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Rocky Mountain Subalpine-Montane Riparian Shrubland

Provisional State Rank: S5

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General Description

This riparian system is a seasonally flooded shrubland found at montane to subalpine elevations of the Rocky Mountains. Shrubs dominate this system, with total shrub cover ranging from 20 to 100 percent. It occurs as linear bands of shrub vegetation lining streambanks and alluvial terraces in narrow to wide, low-gradient valley bottoms and floodplains with sinuous stream channels. Flooding creates and destroys sites for the establishment of vegetation through the transport and accumulation of coarse sediment (Melanson and Butler, 1991). Sediment accumlating in these systems can form gravel bars at or near the surface of the river, creating bands of mixed vegetation that occupy different stages of succession (Melanson and Butler, 1991). Ground water seepage from snowmelt may create shallow water tables or seeps that vegetation depends on for a portion of the growing season. This system often occurs as a mosaic of multiple communities that are shrub and herb dominated. The structure of vegetative communities in these systems can vary depending on latitude, elevation and climate. In Montana, these systems are dominated by willows, including Drummond’s willow (Salix drummondiana), Bebb’s willow (Salix bebbiana), planeleaf willow (Salix planifolia ssp. planifolia), undergreen willow (Salix commutata), Idaho willow (Salix wolfii), booth willow (Salix boothi) and Geyer’s willow (Salix geyeriana). Typical herbaceous vegetation found in the understory includes beaked sedge (Carex utriculata), bluejoint reedgrass (Calamagrostis canadensis), and northern reedgrass (Calamagrostis stricta). Generally, the upland vegetation surrounding these riparian systems are conifer dominated forests. Shrubland riparian systems are important for bank stabilization, organic inputs to the adjacent stream, shade cover and wildlife habitat values.


Diagnostic Characteristics
Montane, shrubland, riverine, alluvial, broad leaf shrub, short flooding interval (< 5 years), short persistence

Similar Systems

Range
This system is found throughout the Rocky Mountain cordillera from New Mexico north into Montana, and occurs in the isolated island mountain ranges of central and eastern Montana. It is found throughout the western states and provinces of North America; including the Intermountain Basin and Colorado Plateau states.

Ecological System Distribution
Approximately 43 square kilometers are classified as Rocky Mountain Subalpine-Montane Riparian Shrubland in the 2017 Montana Land Cover layers.  Grid on map is based on USGS 7.5 minute quadrangle map boundaries.



Montana Counties of Occurrence
Big Horn, Blaine, Carbon, Cascade, Chouteau, Fergus, Flathead, Gallatin, Golden Valley, Hill, Judith Basin, Lewis and Clark, Liberty, Meagher, Missoula, Park, Phillips, Powell, Stillwater, Sweet Grass, Toole, Wheatland

Spatial Pattern
Linear

Environment

This riparian system is a seasonally flooded shrubland found at montane to subalpine elevations of the Rocky Mountains. In Montana, this system typically occurs at elevations between 1,750 and 2,693 meters (5,740-8,830 feet). This system consists of narrow bands of shrub vegetation lining streambanks and alluvial terraces in narrow to wide, low-gradient valley bottoms and floodplains with sinuous stream channels. This system is also typical around seeps, fens, and isolated springs on hillslopes away from valley bottoms. Sediment that accumulates in these systems may create gravel bars at or near the surface of the river where colonizing vegetation creates bands of mixed vegetation that occupy different stages of succession (Melanson and Butler, 1991). Ground water seepage from snowmelt may create shallow water tables or seeps that vegetation depends on for a portion of the growing season.


Vegetation

Plant community composition and structure can vary depending on latitude, elevation and climate. For example, in southwest Montana Drummond’s willow occupies higher elevations while Geyer’s willow and booth willow are found at more intermediate elevations. In the northwest region of Montana, Geyer’s and booth willow are barely present and Drummond’s willow dominates most riparian areas (Hansen et al, 1995). Bebb’s willow, planeleaf willow, undergreen willow and Idaho willow are frequent associates. Barclay’s willow (Salix barclayi), shortfruit willow (Salix brachycarpa) and grayleaf willow (Salix glauca) become common at higher subalpine elevations. Sageleaf willow (Salix candida) is indicative of fens and occurs in association with other willow species to form the shrub-dominated carr layers within riparian areas feeding into or out of fens. Redoiser dogwood (Cornus sericea), shrubby cinquefoil (Dasiphora fruticosa), alder (Alnus spp.), currant (Ribes spp.) and Rocky Mountain maple (Acer glabrum) are common associates. Water birch (Betula occidentalis) or bog birch (Betula nana, glandulosa) may also be present.

Dominant graminoid vegetation in the herbaceous stratum of these shrubland riparian systems includes bluejoint reedgrass, northern reedgrass and Northwest Territory sedge. Common forbs include dwarf fireweed (Chamerion latifolium), field mint (Mentha arvensis), glaucous willowherb (Epilobium glaberrimum), western mountain aster (Symphyotrichum spathulatum), and tiny trumpets (Collomia linearis). Sharptooth angelica (Angelica arguta), starry solomon’s seal (Maianthemum stellatum), sweet-cicely (Osmorhiza species), common cow parsnip (Heracleum maximum), clasp-leaf twisted stalk (Streptopus amplexifolius) and green false hellebore (Veratrum viride) are frequent at higher elevations. Within rich fen-carr shrublands, graminoid and forb species diversity is typically higher than other sites supporting these riparian shrublands.

Flooding in these systems influences vegetative communities by transporting sediments and creating establishment sites for colonization. Many plants in these high-energy systems that experience large disturbances from floods have acquired adaptive traits. Some have flexible, resilient stems and specialized cells to hold oxygen so that they can survive large flood events. These species also have reproductive adaptations such as water-dispersed seeds and are able to sprout quickly from flood damaged stumps. Ground water seepage from snowmelt may create shallow water tables or seeps that vegetation depends on for a portion of the growing season. Sites that are over-browsed will become dominated by Bebb willow, a shrub that is more resilient to heavy grazing. In sites where there is prolonged disturbance, willow coverage will decrease, resulting in a more open canopy. Herbaceous vegetation will transition to a grass-dominated system including fowl bluegrass (Poa palustris), Kentucky bluegrass (Poa pratensis) and field horsetail (Equisetum arvense) (Hansen et al, 1995).


National Vegetation Classification Switch to Full NVC View

Adapted from US National Vegetation Classification

A1003 Salix commutata Wet Shrubland Alliance
CEGL003497 Salix commutata - Mesic Graminoid Wet Shrubland
A2658 Elymus repens Ruderal Grassland Alliance
CEGL005868 Elymus repens Ruderal Grassland
A3434 Betula nana Alkaline Shrub Fen Alliance
CEGL001188 Salix candida - Carex utriculata Shrub Fen
A3769 Salix boothii - Salix geyeriana - Salix lutea Montane Wet Shrubland Alliance
CEGL001173 Salix bebbiana Wet Shrubland
CEGL001174 Salix bebbiana - Mesic Graminoids Wet Shrubland
CEGL001175 Salix boothii - Calamagrostis canadensis Wet Shrubland
CEGL001178 Salix boothii - Carex utriculata Wet Shrubland
CEGL001180 Salix boothii - Mesic Forbs Wet Shrubland
CEGL001181 Salix boothii - Mesic Graminoids Wet Shrubland
CEGL001190 Salix drummondiana Wet Shrubland [Placeholder]
CEGL001192 Salix drummondiana - Mesic Forbs Wet Shrubland
CEGL001205 Salix geyeriana - Calamagrostis canadensis Wet Shrubland
CEGL001206 Salix geyeriana - Carex aquatilis Wet Shrubland
CEGL001207 Salix geyeriana - Carex utriculata Wet Shrubland
CEGL001208 Salix geyeriana - Deschampsia caespitosa Wet Shrubland
CEGL001215 Salix lucida ssp. caudata Wet Shrubland
CEGL001219 Salix lutea - Calamagrostis canadensis Wet Shrubland
CEGL001220 Salix lutea - Carex utriculata Wet Shrubland
CEGL002621 Salix lucida ssp. caudata - Rosa woodsii Wet Shrubland
CEGL002624 Salix lutea - Rosa woodsii Wet Shrubland
CEGL002631 Salix drummondiana - Carex utriculata Wet Shrubland
CEGL002666 Salix geyeriana - Mesic Forbs Wet Shrubland
CEGL002667 Salix drummondiana - Calamagrostis canadensis Wet Shrubland
A3770 Salix wolfii - Salix brachycarpa - Betula glandulosa Wet Shrubland Alliance
CEGL001225 Salix planifolia - Calamagrostis canadensis Wet Shrubland
CEGL001227 Salix planifolia - Carex aquatilis Wet Shrubland
CEGL001229 Salix planifolia - Carex scopulorum Wet Shrubland
CEGL001234 Salix wolfii - Carex aquatilis Wet Shrubland
CEGL001238 Salix wolfii - Deschampsia caespitosa Wet Shrubland
CEGL001244 Salix brachycarpa - Carex aquatilis Wet Shrubland
A3771 Alnus incana - Alnus viridis Wet Shrubland Alliance
CEGL001141 Alnus incana Wet Shrubland
CEGL001142 Alnus incana - Betula occidentalis Wet Shrubland
CEGL001143 Alnus incana - Calamagrostis canadensis Wet Shrubland
CEGL001144 Alnus incana - Carex (aquatilis, lenticularis, luzulina, pellita) Wet Shrubland
CEGL001145 Alnus incana - Cornus sericea Wet Shrubland
CEGL001147 Alnus incana - Mesic Forbs Wet Shrubland
CEGL001156 Alnus viridis ssp. sinuata - Athyrium filix-femina / Cinna latifolia Wet Shrubland
CEGL002628 Alnus incana - Athyrium filix-femina Wet Shrubland
CEGL002629 Alnus incana - Lysichiton americanus Wet Shrubland
A3772 Betula occidentalis Wet Shrubland Alliance
CEGL001080 Betula occidentalis Wet Shrubland
CEGL001083 Betula occidentalis - Dasiphora fruticosa ssp. Floribunda Wet Shrubland
CEGL001161 Betula occidentalis - Cornus sericea Wet Shrubland
A3773 Cornus sericea - Dasiphora fruticosa ssp. floribunda - Ribes spp. Wet Shrubland Alliance
CEGL001107 Dasiphora fruticosa ssp. floribunda - Deschampsia caespitosa Wet Shrubland
CEGL001165 Cornus sericea Rocky Mountain Wet Shrubland
CEGL001166 Cornus sericea - Galium triflorum Wet Shrubland
A3796 Acer negundo - Fraxinus anomala - Celtis laevigata var. reticulata Riparian Woodland Alliance
A3799 Rhus trilobata - Crataegus rivularis - Forestiera pubescens Shrubland Alliance
A3833 Alnus viridis ssp. sinuata - Alnus viridis ssp. fruticosa - Acer circinatum Shrub Swamp Alliance
CEGL001154 Alnus viridis ssp. Sinuata Shrub Swamp
A3968 Abies lasiocarpa - Populus tremuloides / Acer glabrum Central Rocky Mountain Avalanche Chute Shrubland Alliance
CEGL001062 Acer glabrum Drainage Bottom Wet Shrubland
*Disclaimer: Alliances and Associations have not yet been finalized in the National Vegetation Classification (NVC) standard.  A complete version of the NVC for Montana can be found here.

Dynamic Processes

Stochastic flood events and variable fluvial conditions are crucial to the development of establishment sites for riparian plants, and act as a primary control on plant succession. Steep gradients and high-energy flows controlled by precipitation cause flooding events that transport coarse sediments. Scouring out and accumulation of sediments constantly creates and destroys sites for the establishment of vegetation (Melanson and Butler, 1991). Accumulating sediments often create gravel bars at or near the surface of the water where colonizing vegetation creates bands of mixed vegetation occupying different stages of succession (Melanson and Butler, 1991). Ground water seepage from snowmelt may create shallow water tables or seeps that vegetation depends on for a portion of the growing season when stream flow is low.


Management

Grazing along narrow low order streams results in increased erosion and channel downcutting (Mitsch and Gosellink, 2000). Sites that are over-browsed will become dominated by Bebb's willow, a shrub that is more resilient to heavy grazing. In sites where there is prolonged disturbance, willow coverage will decrease, and herbaceous vegetation will transition to a grass dominated system including fowl bluegrass, Kentucky bluegrass and field horsetail. In addition, fire suppression, timber harvest and reduced flood frequency can affect the succession of riparian communities.


Restoration Considerations

Restoration strategies will vary based on the degree and type of disturbance event. Restoration efforts must first concentrate on restoring the stream's hydrology, so the 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 grazing from this ecological system 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. However, rhizomatous, highly adaptable exotic grasses such as Kentucky bluegrass, common timothy and smooth brome, and pasture forbs such as clovers (Trifolium species) 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 decide if the exotic density is sufficiently small that an adequate stand of native graminoids and forbs can become established on the site if reseeding efforts are used. In all cases, grazing by cattle and wildlife should 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 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 shrubs and the seed bank.


Species Associated with this Ecological System
  • Details on Creation and Suggested Uses and Limitations
    How Associations Were Made
    We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
    Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.  In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.  However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.  The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.  If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.

    Suggested Uses and Limitations
    Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.  These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.  Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.  Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.  Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).  Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.

    Literature Cited
    • Adams, R.A.  2003.  Bats of the Rocky Mountain West; natural history, ecology, and conservation.  Boulder, CO: University Press of Colorado.  289 p.
    • Dobkin, D. S.  1992.  Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34.  Missoula, MT.
    • Foresman, K.R.  2012.  Mammals of Montana.  Second edition.  Mountain Press Publishing, Missoula, Montana.  429 pp.
    • Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998.  Montana atlas of terrestrial vertebrates.  Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT.  1302 p.
    • Hutto, R.L. and J.S. Young.  1999.  Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32.  72 p.
    • Maxell, B.A.  2000.  Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species.  Report to U.S. Forest Service Region 1.  Missoula, MT: Wildlife Biology Program, University of Montana.  161 p.
    • Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath.  2004.  Amphibians and reptiles of Montana.  Missoula, MT: Mountain Press Publishing Company. 262 p.

Original Concept Authors
Natureserve Western Ecology Group

Montana Version Authors
C. McIntyre, L.K. Vance, T. Luna,

Version Date
1/1/2017

References
  • Classification and Map Identifiers

    Cowardin Wetland Classification:
    System Palustrine
    Class Scrub Shrub
    Water Regime Temporarily to seasonally flooded
    Geographically Isolated Wetland No


    NatureServe Identifiers:
    Element Global ID 28667
    System Code CES306.832, Rocky Mountain Subalpine-Montane Riparian Shrubland

    ReGAP:
    9187: Rocky Mountain Subalpine-Montane Riparian Shrubland


  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Ellis, Janet H., and Jim Richards. 2003. A planning guide for protecting Montana's wetlands and riparian areas. Bozeman, MT: Montana Watercourse.

    • Cowardin, L.M., et al. 1979. Classification of wetlands and deepwater habitats of the United States. U.S. Fish and Wildlife Service, FWS/OBS-79/31. 103pp.
    • Hansen, P. L., R. D. Pfister, K. Boggs, B. J. Cook, J. Joy, and D. K. Hinckley. 1995. Classification and management of Montana's riparian and wetland sites. Montana Forest and Conservation Experiment Station, School of Forestry, University of Montana, Miscellaneous Publication No. 54. 646 pp. + posters.
    • Malanson, George P., and David R. Butler. 1990. "Woody Debris, Sediment, and Riparian Vegetation of a Subalpine River, Montana, U.S.A.". Arctic and Alpine Research. 22 (2): 183-194.
    • Malanson, George P., and David R. Butler. 1991. "Floristic Variation among Gravel Bars in a Subalpine River, Montana, U.S.A.". Arctic and Alpine Research. 23 (3): 273-278.
    • Mitsch WJ, Gosselink JG. 2000. Riparian Ecosystems. In: Wetlands. 3rd Edition. John Wiley and Sons, Inc. 920 p.

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Citation for data on this website:
Rocky Mountain Subalpine-Montane Riparian Shrubland.  Montana Field Guide.  Retrieved on , from