Coppicing affects growth, root:shoot relations and ecophysiology of potted Quercus rubra seedlings

Abstract

Two experiments were conducted to examine the response of Quercus rubra L. seedlings to coppicing. In a greenhouse experiment, growth, biomass distribution, leaf gas exchange, and water and carbohydrate relations were measured for 1‐year‐old seedlings that were either coppiced when dormant at the time of planting or left intact as controls. Coppicing induced sprouting from the base of the stem, and, in general, the physiology of sprouts and controls was similar. However, the relative growth rate (RGR) of sprouts was 9% higher than that of controls, allowing sprouts to compensate fully for the initial mass lost to coppicing. In a second experiment, in an outdoor cold frame, growth, biomass distribution, leaf gas exchange and plant water relations were measured on 1‐year‐old seedlings that were either coppiced at the time of planting (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 also had a greater soil‐to‐leaf hydraulic conductivity (expressed on a leaf area basis) and a lower ratio of leaf area to root surface area than did controls. Across treatments, photosynthetic rate and stomatal conductance were positively correlated with soil‐to‐leaf hydraulic conductivity, and gas exchange rates and hydraulic conductivity were negatively related to leaf:root area ratio. Thus, the removal of actively growing shoots may have altered subsequent leaf gas exchange largely through coppice‐induced changes in leaf‐root balance.