Portlethen Moss millennia of evaporation, further intensifying the soil acidity, fueled by organic matter decaying, with little drainage outlet. A layer of sphagnum moss would have developed at the benthic level of the bog, and additional sphagnum layers floated in mats atop the bog. At an intermediate level of evolution, thick peat layers formed from decay and carbonisation of the rotting sphagnum. Generations of carex and juncus flourished, leading to further decay of these materials and eventual heightening of the organic mass. Finally, secondary vegetation took root in the spongy sphagnum mats adding greater biomass to the bog.In some cases the heavy
Portlethen Moss saturated organic layers could actually rupture, spilling large volumes of mud and organic debris to surrounding fields, thus enabling a bed for further spatial expansion of the entire bog. Ultimately the colour of the moss waters became blood red in colour, from the successive organic decay and stagnation. Only in times associated with cattle grazing and significant human presence (probably the late Iron Age), would this process reverse and the bog reduce in size. A wide variety of sphagnum, sedges, rushes and other characteristic bog species inhabit Portlethen Moss. Sometimes insectivorous plants reside in mosses, since the soils are generally