Concepts of fen and bog re-examined in relation to bryophyte cover and the acidity of surface waters

Studies of surface-water pH and bryophyte assemblages in 440 plots from five peatland regions across northern North America reveal a very distinct, two-fold division into fens with a pH mode at 6.76-7.00, in which Amblystegiaceae are prominent, and bogs with a pH mode at 4.01-4.25, in which Sphagnaceae are dominant. The relevance of the data to past and current views on peatland classification is explored.