Thermography captures the differential sensitivity of dryland functional types to changes in rainfall event timing and magnitude

Authors: JAVADIAN, M. - University Of Arizona; Scott, Russell - Russ; Biederman, Joel; ZHANG, F. - University Of Arizona; FISHER, J.B. - Chapman University; REED, S. - Us Geological Survey (USGS); POTTS, D.L. - State University Of New York (SUNY); VILLARREAL, M.L. - Us Geological Survey (USGS); FELDMAN, A.F. - National Aeronautics And Space Administration (NASA); SMITH, W.K. - University Of Arizona

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2023
Publication Date: 9/7/2023
Citation: Javadian, M., Scott, R.L., Biederman, J.A., Zhang, F., Fisher, J., Reed, S., Potts, D., Villarreal, M., Feldman, A., Smith, W. 2023. Thermography captures the differential sensitivity of dryland functional types to changes in rainfall event timing and magnitude. New Phytologist. 240(1):114-126. https://doi.org/10.1111/nph.19127.
DOI: https://doi.org/10.1111/nph.19127

Interpretive Summary: The southwest United States is rapidly warming, and rainfall is becoming less frequent and more intense, with major yet poorly understood implications for how ecosystems are going to respond. Thermal camera-based estimates of plant temperature can be integrated with air temperature to infer changes in plant functioning. However, very few studies have evaluated plant temperature dynamics grassland ecosystems. We address this gap by incorporating frequent thermal imaging into a field-based precipitation manipulation experiment in a semi-arid grassland to investigate the impacts on grass functioning using the imagery. We found that fewer/larger precipitation events led to cooler plant temperatures compared to that of many/smaller precipitation events and that perennial grasses were cooler than annuals under the fewest/larger events. We show these patterns were driven by: 1) Increased and consistent soil moisture availability in the deeper soil layers in the fewest/larger treatment; and 2) deeper roots of perennials providing access to deeper plant available water. Our findings highlight the potential for frequent, high resolution thermal cameras to quantify the differential sensitivity of plant functional groups to soil water availability. Detecting these sensitivities is vital to understanding the hydrological and ecological implications of climate change.

Technical Abstract: Drylands of the southwestern United States are rapidly warming, and rainfall is becoming less frequent and more intense, with major yet poorly understood implications for ecosystem structure and function. Thermography-based estimates of plant temperature can be integrated with air temperature to infer changes in plant physiology and response to climate change. However, very few studies have evaluated plant temperature dynamics at high-spatiotemporal-resolution in rainfall pulse-driven dryland ecosystems. We address this gap by incorporating high-frequency thermal imaging into a field-based precipitation manipulation experiment in a semi-arid grassland to investigate the impacts of rainfall temporal repackaging. All other factors held constant, we found that fewer/larger precipitation events led to cooler plant temperatures (1.4°C) compared to that of many/smaller precipitation events. Perennials in particular were 2.5°C cooler than annuals under the fewest/largest treatment. We show these patterns were driven by: 1) Increased and consistent soil moisture availability in the deeper soil layers in the fewest/largest treatment; and 2) deeper roots of perennials providing access to deeper plant available water. Our findings highlight the potential for high-spatiotemporal-resolution thermography to quantify the differential sensitivity of plant functional groups to soil water availability. Detecting these sensitivities is vital to understanding the ecohydrological implications of hydroclimate change.