Examining litter and soil characteristics impact on decomposer communities, detritivores and carbon accumulation in the Mediterranean area

Background and aim: Litter and soil characteristics influence the abundance and activities of decomposers and detritivores, thereby affecting C accumulation. The relationship between the chemical composition of soil organic matter and soil organisms is still unclear. The study aims to investigate how the quality and quantity of litter and soil organic matter influence C accumulation and the relationships between organic matter quality and bacteria, fungi and microarthropods in litter and soil. Materials and methods: Litters and soils from 24 sites were analysed for the abiotic (pH, water content, total C and N content and the chemical composition of soluble C: carbohydrate, alkyl, O-alkyl, aromatic and carboxyl groups) and the biotic characteristics (bacterial and fungal abundances, urease and β-glucosidase, microbial respiration, microarthropod community). Results: Litter had a high carbohydrate and low C contents, whereas soil had higher content of recalcitrant compounds (aromatic and carboxylic groups) and C. Whitin substrate types, higher C content was found in litter from shrubs and in soil under sclerophyllous evergreens. Bacterial abundances were lower in litter than in soil, whereas microbial respiration, enzymatic activities, microarthropod densities and predator abundances were higher in litter than in soil. Microbial abundances and activities were strongly related to total C and N concentrations in both litter and soil, while the microarthropod community was positively correlated with soluble C recalcitrant compounds in soil. Conclusions: Soils showed a high capacity for C accumulation due to the high content of recalcitrant compounds. In soil, the microarthropod community, more than bacteria and fungi, was positively correlated with the quality of organic matter.