Abstract
Currently, reforestation efforts focus primarily on deciduous species replacing coniferous monocultures. Related to this are efforts to identify their interactions in the soil. Root exudation has many functions, including plant communication with soil microorganisms and the solubilisation of nutrients. Root exudates reflect the situation in the soil, as well as refer to the plant species and health/fitness. The idea here was to reveal the typical content of low-molecular-weight phenolic acids in the soil solution that occur in the early-life stages of most typical temperate deciduous trees Quercus robur, Sorbus torminalis, Fagus sylvatica and Acer pseudoplatanus, including the fast-growing invasive Robinia pseudoacacia. To compare their initial strategies and ambient, seedlings were planted in the pot experiment for one season since emergence. The following phenolic acids were detected in detectable concentrations: vanillic, 4-benzoic, syringic, p-coumaric and salicylic. Each tree species tested showed a unique fingerprint in these acids, which can be considered species-specific, i.e., their presence differed among the species. Robinia pseudoacacia (unlike the other trees tested) showed the ability to maintain high levels of p-coumaric acid in the soil solution, indicating its potential to survive in nutrient-poor soil and achieve rapid growth. On the contrary, the levels of all phenolic acids detected in the soil solution of Quercus robur and Sorbus torminalis were very low. These fingerprints should be extended to other compounds and also to older trees.