Transplanting Shock and Water Relations in Urban Tree Species
Large-caliper trees transplanted into urban settings show low survivability. A 1-year transplanting experiment was conducted using Acer ginnala and Acer truncatum. Trees were blocked by species and size, with three blocks of four trees per species. Three trees of each species were left in their original location for purpose of comparison. A 2 × 2 factorial was used to assign treatments (water, water and top prune, top prune, and transplanted control). Using a Schollander Pressure Bomb, predawn and midday water potential measurements were recorded biweekly from early May through September. The first 8 weeks following transplant, all transplanted trees of both species had significantly (P ≥ 0.05) more negative midday water potentials than those not transplanted. During periods of stress, predawn water potentials of transplanted trees did not recover overnight. By September, irrigated trees had water potentials not significantly different from those of trees not transplanted. Canopy closure was measured on the same schedule using a Li-Cor Canopy Analyzer. Leaf area index of transplanted trees was nearly half that of non-transplanted trees. Trees treated with water did have slight, but significantly greater leaf area indexes than those of other treatments. It appears that the most notable effect of transplanting is the inhibition of leaf expansion resulting from early spring water stress. This leads to an open canopy for the whole season following transplant.