Resolving the conundrum of highly stable organic matter in Plaggic Anthrosols

拟议的研究项目旨在阐明为什么高度稳定的有机质（OM）持续存在于腐殖人为土中。残积人为土的形成与以前的耕地管理技术--残积农业有关。瘟疫农业可能始于公元世纪的欧洲西北部。为了提高养分贫乏和酸性桑迪土壤的肥力（例如，从石南和草地上割下的草皮，用作马厩的动物垫料，部分与用于堆肥的家庭残留物混合，随后施用于耕地。秸秆残留物或森林地面材料也被用作plaggen材料。几个世纪以来，残遗农业导致了残遗地平线的形成。尽管100多年前残遗农业已经结束，但残遗层仍然富含土壤有机质。这些大的有机碳（OC）股票说明这些土壤中的有机质的高稳定性，这可能是用来作为模型系统，以了解长期OC稳定在桑迪耕地土壤。我们的建议将阐明为什么桑迪腐殖人为土有较高的有机质水平相比，邻近的桑迪耕地土壤没有腐殖历史。我们将调查的内容和库存的有机碳在散装土壤和有机质组成的土壤组分，特别是在有机无机协会。我们将研究土壤、木炭或矿物质相关的有机质对稳定有机质的作用。将特别注意铁（氢）氧化物和层状硅酸盐的作用，形成稳定的SOM。调查长期矿化过程中的有机质的培养实验将允许分析有机质的稳定性在沼泽人为土。首次，我们将模拟历史plaggen修正案的应用凋落物从（一）燕麦秸秆，（二）橡树，（三）13 C标记的石南花凋落物与排泄物相结合，转换成plaggic土壤材料的桑迪耕地土壤。在培养过程中，将测定释放的CO2的14 C含量，以澄清腐殖人为土中的OM是否比邻近的可耕地土壤中的OM更稳定，以及这是否与特定的OM组分有关（例如，矿物相关的OM）。通过这种方法，我们将能够有助于理解为什么高度稳定的有机质持续存在于沼泽人为土，并阐明有机质稳定化的相关机制。利用这些数据，将有可能得出一个概念模型，有机质存储在腐殖人为土，这可能会有影响，进一步的土壤管理，以提高固碳桑迪土壤。

The proposed research project aims to elucidate why highly stable organic matter (OM) persists in Plaggic Anthrosols. The formation of Plaggic Anthrosols is linked with a former technique of arable land management - the plaggen agriculture. Plaggen agriculture probably started in the 10th century A.D. in NW Europe. To improve the fertility of nutrient-poor and acidic sandy soils (e.g., Podzols), sods from heather and grassland were cut, used for animal bedding in stables, partly mixed with household residues used for composting and subsequently applied to arable fields. Straw residues or forest floor materials were also used as plaggen material. Over centuries plaggen agriculture led to the formation of a plaggic horizon. The plaggic horizon is still enriched in soil organic matter (SOM), even though plaggen agriculture was terminated more than 100 years ago. These large organic carbon (OC) stocks illustrate the high stability of SOM in these soils, which might be used as model systems to understand long-term OC stabilization in sandy arable soils. Our proposal will elucidate why sandy Plaggic Anthrosols have higher SOM levels compared to adjacent sandy arable soils without plaggen history. We will investigate contents and stocks of OC in the bulk soil and SOM composition in soil fractions, particularly in organo-mineral associations. We will study the contribution of recalcitrant plant materials of sods, charcoal or the role of mineral-associated OM to stable SOM. Special attention will be paid to the role of Fe(hydr)oxides and phyllosilicates for the formation of stable SOM. Investigations of long-term mineralization processes of SOM by an incubation experiment will allow to analyse SOM stability in Plaggic Anthrosols. For the first time, we will simulate historic plaggen amendment by application of litter from (i) oat straw, (ii) oak, and (iii) 13C labeled litter from heather in combination with excrements to convert sandy arable soils into plaggic soil material. During incubation, the 14C content of the released CO2 will be determined to clarify if OM in Plaggic Anthrosols is more stable than in adjacent arable soils and if this is related to a specific OM fraction (e.g., mineral-associated OM). With this approach, we will be able to contribute to the understanding why highly stable OM persists in Plaggic Anthrosols and to elucidate the relevant mechanisms of OM stabilization. Using these data it will be possible to derive a conceptual model for OM storage in Plaggic Anthrosols, which may have implications for further soil management to improve carbon sequestration in sandy soils.