Biogeochemistry and weathering in a forest catchment and an arable field in central Sweden

Abstract

Fluxes of base cations, nitrogen and phosphorus were investigated in a long-term study at a forest site and a nearby arable site in central Sweden. At both sites soil mineralogy was reflected in the stream water concentrations, especially during base-flow. Weathering rates for the major base cations and natrium (SBC + Na) in the forest soil calculated from empirical relationships and quartz distribution in the soil profile were 0.4 and 0.3 kmolc ha−1 year−1, respectively. Simulations using the PROFILE model of forest soil predicted a weathering rate of 0.6 kmolc ha−1 year−1 Net vegetation uptake of base cations was calculated to be larger, at 0.8 kmolc ha−1 year−1 In the soil of the arable site biogeochemical fluxes resulting from weathering and biomass removal were one order of magnitude faster. Budget calculations for the arable land indicated that a weathering rate of 7 kmolcha −1 year −1 was needed to keep the system in balance. Weathering of Mg was estimated to be equal to the amount applied as fertilizer based on the quantities supplied during a 15-year period of conventional farming. For K the ratio of weathering to the need for fertilization was estimated at 1.5. © 1998 Scandinavian University Press.