A PRELIMINARY QUANTIFICATION OF THE IMPACTS OF ASPEN TO CONIFER SUCCESSION ON WATER YIELD- II. MODELING RESULTS1

Authors

  • Gerald F. Gifford,

  • William Humphries,

  • Richard A. Jaynes

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    • 2

      Respectively, Professor and Chairman, Watershed Science Unit, College of Natural Resources, Utah State University, UMC 52, Logan, Utah 84322; Graduate Research Assistant currently employed with James L. Grant and Associates, Denver, Colorado; and Lawyer, currently serving with the U.S. Army.


  • 1

    Paper No. 83146 of the Water Resources Bulletin.

Abstract

ABSTRACT: Heat pulse velocity techniques were developed for effective monitoring of water movement in aspen (Populus tremuloides), subalpine fir (Abies lasiocarpa), and Englemann spruce (Picea engelmannif). Water loss was monitored in replicated trees of each species for one year. These data were used to modify the plant activity index (a reflection of the ability of plants to transpire water at various times during a year) and the crop coefficient (a reflection of differences in consumptive use rates of water by different vegetation types when all other factors are held constant) for each species within the model ASPCON, a deterministic, lumped-parameter model describing the hydrology of aspen to conifer succession. Results of the modeling in dicate 18.6 cm net loss of moisture available for streamflow when spruce replaced aspen, and a loss of 7.2 cm when fir forests replaced aspen. The aspen to conifer successional trend appears, therefore, to be significantly reducing water yields in the western United States.

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