• FIRE ECOLOGY OR ADAPTATIONS
• POSTFIRE REGENERATION STRATEGY

FIRE ECOLOGY OR ADAPTATIONS:

Fire adaptations: Fire is the principal means of renewal for decadent stands of Wyoming big sagebrush [17]. Wyoming big sagebrush establishes after fire from the seedbank [12,90,112]; from seed produced by remnant plants that escaped fire [29]; and from plants adjacent to the burn that seed in [29,31]. Fires in Wyoming big sagebrush are usually not continuous, and remnant plants are the principal means of postfire reproduction [29]. Fire does not stimulate germination of soil-stored Wyoming big sagebrush seed, but neither does it inhibit its germination [30].

Wyoming big sagebrush × plains silver sagebrush (Artemisia cana ssp. cana) hybrids usually sprout after top-kill by fire [89].

Litter production is lower in Wyoming big sagebrush communities than in other big sagebrush subspecies, but still may be greater than litter production in communities dominated by other cold-desert shrubs. In the Curlew Valley of northern Utah, average annual litter production was greater in Wyoming big sagebrush (192 g/m²/year) than in winterfat (Krascheninnikovia lanta) or shadscale (Atriplex confertifolia) communities [145].

Fire regimes in Wyoming big sagebrush communities: Wyoming big sagebrush steppe communities historically had low fuel loadings and were characterized by 10- to 70-year interval, patchy fires that produced a mosaic of burned and unburned lands [24,54,60,82,107,137,152,153,154,157]. Fire scars on western juniper in a Wyoming big sagebrush/bluebunch wheatgrass community in Lassen County, California, showed fire return intervals ranging from 10 to 40 years [154]. Vincent [135] suggests that in northern New Mexico, infrequent fire probably maintained Wyoming big sagebrush communities as open, seral stands of Wyoming big sagebrush with productive herbaceous understories. Historic mean fire return interval in northern New Mexico Wyoming big sagebrush communities is estimated at 40 to 50 years [135,153].

Fire regimes have been radically altered in Wyoming big sagebrush communities heavily invaded by cheatgrass [27,66,76,89,116,129]. Cheatgrass dominates many Wyoming big sagebrush stands in southern Idaho, northern Nevada, and eastern Oregon. Annual cheatgrass production is highly variable and can be considerable in years of favorable precipitation. An abundance of cheatgrass enhances the likelihood of fire spread [27]. Fire hazard is estimated to be 5 times as great in big sagebrush communities converted to cheatgrass [106]. Besides removing Wyoming big sagebrush, frequent fire may also inhibit its re-establishment. Repeated burning and invasion by cheatgrass removes VAM associated with Wyoming big sagebrush [109]. Some Wyoming big sagebrush sites in southern Idaho have burned 2 or 3 times within 10 years [18]. On such sites, Wyoming big sagebrush is not regenerating before the next fire cycle, and former steppes are converting to annual grasslands [97].

Fire regimes in other types: Fire return intervals in communities in which Wyoming big sagebrush is an important component of the understory are similar to those of Wyoming big sagebrush communities and are summarized below. For further information on fire regimes in these forest and woodland communities, see the FEIS species report.

Species                  Interval 
Pacific ponderosa pine   1-30 yrs 
   (Pinus ponderosa var. ponderosa)

interior ponderosa pine  2-45 yrs
   (P. p. var. scopulorum)

western juniper          7-100 yrs
   (Juniperus occidentalis)

Utah juniper             10-30 yrs
   (J. osteosperma)

POSTFIRE REGENERATION STRATEGY:

Secondary colonizer - on-site seed
Secondary colonizer - off-site seed

Related categories for SPECIES: Artemisia tridentata ssp. wyomingensis | Wyoming Big Sagebrush