Abstract
Abstract. We present a numerical modeling investigation into the interactions between transient climate and vegetation cover with hillslope and detachment limited fluvial processes. Model simulations were designed to investigate topographic patterns and behavior resulting from changing climate and the associated changes in surface vegetation cover. The Landlab surface process model was modified to evaluate the effects of temporal variations in vegetation cover on hillslope diffusion and fluvial erosion. A suite of simulations were conducted to represent present-day climatic conditions and satellite derived vegetation cover at four different research areas in the Chilean Coastal Cordillera. These simulations included steady-state simulations as well as transient simulations with forcings in either climate or vegetation cover over millennial to million-year timescales. Two different transient variations in climate and vegetation cover including a step change in climate or vegetation were used, as well as 100 kyr oscillations over 5 Myr. We conducted eight different step-change simulations for positive and negative perturbations in either vegetation cover or climate and six simulations with oscillating transient forcings for either vegetation cover, climate, or oscillations in both vegetation cover and climate. Results indicate that the coupled influence of surface vegetation cover and mean annual precipitation shifts basin landforms towards a new steady state, with the magnitude of the change being highly sensitive to the initial vegetation and climate conditions of the basin. Dry, non-vegetated basins show higher magnitudes of adjustment than basins that are situated in wetter conditions with higher vegetation cover. For coupled conditions when surface vegetation cover and mean annual precipitation change simultaneously, the landscape response tends to be weaker. When vegetation cover and mean annual precipitation change independently from one another, higher magnitude shifts in topographic metrics are predicted. Changes in vegetation cover show a higher impact on topography for low initial surface cover values; however, for areas with high initial surface cover, the effect of changes in precipitation dominate the formation of landscapes. This study demonstrates the sensitivity of catchment characteristics to different transient forcings in vegetation cover and mean annual precipitation, with initial vegetation and climate conditions playing a crucial role.
Highlights
Plants cover most of the Earth’s surface and interact chemically and physically with the atmosphere, lithosphere, and hydrosphere
Results indicate that the coupled influence of surface vegetation cover and mean annual precipitation shifts basin landforms towards a new steady state, with the magnitude of the change being highly sensitive to the initial vegetation and climate conditions of the basin
This study demonstrates the sensitivity of catchment characteristics to different transient forcings in vegetation cover and mean annual precipitation, with initial vegetation and climate conditions playing a crucial role
Summary
Plants cover most of the Earth’s surface and interact chemically and physically with the atmosphere, lithosphere, and hydrosphere. With the rise of new techniques to quantify mass transport from the plot-scale to the catchment-scale, and the emergence of improved computing techniques and landscape evolution models, research has shifted more towards building a quantitative understanding of how biota influence both hillslope and fluvial processes (Stephan and Gutknecht, 2002; Roering et al, 2002; Marston, 2010; Curran and Hession, 2013) These previous studies motivate the companion papers presented here. This study does not explicitly present landscape evolution model results “calibrated” to these specific areas, we have chosen the model input (e.g., precipitation, initial vegetation cover, rate of tectonic rock uplift) to represent these areas This has been done in order to provide simulation results that represent the nonlinear relationship between precipitation and vegetation cover (e.g., Fig. 1b, c) over a large climate gradient. Topographic metrics were extracted from a 30 m resolution digital elevation model from the NASA shuttle radar topography mission (SRTM), and vegetation related datasets from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data (https://landcover.usgs.gov/ green_veg.php, last access: 7 August 2018) (Broxton et al, 2014)
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