The spatial factor, rather than elevated CO₂, controls the soil bacterial community in a temperate Forest Ecosystem

Area of Science:

• Ecology
• Microbiology
• Environmental Science

Background:

• Global atmospheric carbon dioxide (CO₂) concentrations are rising, impacting terrestrial ecosystems.
• The response of soil bacterial communities to elevated CO₂ remains poorly understood.
• Understanding these responses is crucial for predicting ecosystem functions.

Purpose of the Study:

• To determine the relative influence of elevated CO₂, nitrogen (N) fertilization, and spatial variation on soil bacterial communities.
• To investigate the impact of soil environmental factors on bacterial diversity and community structure.
• To differentiate the effects of CO₂ enrichment and soil fertility on soil microbes.

Main Methods:

• Utilized a free-air CO₂ enrichment (FACE) site in Duke Forest, North Carolina.
• Employed both sequencing-based approaches and denaturing gradient gel electrophoresis (DGGE) for bacterial analysis.
• Applied multivariate regression tree analysis to partition variation and assess correlations with soil properties.

Main Results:

• Spatial variation explained over 70% of the diversity and 20% of the structure in soil bacterial communities.
• Elevated CO₂ or N treatments explained less than 3% of the variation in bacterial communities.
• Bacterial diversity was positively correlated with total soil nitrogen and negatively with the C/N ratio.
• No significant correlation was found between bacterial community structure and investigated soil properties.

Conclusions:

• Spatial heterogeneity is a dominant factor shaping soil bacterial diversity and community structure in temperate forests.
• Elevated CO₂ and N fertilization have minimal direct impact on soil bacterial communities compared to spatial influences.
• Soil properties like total nitrogen and C/N ratio are key drivers of bacterial diversity, but not community structure.