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Particulate(s) matter! - Importance of canopy-derived water-bound particulate matter in forest ecosystem nutrient cycling

Sebastian Bischoff1, Martin Schwarz2, Jan Siemens3, Lisa Thieme3, Wolfgang Wilcke2, Beate Michalzik1
1 Institute of Geography, Friedrich Schiller University Jena
2 Institute of Geography and Geoecology, Karlsruhe Institute of Technology
3 Institute for Crop Science and Resource Conservation, Rheinische Friedrich Wilhelms University Bonn

P 7.3 in Controls of dissolved organic matter fluxes in ecosystems

Poster Session 1 on Monday, 16:30-18:30

The forest canopy represents one of the most important ecological compartments of wooded ecosystems. It plays a key role with regard to the accumulation of atmospheric deposits as well as the input of nutrients and organic matter (OM) to forest soils. The quality of OM as an energy source and driver for biotic processes plays a crucial role for element cycling in ecosystems. However, the influence of plant species diversity and land use intensity on the amount and quality of OM and associated nutrients is still poorly understood. Throughfall (TF) provides easily decomposable C and N compounds, which probably act as promoters for mineralization and decomposition processes of OM in the forest floor, likely causing increased dissolved OM (DOM) fluxes from the forest floor into the mineral soil building up soil OM. While many investigations addressed the nature and dynamics of water-bound DOM fluxes in terrestrial ecosystems, only few investigated the dynamics and the character of canopy-derived water-bound particulate matter (PM; 0.45 μm < PM < 500 μm) and its role in the biogeochemical cycles of forest ecosystems. In the present study we hypothesized that canopy-derived PM contributes significantly to the input of OM to the forest floor and is controlled by forest management (e.g. stand age, tree species, canopy structure), as well as abiotic (e.g. climatic conditions) and biotic (e.g. pollen deposition, insect infestations) processes. Our study sites were located in the Hainich-Dün area (Thuringia, Central Germany), forming part of the German “Biodiversity Exploratories”, which were established in 2006 as a scientific platform for biodiversity research funded by the German Research Foundation (DFG SPP 1374 "Exploratories for Large-scale and Long-term Functional Biodiversity Research“; www.biodiversity-exploratories.de). TF samples were collected throughout the vegetation periods (April - November) of 2010, 2011 and 2012 in bi-weekly sampling intervals. Annual fluxes of dissolved organic C and dissolved N with TF over three years exhibited significantly higher fluxes under spruce than under beech. Fluxes of particulate organic C showed a high interannual variability in beech forests, likely caused by pollen release, peaking in up to 60% of total organic C in TF for 2011. Similar dynamics were observed for particulate N. We therefore conclude that PM fluxes need to be included in element budgeting of forest ecosystems.

Letzte Änderung 19.06.2014