Förderkennzeichen: DFG FOR 995
The unique features of paddy soils favor large concentrations and fluxes of dissolved organic matter (DOM). Nevertheless, our knowledge about production and stabilization of DOM in paddy soils is scarce although this fraction of soil organic matter is important for greenhouse gas emission and carbon storage in soils. It is assumed that changing redox conditions are the key drivers of DOM dynamics in these soils. However, this hypothesis was not tested so far. The main objective of the project is to study effects of redox conditions on production and stabilization of DOM in paddy soils. Soils of a chronosequence of paddy soil evolution (50 to 1000 years) will be studied in direct comparison to non-paddy soils of the same age. In these soils, exposed to different redox conditions over different periods of times, DOM production and DOM removal from solution by mineralization, sorption and (co-)precipitation with Fe oxides/hydroxides will be determined in laboratory experiments at oxic and anoxic conditions. The use of 13C labeled DOM in column experiments allows for quantification of DOM removal from solution as a cumulative value of several processes but also for quantification of individual processes such as stabilization by binding to Fe oxides/hydroxides and incorporation into the microbial biomass. The results of our project will shed light on the processes in all soils affected by changing redox conditions.