Montana Field Guide

In northwestern Montana, conifer swamps occur from 865 to 1485 meters (2,838-5,200 feet). This is a minor system with infrequent occurrences on valley bottoms, lower benches, toeslopes, stream terraces, and flat sites, often adjacent to lakes, fens or wet meadows with low gradient, meandering streams. Water tables are typically within 50 centimeters (20 inches) of the soil surface throughout the year, with standing water in surface depressions. These swamps are dominated by conifers growing on poorly drained soils that are saturated year-round or have seasonal flooding in the spring. This system is indicative of poorly drained, mucky areas, and areas are often a mosaic of moving water and stagnant water. Soils can be woody peat, muck or mineral but tend toward mineral. Vegetation includes wetland phases of western red cedar (Thuja plicata), western hemlock (Tsuga heterophylla), subalpine fir (Abies lasiocarpa) and Engelmann spruce (Picea engelmannii) forests. These wetland forests are generally distinguishable from other upland forests and woodlands by shallow water tables and mesic or hydric undergrowth vegetation. Some of the most typical understory species include American ladyfern (Athyrium filix-femina), woodfern (Dryopterisspecies), skunk cabbage (Lysichiton americanus), field horsetail (Equisetum arvense), arrowleaf groundsel (Senecio triangularis), and bluejoint reedgrass (Calamagrostis canadensis). This system frequently borders fens and wet to mesic coniferous forests.

This system is dominated by coniferous trees on poorly drained soils that are saturated year-round or are subjected to seasonal flooding during spring months. These forests are found on flat to gently sloping lowlands, but also occur up to the lower limits of continuous forest. In northwestern Montana, these uncommon wetland forests occur most frequently in depressions on valley bottoms. However, they can occur on steeper slopes where soils are shallow over unfractured bedrock. Soils in these systems are poorly drained and can be organic peat or muck, but are more commonly mineral soils with an A horizon of 10 centimeters (4 inches) or less. Surface horizons usually have high organic matter, and redox depletions are found in moist subsoil. Water tables are typically within 50 centimeters (20 inches) of the soil surface throughout the year, with standing water in surface depressions. Generally, there is both moving and stagnant water within these forests. The system is often seen as an ecotone gradient between fens, wet meadows or marshes and mesic, upland coniferous forests. Some occurrences develop in spring-fed areas adjacent to lakes and ponds, but the system is most often found on benches, toeslopes or valley bottoms along mountain streams. At higher elevations, subalpine fir-bluejoint reedgrass (Abies lasiocarpa- Calamagrostis canadensis) forests are found along sub-irrigated stream terraces, pond margins and wet meadows (Pfister et al 1977).

In conifer dominated swamps, the understory vegetation is characterized by high cover of ferns and fern allies such as American ladyfern (Athyrium filix-femina), woodfern (Dryopteris species), and horsetail (Equisetum species). Common graminoids include bluejoint reedgrass (Calamagrostis canadensis), beaked sedge (Carex utriculata) and softleaf sedge (Carex disperma).

In spruce- (Picea species) dominated swamps in the Flathead Valley, skunk cabbage (Lysichiton americanus) can form a nearly continuous cover in the understory. American ladyfern is often co-dominant on these sites. In other spruce-dominated occurrences, field horsetail (Equisetum arvense) or common horsetail (Equisetum hyemale) and American ladyfern are frequently the dominant species in the understory. Other forbs include arrowleaf groundsel (Senecio triangularis), Brewer’s miterwort (Mitella breweri), five stamen miterwort (Mitella pentandra), bunchberry dogwood (Cornus canadensis), dwarf red blackberry (Rubus pubescens), twisted stalk (Streptopus amplexifolius), and Canada violet (Viola canadensis) (Hansen et al., 1995). Orchids such as one leaf orchid (Ameorchis rotundifolia), sparrow’s egg ladyslipper (Cypripedium passerinum) and small yellow ladyslipper (Cypripedium parviflorum) may occur on hummocks formed around base of trees and shrubs, especially in spruce swamps occurring adjacent to extremely rich fens. The shrub canopy may include thinleaf alder (Alnus incana), water birch (Betula occidentalis), dwarf birch (Betula nana) and redoiser dogwood (Cornus sericea).

In northwestern Montana, swamps of western redcedar (Thuja plicata) and western hemlock (Tsuga occidentalis) are largely confined to toeslopes and valley bottoms below 1,280 meters (4,200 feet). In these swamps, devil’s club (Oplopanax horridum) is the dominant shrub. Pacific yew (Taxus brevifolia) is often present. The herbaceous understory includes American skunk cabbage, American ladyfern, oak fern (Gymnocarpium dryopteris), wild ginger (Asarum caudatum), foam flower (Tiarella trifoliata), starry solomon’s seal (Maianthemum stellatum), and fragrant bedstraw (Galium triflorum).

Subalpine fir (Abies lasiocarpa) swamps are infrequently represented in Montana, but floristically, they are very similar to western red cedar swamps. This minor type occurs in colder areas between 1,188 to 1,324 meters (3,900 to 5,000 feet) in northwestern Montana (Pfister et al., 1977). However, subalpine fir-bluejoint reedgrass systems are common throughout Montana up to the subalpine elevations. Shrub cover is low and is usually represented by alder (Alnus species). Bluejoint reedgrass dominates the understory vegetation. Associated forbs include lanceleaf arnica (Arnica latifolia), Canadian horseweed (Conyza canadensis), Idaho licorice root (Ligusticum tenuifolium), and brook saxifrage (Saxifraga arguta).