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K-State Today

October 5, 2017

Division of Biology presents Henry Adams on Oct. 6

By Division of Biology

Henry Adams, Oklahoma State University, will present "Life and Death of Trees on the Dry Forest Edge" as part of the Division of Biology seminar series at 4 p.m. Friday, Oct. 6, in 221 Ackert Hall.

The lecture will cover widespread tree mortality associated with drought that has been observed on all forested continents, and global change is expected to cause additional forest disturbance. Tree mortality and die-off has implications for future biosphere-atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models.

In Adams' seminar, he will describe his research on the temperature sensitivity, physiological mechanism, and interactions with tree-killing fungi of drought-induced tree mortality. In a glasshouse experiment with pinyon pine saplings, he demonstrated that tree under a ~+4°C temperature increase from ambient conditions died 28 percent faster. Using this difference in time-to-mortality, Adams has explored the implications of this temperature sensitivity for the frequency widespread die-off in a warmer world. Using a simple empirical model he estimated that this could cause a fivefold increase in die-off frequency, due to the nonlinear frequency distribution of drought duration. However, better projections of tree mortality could result in process-based models based on physiological processes and mechanisms of tree death from drought. Adams analyzed physiological data that relate to the proposed tree mortality mechanisms of hydraulic failure and carbon starvation from his own experiment, and from a global dataset of similar tree-killing experiments and observational studies. He demonstrates that xylem hydraulic failure was ubiquitous across multiple tree taxa and that all species assessed had 60 percent or higher loss of xylem hydraulic conductivity at drought-induced mortality. Responses of nonstructural carbohydrate reserves at mortality were diverse, and data consistent with carbon starvation was common, but not universal.

He also will discuss ongoing experimental work to determine the lethal threshold in loss of xylem conductivity for death by hydraulic failure in loblolly pine. In the final portion of his presentation he documents a surprising amount of recent tree death associated with drought and infection by the canker-causing hypoxylon fungus for two oak species at a site in the Crosstimbers ecoregion of Oklahoma. Adams will discuss how this fungal affection could influence tree vulnerability and physiological mechanism of mortality.

If you would like to visit with Adams, please contact Jesse Nippert at nippert@k-state.edu