Tree species effects on the release of dissolved organic carbon and nitrogen from decomposing logs

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The release of dissolved organic matter (DOM) from decomposing logs might be a significant contribution to their mass loss and an important C input to the soil underneath the logs. Here we will contribute to the BeLongDead initiative by investigating concentrations, properties and fluxes of DOM as influenced by tree species, forest management, climatic conditions and time of log exposure. Furthermore we will follow the fluxes of mineral N and establish DOM and N budgets of the logs by comparing throughfall fluxes and fluxes with runoff from the logs. The runoff water from the logs will be collected periodically at selected sites using small gutters placed underneath the logs. In total, runoff water from 120 logs will be sampled. All 13 tree species will be studied in the Hainich sites, while at Schorfheide and Schwäbische Alb sites only beech, spruce and oak logs are compared. The elemental composition of DOM (C, N), its spectroscopic properties and 13C signatures will be determined. In addition, the mineralization of DOM to CO2 by soil organisms is investigated in laboratory incubations. In cooperation with the other members of we will be able to achieve ground braking progress on the processes driving the decomposition of logs, the related DOM release and N turnover as influenced by tree species, wood properties, climate, insect and fungi invasion.