. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. cial outwash, and lava flows in the Cas- cade Range of southern Washington and northern Oregon; this community is distinguished by a depauperate un- derstory of Arctostaphylos uva-ursi or A. nevadensis and many species of li- chens and mosses (Kalama River lahar, Gifford Pinchot National Forest, Wash- ington). Figure 154. — Vegetations on serpentine sites and ad- jacent nonserpentine soils often con- trast sharply; in this Siskiyou Mountain area, open Pinus Jeffrey>i stands on ser- pentine (righ
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. cial outwash, and lava flows in the Cas- cade Range of southern Washington and northern Oregon; this community is distinguished by a depauperate un- derstory of Arctostaphylos uva-ursi or A. nevadensis and many species of li- chens and mosses (Kalama River lahar, Gifford Pinchot National Forest, Wash- ington). Figure 154. — Vegetations on serpentine sites and ad- jacent nonserpentine soils often con- trast sharply; in this Siskiyou Mountain area, open Pinus Jeffrey>i stands on ser- pentine (right) contrast with those of Pseudotsuga menziesii, Pinus lamberti- ana, and Libocedrus decurrens on non- serpentine soils (left).. Serpentine Areas Serpentine areas are characterized by unu- sual plant communities and floras. Vegetation is invariably stunted on serpentine sites in comparison with that on adjacent nonserpen- tine soils. Sharp contrasts in physiognomy, composition, and productivity of communi- ties are typical at margins of serpentine out- crops (fig. 154). The floras are unusual includ- ing endemics restricted to serpentine species not usually found in adjacent communities and "bodenvag" species which appear edaph- ically indifferent (Kruckeberg 1954, 1964, 1967; Whittaker 1954b, 1960; Waring 1969). Serpentine areas in this discussion refer to habitats with soils derived from ultramafic rocks either as peridotite and dunite (igneous forms) or as serpentinite (the metamorphic derivative) (Kruckeberg 1967). Such soils are typically low in total and adsorbed calcium and high in magnesium, chromium, and nickel (Walker 1954). Walker (1954) has analyzed the factors affecting plant growth on such sites and concluded the plants growing there must be tolerant of low calcium levels and one or more additional conditions; , high nickel, chromium, or magnesium and physi- cally unfavorable shallow soils. There are three major serpentine areas in the Pacific Nort
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