Lyman Persico Seminar
January 24 @ 3:00 pm - 5:00 pm MST
Bio: Lyman is an associate professor of Geology and Environmental Studies at Whitman College. He received his Bachelor’s from the University of Vermont in Environmental Sciences and Geology and MS and PhD in Earth and Planetary Sciences at the University of New Mexico.
The importance of vegetation and soil development in modulating hillslope response to climate change in the Mojave Desert
Climate exerts an important control on hillslope processes, vegetation cover, soil thickness, and landscape evolution. Hillslopes at a site in the eastern Mojave Desert are mantled by soils derived from weathering of bedrock combined with eolian inputs of fine sand and silt. Sediment from both sources was deposited on the soil surface and incorporated into colluvium, allowing both processes to be dated with optically stimulated luminescence (OSL). OSL ages indicate a period of increased colluviation in the late Pleistocene facilitated by enhanced bedrock weathering by climate-dependent subcritical cracking processes and dust deposition. Hillslope aspect strongly controls soil environments and associated vegetation. Soils with dense grass cover extensively mantle the mesic north-aspect hillslopes, while more xeric south-aspect hillslopes are dominated by desertscrub, thin soils and more extensive bedrock exposure. Remnants of older colluvium with moderately developed soils on south aspects, however, indicate they were once more extensively mantled by thicker colluvial deposits. The transition to drier conditions in the Holocene diminished vegetation cover on more xeric south aspects, triggering widespread erosion, whereas the more mesic north aspects retained more grass cover that minimized erosion. Extensive hillslope grass cover at the late Pleistocene Holocene transition delayed hillslope erosion and valley floor aggradation until the middle Holocene.