Growth of Fagus sylvatica L. and Picea abies (L.) Karst. Seedlings Grown in Hiko Containers in the First Year after Planting

In forest management in Poland, there are no standards for the quality and suitability for planting seedlings produced in nursery containers; therefore, research contributing to the development of such guidelines is important. We investigated the growth reaction of European beech and Norway spruce seedlings growing in container technology one year after planting on an experimental forest plantation. The seedlings used in the study were three experimental variants grown in a container nursery differing in fertilization. Two heights of seedlings were measured, i.e., after the first growing season on the experimental plantation and the initial (obtained in the forest nursery), and the annual (AHI, cm) and relative height increments (RHI, %) were calculated. The regression of the RHI of seedlings to their initial height was calculated, and the equations obtained were used to determine the optimal range of seedling height at the stage of nursery growth at which they will achieve the maximum increment in the first year of growth on the plantation. The change from foliar fertilization to a mixed one affected beech and spruce seedling parameters; however, it did not affect the diversity of their survival on the experimental plantation. Higher seedlings planted on the experimental plantation were characterized by a smaller RHI. The optimal range for the height of seedlings obtained at the nursery stage of growing, which determined the maximum value of the AHI after the first year of growth after planting, was 18–36 cm for beech and 14–25 cm for spruce.