Continental-scale drivers of soil microbial extracellular polymeric substances

Area of Science:

• Soil Science
• Microbiology
• Environmental Science

Background:

• Extracellular polymeric substances (EPS) are crucial microbial residues contributing to soil organic carbon (SOC) and soil aggregation.
• Understanding the large-scale controls on EPS abundance and function is essential for soil carbon cycling research.

Purpose of the Study:

• To investigate the abundance and large-scale controls of EPS across diverse European environments.
• To determine the influence of bedrock, climate, and land use on EPS content and its relationship with soil organic carbon and microbial biomass.

Main Methods:

• Extensive soil sampling across a European transect with varied climates, bedrocks, and land uses.
• Quantification of soil EPS content, EPS-carbon (EPS-C), soil organic carbon (SOC), and microbial biomass carbon (MBC).
• Statistical analysis to identify correlations between EPS, environmental factors, and microbial properties.

Main Results:

• Average soil EPS content was 956 ± 55 µg g⁻¹ soil, with EPS-C contributing 1.6 ± 0.1% to SOC.
• Bedrock significantly influenced EPS content, EPS-C contribution to SOC, and the EPS-C/MBC ratio.
• Land use primarily affected the EPS-C/MBC ratio, which was negatively correlated with microbial growth and carbon use efficiency, and increased under water deficit.

Conclusions:

• EPS is a key microbial residue significantly regulated by climatic, edaphic, microbial, and land-use factors.
• Bedrock and land use are major drivers of EPS dynamics and their contribution to soil carbon.
• Findings have significant implications for understanding soil carbon cycling and sequestration strategies.