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Wildlife, Animals, and Plants |
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FIRE EFFECTS
IMMEDIATE FIRE EFFECT ON PLANT:Rubber rabbitbrush is often top-killed by fire [74,91]. Because of relatively high resin content, both foliage and stems may be consumed, even at fairly high moisture content. Mortality after fire is variable but is often very low [99,103]. Fire effects may depend on subspecies, season of burn, and condition and vigor of plant. After fires with high fireline intensities or a long residence time, buds located at or near the root crown may be killed, limiting ability to resprout [146]. Young [147] reported mortality of 20% after fire in Intermountain shrubsteppe. In the Malheur National Wildlife Refuge of Oregon, postburn mortality of <5% was observed [149].
DISCUSSION AND QUALIFICATION OF FIRE EFFECT:Potential damage is influenced by proximity to other shrubs that provide additional fuel and increase fireline intensity. Mortality is also greater where plants have been defoliated by browsing prior to burning. Plants may lack sufficient carbohydrate reserves to resprout [99].
PLANT RESPONSE TO FIRE:Recovery of rubber rabbitbrush after fire is described as "rapid" or "very rapid" [91,123,128,148]. Recovery may occur by means of vigorous sprouting or through an abundance of wind-dispersed seed [148]. Resprouting may be aided by the release of nutrients after fire [121]. Most postfire sprouting is epicormic (stem) and not root or root crown sprouting [99]. Sprouting response depends on burning conditions, weather, season of burn, subspecies, and ecotypic variation [74,99,116]. White-gray subspecies such as Chrysothamnus nauseosus ssp. hololeucus and C. n. ssp. albicaulis are relatively susceptible to fire, whereas the green-gray subspecies (i.e., C. n. ssp. consimilis and C. n. ssp. graveolens) more often survive [144]. Postfire drought conditions may cause mortality in plants that would otherwise resprout [105]. In many areas, reproduction from seed is also important in increasing rubber rabbitbrush population densities [65,99]. Surviving plants can, in some cases, sprout culms that quickly flower almost immediately after fire. In other instances, plants sprout the following growing season and produce an abundance of flowers and seeds [147]. These seeds germinate and establish the second year after burning. Postfire seed crops are often particularly heavy [149].
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:Rubber rabbitbrush is sensitive to competition. Sites with a dense stand of perennial grasses and forbs are less likely to be dominated by rabbitbrush after fire than those where the understory has been depleted. Burning can temporarily eliminate sagebrush and other plants that compete for water and space. Release from competition stimulates rubber rabbitbrush to produce large numbers of seed [82]. Rubber rabbitbrush biomass production remains low for 1 to 3 years after fire and then often increases rapidly [145]. Rubber rabbitbrush can be a major component of vegetation within 3 to 5 years after a burn [12]. Wright [145] reported that burning reduced rubber rabbitbrush by 59% the first year after fire near Dubois, Idaho. Three years after burning, production doubled; it tripled by the end of year 12. Rubber rabbitbrush reestablished from seed after fire in a Great Basin dry meadow. It peaked in abundance 12 years later [50]. Rubber rabbitbrush may dominate postburn shrub-grass communities in degraded condition if perennial grasses are poorly represented [149]. In many Intermountain shrub-steppe communities, seedlings of rubber rabbitbrush will occupy the sites for 10 to 15 years before big sagebrush again assumes dominance [147]. In pinyon-juniper communities of California, rubber rabbitbrush colonizes higher elevation burns (> 6,600 feet (2,000 m)). Along with other shrubs, it increases in cover and density for 30 to 50 years [135]. It serves as a "nurse shrub" and is rarely found on burns older than 47 years. Two general postburn patterns were noted in these communities: 1) understory fires followed by rapid postfire perennial grass succession, and 2) canopy fires followed by slow postfire shrub and tree succession [135]. General cover by year was as follows [135]:
Immediate reductions in rubber rabbitbrush after a July burn near Kamloops, British Columbia were reported as follows [61]:
FIRE MANAGEMENT CONSIDERATIONS:Control of rubber rabbitbrush with fire is described as "erratic" [17]. Results may differ even on the same site and date if burned in different years. The outcome depends largely on whether the fire is hot enough to kill the crowns [17]. In general, fire must be at least "moderately hot" for effective control [74]. Rubber rabbitbrush may be more susceptible if burned after heavy grazing or during the early summer [148] On many greasewood-rabbitbrush sites, vegetation is typically very sparse and burns can take place only under very hazardous fire conditions [17]. Many degraded sagebrush sites are also difficult to burn. A rest from grazing in summer can increase fuel continuity for better spread if burned in spring, summer, or fall [74].
Related categories for SPECIES: Chrysothamnus nauseosus | Rubber Rabbitbrush |
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