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Seasonal Physiology of Douglas-fir Saplings: Response to Microclimate in Stands of Tanoak or Pacific Madrone

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Plant water potential, leaf conductance, and photosynthesis of saplings of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) were monitored monthly in 1986 through 1988. The objective was to describe influences of microclimate (light, soil water, temperature, and relative humidity) associated with young stands of tanoak (Lithocarpus densiflorus [Hook. & Arn.] Rehd.) or Pacific madrone (Arbutus menziesii Pursh) on Douglas-fir physiology. Hardwood shade reduced photosynthetically active radiation to 20 to 38% of full sunlight; as a result, photosynthesis of Douglas-fir shaded by hardwoods was light-limited throughout the year. Soil water potentials (30-cm depth) in summer (July through September) averaged -0.64 MPa in the presence of hardwoods and - 0.23 MPa in their absence. Reduced soil water availability in the hardwood stand, coupled with elevated air temperatures and lower relative humidities, reduced photosynthesis of associated Douglas-fir. Stomatae neared complete closure at the following plant water potentials: -2.3 (tanoak), -2.5 (Douglas-fir), and -3.4 MPa (madrone). Although seasonal rates of photosynthesis did not vary greatly among the three species, specific water-use patterns were apparent. The abilities of species to minimize water stress were ranked as tanoak > Douglas-fir > madrone. For. Sci. 40(1):59-82.

Keywords: Interference; conductance; photosynthesis; plant water potential; soil water potential

Document Type: Journal Article

Affiliations: Professor, College of Forestry, Oregon State University, Corvallis, OR 97331

Publication date: 1994-02-01

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  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
    Forest Science is published bimonthly in February, April, June, August, October, and December.

    2015 Impact Factor: 1.702
    Ranking: 16 of 66 in forestry

    Average time from submission to first decision: 62.5 days*
    June 1, 2016 to Feb. 28, 2017

    Also published by SAF:
    Journal of Forestry
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