Collaborative Research: Climate effects on Mn oxidation states in soils and Mn/SOM interactions

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This research project seeks to understand the role that the element manganese (Mn) plays in driving the degradation of soil organic matter (SOM). Mn takes multiple chemical forms in the soil, depending on oxygen availability and acidity in the soil; some of these forms are more active in driving the degradation of SOM than others. This proposed research will use a combination of high-technology tools to evaluate the forms of Mn, and experiments to evaluate the interactions of these forms with SOM and with the populations and activity of soil bacteria and fungi. The project will also afford research training opportunities for undergraduate and graduate students and opportunities to broaden participation of members of underrepresented groups in science, including community outreach to Native Hawaiians. SOM is the largest pool of potentially active carbon (C) in the biosphere, but much of that C turns over slowly because it is chemically recalcitrant and/or physically protected. Mn can override this recalcitrance, driving SOM breakdown through multiple pathways that relate to its three oxidation states. This project will evaluate how the oxidation state of Mn varies as a function of rainfall, and how the different oxidation states of Mn drive the decomposition of SOM. Fieldwork will take place on a well-defined precipitation gradient in the Hawaiian Islands, on which most potential controls of ecosystem processes can be held relatively constant while climate varies widely (from 300 mm/yr annual precipitation to 3200 mm/yr) and in well-defined ways; it also draws upon information from National Ecological Observatory Network (NEON) and other sites to evaluate Mn oxidation states and their implications in a broad range of sites that differ in other factors in addition to precipitation, as a test of the hypothesis that precipitation is the dominant driver of Mn oxidation states and its consequences to SOM stability. This project will build upon an ongoing partnership with a Native Hawaiian community organization (Ulu Mau Puanui [UMP]) that is restoring a traditional agricultural system at the same field sites will be used in this research project. Scientists and students in this project will work with UMP to develop curricula and to reach many of the 600+ learners (about half of whom are Native Hawaiian) who visit the site each year; it will also collaborate with Native Hawaiian scientists to evaluate the role of Mn in traditional Hawaiian agricultural systems. The project will include undergraduate and graduate students who belong to underrepresented groups in science. Finally, the project will take part in a well-established summer program at the University of Wyoming to broaden participation of members of underrepresented groups in science.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.