Microbial community dynamics in two Central European peatlands affected by different nitrogen depositions.

Changes in organic matter accumulation in wetlands are critical for climate dynamics. Different nitrogen (N) inputs in Sphagnum-dominated peat bogs can lead to varying rates of carbon (C) and N accumulation, influencing greenhouse gas emissions. We investigated how contrasting N deposition shapes microbial communities in two Czech peat bogs, focusing on biological N2 fixation (BNF) as a key N input in pristine wetlands. Higher N deposition resulted in a more active microbial community with increased enzyme activity and C acquisition, potentially accelerating decomposition and reducing C storage. Enhanced denitrification, indicated by active nosZ Clade I genes, suggests that higher N inputs may increase N losses through denitrification. In contrast, the lower N site showed a less active microbial community with slower decomposition, beneficial for C sequestration, though potentially less adaptable to future N increases. Experimental BNF rates were 70 times higher at the high N site, consistent with elevated diazotroph activity indicated by active nifH gene. Phosphorus (P) availability and NH4+/NO3- ratios appeared to drive BNF differences, emphasizing the need for managed N inputs to maintain peatland ecological functions.