Frost, Heatwaves and Declining Water Tables: Is There a Super Cottonwood Genotype That Can Cope With All Three?
Kevin R Hultine1*, Davis Blasini2, Dan F Koepke3
1Department of Research, Conservation and Collections, Desert Botanical Garden, Phoenix Arizona, USA
2Department of Research, Conservation and Collections, Desert Botanical Garden, Phoenix Arizona, USA
3Department of Research, Conservation and Collections, Desert Botanical Garden, Phoenix Arizona, USA
A major challenge with managing riparian ecosystems in the 21st century is that climate conditions are becoming more extreme such that heatwaves, droughts, and even episodic freezing events are more frequent and catastrophic. Thus, locally adapted plant populations may soon become maladapted as a consequence of rapid climate change. Among the most important and potentially most sensitive of native riparian trees species is Fremont cottonwood that occupies a broad climatic range across the southwestern U.S. This talk highlights a suite of plant traits that when expressed as a whole, we believe will result in cottonwood genotypes that are best suited to cope with the effects of climate change and subsequent resource limitation. We focus on four primary structural / functional trait suites: 1) foliage phenology, 2) leaf morphology, 3) above-ground hydraulic architecture, and 4) xylem structure and function. Data collected from an experimental common garden in central Arizona revealed evidence for strong local adaptation such that cold-adapted genotypes express a suite of traits that maximized tolerance and avoidance to freeze exposure, whereas warm-adapted genotypes express traits that minimize thermal stress from heat exposure. Importantly, cottonwood genotypes from both cold and warm regions expressed a high degree of seasonal phenotypic plasticity that may underscore their capacity to survive multiple stressors related to freezing, heat stress, and declining water tables. Although there are no magic bullets for managing riparian forests in the face of climate change, trait-based ecological solutions described here, may have the potential to produce desired outcomes in riparian restoration under rapidly evolving environmental conditions.