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Jingjing Yin, Nina L. Bassuk, Madeline W. Olberg, and Taryn L. Bauerle

In our study, we investigated whether root hydraulic conductance is related to post-transplant recovery. We used two Quercus species that differ in their transplant ability, Q. bicolor and Q. macrocarpa. Q. bicolor easily survives transplanting, whereas Q. macrocarpa often does not. We compared root hydraulic conductance after transplanting between control (without root pruning) and root-pruned, 1-year-old, small-caliper trees. We also examined the effects of transplant timing on post-transplant recovery of large-caliper trees. Hydraulic conductance in fine roots was correlated with recovery of the two Quercus species after transplanting. Six months after transplanting, small-caliper Q. bicolor trees had similar specific hydraulic conductance (K S) in fine roots compared with the K S before root-pruning, whereas fine root K S in small-caliper Q. macrocarpa trees decreased. Lower pre-dawn and midday xylem water potential in root-pruned Q. macrocarpa 6 weeks after transplanting indicates that root-pruned Q. macrocarpa experienced transplanting-induced water stress. For large-caliper trees, all Q. macrocarpa trees exhibited typical symptoms of transplant shock regardless of transplant timing, which was the result of higher vulnerability to mild water stress compared with Q. bicolor, resulting in a large reduction in fine root K S. Fine root K S in spring-transplanted Q. bicolor trees was much higher than that in fall-transplanted trees, implying spring transplanting is optimal for Q. bicolor. Other intrinsic characteristics of the species should be considered in the future when making better decisions on transplant timing such as xylem anatomy, carbon storage, rhizosphere conditions, and plant growth.

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J. Roger Harris, Nina L. Bassuk, Richard W. Zobel, and Thomas H. Whitlow

The objectives of this study were to determine root and shoot growth periodicity for established Fraxinus pennsylvanica Marsh. (green ash), Quercus coccinea Muenchh. (scarlet oak), Corylus colurna L. (Turkish hazelnut), and Syringa reticulata (Blume) Hara `Ivory Silk' (tree lilac) trees and to evaluate three methods of root growth periodicity measurement. Two methods were evaluated using a rhizotron. One method measured the extension rate (RE) ofindividual roots, and the second method measured change in root length (RL) against an observation grid. A third method, using periodic counts of new roots present on minirhizotrons (MR), was also evaluated. RE showed the least variability among individual trees. Shoot growth began before or simultaneously with the beginning of root growth for all species with all root growth measurement methods. All species had concurrent shoot and root growth, and no distinct alternating growth patterns were evident when root growth was measured by RE. Alternating root and shoot growth was evident, however, when root growth was measured by RL and MR. RE measured extension rate of larger diameter lateral roots, RL measured increase in root length of all diameter lateral roots and MR measured new root count of all sizes of lateral and vertical roots. Root growth periodicity patterns differed with the measurement method and the types of roots measured.