Northern Rocky Mountain Refugium Headwater Forested Streams
Provisional State Rank
(see reason below)
State Rank Reason
This aquatic ecological system and the adjacent landscape contains more globally rare and endemic aquatic and terrestrial invertebrates than any other ecological system in the state.
This ecological system classified within the Pacific-influenced Clearwater or Northern Rocky Mountain Refugium is found in the moderate-high elevation (1600-2500m), steep-forested hillslopes of the Bitterroot Mountains. These small, high-gradient streams near their headwaters sources are moderately-confined, single-thread channel streams (1st order spring rivulets, average wetted width-0.5m, average summer temperature: <12oC),and have permanent flow with strong seasonal variability depending on melting snow pack. These systems are often within National Forest Service boundaries and represent groundwater-based streams contributing year-round flow to headwater foothills and mountain streams. The geomorphology of these streams is usually Rosgen A-2 with a step-pool configuration and substrate ranging from boulder/cobbles to gravel in the short pools. Large woody debris from the surrounding hillslopes can provide significant channel material and additional substrate to these streams.
The typical Northern Rocky Mountain Refugium headwater source stream is steep, shallow and fishless with significant barriers to fish colonization; dominant bioloigical communities are amphibians and macroinvertebrates. The macroinvertebrate community consists of coldwater stenotherms of the shredder and predator functional groups (Pristine Mountain Stream #58 assemblage), including disjunct populations and rare endemics: Caudatella edmundsi, Caurinella idahoensis, Soliperla salish, Sericostriata surdickae, Eocosmoecus schmidi, Soyedina potteri, and Secubelmis (Lumbriculidae). Surrounding forest communities are dominated by western red cedar and dense deciduous riparian brush including false huckleberry and devil's club. Large amounts of moss or large woody debris covers the stream channel in most areas. The Rocky Mountain tailed frog and Idaho giant salmander are long-lived amphibian indicator species for this ecological system. Adults inhabit the moss-covered or vertically oriented cobble and boulders in areas wet from the splash zone or seeping water, and the larvae occur within the step pools or runs.
This ecological system classified within the Pacific-influenced Clearwater or Northern Rocky Mountain Refugium is found in the moderate-high elevation (1600-2500m), steep-forested hillslopes of the Bitterroot Mountains on the boundary between Montana and Idaho, geographically bounded by Lolo Pass to the south and Lookout Pass or a little further north.
Due to the confined valley nature of these streams, the largest management issue involves keeping the riparian zone intact. Disturbances in the riparian zone (e.g., timber harvest) can have severe water quality impacts from bank erosion, sedimentation, increased stream temperatures, silt deposits and loss of large woody debris. Livestock use around the riparian areas can have strong local effects resulting in sedimentation and stream widening at cattle crossings.