Catotelm

Catotelm is a term used in peatland ecology and soil science to describe the deepest, permanently waterlogged portion of a peat profile. It lies below the acrotelm, the uppermost living and seasonally variable layer. The catotelm experiences long periods of saturated, anaerobic conditions that slow microbial decomposition, leading to the accumulation of organic matter and the formation of peat that can persist for millennia. The material in the catotelm is generally more decomposed than that in the overlying acrotelm, often classified as sapric peat, and shows low bulk density and high humification.

The boundary between acrotelm and catotelm is not fixed; it depends on hydrology, climate, and peat age, but the catotelm is defined by its persistent saturation and reduced decomposition. Carbon stored in the catotelm represents a major long-term reservoir in boreal and temperate peatlands. Disturbances such as drainage, peat extraction, or fire can expose catotelm to oxygen, increasing decomposition and releasing stored carbon as CO2 and methane.

In peatland management and restoration, protecting the hydrological regime that maintains the catotelm’s anoxic conditions helps limit carbon loss. Catotelm depth varies with peatland type, from several meters in deep peat bogs to shallower in younger deposits. The concept complements the acrotelm, emphasizing the vertical stratification of peatland soils and their differing biogeochemical processes.