Katotelm

Katotelm, also spelled catotelm, is a term used in peatland science to describe the deeper, permanently saturated layer of peat deposits beneath the upper, dynamic horizon. In many peatlands, the peat profile is treated as two zones: the acrotelm at the surface, where the water table fluctuates and processes such as oxidation and physical decay are common, and the catotelm below, where saturation is continuous and biological turnover is slow. This lower layer tends to be more decomposed and humified than the material in the acrotelm, reflecting long-term accumulation under anaerobic conditions. The catotelm's properties are controlled by hydrology, temperature, and microbial activity; low redox potential prevents rapid decay, but gradual mineralization still occurs over centuries.

Because peat deposits store large amounts of carbon, the catotelm represents a major long-term carbon reservoir in many peatlands. Drainage, peat extraction, or climate warming can alter its stability by increasing decomposition and carbon flux to the atmosphere as CO2 and methane. In field studies, researchers identify the catotelm by coring and stratigraphic analysis to locate the transition from the acrotelm, and to estimate carbon stocks and peat age.

Etymology: The term originates in peatland literature and is widely used in English-language science; variants such as katotelm appear in translations.