• FIRE ECOLOGY OR ADAPTATIONS
• POSTFIRE REGENERATION STRATEGY

FIRE ECOLOGY OR ADAPTATIONS:

Scouler willow layer groups are distinct shrub layers that occur in various habitat types and are created by stand replacing fires [218,227,228,229,231]. Severe wildfires expose patches of bare mineral soil, encouraging the development of Scouler willow shrub layers [229,231]. These layer groups may also develop in response to mechanical scarification in clearcuts and broadcast burns, especially where exposed soil was mounded to trap water behind the mounds, creating well-watered seedbeds of mineral soil [229,231,233].

Scouler willow is frequently a dominant or codominant in the persistent seral brushfields of northern Idaho. These brushfields are likely the result of dry weather patterns after canopy removal and repeated severe fires, which remove most large woody material, litter, and herbaceous fuels. Standing shrubs comprise most of the biomass, and these brushfields can burn in almost any season. If surface fuels are continuous and dry, spring fires spread readily. In the summer, brushfields are often hot and dry, and conditions are exacerbated where nighttime inversions occur. Hot, dry winds during drought conditions can drive severe fires through the shrub layer, with Scouler willow readily regenerating from seed and resprouting [222].

In interior Alaska, Foote [69] identified six community developmental stages following fire in black spruce forests. These are: 1) newly burned, 2) moss-herb, 3) tall shrub-sapling, 4) dense tree, 5) hardwood or mixed hardwood-spruce, and 6) black spruce. Arising from resprouts, Scouler willow can average up to a few thousand stems per hectare 1 year following wildfire depending on preburn density, and thus is an important part of the newly burned stage. It is then often dominant or co-dominant through the tall shrub-sapling stage of succession for about 30 years. It thereafter becomes less frequent, as larger trees outgrow and overtop it.

Resprouting occurs in response to overstory thinning [217] where Scouler willow is well-distributed and in need of rejuvenation [87]. Generally, fast spreading fires produce more willow sprouts than slow fires that can damage root crowns [222]. Density and canopy coverage frequently increase after fire because root crowns produce multiple sprouts [179]. Four years postfire in Alaska, Scouler willow presence was 4 times greater on burned sites than on adjacent unburned sites [253]. In northern Idaho, Scouler willow cover was much higher on burned clearcuts than on unburned clearcuts, particularly where there had been repeated fires over a 30 year period [172]. Postfire immature stands (<90 years) in Montana have significantly more (p<0.05) presence and percent cover of Scouler willow than old growth stands (>150 years) [5].  The increased presence of Scouler willow in Douglas-fir/ponderosa pine stands following elimination of frequent fires is likely the result of stand opening associated with logging [19]. Resprouting Scouler willow creates a round growth form up to 16 feet in diameter and may as a result promote reestablishment of shade tolerant species like Douglas-fir, in turn posing a greater risk of stand replacing fires and favoring growth of Scouler willow [234].

Without fire, closing conifer canopies lead to the deterioration of Scouler willow [84]. In dense second growth stands of sequoia in California, Scouler willow debris creates a fuel hazard; formerly abundant stands of Scouler willow grew in dense clones that were shaded out and killed, forming dense tangles of fuel for wildfire [28].

Fire regimes for plant communities and ecosystems in which Scouler willow occurs are summarized below. For further information regarding fire regimes and fire ecology of communities where Scouler willow is found, see the "Fire Ecology and Adaptations" section of the FEIS species summary for the plant community or ecosystem dominants listed below.

POSTFIRE REGENERATION STRATEGY [241]:

Related categories for SPECIES: Salix scouleriana | Scouler Willow