Quality matters. A quantitative review on the effect of seedling morphology and nursery practices on the outplanting performance of forest plantings.

Most forest plantings worldwide are performed through the establishment of seedlings grown in nurseries. During nursery cultivation, seedlings are exposed to several environmental conditions, such as temperature and growing media pH, and are supplied with resources such as water, light, and mineral nutrients for optimal growth. Plants acclimate to these varied nursery conditions by adjusting morphological and physiological characteristics, leading to distinct phenotypes with specific morphological and physiological traits. Once outplanted, these morphological and physiological traits, referred to as functional attributes, determine seedling water, carbon, and mineral nutrient economy, as well as their resistance and resilience to stress, and consequent ability to establish and grow. Seedlings that perform “satisfactorily” on a forest site are considered high quality because their functional attributes maximize establishment in that particular environment. The “target plant concept” (TPC) emphasizes matching seedling functional attributes and nursery cultivation to the planting environment. In this conceptual framework of “good” forestation practices, the selection of species and provenances, reproductive material, and outplanting practices align with the objectives and environmental conditions of forest restoration. Consequently, defining suitable seedling functional attributes or phenotypes for different planting scenarios is an important challenge of the TPC.