Sturgeon River Gorge Research Natural Area

[photo:] Mixed conifer-hardwood stand near Sturgeon River Gorge RNA on the Ottawa National Forest.  Photo by Ramona Shackleford, USDA Forest Service.

Houghton and Baraga
The primary features of the Sturgeon River Gorge RNA are the large virgin stand of mature eastern hemlock and the oxbow lake. The RNA includes a cross-section of the gorge from river to rim, and includes transverse ridges, terraces and an abandoned oxbow basin. There are a variety of plant communities present that represent seral to mature types, including the following cover types: balsam fir-aspen/paper birch; hemlock; paper birch; quaking aspen; sugar maple-beech/yellow birch; and open (oxbow lake).
The RNA is within the Sturgeon River Gorge Wilderness Area and the Sturgeon River is designated as a Wild River.

Ecological Information

Physical and Climatic Conditions

Nearest weather station, with distance and direction from RNA:
The Alberta weather station is 9 miles east of the RNA.
Annual precipitation (type, seasonal distribution) :
Annual precipitation averages 34 inches (86 cm), 62% of which falls between April and September. Average seasonal snowfall is 155 inches (394 cm).
Maximum and minimum temperatures:
Daily summertime temperatures average 60° F, and daily maximum temperatures average 51° F. Average temperature in the winter is 28° F, and daily minimum temperatures average 40° F.
Elevations range from 981 feet (299 m) on the Sturgeon River to 1270 feet (387 m) MSL at the highest point, in the northwest corner of the RNA. The oxbow lake is at 984 feet (300 m).
Geology and Soils:
Tills of considerable depth, at least to the depth of the gorge, were deposited in this area. The Portage Lake Moraine crosses the gorge at about the RNA. The moraine became a shoreline of proglacial Lake Duluth, which formerly inundated the RNA. The gorge was formed when the lake breached the moraine and drained through the gorge with the water flowing southward toward Lake Algonquin. The subsequent northward retreat of the shoreline toward the Lake Superior basin and the isostatic rebound of the area caused the drainage to reverse and flow northward. Several landforms in the RNA were shaped in these later stages. The terrace appears to have been an oxbow that drained and filled after continuous downcutting left it perched above the river level. The small ridge appears to be a terrace escarpment that formed at an earlier, higher river stage also.
Aquatic Features:
No mapped rivers or streams are within the RNA.  The Sturgeon River forms part of the south and the east boundary of the RNA. The only lake in the RNA is the unnamed 5 acre (2 ha) oxbow lake.

Ecological Classification & Inventory

Southern Superior Uplands (212J)
Keweenaw Coarse Till and Lake Plain (212Sn)
Landtype Association:
Sturgeon River Gorge (JN07)
Plant Communities:
FS Cover Type Acres HA Initial National Vegetation Classification Associations (NVCA)
Balsam fir/ aspen/ paper birch 4 2 CEGL002475 Picea glauca-Abies balsamea-Populus tremuloides/Mixed Herbs Forest or
CEGL002446 Picea glauca-Abies balsamea/Acer spicatum/Rubus pubescens Forest  or
CEGL002474 Abies balsamea-Betula papyrifera/Diervilla lonicera Forest
Hemlock 122 49 CEGL002598 Tsuga canadensis-(Betula alleghaniensis) Forest  or
CEGL005044 Tsuga canadensis-Acer saccharum-Betula alleghaniensis Forest
Paper birch 107 43 CEGL002467 Populus tremuloides-Betula papyrifera-(Acer rubrum, Populus grandidentata) Forest or
CEGL002468 Populus tremuloides-Betula papyrifera/Acer saccharum- Mixed Hardwoods Forest or
CEGL006303 Populus (tremuloides, grandidentata)-Betula (populifolia, papyrifera) Woodland
Quaking aspen 17 7 CEGL002467 Populus tremuloides-Betula papyrifera-(Acer rubrum, Populus grandidentata) Forest or
CEGL002468 Populus tremuloides-Betula papyrifera/Acer saccharum-Mixed Hardwoods Forest or
CEGL006303 Populus (tremuloides, grandidentata)-Betula (populifolia, papyrifera) Woodland
Sugar maple /beech /yellow birch 94 38 CEGL002457 Acer saccharum-Betula alleghaniensis-(Tilia americana) Forest or
CEGL002458 Acer saccharum-Tilia americana/Ostrya virginiana/Lonicera canadensis Forest
Open (oxbow lake) 5 2 NA:  plant communities within the lake have not been mapped
Total 351 142  

View Complete Plant List

Common Shrub Species:
Mountain maple (Acer spicatum), Bunchberry dogwood (Cornus canadensis), American fly honeysuckle (Lonicera canadensis),
Common Herbaceous Species:
Wild sarsaparilla (Aralia nudicaulis), Obscure (rare) clubmoss (Lycopodium obscurum), Bearded shorthusk (Brachyelytrum erectrum), Canada mayflower (Maianthemum canadense), Bluebead (Clintonia borealis), Partridgeberry (Mitchella repens), Threeleaf goldthread (Coptis trifolia), Roughleaf ricegrass (Oryzopsis asperifolia), Interrupted Fern (Osmunda claytonia), Beaked hazelnut (Corylus cornuta), Mountain woodsorrel (Oxalis montana), Intermediate woodfern (Dryopteris intermedia), Long beechfern (Phegopteris connectilis), Bigleaf aster (Eurybia macrophylla), Dwarf red blackberry (Rubus pubescens), Twistedstalk (Streptopus lanceolatus var.  roseus), Shining clubmoss (Huperzia lucidula), Starflower (Trientalis borealis)
Common Fauna:
Fauna typical of mesic northern forest and riverine communities is expected in the RNA.

Related Reports and Publications

Metzger, Frederick, S. J. Trull.  2012.  Establishment Record for Sturgeon River Gorge Research Natural Area. Unpublished report on file at the Northern Research Station, East Lansing, MI.  49 pages.

Last Modified: August 19, 2021