Marshes are characterized by seasonal water level fluctuations, relatively high amounts of water flow, and are influenced by ground and surface waters. Mosses are generally lacking or not abundant as they do not compete well with rapid vascular plant growth and do not tolerate large fluctuations in seasonal water levels. As with shallow open waters, chemical differences in marshes strongly influence their floristic composition. Swamps are forested, wooded or shrubby non-peaty wetlands. Swamps and marshes have a poorly developed bryophyte layer that results from strong seasonal water level fluctuations and high vascular plant production.
Peat accumulation is limited in swamps as decomposition rates are high.
Vegetatively swamps are quite diverse and in Alberta may be composed of some combination of Larix laricina , Picea mariana , Betula , and Salix . Peatlands , often termed muskeg, differ from non-peat forming wetlands by a combination of interrelated hydrologic, chemical, and biotic factors that results in a decrease in decomposition relative to plant production allowing for the accumulation of peat. The initiation of peat accumulation is related to stabilization of seasonal water levels and restriction of water flow through a wetland, in conjunction with leaching of salts from the mineral substrate allows for the establishment and development of a moss layer. The establishment of a moss layer results in the accumulation and maintenance of nutrients in a nonavailable form, reducing vascular plant production. As peat accumulates, surface vegetation can become isolated from the underlying substrate, coupled with biologic and chemical processes this can lead to acidification and oligotrophication.