Drivers controlling spatial and temporal variation of microbial properties and dissolved organic forms (DOC and DON) in fen soils with persistently low water tables

Factors controlling dissolved organic carbon (DOC) and nitrogen (DON) production in degraded fen peatlands remains largely equivocal. Thus, the purpose of this research was to determine whether short-term changes in DOC and DON content and microbial properties are related to variations in weather conditions, soil properties and human activity. The study was conducted in May and September 2017–2019 to determine the seasonal variations in the abovementioned parameters in soil layers (0–30 cm) of a long-term agricultural peatland additionally affected by open-pit mining. We found that the most critical environmental factors that shape microbial community structure and activity are air temperature and precipitation, which explained 59.9% of the variability. Air temperature was also the most important explanatory factors for DOC and DON variation, which explained 18.9% of the total variability. Moreover, in the case of DOC and DON production, significant positive correlations with soil organic carbon content (DOC r = 0.46, p < 0.01; DON r = 0.54, p < 0.001) was found. The potential impact of open-pit mines on the DOC and DON production was not confirmed, as there was no significant difference between sites located in the depression cones (caused by lignite mining) and those sites affected exclusively by agriculture drainage. This work hopes to contribute towards a deeper understanding of the variables and dependencies that affect the production of labile organic forms in degraded fen peatland soils in the temperate climate zone.