DIGGING DEEPER: PERSISTENCE AND CLIMATE SENSITIVITY OF DEEP SOIL ORGANIC MATTER (Invited Presentation)

Deep soil layers (below 30cm or A-horizon) account for up to 70% of the carbon (C) stored in soils. Decomposition of deep soil organic matter (SOM) contributes to surface carbon dioxide efflux, and is controlled by climate, soil physico-chemical properties, and geomorphology of the landscapes and associated hydrology. This presentation will include synthesis of our past and ongoing projects on deep SOM dynamics, including SOM in weathered bedrock and how climate regulates SOM storage, chemical composition, persistence, and stabilization mechanisms using results from the NSF funded Southern Sierra Critical Zone Observatory, and agricultural systems in California. Our work contributes to improve our: understanding of mechanisms that control deep SOM persistence and ability to predict the vulnerability of soil carbon to climate change.