Plants causing peat formation are called peat formers. Their dying-off and incomplete decay which occurs in conditions of lack of oxygen and excessive moisture, leads to formation of a useful fertilizer. In the peat-forming layer, approximately at a depth of 50 cm, microorganisms (fungi, invertebrates, bacteria) consume decay products reducing the phytomass weight. However, not all decay products turn into peat – about 70% of dead plants become food for their "relatives", washed out or evaporated into the atmosphere.
If the peat deposit has preserved vegetation, the formation process will continue further. How large is the increase in peat deposits can be determined by herbaceous plants, the green chlorophyll-bearing part of the sphagnum, various root systems, conifers.
The accumulation of dead organic matter has been going on for thousands of years – the age of the first finds relates to carbon (the penultimate geological period). Due to the stopped decomposition processes, peat can maintain its properties for millennia, but the rate of peat accumulation is difficult to determine. The point is the dependence of this process on plant groups, geography and the climate of peat formation.