Lower Subalpine Moderately Warm and Moist Coniferous Pend Oreille-Kootenai Valleys grand fir/bride's bonnet

Description

The historic State would have western white pine as a long-lived seral species in which the reference phase dominated by Grand fir would not be prevelant across landscape scales due to fire disturbance cycles and longevity of seral phases dominated by western white pine. Historically western white pine would have been within Lincoln County, which encompasses part of the Kootenai N.F., and in smaller islands stretching east to 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 five 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, 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, it was mixed severity fire 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 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 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. It 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 western 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% 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 continuation of this trend occurring in low-density mature stands and younger pole-sized stands that result from root disease and bark beetle-caused mortality (Byler and Hagel, 2000). These stands also are less productive in terms of timber. They are dominated by species with high nutrient demands, and therefore 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. Approximately 5 percent of the original acre range was re-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, 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. It 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 once 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. State 2 forests are now dominated by the shade-tolerant climax species Grand fir. While there is a tremendous effort to bolster the numbers of western white pine, it currently covers only 5 percent of its historic range.

This ecological site is described as having moderately warm and moist site conditions in elevations between 731 to 1534 meters (2,400 to 5,000 feet) in valley bottoms and benches on all aspects in western Montana. The vegetation community is mainly determined by the inland maritime climate and long fire free interval. The Reference state is dominated by Grand fir which is a shade-tolerant climax conifer. After a major disturbance, numerous seral species can occur though Grand fir is the main shade tolerant species that continues to reproduce from the pole size to mature size phases. Moist site understory species are common including queencup beadlily, American trailplant, drops of gold, fragrant bedstraw, Rocky mountain maple, Saskatoon serviceberry, white spirea and common snowberry.

The historic fire regime of these forests leads to a very diverse mosaic of landscapes due to various fire severities, intervals and patterns. It is a mixed severity regime with low and moderate severity fire more frequent and severe fire at much longer intervals. Therefore, it is one of generally low fire frequency, but fire severity can be highly variable. It can be low due to the most common moist conditions but can be severe during times of drought. Fire severity is enhanced due to the very high fuel loading in this ecological site. Historic fire return intervals were non-uniform, including mixed severity fires on 30-85-year intervals, as well as stand replacement fires on a 100-200 year intervals (VRU KOOTENAI). This finding is corroborated by the Landfire model. The Northern Rocky Mountain montane mixed-conifer forest, which spans through the north Idaho, western Montana and northeastern Washington, is based on the LANDFIRE Biophysical Settings (BpS) data layer of the forest succession model. This group had a fire interval of 10 to 80 years, with 11 to 52 percent of fires classified as of replacement severity and 14 to 69 percent of fires classed as mixed severity and 0 to 75 percent as low severity (USDA, USFS, FEIS, Fire Regime). This ecological site is in fire regime group 11 (Warm, Moist Grand fir, western redcedar, and western hemlock habitat types), of the western Montana fire ecology grouping (Pfister). Generalities for the role of fire in this moist environment with highly variable fire severities include: fire creates a mineral seedbed for climax and seral species regeneration, it creates a mosaic of seral and climax communities across the landscape and it affects within stand tree species composition. A fire history study of the Grand fir/queencup beadlily habitat type in the Swan Valley in western Montana, found fire return intervals of 100 to 200 years for stand replacing fires. The fuel loadings for this very productive ecological site can be very high (averaging 25 tons per acre, the highest of any fire group in western Montana) due to deadfall and natural thinning of small and medium-sized branches. In early and intermediate successional phases, the understory can have high cover adding to fuel loadings. Due to the generally moist conditions, fire return intervals can be long with fuels building up between fires. In general, the variability in fire regime and the high diversity of tree species present in most stands, allow this ecological site to form a diverse mosaic landscape with varying dominance or mixes of seral species. Species composition post fire is not solely determined by fire severity, rather species composition before fire, species within the onsite seedbank, offsite seeding and seedling establishment success play a larger role in this fire group than in others in western Montana.


The general fire succession process is that after stand replacement fires in the reference phase of Grand fir with lesser Douglas fir, western white pine and western larch, the community reverts to an herbaceous one, then to shrubland. If fire is reoccurring in this phase, then the phase is maintained for a long time. The herbaceous community can be dominated by the disturbance-loving fireweed, beargrass, or numerous other species, depending upon the seedbank at the site and beyond. Duration of the herbaceous or shrubland phase is also dependent upon the availability of tree seed. There are different seral communities that will develop depending on seedling establishment.


If serotinous lodgepole pine seeds are available, then the site will become dominated by it and a lodgepole pine stand will develop for about 10 to 25 years (Habeck, 1968). After that time, other species become established including western larch and other conifers. A fire in the early pole sized stage, severe enough to kill young western larch will return the site to an herb and then shrubland and then to a pure lodgepole pine seral forest. If serotinous lodgepole pine seeds are not present, then the seedlings are a very diverse mixture of conifers. These seedlings form a thick carpet on the site shared with shrub species such as Scouler’s willow, white spirea, thinleaf huckleberry, thimbleberry, and Oregon boxwood. Forbs present include ferns, beargrass and fireweed. Moss cover can be variable. If fire does not occur, the seedlings will grow to saplings and then pole-sized trees of diverse seral species. Low to moderate fires in this stage would favor fire-tolerant seral species over grand fir, which is less fire-resistant. Severe fires will return these to the herbaceous or shrubland phase. Various scenarios can result if one seral species is more successful in seedling establishment than other species. If lodgepole pine is not present, or the seeds are non-serotinous and or low in number, and western larch is present, numerous and has successful seedling establishment, it will dominate the post fire regeneration with lesser Douglas fir, western white pine, lodgepole pine and grand fir. Douglas fir will establish quickly, and later grand fir will establish as well and in time become co-dominant with western larch. If neither western larch nor lodgepole pine seedlings establish, then Douglas fir with seedlings present, will dominate the early seral seedling establishment.
In the pole-sized phase, seral species are abundant and grand fir is just becoming established and usually has low cover (3 to 15 percent of the stand). Without further disturbance, this phase will continue to the maturing forest in which grand fir becomes more evident in the stand and eventually has higher cover than the seral tree species. Western larch may survive severe fires in the maturing or mature phases. These trees would then provide seed for the stand initiation phase after a fire. As well, after frequent low to moderate fires in the mature phase, a relict western larch stand could occur. Reference stands in which only grand fir occur can be rare, as seral species are long-lived and fire occurs frequently enough that stands seldom develop beyond the mature phase. Reference stands may withstand low fires that thin the stand, but moderate or severe fires would return the site to the herbaceous or shrubland phase.

Significant fires have occurred within this land resource unit in 1889 and in 1910. These fires were huge in size and severity. Since that time there have been extremely few fires of any substantial size (over 10 acres), except in 2015 in which one fire did encroach on this valley area from the adjoining mountains.

Grand fir is subject to a variety of diseases and insect pests. Most notably, Armillaria and Annosus root diseases affect the roots with the former causing death of trees in patches. Stem decays are also a concern, including Pouch fungus, Indian paint fungus and red belt fungus. Other stem damagers include blue stain of sapwood and fir canker, the latter also affects branches and terminals. Wood borers include metallic wood borers, roundheaded borers and fir engravers. Damage to the foliage can be caused by Western spruce budworm, Delphinella shoot blight, black mildew, fir needle cast, snow blight, fir-fireweed rust and fir-blueberry rust. This is a list of the common species affecting Grand Fir, but abundance of each is determined by location.

A good tool to use to discern the levels of insects and diseases, the damage patterns, and whether these are at endemic or epidemic levels is aerial photography. These maps (USFS Aerial Detection) 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 this LRU, the most common damage was Lophodermium needle cast of pines by Lophodermium species. This foliage disease affected ponderosa pine by defoliation and the severity was low, defined as equal to or less than 50 percent defoliation of an area. The pattern was defined as relatively continuous. To a minor extent, there was tree mortality due to the western pine beetle on ponderosa pine. Generally, in the northern region, the USFS Stand Health map shows, via many very large polygons throughout the area, that the major impact 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 W. Fir-Spruce. 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 disease of western larch also was found, to a much lesser degree. Scattered small polygons showing damage were found throughout the region, including mortality from mountain pine beetle on lodgepole pines, Douglas-fir beetle on Douglas-fir, spruce beetle on Engelmann spruce, fir engravers and woolly adelgid on Abies species, and general Abies species mortality. These would affect the seral tree species of this ecological site and field notes corroborate these findings.

Submodel

Description

Another disease affecting this ecological site is root rot. Douglas-fir, grand fir, and subalpine fir are the most susceptible species. Armillaria root disease is the most common root disease fungus in this region, and is 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 effects the tree species most susceptible 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. The common disease expression is some mortality in saplings, and residuals of partial harvests often develop severe infections but are very slow to die (Hagle, 2010). There has been a link determined between parent material and susceptibility to root disease (Kimsey et al., 2012). Metasedimentary parent material is thought to increase the risk of root disease. Areas dominated by metasedimentary parent material 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). Management tactics include to identify the type of Armillaria root disease, 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 (Hagel, 2010).

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