Soil production limits and the transition to bedrock-dominated landscapes

The extent and persistence of the Earth's soil cover depends on the long-term balance between soil production and erosion. Higher soil production rates under thinner soils provide a critical stabilizing feedback mechanism ^1-3, and climate- and lithology-controlled soil production is thought to set the upper limit for steady-state hillslope erosion ⁴. In this framework, erosion rates exceeding the maximum soil production rate can be due only to bedrock mass wasting ⁵. However, observation of pervasive, if patchy, soil cover in areas of rugged topography and rapid erosion indicates additional stabilizing mechanisms. Here we present ¹⁰Be-derived estimates of soil-production and detrital erosion rates that show that soil production rates increase with increasing catchment-averaged erosion rates, a feedback that enhances soil-cover persistence. We show that a process transition to landslide-dominated erosion in steeper, more rapidly eroding catchments results in thinner, patchier soils and rockier topography, but find that there is no sudden transition to bedrock landscapes. Instead, using our global data compilation, we suggest that soil production may increase in frequency and magnitude to keep up with increasing erosion rates. We therefore conclude that existing models ^6-8 greatly exaggerate changes in critical-zone processes in response to tectonic uplift.