PubMed · 2026-05-08
A new study finds that waterlogged, oxygen-free soils actually break down plant compounds called polyphenols faster than dry, oxygenated soils — the opposite of what scientists long believed. Iron minerals in the soil, activated by bacteria under wet conditions, drive this rapid decomposition and release more carbon dioxide, meaning flooded soils may store less carbon than previously thought.
Gallic acid (a common plant tannin) decomposed 1.6–2.2 times faster under anaerobic (oxygen-free) conditions than aerobic ones, with degradation rate constants of 0.021–0.26 h⁻¹.
Bacterial reduction of iron minerals shifted the breakdown pathway away from polymerization (carbon storage) toward mineralization, releasing approximately 3 times more CO₂.
Soil validation confirmed anaerobic degradation rate constants (~0.12 h⁻¹) and cumulative CO₂ production were 2× and 1.5× higher than aerobic conditions, respectively.