The 87 ha Sister Rocks RNA, located in Skamania County, Washington, occupies a broad, north-trending ridge top. The topography of the area is generally gentle to moderate, except along the lower margins where steeper slopes occur. Elevations range from 1,100 to 1,280 m. The major plant communities in the natural area are Pacific silver fir (Abies amabilis)/Alaska huckleberry (Vaccinium alaskaense) and Pacific silver fir/rosy twistedstalk (Streptopus roseus) community. Pacific silver fir, often found in pure stands, dominates the entire tract, with western hemlock (Tsuga heterophylla) as the common associate. Douglas fir (Pseudotsuga menziesii), which is rare at higher elevations, becomes occasional to common in some lower slope stands. Noble fir (Abies procera) is also present, although snags and stumps suggest that the species was once more common, and a young stand of noble fir, mountain hemlock (Tsuga mertensiana) and lodgepole pine (Pinus contorta) occurs with Pacific silver fir at the southern edge of the area. Pacific sliver fir is the climax species throughout the area. Douglas fir and noble fir occur only as large, old specimens, and western hemlock, generally a very tolerant species, is also failing to reproduce in significant numbers. Road construction has caused, and will continue to cause, disturbances along the edges of the natural area. However, most of the area is free of human disturbance. A trail runs through the RNA.

Township/Range/Section:

Portions of secs 2, 3, 10 and 11, T5N, R6E.

Latitude:

45,56N

Longitude:

122,03W

Quad Map:

15' Lookout Mountain (1953) - scale 1:62,500.

Threatened or Endangered Species:

Exotic Species Present:

Plant Communities:

The RNA exemplifies Pacific silver fir stands as they occur on mountain slopes and ridgetops in older volcanic portions of the Cascade Range. There are three major community types: Pacific silver fir/rosy twisted stalk (avalanche fawn-lily phase), Pacific silver fir/Alaska huckleberry, and Pacific silver fir/beargrass.

Aquatic Features Present:

None.

Soils:

Soils are generally podzolic with distinctive A2-B2 sequences.

Other Physical Features:

Past Disturbance History:

Other Comments:

Access by road and trail