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Abstract
In southwestern California,
Quercus agrifolia distribution closely matches regions of granitic regolith. High annual evapotranspiration demand and inherent shallow soil conditions lead to a dependence on a deep rooting system and an ability to access water from deep within the regolith. Most of the plant available water in weathered granitic rock is held within micropores, which are generally too small for roots to access. It is not clear how water held in the rock matrix reaches the roots, which are confined to the fractures. Hyphae are narrow and able to explore a greater substrate volume for resources. Our study addresses the vertical composition of both endo- and ecto-mycorrhizae in weathered granitic rock in an effort to determine if mycorrhizae are available to act as conduits to transport water from rock matrix to roots. Water status, morphology, nutrients, root and mycorrhizae distribution of three
Q. agrifolia trees were characterized from a 15-meter-wide by 4-meter-deep profile consisting of 30 to 70 cm of soil and 330 to 370 cm of weathered bedrock. Plant available water within the soil fraction was depleted by the end of June; therefore plants must rely on water available within the fractured bedrock for the remainder of the growing season and during the dry season. Roots greater than 1 mm are present throughout the entire 4-meter deep profile. Fine roots
Parent Publication
Citation
Bornyasz, M.; Graham, R.; Allen, M. 2002. Distribution of
Quercus agrifolia mycorrhizae deep within weathered bedrock: a potential mechanism for transport of stored water. In: Standiford, Richard B., et al, tech. editor. Proceedings of the Fifth Symposium on Oak Woodlands: Oaks in California''s Challenging Landscape. Gen. Tech. Rep. PSW-GTR-184, Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 821-822
