Collaborative Research: MSB-ENSA: Leveraging NEON to Build a Predictive Cross-scale Theory of Ecosystem Transpiration

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Water is a critical resource that sustains continental ecosystems. Land plants play a critical role in the cycling of water between the continents and atmosphere by extracting water from soils and groundwater and releasing it to the atmosphere as they grow. Existing data suggest that this process, transpiration, accounts for more than half of the global transfer of water from the continents to the atmosphere. Surprisingly little is known about how much water is transpired, how different types of plants and ecosystems govern transpiration, and how properties of ecosystems are shaped by transpiration. This award supports an interdisciplinary group of ecologists, Earth and atmospheric scientists, and engineers to make estimates of plant transpiration across the United States for the first time and use these data to develop models and improve predictions of future plant water use. The team will develop new techniques and datasets benefitting the scientific community and conduct interdisciplinary graduate student training to prepare diverse, next-generation scientists to tackle ecological and data science challenges.The project team will work with a wide range of data products produced by the National Ecological Observatory Network, with a primary emphasis on stable isotope ratios of water vapor and carbon dioxide. Isotope ratios provide an integrated measure of physical processes controlling gas exchange between plant leaves and the atmosphere. The suite of sensors deployed by the Network across the USA provides the first standardized dataset enabling isotope-based estimation of transpiration across a diverse range of continental ecosystems. The project team will develop new calibration procedures and data products from the Network's sensor data and distribute these for use by the broader research community. These data will be integrated with other data collected by the Network and information from field campaigns by the project team, using analysis at a range of spatial scales from individual plots to continental scales to determine how ecosystem structure and plant regulation of gas exchange control transpiration. This knowledge will be integrated into and used to test models for plant water use that reflect the underlying distribution of functional traits and structural properties within the study ecosystem. The models will be used to examine the potential sensitivities of transpiration and ecosystem water use. During the course of its work, the project will develop and disseminate new measurement and data analysis approaches and datasets of broad use to researchers, and will support a graduate short course in spatial sciences.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.