Record Details
Meta-sedimentary bedrock as an alternative source of water for forest ecosystems in a Mediterranean climate
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Meta-sedimentary bedrock as an alternative source of water for forest ecosystems in a Mediterranean climate |
| Names |
Zwieniecki, Maciej A.
(creator) Newton, Michael (advisor) |
| Date Issued | 1995-06-21 (iso8601) |
| Note | Graduation date: 1996 |
| Abstract | Evaluation of meta-sedimentary bedrock as a source of stored water available to plants in a mediterranean climate is presented based on: root length distribution (RLD), root morphology, rock water holding capacity and seasonal pattern of water depletion. Studies were performed in southwestern Oregon under young stands of whiteleaf manzanita, ponderosa pine, Douglas-fir and Pacific madrone. RLD analysis shows that more then one quarter of the total root length of ericaceous plants is located in the rock layer. Stepwise procedures identified the best fitting multiple-regression model for relating RLD to depth, bulk density of rock and the space penetrable by roots (SPR). Linear expressions of SPR and depth were found to be significant explanatory variables. Roots of manzanita and madrone occupy rock fissures as small as 100 urn. The root stele remains cylindrical in shape without visible mechanical stress, the cortex became flat, creating "wing-like" structures on each side of the stele. Fine particles that fill the space between root cortex and rock matrices create a continuous conduit for water flow. Pore volume distribution of rock was measured in four functional ranges of pore size: gravitational water, available water content (AWC), slowly available water (SAW) and unavailable water (UW). An appreciable amount of pore volume is present within the AWC and SAW, ranging downward from 20% of total rock volume in rock at a density of 2.1 to negligible at density 2.67 grams per cubic centimeters. End-of-summer water content measured in-site in the field and bio-assay results shows that plants extract this water from the rock matrix during the typical water stress of a mediterranean type summer. Water depletion from soil/rock profile follows distinct patterns according to vegetation type, based on neutron probe measurements from aluminum access tubes 3.2 m deep. Measurements were taken during two growing seasons (1993 and 1994) under pure cover of the above species. Both conifers show very limited ability to utilize water from bedrock. Ericaceous plants were very efficient in depletion of water from the rock layers, using all available water measured by the access tubes. Water resources used by both types of plants overlaps considerably and competition will be very strong in species mixtures. Ability to utilize bedrock water by ericaceous plants appears to offer a major competitive advantage. |
| Genre | Thesis/Dissertation |
| Topic | Plant-water relationships |
| Identifier | http://hdl.handle.net/1957/13630 |
