Shoot growth patterns as indicators of root system recovery after transplanting in nursery-grown hackberry trees

This study on young planted hackberry trees identifies distinct recovery stages where aboveground traits reliably predict root system regeneration, providing a basis for non-destructive assessment of post-transplant recovery. Transplanting trees disrupts the root system, creating a root-to-shoot imbalance that challenges recovery. Post-transplant recovery is heterogeneous, with distinct growth dynamics. We hypothesized that: (1) this heterogeneity represents few growth patterns; (2) these patterns reflect specific root regeneration behaviors; and (3) aboveground traits could indicate root system recovery. To test them, we transplanted 600 young bare-root Celtis australis and monitored their recovery over two years. A total of 112 trees were selectively excavated at the end of each growing season to characterize root regeneration and its links with aerial growth categories. Two indicators, the Root Regeneration Score (RRS) and the Aerial Field Index (AFI), were developed to evaluate aerial growth dynamics and root regeneration. Our results showed that post-transplant heterogeneity in aboveground growth could be categorized into distinct patterns based on budbreak timing and shoot elongation dynamics. These aerial growth categories corresponded to specific root regeneration behaviors, characterized by differences in the proportion of regenerated pruned roots, new root production, and pruning wound closure rates, key traits used to construct the RRS. The AFI, integrating time to budbreak, trunk growth, and maximum shoot length, effectively distinguished growth categories and demonstrated strong predictive power for root recovery. This study provides a framework for characterizing post-transplant recovery dynamics and emphasizes the functional interplay between root and shoot recovery. The AFI offers a standardized tool for evaluating plantation success and informing urban forestry management.