Collaborative research: Controls of climate and dust on soil chemical erosion and nutrient supply

Soils are a critical component of Earth?s surface environment. They are storehouses of nutrients that sustain life, they provide habitats for plants and animals, and they influence Earth?s climate through their role in the global carbon cycle. This project?s main goal is to quantify how climate and dust affect soil chemical erosion rates and soil?s nutrient content. This is of interest because chemical erosion accelerates landscape evolution and modulates Earth?s climate, and because dust is a key source of nutrients to soils. To investigate these linked phenomena, this project will establish a series of study sites along two altitudinal transects at San Jacinto Peak, California, where nearly 3 km of relief creates a striking climate gradient with a range in mean annual temperature of 18 degrees C. This work will support a team of two early career faculty (one female, both pre-tenure), and will promote diversity initiatives through the support of the PI team, one whom is a member of an underrepresented group (Alaska Native), as well as through the recruitment of students via on-campus programs for students from underrepresented groups. Outreach and education activities will focus on developing resources for middle school teachers in collaboration with experts at the San Diego County Office of Education and the University of Wisconsin Geology Museum.<br/><br/>Despite longstanding expectations that climate should strongly affect chemical erosion rate, quantifying these effects in nature has proven difficult, partly because these rates are difficult to measure, and partly because other factors like lithology and dust can obscure climatic effects. Dust?s impact on soil nutrient supply is likewise an ongoing topic of contention, partly because it depends on rates of soil production and chemical erosion, which are rarely measured in the same places that dust deposition rates are. The proposed work will avoid these issues by combining measurements of chemical erosion rates, climate, and dust deposition rates and provenance at SJP, which spans the largest range in temperature within a single unglaciated lithology in the United States. This will build on previous work by applying novel radiogenic isotope measurements in bedrock, soil, dust and vegetation. These data will quantify the sensitivity of chemical erosion rates to climate and provide new insights into spatial and temporal variations in dust?s impact on soil nutrient supply, which is not well constrained at the seasonal time scales that will be targeted in this work. More broadly, this work has the potential to remove a barrier to understanding how Earth?s topography, surface chemistry, and the dust cycle evolve under spatially variable climates?a common feature of Earth?s mountain ranges. Ultimately, these measurements across one of the most striking climate gradients in the United States should guide future efforts to include climate and dust explicitly in models of the topographic and chemical evolution of the Earth?s surface.<br/><br/>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.