2019 ASHS Annual Conference

Recent climate and decadal downscaling of global climate models reinforce a trend towards more extreme drought and high temperatures. The gradient of hydric behavior will affect how horticultural species growth and water use respond to more extreme temperatures and drought. At one end is isohydric behavior that closes stomates to reduce transpiration and soil water depletion, and maintain less negative internal tension, but at the cost of reduced photosynthesis. At the other is anisohydric behavior that maintains high transpiration and photosynthesis at the cost of negative internal water tension and soil water depletion. More extreme temperatures and drought may affect horticultural species trending isohydric by limiting potential growth and potential carbon fertilization effect. Anisohydric trending species may tolerate higher temperatures and benefit from high atmospheric CO2, but may be at more risk of stress and poor performance due to greater soil water depletion and extended drought when non irrigated

Roger Kjelgren’s area of expertise is tree physiology, with an emphasis on canopy level interactions with the atmosphere. He spent 25 years at Utah State University studying tree water use, drought stress, and urban water conservation. He is currently director of the University of Florida Mid Florida Research and Education Center in Orlando, still dabbling in water use research to keep his sanity.