Faculty Affairs and Academic Programs
Pedro Martinez
Life Sciences; Agriculture and Veterinary Sciences
Environmental Science
UC Riverside
Soil-Landscape Evolution of Vernal Pools in Southern California
Vernal pools are seasonal wetlands that host unique biodiversity composed of endemic flora and fauna. Although soils control the hydrology that underpins this biodiversity, the genesis of soils in vernal pool remains unknown. This project aims to investigate the coupled evolution of soils and geomorphology in vernal pools at the Santa Rosa Ecological Reserve in Southern California. Previous studies identified Vertisols (i.e. clay-rich soils with pronounced shrink-swell properties) in vernal pools where cobble-sized stones cover 35 to 50% of the soil surface. The question addressed in this proposal is why do vernal pools exhibit such high concentration of stones on the soil surface? Two competing hypotheses will be tested: (1) cobbles have slowly migrated upward over time through shrink-swell activity during Vertisol formation, or (2) cobbles were lifted in unison from the underlying bedrock by sediments deposited around and under the cobbles as the basin filled in. The second hypothesis invokes a mechanism analogous to desert pavement formation but driven by water-borne rather than aeolian erosion. To test these hypotheses, cosmogenic nuclide dating analyses of cobbles from soil surface will be performed. If the cosmogenic dates of cobbles on soil surface are similar, then the second hypothesis would be favored, but if dates are significantly different, it would favor the first hypothesis. The results will provide new insights into whether these landscapes are actively forming nowadays or represent relict features. The findings will advance understanding of landscape evolution and inform the conservation of one of California’s most threatened ecosystems.
