Effects of nursery fertilization and shading on the seedling quality of the endemic Abies cephalonica Loudon

Forest restoration initiatives are accelerating worldwide, increasing the demand for high-quality nursery seedlings. Seedling performance after planting depends strongly on nursery practices that shape morphology, physiology, and stress tolerance. Despite this, species-specific protocols remain scarce, particularly for endemic Mediterranean conifers such as Abies cephalonica. This species faces high vulnerability due to climate-driven droughts and rising wildfire incidence, which severely limit natural regeneration. To support effective restoration, understanding how nursery techniques affect seedling quality is essential. We assessed, for the first time, the combined effects of shade, fertilization, and seed provenance on the growth and quality of Greek fir seedlings. The results showed that across treatments, seedlings remained relatively small at two years of age. Seed provenance primarily affected shoot morphology, with Parnitha seedlings showing greater height and higher H/D ratios than those from Vytina. Fertilization was the dominant factor enhancing seedling quality, significantly increasing RCD, biomass accumulation, and root system development. Shading effects were complex: 70% shade improved root collar dameter and reduced heght/diameter ratio, while 50% shade maximized root and total biomass. Our study provides critical insights into how these widely used practices influence biomass allocation, root development, and overall seedling quality. The results offer practical recommendations for optimizing nursery protocols and improving restoration success for this threatened Mediterranean species.