Ecology Research Seminar: Candidate for Plant Physiological Ecologist, Henry Adams
- Thursday, February 14, 2019 from 3:30pm to 4:30pm
- Lewis Hall, 304 - view map
The Department of Ecology welcomes Dr. Henry Adams, Candidate for Plant Physiological Ecology Faculty, to campus as he presents his research seminar, "The ecophysiology of drought-induced tree mortality." Dr. Adams is an Assistant Professor in the Department of Plant Biology, Ecology, & Evolution at Oklahoma State University.
Widespread tree mortality from drought has been observed on all forested continents, has significant effects on ecosystem function, and is poorly represented in vegetation models – but we can expect to see more of this disturbance with climate change. I will describe my research on physiology of drought-induced tree mortality, its sensitivity to temperature, and determination of lethal thresholds in tree hydraulic function. In glasshouse and growth chamber experiments with pine seedlings and saplings, I found that trees under higher temperatures died faster during drought. Using difference in time-to-mortality, I explored the implications of temperature sensitivity for the frequency widespread die-off in a warmer world, using an empirical model. I demonstrated how linear responses in temperature sensitivity can cause progressive increases in die-off, due to the non-linear frequency distribution of drought duration. However, better projections of tree mortality could result from mechanistic, process-based models based on the physiological process of tree death from drought. I analyzed physiological data that relate to proposed tree mortality mechanisms of hydraulic failure and carbon starvation from my own experiments, and by building a global dataset of similar tree-killing experiments and observational studies. I found that xylem hydraulic failure was ubiquitous across multiple taxa, as all species assessed had 60% or higher loss of xylem hydraulic conductivity at death. Responses of non-structural carbohydrate reserves at mortality were diverse and though data consistent with carbon starvation was common, it was not universal. Focusing on hydraulic failure, subsequent research pivots from describing the results of death to characterizing risk factors and lethal thresholds across a range of tree drought stress. In a re-watering experiment led by my PhD student, we found that the level of xylem embolism resulting in 50% mortality was higher than expected, but surprisingly similar for two species that vary greatly in drought tolerance.