Wildland Fire Management Plan Craters of the Moon National Monument, Idaho

Appendix F - Vegetation Type Descriptions

Mountain Big Sagebrush

Mountain big sagebrush, in combination with several species of grasses which dominate the understory, is the most widespread of all vegetation types found on the monument, comprising 63% of the vegetated area. North of the highway, it occurs with bluebunch wheatgrass, Sandberg bluegrass, downy brome, bottlebrush squirreltail, and antelope bitterbrush. There, its occurrence is highly variable with respect to slope, aspect, and elevation. Idaho fescue is found on loess soils but does not occupy sites developed from recent cinder material.

Mountain big sagebrush intermixed with rubber rabbitbrush and green rabbitbrush with an understory of Sandberg bluegrass and the needlegrasses are prevalent in the southern portions of the monument, particularly in the Little Prairie area, around Echo Crater, and on Carey Kipuka. In the latter area it is often mixed with Idaho fescue and junegrass. In many areas in the southern portion of the monument, the mountain big sagebrush is a common associate in limber pine communities.

Of the sagebrush species, mountain big sagebrush is one of the best adapted to fire. It establishes readily following fire. Its seeds germinate more readily following a heat treatment than if untreated (Chaplin and Winward 1982). The plants grow rapidly and reach reproductive maturity within 3 to 5 years. Sagebrush may return to preburn levels within 15 to 20 years if sagebrush seedlings successfully establish the first year. If not, it may require 30 to 50 years for sagebrush to fully occupy the site (Blaisdell et al. 1982, Bunting et al. 1987). Observation of past burned sites on the monument indicate that sagebrush probably takes longer to return to preburn levels on the young cinder soils. There, we estimate that more than 75 years are required for the sagebrush to reoccupy the site.

Herbaceous productivity normally increases following fire in mountain big sagebrush vegetation (Harniss and Murray 1978, Uresk et al. 1980, Tisdale and Hironaka 1981, Johnson and Strang 1983, Blaisdell et al. 1984). Most perennial grass species such as bluebunch wheatgrass, bottlebrush squirreltail, Indian ricegrass, Great Basin wildrye and western needlegrass are well adapted to withstand fire. Productivity may be reduced the first year following fire if the fire was severe. Herbaceous productivity will remain at higher levels until the shrubs re-establish on the site. Initially forbs will dominate the site following fire (Kuntz 1982). Perennial grasses will gradually increase and dominate. If substantial perennial grass exists on the site at the time of the fire, forbs may dominate for only 1 or 2 years. At lower elevations and on more xeric sites, annual grasses such as cheatgrass may initially dominate if post-burn coverage of perennials is low. This could occur in sagebrush communities on cinder derived soils because these soils are more xeric than most typical soils of this vegetation zone. There are few native annual grasses common to this zone, however, annual forbs such as blue-eyed Mary, slenderleaf collomia, cryptantha, mentzelia and monkey flower may also increase greatly during this period until perennials dominate the burned site. Annuals may dominate the site for 5 to 10 years following the fire.

If these communities are not burned periodically, sagebrush cover will continue to increase. Potential cover of mountain big sagebrush may exceed 40%, which is greater than most other sagebrushes of the Artemisia zone (Bunting et al. 1987). Increasing sagebrush cover will suppress the herbaceous productivity in the understory. In particular, many of the forbs will be diminished and may disappear from the site. Some of these species may remain on the site through seeds stored in the soil seedbank. Severity of fires in dense old sagebrush is greater than those in stands of low sagebrush cover. This increases the direct impact of the fire on the herbaceous species and reduces the number of viable seeds stored in the soil.

Diversity of the community is probably greatest within a few years post-burn and gradually declines as the sagebrush stand develops. The increase in diversity is caused by the temporary increase in forbs within the community. Some grasses such as western needlegrass may also increase rapidly during the initial years after the fire.

Antelope bitterbrush is common within this vegetation type and may be greatly reduced in density by the fire. Bitterbrush density is reduced 50% on the average but variation between stands is high (Bunting et al. 1985). Murray (1983) found that in eastern Idaho, bitterbrush would remain below preburn levels for over 30 years. It appears from observations of old burns on the monument that bitterbrush may recover more rapidly than sagebrush on the cinder soils. An area near Coyote Butte was burned by a wildfire in the 1940s. Bitterbrush has repopulated the site but mountain big sagebrush is still absent. It is likely that bitterbrush can tolerate these infertile harsh sites better than sagebrush. Bitterbrush is often observed as one of the pioneer plants that invade onto new road cuts and other severely disturbed sites.

Three-tip Sagebrush

Three-tip sagebrush vegetation types occur primarily on the Carey Kipuka and on areas north of the highway. In the north it is found on northeast slopes of Little Cottonwood Canyon. Idaho fescue is a co-dominant in this type. Bluebunch wheatgrass and Hoods phlox occur less frequently in this type.

Three-tip sagebrush has been reported to sprout following fire (Pechanec et al. 1965, Morris et al. 1976). The ability to resprout varies, however, which indicates that several ecotypes exist (Hironaka et al. 1983). Our experience with the populations of three-tip sagebrush in the CRMO region has shown that it has only moderate resprouting potential and that reduction in abundance of the species usually occurs following fire. The herbaceous plants such as bluebunch wheatgrass, western needlegrass and Idaho fescue will gradually increase in density when the canopy of the sagebrush is opened. Recovery of the sagebrush stand will probably take 25-40 years to reach preburn levels. If few perennial grasses are present prior to the fire, cheatgrass may invade the site following disturbance (Hironaka et al. 1983).

Without periodic fire, three-tip sagebrush will gradually increase in density and cover. It appears that maximum coverage for the species is approximately 25 to 30% (Daubenmire 1970, Bunting et al. 1987). Productivity of the herbaceous component will be suppressed by the relatively high coverage of the sagebrush.

Low Sagebrush Communities

Low sagebrush occurs exclusively north of the highway. It is typically found on bare ridgetops on either side of Little Cottonwood Canyon. The herbaceous component is usually diverse but sparse. Due to low productivity, these sites are difficult to burn and may sometimes be used as firebreaks. Care must be taken in years with greater than average production when these communities may be capable of carrying a fire (Bunting et al. 1987).

Sandberg bluegrass is usually abundant with stonecrop and Hoods phlox in lesser quantities. A small amount of low sagebrush with an understory of Idaho fescue, Hoods phlox and bluebunch wheatgrass is found in the extreme northwest corner of the monument on northwest facing slopes.

Low sagebrush does not resprout and is easily killed by fire. Sagebrush cover does not tend to increase greatly in the absence of fire and is normally less than 13% at CRMO. Recovery of low sagebrush following fire is slow and may require 25-50 years to reach preburn levels.

Antelope Bitterbrush

Plant communities dominated by antelope bitterbrush are well distributed throughout the central portions of the monument. Major occurrences of this type can be found in the vicinity of Big Cinder Butte. In most locations it is associated with young cinder substrates and is one of the initial species to occupy this material. Generally the dominant, antelope bitterbrush is associated with considerable amounts of rubber rabbitbrush. In areas where succession is more advanced, mountain big sagebrush and wax current are important associates. Bluebunch wheatgrass, downy brome, Indian ricegrass and several forbs make up the understory. In some distinct but widely scattered areas, Great Basin wildrye and bluebunch wheatgrass share dominance in the understory.

Bitterbrush rapidly occupies sites following a disturbance. This ability to tolerate bare sites is one of the factors allowing it to be a pioneer species on the cinder substrates. Bitterbrush has re-established more rapidly than sagebrush following the fire that occurred in the 1940's on Coyote Butte. On heavier soils, mountain big sagebrush would probably re-establish with bitterbrush.

Bitterbrush is not shade tolerant and will often decline in a stand as the canopy of trees develops. This may be a factor for long-term bitterbrush productivity on sites where Douglas-fir or limber pine stands are developing. The stands of decadent bitterbrush on Grassy and Big Cinder Buttes are probably declining as a result of conifer overstory closure.

Bitterbrush is a relatively short-lived plant. McConnell and Smith (1977) found that biomass productivity declined in Oregon high desert populations after approximately 70 years. We have noted similar declines in populations on the southern Boise National Forest. This indicates that conditions for adequate seedling establishment must be frequently met to maintain vigorous populations. Without periodic disturbance, we predict that bitterbrush not associated with limber pine would decline in seed and biomass production but would remain in the community. Those bitterbrush stands associated with limber pine would be affected by the degree of tree canopy closure. Probably only those in the high density limber pine stands would be reduced.

Populations of bitterbrush associated with mountain big sagebrush are reasonably well adapted to periodic fire (Bunting et al. 1985). They are normally of the decumbent growth form which resprouts well. Resprouting of bitterbrush averaged 45% in nonforested communities where mountain big sagebrush was present. Moderate seedling establishment occurs on these sites and it is expected that bitterbrush populations would recover within 10 to 20 years following fire.

Great Basin Wildrye

This community is restricted to two areas north of the highway, one at the mouth of Little Cottonwood Canyon and a second just north of the group campground. Great Basin wildrye is the dominant plant species in both areas. Mountain big sagebrush and rubber rabbitbrush are found in limited quantities along the margins of this community but do not occupy the community. The shrubs are probably restricted by the high water content of the soil during the spring period. Stickseed, tumble mustard, and field pennycress are found on disturbed areas within this type. Small amounts of Canada thistle are found adjacent to Little Cottonwood Creek. These forb species tend to behave as weeds (tumble mustard, field pennycress and Canada thistle are also exotics) and would increase temporarily following fire.

The wildrye community is productive and appears to be maintaining itself. The major environmental factor determining its development as a community is the periodic moisture saturated soil. Wildrye is well adapted to fire and annual biomass production would probably increase following a fire for several years. There is no evidence, however, that the current community is dependent upon fire for maintenance. Fire would control the big sagebrush at the community boundary but sagebrush encroachment is limited by the saturated soil.

Canada thistle would increase in the community following fire. Its rhizomatous rootsystem and aggressive seedlings would make it possible for this species to rapidly occupy the plant interspaces created by the fire. Once established the thistle would likely remain in the newly occupied area. Therefore, fire would only serve to spread thistle.

Limber Pine-Bitterbrush

Day and Wright (1985) defined three separate limber pine/antelope bitterbrush communities based on the density and cover of the limber pine. In each type, limber pine dominates the landscape. The distribution of limber pine is probably heavily influenced by seed caching activity of Clark's nutcracker. Reproduction of whitebark pine is nearly completely dependent upon Clark's nutcracker (Lanner 1980). The reproduction of limber pine has a similar dependence on the birds.

Low cover limber pine/antelope bitterbrush stands are found on the older block lava flows. These are typical in the Devil's Orchard area and in the vicinity of the Sentinel. The understory is variable but is primarily composed of rubber rabbitbrush, antelope bitterbrush and lava phlox.

High cover limber pine/bitterbrush stands tend to occur in association with cinder and older pahoehoe lava flows on many areas of the monument south of the highway. Antelope bitterbrush and mountain big sagebrush are co-dominant shrubs in these stands, with rubber rabbitbrush a frequent associate. All 3 of these shrub species are shade intolerant but can persist in the stand at the densities which limber pine achieves. At high tree density such as on the north slope of Grassy Cone, these shrubs will begin to decline on the site. Grasses include Sandberg bluegrass, bottlebrush squirreltail and occasionally Indian ricegrass. These grass species are also shade intolerant and will decline under conditions of high tree density. Limber pine is also shade intolerant but densities which interfere with reproduction are seldom achieved on CRMO.

Selected locations in the central and southern portions of the monument support very high densities of limber pine (up to 456 trees/ha). Usually these sites are on the northeast slopes of older cinder cones. The shrub component is similar to the other limber pine types, but herbaceous production and cover are lower.

Substantial numbers of mature limber pine on the monument were removed or poisoned in the mid-1960s in order to "control" a dwarf mistletoe outbreak. Despite this loss, the number of limber pine trees appears to be increasing on many sites throughout the monument (Table 3). The increase apears to have been most rapid during recent years as the mean annual density change has been 3.8% since 1961. This increase has resulted in spite of over 6000 trees being killed during the dwarf mistletoe control program.

The increase in limber pine is consistent with observed changes in the distribution of other conifers throughout the region (Franklin et al. 1971, Koterba and Habeck 1971, Vale 1981, Arno and Gruell 1983, Butler 1986). This has been attributed to an number of factors including fire suppression, grazing by domestic livestock and climatic variation. At CRMO the influence of the former 2 factors has been minimal, suggesting that climatic variation is the predominant factor involved. This is confounded by the primary succession occurring on the monument. Successional changes may be occurring more rapidly than formerly expected. The cause of the increase is probably "natural" and not human induced, and therefore, no management action is required to rectify the situation.

The occurrence of fire would set succession back and reduce the abundance of both limber pine, sagebrush and bitterbrush. If rubber rabbitbrush was abundant at the time of the fire, it would probably then dominate the site. If rabbitbrush were not present, then grasses would probably dominate until the shrubs and limber pine became re-established. It would probably require 50-100 years for the shrubs to dominate and over 100 years for the limber pine to re-establish on the site. The establishment rate for limber pine is not well documented, however. Data indicate that it requires over 50 years for whitebark pine to become re-established following fire and then up to 100 additional years for the individual to reach maturity (Morgan and Bunting Unpublished data). Whitebark pine has many similar site requirements to limber pine and is also dependent upon the Clark's nutcracker for reproduction (Lanner 1980).

Table 3. Change in limber pine density at Craters of the Moon National Monument from 1922 to 1986 based on paired photographs (Wright and Bunting Unpublished data).

Years	Interval length (yr)	Percent change (Range)	Annual change (Range)	Mean annual change (%)
1961-1986	25	21 - 244	0.84 - 11.64	3.8
1955-1986	31	-10 - 85	-0.34 - 2.94	1.1
1922-1986	64	-8 - 160	-0.13 - 3.08	1.3

Douglas-fir

This type is found in three discrete areas, Grassy Cone, Sunset Cone, and in the upper portions of Little Cottonwood Canyon. The stand on Grassy Cone is on a more xeric site with cinder substrate. Mountain snowberry is the dominant understory shrub and antelope bitterbrush and rubber rabbitbrush are common in certain locations. Chokecherry is frequent in restricted areas. The herbaceous understory is sparse and includes arrowleaf balsamroot, bluebunch wheatgrass, Sandberg bluegrass, and desert parsley. The Sunset Cone stand is also a xeric site. The substrate is also cinder, but mixed with a more coarse aggregate. The shrub and understory components are sparse in this stand as well. Sandberg bluegrass, antelope bitterbrush and cinquefoil occur infrequently. Scattered aspen are also present.

A Douglas-fir stand, more typical of those found in central Idaho, is located in upper Little Cottonwood Canyon. This stand appears to be quite viable with numerous young trees. The understory dominant, mountain snowberry, is much more prevalent than in the preceeding stands. Other understory species such as nettleleaf, slender wheatgrass, and starry solomonplume indicate a more moist environment. In all of the Douglas-fir stands, understory cover is reduced due to wildlife use. These stands are a favored mule deer foraging and resting area, particularly in late summer and early fall.

Based on photographic evidence, the Douglas-fir stands have increased both in density and in area by spreading into adjacent sagebrush grasslands over the past 50 to 75 years. The increase in Douglas-fir is consistent with the results found by other researchers in the region (Patton 1969, Sindelar 1971, Arno and Gruell 1982, Gruell et al. 1986). The stand in Little Cottonwood Canyon has invaded into adjacent sagebrush-grass and aspen vegetation types. The development of a coniferous overstory alters the understory significantly as shade-tolerant species become more abundant. Eventually most species found in the sagebrush-grass and the aspen stands will be lost from the community. The effects of conversion to Douglas-fir have been described by Gruell et al. (1986).

The primary cause of the regional increase in Douglas-fir is thought to be fire suppression which allows the young seedlings to become established in the adjacent communities (Houston 1973, Arno 1980). This is also probably the case for Little Cottonwood Canyon and Grassy Cone. Fire scars can be found on the older Douglas-fir trees in Little Cottonwood Canyon. It appears from dates on these trees that the last major fire in this drainage occurred over 100 years ago. Lavas and cinders from recent volcanic activity at the mouth of the canyon would have prevented fires from sweeping out of the valleys and up the canyon. Thus, fire was probaby not as prevalent here as in many similar canyons out of the monument and they would tend to be less extensive with local ignitions.

Fire within this type would reduce the abundance of Douglas- fir and increase the abundance of shade intolerant shrub species such as sagebrush and bitterbrush. Low intensity fires would primarily effect the young trees and saplings leaving the mature trees as a seed source for regeneration. High intensity fires could potentially kill most Douglas fir within the stand. The recovery period would then be substantially longer and it may require several hundred years for the site to recover to the preburn conditions.

Upland Quaking Aspen

The majority of the aspen on the monument is located north of the highway. However, scattered stands occur in the central and southern portions of the monument on Big Cinder Butte, Fissure Butte, and small areas within the Silent Cone flow. In each, quaking aspen is the dominant species. Woods rose, chokecherry, antelope bitterbrush and mountain big sagebrush are common associates. Fireweed grass, bluebunch wheatgrass, slender wheatgrass and mountain bromegrass are the most abundant grass species in this type.

Like the limber pine and Douglas-fir, the aspen stands on the northern portion of the monument have increased in area substantially in the past 50 years (Wright and Bunting, unpublished data). In many areas the understory cover has been heavily depleted by mule deer which use the stands for shade and resting cover in summer and early fall.

In the absence of fire, aspen will tend to invade into adjacent sagebrush grassland vegetation (Loope and Gruell 1973). Older stands on northern aspects will be invaded themselves by Douglas-fir if a seed source is available. Fire in aspen stands will invigorate the stand by inducing resprouting and controlling competing vegetation. Non-resprouting species such as conifers will be temporarily removed from the stand. Lack of fire in the stands invaded by Douglas-fir will result in a conversion of this type to a Douglas-fir forest and eventual loss of the aspen. In stands which are not invaded by conifers, the situation is less clear. Some researchers consider the aspen to be climax on these sites (Langenheim 1962, Reed 1971). Many aspen stands will deteriorate in time if not invigorated by fire and will revert back to grassland or sagebrush grassland (Krebill 1972, Schier 1975, DeByle 1976, DeByle and Winokur 1985). It is not clear which will happen at CRMO but there is no evidence at this time of aspen stand deterioration.

Riparian Zone

Two small zones of riparian vegetation are found in the northern portions of the monument along the drainages of Little Cottonwood Creek and Leach Creek. Both areas are comprised of dense woody vegetation and an understory of dense tall forbs. The dominant tree species include quaking aspen, cottonwood, chokecherry, alder, and willow. The forb layer is comprised primarily of cow parsnip, big-sting nettle (both exotics), and small-leaf angelica.

Little information is available on the effects of fire or lack of fire on riparian systems. Most of the overstory shrub species resprout vigorously following fire and most understory species can probably survive infrequent fires of low intensity. Fire would tend to remove Douglas-fir from riparian zones but Douglas-fir probably would not become a dominant in any case because it is best adapted to upland, well drained sites. Riparian sites can accumulate substantial amounts of dead wood in the shrub canopies and on the soil surface. This is particularly true for those dominated by willows. Periodic fire probably would maintain the shrubs in a more healthy and productive condition if fires did not occur too frequently. There is no evidence to indicate that fire is necessary to maintain the vegetation type in this area.

If fires occurred too frequently in riparian systems, the stream course would begin to straighten and water flow would accelerate. Debris dams and overhanging banks would be reduced. Water quality would probably decline due to increased sediment loads. Riparian zones are disproportionately important to wildlife species as compared to the area of upland vegetation (Ames 1977, Thomas 1979, Wright and Hoffman Unpublished data from CRMO). Frequent fires within these types would greatly change the structure of the plant community, reducing the tree and shrub component and thereby reduce the habitat value for wildlife.

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