Root System Architecture and Plasticity Under Orchard Intensification: A Systematic Review and Narrative Synthesis of Field-Based Evidence

Orchard intensification has transformed fruit production through the combined adoption of higher planting densities, dwarfing rootstocks, localized irrigation/fertigation, and increasingly mechanized orchard management. While aboveground outcomes are well documented, belowground responses remain fragmented across species, orchard contexts, and measurement approaches. This systematic review synthesizes field-based evidence on how orchard intensification and its main operational drivers are associated with root system architecture (RSA) and root plasticity in fruit trees. Following systematic searching and study selection, we performed a narrative synthesis because heterogeneity in species, orchard age, intensification metrics, root assessment methods, and reported traits precluded robust quantitative meta-analysis. The reviewed evidence was more frequently structured around co-occurring drivers—particularly irrigation geometry, rootstock vigour, and soil physical constraints—than around planting density manipulations alone. Root distributions were often reported as predominantly shallow and spatially concentrated within managed zones, especially along tree rows under localized irrigation, with shifts in vertical and lateral allocation that appeared context-dependent. These responses varied with species, genotype, and pedoclimatic conditions, suggesting that intensification does not impose a single deterministic RSA outcome, but rather constrains the potential root zone volume, defined here as the soil volume theoretically available for root growth, within which root distribution may be plastically modulated. Overall, we propose an interpretative framework that may help organize the available evidence by distinguishing (i) the structural definition of an effective rooting domain under intensive management and (ii) plastic modulation of root distribution within that domain. The review also highlights a major evidence gap: the scarcity of factorial field experiments that isolate planting density from irrigation design, genotype, and soil physical constraints.