Evolution of phenolic patterns in plants and associated litters and humus of a mountain forest ecosystem

The pattern of phenolic polymers (tannins) and monomers (phenolic acids, flavonoids) was followed from living organs (leaves and roots) of Picea abies (L.) Karst and Vaccinium myrtillus (L.) to litter types and humus, in two stands (1630 and 1860 m) of a mountain forest of Northen Alps (France). Quantitative and qualitative criteria were found to characterize species: abundance of tannins in bilberry; and, presence of p-hydroxyacetophenone a specific (and variable) metabolite in spruce needles. Compared to green foliage, an important loss of monomeric compounds in brown foliage was observed, when tanning activity greatly increased. As biodegradation proceeded the amounts of the degradation intermediates (protocatechuic, vanillic acids) increased in litters, and the influence of phenol-rich plants, such as bilberry, on organic layers was expressed by higher amounts of tanning activity and phenolic acids under bilberry cover. Because of its specificity and abundance, special attention might be given to p-hydroxyacetophenone in spruce forest floor. Control of phenolic compounds dynamics by their structure was equally emphasized.