UC Riverside

The struggles of Angiosperms to deal with the challenges of the vertical ascent of sap have lead to diverse evolutionarily stable strategies that we see today. The strategies of hydraulic transport are multifaceted and coordinated among organs that are highly attuned to the environment, which promotes effective resource acquisition and utilization. In light of the climate changes in the Anthropocene, the plant hydraulic strategies will dictate which plants will tolerate drought and which plants will succumb to drought and ultimately to mortality. A framework to explain plant mortality has been recently proposed where a trade-off exists between plants that utilize profligate hydraulic strategies but are vulnerable to hydraulic failure and plants that utilize conservative hydraulic strategies but are vulnerable to carbon starvation. Currently, the physiological traits that are used in modeling of plant mortality are lacking and such traits are important because they allow greater predictive power in modeling future tropical forest composition and dynamics. The goal of the dissertation is to characterize the hydraulic physiological traits that underpin plant drought response strategies by utilizing plant hydraulic research methods that describe hydraulic architecture and capacities in transport, storage and resistance to dysfunction (i.e. cavitation resistance). Furthermore, the traits are used in conjunction with other techniques that describes how carbon and nutrient dynamics are influenced such as gas exchange and stable isotopes. This dissertation has lead to providing mechanistic evidence for the observed increase in liana abundance in tropical forests, to proposing a novel drought response trait in the form vessel occlusion and its relationship to hydraulic and anatomical traits, and to the application of what we learned in natural systems to assess physiological performance of avocado varieties.