Soil formation under two moss species in sandy materials of central British Columbia (Canada)

Mosses can influence soil formation because of its role in the transfer of energy, water and chemical compounds. This study was conducted (1) to compare the morphological, chemical and mineralogical properties of soils under two species of mosses (Pleurozium schreberi (Brid.) Mitt. and Ptilium crista-castrensis (Hedw.)), and (2) to determine the chemical composition of the moss carpets associated with these two species. We measured the pH, cation exchange capacity, exchangeable cations, and pyrophosphate-extractable Fe and Al from soils collected from the mineral horizons of the soils that developed under these two mosses using standard procedures. The mineral composition of the soil was determined using X-ray diffraction techniques while the chemical composition of the moss carpets was determined using ICP-AES and NMR spectroscopy. Results show that the Ae horizon is thicker (6–12 cm) beneath Pti. crista-castrensis than under Ple. schreberi (0–2 cm). The Na-pyrophosphate extractable Fe and Al in the Bf horizon is higher (0.70%) in soil under Ptilium than the soil under Pleurozium (0.48%). Clay mineral composition of the Bf and C horizons in the two soils consist of mica, chlorite and kaolinite. In the Ae horizon, chlorite is not detectable and 2:1 expanding clays are dominantly present in soil under Ptilium while the soil under Pleurozium contains chlorite with minor amounts of 2:1 expanding clays. Moss carpets have similar amounts of various types of organic compounds including carbohydrates, carboxyl C and ketones. Elemental contents (in mg kg−1) of the moss carpets show significantly higher Mg, Al and Fe in Pleurozium (Mg=1203, Al=5029 and Fe=5777) than in Ptilium (Mg=820, Al=2624, and Fe=2548). The low levels of Mg and Fe in Ptilium beds accompanied by high water content may result from the removal of the brucite (Mg and Fe) layer in chlorite and the transformation of mica into 2:1 expanding clays. Our results indicate a higher intensity of podzolization under Ptilium compared to Pleurozium, probably due to the influence of moss cover on the movement of Fe, Mg and Al and water in and out of the moss carpets assuming that influence from moss population dynamics and cyclical processes is minimum.