Serpentine soil

A serpentine soil is derived from ultramafic rocks, in particular serpentinite, a rock formed by the hydration and metamorphic transformation of ultramafic rock from the Earth's mantle. Serpentinite is composed of the mineral serpentine, but the two terms are often both used to mean the rock, not its mineral composition.

The soils derived from ultramafic bedrock give rise to unusual and sparse associations of edaphic (and often endemic) plants that are tolerant of extreme soil conditions, including:

The atmosphere is the source of nitrogen, mainly by microbial fixation, in practically all soils. Soils derived from any parent material, including serpentinite, differ greatly in the amounts of plant-available nitrogen in them. Nitrogen spans practically the same range of concentrations in serpentine soils as in most other kinds of soils. The low Ca:Mg ratios is the main plant limiting factor in serpentine soils.

Plants that grow only in serpentine soils are commonly called serpentine endemics.

Excellent examples of serpentine soils and the distinctive ecologic communities associated with them have been described in western North America.

For instance, in areas where these ultramafic rocks are patchy, such as the Klamath Mountains of northern California and southwest Oregon, the areas of serpentine soil can be clearly seen as sparsely covered areas or open forest bounded by closed forest on the non-ultramafic soils.

Areas of serpentine soil are also home to diverse wildflowers, many of which are rare or endangered species such as Acanthomintha duttonii, Pentachaeta bellidiflora, and Phlox hirsuta. In California, shrubs such as leather oak (Quercus durata) and coast whiteleaf manzanita (Arctostaphylos viscida ssp. pulchella) are typical of serpentine soils.

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