Dissertation Research: Nitrogen and Water Utilization by Co-occurring Evergreen Oak that Differ in Rooting Depth

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The patterns of water and nitrogen acquisition and utilization by two species of oaks growing on serpentine-derived soil will be investigated. Preliminary results indicate that Quercus agrifolia and Q. durata differ in rooting depth, and that the availability of water and nitrogen in the soil varies with both depth and season. It is hypothesized that, as a result of spatial interactions between soil resource availability and root distribution, neighboring individuals of Q. durata and Q. agrifolia have access to different levels of nitrogen and water. It is further predicted that neighboring individuals of the two species should differ in the acquisition and utilization of nitrogen and water. These hypotheses will be investigated using both field and controlled environment studies. Information on rooting depth will be compared with the availability of water and nitrogen at several depths. The seasonal patterns of nitrogen and water acquisition and utilization for several sets of adjacent size matched plants will be followed, and the ways in which Q. durata and Q. agrifolia acclimate to nitrogen and water availability will be investigated by growing plants under nutrient sand-culture conditions designed to simulate the resources available to shallowly and deeply rooted plants.