DISSERTATION RESEARCH: Plant response to water availability and drought in a changing world

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Drought has been increasing in frequency and severity worldwide for the last 60 years, and the increase is expected to continue over the next several decades. Extreme drought events are already taking their toll on trees and other woody plants all over the world, leading to widespread forest mortality. As greenhouse gas emissions continue to rise on a global scale, the importance of forests increases, as trees can take up carbon dioxide and store it for centuries in the form of wood. However, the death of trees during drought reduces how much can be taken up and increases the amount of carbon dioxide released back into the air when dead trees decompose. This Doctoral Dissertation Improvement Grant will provide funds to evaluate which kinds of plants are more susceptible to drought, and the mechanisms that determine plants? vulnerability to extreme drought events. This research has the potential to reveal characteristics that make woody plants more or less tolerant to drought and may increase the ability to predict species? responses to extreme drought events. The results will inform local land managers and policy-makers on which tree species are more tolerant to drought and therefore improve plans for restoration and management of forests in the face of increasing drought severity. This project will use novel methods to determine the resistance of woody plants to extreme drought using plant anatomical features and physiological measurements. The major cause of tree mortality from drought is embolism accumulation in the water-conducting pipes of plants that obstruct proper water movement from the soil up to the leaves. The researchers will study which anatomical traits make plants more susceptible to embolisms. This work will be conducted in both dry and wet temperate and tropical forests to provide information on how plants growing under different rainfall environments respond to drought. The project will include workshops with public primary school teachers in rural Northwestern Costa Rica, which is an area with a history of extreme droughts that have resulted in widespread forest mortality. These workshops will enhance Costa Rican primary school curriculum through active learning of how plants obtain and use water and the impact of drought on native forests.