Is There a Light Regime Determined Tree Ideotype?

A theoretical analysis of the light interception of isolated tree crowns is presented. Two types of crown, ellipsoid and cone, are studied. Assuming that tree crowns are black bodies it is revealed that for any narrow-crowned tree there exists a most-sensitive solar elevation range at which the momentary light interception is maximized. The temporal and latitudinal variations in angular distribution of possible sunshine hours, the concomitant incoming direct light energy, and the light intercepted by isolated crowns of different shapes and different height to width ratios are computed. The results are compared with established hypotheses on crown shape as an adaptation to local radiation climates.