Abstract
The relationship between quadratic mean diameter and tree density appeared curvilinear on a log–log scale, based on data from direct-seeded slash pine (Pinus elliottii var. elliottii Engelm.) stands. The self-thinning trajectory followed a straight line for high tree density levels and then turned away from this line as tree density decreased. A system of equations was developed to model the reciprocal effects of stand diameter and density through time. The equations performed well for these data. Since the model is constrained according to the self-thinning rule, it should provide reasonable extrapolation. FOR. SCI. 46(3):317–321.