Linkages between the soil organic matter fractions and the microbial metabolic functional diversity within a broad-leaved Korean pine forest

• Metabolic activity showed moderate spatial dependence.
• The nugget to sill ratio for functional diversity was <0.25, suggesting a strong spatial dependence.
• Among all SOM fractions, the DOC accounted for the largest effects on variation.

Patterns in the spatial distribution of soil microorganisms and the factors that determine them provide important information about the mechanisms regulating diversity and function of terrestrial ecosystems. The spatial heterogeneity of metabolic functional diversity of soil microorganisms was studied across a 30 × 40 m plot and at two soil depths (0–10 cm and 10–20 cm) in a natural, mixed broad-leaved Korean pine (Pinus koraiensis) forest soil in the Changbai Mountains. In addition, we assessed the importance of the quantity and quality (indicated by labile soil organic matter fractions) of soil organic matter in small-scale structuring of soil microbial metabolic functional diversity. Microbial metabolic functional diversity was characterized based on the Biolog profile. The results showed that metabolic activity exhibited moderate spatial dependence, while functional diversity had a much stronger spatial dependence. All soil organic matter fractions including total soil organic matter, dissolved organic matter, particulate organic matter explained 15–27% of the variance in microbial functional diversity in the two soil layers. Among all soil organic matter fractions, the labile dissolved organic carbon accounted for the largest amount of variation. Overall, the significant relationship between soil microorganisms and organic matter fractions allows for better understanding the ecological functions governing C cycling and microbial communities in forest ecosystems.