Dissolved Si export: Impact of increased water fluxes through soil

Abstract

Intense deforestation over large areas is an important component of global models which aim to quantify the transfer of terrestrial siliceous material from the continent to the coast. Hence, there is a need for improved understanding of land use impact on Si export. We present a model that simulates the kinetic dissolution of biogenic Si in a forest soil. A kinetic equation was calibrated based on leaching experiments of soil columns at constant water flux. The calibrated equation was then used to simulate the Si export from a forest soil under varying atmospheric conditions and provided realistic Si concentrations in soil water. The same model was used to simulate the impact of reduced evapotranspiration due to deforestation and consequently increased soil water fluxes on the Si export. Results showed that lower amounts of biogenic silicon dissolved and higher Si fluxes were released to the system once water flux increased. The use of the kinetic dissolution equation for biogenic Si improves our understanding and the modelling of the Si release from soils towards the hydrographic system.