Forest shadows: how much shelter in a shelterwood?

A simulation model is presented that will permit silviculturists to estimate the shade cast on any site at any time by a randomly distributed conifer stand of any stocking level. Computational requirements are modest. Simple situations may be solved in an hour or so on a programmable hand calculator; most complex situations can be handled on a desk microcomputer. Trees are modelled as a crown consisting of a cone on top of a cylinder, and the crowns may vary in density. The bole is modelled as a solid cylinder. Relative dimensions may be varied to simulate almost all regular conifer tree forms. The projected shadow area of trees is integrated for any number od independently distributed trees to obtain the relative shadow area on the ground surface. Alternatively, the model permits the determination of the number of trees of any given dimensions per unit are needed to provide a given degree of shade.