PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Effects of light acclimation on the photosynthesis, growth, and biomass allocation in Castanea dentata L. seedlings.
Wang, G. Geoff1, Bauerle, William1, Mudder, Brian1, 1 Clemson University, Clemson, SC
ABSTRACT- Before eradicated by blight (Cryphonectria parasitica), American chestnut (Castanea dentata) was a widely distributed tree species dominating the eastern deciduous forest. To develop a viable silvicultural system for reintroducing blight-resistant American chestnut into its formal range, we need to understand the photosynthetic and growth response of American chestnut to various light environments. In a greenhouse study, we grew American chestnut seedlings at four light levels (4, 12, 32 and 100% of full sunlight) to examine how light intensity influences photosynthesis, growth, and biomass allocation. Maximum photosynthesis, light compensation, light saturation and dark respiration were 9.08, 29.5, 203.50, and 1.97 
mol m-2 s-1, respectively. When measured at the acclimated light level, net photosynthesis rate increased linearly with light, while water use efficiency peaked at 32% light. Both height and diameter increased with light level. However, seedlings only grew laterally under 4% light. Total biomass increased linearly with light levels and root to shoot ratio was lower under 4 and 12% light. Regardless of light level, > 70% of total biomass was allocated to shoot growth. As the level of shade went up, specific leaf area significantly increased. These observed morphological and physiological light acclimation responses suggest that American chestnut is more shade tolerant than previously reported, which partially explains why American chestnut has persisted as understory sprouts for nearly a century. The shade-tolerance and fast growing characteristics suggest that an underplanting and release or gap-phase regeneration approach would be feasible. The results indicate, therefore, that a clearcut and planting approach may not be necessary when reintroducing blight-resistant American chestnut to its former range.
Key words: American chestnut, reintroduction, regeneration