Ashy Depressions 35"+ PZ Frigid

Description

This state with extended fire intervals turns into an all aged western redcedar stand with some grand fir and/or western hemlock present. Stand development after fire depends on fire size and severity, as well as changes in drainage and microclimate. Since severe fires are accompanied by stand removal over a large geographic area, stand-replacing fire may be followed by a significant rise in the water table. Salix scouleriana often dominates such wet sites. Canopy removal also increases the likelihood of frosty conditions, favors shrub dominance, and retards establishment of the ferns and herbs characteristic of climax stands. Reforestation may require more than 100 years. The tree species that establish on burns vary with postburn conditions. Shade-tolerant species are favored in small openings, especially if duff is not removed. In larger openings, hardwoods and shade-intolerant conifers can overtop climax species and so dominate early seral stages. Black cottonwood is often important in such stands. On sites with good drainage, western white pine, western larch, and Douglas-fir all occur. Cold conditions favor Engelmann spruce and occasional lodgepole pine. Rotting logs are the best microsites for tree establishment; root crowns of fallen trees are also good seedbeds. With successful tree regeneration a mix of seral tree species can occupy the stand or in some cases, a single species like western larch will dominate the stand. These stands go into the stem exclusion phase with tree to tree competition. Understory vegetation will be sparse. As these stands mature mixed severity fires create a mosaic of stand structure and species composition with a combination of seral species and shade tolerant cedar, hemlock and grand fir. Old-growth stands develop an open canopy composed of large, evenly spaced trees, with mostly cedar or hemlock regeneration beneath. The most vigorous understory trees originate in canopy gaps, not in shade (Smith and Fisher, 1997).

Submodel

Description

Severe fires change reference state to a shrubfield site. No tree regeneration due to shrub competition and soil conditions. Major shrubs include snowbrush and redstem ceanothus, serviceberry, ninebark, Scouler willow, elderberry species, snowberry, spirea, and Douglas maple

Submodel