Production and stabilization of dissolved organic matter in paddy soils depending on redox conditions

水稻土具有溶解性有机质（DOM）高浓度、高通量的特点。然而，我们对水稻土中DOM的产生和稳定性的了解很少，尽管这部分土壤有机质对温室气体排放和土壤碳储存很重要。据推测，不断变化的氧化还原条件是这些土壤中DOM动态的关键驱动因素。然而，这一假设迄今尚未得到检验。本项目的主要目的是研究氧化还原条件对水稻土中DOM的产生和稳定性的影响。将研究水稻土演变时序（50至1000年）的土壤，与同龄的非水稻土进行直接比较。在这些土壤中，暴露于不同的氧化还原条件下，在不同的时间段，DOM生产和DOM去除从溶液中的矿化，吸附和（共）沉淀与铁氧化物/氢氧化物将在实验室实验中确定在好氧和缺氧条件。在柱实验中使用13 C标记的DOM允许从溶液中去除DOM的量化作为几个过程的累积值，但也用于量化单个过程，例如通过结合到Fe氧化物/氢氧化物和掺入到微生物生物质中的稳定化。我们项目的结果将揭示所有土壤中受氧化还原条件变化影响的过程。

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.