Much of my research is in collaboration with the Bedrock Critical Zone Network (BCZN). Here our work centers on better understanding the critical zone (CZ) through various scientific methods. The CZ spans the treetops and air we breathe all the way to the unfractured bedrock beneath our feet. This area shapes the world as we know it today and is the main interface where humans receive vital resources to continue living on the planet (water, nutrients, etc.). For more information on the specific research the BCZN is doing click on the link here

Image: Chorover, J., R. Kretzschmar, F. Garcia-Pichel, and D. L. Sparks. 2007. Soil biogeochemical processes in the critical zone. Elements 3, 321-326. (artwork by R. Kindlimann)

The CZ is challenging to observe because it mostly lies hidden underground. Exposures of the CZ in roadcuts and outcrops comprise a largely untapped resource for exploring CZ heterogeneity, and to address the question, do CZ processes create heterogeneity or destroy it? Weathering processes might be expected to homogenize chemical composition by transforming diverse weatherable bedrock minerals into clays. However, we also might expect near-surface CZ processes to create heterogeneity, through opening fractures, bioturbation, and infiltration of surface water. Which processes dominate? 

We created a “Virtual CZ” (VCZ) by combining physical and chemical measurements at a roadcut that exposes weathered biotite gneiss in a SW Virginia quarry. The VCZ will provide unprecedented views of CZ properties at multiple scales and an interactive, virtual platform for teaching and outreach. LiDAR and photogrammetry data form the base of a 3D model that incorporates geochemical data, ground-penetrating radar (GPR), seismic refraction, and electrical resistivity data. We collected 70 rock samples in two 7 m vertical transects at 20 cm intervals and determined geochemical composition using handheld and benchtop XRF spectrometers. Next we will collect more detailed XRF data, calculate chemical depletion, and perform higher-resolution seismic surveys to better resolve subsurface structure. Overall, we hope to create a virtual model with a simple user interface that will provide new scientific insights and an interactive educational platform to bring CZ science into K-12 and college classrooms.

By absorbing carbon dioxide, mitigating hazards, and providing critical ecosystem resources and biodiversity, trees play a pivotal role in protecting Earth's inhabitants from the impacts of climate change. However, as climate change becomes more extreme, forest degradation increases as wildfires and disease increase. Among those affected are the world’s largest trees, the giant sequoias, which exist in small groves in the Sierra Nevada, CA. While the giant sequoia trees are resilient, the increasing wildfires and tree disease within California have weakened these tree populations. Our group aims to determine what makes these trees resistant to the effects of climate change. Our hypothesis is that the subsurface may be responsible for this resiliency. Such as an increase of fractured bedrock and thicker saprolite layer could help increase water storage for these large trees. Understanding more about sequoia trees' resiliency to fire and disease can inform future generations on how to best protect these groves and replenish the population through planting. Past research on sequoia groves has not focused on the subsurface. There have been no large-scale geophysical surveys imaging the subsurface of the sequoia trees. To fill that knowledge gap, a preliminary seismic study was performed inside the Mariposa Grove of Yosemite National Forest in July of 2023. The study goal was to examine the subsurface within and outside of sequoia groves. We also wanted to examine the overall heterogeneity of the subsurface below sequoia trees and how it connects to weathering and microbes in the soil. To do this, we collected four high- resolution nodal seismic arrays that transect two giant sequoia trees and two fir trees and two 250- meter-long lines, the first crossing a sequoia grove and the second crossing a fir grove. Both survey initial results show a greater depth to bedrock underneath sequoia trees. Overall, seismic imaging shows promising results in further understanding how these large trees impact and are impacted by the subsurface.

Currently we are working on analyzing data collected this past summer!