Properties of dissolved and total organic matter in throughfall, stemflow and forest floor leachate of central European forests

[摘要] We present the first investigation of the composition of dissolved organicmatter (DOM) compared to total organic matter (TOM, consisting of DOM, < 0.45 μm and particulate organic matter 0.45 μm < POM < 500 μm) inthroughfall, stemflow and forest floor leachate of common beech(Fagus sylvatica L.) and Norway spruce (Picea abies (L.)H. Karst.) forests using solid-state ¹³C nuclear magnetic resonance(NMR) spectroscopy. We hypothesized that the composition and properties of organic matter(OM) in forest ecosystem water samples differ between DOM and TOM and between thetwo tree species.

The ¹³C NMR results, derived from 21 samples, point to pronounceddifferences in the composition of DOM and TOM in throughfall solution at thebeech sites, with TOM exhibiting higher relative intensities for the alkyl Cregion, which represents aliphatic C from less decomposed organic materialcompared to DOM. Furthermore, TOM shows lower intensities for lignin-derivedand aromatic C of the aryl C region resulting in lower aromaticity indicesand a diminished degree of humification. Across the ecosystem compartments,differences in the structural composition of DOM and TOM under beech lessenedin the following order: throughfall > stemflow ≈ forest floor leachate.

In contrast to the broadleaved sites, differences between DOM and TOM inthroughfall solution under spruce were less pronounced and spectrawere, overall, dominated by the alkyl C region, representing aliphatic C.Explanations of the reported results might be substantiated in differences intree species-specific structural effects, leaching characteristics ordifferences in the microbial community of the tree species' phyllosphere andcortisphere. However, the fact that throughfall DOM under beech showed thehighest intensities of recalcitrant aromatic and phenolic C among all samplesanalysed likely points to a high allelopathic potential of beech treesnegatively affecting other organisms and hence ecosystem processes andfunctions.

[学科分类] 地球化学与岩石