Why do grasslands usually have high organic matter?

• A. High rainfall
• B. Extensive root systems
• C. Frequent burning
• D. Dense canopy limiting decomposition

Answer: (B)

Grasslands tend to have high soil organic matter because grasses put a lot of biomass into their root systems, not just above the surface. The fibrous roots spread widely and turnover continuously, dying and decomposing in the soil. That below‑ground litter becomes soil organic matter and, along with root exudates that feed soil microbes, helps form stable organic carbon inside soil aggregates. Even when above‑ground material is removed by grazing or fire, the underground inputs keep accumulating, sustaining high organic matter.

Other factors can influence decomposition and litter, but they don’t explain the pattern as reliably. High rainfall often speeds decomposition, and a dense canopy is more typical of forests than grasslands, while burning mainly removes above‑ground material rather than driving as much soil organic matter production.