Pedologists and ecologists generally consider peridotite and serpentinite together as common serpentine soils or substrates. A detailed survey in the Klamath Mountains, CA, with separate soil map units on peridotite and serpentinite revealed appreciable differences in geomorphic and pedologie features between these types of ultramafic rocks. Slopes tend to be steeper on peridotite and the soils redder. More Alfisols (Luvisols) were found on peridotite, and more Mollisols (Phaeozems) on serpentinite. Very shallow soils (7% of the area), which are mostly Mollisols and Entisols (Leptosols), are more common on serpentinite. Barrens are commonly fragmental colluvium (talus) on peridotite and erodible, slightly to moderately stony summits and slopes on serpentinite. The most obvious vegetation differences related to parent material are on very shallow and shallow soils, with more coniferous trees (Pinus jeffreyi [Jeffrey Pine] > Calocedrus decurrens [Incense Cedar] > Pseudotsuga menziesii [Douglas Fir]) and Quercus durata (Leather Oak) on peridotite, and more Ceanothus cuneatus (Buckbrush) and Vulpia microstachys (Annual Fescue) on serpentinite soils.