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Serpentine Geoecology of Western North AmericaGeology, Soils, and Vegetation$
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Earl B. Alexander, Roger G. Coleman, Todd Keeler-Wolfe, and Susan P. Harrison

Print publication date: 2007

Print ISBN-13: 9780195165081

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780195165081.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 13 June 2021

Synthesis and Future Directions

Synthesis and Future Directions

24 Synthesis and Future Directions
Serpentine Geoecology of Western North America

Earl B. Alexander

Roger G. Coleman

Todd Keeler-Wolfe

Susan P. Harrison

Oxford University Press

Ultramafic rocks come from deep within the earth. Most rocks on the surface of the earth are quite different from them. Unique rocks make unique soils and support special plants. Exploring the links and interactions among these unique rocks, soils, and vegetation is an interdisciplinary endeavor that has been accomplished by experts in three areas. It has helped elucidate serpentine rock–soil–plant relationships and provide a rationale for the unusual soil properties and vegetation associated with ultramafic rocks. Examples from arctic tundra to temperate rainforest and hot desert in western North America provide a framework for the investigation of serpentine geoecosystems around the world. The unusual character of most serpentine vegetation is readily apparent even to an untrained eye. Although a vast number of rock and soil types make up the earth’s surface, few have as dramatic and visible effects on ecosystems as do ultramafic, or serpentine materials. Most ultramafic rocks in western North America have been derived from the mantle of earth via ocean crust. Magnesium is highly concentrated in the mantle and calcium, potassium, and phosphorous are relatively low. Calcium and potassium are further depleted from peridotite in the partial melting of ultramafic rock at the base of the ocean crust. As oceanic plates drift from spreading centers, most of the ocean crust is subducted and returns to the mantle (chapter 2). Only relatively small fragments of ocean crust are added to the continents. Because eukaryotic organisms, from protozoa to plants and animals, have evolved on continental crust, they are adapted to soils with higher concentrations of calcium, potassium, and phosphorus (elements with higher concentrations in continental crust than in ultramafic rocks from the base of the ocean crust) and much lower concentrations of magnesium. Having evolved on continents, plants depend on relatively high ratios of calcium and potassium to magnesium, elements that they use for a wide range of physiological functions. Although there has been a long history of evolutionary adaptation to the chemistry of the continental crust, special adaptations have allowed some plants to colonize the atypical conditions of serpentine.

Keywords:   aquifer, barrens, carbonate, dunite, fungi, gabbro, harzburgite, mantle, peridotite

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