Peatlands store about 30% of the global soil carbon (C) stock. The decomposition of peat C in these systems depends on environmental parameters – such as water table levels and corresponding availability of electron acceptors for microbial respiration. Due to the latter, potential peat decomposition depends also on whether the material is initially oxidized or reduced prior to decomposition experiments.

Recent studies revealed the importance of silicon (Si) for peat decomposition. High amounts of biogenic Si were found in peatlands, in particular in minerotrophic fens, and the importance of Si for graminoids and decomposability of respective litter has been widely discussed. Furthermore, the availability of Si was reported to influence the binding of phosphorus (P) to iron (Fe) and thereby the conditions under which decomposition proceeds. Yet the influence of Si on greenhouse gas production in peat under different initial redox conditions is largely unknown. Therefore, we intended to test the effect of Si on greenhouse gas production under different initial electron acceptor availabilities for microbial respiration, such as the availability of ferric Fe.

We conducted two incubation experiments with initially oxidized and reduced peat organic matter (OM). We hypothesized that Si can mobilize P from Fe minerals, which increases microbial activity, and leads to higher production rates of carbon dioxide (CO₂) and methane (CH₄). Using the two different materials, we studied how initial redox conditions would modify effects of Si. As the predominant form of Fe as either ferric Fe-(oxy)hydroxides or as ferrous Fe minerals (sulfides, carbonates) is important for interaction with Si, we further hypothesized that Si effects should be stronger in initially oxidized peat in presence of ferric Fe, compared to initially reduced peat with ferrous Fe only.

For incubation experiments using formerly oxidized material the Si addition increased P concentrations in the pore water, and more CO₂ was produced. The onset of methanogenesis was much stronger with than without addition of Si, indicating a more rapid depletion of electron acceptors by faster rates of respiration. We explain this by more P being available stimulating microbial activity, and also by a direct effect of Si on microbial activity and methanogenesis. The incubation of formerly reduced OM did not show any effects of Si on respiration processes, presumably due to the absence of ferric Fe phases.

In conclusion, there was a clear difference in the effect of Si addition on decomposition of formerly oxidized compared to long term reduced OM, with only oxidized peat OM or peat with ferric Fe phases present showing clear Si effects. Consequently, redox conditions and availability of ferric Fe are a main control for Si effects on OM decomposition and nutrient availability. Little effects of Si can be expected under permanently reducing conditions and in absence of ferric Fe phases.

泥炭地存储了全球土壤碳（C）总量的30％。在这些系统中，泥炭C的分解取决于环境参数，例如地下水位和相应的微生物呼吸电子受体的可用性。由于后者，潜在的泥炭分解还取决于材料在分解实验之前是先被氧化还是被还原。

最近的研究揭示了硅（Si）对泥炭分解的重要性。在泥炭地，特别是在矿化营养区发现了大量的生物硅，并且硅对类动物粪便和各个垫料的可分解性的重要性已得到广泛讨论。此外，据报道，Si的可用性影响磷（P）与铁（Fe）的结合，从而影响分解进行的条件。然而，在不同的初始氧化还原条件下，硅对泥炭中温室气体产生的影响尚不清楚。因此，我们打算测试在微生物呼吸的不同初始电子受体利用率（例如三价铁的利用率）下，硅对温室气体生产的影响。

我们对最初氧化和还原的泥炭有机质（OM）进行了两个培养实验。我们假设Si可以从Fe矿物中迁移P，从而增加微生物活性，并导致更高的二氧化碳（CO ₂）和甲烷（CH ₄）生产率。使用两种不同的材料，我们研究了初始氧化还原条件如何改变Si的影响。由于Fe的主要形式为Fe-（羟基）氢氧化铁或Fe铁矿物质（硫化物，碳酸盐）对于与Si相互作用很重要，因此我们进一步假设在Fe的存在下，最初氧化的泥炭中Si的作用应更强与最初仅使用铁亚铁减少的泥炭相比。

对于使用以前被氧化的物质进行的温育实验，添加Si可增加孔隙水中P的浓度，并产生更多的CO ₂。与不添加Si相比，甲烷生成的发生要强得多，这表明通过更快的呼吸速率可以更快地耗尽电子受体。我们通过更多的P可以刺激微生物的活性，以及​​Si对微生物活性和甲烷生成的直接作用来解释这一点。以前还原的OM的孵育未显示Si对呼吸过程有任何影响，这可能是由于不存在三价铁相。

总之，与长期还原的OM相比，添加Si对以前被氧化的OM分解的影响存在明显差异，仅氧化的泥炭OM或具有铁相的泥炭表现出明显的Si效应。因此，氧化还原条件和三价铁的有效性是控制硅对OM分解和养分有效性的主要控制因素。在永久还原的条件下，在没有铁的铁相的情况下，Si的影响很小。