Swiss soil samples storage comparison Dried vs Frozen

Soil biodiversity monitoring requires standardized and practical sample storage methods, particularly for large-scale surveys. However, the impact of soil storage conditions on DNA-based assessments of microbial and faunal communities remains underexplored across different land-use types and management intensities. Here, we assessed whether air-drying of soils at room temperature alters microbial (prokaryotes, fungi, micro-eukaryotes) and faunal (nematodes, annelids, micro-arthropods) abundance and diversity compared to freezing at –20?°C through quantitative polymerase chain reaction (qPCR) and soil DNA metabarcoding. To do so, we sampled topsoil (0 – 10 cm) from 42 sites in northern Switzerland spanning forests, grasslands, arable lands, orchards, wetlands, and urban areas, with forests, grasslands and arable lands varying in management intensities. Across land-use type and management intensity, air-dried and frozen soils yielded comparable gene abundances, alpha-diversity, and community structures for all microbial and faunal groups. Moreover, land-use type and soil physicochemical variables consistently shaped microbial and faunal community structures regardless of the soil preservation method. These findings demonstrate that air-drying is a cost-effective and reliable method for preserving soil samples in large-scale biodiversity monitoring without compromising data quality.