EFFECTS OF LIGHT GRADIENT ON HEIGHT GROWT H AND CROWN ARCHITECTURE OFA NATURALLY REGENERATED BALSAM FIR

This study characterized the height growth and crown form of 14-year-o ld balsam fir regenerated naturally under a light gradient varying fro m 3 to 83% of photosynthetic photon flux density (PPFD). After 14 year s, total height growth was correlated with percent PPFD (R(2) = 0.766; p < 0.001). From 3 to 25% of PPFD, balsam firs went from a suppressed stage with an umbrella type crown shape to a full grown stage with a cone type crown shape. This morphological change was caused by a great er increase in leader length compared to the mean nodal branches lengt h. The number of nodal and internodal branches increased with PPFD. Ba lsam fir crown morphology showed a strong plasticity with a light grad ient going from 3 to 83% of PPFD.