Seasonal variations in the chemical composition of dissolved organicmatter in organic forest floor layer leachates of old-growth Scots pine(Pinus sylvestris L.) and European beech (Fagus sylvatica L.) stands innortheastern Bavaria, Germany

摘要

Organic matter dissolved in the percolation water of forest soils contributes largely to element cycling and transport of natural and anthropogenic compounds. The way and extent to which these processes are affected depends on the amount and the chemical composition of soluble organic matter. Because the amount of soluble organic matter varies seasonally with changes in the microbial activity in soil, it seems reasonable to assume that there may be also seasonal changes in the chemical composition of dissolved organic matter. We examined dissolved organic matter in the seepage waters of organic forest floor layers over a 27-month period (1997-1999) in two forest ecosystems, a 160-year-old Scots pine (Pinus sylvestris L.) stand and a 90-year-old European beech (Fagus sylvatica L.) forest. The forest floor leachates were analysed for bulk dissolved organic C, C in hydrophilic and hydrophobic dissolved organic matter fractions, lignin-derived phenols (CuO oxidation), hydrolysable neutral carbohydrates and uronic acids, hydrolysable amino sugars, and stable carbon isotope composition. In addition, we studied the samples by use of liquid-state C-13-nuclear magnetic resonance (NMR) spectroscopy.