On sites characterized by shallow soil in semiarid climates, lack of bedrock description may lead to underestimates of total storage capacity of water available for plants, and therefore of potential site productivity. Sample rocks from southwestern Oregon soil‐rock profiles excavated beneath typical forest plant communities were examined for pore volume distribution by means of mercury intrusion porosimetry and oversolution equilibrium. Four ranges of pore size were distinguished: gravitational water, available water content (AWC), slowly available water (SAW), and nonavailable water. Pore volume for AWC and SAW was associated with bulk density and in low density rock, was 20% of volume. Results suggest that metasedimentary rock has the potential to be a major reservoir of plant available water in semiarid climates.
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Zwieniecki et al. (1996) studied this question.