Which organism is primarily associated with long-term carbon storage in soils?

• A. Bacteria
• B. Nematodes
• C. Fungi
• D. Algae

Answer: (C)

Long-term soil carbon storage is driven by organisms that produce and stabilize complex organic matter in a way that resists rapid decomposition. Fungi play this central role because they are adept at breaking down tough plant polymers like lignin and, importantly, converting plant debris into fungal biomass and necromass that persists longer in soil. Their hyphae help bind soil particles into stable aggregates, and many fungi produce extracellular substances (such as glomalin from arbuscular mycorrhizal fungi) that cement these aggregates and physically protect carbon from rapid breakdown. This combination—efficient processing of resistant materials and creation of durable soil aggregates—puts fungal inputs into a long-lasting carbon pool.

Bacteria, by contrast, tend to drive faster carbon turnover, quickly mineralizing available carbon and contributing to more labile soil organic matter rather than the persistent pool. Nematodes are mainly consumers moving through the food web and influence carbon dynamics indirectly rather than acting as primary storage agents. Algae contribute organic matter through photosynthesis, but their outputs in soil are generally more transient and surface-associated, not the enduring storers of soil carbon that fungi cultivate.

So, the organism most closely linked with long-term carbon storage in soils is fungi.