Quantifying biotic and abiotic Si fluxes in the Critical Zone with Ge/Si ratios along a gradient of erosion rates

A significant portion of silicon (Si) exported from rapidly eroding landscapes, such as the Central Swiss Alps, is transported as secondary solids—clays and plant material—rather than dissolved Si. This finding challenges conventional understanding by revealing that plant biomass contributes substantially to Si export, potentially equating to 25–110% of dissolved Si export in these systems. The study leverages germanium (Ge)/Si ratios across three sites with varying erosion rates—Sri Lanka, the Swiss Alps, and California’s Sierra Nevada—to trace Si cycling in the Critical Zone. Unlike prior approaches, Ge/Si ratios in secondary clays proved more reliable than river solutes for assessing weathering intensity, sometimes outperforming silicon isotopes. The research also highlights that plants do not significantly discriminate against Ge during uptake, suggesting a broader role for biotic processes in Si dynamics.

Frings, P. J., Schubring, F., Oelze, M., & von Blanckenburg, F. (2021). Quantifying biotic and abiotic Si fluxes in the Critical Zone with Ge/Si ratios along a gradient of erosion rates. American Journal of Science, 321(8), 1204–1245. https://doi.org/10.2475/08.2021.03