The Department of Soil Science welcomes Dr. Rebecca Lybrand, Assistant Professor, Crop & Soil Science, Oregon State University, Corvallis, as the Bockheim Distinguished Lectureship speaker. Her presentation is entitled “Incipient Weathering in the Critical Zone:Assessing the Bioweathering of Minerals at the Microscale.” Please join us on Wednesday, October 16 at 3:30 pm in Room 270 Soils Bldg. Following Dr. Lybrand’s presentation, there will be a reception in the Jackson-Tanner Commons.
Rock weathering replenishes nutrients in soil, shapes geochemical carbon sequestration, and drives physical, chemical, and biological processes at a multitude of scales. Globally, lithology type and distribution, climate, and ecosystem activity are predictors of mineral weathering rates and long-term carbon cycling. Knowledge deficits exist in understanding how microbes drive incipient mineral transformation in natural environments and how fungal-mineral interactions influence mineral weathering– a critical yet underrepresented component of climate science and nutrient cycling models. Our goal was to examine the effect of microbial activity on transforming granular basalt, granite, and quartz sand (250-53 µm) deployed in natural soil environments. We successfully developed and employed a coupled high-resolution microscopy method to identify incipient weathering features and microbe-mineral interfaces of the granular substrates deployed along a semiarid to humid environmental gradient encompassed by the Catalina Critical Zone Observatory (CZO), AZ and the Calhoun CZO, SC. In parallel, the composition of organic matter interacting with the retrieved rock substrates was identified with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) using two solvents (water, chloroform) with different polarities to sequentially extract a representative fraction of organic materials. Our work confirmed evidence for hyphal tunnelling, organic coatings, and biomineralization in samples after 3 years of field burial. This is the first time helium ion microscopy was coupled with scanning electron microscopy and applied in the earth and ecosystem sciences to assess microbe-mineral interfaces and in situ biological contributors to incipient weathering. The FT-ICR-MS data suggest that the classes of biogeochemical compounds associated with the grains varied by ecosystem and mineral substrate composition. This work contributes to a broader understanding of biologically-mediated weathering across climate and topographic gradients in the critical zone.
Made possible by the generous support of James and Julie Bockheim