Ecological dynamics

Ecological Dynamics of the Site
This ecological site is found in cool, moist mid-elevations that span the lower subalpine through the subalpine zone. While primary data was collected in Glacier National Park (NP), this ecological site also occurs on the adjacent US Forest Service (USFS) Flathead National Forest (NF) land and in limited areas of the Kootenai NF. Associated sites to the 43A SUBALPINE COOL MOIST CONFEROUS ecological site include subalpine fir/queencup beadlily-rusty menziesia (ABLA/CLUN2-MEFE) at lower elevations, subalpine fir/Hitchcock’s smooth woodrush (ABLA/LUGLH) at higher elevations, subalpine fir/beargrass (ABLA/XETE) in drier areas, and subalpine fir/bluejoint (ABLA/CACA4) in very wet sites or wetland areas.

Management
Various management strategies can be employed for the 43A SUBALPINE COOL MOIST CONFEROUS ecological site, depending upon the ownership of the particular land and which value is prioritized. The management of the forest determines the composition of the stand and the amount of fuel loading. A stand will be managed differently and look differently if it is managed for timber or ecological services like water quality and quantity, old growth, or endangered species. If a stand is managed for timber, it may be missing certain attributes necessary for lynx habitat. If a stand is managed for lynx habitat, it may have increased fuels and therefore an increased risk of wildfires.

The USFS Habitat Type guide states that the basal area on the West side of the Continental Divide for ABLA/MEFE is 172+/- ft2 per acre and the site index at 50 years for Picea is 60 +/- 10 and for Abies 57+/-9. Timber production on these sites vary from moderate to high. Intensive management for timber production can have problems including partial cutting, which can increase shade-tolerant subalpine fir or lack of regeneration under the dense shrubs of rusty menziesia and Sitka alder. Site preparation by dozer scarification or prescribed burning on steep areas is essential. Prescribed burning can be accomplished only when fuels are dry on this rather moist site. Watershed values are high for this site. The management of USFS lands is encompassed in the management plan for each National Forest. The management plan for the Flathead NF also has an Appendix B that gives specific management guidelines for habitat types (which relate to our forested ecological sites) found on the forest in relation to current and historic data on forest conditions (Flathead NF Plan, 1998 amended 2001 and Appendix B). Another guiding USFS document is the Green et al. document, 1992 amended (2005) which defines “Old Growth” forest for the northern Rocky Mountains. This document provides an ecologically-based classification of old growth based on forest stand attributes including numbers of large trees, snags, downed logs, structural canopy layers, canopy cover, age, and basal area. While this document finds that the bulk of the pre-settlement upland old growth in the northern Rockies was in the lower elevation areas, ground fire-maintained ponderosa pine/western larch/Douglas-fir types (Losensky, 1992), it does not mean that other types were not common or not important. This could apply to some of the areas of this ecological site.

The USFS Habitat Type ABLA/MEFE is common on the Flathead NF, located just west of Glacier NP. The following is a personal communication with a silvicultural forester on management of subalpine fir/rusty menziesia (ABLA/MEFE) on the Flathead NF (Reichenberg, 1/2016):

This habitat type (HT) is common, but colder types dominate the Flathead NF This is managed to promote western larch and western white pine. These species are tolerant or resistant to root disease and insect outbreaks (much more so than subalpine fir, Engelmann spruce or Douglas-fir). Site preparation is key! Rapid and aggressive shrub response to sunlight. Planting is important to establish favored seral species before shrubs occupy site. Use large scalps (area of bare mineral soil created by the tree planter with hoedad) when planting to deter competing vegetation. This HT can grow some great picea species. I try to mix some in with the planting prescription. Currently, there is an uptick of western spruce budworm potentially brought on by the current drier weather conditions. Another reason to promote western white pine is that it is expected to be adaptable in the face of climate change and to restore this species to the landscape after the significant mortality caused by the introduction of white pine blister rust. The current generation of resistant western white pine seedling stock shows up to 60 percent survival against white pine blister rust. Historically, this habitat type was managed using traditional even age strategies on the FNF. Management also needed to employ intense methods to allow for scarification of the soil which is a regeneration requirement of western larch. These methods included harvesting using skid trails and prescribed burns for site preparation. These methods are constrained because of soil and air quality concerns. Therefore, planting of western larch is employed instead and there is competition by Canada thistle and grass. As well, management on this habitat type is further constrained by concerns for Lynx habitat. Unless a unit is classified as WUI or is managed for western white pine, there is no pre-commercial thinning allowed in this habitat type. This inability to thin stands could cause forest stand health issues with root disease or insect outbreaks if the stand has significant density of the vulnerable species of subalpine fir, Engelmann spruce or Douglas-fir. The inability to thin also greatly affects the diameter growth of individual trees. Traditional even-aged management on this type consists of pre-commercial thinning followed by commercial thinning to grow older larger western larch. A seed tree harvest leaving western larch and western white pine and large diameter Douglas fir and western larch snags for wildlife is used to regenerate a new stand. If a stand has sufficient subalpine fir, then it might trip the snowshoe hare screen for the Lynx Amendment and then left alone. Multi-story structure of a stand and minimum cutting unit size is important for lynx habitat. As well, if a unit is deemed old growth then it is left alone even if these conditions make it susceptible to root rot or insect damage because these conditions are consistent with forest succession on this habitat type.

Associated Sites
43A Montane Steep Stable Colluvial Slope
43A Lower Subalpine Coniferous Cool Moist Ashy Very Deep, (ABLA/CLUN2-ARNU2)
43A Upper Subalpine Cold Coniferous, ABLA/LUGLH)
The 43A Montane Steep Stable Colluvial Slope ecological site is found on steep slopes with vegetation cover ranging from impenetrable shrubs to open canopy of medium statured shrubs with lush understory of grass and forb species. Steep sites on valley walls. The thick vegetative growth contributes to the dark surface horizon colors in these soils. The reference vegetation community is Saskatoon serviceberry (Amelancheir alnifolia), common snowberry (Symphoricarpos albus), Sitka alder (Alnus viridis ssp. sinuata), Rocky mountain maple (Acer glabrum), thimbleberry (Rubus parviflorus), mountain brome (Bromus marginatus) and Geyer’s sedge (Carex geyeri).

The 43A Lower Subalpine Coniferous Cool Moist Ashy Very Deep, (ABLA/CLUN2-ARNU2) has a reference vegetation community of Subalpine fir-Engelmann spruce overstory and an understory of Rocky Mountain maple, thinleaf huckleberry, thimbleberry, wild Sarsaparilla, threeleaf foamflower and queencup bead lily.

The 43A Upper Subalpine Cold Coniferous (ABLA/LUGLH) ecological site has a reference vegetation community of subalpine fir (and minor Engelmann spruce) with an understory of thinleaf huckleberry, rusty menziesia, Hitchcock’s smooth woodrush-beargrass and yellow avalanche lily.
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).
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. The historic extent of western white pine in Glacier National Park was primarily along the western border. 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, 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, susceptible to Armillaria root disease only when young, and 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 full sunlight. Fire greatly influences the composition, structure, and function of vegetation across the landscape. Historically, the area had mixed severity fires in between severe stand-replacement 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 declined through time due to effects of insects and pathogens, were 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. Western white pine was a major component in forested ecosystems of the inland northwest U.S. prior to the 20th century, 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 pathogens and insects effects on forests within the Inland Empire found that, excluding fire, there were 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 beetle 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. 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 Hagel, 2000). These stands are also less productive in terms of timber. They also are dominated by species with high nutrient demands, in areas 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. There has been a total of approximately 5 percent of the original acre range 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).
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.

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 rusty menziesia that is patchy or dense, the tall height shrub Greene’s mountain ash and Utah honeysuckle, and other medium-sized shrubs such as thinleaf huckleberry with an understory of beargrass, sidebells wintergreen, threeleaf foamflower and darkwoods violet. Subalpine fir, Engelmann spruce, western larch, Douglas-fir, western white pine, and lodgepole pine are present in order of decreasing abundance. The rusty menziesia (MEFE) indicated type specifically represents areas that are cold and moist. It is more common on cool northern and eastern exposures, and where rusty menziesia and broadleaf arnica (ARLA8) are abundant. Historically, this site would have had western white pine before this species was decimated by the white pine blister rust epidemic (Mcdonald et al., 2000).

This ecological site is described as having cool and moist site conditions and high species diversity in the overstory. 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 there is an increased chance of stand-replacement fire when it does occur due to moist site conditions and relatively high loadings of live and dead fuels, combined with periodic summer drought. Stand-replacement fires occur in patches of 200 to 2,000 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. Understory burns, which effect the understory shrub and herbaceous species and conifer regeneration the most, can occur and maintain any community phase. A stand-replacement 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, and subalpine fir. Therefore, these species would dominate the maturing forest phase for longer periods of time. After a stand-replacement fire at this stage with serotinous lodgepole present, these 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 the Douglas-fir, leaving the site to be regenerated by either serotinous lodgepole 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 and affected this ecological site are the 1994 Starvation Creek fire, which burned 4,001 acres in Glacier NP and 7,202 in total, caused by lightning. The Wedge Canyon fire in 2003 burned 30,314 acres in Glacier NP, 53,359 total acres, and was caused by lightning. The 1988 Red Bench fire burned 27,500 acres in Glacier NP, and a total of 36,037 acres, also caused by lightning. In 2001, the Moose fire burned 27,194 acres in Glacier NP and 70,605 total acres, caused by lightning. The 2003 Robert fire burned 39,384 acres in Glacier NP, 52,747 total acres, and was caused by humans; while lightning caused the Harrison fire that same year, burning 5,864 acres in Glacier NP and the Rampage fire, which burned 21,630 acres in Glacier NP.

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 and result 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 commonly can cause additional damage to stands following disease and pest disturbance. Subalpine fir is most commonly susceptible to Armillaria and Annosus root disease, pouch, Indian paint, and red belt fungi 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 needlecast, snow blight, and fir-blueberry rust. Engelmann spruce is most commonly susceptible to Annosus and Schweinitzii 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, spruce canker, and brown felt blight.

Aerial photography is 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. These maps capture only moments in time, 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 shows that the major impact is defoliation by western spruce budworm. The defoliation was categorized as mostly low severity (equal to or less than 50 percent defoliation) and some as high (with greater than 50 percent defoliation) on Abies species, and the damage is contiguous or nearly continuous. The forest type was categorized as western Fir-Spruce type. There was also defoliation by Western Spruce budworm on Douglas-fir, but to a much lesser degree. Larch casebearer, a defoliator of western larch, and generalized needlecast of larch was also found to a much lesser degree. Scattered small areas 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 and woolly adelgid on Abies species, and general Abies species mortality. All of these would affect this ecological site and field notes corroborate these findings.

Community Phase 2.1
Structure: multistory with small gap dynamics
The overstory is dominated by subalpine fir and Engelmann spruce, with small gap dynamics in which small numbers of trees are dead and conifer regeneration is infilling. The canopy cover ranges from 40-60 percent. The understory is dominated by a shrub layer in which the indicator species, rusty menziesia, is present and may be dominant. Species with high frequency of occurrence in 7 canopy cover sites include: thinleaf huckleberry, beargrass, Greene’s mountain ash and rusty menziesia. Foliar cover (taken at three sites) is high at this community phase, and the ground cover predominantly consists of very high cover of duff (86%) with a low amount (<5%) of moss, bare soil, and stones. The vegetation structure at this community phase is that of tall trees (700 inches on average) with a tall shrub layer of Menziesia ferruginea at 90 inches, and a lower layer of shrubs and forbs at 20 inches including beargrass, white spirea, fireweed, thinleaf huckleberry, and Oregon boxleaf. At these higher elevations both tree species are slow-growing and infill can take several decades, sustaining the multistory structure of this community. The presence of root rot pockets can shift the composition of this community away from its host species. The understory of this community is defined by the medium-sized shrub rusty menziesia in either clumps or dense thicket. The tall shrub Greene’s mountain ash and the medium-sized thinleaf huckleberry is also prevalent. The understory has beargrass and moss. This ecological site must have a presence of rusty menziesia and sometimes this is dominant. At this phase, Armillaria root rot and defoliation by western spruce budworm can be a threat.
Community Phase Pathway 2.1A
This pathway represents a larger disturbance, such as an insect infestation, wind storm, or rot pocket that would create this forest structure. Areas of regeneration would range from approximately 2 to 5 acres.

Community Phase Pathway 2.1B
This pathway represents a major stand-replacement fire disturbance such as a high-intensity fire, large-scale wind event, or major insect infestation.

Forest Overstory
Forest canopy: Canopy cover ranges from 40-60 percent
Average basal area: Total 260 ft2/acre
Site Index at 100 yrs.: ABLA ranges from 30-57
CMAI ABLA 26@130yrs. 45@125yrs.
Community Phase 2.2
Structure: mosaic of mature overstory and regenerating openings
Community Phase 2.2 retains some areas that resemble Community Phase 2.1, but also contains moderate-sized (2-5 acres) openings. Subalpine fir and Engelmann spruce are both host to organisms causing root rot and heart rot, and with windthrow can cause large pockets of overstory mortality. These areas may take decades to become reforested, resulting in either patches of shrubs or seral species such as western larch and Douglas-fir. As the organisms slowly die off due to a lack of host trees, subalpine fir, and Engelmann spruce will re-colonize these areas. This community can be prone to Armillaria root rot and western spruce budworm on fir.

Community Phase Pathway 2.2A
This pathway represents growth over time with no further significant disturbance. The areas of regeneration pass through the typical stand phases-competitive exclusion, maturation, and understory reinitiation until they resemble the old-growth structure of the Reference Community.

Community Phase Pathway 2.2B
This pathway represents a major stand-replacement fire disturbance, such as a major insect outbreak, or major fire event, which leads to the stand initiation phase of forest development.

Community Phase 2.3
Structure: patchy clumps of regeneration-single story

Community Phase 2.3 is a forest in the stand initiation phase, possibly with scattered remnant mature trees; the composition of the seedlings depends on the natural seed sources available. The canopy cover is generally less than 10 percent as a mixture of conifers including Douglas-fir, lodgepole pine, western larch, Engelmann spruce, and subalpine fir. If serotinous lodgepole seedbank is present, it will dominate the area.

Community Phase Pathway 2.3A
This pathway represents continued growth over time with no further major disturbance.

Community Phase 2.4
Structure: dense single story
Community Phase 2.4 is a forest in the competitive exclusion phase, possibly with scattered remnant mature trees; individual trees compete for the available water and nutrients. The canopy cover ranges from 50-80 percent. Canopy closure is very high within the areas successfully reforested, leading eventually to a diminished graminoid community, but also providing protection for those species which do well in the shade, such as prince’s pine. This community is more tolerant of Armillaria root rot due to forest stand composition, but is vulnerable to defoliation by western spruce budworm on fir. The understory at this community phase of this ecological site has a thick shrub layer, including rusty menziesia and grouse whortleberry and thinleaf huckleberry and forbs sidebells wintergreen and beargrass.
Community Phase Pathway 2.4A
This pathway represents continued growth over time with no further major disturbance.

Community Phase Pathway 2.4B
This pathway represents a major stand-replacement fire disturbance, such as a major insect outbreak, or major fire event which leads to the stand initiation phase of forest development.

Community Phase 2.5
Structure: single story with few small openings
Community Phase 2.5 is a maturing forest which is starting to differentiate vertically. The canopy cover ranges from 30-80 percent, and is a mixed conifer overstory including subalpine fir, Engelmann spruce, Douglas fir, and lodgepole pine. The understory is dominated by the medium-statured shrubs rusty menziesia, thinleaf huckleberry, and beargrass can have high cover. Other species that occur frequently include Utah honeysuckle, sidebells wintergreen, threeleaf foamflower, darkwood violet. Individual trees are dying (whether due to insects, disease, competition, or windthrow), allowing some sunlight to reach the forest floor. This allows for an increase in the understory as well as some pockets of overstory tree species regeneration. This community is prone to Armillaria root rot and western spruce budworm on fir.
Community Phase Pathway 2.5A
This pathway represents no further major disturbance. Continued growth over time, as well as ongoing mortality, leads to continued vertical diversification. The community begins to resemble the structure of the Reference Community, with small pockets of regeneration and a more diversified understory.

Community Phase Pathway 2.5B
This pathway represents a major stand-replacement fire disturbance, leading to the stand initiation phase of forest development.

State 3.0
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).