Subalpine Coniferous Cool Moist subalpine fir (Abies lasiocarpa)-Engelmann spruce (Picea engelmannii)

Description

State 1.0
Western white pine (Pinus monticola)/(subalpine fir (Abies lasiocarpa)-Engelmann spruce (Picea engelmannii)/Sitka alder (Alnus viridis ssp. sinuata)/rusty menziesia (Menziesia ferruginea)-thinleaf huckleberry (Vaccinium membranaceum)/common beargrass (Xerophyllum tenax).

Submodel

Description

State 2: Subalpine fir (Douglas fir) /Greene’s mountain ash/rusty menziesia-thinleaf huckleberry/beargrass.
State 2 is different than State 1 in that western white pine no longer plays a significant role in the seral communities as it once did. Western white pine has been dramatically reduced in numbers and area by the epidemics of white pine blister rust, western spruce budworm, and dramatic fire suppression. Therefore, climax species have been able to fill the seral role that western white pine held. As well, more forests are progressing to the climax or Reference phase than historically when most forests were in the fire-maintained western white pine-dominated seral phase. Forests are now dominated by these shade-tolerant climax species subalpine fir and Engelmann spruce. While there is a tremendous effort to bolster the numbers of western white pine, it currently covers only 5 percent of its historic range.

Submodel

Description

Another disease affecting the 43A SUBALPINE COOL MOIST CONFEROUS ecological site is root rot. Armillaria root disease is the most common root disease fungus in this region, especially prevalent west of the Continental Divide. It may be difficult to detect until it has killed enough trees to create large root disease pockets or centers, ranging in size from a fraction of an acre to hundreds of acres. The root disease spreads from an affected tree to its surrounding neighbors through root contact. The root disease affects the most susceptible tree species first, leaving less susceptible tree species that mask its presence. When root rot is severe, the pocket has abundant regeneration or dense brush growth in the center. In western Montana and northern Idaho, Armillaria is present in most stands with diffuse mortality and large and small root disease centers. The disease pattern is one of multiple clones merging to form essentially continuous coverage of sites. Grouped as well as dispersed mortality can occur throughout the stand. A mosaic of brushy openings, patches of dying trees, and apparently unaffected trees may cover large areas. There can be highly significant losses, usually requiring species conversion in the active management approach. Management tactics include to identify the type of Armillaria root disease present and manage for pines and larch. Pre-commercial thinning may improve growth and survival of pines and larch. Avoid harvests that leave susceptible species (usually Douglas-fir or true firs) as crop trees (Hagle, 2010). A link has been determined between parent material and susceptibility to root disease, and metasedimentary parent material is thought to increase the risk of root disease. Glacier NP is dominated by metasedimentary parent material, and therefore may be more at risk than other areas to root disease (Kimsey et al., 2012). If a stand sustains very high levels of root disease mortality, then a coniferous stand could cross a threshold and become a shrubland, once all conifers are gone (Kimsey et al., 2012).

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