AbstractThe classic explanation of the low pH in bogs attributes this phenomenon to the H+exchange capacity ofSphagnum. However, recent researchers have challenged this theory, arguing instead that such exchange could not account for the ions measured and that organic acids were a more likely explanation. We have attempted to determine ifSphagnumcan exchange sufficient hydrogen to account for the low pH of the bog surface zone. To determine cation exchange capability ofSphagnum magellanicumin relation to the common cations of natural habitats, distilled and deionized water and different concentrations of Mg2+, Ca2+, K+, and Rudolph's Sphagnum nutrient medium were tested. In these experiments Sphagnum changes the pH of a surrounding liquid medium in the pH range of 3 to 7. The cation exchange capacity of Sphagnum magellanicum follows the series K+