PHENOLIC SUBSTANCES IN A HUMUSPODZOL PROFILE AND THEIR IMPACT ON SOME WOODLAND HERBS AT LOW NUTRIENT SUPPLY

Abstract

Twelve years after clearance of a Picea abies stand, the spectrum of water-soluble phenolic acids in the soil still resembled that of an adjacent, undamaged stand. Ferulic and p-coumaric acid were the predominant phenolic compounds. Apparently, the spectrum of low molecular phenolics in the soil layers is affected by the original litter material over a long period. The concentrations of water-soluble acids was highest in the A0-horizon. A comparison between the sites revealed that concentrations in the clearing were reduced with more than 50% compared to the undamaged stand. The significance of the phenolic acids for plant growth was investigated for two herbaceous woodland (-clearing) species, Senecio sylvaticus and Chamaenerion angustifolium. Both species were tested for their sensitivity to phenolic acids in dependence of nutrient supply under greenhouse conditions. Severe growth reduction occurred at high phenolic acid concentrations (10–3 M). Plants that were restricted in growth by a low nutrient supply, were less affected by the intermediate phenolic acid concentrations of 10–5 and 10–4 M than plants grown at high nutrient supply. The results are discussed in view of vegetation succession on woodland clearings.