Identifying the sources of sediment using plant-based eDNA – a proof of principle analysis

Understanding sediment origins is crucial for effective catchment management, especially given the strong influence of vegetation on geomorphological processes. This study presents a proof of principle analysis investigating plant-based environmental DNA (eDNA) as a tool for tracing sediment sources. Two contrasting catchments were selected: a lowland agricultural area with rotating crop cycles and a high mountain environment with semi-natural vegetation. The approach aims to link sediment production to vegetation types to improve land degradation assessment and management strategies.

eDNA was analysed using an amplicon sequencing approach targeting the plant species in soil samples from representative land cover types and river sediment from four flood events. Data analysis included quantifying the eDNA concentration, identifying indicator species of plant communities, determining relative abundances and visualizing differences in community composition.

The findings confirm that soils carry a distinct eDNA signature reflective of plant communities, even in degraded or eroded conditions. Our results demonstrate that eDNA in eroded sediment from Solanum tuberosum L. (potato) fields in a lowland catchment was correctly identified and that at a high mountain environment, vegetation from heath and forest dominated the eDNA signal in sediment after flood events. However, the study also highlights important limitations associated mostly to sampling.

Plant-based eDNA shows promise for identifying sediment sources and providing ecological context. However, its effectiveness depends on factors such as eDNA persistence, source sampling, and sediment connectivity, rendering the method semi-quantitative. Further research is needed to improve consistency and broader applicability.