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 compa re the morphological, chemical and mineralogical properties of soils under two species of mosses (Pleurozium schreberi (Brid.) Mitt. and Ptilium crist a-castrensis (Hedw.)), and (2) to determine the chemical composition of the moss carpets associated with these Mo species. We measured the pH, cation exchange capacity, exchangeable cations, and pyrophosphate-extractable Fe a nd AI from soils collected from the mineral horizons of the soils that deve loped under these two mosses using standard procedures. The mineral composi tion of the soil was determined using X-ray diffraction techniques while th e 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) be neath Pti. crista-castrensis than under Pie. schreberi (0-2 cm). The Na-pyr ophosphate extractable Fe and Al in the Bf horizon is higher (0.70%) in soi l under Ptilium than the soil under Pleurozium (0.48%). Clay mineral compos ition of the Bf and C horizons in the two soils consist of mica, chlorite a nd kaolinite. In the Ae horizon, chlorite is not detectable and 2:1 expandi ng clays are dominantly present in soil under Ptilium while the soil under Pleurozium contains chlorite with minor amounts of 2:1 expanding clays. Mos s carpets have similar amounts of various types of organic compounds includ ing carbohydrates, carboxyl C and ketones. Elemental contents (in mg kg(-1) ) of the moss carpets show significantly higher Mg, AI 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 days. O ur results indicate a higher intensity of podzolization under Ptilium compa red to Pleurozium, probably due to the influence of moss cover on the movem ent 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. (C) 2000 Elsevier Science B.V. All rights reserved.