Peat Mosses (Sphagnum)

This group gathers Mosses and Liverworts subcategory members belonging to the genus Sphagnum, the peat mosses, a distinctive lineage so different in structure from every other moss that it is placed in its own separate class, Sphagnopsida. Peat moss leaves are built from an unusual mixture of living, photosynthetic cells and larger, dead, empty cells with pores that can absorb and hold many times the plant's own dry weight in water, an adaptation that lets peat moss create and maintain the permanently waterlogged, low-oxygen conditions of a bog largely on its own. As peat moss dies, its remains decompose extremely slowly in that acidic, oxygen-poor environment, accumulating over centuries and millennia into deep layers of peat that store an enormous quantity of carbon, making peatlands, despite covering a relatively small fraction of the Earth's land surface, one of the planet's most important terrestrial carbon reservoirs, and dried peat moss itself has long been harvested for horticultural use and, historically, as a fuel.