Lithospheric organic carbon (“petrogenic”; OCpetro) is oxidized during exhumation and
subsequent erosion within mountain ranges. This process is a significant source of CO2 to the
atmosphere over geologic timescales, but the mechanisms that govern oxidation rates in
mountain landscapes remain poorly constrained. We demonstrate that, on average, 67 ± 11 % of
OCpetro initially present in bedrock exhumed from the tropical, rapidly eroding Central Range of
Taiwan is oxidized within soils, leading to CO2 emissions of 6.1 – 18.6 t C km-2 yr-1. The
molecular and isotopic evolution of bulk OC and lipid biomarkers during soil formation reveals
that OCpetro remineralization is microbially mediated. Rapid oxidation in mountain soils drives
CO2 emissions fluxes that increase with erosion rate, thereby counteracting CO2 drawdown by
silicate weathering and biospheric OC burial.
