Acrotelm and catotelm
The catotelm and acrotelm represent two distinct soil layers in undisturbed peat bogs that control the hydrological regime. The catotelm is the bottom layer of peat that is permanently below the water table. Under these anaerobic conditions, microbial activity and peat decomposition is very slow. The catotelm is composed of relatively decomposed compacted peat and water movements are slow.