Resolving the conundrum of highly stable organic matter in Plaggic Anthrosols

提出的研究项目旨在阐明为什么高度稳定的有机物质（OM）持续存在于可塑性人类。耕耕人类的形成与以前的耕地管理技术——耕耕农业有关。普拉根农业可能始于公元10世纪的欧洲西北部。为了提高营养贫乏和酸性沙质土壤（例如灰壤）的肥力，从石南和草地上割下的草皮用于马厩的动物垫料，部分与用于堆肥的家庭残留物混合，然后用于耕地。秸秆或森林地面材料也可用作菌丝体材料。几个世纪以来，贫瘠的农业导致了贫瘠土地的形成。尽管真菌农业在100多年前就已经终止了，但该地区的土壤有机质（SOM）仍然很丰富。这些大的有机碳储量说明了土壤有机质的高稳定性，可以作为研究沙质耕地土壤有机质长期稳定的模型系统。我们的研究将阐明为什么沙质可耕地土壤的SOM水平比邻近的没有白菌素历史的沙质可耕地土壤高。我们将研究大块土壤中有机碳的含量和储量以及土壤组分中SOM的组成，特别是在有机-矿物组合中。我们将研究顽固性植物材料如草料、木炭或矿物相关OM对稳定SOM的作用。将特别注意铁（氢）氧化物和层状硅酸盐在形成稳定的SOM中的作用。通过培养实验对SOM的长期矿化过程进行调查，将允许分析SOM在易变人类中的稳定性。我们将首次模拟历史上菌素的修正，将(i)燕麦秸秆凋落物、（ii）橡树凋落物和（iii）石南花凋落物与粪便结合使用，将沙质可耕地土壤转化为可耕土壤材料。在孵育期间，将测定释放的二氧化碳的14C含量，以澄清可耕人类土壤中的有机质是否比邻近耕地土壤中的有机质更稳定，以及这是否与特定的有机质组分（例如，与矿物相关的有机质）有关。通过这种方法，我们将有助于理解为什么高度稳定的有机质在易变人类中持续存在，并阐明有机质稳定的相关机制。利用这些数据，将有可能推导出可塑人类体内OM储存的概念模型，这可能对进一步的土壤管理产生影响，以改善沙质土壤中的碳封存。

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.