Elevated Air Humidity Changes Soil Bacterial Community Structure in the Silver Birch Stand

Area of Science:

• Forest ecology
• Microbial ecology
• Climate change impacts

Background:

• Soil microbes are crucial for forest ecosystems and sensitive to environmental shifts.
• Climate change predicts increased temperatures and altered hydrological cycles, particularly in the Baltic Sea region.
• Understanding humidity's effect on soil microbes is vital for predicting forest ecosystem responses.

Purpose of the Study:

• To assess the impact of elevated air humidity on the topsoil microbial community structure in a silver birch stand.
• To investigate the relationship between humidity-induced microbial changes and soil abiotic/biotic factors.
• To analyze the effects on bacterial communities in both bulk soil and the birch rhizosphere.

Main Methods:

• Utilized a free air humidity manipulation (FAHM) facility to control humidity levels.
• Employed high-throughput sequencing of 16S rRNA gene fragments to analyze bacterial community structure.
• Quantified denitrification-related genes (nir, nosZ) and assessed root morphology.

Main Results:

• Increased air humidity significantly altered bacterial community structures in both bulk soil and rhizosphere.
• Changes were linked to modified soil abiotic factors (e.g., pH) and biotic factors, notably root morphology (absorptive root diameter).
• Decreased abundance of nir and nosZ genes was observed in the rhizosphere, though N2O emission potential remained unaffected.

Conclusions:

• Elevated air humidity reshapes soil bacterial communities in silver birch stands.
• Root morphology plays a critical role in mediating microbial community responses to humidity in the rhizosphere.
• These shifts influence soil C, N, and P turnover, highlighting ecosystem adaptation mechanisms to changing climate conditions.