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

Abstract

Abstract. We present the first investigation of the composition of dissolved organic matter (DOM) compared to total organic matter (TOM, consisting of DOM, < 0.45 µm and particulate organic matter 0.45 µm < POM < 500 µm) in throughfall, stemflow and forest floor leachate of common beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) H. Karst.) forests using solid-state 13 C 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 the two tree species.The 13 C NMR results, derived from 21 samples, point to pronounced differences in the composition of DOM and TOM in throughfall solution at the beech sites, with TOM exhibiting higher relative intensities for the alkyl C region, which represents aliphatic C from less decomposed organic material compared to DOM. Furthermore, TOM shows lower intensities for lignin-derived and aromatic C of the aryl C region resulting in lower aromaticity indices and a diminished degree of humification. Across the ecosystem compartments, differences in the structural composition of DOM and TOM under beech lessened in the following order: throughfall > stemflow ≈ forest floor leachate.In contrast to the broadleaved sites, differences between DOM and TOM in throughfall solution under spruce were less pronounced and spectra were, overall, dominated by the alkyl C region, representing aliphatic C. Explanations of the reported results might be substantiated in differences in tree species-specific structural effects, leaching characteristics or differences in the microbial community of the tree species' phyllosphere and cortisphere. However, the fact that throughfall DOM under beech showed the highest intensities of recalcitrant aromatic and phenolic C among all samples analysed likely points to a high allelopathic potential of beech trees negatively affecting other organisms and hence ecosystem processes and functions.

Dissolved organic matter characteristics of deciduous and coniferous forests with variable management: different at the source, aligned in the soil

“…This agrees with findings of Lorenz et al (2004), who reported higher concentrations of tannins in beech leaf litter than in pine needles. A higher share of phenolic carbon in beech than spruce solution samples from the same plots than this study was also found by Bischoff et al (2015), based on 13 C NMR analysis.…”

“…Dissolved organic matter (DOM) processing and transport is highly dynamic in forest ecosystems (Kaiser and Kalbitz, 2012) and plays an important role in the biogeochemical cycles of carbon and nutrients (Bolan et al, 2011;Kaiser and Kalbitz, 2012). The chemical composition of DOM strongly affects its role in the carbon and nutrient cycles of ecosystems (Bolan et al, 2011). The chemical composition, in turn, depends on the DOM source and its processing along the water flow path through ecosystems.…”

“…Both, sources and processing, affect DOM chemical composition . Biological DOM production and mineralization are important mechanisms regulating DOM dynamics in the environment (Benner, 2002;Bolan et al, 2011). Biodegradability of DOM is, in addition to other controls, driven by intrinsic characteristics like molecular structure, functional group content or size of the molecules (Marschner and Kalbitz, 2003).…”

A review of stemflow generation dynamics and stemflow‐environment interactions in forests and shrublands

“…How might this change with tree age and change in bark structure? NMR spectroscopy may prove useful to examine the chemical character of PM in stemflow [ Bischoff et al ., ]. The variety of plant surfaces is as vast as the number of tree species.…”

DOC Transport and Export in a Dynamic Tropical Catchment

“…DOC pools are denoted from S1 to S7. Although SOC (including litter leachate) near the riparian areas constitutes the main carbon pool in headwater tropical catchments, organic matter from throughfall (1-61 mg/L) and stemflow (7-482 mg/L; often stored and released from mosses, ferns, lichens, and bromeliads) may also contribute a significant DOC pulse during large rain events (Bischoff et al, 2015;da Costa et al, 2017;Van Stan & Stubbins, 2018) to the overall fluvial carbon budget.…”