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.
Changing climate conditions are having a profound impact on global photosynthesis and posing a threat to forest ecosystems in Europe, negatively impacting their stability, structure, and biodiversity. Recent research clearly shows that the severity of soil and ecological droughts and changes in moisture conditions have significantly increased in recent years during the growing season, posing a serious threat that directly impacts forest productivity. It is predicted that in the long term, climate change, particularly the severity of droughts, will lead to increased water stress, and the occurrence of extreme weather events may pose some of the most serious threats to forest productivity through decreased biomass growth and increased tree mortality worldwide. Moreover, a steady increase in the frequency of extreme disturbances, such as long-term droughts, floods, and heat waves, is predicted. Global warming will therefore have a significant impact on European forest ecosystems and may result in a shift in the competitiveness and dominance of species with contrasting ecological characteristics and varying drought tolerance, as well as their ability to regenerate quickly. Mixed stands will therefore become an important component. Beech (Fagus sylvatica L.) is the most widespread forest tree in the temperate zone of Europe, naturally occurring on a wide range of soil types. Its range is expanding northwards and to higher mountain locations in response to the changing climate -- an expansion that may cause the species to eventually replace spruce monocultures (Picea abies L.). However, scientists predict changes in the distribution of the species in Europe especially in mountainous regions where rising temperatures and an increase in the frequency of extreme weather events such as drought or water scarcity are leading to a significant reduction in habitats suitable for beech at lower elevations (below 500 m above sea level).
The second most economically and ecologically valuable tree species in Central Europe is the pedunculate oak (Quercus robur L.). This species is considered one of the most important elements of mixed stands with the ability to adapt to climate change. In stands, oak is underplanted with shade-tolerant tree species that are more competitive in order to obtain high-quality wood. This competition hampers the natural regeneration of the oaks, necessitating their regeneration via artificial methods. In addition, the species could play a key role in the adaptation of Europe's forests to changing climatic conditions, as they show greater resistance to heat stress and drought compared to the common beech. Models assume that the range could expand northward with the oak's presence at higher elevations previously overlooked due to colder climates.
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. Peatlands are known to store significant amounts of soil carbon (estimated at up to one-third of the global supply) and have the potential to mitigate climate change. Peatlands occupy a small part of the world's land surface, but their degradation releases 2 billion metric tons of CO emissions into the atmosphere. In recent years, in several European countries such as Austria, England, Germany, Finland, Ireland, Northern Ireland, Scotland and Wales, measures are being taken to protect, restore and carry out sustainable management over peatland use depending on the recognized condition of the habitat. Therefore, it is becoming extremely important to conduct research on creating an alternative substrate to peat, with composted municipal waste or biocomposts cited among the materials with which to replace peat.
Some researchers have focused on dead wood as a substrate that provides favorable physicochemical, biochemical, and moisture properties for seedlings of various tree species. The most important consideration in the production of an alternative substrate is to provide appropriate chemical properties for plant growth and the proper nutritional status of the seedling. A well-analyzed component in the literature is coconut fiber, which has a high pH, high potassium content, and a high C: N ratio, which may negatively affect nitrogen availability. In turn, the use of green compost is difficult to analyze and evaluate due to its variable chemical properties; another problem resulting from the use of this type of substrate is increased susceptibility to fungal pathogens, weed seeds, or insects, which would adversely affect the development of seedlings. On the other hand, post-logging waste in the form of bark and wood chips has shown high contents of toxic phenolic compounds and other components that can be phytotoxic and constitute a barrier for plants planted on such a substrate. Therefore, it is extremely important to select a substrate that will meet the most important chemical, physical, and biological criteria for seedling growth.
To assess the potential of alternative substrates in nursery production, it is necessary to assess the nutrition of the seedlings grown on them. Leaf stoichiometry, which deals with the balance of multiple elements in ecological interactions and plays an important role in assessing nutrient uptake, plant composition, and ecosystem functions, can be used for this purpose. Good growth is conditional on appropriate plant nutrition, and especially on maintaining the appropriate proportions of nutrients in plant tissues. Nutrient concentrations, and their mutual relationships, in the leaves of forest trees are important indicators of the trees' functioning. The concentration of nutrients in leaves depends on many factors: the amount and availability of water, the length of the vegetation period, the content of nutrients in the substrate, ionic antagonisms, mobility, and ability to absorb ions. Some authors have highlighted the imbalance of proportions between macroelements in European beech leaves, especially the negative trend in phosphorus, calcium, and magnesium nutrition. In our study, we evaluated the potential of using an innovative peat-free substrate for the production of beech and oak seedlings with a covered root system compared to the standard peat used, checking whether the new substrate provides proper nutrition to the seedlings and appropriate stoichiometric ratios of macronutrients in the assimilation apparatus. In addition, we analyzed the effect of fertilization (solid and liquid) as a supplement to macronutrients.