Peat basin swamps are dome-shaped with 'ombrogenous peat' occupying the central portion of the peat dome (Murtedza et al., 2002; Tie, 1990).
(b) Ombrogenous peat: plant remains formed by plants growing solely on nutrient cycled through vegetation and peat (no mineral subsoil or ash content) and is fed by rain water only.
Ombrogenous peat is characterized by a high water content, an extremely low bulk density, a relatively higher decomposition rate and a relatively lower pH, and is composed of mainly loose trunks, branches, roots, fruits and leaves (Paramananthan, 2011).
Geogenous ("mineral-fed"), often-acidic fens and ombrogenous ("rain-fed") bogs (terminology follows Bridgham et al.
Plant productivity is generally higher in fens than in bogs (Bradbury and Grace 1983) coincident with a general increase of electrolytes and pH from acidic ombrogenous bogs, through low-pH fens to alkaline, high-pH fens (Sjors 1950).
In contrast, the ombrogenous, precipitation-dominated wetlands receive external nutrients mainly from atmospheric sources.