Collaborative Research: MRA: Dew impacts on ecosystem carbon, energy and water fluxes at continental scale - a synthesis across NEON sites

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The processes that control carbon and water flows through vegetation are critical land surface feedbacks on a changing climate. While often overlooked, dew formation can generate up to a 25% reduction in the transpiration flux and may improve plant tolerance of drought or heat stress in xeric systems or during dry periods in mesic systems. Furthermore, dew affects the uptake and exchange of gases across the stomata potentially limiting carbon gain, influences plant susceptibility to some pathogen infections, and supports epiphyte communities. Placing a constraint on the importance of dew to these ecosystem processes is critical since larger, but less frequent, rain events and drier air are expected under warming and may generate broad declines in dew inputs. This project will provide the first comprehensive, macroscale assessment of dew impacts on carbon, energy, and water fluxes across xeric to hydric ecosystems. It will generate a new module for dew implementation in land surface models, enabling further investigations of the impacts of dew in research areas ranging from weather forecasting to microbiology. The project will support the development of a new field-based study abroad program on climate and ecosystem resilience in Puerto Rico where students will participate in fieldwork at NEON sites and take part in workshops and discussions with local scientists. The project will support up to 36 undergraduate students for this, who will be recruited primarily from a minority-serving institution. The project will also support an early career female faculty member as PI, train three PhD students and eight high school students. The formation of dew is a ubiquitous phenomenon that can be an almost daily occurrence in some ecosystems. Dew has a measurable impact on carbon and water fluxes by suppressing transpiration, reducing carbon exchange, and impacting the temperature, albedo, and local vapor pressure deficit (VPD) of the canopy. However, previous work has largely focused on discrete campaigns in arid environments at the leaf or plant level. Here, the first standardized continuous canopy-scale measurement of dew will be generated using infrared radiometry, canopy water content estimates from GPS receivers, and leaf wetness sensors across a hydric to xeric gradient encompassed by the NEON network. The observations will be used for the direct assessment of dew impacts on ecosystem fluxes and for the development and implementation of an ecosystem model that accounts for the effects of dew on surface soil moisture, foliar water uptake, and energy balance. This project will provide fundamental insights into dew impacts on ecosystem processes and a critical constraint on how dew reduction associated with rising temperatures and VPD may exacerbate ecosystem water stress.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.