Horse Rock Ridge RNA

Horse Rock Ridge Research Natural Area (RNA) was established to represent a grassy “bald” (treeless area) on the western margin of the Cascade Range and its associated botanical, wildlife, and scenic values. It lies east of the Willamette Valley and is part of the western slope of the Cascade Range physiographic province. Approximately two-thirds of the RNA has a southern exposure, and the rest of the area lies on a north slope. The topography is rugged with rock outcroppings and steep slopes. The RNA consists of a mosaic of open grasslands with young and old-growth forests. The forest is dominated by Douglas fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla). Hairy manzanita (Arctostaphylos columbiana), poison oak (Toxicodendron diversilobum), oceanspray (Holodiscus discolor), and serviceberry (Amelanchier alnifolia) dominate the transition between forest and grassland. The grass bald includes several seeps where most of the species diversity is located. The blue wildrye (Elymus glaucus) association dominates the grassland while Idaho fescue (Festuca idahoensis), lemon’s needlegrass (Stipa lemmonii)/racomitrium moss (Racomitrium canescens), naked buckwheat (Eriogonum nudum), Ross’ sedge (Carex rossii), seep monkeyflower (Mimulus guttatus), and Kellogg's dwarf rush (Juncus kelloggii) are also present plant associations.