Network Cluster: Patterns and controls of ecohydrology, CO2 fluxes, and nutrient availability in pedogenic carbonate-dominated dryland critical zones

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The Critical Zone is the layer of Earth’s surface from the top of the trees to the bottom of the groundwater. Rocks, soil, water, air, and living organisms interact in the Critical Zone to provide life-sustaining resources such as food and water. Drylands, with arid to semi-arid climates, cover 45% of the Earth and provide homes to more than 2 billion people. The drylands of the American West are facing significant challenges caused by global change, such as drought and changing plant communities. Increases in human population and food demand have also converted many natural drylands in this region to irrigated farms. These changes in land use and climate have greatly affected the movement of water, carbon, nutrients and salt through different parts of the drylands. All of these changes impact the sustainability of natural and agricultural ecosystems. This project will investigate these important Critical Zone processes and improve our ability to predict future change. Specifically, this thematic cluster will investigate how carbonate minerals in dryland soils control and impact water, nutrients, salts, and carbon moving in and out of the Critical Zone. This project will help to educate and train middle to high school students, and college undergraduate and graduate students. These students will be provided with the motivation, skills and tools to become future professionals in science, technology, engineering, arts, and mathematics (STEAM). Our research and education efforts will also help to grow public awareness of the importance of the Critical Zone function and service in drylands.The Critical Zone in dryland ecosystems is an understudied but crucial part of the Earth system. It contrasts with mesic areas by having sparse vegetation, limited but dynamic soil moisture, deep water table, low soil organic matter, alkaline pH, and buildup of salt precipitates, especially as pedogenic carbonates that can develop into a thick caliche layer and dominate the soil structure. However, these systems are underrepresented in Critical Zone research and current conceptual models do not fully address phenomena unique to drylands such as development of pedogenic carbonate, dust storms, episodic precipitation, and high spatiotemporal variability in hydrological and biogeochemical processes. To fill these knowledge gaps, the overarching goal of the project is to increase our capacity to quantify and predict dryland carbon budgets across land-use and climatic gradients by examining the role of water and nutrient availability in regulating the movement of organic and inorganic carbon in the dryland Critical Zone. Specifically, this project centers around the multifaceted roles of pedogenic carbonates in dictating vadose zone water dynamics, the potential recharge to deep water table, and nutrient cycling in typical dryland landscapes, piedmont, playa and irrigated agricultural fields. These in turn drive trends in evolution of Critical Zone architectures and land-atmosphere C exchange. We will tackle these problems by using a comprehensive set of tools including eddy covariance towers, deep Critical Zone drilling, hydrogeophysical surveys, soil and hydrologic sensors, isotopic analysis, synchrotron, geochemical proxies, and genetic sequencing. This project builds on the rich historical data, knowledge, and models at the Jornada LTER, the Reynolds Creek CZO, USDA-ARS Kimberly site in Idaho and irrigated agricultural sites along the Rio Grande Valley in Texas. This thematic cluster will develop an interdisciplinary framework to understand material and energy flow through dryland Critical Zones and lay the foundation for managing Critical Zone function, evolution, and services, as well as forecasting carbon budget changes with future shifts in climate and land use in drylands.This project is jointly funded by the Critical Zone Collaborative Network and the Hydrologic Sciences programs in the Division of Earth Sciences and the Hispanic Serving Institutions program in the Education and Human Resources Directorate's Division of Human Resource Development.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.