Microbial nitrogen cycling in wetland forests with varying management statuses across Europe

Temperature and oxygen content in soil are the well-known drivers of macronutrient cycling, as they influence the overall conditions that regulate microbial metabolism. However, the more detailed underlying aspects affecting nutrient cycling remain insufficiently understood.

This study focuses on different wetland forest types across Europe, aiming to investigate N cycling processes, the spatial distribution of N cycling genes and the linkage with soil greenhouse gas (GHG) emissions and relevant environmental parameters. The study sites were located in Finland, Estonia, and Latvia in Northern Europe, as well as in France and Spain in Southern Europe. The Northern Europe sites consisted of drained peatlands with varying management statuses, while the Southern Europe ones were alluvial forests. Soil samples were collected from three depths (0-10, 10-20, 20-40 cm) in autumn 2023, analysed using quantitative polymerase chain reaction (qPCR), and sequenced to assess processes and communities. In all samples, soil physico-chemical parameters were also determined and simultaneously with soil sampling, in-situ GHG emission measurements were done all as a part of Horizon Europe ALFAwetlands project.  

Preliminary results of the quantification of N cycle genes revealed differences in the microbiome across wetland forest types in Europe. Ammonia-oxidizing archaea appeared to be the primary nitrifiers in the soils of the study sites, compared to ammonia-oxidizing bacteria. The alluvial forest soils revealed a higher genetic potential for the DNRA (Dissimilatory Nitrate Reduction to Ammonium) process in soil. The abundance of genes responsible for the comammox process—complete ammonia oxidation by a single microorganism—was also higher in the soils of the alluvial forests. In the rewetted peatland forest of Latvia, the soil exhibited a greater genetic potential for denitrification and DNRA processes compared to the drained peatland forests. The further analyses will be exploring the links between N cycle genes, GHG emissions, and soil physico-chemical properties.