EGU2020-15883, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-15883
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Chemical composition and colloidal properties of dissolved organic matter in Norway spruce forest stands of different ages

Viktoriia Meklesh1,2, Luigi Gentile3, Ulf Olsson2, Anders Tunlid4, and Per Persson1,4
Viktoriia Meklesh et al.
  • 1Centre for Environmental and Climate Research (CEC), Lund University, Ecology Building, Sölvegatan 37, SE-223 62 Lund, Sweden
  • 2Department of Chemistry, Physical Chemistry Division, Lund University, Naturvetarvägen 14, 223 62 Lund, Sweden
  • 3Department of Chemistry, University of Bari Aldo Moro, Via Orabona 4, I-70126, Bari, Italy
  • 4Department of Biology, Microbial Ecology Group, Lund University, Ecology Building, SE-223 62 Lund, Sweden

     Dissolved organic matter (DOM) is the most mobile and actively cycling fraction of soil carbon and acts as a carrier of nutrients and contaminants. It is consumed by microbes, photodegraded, or adsorbed in soils and sediments on its way to the ocean. Despite intensive research in the last two decades, the formation and fate of DOM in soils and its response to changes in land use and climate are poorly understood [1-3]. The changes in temperature and chemical composition of soils affect substantially the rates of microbial decomposition. It has previously been observed that afforestation had a positive effect on carbon stocks approximately 3 decades after land-use change [4]. The aim of this study was to identify the role of afforestation on the chemical composition and colloidal nature of DOM. We compared water extractable DOM from an organic horizon in three differently aged (35-, 61-, 90-years-old) Norway spruce stands growing in the same Tönnersjöheden area located at Simlångsdalen, south-west Sweden . Arable fields that were adjacent to each of these three forests served as control DOM samples and represented the soil material before afforestation. Chemical composition of DOM was inferred from 13C solid-state nuclear magnetic resonance (NMR), high-resolution 1H NMR, infrared spectroscopy (DRIFT) and elemental analysis measurements. Colloidal properties of DOM were investigated using small-angle X-ray and dynamic light scattering methods together with electrophoretic mobility measurements. The dialysis experiment was additionally performed in order to investigate the high molecular fraction of DOM.

     Elemental analysis revealed an increase in the ratio between total organic C and total N with forest age and no differences between three field DOM extracts. 1H and 13C NMR results showed that both field and forest DOM extracts were dominated by carbohydrates and also contained carboxylic and aliphatic compounds. The aromatic structures were not detected using NMR. However, some features of aromatics and phenolics were detected in IR spectra, especially in forest cold DOM. Scattering data showed that field and forest DOM contained locally stable colloidal aggregates of ca. 100 nm in radius. The structures of these aggregates are consistent with a combination of globular and cluster-like colloids. Field DOM contained slightly higher fraction of clusters than forest DOM. According to the dialysis experiment the half of DOM was presented in high molecular weight fraction (> 12-14 kDa). Overall, our data suggest that DOM extracted from forest and field organic soils had similar chemical and colloidal properties. The relative composition was dictated more by temperature at which DOM was extracted.

  1. J. Lehmann, M. Kleber, Nature. 528, 60–68 (2015).
  2. M. W. I. Schmidt et al., Nature. 478 (2011), pp. 49–56.
  3. K. Kalbitz, S. Solinger, J.-H. Park, B. Michalzik, E. Matzner, Soil Sci. 165, 277–304 (2000).
  4. T. G. Bárcena et al., Glob. Chang. Biol. 20, 2393–2405 (2014).

How to cite: Meklesh, V., Gentile, L., Olsson, U., Tunlid, A., and Persson, P.: Chemical composition and colloidal properties of dissolved organic matter in Norway spruce forest stands of different ages, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15883, https://doi.org/10.5194/egusphere-egu2020-15883, 2020

Display materials

Display file