Microbial communities with distinct denitrification potential in spruce and beech soils differing in nitrate leaching

Area of Science:

• Forest Ecology
• Soil Microbiology
• Biogeochemical Cycling

Background:

• Elevated acid deposition poses a significant global threat to ecosystems, primarily through nitrogen leaching.
• Understanding variable nitrate losses in European forests post-acid deposition is crucial for ecosystem management.
• Forest vegetation type influences soil properties and microbial communities, affecting nitrogen cycling.

Purpose of the Study:

• To investigate the link between soil microbial functional characteristics and variable nitrate losses in recovering European forests.
• To compare nitrogen cycling microbial guilds in adjacent beech and spruce forests with differing acidification recovery and nitrate leaching.
• To identify potential keystone microbial species influencing nitrogen immobilization and ecosystem retention.

Main Methods:

• Reconstruction of soil microbial functional traits related to nitrogen and carbon cycling based on community composition analysis.
• Comparison of microbial communities in adjacent beech and spruce forest soils with contrasting acidification levels and nitrogen leaching.
• Assessment of the ratio of denitrification to dissimilative nitrogen reduction to ammonium (DNRA) as an indicator of nitrate loss pathways.

Main Results:

• Acidic spruce soils (high C, Acidobacteria/Actinobacteria dominant) showed high potential for nitrate loss via denitrification (denitrification:DNRA ratio = 3).
• Less acidic beech soils (low C, high N availability, Proteobacteria dominant) had lower denitrification potential (denitrification:DNRA ratio = 1), potentially increasing nitrate availability.
• Distinct microbial guilds, including DNRA-capable microbes in beech and denitrifiers in spruce, were identified, suggesting vegetation-driven functional specialization.

Conclusions:

• Vegetation dominance (beech vs. spruce) drives distinct soil microbial functional guilds, even after acid deposition impacts.
• These microbial differences significantly influence nitrogen immobilization potentials and the overall nitrogen retention capacity of forest ecosystems.
• Understanding these microbial dynamics is key to predicting and managing nitrogen leaching in recovering forest ecosystems.