Wikipedia
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:
- low calcium-to-magnesium ratio
- lack of essential nutrients such as nitrogen, potassium, and phosphorus
- high concentrations of nickel and chromium (more common in ultramafic rocks).
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.