  Calibration of the self-thinning frontier in even-aged monocultures is
hampered by scarce data and by subjective decisions about the proximity of data
to the frontier. We present a simple model that applies to observations of the
full trajectory of stand mean diameter across a range of densities not close to
the frontier. Development of the model is based on a consideration of the slope
s=ln(Nt/Nt 1)/ln(Dt/Dt 1) of a log-transformed plot of stocking Nt and mean
stem diameter Dt at time t. This avoids the need for subjective decisions about
limiting density and allows the use of abundant data further from the
self-thinning frontier. The model can be solved analytically and yields
equations for the stocking and the stand basal area as an explicit function of
stem diameter. It predicts that self-thinning may be regulated by the maximum
basal area with a slope of -2. The significance of other predictor variables
offers an effective test of competing self-thinning theories such Yoda's -3/2
power rule and Reineke's stand density index.

Quantitative Methods