Microbial mechanisms mediating increased soil C storage under elevated atmospheric N deposition

Area of Science:

• Forest Ecology
• Soil Microbiology
• Biogeochemistry

Background:

• Anthropogenic nitrogen (N) deposition influences forest ecosystem carbon (C) cycling and storage.
• Experimental N deposition in a northern hardwood forest reduced forest floor decay, increasing soil C storage.
• Microbial mechanisms underlying this response require further investigation.

Purpose of the Study:

• To investigate the impact of experimental nitrogen deposition on the functional genes of soil actinobacteria and fungi.
• To understand how changes in microbial functional genes relate to forest floor decay and soil carbon storage.

Main Methods:

• Utilized GeoChip 4.0, a high-throughput functional-gene microarray, to analyze microbial communities in forest floor soil.
• Examined functional genes from actinobacterial and fungal communities under ambient and experimental N deposition.
• Assessed gene richness, diversity, and composition related to organic matter depolymerization and oxidation.

Main Results:

• Experimental N deposition significantly altered the composition and increased heterogeneity of functional genes in actinobacterial and fungal communities.
• A significant decrease in the richness and diversity of genes involved in the depolymerization of starch, hemicellulose, cellulose, chitin, and lignin was observed.
• Genes encoding oxidoreductases, crucial for lignin decay, showed altered composition, contributing to community dissimilarity under N deposition.

Conclusions:

• Experimental nitrogen deposition impacts microbial functional genes, reducing the diversity and richness of decay-associated enzymes.
• These microbial shifts correlate with reduced forest floor decay and enhanced soil organic matter accumulation.
• Changes in actinobacterial and fungal community gene composition have significant functional implications for forest ecosystem carbon cycling and storage.