COPPICING AFFECTS GROWTH, ROOT-SHOOT RELATIONS AND ECOPHYSIOLOGY OF POTTED QUERCUS-RUBRA SEEDLINGS

Two experiments were conducted to examine the response of Quercus rubr a L. seedlings to coppicing. In a greenhouse experiment, growth, bioma ss distribution, leaf gas exchange, and water and carbohydrate relatio ns were measured for 1-year-old seedlings that were either coppiced wh en dormant at the time of planting or left intact as controls. Coppici ng induced sprouting from the base of the stem, and, in general, the p hysiology of sprouts and controls was similar. However, the relative g rowth rate (RGR) of sprouts was 9% higher than that of controls, allow ing sprouts to compensate fully for the initial mass lost to coppicing . In a second experiment, in an outdoor cold frame, growth, biomass di stribution, leaf gas exchange and plant water relations were measured on 1-year-old seedlings that were either coppiced at the time of plant ing (dormant-coppiced), coppiced soon after bud break (active-coppiced ) or left intact (controls). Dormant coppicing again had little impact on seedling physiology, and dormant-coppiced plants again compensated for initial mass loss with a higher RGR. In contrast, active-coppiced seedlings did not compensate for initial mass loss, as their RGR did not differ from that of controls. By the tenth week of the study, leaf gas exchange rates of active-coppiced sprouts were higher than those of dormant-coppiced and control seedlings. Active-coppiced sprouts als o had a greater soil-to-leaf hydraulic conductivity (expressed on a le af area basis) and a lower ratio of leaf area to root surface area tha n did controls. Across treatments, photosynthetic rate and stomatal co nductance were positively correlated with soil-to-leaf hydraulic condu ctivity, and gas exchange rates and hydraulic conductivity were negati vely related to leaf:root area ratio. Thus, the removal of actively gr owing shoots may have altered subsequent leaf gas exchange largely thr ough coppice-induced changes in leaf-root balance.