Disentangling interactions between microbial communities and roots in deep subsoil.

Area of Science:

• * Soil science and paleoecology
• * Microbial ecology and biogeochemistry
• * Climate change and carbon sequestration studies

Background:

• * Soils, paleosols, and sediments are crucial archives for climate change research and terrestrial carbon pools.
• * Chronological integrity of these archives is vital for reliable paleoenvironmental records.
• * Deep rooting and organic matter (OM) incorporation by roots can compromise archive integrity and OM stability.

Purpose of the Study:

• * To investigate the long-term effects of sedimentary characteristics and deep rooting on deep subsoil microbial communities.
• * To characterize fossil and living microbial communities using molecular markers in a Late Pleistocene loess-paleosol sequence.
• * To assess the influence of ancient and recent root presence on molecular signatures and microbial activity.

Main Methods:

• * Molecular analysis of free and phospholipid fatty acids (FAs).
• * Analysis of core and intact polar glycerol dialkyl glycerol tetraethers (GDGTs).
• * 16S rRNA gene sequencing of bacterial DNA from fossil and living microbial communities.

Main Results:

• * Living microorganisms were detected throughout the sequence, with bacterial communities resembling modern topsoils.
• * Molecular markers showed significant overlap between fossil and living communities, indicating a time-integrated signal.
• * Fossil microbial markers correlated with ancient and recent roots, while living microbial markers correlated only with recent roots.

Conclusions:

• * Post-sedimentary rooting significantly impacts deep subsoil microbial communities and biogeochemical processes.
• * Root-induced OM mineralization can persist for millennia, affecting long-term carbon sequestration.
• * Findings enhance understanding of OM dynamics and carbon storage potential in deep soils.