Carbon budgets of Quercus rubra L. seedlings at selected stages of growth: Influence of light

Abstract

To determine potential growth responses of northern red oak (Quercus rubra L.) seedlings to various field light environments, carbon budgets of one-, two-, and three-flush seedlings were calculated. Leaf carbon dioxide exchange rate (CER), root respiration, and growth analysis provided inputs for the budgets. Daily CO/sub 2/ assimilation rates obtained from these budgets were lower than, but consistent with, actual red oak seedling growth rates. The budgets predicted that optimum daily CO/sub 2/ assimilation occurs under saturating irradiances in the absence of other stresses (e.g., drought), and that daily CO/sub 2/ assimilation is inadequate to match seedling respiration under the shade of a typical closed forest canopy. Calculated minimum incident photosynthetic photon flux densities required for sufficient CER to balance daily seedling respiration ranged from 30 to 150 ..mu..mol photons m/sup -2/ s/sup -1/, depending on plant size. 44 refs., 7 tabs.