Montana Field Guide

This riparian woodland system includes seasonally flooded forests and woodlands found at montane to subalpine elevations in the Rocky Mountains. This habitat ranges from narrow streamside forests lining, confined low-order mountain streams to stands along broader, meandering tributaries, but they are typically dominated by coniferous tree species. Stands generally occur at elevations between 4,600 and 8,800 feet. In subalpine environments where there are steep gradients and high-energy flows controlled by precipitation and hydrological events, the transport and accumulation of sediments constantly creates and destroys sites for the establishment of vegetation (Melanson and Butler, 1991). In western Montana, this system is typically dominated by grand fir (Abies grandis), subalpine fir (Abies lasiocarpa), Engelmann spruce (Picea engelmannii), western red cedar (Thuja plicata) and western hemlock (Tsuga heterophylla) in moister sites, and by Douglas-fir (Pseudotsuga menziesi), ponderosa pine (Pinus ponderosa), and Rocky Mountain juniper (Juniperus scopulorum) in drier areas (Ellis and Richard, 2003). The understory in this riparian system is typically sparse, but along the banks and on gravel bars, willow (Salix spp.), alder (Alnus spp.) and redosier dogwood (Cornus sericea) can be found. These riparian conifer types contribute to animal and plant diversity because they tend to have a more diverse forest structure than adjacent upland habitats. Although riparian areas make up a relatively small percent of cover in the Rocky Mountain West, they provide important migratory corridors, foraging areas and shade cover for Montana’s birds, fish, insects and mammals (Ellis and Richard, 2003).

This riparian woodland system includes seasonally flooded forests and woodlands found at montane to subalpine elevations of the Rocky Mountains. Stands typically occur at elevations between 4,600-8,800 feet. This system is common to the poorly-developed floodplains and terraces of V-shaped, narrow valleys and canyons, and less frequently, it occurs in moderate to wide valley bottoms on large floodplains along broad, meandering rivers such as the South Fork of the Flathead, and on pond or lake margins. In subalpine environments where there are steep gradients and high-energy flows controlled by precipitation and hydrological events, the transport and accumulation of sediments constantly creates and destroys sites for the establishment of vegetation (Melanson and Butler, 1991).

Vegetation composition and structure can vary depending on latitude, elevation and climate. A woody riparian area in the subalpine zone of the Rocky Mountains in Montana is typically dominated by grand fir, subalpine fir and Engelmann spruce. Grand fir and Engelmann spruce are considered late seral species, while subalpine fir is predominantly found in climax communities at higher elevations or at lower elevations in frost pockets (Hansen et al., 1995). In the montane zone, dominant vegetation changes to a community dominated by ponderosa pine, western larch (Larix occidentalis) and Douglas fir (Pseudotsuga menziesii). Western red cedar (Thuja plicata) and western hemlock (Tsuga heterophylla) occur in moister sites west of the Continental Divide, and Some sites support Rocky Mountain juniper. The understory is typically sparse, but along the banks and on gravel bars, willow, alder and redosier dogwood can be present. Some sites support scattered black cottonwood (Populus balsamnifera) and/or small stands of quaking aspen (Populus tremuloides). The vegetation in these systems relies on a consistent shallow water table to meet individual plant requirements; however, periodic flooding is necessary for community maintenance. Flooding transports sediments and creates establishment sites for plant colonization. Many plants have acquired adaptive traits as a result of this disturbance regime. Mechanical adaptations such as stem flexibility and specialized oxygen-holding cells assist riparian plants to endure through the physical strains of flooding. Reproductive adaptations, including water-dispersible seeds, vegetative budding, and adventitious roots allow plants to colonize and regenerate by seed and asexual methods.

The understory shrub species often form in a narrow band in the gravel bars and embankments along the stream channel. In the montane zone, species such as thinleaf alder (Alnus incana), redoiser dogwood and willows such as Bebb’s willow (Salix bebbiana), Booth’s willow (Salix boothii), Drummond’s willow (Salix drummondiana), dusky willow (Salix melanopsis), and Geyer’s willow (Salix geyeriana) are common. In western Montana riparian forests dominated by spruce or subalpine fir, devil’s club (Oplopanax horridus) may be a codominate in the understory, but this is an infrequent plant association. Other minor shrubs include thimbleberry (Rubus parviflorus), elderberry (Sambucus species), Douglas hawthorn (Crataegus douglasii), black twinberry (Lonicera involucrata), alder buckthorn (Rhamnus alnifolia), serviceberry (Amelanchier alnifolia), common snowberry (Symphoricarpos albus) and Woods’ rose (Rosa woodsii).

In the subalpine elevations, sitka alder (Alnus viridis) and Drummond’s willow are frequently dominant. Water birch (Betula occidentalis) or resin birch (Betula glandulosa) may also be present. Planeleaf willow (Salix planifolia), undergreen willow (Salix commutata), Barclay’s willow (Salix barclayi), shortfruit willow (Salix brachycarpa) and grayleaf willow (Salix glauca) become common at higher elevations. Herbaceous vegetation forms a minor component of this system but may include small patches of bluejoint reedgrass (Calamagrostis canadensis), drooping woodreed (Cinna latifolia) and sedges such water sedge (Carex aquatilis). Common forbs include arrowleaf groundsel (Senecio triangularis), angelica (Angelica spp.) baneberry (Actaea rubra) western meadow rue (Thalictrum occidentale), starry solomon’s seal (Maianthemum stellatum), fragrant bedstraw (Galium triflorum), Virginia strawberry (Fragaria virginiana), sweet-cicely (Osmorhiza species), common cow parsnip (Heracleum maximum), clasp-leaf twistedstalk (Streptopus amplexifolius) and green false hellebore (Veratrum viride). Common ferns and fern allies are often present, such as horsetail (Equisetum species), American ladyfern (Athryium filix-femina), and oak fern (Gymnocarpium dryopteris).

Grazing along narrow, low order streams can result in increased erosion and channel downcutting (Mitsch and Gosellink, 2000). Sites that are subjected to heavy grazing practices may transition to an herbaceous understory consisting of introduced grasses and forbs such as Kentucky bluegrass (Poa pratensis) and Canadian thistle (Cirsium arvense). In addition, fire suppression, timber harvest and reduced flood frequency can affect the succession of riparian communities.

Restoration strategies are dependent on the degree and type of disturbance event. Restoration efforts must first concentrate on restoring thestream's hydrology, so floods can re-occur. In-stream habitat enhancement (e.g., additions of logs or boulders) should be employed after restoring natural processes or where short-term improvements in habitat are needed (e.g., for species in recovery).

Removing or strictly limiting grazing by livestock and wildlife will allow the system to recover if hydric soils have not been lost due to extensive soil compaction, pugging, or down cutting of stream channels, and if there are existing populations of herbaceous native species (Carex, Juncus, and native grasses) that possess rhizomatous root systems capable of re-colonizing bare soils. Rhizomatous, highly adaptable exotic grasses such as Kentucky bluegrass, common timothy and smooth brome and pasture forbs such as clovers (Trifoliumspecies) and common dandelion (Taraxacum officinale) will persist on the site and may compete with existing populations of native graminiods and forbs. In these cases, land managers must determine whether the exotic density is small enough that an adequate stand of native graminoids and forbs can become established on the site if reseeding efforts are used. In all cases, grazing must be excluded for several years to allow adequate re-growth and recovery of existing shrubs and the herbaceous understory.

Because all major shrub species within this riparian system are capable of re-sprouting and typically possess extensive, spreading root systems, modified land management practices in areas of low to moderate impact can minimize additional restoration needs. Vigor, health and degree of vegetative regeneration of existing trees and shrubs must be evaluated to determine if these components of the community are capable of recovery in an acceptable time frame. Intensive revegetation efforts should be limited to sites where a catastrophic wildfire or prolonged heavy grazing has destroyed existing trees, shrubs and the seed bank.