Ecological dynamics

Ecological Dynamics of the Site
The Lower Subalpine Coniferous Cool Moist and the Lower Subalpine Coniferous Cool Moderately Dry ecological sites are the most expansive forested areas within Glacier National Park (GNP). This grouping is divided into moister versus drier aspects. This ecological site relates to the moderately drier aspect of this grouping, and is indicated by beargrass (Xerophyllum tenax) as the indicator species. This ecological site is in cool, moderately dry mid-elevations that span the lower subalpine zone. While primary data was collected in Glacier NP, this habitat type also spans into the adjacent US Forest Service (USFS) land Flathead National Forest (NF), and, in limited areas, the Kootenai NF.
Management
Various management strategies can be employed for the lower subalpine coniferous cool moderately dry 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 the habitat type subalpine fir/queencup beadlily is 248+/- ft2 per acre and site index at 50 years for Picea is 66 +/- 6 feet, and for Abies it is 59+/-6 feet. Timber production on these sites vary from low to very high, and are important for water production. The drier phases are less productive for timber and water than the wetter phases. Timber production is lowest in the beargrass phase of the Cryic/Udic Coniferous ecological site, and site preparation is needed for prompt seedling establishment in this driest phase. 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, 2001 and Appendix B). Another guiding USFS document is the Green et al. document (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, 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 subalpine fir/queencup beadlily 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/queencup beadlily on the Flathead NF.

The subalpine fir/ queencup beadlily habitat type is common, but colder types dominate the Flathead NF. This type 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. 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 Flathead NF. Starting sixty years ago, they regenerated very many of this habitat type. Management also is needed to employ intense methods to allow for scarification of the soil, which is a regeneration requirement of western larch. These methods include harvesting using skid trails, and prescribed burns for site preparation, but the 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 Wilderness Urban Interface (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, 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, it might fall within the snowshoe hare screen for the Lynx Amendment and will be managed for lynx habitat. 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.
State 1.0
Western white pine (Pinus monticola)/subalpine fir (Abies lasiocarpa)-Engelmann spruce (Picea engelmannii)/thinleaf huckleberry (Vaccinium membranaceum)/common beargrass (Xerophyllum tenax)-queencup beadlily (Clintonia uniflora)
Historically, western white pine would have been within Flathead County, Montana, 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, 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. Western white pine is 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, meaning it has high ecological flexibility. Western white pine 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. Moisture and soil temperature determine seed germination onset. Fire greatly influences the composition, structure, and function of vegetation across the landscape. Historically, this ecological site had mixed severity fire in between severe stand-replacement fires. Western larch and western white pine are long-lived, fire-adapted, shade-intolerant tree species that historically thrived. Also present in significant amounts, particularly in young stands, but declined through time due to the 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 in areas 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. A study of pathogens and insects effects 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 beetle were the causes 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, and 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 was 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 2.0
Subalpine fir-Engelmann spruce/Sitka alder/Thinleaf huckleberry/beargrass-queencup beadlily
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 and western spruce budworm, and by 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.

Currently, 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 tall shrub Sitka alder (Alnus viridis), the mid-height shrub thinleaf huckleberry (Vaccinium membranaceum), with an understory of beargrass (Xerophyllum tenax) and queencup beadlily (Clintonia uniflora). The queencup beadlily phase specifically represents the middle or average environmental conditions, and is the most common type. Subalpine fir, Engelmann spruce, western larch, Douglas-fir, and lodgepole pine are present in decreasing abundance. Queencup beadlily is the indicator species for all phases of this habitat type, but other commonly-occurring species specifically for this phase include fragrant bedstraw (Galium triflorum), threeleaf foamflower (Tiarella trifoliata), Oregon boxleaf (Paxistima myrsinites), thimbleberry (Rubus parviflorus), and thinleaf huckleberry (Vaccinium membranaceum). Other frequently occuring species for this ecologcial site include Rocky mountain maple (Acer glabrum), Sitka alder (Alnus viridis sitchensis), white spirea (Spirea betulafolia), heartleaf arnica (Arnica cordifolia), mountain brome (Bromus marginatus), western meadowrue (Thalictrum occidentale) and beargrass. The other phase of this type (beargrass) represents the dry, colder portion of the habitat type on well drained sites, i.e. south- and west-facing slopes. It has the same indicator species in the understory, but is dominated by beargrass.

This ecological site is described as having cool and moderately dry site conditions and 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 hemlock and western redcedar, and not cold enough for whitebark pine. The historic fire regime of these forests is one of low frequency (about 128 years) and high intensity, and therefore has an increased chance of stand-replacement fire when it does occur, due to site conditions, relatively high loadings of live and dead fuels, and periodic summer drought. The drier phases of this habitat type described in this site may have more frequent fires of lower to moderate severity than the moister phases. 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. Underburns, which affect 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 and western larch, or western white pine over lodgepole pine, Engelmann spruce, and subalpine fir. Therefore, these species would dominate the maturing forest phase for a longer period of time. After a stand-replacement fire at this stage with serotinous lodgepole pine present, the seedlings will 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 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 it will continue into the Reference phase. Significant fires that have occurred on the west side of the Continental Divide that affected the Cryic/Udic Coniferous ecological site are the 1994 Starvation Creek fire, caused by lightning, which burned 7,202 total acres, 4,001 of which were in Glacier NP, and the 2003 Wedge Canyon fire, also caused by lightning, which burned 53,359 total acres, 30,314 of which were in Glacier NP. The 1988 Red Bench fire was caused by lightning and burned 36037 total acres, 27,500 of which were in Glacier NP.
The lightning-caused Moose fire in 2001 burned 27,194 acres in Glacier NP, and 70605 total acres. The 2003 Robert fire was caused by humans and burned 52,747 total acres, 39,384 acres of which were in Glacier NP. The Harrison fire in 2003 burned 5,864 acres in Glacier NP, caused by lighting. Finally, the 2003 Rampage fire, caused by lightning, burned 21,630 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 that result in small openings scattered throughout the forest or major mortality during an outbreak, such as of western spruce budworm (Choristoneura occidentalis). The patterns of damage from endemic populations of insects and disease create 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 (Aerial Detection Survey maps, 2014) shows that the major impact to this area is defoliation by western spruce budworm. The defoliation was categorized as mostly of low severity (equal to or less than 50 percent defoliation) and some of high severity (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 also was 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 western larch also was found to a much lesser degree. Scattered small areas of damage 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 spp., and general subalpine fir mortality. Any of these would affect the Cryic/Udic Coniferous 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 overstory canopy cover averages 40-50 percent. The understory is multistoried with tall shrubs Sitka alder, Rocky mountain maple with a lower shrub layer including thinleaf huckleberry and white spirea. The lower layer includes shrubs, grasses and forbs with the most frequently occurring including beargrass, threeleaf foamflower, western meadowrue, thimbleberry, Oregon boxleaf, heartleaf arnica, mountain brome and queencup beadlily (18 sites canopy cover data). The foliar cover (6 sites dataset) is high at this community phase (68 percent), with very high cover of total litter on the ground (93% percent, 87% is duff), moderate cover of moss (8 percent) and very low cover of gravel and bare soil (4%). This community has an overstory of trees ranging from 80 to 100 feet tall. The understory is multi-layered with the tall layer growing 30-40 inches tall (Utah honeysuckle, Sitka alder, Rocky Mountain maple, red baneberry), the next layer is 20-30 inches tall (common snowberry, serviceberry, thinleaf huckleberry), and the lower layer is 10-20 inches tall (white spirea, rose species, beargrass, thimbleberry), the lowest layer is below 10 inches (pinegrass, queencup beadlily, Geyer’s sedge, prince’s plume, heartleaf arnica, darkwoods violet). 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 multistoried as well, with the tall Sitka alder in clumps, the medium-height thinleaf huckleberry throughout, and the herbaceous layer varied, but with the beargrass phase type dominated by that species. This ecological site must have a presence of queencup beadlily, 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-an insect infestation, wind storm or rot pocket 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 disturbance such as a high-intensity fire, large-scale wind event, or major insect infestation
Community Phase 2.2: Subalpine fir-Engelmann spruce (western larch-lodgepole pine)/Sitka alder/thinleaf huckleberry/beargrass-queencup beadlily

Structure: Mosaic of mature overstory and regenerating openings

Community Phase 2.2 retains some areas that resemble Community Phase 1.1, but also contains moderate-sized (2-5 acres) openings. The canopy cover ranges from 50-60 percent. Subalpine fir and Engelmann spruce are both hosts to organisms causing root rot and heart rot, and combined with windthrow large pockets of overstory mortality may occur. These areas may take decades to become reforested, resulting in either patches of shrubs or seral species such as western larch and lodgepole pine. 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, 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 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: Thimbleberry/Arnica species-western showy aster/mountain brome
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 upon 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, then this species will dominate the area. Queencup beadlily is present at this community phase. Species occurring with high frequency include fireweed, queencup beadlily, thimbleberry, white spirea, western meadowrue and beargrass. Fireweed, western showy aster and snowbush ceanothus can have infrequent, high canopy cover.
Community Phase Pathway 2.3A
This pathway represents continued growth over time with no further major disturbance

Community Phase 2.4: Lodgepole pine (Douglas-fir)/white spirea-thinleaf huckleberry/pinegrass-beargrass

Structure: Dense single story
Community Phase 2.4 is a forest in the competitive exclusion phase, possibly with scattered remnant mature trees; competition is increased among individual trees 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 and queencup beadlily. This community is more tolerant of Armillaria root rot due to forest stand composition, but is subject to defoliation by western spruce budworm on fir. The understory is multistructured with the tall shrub layer including serviceberry and Greene’s mountain ash. The lower shrub layer includes white spirea, thinleaf huckleberry and Rocky mountain maple and thimbleberry. The lowest layer includes queencup beadlily, beargrass, heartleaf arnica and pinegrass (14 sites of canopy cover data).
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 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: Subalpine fir-Engelmann spruce (western larch, lodgepole pine)/Rocky mountain maple/thinleaf huckleberry-white spirea-thimbleberry/queencup beadlily-beargrass

Structure: Single story with few small openings

Community Phase 2.5 is a maturing forest which is starting to differentiate vertically. Canopy cover averages 60 percent. Individual trees are dying 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. Species occurring most frequently at this community phase include the tall shrub Utah honeysuckle, medium statured shrubs Rocky mountain maple, thimbleberry, Oregon boxleaf, white spirea, thinleaf huckleberry and the lowest layer of queencup beadlily, twinflower, western meadowrue, threeleaf foamflower, darkwoods violet and beargrass. Species that occur infrequently, though in high canopy cover including Sitka alder and heartleaf arnica.
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 Lower Subalpine Coniferous Cool Moderately Dry 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 the 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 root disease mortality, then a coniferous stand could cross a threshold and become a shrubland, once all conifers are gone (Kimsey et al., 2012).