Robert C. Graham¹, Ann M. Rossi¹, Kenneth R. Hubbert²

¹ Soil & Water Sciences Program, Dept. of Environmental Sciences, University of California, Riverside, California 92521-0424, USA
² USDA Forest Service, Pacific Southwest Research Station, 3644 Avtech Parkway, Redding, California 96002, USA

Abstract

Weathering processes transform hard fresh rock into friable weathered rock, which is then physically disrupted to become soil. These regolith materials mantle the land masses and support terrestrial life but their formation involves some of the least understood of Earth’s surficial processes. The conversion of biologically inert hard rock to a hospitable substrate for organisms begins with the production of porosity by weathering. Porosity allows water to flow through weathered rock, but it also imparts a water-holding capacity so that water can be stored for prolonged use by organisms. Organisms themselves, in the form of microbes and plant roots, invade the rock as porosity forms. Production of porosity is the fundamental process responsible for converting rock into a medium capable of supporting terrestrial ecosystems. Consequently, the rate of porosity formation during rock weathering is the ultimate measure of the production and sustainability of ecosystem-functional substrates.

Manuscript received 22 May 2009; accepted 15 September 2009

DOI: 10.1130/GSAT57A.1

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