Using the landscape evolution modelling framework Landlab to quantify how soils, climate, and vegetation are linked in semi-arid landscapes

Soils are the interface between the lithosphere and the atmosphere. The presence and thickness of a soil mantle is locally a function of the rate of parent material weathering and the net transport of soil downslope, which are both heavily controlled by the type and density of vegetation present. In semiarid landscapes, water is often both a limiting material to the growth of vegetation as well as additional control on weathering and erosion of soil. The goal of our study is to promote fundamental understanding of the sensitivity of soil thickness to changes in precipitation in these water-limited environments. To accomplish this, we have quantified denudation rates in a semi-arid ecosystem through field work and used these data to inform a variety of climate change simulations in a landscape evolution model.

Our denudation rates were sampled from areas with varying elevation, slope, and aspect, all variables that engender differences in the vegetation of sagebrush steppe ecosystems. The data were collected using a sediment flux measurement technique where a GPS with sub-centimeter accuracy was used to periodically resample the movement of rebar that was installed in the regolith.

Within sagebrush steppe ecosystems, wildfires were historically common before the presence of humans. Contemporarily, after a disturbance invasive species are able to establish themselves more quickly than native plants can, and so fires have a much different effect on our landscapes than they did in the past. With Landlab, an open-source, community framework that supports the rapid development of integrated landscape development models, we have modeled the effect of this shift on landscape evolution. Our model is able to react to shifts in climate by changing the vegetation present and the recurrence interval of fires. We can, therefore, use the model to quantify the linkages between climate, local soil evolution, and landscape evolution under plausible alternative futures of climate.