Mobilization of Silica in Terrestrial Grassland Ecosystems and the Potential Impact on the Global Silica Cycle.

We demonstrate the impact of grassland ecosystems on silica mobilization in the terrestrial environment.  The biogeochemical behavior of silica is closely linked to that of other important elements, including soil carbon and the carbon cycle.  While marine diatoms are a major control on the distribution of silica in the oceans, and play a major role in controlling atmospheric pCO₂ via the “biological pump.”  The importance of biological controls on silica cycling in the terrestrial environment is much less well known, but this paper indicates that the formation and storage of biogenic silica in plants and soils, particularly in grasslands, is of fundamental importance. Recent estimates suggest that the global uptake of biogenic silica by terrestrial biomass ranges from 60 to 200 Tmol yr^-1 and rivals quantities stored in the biologically active portions of the ocean systems. Importantly, the largest reservoir of biogenic silica in terrestrial systems resides not in living biomass but in soils, as biogenic silica is deposited upon death and decomposition of the plant materials.  This large, but currently poorly defined, reservoir of biogenic silica is potentially of great importance in global biogeochemical cycles.  We will present our research on the biogeochemical cycle of silica in grasslands, as they are both highly dynamic and store large quantities of biogenic silica.