent fires. Big sagebrush reinvades a site primarily by off-site seed or seed from plants that survive in unburned patches. The rate of stand recovery depends on the season of burn, as season affects the availability of seed, postfire precipitation patterns, and the amount of interference offered by other regenerating plant species.

Foliage of big huckleberry is of low flammability, allowing for survival after low severity fires, with top-kill resulting from higher severity fires. Top-killed plants resprout from rhizomes. Plants subjected to regular fire intervals may be better suited to surviving fire than individuals developed under fire suppression. Plants are consumed by fire only when adequate fuels are present to dry and preheat stems and foliage. Seed is not an important postfire recolonization method and is rarely found in postfire areas. Historically, burning of big huckleberry patches by Native Americans was a regular activity. To enhance production, Tribes set fires in autumn after berry harvest. Fires reduced invasion of shrubs and trees. Fields of big huckleberry in the Pacific Northwest are considered a product of uncontrolled wildfires occurring before effective fire suppression.

Big sagebrush plants are killed by most fires. Prolific seed production from nearby unburned plants coupled with high germination rates enables seedlings to establish rapidly following fire. Wind, water, and animal-carried seed contribute to regeneration on a site. Fire return intervals in big sagebrush are 5 to 70 years. Big sagebrush is readily killed when aboveground plant parts are charred by fire. If sagebrush foliage is exposed to temperatures above 195 degrees Fahrenheit (90oC) for longer than 30 seconds, the plant dies. In some areas, scattered unburned big sagebrush may survive, particularly where the soil is thin and rocky and where sparse herbaceous biomass limits the fire's spread. Big sagebrush does not resprout after fire. Because of the time needed to produce seed, it is eliminated by frequent fires. Big sagebrush reinvades a site primarily by off-site seed or seed from plants that survive in unburned patches. The rate of stand recovery depends on the season of burn, as season affects the availability of seed, postfire precipitation patterns, and the amount of interference offered by other regenerating plant species.

Chokecherry is well adapted to fire. Although susceptible to top-kill by fire, it resprouts rapidly and prolifically from surviving root crowns and rhizomes. Seed germination improves with heat treatment, suggesting scarification by fire is an important adaptation. Postfire regeneration probably also involves the germination of off-site seed dispersed by mammals and birds. Fire often kills aboveground chokecherry stems and foliage, but it quickly resprouts, either the same year following a spring burn, or by the next growing season. Steve Arno hypothesized that relatively frequent fires set by Native Americans in western grassland and sagebrush communities, where chokecherry occurs, favored expansion of grasslands into adjacent shrub or tree communities. In recent times shrub and tree communities have developed in former grasslands due to fire exclusion and grazing.

Common juniper is susceptible to fire because it is not equipped with fire-surviving regeneration properties. The foliage is resinous and very flammable. Plants are generally killed or seriously damaged by fire. The degree of damage received increases with progressively greater fire severity. In some areas, older common juniper often survive fires of low severity. Patchy fires may allow individual plants to survive in protected areas such as on rocky cliffs. More rarely, portions of a lightly-burned plant may survive. Where common juniper is killed by fire, some seeds may survive in the soil on-site and germinate when conditions become favorable. Other seed is brought to the site by bird or, less commonly, mammal dispersers. These factors contribute to slow postfire reestablishment on many sites.

Common snowberry is classified as a survivor and has high resistance to fire. It is a rhizomatous species with rhizomes buried 2 to 5 inches (5-12.5 cm) deep in mineral soil. After fire has killed the top of the plant, new growth sprouts from these rhizomes. This rhizomatous growth response is highly variable and depends on conditions at specific sites. Regeneration from buried seed is favored by fires of low severity and short duration that remove little of the soil organic level. Among the first to recolonize a site after fire, growth of snowberry in the 1st postfire year varies, but is generally considered to be good. With light to moderate soil disturbance, reprouting will return common snowberry coverage in a year and common snowberry may produce fruit the 1st year.

Creeping juniper is subject to fire-caused mortality or damage, but limited evidence suggests that this species may be less susceptible to damage than many other junipers. The low mat-like growth form of creeping juniper results in poor air circulation near the plant, more limited fuels, and higher relative humidity around the crown, all of which serve to decrease flammability. Creeping juniper can grow on extremely rocky sites, which frequently lack sufficient fuels to carry a fire. Reestablishment after fire may occur in a number of ways. In areas where creeping juniper grows in large mats, parts of the mat may remain undamaged and survive. In many locations break-up of old mats is an important means of forming new individuals. This process is likely to be of at least some importance after fire in certain areas. Reestablishment after fire may also occur through seed buried on-site in the soil or brought on-site by water, gravity, or by any of a number of birds and mammals.

Sites where devil's club occurs burn infrequently. Typically, the moist ravines and streamside areas serve as a fire break to low and moderate-severity ground fires. The return interval for such fires ranges from 50 to 100 years in the western redcedar/devil's club type of western Montana. Less often, this type undergoes severe, stand-replacing fire, regressing the site to pioneer conditions. Stand-replacing fires in the western redcedar/devil's club type of western Montana have historically occurred at intervals ranging from 150 to more than 500 years. Devil's club adaptations to fire are not well documented. It may sprout from the root crown, and sprouting from rhizomes may also occur. But devil's club is probably absent from most burn sites for decades following stand-replacing fire. Presumably, devil's club establishes on these sites from animal-dispersed seed after the canopy has closed enough to shade this light-sensitive species.

Greene mountainash sprouts from deep-seated rhizomes and resprouts vigorously after fire.

Although the seed is generally viable, postfire regeneration of grouse whortleberry from seed is rare because germinants are fragile. The species relies on prolific rhizomes to survive fire. Following low- or moderate-severity fires that do not kill the shallow rhizomes, grouse whortleberry sprouts quickly and vigorously. The rhizomes occur in duff or at the duff-soil interface. Severe fires can eliminate this shrub from a site.

Kinnikinnick is a sprouting species best suited to short fire cycles with low fuel buildup and low fire intensities. It possesses latent buds on the horizontal stems and dormant buds on the stembase or root crown that allow sprouting of surviving plants or rooted stems. The crown of bearberry plants may lie just below the top of mineral soil, but as duff increases it migrates into the duff layer and becomes susceptible to fire. Bearberry's main roots extend into mineral soil, but it has been considered to be incapable of regeneration from the roots if the crown is killed. Since it can be propagated from root cuttings, it might be capable of regeneration from the roots under some circumstances. Bearberry may be a seedbanking species with fire resistant seed.

Lewis' mockorange is top-killed by fire, but the root crown usually survives and produces sprouts. Lewis' mockorange occurs in both forested environments which frequently experience fire and on rocky scree slopes which may not burn at all. In western Montana, Lewis' mockorange occurs in Douglas-fir habitat types that had historical fire frequencies of 5 to 45 years. The ability of Lewis' mockorange to sprout after top-kill by fire enables it to persist in these forests.

After a fire, mountain lover sprouts from surviving root crown and from buds along its taproot. Moderately resistant to fire kill. Some seedling establishment via short-term viablity seed stored on-site may also occur. Usually survives low to moderate severity fires that do not consume the duff and heat soil excessively. Usually increases after a fire.

Ninebark is classified as fire resistant and has been ranked in the highest fire-survival category in a western Montana study. It is, however, susceptible to death from severe fire temperatures. Roots may be damaged by moderate to severe fires. Often there is a decrease in aboveground parts following fire, subsequently delaying regeneration. Ninebark sprouts vigorously following fire. Sprouts originate from horizontal rhizomes, of which a high proportion are situated in mineral soil. Ninebark has 36 to 99 percent of its rhizomes buried in mineral soil, ensuring its potential for survival and sprouting following a fire. Indeed, Ninebark has been found to be more abundant on burned sites than on unburned sites.

Oceanspray is only moderately resistant to fire, but is well adapted to disturbance by fire. Although readily top-killed, this species is generally quite resistant to fire mortality. It survives fire by regenerating from soil-stored seed or sprouting from surviving root crowns. Its most common postfire regeneration stategy is vegetative regeneration. Generalized information indicates that postburn seedling establishment is rare, but seedling cover may be greater on high severity burns.

Pacific yew has thin bark and is sensitive to heat damage. Plants are generally killed by even light ground fires, and this species is almost always eliminated from burned stands. In western Montana, researchers observed that all plants were eliminated from burned stands. Hence, an abundance of Pacific yew can be equated with an absence of fire. Plants which occasionally survive fire do so because they occur in the wettest concavities, which are relatively unaffected by fire. Because Pacific yew is susceptible to heat damage, it is most often associated with forests characterized by long fire-free intervals. Fire is rare in many old-growth forests of the Pacific Northwest. Mature moist-site stands in which Pacific yew grows as scattered individuals are often considered relics from past fires. In parts of western Montana, the age of Pacific yew averages approximately 210 years where fire replacement cycles are estimated at 150 years. This suggests that the association of Pacific yew with moist microsites conveys some protection from fire. After fire, Pacific yew slowly reestablishes by means of bird-dispersed seed as the overstory canopy develops.

Prickly currant occurs in many forest types that are characterized by long fire free intervals punctuated by severe, stand replacing fires. Its ability to regenerate after fire from long lived seed stored in soil or from off site sources makes prickly currant fairly resilient to stand-replacing fire. Low-severity fire is probably more favorable to currants than severe fire. After fire currant canopy cover increases slowly, reaching a maximum density in several to many decades. Fire that burns the organic soil probably kills prickly currant. Researchers report that fire that removes the organic soil layer will likely kill the shallow root systems of most Ribes (currant and gooseberry) species. Prickly currant nearly disappeared from study sites after a severe prescribed fire in central Idaho. Low severity fire probably top kills prickly currant. Seeds contained in the organic mantle are destroyed by severe fire. However, seeds buried in mineral soil probably survive most fire.

Red-osier dogwood is considered to be a semi-fire-tolerant, seed-banking species. Aboveground foliage of red-osier dogwood is usually killed by fire. However, the roots will survive all but the most severe fires that remove the duff and heat the upper soil for extended periods. The plant is able to sprout from the surviving roots or stolons and from the base of aerial stems following fire. It can be killed by severe fires that cause extended heating of the upper soil. Light fires that partially remove the duff stimulate germination of buried seed. In a northern Idaho grand fir (Abies grandis) forest seed bank study, red-osier dogwood seed was found in the top 2 inches (5 cm) of soil; however, viability was low (4%). In another postfire soil germination study, all red-osier dogwood plants were sprouts from root fragments.

Russet buffaloberry is normally fire resistant but can be eliminated by fire. As a result it is classified as moderately resistant to burning. Sprouting from surviving root crowns and establishment from seed transported from off-site allow russet buffaloberry to survive fire. As fire suppression culminates in closed-canopy, old-growth forests, fire generally increases russet buffaloberry density and vigor, although full benefits may not be realized for at least 25 years. Following a Montana wildfire, regrowth of buffaloberry was slow; 4 to 5 years were required for 25 percent of the eventual crown size to be obtained. Recurrent, low-intensity ground fires are closely linked to maintaining russet buffaloberry density and vigor in stands with lodgepole pine and quaking aspen overstories and dry upland meadows where it dominates the shrub layer.

Menziesia is very susceptible to fire-kill and is considered a fire-sensitive species. Moderate to severe fires reduce survival and slow redevelopment. Wildfires apparently removed menziesia totally from areas in Washington and Oregon for up to 16 years. It responds to fire by sprouting from the root crown. Since menziesia is indicative of cool, moist sites, fire plays a minor role in its development.

Willows are greatly favored by fire in most habitats. As a survivor and off-site colonizer, Scouler willow is abundant following fire and has a moderate regeneration period. It is adapted to fire by rapidly resprouting from the root crown, and establishes from seed on severely burned sites. Wind dispersed seeds facilitate rapid recolonization of burned areas. In a north-west Montana study Scouler willow was found on 80% of burned sites with no previous Scouler willow presence. Stand replacing fires favor regeneration of Scouler willow, and good response from Scouler willow seedlings can be expected on sites where fire damage is thorough enough to expose mineral soil. However, it is rarely present on sites where more than 50% of the prefire overstory remains.

Shrubby cinquefoil is susceptible to damage by fire; however, if the root crown remains undamaged individual plants readily resprout. Shrubby cinquefoil also re-establishes from off-site seed sources. The fibrous bark of shrubby cinquefoil results in very flashing, high intensity fuel. The high density of shrubby cinquefoil growing in pure stands (up to 7,500 plants/acre or 18,750 plants/ha) may increase fire spread and intensity; when growing in conjunction with shrubby cinquefoil, bunchgrasses may contribute to shrubby cinquefoil's flammability. Fire occurs infrequently on many shrubby cinquefoil sites; some areas are too moist to carry fire. Other sites, such as talus slopes, may lack sufficient fuels to carry fire.

Sitka alder is generally favored by fire. It often increases in frequency and extent in the early seral communities that follow a fire. Although aboveground plant parts may be killed by fire, plants usually recover by sending up several new shoots from their root crown, which often increases stand density. Numerous wind-dispersed seeds are produced by off-site plants and on-site plants. The seeds quickly colonize soils exposed by fire, and seedlings often become an important part of the first postfire generation. Fire tends to occur infrequently on the moist sites occupied by Sitka alder communities. However, sitka alder's frequency and extent increase rapidly in early successional communities following fire that do occur. The nonflammable bark and nonresinous leaves protect alders somewhat from low intensity fires.

Snowbrush ceanothus is promoted by fire. It establishes from seed and sprouts from the root crown after fire. Postfire recovery can be expected within 2 to 5 years in the Intermountain region.The plant usually increases following fire, often dramatically. Snowbrush ceanothus seedlings often appear on sites following fire where it was previously uncommon or not present. Snowbrush ceanothus burns quite hot. The foliage contains volatile oils that may contribute to fire hazard. Snowbrush ceanothus has dormant, ground-stored seed that requires heat treatment to germinate. Where its seeds are present in the soil, snowbrush ceanothus may dominate early seral growth following a medium or hot fire. It also sprouts vigorously from the root crown after fire. Fire creates conditions more favorable for snowbrush ceanothus growth by removing the overstory. When conifers overtop the shrubfields, snowbrush ceanothus may die out because of reduced light intensities in the forest understory. As a nitrogen fixer, snowbrush ceanothus plays an important role in nitrogen reaccumulation following fire.

Thimbleberry is resistant to and generally enhanced by fire. In areas of rigorous fire suppression, thimbleberry fruit production and plant vigor has declined. This species is well-adapted to vigorously invade many types of burned sites through rhizomes or seed. Rhizome sprouting is an important post-fire strategy that enables rapid reestablishment and spread. Thimbleberry, a seed banker, also reestablishes through viable seed stored in the soil or duff. Birds and mammals add to seedling establishment by transporting seed to the site. Thimbleberry typically becomes abundant within the first few years after fire and remains prominent during the early post-fire decades. Research suggests that thimbleberry may be well-adapted to the high nutrient availability and low competition from other species found immediately after burning, but is less successful once other species have reestablished. This fire-adapted species typically declines as the overstory develops in postfire communities.

Fire often injures Utah honeysuckle and results in temporary reductions in cover and frequency. Utah honeysuckle sprouts from the root crown after top-kill by fire. For some of the communities that Utah honeysuckle occurs in, such as grand fir/queencup beadlily in northwestern Montana or mixed-conifer subalpine forests of the southern and central Rocky Mountains, fire-free intervals or stand-destroying fires occur on average every 150 years.

Western serviceberry in forests is fire dependent and declines with fire exclusion. It may persist in the understory for decades, but eventually dies out with canopy closure. Through time series photographs, researchers have documented decline of serviceberry in ponderosa pine habitat types in the Northern Rocky Mountains due to canopy closure with fire exclusion. Serviceberry sprouts from the root crown and/or rhizomes after fire. Because serviceberry sprouts from existing plants, fire is not likely to alter its frequency unless plants were in poor condition before fire. After light to moderate severity fire, it usually sprouts from the root crown or from shallowly buried rhizomes. However, deeply buried rhizomes enable serviceberry to sprout after even the most intense wildfire. For example, the Sundance Fire of Aug. 23, 1967, on the Kaniksu National Forest of northern Idaho was an intense, running crown fire that reached firestorm proportions in the Pack River Valley. Serviceberry sprouts were a principle component of Pack River Valley vegetation at post-fire year 1, with 12 percent frequency and 4 percent cover. Seedling establishment is apparently not an important post-fire regeneration strategy.

White spirea, almost always top-killed following fires of moderate to high intensity, is highly resistant to fire-kill. It resprouts from surviving root crowns, and from rhizomes positioned 2 to 5 inches (5-13 cm) below the soil surface. White spirea demonstrates high survival capabilities following holocaustic wildfires. It is a rhizomatous shrub that not only survives burning, but can often flower the year immediately following the burn. Researchers have found white spirea to increase in cover and frequency following disturbance by fire. In fact, white spirea was found to increase in canopy cover 3 to 5 years after a burn.

Arrowleaf balsamroot is top-killed by fire. After a burn, the plant regenerates from its caudex (the term caudex refers to the woody base of an otherwise herbaceous perennial plant). It then regenerates from windborne seed or, more commonly, from rapid regrowth from the caudex. Arrowleaf balsamroot can survive even the most severe fires and will increase in frequency and density after fire. It is classified by some as one of the most fire resistant forbs.

Heartleaf arnica is top-killed by fire, but rhizomes often survive. A rhizome is a creeping plant stem (not a root) growing beneath the surface. Heartleaf arnica is rated as susceptible to intermediate in resistance to fire damage. This probably varies according to how far below the soil surface rhizomes are buried and how severe the fire is—the plant is apparently reduced by high intensity fires. It is best described as moderately fire resistant. In addition to sprouting from rhizomes, it also regenerates from wind-dispersed seed and from seed resulting from mass flowering, which often occurs 1 or 2 years after a fire. This is typically followed by a decline in cover and frequency within a few years.

Conspicuous aster is moderately resistant to fire, typically sprouting from surviving rhizomes. While conspicuous aster is top-killed by fire, rhizomes usually survive light- to moderate-severity fires that do not cause excessive soil heating. A rhizome is a creeping plant stem (not a root) growing beneath the surface. After fire, conspicuous aster also regenerates from wind-dispersed and soil-stored seed. Growth is stimulated after fire, resulting in mass flowering in the first few post-fire years. The extent of this flowering is directly related to pre-burn abundance and post-fire survivorship.

Conspicuous aster is moderately resistant to fire, typically sprouting from surviving rhizomes. While conspicuous aster is top-killed by fire, rhizomes usually survive light- to moderate-severity fires that do not cause excessive soil heating. A rhizome is a creeping plant stem (not a root) growing beneath the surface. After fire, conspicuous aster also regenerates from wind-dispersed and soil-stored seed. Growth is stimulated after fire, resulting in mass flowering in the first few post-fire years. The extent of this flowering is directly related to pre-burn abundance and post-fire survivorship.

False Solomon’s seal sprouts from surviving, stout creeping rhizomes. It is moderately resistant to fire-kill but may be killed by severe fires that remove the duff and heat soil excessively. Usually it maintains its pre-fire frequency.

Broadleaf arnica is susceptible to firekill. It will usually survive cool to moderately severe fires and may exhibit rapid initial regrowth accompanied by heavy flowering and seeding establishment. It sprouts from surviving rhizomes that creep laterally in the soil.

Mountain death camas sprouts from surviving tunicated bulb and is resistant to fire-kill.

Mountain sweetroot has short shallow roots and barbed, dispersed seeds. It is moderately fire resistant and temporarily increases after a fire.

Prince's pine is a fire-sensitive species that is very susceptible to damage and often shows a strong decline following fire. Survival probably depends to a great extent on damage to rhizomes, so survival of the plant depends on depth of rhizomes, fire severity, and consumption of duff. Loss of the long-lived evergreen leaves may also reduce survival. Postfire vegetative recovery depends primarily on the survival of scattered individuals in undisturbed microsites.

Fire top-kills or kills queencup beadlily. The plant is considered an onsite survivor that regrows from underground rhizomes. The extent of damage inflicted on queencup beadlily depends on several factors including root and rhizome depth, fire severity, and whether the plant is rooted in soil or organic material. Fires with high degree of soil heating, long durations, or those that occur in areas with low moisture content can cause greater mortality. The plant typically declines in frequency and coverage due to fire. Declines can be small and short lived.

Sidebells shineleaf sprouts from surviving rhizomes that grow mostly in the duff or at the soil surface. It is susceptible to fire-kill. Coverage is frequently reduced following a fire. It may survive cool fires when duff moisture is high.

Spreading dogbane sprouts from surviving rhizomes. It generally maintains its pre-fire frequency following a fire.

Sweetscented bedstraw is moderately resistant to fire. Top-killed by low-severity fires, it increases rapidly immediately following fire, then decreases over time. It typically germinates from seed and sprouts from surviving rhizomes following a fire. The bristly seeds may be carried limited distances by animals, aiding in colonization of recently disturbed sites.

Timber milkvetch sprouts from buds along surviving roots that may be 2 to 8 inches (5 to 20 cm) below the root crown. Resistant to fire-kill, it can regenerate even when the entire plant crown is destroyed. Timber milkvetch can send up shoots and set seed the first year. It may increase dramatically following fire. Milkvetch is poisonous to sheep and cattle.

Virginia strawberry sprouts from surviving (runners) at or just below soil surface. It is susceptible to fire-kill but will often survive cool fires that do not consume the duff because of high duff-moisture content.

Fire top-kills wild sarsaparilla; vegetative and reproductive buds are destroyed. Surviving rhizomes sprout and vigorously grow following fall or spring fires. New rhizomes are produced. Flowers are not initiated during the first growing season following fire. Very few wild sarsaparilla come in as seed immediately following fire. Wild sarsaparilla has been classified as a decreaser. It initially decreases in frequency and biomass following fire. The amount of decrease depends on fire intensity and time of burning.

Elk sedge has a high degree of resistance to fire because of its ability to resprout from underground rhizomes. After a fire in a lodgepole pine forest in Yellowstone National Park, elk sedge plants that had been top-killed and reduced to brown stubble patches produced new shoots the next year from rhizomes and roots that survived the fire. Elk sedge is often one of the first species to recolonize or grow back after a fire because it is able to resprout from underground rhizomes or recolonize from seeds stored in soil. Elk sedge is generally slower to recover after severe burns than after lower intensity fires. Some researchers report that elk sedge cover decreases after severe or relatively intense fire and imply that some plants are killed by fire. Elk sedge often increases or invades after a fire, sometimes flowering and producing seed the year after a fire. However, the ability of elk sedge to recolonize or regrow after a fire seems to depend largely on severity of the fire.

Idaho fescue is a small bunchgrass that can survive light severity fires. It is usually harmed by more severe fire. It grows in a dense, fine leaved tuft. Fires tend to burn within the accumulated fine leaves at the base of the plant and may produce temperatures sufficient to kill some of the root crown. Mature Idaho fescue plants are commonly reported to be severely damaged by fire in all seasons. Initial mortality may be high (in excess of 75%) on severe burns, but usually varies from 20 to 50%. Idaho fescue is commonly reported to be more sensitive to fire than bluebunch wheatgrass; however some researchers, using special instrumentation to control the intensity and duration of fire treatment for individual plants, suggested the latter was more sensitive. Fires burning at 10- to 25- year intervals have neutral to negative effects on Idaho fescue.

Prairie Junegrass is reported as showing little or no damage to moderate damage from fire. Perennial grasses possess growing points insulated near or below the soil surface. The small stature of prairie Junegrass and coarse textured foliage aid in protection of these meristimatic tissue areas. Possessing coarsely textured foliage and a small clump size also limits the potential for fire damage. Coarse grasses like prairie Junegrass burn quickly, transferring little heat below the soil surface. Fire survival strategy for prairie Junegrass is based upon seed germination and residual plant survival. The extent of damage or benefit imposed by fire is highly variable. Response can vary according to fire severity, physiological state of plant, soil moisture, and season of burn. Prairie Junegrass is usually top-killed or killed by fire. Fast-moving, low-intensity fires will consume above ground vegetation without damaging the plant's crown. In general, late-spring burns are more damaging to prairie Junegrass than early-spring, late-summer, fall, or winter burns.

Pinegrass is usually top-killed by fire. Fires that consume the duff layer may kill pinegrass rhizomes. In the northern Rocky Mountains, pinegrass is seldom, if ever, eliminated from a site even after severe wildfire. Pinegrass sprouts from rhizomes following fire. Rhizomes are buried in the top 2 inches (5 cm) of mineral soil, allowing the plant to survive fires that do not completely consume the duff layer. Pinegrass is seldom, if ever, eliminated from a site even after severe wildfires. Throughout its range, repeated fires promote increased cover in pinegrass and often result in its early postfire dominance. Pinegrass seedlings establish on burned sites from off-site sources, and pinegrass undergoes mass flowering in the years immediately following fire, allowing for rapid postfire colonization. Historically, pinegrass stands have perpetuated surface fires that maintained open stands of ponderosa pine.

Ross' sedge is resistant to fire. It survives fire through buried seed, which is viable over the long-term. The seeds germinate after heat treatment. It also regenerates through rhizomes. Recovery is rapid to moderate, taking 2 to 10 years to return to preburn frequency. Ross' sedge increases after fires that heat the soil but do not completely consume duff. After the Sundance Fire of northern Idaho, Ross' sedge was one of the most widely distributed plants and increased for four years following the fire. At some sites, Ross' sedge may not be part of the pre-fire vegetation but may exist as residual seed in the ground awaiting fire to create the proper germination conditions.

Rough fescue appears to be well adapted to periodic burning. The dense, tufted habit of rough fescue makes it resistant to light fire. The primary post-fire survival strategy of rough fescue is through the resprouting of surviving residual plants and from off-site wind-dispersed seed. Although plants are initially top-killed, recovery of pre-fire coverages and herbage production is usually attained in 2 to 3 years. Susceptibility to fire is related to fire severity, frequency, and season. Where reduced fire frequencies have produced large-diameter bunches with heavy litter build-ups, survival may be severely inhibited, as crowns tend to continue burning long after passage of the flame front. Fire frequencies in the range of 5 to 10 years may best maintain rough fescue.

Blue wildrye can survive fire. It typically forms small bunches that rarely exceed 4 inches (10 cm) in diameter, and mature aboveground growth generally consists of coarse leaves and stems. These attributes suggest that this bunchgrass burns rather quickly, with little heat transferred down into the root crown. As a result, basal buds located at or just below the ground surface are not subjected to prolonged heating, and may survive and resprout. Because blue wildrye is a short-lived perennial that generally does not compete well with surrounding vegetation, severity and frequency of fire or other types of disturbance greatly influence the recovery and maintenance of this species. In northern Idaho, the highest frequencies of blue wildrye occur on sites that have been subjected to multiple burns 2 or more times in the previous 30 years.

Needle-and-thread grass is top-killed by fire and sprouts from the caudex following fire, if heat has not been sufficient to kill underground parts. It may be killed if the above-ground stems are completely consumed. Needle-and-thread grass in sagebrush ecosystems is classified as slightly damaged by fire, and in Intermountain rangelands, as severely damaged. Burning in June can kill more than 90% of needle-and-thread grass plants, while burning in July kills only 20%. Needle-and-thread grass' dense culms, with a lot of dead material, will continue to burn after the fire has burned over the stand; resulting temperatures can be lethal to underground parts.

In the Pacific Northwest, timber oatgrass is moderately resistant to fire (having a 35 to 64% chance that at least 50% of the population will survive or reestablish after fire). Postfire regeneration occurs through seed and recovery is generally complete within 5 to 10 years. In a study in Washington state, levels of timber oatgrass and other grasses were not affected immediately after fire in a timbered area. However, several grasses, including timber oatgrass, began to increase 2 years after the burn. By the 5th year after fire, timber oatgrass was the dominant grass on burned plots. Two seasons after a May burn in northwestern Montana, timber oatgrass cover increased by 7.5% over preburn levels.

Tufted hairgrass generally survives all but the most severe fire. It usually sprouts from the root crown after aerial portions are burned. Tufts formed by the leaves often protect basal buds from fire damage. Tufted hairgrass seeds occur in the seedbank; after fire tufted hairgrass may regenerate from soil-stored seed.

Sweetgrass has creeping rhizomes that are often fairly deep and that may sprout after aerial portions are burned. Culms arise from among dead foliage of the preceding year. This foliage may protect basal buds from fire damage in the spring when moisture content of dead foliage is high. But in fall, it is more likely that the buds would be damaged by heat produced when the dried foliage burns.

In general, ticklegrass increases in abundance in response to fire. Wind-dispersed ticklegrass seeds readily colonize bare mineral soil on recently burned sites. Seeds may also be stored for short durations in the soil, allowing for early establishment of areas burned in the spring. Annual spring burns in aspen stands in Alberta caused an increase in ticklegrass inflorescence production. In unburned areas, there was an average of one flower head per square foot (10/sq m), but on burned sites 10 flower heads per square foot (110/sq.m) were produced.

Fire will kill aboveground vegetation of bluejoint reedgrass. Bluejoint reedgrass sprouts from on-site surviving rhizomes following fire. It can also establish on burned sites by wind-dispersed seeds. Severe fires will kill belowground rhizomes. Buried or wind-dispersed seeds may be the primary source of plant establishment on severly burned sites.

In this zone, naturally occurring fire will maintain grasslands, open stands of Douglas-fir or ponderosa pine, and prepare seedbeds. Frequent fires in seral stands maintained a ponderosa pine stand by killing fire-susceptible Douglas-fir seedlings. In this role, fire frequency largely determined the stand composition. Following a prolonged fire-free period, Douglas-fir regeneration became established beneath the canopy. A ground or surface fire that reached a thicket of saplings and small poles could ascend into the overstory, killing or injuring adjacent mature trees through the vegetative fuel ladder. During periods of high fire danger, this often resulted in a stand-destroying fire. Historic fire frequency was from 5 to 25 years between fires. Successful supression of surface fires in open fire-maintained stands over the last several decades has increased the potential for a fire to become severe.

Under natural conditions, fire occurred less frequently within this zone than it did within ponderosa pine habitat types or within the warmer Douglas-fir habitat types. The relatively light fuel loads, sparse undergrowth, and generally open nature of the stands would appear to favor long fire-free intervals. However, some researchers estimate a mean fire interval of 35 to 45 years in presettlement stands in southwestern Montana. Fire’s role in seedbed preparation is confounded by the difficulty of regeneration to progress beyond the seedling stage on these droughty sites because of undergrowth and overstory competition. Where dense regeneration does occur, fire probably played a role as a thinning agent in sapling and pole-sized stands. Ground fire probably maintained many mature stands in an open, parklike condition. Many presettlement stands were actually maintained as seral grasslands with scattered trees inhabiting rocky microsites. The prolonged absence of fire has allowed many of these groves to become forest stands.

Fire history studies in this zone in southwest Montana show mean fire intervals ranging from 15 to 42 years for presettlement stands. Fire was an important agent for controlling density and species composition. Low to moderate severity fires converted dense stands of pole-sized or larger trees to a more open condition, and subsequent light burning maintained stands in a parklike state. Frequent low or moderate fires favored larch and ponderosa pine over Douglas fir in stands where these species occurred. Severe fires probably occurred on dense, fuel heavy sites (like that shown at right) and resulted in stand replacement. Stand-replacement fires favored lodgepole pine on sites where it was present. Fire has a demonstrable effect on wildlife habitat through its effects on food plants. The combination of opening up stands by killing overstory trees, reducing competition by removing understories and rejuvenating sprouting plants through top kill, can significantly increase the availability of palatable browse and forage. Fire’s role as a stand-replacement agent becomes more pronounced when the natural fire-free interval is increased though fire suppression, unless corresponding fuel reduction occurs.

On sites below 7,500 feet, the role of fire in seral lodgepole forests is almost exclusively as an agent that perpetuates or renews lodgepole pine. Without periodic disturbance, the shade-tolerant species replace lodgepole because it does not regenerate well on duff or in shade. Fire interrupts the course of succession and increases the proportion of lodgepole with each burn. Within 50 to 100 years following a severe fire in a lodgepole-dominated stand, a reestablished lodgepole forest will exist even though shrubs and herbaceous cover may become dominant immediately following the burn. Large-scale stand-replacing fires play a major role in the ecology of lodgepole pine stands. The natural periodicity of severe fires in seral lodgepole stands probably ranges from less than 100 years to about 500 years. Recurring low-intesity fires may thin the stand or otherwise rejuvenate it without doing serious damage. However, in stands greater than 60 to 80 years old, fuels build up to a hazardous level due to natural thinning, mountain pine beetle outbreaks, dwarf mistletoe infestations, and fire-killed timber from previous fires. Eventually, a chance ignition sets off a fire that can cover thousands of acres.

Almost 60 percent of the mature western Montana subalpine fir-beargrass stands show evidence of ground fire. The occurrence of periodic low- to moderate-severity fire favors Douglas-fir and lodgepole pine. These fires set back invasion by the more tolerant subalpine fir and spruce, which in the absence of fire form dense understories and eventually take over the site. Fires of moderate severity probably help Douglas-fir maintain a position of dominance or codominance with lodgepole in many stands. The more fire-resistant Douglas-fir has a better chance of surviving these fires and is able to successfully regenerate in fire-created openings where mineral soil has been exposed. Severe, stand-destroying fire will generally favor lodgepole pine on many of these sites. Some large, thick-barked trees will often survive fires severe enough to kill all the lodgepole pine trees, thereby assuring the presence of Douglas-fir in the new stand.

The average fire-return interval for these sites in western Montana varies. In the upper Flathead (Coram) it is about 128 years. The impact fire has depends on stand condition and species composition. The general absence of spruce, subalpine fir, or mountain hemlock climax condition is evidence of disturbance by past fires. The dominance of lodgepole pine, Douglas-fir, larch or spruce on may sites suggests these stands developed on a fire-created mineral soil seedbed. Frequent moderate to severe fires may be restricted in their occurrence because many mature stands have an overstory that includes fire-sensitive spruce and lodgepole.

When it comes to forest development, fire on these sites is secondary to climate, soil, and other site factors. The cold moist, rocky, snowbound, unproductive, and otherwise fire-resistant environment that characterizes many of the sites not only makes fires infrequent but severely limits their extent. Lightning does ignite fires, but the paucity of continuous fine surface fuels coupled with the rain that commonly accompanies thunderstorms usually limits fire spread and severity. Historical fire frequencies ranging from 35 to 300 years have been reported for individual sites. In more continuous forests of this group, the most pronounced fire effect is to produce stand-replacing fires at long intervals (200 years or more). Stand-destroying fires are most likely to occur during extended drought conditions when severe wind driven crown fires develop in the forest below and burn into the upper subalpine and timberline forests. Vegetation recovery following these fires is usually slow because of the climate and extremely short growing season.

The relatively warm, moist conditions that sustain the growth of these diverse and highly productive stands keep fire frequency generally low. A fire may burn into the edge of a stand, possibly scarring some trees, but it will usually die out when it reaches the moist duff layer. Occasionally these stands are hit by severe summer drought, which can set the stage for severe, widespread fires. Stands are replaced and sites revert to pioneer species.