A 12 year study reveals that biochar increases stable microbial carbon in topsoil but can actually reduce it in deeper soil layers. This suggests that the effectiveness of biochar for carbon sequestration depends heavily on the soil profile and depth of application. The research highlights that while fungal necromass helps build carbon reservoirs near the surface, subsoil microbes may break down existing residues due to nutrient stress. This finding challenges the assumption that biochar provides a uniform carbon benefit across all soil depths.
