Shift in nitrogen transformation in peatland soil by nitrogen inputs

Area of Science:

• Environmental Microbiology
• Biogeochemistry
• Peatland Ecology

Background:

• Agricultural intensification has led to increased nitrogen (N) inputs into peatlands, affecting ecological processes and carbon storage.
• Understanding the long-term impacts of N inputs on N transformation processes in peatland soils is crucial but remains incomplete.

Purpose of the Study:

• To investigate the effects of long-term N inputs on N mineralization, nitrification, and key nitrogen transformation pathways in peatland soils.
• To quantify the contributions of nitrite-dependent anaerobic methane oxidation (n-damo), anaerobic ammonium oxidation (anammox), denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) to N2 production.

Main Methods:

• Utilized isotope tracing techniques and quantitative PCR (qPCR) to analyze N transformation rates and microbial abundances.
• Studied a peatland site with over 50 years of documented N inputs.

Main Results:

• N inputs significantly increased N mineralization (77%) and nitrification (43%) rates.
• Contributions of n-damo (242% increase) and anammox (170% increase) to N2 production were substantially enhanced, while denitrification and DNRA contributions decreased.
• N inputs promoted nitrifier, n-damo, and anammox bacteria abundance, but reduced denitrifier abundance, with soil pH identified as a key influencing factor.

Conclusions:

• Long-term N inputs fundamentally alter N cycling pathways in peatlands, shifting dominance towards n-damo and anammox.
• n-damo plays a significant role in N cycling under elevated N conditions in peatlands.
• Findings provide a scientific basis for improved peatland management strategies in response to anthropogenic N enrichment.