ORE-CZ: Modeling impacts of salt stress on coupled carbon and water dynamics in dryland critical zones

High salt concentrations in soil, groundwater, and in irrigation water can limit agricultural productivity by increasing plant water stress and limiting carbon uptake, leading to tens of billions of dollars in lost crop production across one-fifth of the world’s irrigated lands. The interactions between vegetation, groundwater, and upper soil layers are influenced by plant water uptake and hydraulic redistribution. Hydraulic redistribution is a process by which plant roots serve to transport water between various soil layers. The role that salinity plays in these interdependencies may vary depending on the vertical distribution of salts in the soil column and specific plant responses, such as salinity tolerance and filtration by the root system. The investigators will conduct experiments and develop models to understand the effects of salinity on water stress in agricultural dryland areas. During this research, the researchers will recruit, train, and facilitate the retention of community college students, who make up over 50% of the engineering student body at Portland State University through research involvement, and they will develop new materials for course-based undergraduate research. This project will employ controlled greenhouse experiments, modeling, and analyses of field data to elucidate how factors such as root and shoot water and salt storage, plant salt uptake, and ionic and osmotic stresses impact total drought and salt induced stress in phreatophytic plant species, thereby impacting carbon and water fluxes in dryland critical zones. The greenhouse experiments will involve measuring plant water transport under salinized conditions to collect data which will aid in the development and parameterization of a new model to predict groundwater-surface water interactions, hydraulic redistribution, water stress, and salt stress under saline conditions. The resulting model predictions of plant transpiration, carbon assimilation, and uptake of salt from various soil layers will be used to evaluate impacts of salinized soil, groundwater, and irrigation water on carbon and water cycling in salt-affected dryland ecosystems in the Rio Grande Valley. Investigators will collaborate with the Drylands Critical Zone Network cluster to synthesize model results with data collected from existing salt-affected pecan orchards to provide insights into water use efficiency, management strategies, and long-term sustainability. The project will facilitate the training and mentoring of undergraduates and community college students at Portland State University. 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.