. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Forest Composition For community descriptions within the Mixed-Evergreen Zone, we are almost entirely dependent upon Whittaker (1960); we will use his description of vegetation growing on diorite, with average moisture conditions as modal for the zone. The upper canopy level is dominated by Pseudotsuga menziesii, al- though Pinus lambertiana is frequently pres- ent. The lower tree canopy of sclerophyllous trees is dominated by Lithocarpus densiflorus, associated with Quercus chrysolepis, Arbutus me
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Forest Composition For community descriptions within the Mixed-Evergreen Zone, we are almost entirely dependent upon Whittaker (1960); we will use his description of vegetation growing on diorite, with average moisture conditions as modal for the zone. The upper canopy level is dominated by Pseudotsuga menziesii, al- though Pinus lambertiana is frequently pres- ent. The lower tree canopy of sclerophyllous trees is dominated by Lithocarpus densiflorus, associated with Quercus chrysolepis, Arbutus menziesii, and Castanopsis chrysophylla. The shrub layer averages about 30-percent cover- age and is "typically composed of Quercus chrysolepis, Berberis nervosa, B. pumila, Rubus ursinus, Rosa gymnocarpa, Rhus diver- siloba, and Gaultheria shallon. The herba- ceous layer is not well developed ( coverage) but includes Whipplea modesta, Achlys triphylla, Trientalis latifolia, Goody era oblongifolia, Pteridium aquilinum, Apocynum pumilum, Disporum hookeri, Lonicera hispi- dula, Festuca occidentalis, and Melica har- fordii. Whittaker (1960) described a Chamaecy- paris lawsoniana-Pseudotsuga menziesii forest on more mesic sites in which these species are dominants. Small sclerophyllous trees are present but not dominant. Taxus brevifolia, Acer circinatum, Corylus cornuta var. califor- nica, and Cornus nuttallii are typical under- story species along with Gaultheria shallon, Berberis nervosa, Rubus ursinus, Linnaea bo- realis, Polystichum munitum, and Achlys tri- phylla. Whittaker (1960) refers to communities on more xeric dioritic sites as "Sclerophyll- Pseudotsuga" as they are characterized by an overgrowth (with less than 50-percent cover- age) of Pseudotsuga menziesii and a closed canopy of sclerophylls. Lithocarpus densiflor- us is characteristically the dominant sclero- phyll, but Arbutus menziesii and Quercus chrysolepis are also abundant. Typical shru
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