Biological soil crusts (biocrusts) play an important role in the biogeochemical C-, N- and P-cycles but there is limited knowledge about their effect on the composition and stability of organic matter (OM) in soil. In pine and beech dominated temperate forests, the different compartments of biocrust, crust-adhering soil and crust-free soil were analysed by pyrolysis field ionization mass spectrometry (Py-FIMS) and C K-edge X-ray absorption near edge structure (XANES) spectroscopy. Phototrophic biocrust communities had been determined morphologically. Predominant tree species affected OM composition and stability but an overriding effect of biocrust organisms was observed. In biocrusts, the OM mineralization potential was high due to a high carbohydrate/ketone ratio and a high proportion of the fatty acid C_22:0. A high proportion of free fatty acids in combination with a high carbohydrate proportion was identified as a relative marker for biocrusts and additional high proportions of lignin dimers were specific for samples under pine. In biocrust under pine, OM in soil compartments was characterized by large proportions of long-chain aliphatics from plant cuticular material. In A-horizon substrate under beech, OM compound classes were not affected by phototrophic species richness, suggesting functional redundancy of these biocrust organisms with regard to OM composition. In contrast to A-horizon substrate, OM in C-horizon substrate was characterized by a higher proportion of easily decomposable material. Under pine, forest management intensity (SMI) affected OM by stand age and density due to effects on phototrophic biocrust species. We conclude that compartment, vegetation, horizon substrate and SMI affected OM composition and stability, and biocrusts hence contributed to soil OM diversity in forest ecosystems.

生物土壤结皮（生物结皮）在生物地球化学 C-、N-和 P-循环中起着重要作用，但关于它们对土壤中有机质 (OM) 组成和稳定性的影响的知识有限。在以松树和山毛榉为主的温带森林中，通过热解场电离质谱 (Py-FIMS) 和 C K边缘 X 射线吸收近边缘结构 (XANES ) 分析了生物结皮、附着结皮土壤和无结皮土壤的不同部分) 光谱学。光养生物结皮群落已在形态上确定。主要树种影响 OM 组成和稳定性，但观察到生物结皮生物的压倒性影响。在生物地壳中，由于高碳水化合物/酮比和高比例的脂肪酸 C，OM 矿化潜力很高_22:0. 高比例的游离脂肪酸与高比例的碳水化合物被确定为生物结皮的相对标志物，另外高比例的木质素二聚体对松树下的样品具有特异性。在松树下的生物结皮中，土壤隔室中的 OM 以来自植物表皮材料的大比例长链脂肪族化合物为特征。在山毛榉下的 A-horizo​​n 基质中，OM 化合物类别不受光养物种丰富度的影响，表明这些生物外壳生物在 OM 组成方面具有功能冗余。与 A-horizo​​n 底物相比，C-horizo​​n 底物中的 OM 的特征在于更高比例的易分解材料。在松树下，由于对光养生物结皮物种的影响，森林管理强度 (SMI) 通过林龄和密度影响 OM。