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Siskiyou Wild Rivers: Botanical Diversity

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Vollmer’s lily

Rare plants, ancient trees and brilliant wildflowers: the Siskiyou Wild Rivers area is a national botanical treasure. However, the astounding botanical diversity of the Siskiyou Wild Rivers area of Southwest Oregon went largely unnoticed until 1960, when ecologist Robert Whittaker published his classic study: Vegetation of the Siskiyou Mountains, Oregon and California. Whittaker compared the botanical diversity of the Siskiyou Wild Rivers area to the southern Appalachian Mountains, crediting the region as having “central significance” for the floristic origins and diversity of Pacific Northwest flora. 

The Siskiyou Wild Rivers area is home to thousands of species of plants, including hundreds of species that live nowhere else on earth, leading the World Conservation Union to designate the region as an Area of Global Botanical Significance.

The reasons for this level of botanical diversity say a lot about the nature of the Siskiyou Wild Rivers area. This wild, rugged region is known for its steep terrain, east-west ridgelines, complex geology and numerous microclimates. In addition, over the past 200 million years, the Siskiyou Wild Rivers area hasn’t experienced the volcanic eruptions and glacial events that have shaped other areas in the western United States. The absence of these two factors has created an area that is both a refuge for ancient plant species and a rich source of new plant species. As a result, the Siskiyou National Forest area has the distinction of being the most floristically diverse National Forest in the country.

Howell’s mariposa-lily
Howell’s mariposa-lily

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Adopt a Botanical Area

The Adopt a Botanical Area program is a community watchdog program designed to mobilize volunteers to be KS Wild’s eyes an ears on the ground in designated Botanical Areas throughout the Klamath-Siskiyou region.


Much of the diversity also results from plant species adapting to life in harsh soils derived from peridotite and serpentinite rocks rich in heavy metals such as magnesium, iron, chromium and nickel. In high amounts, these metals are toxic to most plants.

In a nitrogen-limited environment such as the serpentine, plants have adapted their own means of obtaining this vital nutrient, including carnivory. The California pitcher plant or Cobra Lily, Darlingtonia californica, is a rare carnivorous plant of serpentine wetland communities. California pitcher plant obtains nitrogen by decomposing insects captured in the pitcher-shaped leaves. The insects crawl down inside the pitcher where they are trapped by a barrier of downward facing hairs. The Darlingtonia secrets a proteolytic enzyme that breaks down and digests the captured insects.

Awareness of this very special area has grown since Robert Whittaker published his study in 1960, but there are still surprisingly few protections in place to preserve this national treasure for future generations. The rare plants of the Siskiyou Wild Rivers area face ongoing threats from a variety of sources. Mining interests continue to press for the opportunity to remove minerals such as nickel and gold from serpentine areas, which could devastate these fragile plant communities.

“I think this is probably the most important, the most biologically significant, unprotected landscape in the American West”
Bruce Babbitt, Former Secretary of the Interior, 2001
Gentner’s fritillaria

The diversity of the region’s flora is arguably its most distinguishing characteristic. Diversity factors at a local scale include the variability of serpentine soil chemistry, particularly with respect to the ratio of calcium to magnesium, slope, aspect, frequency of disturbance such as fire, and the richness of the flora in the surrounding area. Age of exposure, geographic and reproductive isolation, regional species richness, high rainfall, topographic diversity, distinctive (and exclusionary) soils, and natural selection combine to give us the diversity and endemism of the Klamath-Siskiyou serpentines.

Calypso Orchid
AN AREA AT RISK:

Awareness of this very special area has grown since Robert Whittaker published his study in 1960, but there are still surprisingly few protections in place to preserve this national treasure for future generations of outdoor enthusiasts. The rare plants of the Siskiyou Wild Rivers area face ongoing threats from a variety of sources. Mining interests continue to press for the opportunity to remove minerals like nickel and gold from serpentine areas, which will devastate these fragile plant communities. Off-road vehicles also pose a threat to the area – tearing up sensitive habitat and spreading Port Orford cedar disease, which is threatening the very existence of one of the most beautiful, iconic trees of the region.


SISKIYOU WILD RIVERS AREA BOTANICAL FACTS

  • The Siskiyou Wild Rivers area is home to approximately 1,400 species of plants, including:
    • 400 sensitive or endangered species
    • Approximately 100 endemic plant species
    • 28 species of conifers
  • The watersheds of the West Fork Illinois River and Rough and Ready Creek contain the highest concentration of rare plants in the state of Oregon.

Kalmiopsis leachiana

Kalmiopsis leachiana, a plant discovered in 1930 by Lilla Leech in the Gold Basin area, is a relic of the pre-ice age and the oldest known member of the Heath (Ericaceae) Family. The Kalmiopsis Wilderness was named after this unique endemic shrub.