Lower Subalpine Cool Moist Coniferous subalpine fir-Engelmann spruce/Rocky Mountain maple-thinleaf huckleberry/thimbleberry

Description

Historically western white pine would have been within Flathead County, which encompasses the Flathead NF and in lower elevations, west of the continental divide in Glacier NP. Originally, western white pine covered 5 million acres in the Inland Northwest. Western white pine is incredibly productive for timber, with a very high growth rate, is tall and deep–rooted, and competes best on highly variable, high resource sites. As well, it is tolerant to the native root rot diseases and other native forest pests, is susceptible to Armillaria root disease only when young, and is vulnerable to mountain pine beetle largely at advanced ages (over 140 years). It also has the capability to thrive in a wide variety of sites and environments, which means it has high ecological flexibility. It is a long-living seral species that tolerated intense timber harvesting practices and severe fire disturbance by its ability to regenerate heavily on mineral soil and in full sunlight. Fire greatly influences the composition, structure, and function of vegetation across the landscape. Historically, it was mixed severity fire in between severe stand-replacing fires. Western larch and western white pine are long-lived, fire-adapted, shade-intolerant tree species that thrived historically. Also present in significant amounts particularly in young stands, but which declined through time due to effects of insects and pathogens, were the shorter-lived, shade-intolerant, fire-adapted tree species such as Douglas-fir and lodgepole pine. Shade-tolerant, fire-intolerant tree species such as western cedar, western hemlock, grand fir, Engelmann spruce, and subalpine fir were present but rarely survived long enough to dominate stands, except where the interval between fires was unusually long and where root disease was not severe. Prior to the 20th century, western white pine was a major component in forested ecosystems of the inland northwest U.S., but has been greatly reduced in distribution and abundance by white pine blister rust, mountain pine beetles, and anthropogenic fire exclusion (Tomback and Achuff, 2010). Western white pine has been replaced by Douglas-fir, grand fir and western hemlock. Douglas-fir and grand fir are susceptible to a greater variety of insect and disease problems and hemlock is more sensitive to drought and decay. More stands have also progressed to the climax species-dominated phase, which previously were rarely achieved due to the fire rotations and susceptibility of these species to disease and forest pests. In a study of the effects of pathogens and insects on forests within the Inland Empire found that, excluding fire, more than 90 percent of sample stands changed to a different cover type, structure stage, or both during a 40-year period that was coincident with the blister rust epidemic and fire suppression policy. Root pathogens, white pine blister rust, and bark beetles were the cause of most changes and this accelerated succession of western white pine, ponderosa pine, and lodgepole pine to later successional, more shade-tolerant species. The structure was reduced in stand density or prevented canopy closure. Grand fir, Douglas-fir, and subalpine fir were the predominant cover types at the end of the period, and were highly susceptible to root diseases, bark beetles, fire, and drought. It is estimated that there will be greater accumulations occurring in low-density mature and younger pole-sized stands that result from root disease and bark beetle-caused mortality (Byler and Hagle, 2000). These stands also are less productive in terms of timber. They are dominated by species with high nutrient demands where nutrient storage and cycling rates are increasingly depressed. This will likely lead to ever-increasing stress and destabilization by pests and diseases. Drought can further exacerbate the situation by stressing trees. The Inland Empire Tree Improvement Cooperative and the USFS have a breeding program for blister-resistant western white pine. A total of approximately 5 percent of the original acre range has been planted with rust-resistant stock. Currently, the modified stock shows about 60 percent resistance to blister rust. A study modeling the effects of climate change found that warming temperatures would favor increased abundance of western white pine over existing climax and shade-tolerant species in Glacier NP, mainly because warmer conditions potentiate fire dynamics, including increased wildfire frequency and extent, which facilitates regeneration (Loehman et al., 2011).

Submodel

Description

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. The historic extent of western white pine in Glacier National Park was primarily along the western border. 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 the 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.

Subalpine fir (Abies lasiocarpa) and Engelmann spruce (Picea engelmannii) are the dominant overstory species with co-occurring Douglas-fir (Pseudotsuga menziesii) and lodgepole pine (Pinus contorta). The main understory species are the medium sized shrub Rocky Mountain Maple, the mid height shrub Thinleaf huckleberry (Vaccinium membranaceum) with an understory of wild sarsaparilla, threelaf foamflower and queencup bead lily (Clintonia uniflora). Subalpine fir, Engelmann spruce, western larch, Douglas fir, western white pine, lodgepole pine are present in decreasing abundance. Queencup beadlily is the indicator species for all phases of this habitat type but other indicator species specifically for this moister phase include: American trailplant (Adenocaulon bicolor), bunchberry dogwood (Cornus canadensis), fragrant bedstraw (Galium triflorum), threeleaf foamflower (Tiarella trifoliata), twinflower (Linnaea borealis), Utah honeysuckle (Lonicera utahensis), Oregon boxleaf (Paxistima myrsinites), thimbleberry (Rubus parviflorus) and thinleaf huckleberry (Vaccinium membranaceum). These phases represent the wetter aspect of this habitat type. The rusty menziesia (Menziesia ferruginea) indicated type specifically represents areas that are cold and moist. It is more common on cool north and east exposures and has rusty menziesia and broadleaf arnica (Arnica latifolia) abundant. The other phase of this type (wild sarsaparilla) represents the wet and moist portion of the habitat type on bottomlands and at the lowest elevations of the ecological site. Wild sarsapirilla, Pacific oakfern (Gymnocarpium disjunctum) and common ladyfern (Athyrium filix-femina) are indicators of this phase and paper birch (Betula papyrifera) can occur as a seral tree species. Redosier dogwood (Cornus sericea ssp. sericea), Pacific yew (Taxus brevifolia), American trailplant, bunchberry dogwood, stiff clubmoss (Lycopodium annotinum) and groundcedar (Lycopodium complanatum) also occur frequently.

This ecological site is described as having Cool and Moist site conditions, high species diversity in the overstory including western larch, Douglas fir, Western white pine, Engelmann spruce, lodgepole pine, subalpine fir and Grand fir. Sites after stand replacement fires can be dominated by lodgepole pine. Sites are too cool for western redcedar and western hemlock and not cold enough for whitebark pine in any major way. The historic fire regime of these forests is one of low frequency (about 128 years) and high intensity, and therefore an increased chance of stand-replacing fire when it does occur due to moist site conditions, relatively high loadings of live and dead fuels and periodic summer drought. Stand replacement fires occurs in patches of anywhere from 200 to 2000 hectares (McDonald et al., 2000). The general post disturbance successional phases include the stand initiation phase dominated by herbaceous and shrub species and conifer seedlings, the competitive exclusion phase of dense pole sized mixed conifer or single seral species, the maturing forest of overstory mixed conifer trees with or without patches of regeneration, and the Reference Phase dominated by subalpine fir and Engelmann spruce with small gap dynamics. Underburns which affect the understory shrub and herbaceous species and conifer regeneration the most, can occur and maintain any community phase. A stand-replacing fire in the mature forest or Reference Phase would result in the stand initiation phase with species composition of seedlings varying with site conditions. Moderate fires (or mixed severity fires) in the competitive exclusion phase would favor the more fire-resistant Douglas fir, western larch or Western white pine over lodgepole pine, Engelmann spruce, or subalpine fir. Therefore, these species would dominate the maturing forest phase for longer. After a stand replacement fire at this stage with serotinous lodgepole pine present then lodgepole pine seedlings would dominate the seedling and competitive exclusion phases. Absence of fire will transition the competitive exclusion phase to a mature forest dominated in the overstory by a mix of conifer species. Moderate or severe fire at this stage could remove much of Douglas fir, leaving the site to be regenerated by either serotinous lodgepole pine or remnant western larch. Severe fires that remove even western larch will return to the treeless stand initiation phase. If fire does not occur in the forest maturing phase, then this will continue into the Reference Phase. Significant fires that have occurred on the west side of the Continental Divide that have affected the Cryic/Udic Coniferous ecological site are the Starvation Creek fire in 1994, which burned 4,001 acres in Glacier NP and 7,202 total acres; the Wedge Canyon fire in 2003, which burned 30,314 acres in Glacier NP and 53,359 total acres; and the 1988 Red Bench fire, which burned 27,500 acres in Glacier NP and 36,037 total acres. All of those fires were caused by lightning. Also caused by lightning were the 2001 Moose fire, which burned 27,194 acres in Glacier NP and 70,605 total acres; the Harrison fire in 2003 burned 5,864 acres in Glacier NP; and the Rampage fire in 2003, which burned 21,630 in Glacier NP. The Robert fire in 2003 was caused by humans, and burned 39,384 acres in Glacier NP and 52,747 acres in total.

Both subalpine fir and Engelmann spruce are subjected to a variety of diseases and insect pests including root rot, stem decay, bark beetles and wood borers and defoliators. These can weaken and or kill trees, which results in small openings scattered throughout the forest or major mortality during an outbreak such as western spruce budworm (Choristoneura occidentalis). The patterns of damage from endemic populations of insects and disease creates small openings whereas epidemic patterns are extensive throughout the landscape. Windthrow can commonly cause additional damage to stands following disease and pest disturbance. Subalpine fir is most commonly susceptible to Armilllaria and Annosus root disease, Pouch, Indian paint and red belt fungus which cause stem decay, metallic, roundheaded and Western balsam bark beetle, fir canker and defoliators such as Delphinella shoot blight, black mildew, brown felt blight, fir needle cast, snow blight and Fir-blueberry rust. Engelmann spruce is most commonly susceptible to Annosus and Schweintzii root disease and butt rot, Pini rot, stem decays by red belt fungus, metallic and roundheaded borers, spruce beetle, blue stain of sapwood, spruce broom rust and spruce canker and brown felt blight.

A good tool to use to discern the level of insect and disease and the damage patterns and whether these are at endemic or epidemic levels is aerial photography. These maps capture only moments in time though and infestations grow and move from location to location following their preferred habitat, so repeated photography can be necessary. Specifically, for the northern region, the USFS Stand Health map (Aerial Detection Survey maps) shows that the major impact (many very large polygons throughout the area) is defoliation by Western Spruce Budworm. The defoliation was categorized as mostly low severity (equal to or less than 50% defoliation) and some high (with greater than 50% defoliation) on Abies species and the damage is contiguous or nearly continuous. The forest type was categorized as W. Fir-Spruce. There was also defoliation by Western Spruce budworm on Douglas fir, but to a much lesser degree. Larch casebearer, a defoliator of LAOC, and generalized needlecast of western larch was also found to a much lesser degree. Scattered small polygons were found throughout the region including mortality from: Mountain Pine Beetle on lodgepole pine, Douglas fir Beetle on Douglas fir, Spruce beetle on Engelmann spruce, Fir engravers on ABIES spp., and Woolly adelgid on Abies spp., and general subalpine fir Mortality. Both of these would effect this ecological site and field notes corroborate these findings.

Submodel

Description

Another disease affecting this 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: identify the type of Armillaria root disease you are managing, manage for pines, 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 may be more at risk than other areas to root disease (Kimsey et al., 2012). If a stand sustains very high levels of roots 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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