Nursery Resource Efficiency Drives Seedling Quality and Field Establishment of Pinus devoniana for Forest Restoration

Forest restoration depends on producing seedlings able to convert nursery inputs into functional traits that persist after outplanting. This study evaluated whether contrasting nursery resource-management profiles, derived from container volume, fertilization, and irrigation, shaped seedling quality and field establishment of Pinus devoniana. Seedlings were conditioned for six months under eight profiles and validated during one year under field conditions. Nursery evaluation included morphology, biomass allocation, Dickson Quality Index (DQI), nutrient status, and proline; field validation included survival, growth, ectomycorrhization, stomatal density, and lignification. Profiles differed significantly in root collar diameter, height, root biomass, total biomass, root–shoot ratio, and DQI. The 5 L fertilized and irrigated profile produced the highest integrated quality, with 140.9% more root biomass than the weakest root profile and 144.3% higher DQI than the lowest-quality profile. Nitrogen- and proline-separated nutrient and stress responses showed that higher nutrient status did not always imply lower stress. Field survival reached its highest value under the 5 L fertilized and irrigated profile, exceeding several 1 L profiles by 74.8%. DQI was positively associated with field survival (r = 0.71, p = 0.048), supporting a nursery-to-field carry-over effect. The findings highlight rooting space as a leverage point for improving reforestation outcomes.