41 Biogeochemical Cycling of Elements at the Earth’s Surface Across Space and Time (Posters)

Friday, 21 March 2025
1:00 PM - 5:00 PM
Shenandoah ABC

HILLSLOPE ASPECT CONTROLS ON BIOTURBATION IN THE BLUE OAK RANCH RESERVE, CALIFORNIA TRACED WITH 137CS

Paper number: 41-5
Program: Theme Sessions
Time: 1:00 PM – 5:00 PM

Authors

Abstract

Hillslope aspect is known to affect microclimate conditions in soils worldwide. On semi-arid landscapes, in particular, hillslope aspect controls soil moisture, affecting vegetation cover and thus sediment transport. However, the specific effects that hillslope aspect has on bioturbation, a key driver of hillslope diffusion and thus landscape evolution, have not been measured. Here we study how burrowing mammals, such as tunneling ground squirrels, affect the transport and diffusion of 137Cesium on hillslopes in the Blue Oak Ranch Reserve, California. Eight total soil cores were collected from a north and a south-facing slope; two were collected on each hill's ridge, one at each mid-section, and one at each toe. The cores were then sub-sectioned based on depth, packed, and analyzed for 137Cs activity using gamma spectrometry, as 137Cs is a powerful tracer of soil transport. Results so far show sharper 137Cs peaks in the top 10 cm of soil on south-facing slopes, indicating reduced diffusion, possibly from reduced burrowing activity. North-facing slopes show more variability in 137Cs activity through the vertical profile, likely due to bioturbation. These findings may suggest aspect-driven variation in bioturbation and sediment transport mechanisms in a local system. This research will be advanced by analyzing more soil profiles, coupling 137Cs measurements with soil carbon, and comparing diffusion rates across slopes and varying parts of the hills. Studying these processes in a semi-arid region prone to increased drought and wildfire frequencies is critical for understanding landscape evolution and predicting responses to climate change.

Geological Society of America Abstracts with Programs. Vol. 57, No. 2

doi: 10.1130/abs/2025SE-408583

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.