Ecological dynamics

Plant Community Dynamics
The vegetation community that defines the 43A Alpine Shallow Meadow ecological site includes perennial snow-loving forbs and grasses, sedges, and rushes. This site is very diverse with early, mid, and late season blooming forbs. The defining species include yellow avalanche lily (Erythronium grandiflorum), Scouler’s St. Johnswort (Hypericum scouleri), alpine leafybract aster (Symphyotrichum foliaceum), Hitchcock’s smooth woodrush (Luzula glabrata var. hitchcockii), shortstalk sedge (Carex podocarpa). There is a constant presence of subalpine fir (Abies lasciocarpa), but it provides very low cover. Species at this site are not wetland obligates, rather some may have moderate affinity to wetlands while others to uplands.

This community goes through a phenological sequence of blooming. The earliest species to bloom, directly after snowmelt, is lanceleaf springbeauty (Claytonia lanceolata). This is followed by yellow avalanche-lily and then Hitchcock’s smooth woodrush. Shortstalk and smallwing sedges bloom in May through August. Next to bloom in June and July are pacific anemone (Anemone multifida), broadleaf arnica (Arnica latifolia), and nineleaf biscuitroot. Flowering from June through August are other Arnica species, autumn dwarf gentian (Gentianella amarella), Hitchcock’s smooth woodrush, and western meadow-rue (Thalictrum occidentale). In July and August, numerous species bloom including Aster species, splitleaf Indian paintbrush (Castelleja rhexifolia), western showy aster (Eurybia conspicua), Scouler’s St. Johnswort (Hypericum scouleri subsp. scouleri), arrowleaf ragwort (Senecio triangularis), Sitka valerian (Valeriana sitchensis), American alpine speedwell (Veronica wormskjoldii), and mountain deathcamas (Zigadenus elegans). Near summer’s end, the rushes bloom in July through September, including Drummond’s rush (Juncus drummondii) and Mertens’ rush (Juncus mertensianus). By mid-August, the subalpine fleabane blooms. Lastly, alpine leafybract aster (Symphyotrichum foliaceum) and sticky purple geranium (Geranium viscosissimum) bloom in August through September.

The 43A Alpine Shallow Meadow ecological site is found primarily on toeslope and backslope positions of cirque walls, colluvial aprons or saddles with smooth or linear slope shapes. It also is found in linear areas between ribbons of high elevation forests (whitebark pine-subalpine fir) found on cirque floors and walls, roche moutonées, and saddles. These landforms have the typical vegetation community of this ecological site. It can also be found on bedrock controlled areas which are gently rolling, undulating landforms with variable depths to bedrock resulting in more varied overall vegetation community with minor vegetation inclusions. On convex knobs within this undulating landform, there is a distinct increase in the presence of yellow mountainheath. These are interspersed between linear to concave positions with the vegetation community typical of this ecological site. There are only two instances in which obligate wetland species occur at this site, and these are patches of the dwarf shrub alpine laurel (Kalmia microphylla) and undergreen willow (Salix commutata) within concave positions that are often ponded, of this ecological site. On areas close to bedrock outcrops or ledges, with very shallow to shallow soils, there is predominance of shortstalk sedge (Carex podocarpa).

This community is considered intermediate in its snow-holding capacity: it holds less snow than the ecological site 43A Nivation Hollow (dominated by turf forming sedges), which can sit directly next to glaciers and perennial snowfields at the highest elevations, and has a concave position that holds snow longer than surrounding areas. The alpine shallow meadow ecological site, in contrast, is found primarily on toeslope positions of colluvial slopes or in gently rolling, slightly wind-protected positions on undulating landforms. Snow accumulates on these landforms and the growing season is only 3.5 to 4 months long. There are few species that tolerate these site conditions. Thus, there is an affinity of species between the Nivation Hollows and the Alpine Shallow Meadow vegetation communities, in that similar sedge species occur in both ecological sites, though in far different proportions. The Nivation Hollow community is dominated by sedges.

The 43A Alpine Shallow Meadow ecological site is generally moist and, for the most part, does not burn frequently. The closest fire regime to this ecological site is that of the Northern Rocky Mountain Alpine and Subalpine Meadows and Grasslands community (Landfire, 2005), which has a fire interval of 350 years for replacement fire interval and 750 years for mixed fire interval, the average for all fires is 239 years (Agee, 1993). The National Park Service (NPS) regards the fire return interval for the Logan Pass area (this area is dominated by the alpine shallow meadow ecological site) to be approximately 200 years, maybe up to 300 or more (personal communication, McClellan, NPS Fire Effects, 2016). Hitchcock’s smooth woodrush is a co-dominant at this ecological site. It is a short, rhizomatous perennial rush specie that regenerates into extensive colonies. It also reproduces via seed, which is dispersed by the splash cup method using raindrops, wind, or the vibrations of passing animals. It is considered an indicator of cold environments, found mainly where deep snow lies late at high elevations. Following fire, it resprouts from surviving rhizomes after the fire consumes all aboveground parts. Hitchcock’s smooth woodrush has been shown to increase in biomass following fire. Another of the main species found on this site is yellow avalanche-lily, a perennial forb with a deep corm. After fire, it can resprout from the corm. Yellow avalanche-lily is pollinated by bumblebees and other species of bees, and needs 100 days of cold stratification before germination. A fire would destroy that year’s seeds, preventing new plant establishment during the first post-fire year.

The 43A Alpine Shallow Meadow ecological site sustains disturbance from wildlife, particularly grizzly bears digging for the yellow avalanche-lily corms. Following digging disturbance, the seral progression proceeds from mineral soil colonized by moss species, then Hitchcock’s smooth woodrush, which forms a dense stand. Eventually, this is invaded by other forb species. Other animals that disturb this ecological site by digging for food or burrowing include gophers, marmots, voles, and other rodents. Yellow avalanche lily also is important forage for ground squirrels, sheep, cattle, horses, elk, and mule deer (Ellison, 1954).

Hansen et al. in 1995 found that certain species included in this site were generally good or fair forage for sheep, cattle, and horses including alpine leafybract aster, heartleaf arnica, fireweed, sticky geranium, and arrowleaf ragwort. These species were generally low in energy and protein value in the fall and winter. These species were general good to fair food value for elk, mule and whitetail deer, and antelope. Alpine leafybract aster and arrowleaf ragwort were deemed good to fair food value for upland, waterfowl, small mammals, and small non-game birds, while fireweed and sticky geranium were fair to poor in those categories.

The 43A Alpine Shallow Meadow ecological site is impacted by human trampling from visitors. In a long-term study monitoring visitor impact on Logan Pass in Glacier National Park, Hartley (2000) found that it took up to 30 years to recover after trampling treatments to pre-treatment ratios of vegetation, litter, and bare ground. Vegetation took 19-25 years to recover after trampling 15 times per week, and 25-30 years when trampled 50 times per week. In studies on trampling by Landals and Scotter (1973, 1974), it was found that the community type Sitka valerian subalpine forb meadow responded to repetitive trampling by a dramatic drop in canopy cover of 75 percent within 100 passes. It was categorized as being somewhat susceptible to both light and heavy trampling. This meant that it took 26-100 passes to reduce cover to 50 percent of the original condition. The relative cover after 800 passes was 8-15 percent, which was categorized as neither susceptible nor resistant. Alpine leafybract aster (Symphyotrichum foliaceum) was considered neither resistant nor sensitive to trampling, whereas heartleaf arnica and showy aster were considered sensitive species.

A yellow mountainheath subalpine meadow also was found to respond dramatically to trampling with a similar decrease in canopy cover. It was categorized as being somewhat susceptible to light trampling. This meant that it took 26-100 passes to reduce cover to 50 percent of the original condition. It was categorized as very susceptible to heavy trampling, meaning that relative vegetation cover after 800 passes was 0-3 percent.

Climate change may have an effect on this community. Altered temperature and precipitation regimes as well as changes in the extent of glaciers and snowpack will have a more pronounced effect on plants in the alpine. Plants in this ecological site are adapted to living in the harsh alpine environment with a short growing season. Changes to snowpack will particularly effect plants that are the earliest flowering species. Erythronium grandiflorum is one the earliest flowering species and was shown to flower earlier by 4.14 days per decade over a 30 year period (Lambert, 2010). Snowmelt was shown to be arriving earlier, which caused earlier flowering. Numerous animals rely on Erythronium grandiflorum and the shift in earlier flowering may have cascading effects. Queen bumblebees, broad tailed hummingbirds, elk, deer and grizzly beer rely on it for green vegetation food directly after snowmelt in early spring.
STATE 1.0:
Community Phase 1.1:
Yellow avalanche-lily (Erythronium grandiflorum)-Scouler’s St. Johnswort (Hypericum scouleri)-alpine leafybract aster (Symphyotrichum foliaceum)-Sitka valerian (Valeriana sitchensis)-heartleaf arnica (Arnica cordifolia)/Hitchcock’s smooth woodrush (Luzula glabrata var. hitchcockii)-shortstalk sedge (Carex podocarpa).
This community phase has high foliar cover and the ground cover is predominantly litter and duff, though can have moderate cover of soil and trace amounts of bedrock, stones, cobbles, gravel and moss. The vegetation structure is a fairly uniform two layers, one 10-20 inches tall and another layer below 10 inches tall of diverse forb and grass species. The tallest common specie, Alpine timothy (Phleum alpinum) can be 40 inches tall. Only thinleaf huckleberry which occurs sporadically and green false hellebore (Veratrum viride) can reach heights of 30 inches tall. The 10-20 inches tall layer can include sticky purple geranium (Geranium viscosissimum), yellow avalanche lily (Erythronium grandiflorum), broadleaf arnica (Arnica latifolia), aster, bromus and senecio species. The lower layer below 10 inches can include Payson’s sedge (Carex paysonis), Drummond’s rush (Juncus drummondii), shortstalk sedge (Carex podocarpa), Hitchcock’s smooth woodrush (Luzula glabrata var. hitchcockii), Scouler’s St. Johnswort (Hypericum scouleri), creeping sibbaldia (Sibbaldia procumbens) and other forbs and grasses.
Community Phase 1.2: This community has reduced foliar cover than community phase 1.1 due to grazing or trampling. There is an increase in bare ground cover and compaction of the soil. This community is at additional risk to crossing a threshold to State 2.0.
Community Phase 1.3: This community has sustained bear digging in which the soil has been churned over, aerating the soil and exposing buried plant propagules. The recovery time from this small scale disturbance is short. The seral progression is colonizing moss species, then Hitchcock’s smooth woodrush and perennial forb species re-establish on the site.

Community Phase Pathway 1.1a
This represents extensive animal trails or trampling by humans which lead to an increase in bare ground, compaction of soil, lowering of total foliar cover, change in species composition, and/or a lowering of total productivity of the site. Drought conditions would exacerbate the disturbance and lengthen recovery time. The disturbance may be extensive.

Community Phase Pathway 1.1.b.
This represents disturbance by bear digging and rodent burrowing, which lead to a churning of soil, aeration and exposure of buried plant propagules. This disturbance is small in area generally and the vegetation recovers quickly.

Community Phase Pathway 1.2.A.
This represents a resumption of production and composition by species to the reference state by a decrease in grazing or trampling by humans.

Community Phase Pathway 1.3A
This represents time without extensive bear digging in which the seral progression of colonizing moss species, Hitchcock’s smooth woodrush and perennial forb species re-establish on the site.

STATE 2.0:
Community Phase 2.1: This community has sustained a dramatic reduction in foliar cover, species production or even a change in species composition from the Reference Community (1.1) due to intense grazing or trampling.


Table 1. Canopy cover data for species present in community phase 1.1 for this ecological site including count of frequency and canopy cover values (average, minimum and maximum).

Minor vegetation community within this ecological site, found on convex positions:
Pink mountainheath (Phyllodoce empetriformis)-yellow mountainheath (Phyllodoce glanduliflora)/creeping sibbaldia (Sibbaldia procumbens)-subalpine fleabane (Erigeron peregrinus)/Payson’s sedge (Carex paysonis)-Hitchcock’s smooth woodrush (Luzula glabrata var. hitchcockii)-Mertens’ rush (Juncus mertensianus)-Parry’s rush (Juncus parryi). Foliar cover at this community phase is high and the ground cover is predominantly litter and duff with fairly high moss cover and trace cover of cobbles, gravel, lichen and soil. The vegetation structure is of one layer that is short, less than 10 inches tall and can include pink mountainheath (Phyllodoce empetriformis)-yellow mountainheath (Phyllodoce glanduliflora)/creeping sibbaldia (Sibbaldia procumbens)-subalpine fleabane (Erigeron peregrinus)/Payson’s sedge (Carex paysonis)-hitchcock’s smooth woodrush(Luzula glabrata var. hitchcockii)-Mertens’ rush (Juncus mertensianus)-Parry’s rush (Juncus parryi).