Thank you for helping us to document the biodiversity of life in soils. There are a number of aspects to consider when taking your samples and we hope this guide can help to inform your decisions on a sampling strategy.
Research Goals and Target Species
Before selecting a site, define your research objectives and identify your target species or communities. Different environments will yield different eDNA due to variations in species composition and abundance.
Time of the Year
Soil sampling can be done any time of the year and the communities present will vary depending on whether you assess them in the spring, summer, and fall. A thorough sampling regime will look at the communities that are present throughout the year, not just at a single time-point. Consider the life cycle of the target species and the best time to detect eDNA. For example, if the target species breed in the spring, sampling during or after this period may yield better results.
Our kits make use of plastic soil collection syringes, so they are not able to sample during periods of cold weather where the ground may be frozen. Consider taking your first samples as soon as the ground thaws.
Accessibility and Permission
Ensure that the sites are accessible and that you have the necessary permissions to collect samples, especially if the land is privately owned or protected. Logistics and legal access can impact your sampling plan significantly.
Habitat
There is not a specific type of habitat that we are most interested in. All habitat types can produce interesting results! The type of habitat that you sample from should be based on your individual sampling goals and objectives. Think about the primary reasons you are interested in looking at the biodiversity of your soils. For instance, if you are most interested in looking for an eDNA signature of a forest floor-dwelling salamander, you'll want to sample from forest soils rather than from agricultural fields.
Some common goals of sampling include assessing the health of the environment, assessing the biodiversity that is present in a location, or to look for red-listed or invasive species. Your specific goals may lead you to bias your sampling efforts towards one habitat type vs. another.
Sampling Bias
To reduce sampling bias and ensure representative data, select multiple sites within the habitat of interest. Consider random, systematic, or stratified sampling designs to cover the area effectively. For rare or patchily distributed species, targeted sampling may be necessary.
Geographical Spread and Replication
If possible, select sites that are geographically spread to gain a more comprehensive understanding of species distribution. Multiple samples from each site (replicates) will help ensure the reliability of your results.
Remember, thorough planning and careful site selection are fundamental for effective eDNA sampling. Each of the points above can significantly influence the outcomes of your sampling. Always document the site selection process, as this is important information for the interpretation of your results and for other researchers who may follow up on your work.