Ge/Si ratios point to increased contribution from deeper mineral weathering to streams after forest conversion to cropland
(2018) Applied Geochemistry — Vol. 96, p. 24-34 (2018)
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- The impact of forest conversion on soil weathering is studied in a subtropical humid setting in southern Brazil (Rio Grande do Sul). A geochemical tracer of mineral weathering processes, the Ge/Si ratio, was used at the pedon and catchment scales to compare a cropland and a forest catchment. Ge/Si measurements were performed n bedrock, bulk soil, soil pore water and stream waters during base flow and rain events. The Ge/Si ratio in bulk soils is interpreted as the result of a mixing between clay minerals and quartz. Based on the Ge/Si ratio in soil pore water, no change in mineral weathering has been induced by forest conversion at the pedon scale. In contrast, at the catchment scale, the Ge/Si ratio of stream waters indicates an increased contribution from mineral weathering after conversion of forest to cropland. The evolution of Ge/Si ratio in stream waters during rain events points to a change in the hydrological paths due to forest conversion. We argue that forest conversion to cropland led to increased water percolation in soil, allowing the weathering of deeper soil material and thus, a stronger contribution from mineral weathering to stream waters.
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Ameijeiras Mariño, Y., Opfergelt, S., Derry Louis A., Robinet Jérémy, Govers Gerard, Minella Jean P.G., & Delmelle, P. (2018). Ge/Si ratios point to increased contribution from deeper mineral weathering to streams after forest conversion to cropland. Applied Geochemistry, 96, 24-34. https://hdl.handle.net/2078.5/126004 (Original work published 2018)