Seeing the Forest (and Rock) Through the Trees
Dr. Matt Rossi takes on three big questions:
1) Is there a topographic signature of life? 2) Is there coevolution of forest structure and bedrock exposure in the Rampart Range (CO)? 3) Can landscape evolution models simulate these dynamics?
Date: 3/8/22
Location: Zoom & SEEC 372 A/B
Speaker: Matt Rossi
Abstract: The search for a topographic signature of life has inspired many, though observations increasingly suggest that both biotic and abiotic processes produce the same kinds of landforms. Instead, the imprint of life on topography may lie in the prevalence and scale of landforms. To this point, I will show an example here where forest dynamics that operate over decades to centuries dictate patchy soil patterns that evolve over millennia to millions of years. Trees have long been expected to play myriad roles in the long-term evolution of hillsides. Where soils are thin, trees impact soil production rates (e.g., via root growth at the soil-bedrock interface), soil cohesion (e.g., via stabilizing the soil matrix), runoff generation (via plant water use), and sediment transport (e.g., via tree throw). However, such complex interactions beg important questions as to how topography reflects modern forest structure and whether the geomorphic transport laws we use to simulate landscape evolution are sufficient to capture the role of forests on hillside morphology. Specifically, I will use a natural experiment from the Rampart Range, CO where forest and surface properties vary as a function of elevation and aspect to explore these questions. Using airborne lidar and drone photogrammetry, I show the importance of quantifying surface properties at the individual tree and outcrop scale. These process-scale measurements motivate the need for new numerical models of hillside evolution that can distinguish between biotic and abiotic mechanisms for soil production and sediment transport.
Bio: Matthew Rossi is a geomorphologist at Earth Lab who is interested in developing a quantitative understanding of the processes and process interactions that sculpt the Earth’s surface. His research largely focuses on the relative roles of climate, tectonics, material properties, vegetation, and hydrology on setting the form and function of rivers and hillslopes. He received his B.S. in Geology at the College of William and Mary (2003) and his Ph.D. in Geological Sciences from Arizona State University (2014).
