These forests are similar to Rocky Mountain Subalpine Dry-Mesic Spruce-Fir Forest and Woodland (4242), but occur in locations with cold-air drainage or ponding, or where snowpacks linger late into the summer, such as north-facing slopes and high-elevation ravines. They are distinguished by their occurrence on mesic to wet microsites within the matrix of the drier (and warmer) subalpine spruce-fir or lodgepole pine forests. The microsites include north-facing slopes, swales or ravines, toeslopes, cold pockets, and other locations where available soil moisture is higher or lasts longer into the growing season. This system can extend down in elevation below the subalpine zone in places where cold-air ponding occurs, especially on north and east aspects. Elevations range from 884 to 1,981 meters (2,900-6,500 feet) west of the Continental Divide, and 1,585 to 2,682 meters (5,200-8,800 feet) east of the Continental Divide. Spruce is usually associated with subalpine fir and occurs either as a climax co-dominant or as a persistent, long-lived seral species in most upper elevation subalpine fir stands. Mountain hemlock (Tsuga mertensiana) occurs as small patches within the matrix of this mesic spruce-fir system, but only in the most maritime of environments of northwestern Montana, in the coldest and wettest sites. The shrub understory contains many ericaceous species such as rusty leaf menziesia (Menziesia ferruginea), dwarf huckleberry (Vaccinium caespitosum), mountain huckleberry (Vaccinium membranaceum), bilberry (Vaccinium myrtillus), grouse whortleberry (Vaccinium scoparium), pink mountain heath (Phyllodoce empetriformis), black twinberry honeysuckle (Lonicera involucrata), gooseberry (Ribesspecies) and thimbleberry (Rubus parviflorus). The herbaceous understory contains mesic forbs, graminoids, and ferns and fern allies on the wettest sites. Moss cover is often high. Stand-replacing fires are less common in mesic spruce-fir forests than in dry-mesic forests.
Forest and woodlands, acidic and udic soils, very long disturbance intervals, long persistence (>500years), Picea engelmannii, Abies lasiocarpa
This system occurs is distinguished by its occurrence on mesic to wet microsites within the matrix of the drier (and warmer) subalpine spruce-fir or lodgepole pine forests. The microsites include north-facing slopes, swales or ravines, toeslopes, cold pockets, and other locations where available soil moisture is higher or lasts longer into the growing season. Engelmann spruce and subalpine fir mesic forests comprise a substantial part of the subalpine forests of the northwestern Montana Rocky Mountains. In Montana, these mesic to wet forests are very common west of the Continental Divide in the Flathead and Kootenai river drainages. The wetter habitat types such as subalpine fir/ devil’s club (Abies lasiocarpa/Oplopanax horridum) and Engelmann spruce/ horsetail (Picea engelmannii/Equisetum arvense) associations are found locally in the Flathead Valley and along Sheep Creek north of White Sulphur Springs.
Tree canopy characteristics are relatively uniform, with Picea and Abies dominating either mixed or alone. Engelmann spruce is more tolerant of extreme environmental conditions than subalpine firs, and is usually more dominant in the drier and wettest occurences within this system. Mountain hemlockoccurs as small to large patches within the matrix of this mesic spruce-fir system but only in the most maritime of environments of northwestern Montana, in the coldest and wettest sites.
The understory of Picea -Abies forests in northwestern Montana often supports diverse stands of ericaceous plants, such as rusty leaf menziesia, dwarf huckleberry, mountain huckleberry, bilberry and mountain heath. Grouse whortleberry and Labrador tea (Ledum glandulosum) are common on mesic sites.Cascade azalea (Rhododendron albiflorum) occurs in association with mountain hemlock and subalpine fir in some occurrences in northwestern Montana.Other common shrubs include Rocky Mountain maple (Acer glabrum), serviceberry (Amelanchier alnifolia), black twinberry honeysuckle, currant (Ribes species), thimbleberry, shortfruit willow (Salix brachycarpa) and greyleaf willow (Salix glauca). In the wettest subalpine fir forests in northwestern Montana, devil’s club is a major shrub associate. These sites are usually restricted to ravine bottoms near streams and seeps where the water table remains near the surface all year. The herbaceous layer is typically diverse. Smooth woodrush (Luzula glabrata var. hitchcockii), bluejoint reedgrass (Calamagrostis canadensis), and pinegrass (Calamagrostis rubescens) are the most commonly associated graminoids. On moist sites with seeps or adjacent to running water, a lush herbaceous understory is present. Forb species includebaneberry (Actaea rubra), marsh marigold (Caltha leptosepala), queen’s cup beadlily (Clintonia uniflora), bunchberry dogwood (Cornus canadensis),starry Solomon’s seal (Maianthemum stellatum), sidebellswintergreeen (Orthothilla secunda), arrowleaf groundsel (Senecio triangularis), clasp-leaf twisted stalk (Streptopus amplexifolius), foamflower (Tiarella trifoliata), western meadow rue (Thalictrum occidentale), Sitka valerian (Valeriana sitchensis), green false hellebore (Veratrum viride), and beargrass (Xerophyllum tenax). Ferns and fern allies such ashorsetail (Equisetum species), oakfern (Gymnocarpium dryopteris) and ladyfern (Athyrium species) form dense cover, inespecially wet spruce habitats on flat sites with poor drainage. Moss cover is often high within these forests.
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