Wildfire effects on diversity and composition in soil bacterial communities

Area of Science:

• Ecology
• Microbial Ecology
• Environmental Science

Background:

• Mediterranean ecosystems face increasing wildfire frequency and severity, linked to climate and land use changes.
• Wildfire impact assessment traditionally focuses on vegetation damage, with less attention on microbial communities.
• Soil bacterial communities can serve as sensitive indicators of wildfire severity.

Purpose of the Study:

• To investigate the impact of wildfire severity on soil bacterial communities in diverse Mediterranean ecosystems.
• To compare bacterial community structure and diversity across different fire severities and ecosystem types.
• To identify potential bacterial indicators of wildfire impact.

Main Methods:

• Sampling of soil bacterial communities from three Mediterranean ecosystems (two shrubby, one arboreal) two months post-wildfire.
• Comparison of bacterial communities between two fire severity levels and unburnt control soil.
• Analysis of bacterial diversity (richness and Shannon's diversity) and community composition.

Main Results:

• Increased wildfire severity significantly reduced soil bacterial diversity, with richness and Shannon's diversity decreasing by up to 40.6% and 58.6%, respectively, in high-severity fires.
• Fire severity was the primary driver of differences in bacterial communities, followed by ecosystem type.
• Five bacterial families (Oxalobacteraceae, Micrococcaceae, Paenibacillaceae, Bacillaceae, Planococcaceae) became dominant across all studied ecosystems, with some species increasing in frequency by 100-fold.

Conclusions:

• Soil bacterial communities are highly sensitive to wildfire severity in Mediterranean ecosystems.
• Bacterial diversity and composition can serve as effective indicators for assessing wildfire impacts.
• While certain bacterial groups dominate post-fire, specific dominant species may vary due to stochastic factors.