The Serpentine Siskiyous ecoregion consists of highly dissected mountains containing perennial, high gradient streams at an elevation of 1,500 to 4,300 feet (457 to 1,311 m). It is lithogically distinct from the rest of the Klamath Mountains ecoregion. Many plants have difficulty growing in its serpentine soils due to a shortage of calcium and high levels of magnesium, nickel, and chromium. As a result, vegetation is often sparse and composed of specialist species that have evolved to grow in the potentially toxic and nutrient-poor serpentine soils. It supports a mixed conifer forest of Jeffrey pine, tanoak, incense-cedar, Douglas-fir, and montane chaparral composed of manzanita, ceanothus, Idaho fescue, and Lemmon needlegrass. Historic gold, nickel, chromite, copper, and mercury mining have contributed to water quality problems. The region covers 440 square miles (1,140 km2) in Oregon, including portions of the Rogue River – Siskiyou National Forest and the Kalmiopsis and Wild Rogue wildernesses. Contiguous areas in California have not been mapped yet.