STAND DENSITY AND PRODUCTION PROCESSES IN BALSAM FIR STANDS

Plants use acquired carbon and energy to sustain life and for growth, so growth responses to competition can be understood by considering (1) resource acquisition, (2) division of resources between life support and synthesis, and (3) efficiencies of synthesis and maintenance processes.; Judging from patterns of foliage distribution within crowns, dominating trees produced more photosynthates than subordinate neighbours primarily by having larger crowns, and not by having higher annual photosynthetic production per kilogram of foliage. Larger trees did not increase dominance by allocating a larger proportion of acquired resources to foliage growth. Dominating trees had higher ratios of leaf mass to total plant mass than subordinate neighbours, implying they would grow faster per kilogram of foliage mass if efficiencies of maintenance and synthesis processes were equal. Since growth per kilogram of foliage by dominating trees were not greater than those of subordinate trees, they must use resources less efficiently.; Foliage was not as efficiently displayed to intercept light for photosynthesis in the total canopy of the thinned stand as in the upper canopy of the unthinned stand, so the increase of photosynthesis rate did not make the thinned stand more effective at acquiring resources. Growth per kilogram of foliage was greater in the thinned stand than in the unthinned stand, but these differences were not as great as differences in ratios of leaf mass to total plant mass. This suggests that the thinned stands used acquired resources less efficiently than the unthinned stands.; Use of acquired resources was examined by measuring respiration and growth of selected internodes on specific trees in a thinned and unthinned stand. Results suggest that slow-growing trees performed maintenance more efficiently than fast-growing trees, and that efficiencies of synthesis processes were lower for large trees than small trees.