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Media type:
E-Article
Title:
Dissolved organic matter characteristics of deciduous and coniferous forests with variable management: different at the source, aligned in the soil
Published in:
Biogeosciences, 16 (2019) 7, Seite 1411-1432
Language:
English
DOI:
10.5194/bg-16-1411-2019
ISSN:
1726-4189
Origination:
Footnote:
Description:
Abstract. Dissolved organic matter (DOM) is part of the biogeochemical cycles of carbonand nutrients, carries pollutants and drives soil formation. The DOMconcentration and properties along the water flow path through forestecosystems depend on its sampling location and transformation processes. Toimprove our understanding of the effects of forest management, especiallytree species selection and management intensity, on DOM concentrations andproperties of samples from different ecosystem fluxes, we studiedthroughfall, stemflow, litter leachate and mineral soil solution at 26 forestsites in the three regions of the German Biodiversity Exploratories. Wecovered forest stands with three management categories (coniferous, deciduousage class and unmanaged beech forests). In water samples from these forests,we monitored DOC concentrations over 4 years and characterized the qualityof DOM with UV-vis absorption, fluorescence spectroscopy combined withparallel factor analysis (PARAFAC) and Fourier transform ion cyclotronresonance mass spectrometry (FT-ICR-MS). Additionally, we performedincubation-based biodegradation assays. Multivariate statistics revealedstrong significant effects of ecosystem fluxes and smaller effects of maintree species on DOM quality. Coniferous forests differed from deciduousforests by showing larger DOC concentrations, more lignin- and protein-likemolecules, and fewer tannin-like molecules in throughfall, stemflow, andlitter leachate. Cluster analysis of FT-ICR-MS data indicated that DOMcompositions, which varied in aboveground samples depending on tree species,become aligned in mineral soil. This alignment of DOM composition along thewater flow path in mineral soil is likely caused by microbial production andconsumption of DOM in combination with its interaction with the solid phase,producing a characteristic pattern of organic compounds in forest mineralsoils. We found similarly pronounced effects of ecosystem fluxes on thebiodegradability of DOM, but surprisingly no differences between deciduousand coniferous forests. Forest management intensity, mainly determined bybiomass extraction, contribution of species, which are not site-adapted, anddeadwood mass, did not influence DOC concentrations, DOM composition andproperties significantly.