Air-dried soils deliver reliable biodiversity data, new SOB4ES study shows
How soil samples are stored after collection may seem like a technical detail, but it plays an important role in how we measure life belowground. A new open-access study published in Soil Biology & Biochemistry brings reassuring news for soil researchers and monitoring programmes: air-drying soil samples preserves soil biodiversity information just as well as freezing.
Environmental DNA (eDNA) methods are increasingly used to assess soil biodiversity, from microbes to small soil animals. Traditionally, soil samples are frozen shortly after collection to prevent DNA degradation. While effective, freezing requires cold storage, specialised equipment, and careful transport — constraints that can limit sampling efforts across large or remote areas over longer time periods.
To test whether a simpler approach could work just as well, the researchers compared air-dried soils stored at room temperature with soils frozen at −20 °C. They analysed DNA from a wide range of soil organisms, including bacteria, fungi, micro-eukaryotes, nematodes, annelids, and micro-arthropods.
The study was carried out across 42 sites in the Swiss Central Plateau, covering forests, grasslands, arable land, orchards, wetlands and urban soils. Several land-use types were sampled along gradients of management intensity, allowing the team to assess whether storage effects differed under contrasting environmental conditions.
The results were remarkably consistent. Across all land uses and management intensities, air-dried and frozen soils showed comparable DNA abundance, diversity, and community composition for all organism groups studied. Crucially, the main drivers shaping soil biodiversity — such as land use and soil properties — were the same regardless of how the samples had been stored.
“From a monitoring perspective, this is very encouraging,” says Aline Frossard, from SOB4ES partner WSL and last author of the study. “Our results show that air-drying of soils does not compromise the quality of eDNA-based biodiversity assessments, even across very different land-use types. This opens up much more flexible and cost-effective options for large-scale soil biodiversity monitoring.”
By demonstrating that air-drying is a reliable short-term storage method, the study removes a major logistical barrier for soil biodiversity surveys. This is particularly relevant for international projects, long-term monitoring programmes, and initiatives aiming to harmonise sampling across biogeographical regions.
As efforts to better understand and protect soil biodiversity continue to grow, practical solutions like this help ensure that monitoring can be both scientifically robust and feasible at scale. Read the full study in Soil Biology and Biochemistry
