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    Author(s): William R. Harms
    Date: 1983
    Source: Proceedings of the Second Biennial Southern Silvicultural Research Conference
    Publication Series: Scientific Journal (JRNL)
    Station: Southern Research Station
    PDF: Download Publication  (274.0 KB)


    A flexible sigmoid function of the form S = 1/[1 + (H/Hc)0], where S is survival expressed as the ratio of number of living trees (N) to the number of trees at stand  establishment (Ni), H is mean stand height, Hc is mean height at S = 0.5, and 0 is an exponent defining the shape of the curve, was fit to a set of loblolly pine survival data cover­ing a range of densities from 1000 to 16,000 trees per acre. The equation provided an adequate fit to the data vith r2 values from 0.76 to 0.98. The estimated parameters Hc and 0 were found to be correlated to initial density. Both can be predicted satisfactorily with regressions of the form
    Hc = b0Ni b1, and 0 = b0 + bi/Ni.

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    Harms, Williams R. 1983. An empirical function for predicting survival over a wide range of densities. Charleston, SC. In: Proceedings of the Second Biennial Southern Silvicultural Research Conference; 1982 November 4-5; Atlanta, GA: p.334-337.

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