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Wildlife, Animals, and Plants |
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FIRE ECOLOGYFIRE ECOLOGY OR ADAPTATIONS:Adaptations to fire: Grand fir is moderately resistant to frequent surface fire. It has thin bark and is easily killed when young, but the bark is thick enough at maturity (about 2 inches (5 cm)) to provide resistance to low- and moderate-severity fires [3,169,44,50,69,89,92]. Compared to other Pacific Coast conifers, it is less fire resistant than coastal Douglas-fir but more so than western hemlock and Pacific silver fir [70]. Inland, it is less fire resistant than western larch, Pacific ponderosa pine, and Rocky Mountain Douglas-fir; about the same as white fir; and more fire resistant than western white pine, subalpine fir, Engelmann spruce (Picea engelmannii), and Rocky Mountain lodgepole pine [148,70]. Fire-scarred grand fir are susceptible to heart rot [7,9,14,108,62]. Grand fir does not survive crowning or severe fire. Its low, dense branching habit, flammable foliage, and tendency to develop dense stands with heavy lichen growth increase the likelihood of torching and mortality from crown fire [44,50,69,169]. Fire strongly influences grand fir's ecological niche and successional role [91,108]. In coastal British Columbia grand fir occurs in areas of relatively low summer rainfall and high summer temperatures, suggesting that its range may be restricted to sites with higher fire frequencies compared to moister surrounding forests with longer fire return intervals [155]. On many Pacific Northwest sites, however, grand fir only dominates sites where fire is excluded. Fire history studies show that Oregon white oak, Port-Orford-cedar (Chamaecyparis lawsoniana), Pacific ponderosa pine, western larch, and/or coastal Douglas-fir were maintained as site dominants by frequent surface fires that eliminated young grand fir [90,91,81]. After cessation of Native American burning in the Willamette Valley of Oregon (around 1850), grand fir has successionally replaced Oregon white oak and coastal Douglas-fir on most sites. Coastal Douglas-fir retains dominance only on the driest sites in the valley [42]. Although grand fir is not usually seral on sites with frequent fires, it may be either climax or seral on sites that experience infrequent crown fires [91].Fire regimes: Fires in grand fir types were historically of mixed severity, with fire behaviors ranging from frequent low-severity, nonlethal surface fire to infrequent, stand-replacing crown fire [9,3,5,18,139,12,166,19]. The grand fir series can roughly be divided into warm/dry types and warm/moist types. In warm/dry types, the historical fire regime was frequent (5-50 year), low-severity fire that favored Pacific ponderosa pine and western larch [11,34,170,190]. For example, a mean fire return interval of 47 years is reported for the Blue Mountains [190], with a range of 33 to 100 years [194]. Historically, fire severity in grand fir types of the Blue Mountains was often moderate, with a wider range of fire severities than Douglas-fir types [3]. Dry grand fir/graminoid types with understories of elk sedge or pinegrass typically experienced frequent surface fires (10- to 25-year intervals) [6,128,191]. Fire regimes in northern Idaho and western Montana were historically similar to those in the Blue Mountains, but fire return intervals showed a wider range (3-200 years) [9,11]. On a dry site in the Bitterroot National Forest of western Montana, Arno [162,171] reported a mean fire return interval of 17 years between 1735 and 1900, with a range of 3 to 32 years. He attributed the short fire return interval to the relative scarcity of the grand fir series there, so that grand fir had "fire frequencies much like those in surrounding major series" such as Rocky Mountain Douglas-fir [16,12]. Mixed-severity fires with longer return intervals (25-100 years) were more common on cooler, moderately moist grand fir types with Rocky Mountain maple, Pacific yew, oak fern (Gymnocarpium dryoptera), or sword fern (Polystichum munitum) understories. Fire regimes shifted to moderate severity on these wetter sites, and stand-replacement fires were more common [3,6,34,12,166,19]. Fire-scarred, mature grand fir trees in northern Idaho have withstood moderate-severity surface fires once or twice a century [18]. Camp [34] reported that fire history was complex on warm/moist forests of the eastern slope of the Cascade Range in Washington, with evidence of both frequent, low-severity fires and infrequent severe, stand-replacing fires. Sites experiencing severe fire often escaped fire through 2 to 3 surface fire cycles that occurred in surrounding forest. These long-unburned sites developed into multi-layered grand fir forest that functioned as old-growth fire refugia until the next severe fire cycle. Presettlement sites of fire refugia occurred most often on north-facing aspects, benches, valley bottoms, and stream confluences and headwalls [34,35]. Long-interval (> 100 years), severe fires were most common on wet grand fir habitat types [12,166,19]. Moist types are highly productive and have large fuel loads [94]. Barrett [18] found that fires in grand fir of the Clearwater National Forest in northern Idaho were usually large and exhibited behavior of (1) moderate to severe surface fires that killed the grand fir but left a few fire-resistant seral conifers, and (2) running crown fires (with individual runs of several hundred acres) that killed entire stands. Even given this extreme fire behavior, there was also evidence of low-severity surface fires, particularly on north slopes, that scarred but did not kill grand fir [18]. Barrett and Arno [19] found that patchy, stand-replacement fires with a mean return interval of 119 years typified fire regimes in Rocky Mountain Douglas-fir/grand fir habitats of the Selway-Bitterroot Wilderness in northern Idaho. A minority of stands experienced mixed-severity fire of nonuniform spread. Long-interval, stand-replacing fire also occurred historically in the relatively moist Swan Valley of western Montana. The Swan Valley also shows evidence of a mixed fire regime, with a mosaic of stands of varying age and composition [9]. Fire return intervals in the Swan Valley ranged from 20 to 300+ years, with a mean of 150 years [9,10]. Fire regimes for plant communities and ecosystems where grand fir is a common associate are summarized below.
POSTFIRE REGENERATION STRATEGY [177]:
Tree without adventitious bud/root crown
Related categories for SPECIES: Abies grandis | Grand Fir |
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