Modelling the movement of biogenic silica from terrestrial vegetation to riverine systems within the continental USA

Landscape change in vegetation has the potential to alter dissolved concentrations of silica in rivers and silica transport to oceans. To expand our understanding of the influence of land cover on biogenic silica (BSi) export, a terrestrial biogenic silica model is developed. This model quantifies biogenic silica fluxes for North American grasslands, wetlands, coniferous and deciduous forests. The Terrestrial Silica Box (TerSiB) model incorporates the production of primary and amorphous silicates as phytoliths (and their annual dissolution), storage, and leaching of Si in soils. Land cover types were found to reflect signature BSi production rates and to influence soil properties affecting DSi delivery. Results showed that conifer-dominated regions expressed the highest silica flux to rivers (4.7 kg ha(-1) yr(-1)) while wetlands showed the lowest (0.26 kg ha(-1) yr(-1)); trends that are well supported by the literature. Grassland and deciduous regions displayed export values of 0.90 kg ha(-1) yr(-1) and 0.38 kg ha(-1) yr(-1), respectively. High BSi export in conifer-dominated systems can be explained by high dissolution rates and a high leaching coefficient. Wetland systems showed significantly lower export values where approximately 90% of the Si produced is believed to remain in soils. Leaching of biogenic silica is altered by catchment parameters which can promote/retard watershed retention, soil processes, and initial production of biogenic silica by plant types. (C) 2015 Elsevier B.V. All rights reserved.