Identification and allelochemical activity of phenolic compounds in extracts from the dominant plant species established in clear-cuts of Scots pine stands

Abstract

Dominant plant species established in the understory of clear-cuts may have a strong biochemical influence on pine regeneration process, with important consequences for reforestation management. We evaluated and compared the total phenolic content and the allelopathic activity of acqueous extracts from both roots and shoots of dominant plant species established in 1-yr-old and 2-yr-old clear-cuts of Scots pine (Pinus sylvestris L.) stands in Lituania. The highest total content of phenolic compounds was detected in the lingonberry (Vaccinium vitis-idaea L.) shoots from 1-yr-old and 2-yr-old clear-cuts, as well as in the common heather (Calluna vulgaris [L.[ Hull) shoots from 1-yr-old clear-cuts. High-performance liquid chromatography (HPLC) was used to identify and quantify the allelochemicals present in the active fraction to determine their possible role in allelopathy. The highest variety and content of phenolic compounds were observed in shoot extracts of the dominant species from both 1-yr-old and 2-yr-old clear-cuts. Scots pine seed germination and seedling growth were significantly and negatively correlated with ρ-coumaric acid and sinapic acid content, while Scots pine seedling growth was significantly and negatively correlated with ferulic, caffeic and hydroxycinnamic acids contents. The highest contents of these phenolic acids were determined in aqueous extracts of C. vulgaris from 1-yr-old clear-cuts and Rumex acetosella L. of 2-yr-old clear-cuts, which exerted a strong phytotoxicity on Scots pine seed germination. Moreover, morphometric parameters of Scots pine seedlings were most sensitive to aqueous extracts of V. vitis-idaea shoots from both 1-yr-old and 2-yr-old clear-cuts and R. acetosella shoots from 2-yr-old clear-cuts.