We focus on a series of well characterised field sites (in the Swiss Central Alps, the Californian Southern Sierra Nevada, and the highlands of Sri Lanka). They are underlain by similar granitic lithologies, and together define an “erodosequence” – sites that define a gradient of erosion rates, analogous to a “chronosequence” or a “climosequence”. We combine our expertise in cosmogenic nuclides and metal (isotope) geochemistry to yield quantitative data on the absolute and relative fluxes of elements in the eroding Critical Zone, to test hypotheses related to the influence of erosion on weathering and element cycling.

The rate of rock supply also sets an upper limit on the rate at which key mineral nutrients, e.g. phosphorous, potassium, magnesium or zinc, can be supplied to an ecosystem. We are therefore also interested in the strategies ecosystems apply in order to obtain and retain these essential nutrients, and whether these strategies differ along the erodosequence.

Figure: A “chronosequence” can be seen here. Here, the weathering zone and soil develop with age following the exposure of unweathered rock (by a glacial retreat or a freshly solidified lava flow, for example). Below we see an “erodosequence”. In this there is no actual soil age, but a “residence time” that decreases as the erosion rate increases. Geochemical fluxes decrease with both age (chronosequence) and residence time (erodosequence), while nutrient cycling by plants increases.