The transformation of organic matter (OM) occluded in earthworm casts during the casts' lifetime may affect its composition and accumulation in stabilised OM pools. We collected casts produced by the anecic earthworm Amynthas khami in a tropical woodland of Northern Vietnam presenting different degradation stages. The aim of this study was to assess (1) the biogeochemical properties of OM in earthworm casts compared to control aggregates from the surrounding soil, and (2) the fate of occluded OM during cast ageing. We analysed intact casts and their density fractions at five ageing stages for organic carbon (OC) and nitrogen (N) content, OM chemical composition by analytical pyrolysis, and OM stability by Rock-Eval thermal analysis. Compared to control aggregates, fresh casts had higher OC values (5.3 vs. 2.6%) and increased OC in all density fractions. Cast OM had more lignin (1.1 vs.<0.1%), similar polysaccharide and N-compound contribution and was more thermally labile than those of control aggregates. Changes in OM composition and content during cast ageing appeared at the end of the casts’ lifetime, when they were broken into smaller aggregates (10–13 mm). At these latest stages, OC content decreased (1.5-fold); along with OM in macro-aggregates (2.2-fold) and microaggregates (6.8-fold). Reduced mineral-associated OC was also recorded (1.3-fold). During ageing, the percentage of lignin decreased (5.5-fold) while the thermal stability of OM increased. The distinct OM properties of casts were maintained throughout the cast ageing process, and most properties of the oldest casts were significantly different from the control aggregates. Since OM is retained in cast fragments after they disintegrate, the earthworm influence on soil organic matter stabilisation processes appears to persist beyond the lifespan of casts.

worm的生长期中，cast的有机物（OM）的转化可能会影响其组成和在稳定的OM池中的积累。我们收集了由an引起的粪便Amynthas khami在越南北部的热带林地中呈现出不同的退化阶段。这项研究的目的是评估（1）与周围土壤的对照聚集体相比，worm铸模中OM的生物地球化学特性，以及（2）铸模老化过程中被封闭的OM的命运。我们分析了五个时效阶段的完整铸件及其密度分数，其中包括有机碳（OC）和氮（N）含量，通过分析热解的OM化学成分以及通过Rock-Eval热分析的OM稳定性。与对照骨料相比，新鲜铸坯的OC值更高（5.3比2.6％），并且所有密度部分的OC均增加。Cast OM的木质素含量更高（1.1比<0.1％），相似的多糖和N化合物的贡献，并且比对照聚集体的热不稳定。铸件时效过程中，OM成分和含量的变化出现在铸件使用寿命的尽头，当它们破碎成较小的骨料（10-13毫米）时。在这些最新阶段，OC含量下降了（1.5倍）。以及大型集合体（2.2倍）和微型集合体（6.8倍）中的OM。还记录到矿物相关的OC减少（1.3倍）。在老化过程中，木质素的百分比降低（5.5倍），而OM的热稳定性提高。在整个铸件时效过程中，铸件具有独特的OM性能，最老的铸件的大多数性能与对照骨料显着不同。由于OM在分解后会保留在铸模碎片中，