Vegetation control on long-term to short-term landscape evolution from thermochronology and remote sensing

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This proposal outlines a project that follows the aims of the SPP "EarthShape" by investigating the role of biota for Earth’s shaping processes. This study aims to (i) test the primary assumption of EarthShape that all primary areas share a similar long-term tectonic (rock uplift) history, and (ii) reveal the impact of biota and geomorphologic expression on erosion and sediment transport over millennial timescales along a distinct climate and ecological gradient in the Chilean coastal range. A current assumption of EarthShape is that all four primary areas share the same tectonic (rock uplift) history, and consequently observed lateral variations in topography and surface processes are solely triggered by climate and biota. Tectonic studies and pilot thermochronological data presented in this proposal suggest that this may not be true – which means that there could be a latitudinal gradient in tectonic forcing, thereby biasing any conclusions about biota-topography-erosion relations. We will apply bedrock low-temperature thermochronology (apatite (UTh)/ He and fission track method) and thermal-kinematic modelling (PECUBE) to reconstruct the Myr-scale tectonic (rock uplift) history of all four primary areas investigated in EarthShape. Results are highly relevant for observational as well as modelling studies investigating large-scale tectonic-climate-biota interactions and landscape evolution (cf. phase II EarthShape proposals: PIs Ehlers and Hickler, Schaller and van der Kruk, Mutz and Niedermeyer). Detrital (tracer) thermochronology will be applied to all primary areas of EarthShape to identify the driving forces of millennial Earth surface processes, such as the links between vegetation cover, geomorphic expression, erosion and sediment transport. This is done by statistically relating the detrital age distributions measured in river sand to the source areas in analysed catchments. Geomorphic and biota metrics will be derived from various remote sensing data. Geomorphic erosion factors will be calculated from digital elevation models (ASTER, LiDAR), whereas vegetation erosion factors will be derived from analysing multispectral satellite data (Sentinel, Landsat) combined with field work. Resulting relative erosion maps will be combined with cosmogenic-nuclide erosion rates (e.g. EarthShape phase I+II, PIs Schereler et al., Schaller and van der Kruk) to derive high-resolution millennial erosion rate maps for all primary areas of EarthShape. We expect that this innovative multi-disciplinary approach (combining thermochronology and remote sensing data) will advance our understanding of tectonic-climate-biota landscape dynamics.