Phenolic substances in forest leaf litter and their impact on plant growth in forest vegetations

Abstract

The role of phenolic secondary substances released from decaying plant litter and entering the forest soil system is discussed. Low molecular-weight phenolic acids have been found to leach in high amounts from various types of forest leaf litter. Different leaching patterns were established between litter from coniferous trees and litter from deciduous trees. An overview is given about the physiological impact of phenolic acids on plant development. By affecting ectomycorrhizal fungi, phenolics may influence the establishment and growth of tree seedlings. Polymeric phenols in forest leaf litter, i.e., hydrolyzable and condensed tannins, have a large influence on nutrient cycling in forests and thereby on the growth conditions of plants. They play a decisive role in the development of the humus profile. In this respect, two distinctive forms of humus formation, i.e., mor and mull humus type, are discussed. The allelopathic potential of species by the action of low molecular-weight phenolic acids, may be influenced by the humus form prevailing under the vegetation. Finally, the implications of monomeric and polymeric phenols for vegetation processes in forests are discussed.