Résumé
Agroforestry, which combines crops and trees, promotes biodiversity and ecosystem services. Despite its potential, the successful establishment of young trees within the agroforestry system remains a major challenge for farmers, who may be faced with heterogeneous recovery after planting. This research aims to identify indicators to assess tree recovery and root health after planting, while also providing a better understanding of the factors influencing the establishment of young trees. Our study analysed the recovery of 600 young Mediterranean hackberry trees (Celtis australis L.) planted with bare roots across four micro-plots with varying soil types. Different pruning protocols before planting enabled us to establish various root/shoot ratio categories and to assess their impact on recovery quality. Over the two years following planting, we monitored the trees' establishment phase, which included bud burst, shoot elongation, and trunk growth. Through 125 targeted excavations, we investigated the correlation between aerial growth dynamics and the recovery and health status of root systems. Additionally, we analysed spatial growth patterns to better understand the influence of soil on tree recovery. After planting, significant heterogeneity in tree recovery was observed. A higher root/shoot ratio at planting correlated with improved survival and recovery. Analysis of the aerial system's growth identified four primary categories of growth dynamics, associated with the traits of annual shoots (number of elongation cycles, length of elongation units, leaf area, and type of buds mobilised). Excavation data indicated that each category of aerial growth dynamics was linked to distinct root system behaviours regarding root regeneration and health. A relationship was found between the number and size of annual shoots, the total leaf area, and the number and size of new roots developed on the root system. This implies that visible annual shoots on the aerial system can serve as indicators to infer the less observable root production in the soil. Spatial analysis uncovered non-random patterns of growth, suggesting that soil characteristics significantly influence recovery. Findings underscore the importance of meticulous selection of young trees for planting and demonstrate that morphological indicators on the aerial system can serve as effective proxies to monitor successful recovery and root health during the establishment phase. The spatial distribution of tree growth enhances our understanding of soil characteristics and functionality, thus aiding decision-making for soil management in agroforestry systems. Overall, our results provide deeper insights into the critical phase of young tree establishment, essential for achieving the long-term goals of agroforestry.