Leaf stoichiometry of European beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.) seedlings grown on an innovative peat-free organic substrate.

The impact of changing climate conditions on the stability, structure and biodiversity of forest ecosystems in Europe is well known. The main threat to trees is the continuous increase in temperature and changes in moisture conditions, especially in the soil. Very often, seedlings with a covered root system grown in container nurseries are used to rebuild forests or replace decaying spruce monocultures. The cultivation of such seedlings is carried out on a substrate whose main component is peat, the extraction of which poses a serious threat to the environment. Leaf nutrient stoichiometry offers an important indicator of the nutritional status of forest tree seedlings. This study assessed the potential of alternative peat-free substrates in nursery production and evaluated European beech and pedunculate oak seedlings with a covered root system, examining whether it ensured their proper nutrition and appropriate stoichiometric ratios of macroelements in the assimilation apparatus when compared to seedlings produced under the same conditions on a peat substrate. These studies were carried out in the production of beech and oak seedlings on innovative, organic, peat-free substrates using standard fertilization and a new fertilization developed by the research team. The peat-free substrates were characterized by higher concentrations of nitrogen (N), potassium (K), and phosphorus (P), which promote more effective growth. Our elemental leaf stoichiometry results indicate their excess in relation to standards, which suggests that plants can use these elements as reserves for the future. Results also showed strong correlations between the contents of elements in the soil and the growth parameters of seedlings. The peat-free substrates showed a beneficial effect on seedling growth, thus highlighting their potential as suitable substrates in nurseries.