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Wildlife, Animals, and Plants |
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FIRE EFFECTS
IMMEDIATE FIRE EFFECT ON PLANT:Blackbrush stands are substantially decreased or eliminated by fire [8]; fire usually kills blackbrush seeds and mature shrubs [17,22]. Blackbrush is susceptible to fire and slow to reestablish [129]; it is generally removed from the site for 25 to 30 years [8,129].
DISCUSSION AND QUALIFICATION OF FIRE EFFECT:No entry
PLANT RESPONSE TO FIRE:Blackbrush is a nonsprouter after fire and does not aggressively return to burned sites [8,17,20,36,124,125,129,129]. A number of common desert shrubs and annuals occupy blackbrush sites after a fire, but very few blackbrush seedlings are usually present [17]. Fire destroys the short-lived blackbrush seedbank [72], and blackbrush may take 60 years or more to reestablish after fire [17,72]. Blackbrush reinvades so slowly following fire that even after 35 years it may not be an important component of the vegetation [37].
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:Thatcher [104] observed the return of blackbrush following natural fires in a relict area of northwestern Arizona. The relict area developed under the influence of natural fire, without the influence of humans and domestic livestock. Natural fires in areas where blackbrush dominated did not materially alter the plant community: the community reverted immediately back to blackbrush without going through an intermediate plant association.
FIRE MANAGEMENT CONSIDERATIONS:Fire can create more diverse plant communities from nearly monotypic blackbrush stands [8,17]. Prescribed burning has been used to promote forage-producing species in blackbrush communities [8] and to increase the herbaceous component in blackbrush communities [17]. Conversion results vary; common successors include turpentine bush, desert bitterbrush, Mojave desertrue, banana yucca, Stansbury cliffrose (Purshia mexicana var. stansburiana), ephedra, desert almond, big sagebrush, broom snakeweed, red brome, and cheatgrass [8,24]. Fires may increase species diversity, livestock carrying capacity, and range condition. The following table describes 5 different sites and improvement of range condition after fire. All sites had cobbled, stony soils with 35% or more gravel content and received a mean annual precipitation of 125 mm [8].
Prescribed burning on 3 southern Nevada sites killed the blackbrush cover, and the species failed to reestablish after as long as 28 years. Plant succession varied widely, with different plant species dominating on different burns, but the density of annual species was substantially increased in the 1st 3 years following burning. Replacement shrubs after fire were largely undesirable forages [17]. Since sites may be highly suitable for blackbrush, burning these areas to convert them to grassland may give unpredictable or undesirable results [23]. After burning on 3 proximal sites in southwestern Utah, 1 site was dominated by turpentine bush, desert bitterbrush, desert almond, and big sagebrush; another site established a pure stand of broom snakeweed, and a 3rd site established a pure stand of big sagebrush [16]. Vast areas of blackbrush in Nevada were burned in the 1940s and 1950s. These sites were subsequently occupied by annuals and broom snakeweed and have been subject to recurring fires. In wet years, the burned areas had 8 to 10 times more herbage production than the range before it was burned, but herbs were very sparse in dry years [124]. Site potential is an important consideration for burning blackbrush; fire may be more useful on areas with better-developed soils and potential to revegetate to more desirable plants [8]. Widespread burning to reduce blackbrush is not recommended due to the unpredictability of successive vegetation, accelerated soil erosion, long-term or permanent removal of blackbrush, and damage to cryptogamic soil crusts [24,125,129]. Fire may be a necessary tool to modify fuel buildup; however, research is needed regarding management and restoration recommendations for blackbrush [72].
Related categories for SPECIES: Coleogyne ramosissima | Blackbrush |
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