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Journal of Environmental Quality Abstract -

Sample Size Requirements for Estimation of Throughfall Chemistry Beneath a Mixed Hardwood Forest


This article in JEQ

  1. Vol. 18 No. 3, p. 274-280
    Received: Feb 21, 1988

    * Corresponding author(s):
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  1. K. M. Kostelnik,
  2. J. A. Lynch *,
  3. J. W. Grimm and
  4. E. S. Corbett
  1. USDA-Forest Service, Northeastern Forest Exp. Stn., University Park, PA 16802.



Six rainfall events were intensively sampled below a mixed hardwood forest canopy in central Pennsylvania to determine sample size requirements for estimation of thronghfall volumes and ionic concentrations. Evaluation of the ionic parameters of thronghfall revealed that the concentrations of most major ions were nonnormally distributed. Differences in the distributions of concentrations were found to occur between ions as well as between storms. Significant departures from normality were mainly due to right-skewness. Only H+ exhibited a left skewed sample distribution. None of the basic transformations were effective in normalizing all parameters. A high degree of spatial variability was observed for each of the chemical parameters. Nitrate and hydrogen ions (NO3 and H+), were found to be the least variable, whereas vegetatively mobile ions such as K+ and Mg2+ exhibited the greatest variability. Because of high event-to-event variation in the distributions of ion concentrations, specific sample-size requirements should be estimated for each ion through preliminary sampling of thronghfall precipitation from several storms.

Contribution from the Pennsylvania State Univ. Agric. Exp. Stn. Journal Series no. 7879.

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