Bunchgrass Ridge

Ecology and restoration of conifer-invaded meadows:
Research and adaptive management

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Tree encroachment
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Landscape context
Bunchgrass Ridge is a broad, gently sloping plateau in the Cascade Range of western Oregon (photo, at bottom). It lies along the boundary of the older, steeply dissected West Cascades and the younger peaks of the High Cascades (map, at right). Elevations range from 1220 to 1375 m (4000 to 4500 ft) and slopes are gentle (<5%), facing primarily southwest. Climate is maritime, with warm dry summers and cool wet winters. Most precipitation falls during winter, with >1000 cm of snowfall. Snowpacks can exceed 2 m and persist into late May.

Tree encroachment. Recent encroachment of conifers into meadows has been dramatic (see photo-sequence, at right). For much of the 20th century, the study area supported a mix of forest and meadow, but many open areas have since been filled by trees. (See our research on the patterns and consequences of conifer invasion at Bunchgrass Ridge)

Tree encroachment
Recent  invasion by lodgepole pine
Recent encroachment
Pinus snags in Abies forest
Older encroachment
Vegetation. The plateau supports a mosaic of dry meadows, areas of recent encroachment (<90 yr), and older forests (>100-200 yr) of lodgepole pine (Pinus contorta) and grand fir (Abies grandis). Forest understory species are typical of rich, mesic sites (e.g., Smilacina stellata, Achlys triphylla, Galium oreganum, and Anemone oregana). Meadows are dominated by graminoids (e.g., Festuca idahoensis, Bromus carinatus, and Carex pensylvanica [now C. inops]) and a diversity of forbs. Plant species list (PDF).

Glacial history. During the Pleistocene, glaciers carved valleys to the north and south of Bunchgrass Ridge and scoured the summit, leaving the current raised plateau. Lateral moraines (PDF) flank the ridge on the north and south, and pothole lakes (Kuitan and Robinson) lie to the east.

Soils. Soil pits dug in meadows and forest of varying ages (photo, below) suggest the presence of grassland vegetation for centuries (perhaps millennia). Soils are deep (>170 cm), fine to very-fine-sandy loams derived from andesitic basalt and deposits of tephra with variable amounts of glacially derived cobbles, stones, and boulders. Soil profiles (PDF).

Disturbance history. Fires occur infrequently (>100 yr) at this elevation in the Cascades. Native Americans used fire to maintain open habitats throughout the Northwest, but stumps within the experimental plots do not show evidence of fire, and archeological surveys have not produced artifacts indicative of human use of the meadow prior to Euro-American settlement.

Describing a soil profine
Lammers & Dyrness
Ted Dyrness (top, deceased) and Duane Lammers (in pit) describe the soil profile in a conifer-invaded meadow (2004).
Grazing by sheep is likely to have occurred during the early part of the 20th century, when grazing in the Cascades was widespread (Miller 1994). However, the local history of grazing at Bunchgrass Ridge is not recorded in Forest Service archives.

Special Habitat Area designation. Bunchgrass Ridge was designated as a Special Habitat Area for wildlife in the Willamette National Forest Land and Resource Management Plan (1990). During the Upper McKenzie Watershed Analysis (1995, update 2006), Bunchgrass was targeted as a high priority for restoration with these objectives:
  • Improve wildlife use by enhancing forage quality and abundance
  • Reduce excessive fuel loadings
  • Maintain/restore grass- and forb-dominated communities and associated ecological processes
  • Protect/preserve historic and prehistoric heritage resources
Bunchgrass Ridge (white rectangle) in the western Cascades landscape, viewed from the south.
Bunchgrass Ridge from the south

Tree encroachment at Bunchgrass Ridge
Trees dominating the forest-meadow mosaic in 1946 had established in the 1800s. Clearcuts adjacent to the study area are evident in the 2000 photo.