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

水稻土的独特特征有利于土壤中溶解有机质（DOM）的高浓度和高通量。然而，尽管这部分土壤有机质对土壤温室气体排放和碳储存很重要，但我们对水稻土中DOM的产生和稳定的了解很少。我们认为，改变氧化还原条件是这些土壤中DOM动态的关键驱动因素。然而，到目前为止，这一假设还没有得到验证。该项目的主要目的是研究氧化还原条件对水稻土DOM生成和稳定的影响。水稻土演化时间序列（50至1000年）的土壤将与相同年龄的非水稻土进行直接比较。在这些土壤中，在不同的时间暴露于不同的氧化还原条件下，DOM的产生和DOM通过矿化、吸附和与铁氧化物/氢氧化物（共）沉淀从溶液中去除将在有氧和无氧条件下进行实验室实验。在柱实验中使用13C标记的DOM，可以将DOM从溶液中去除作为几个过程的累积值进行量化，也可以对单个过程进行量化，例如通过与铁氧化物/氢氧化物结合和融入微生物生物量进行稳定。我们项目的结果将阐明受氧化还原条件变化影响的所有土壤中的过程。

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.