A unified framework of modeling transpiration responses to water stress in the US Midwest
Plant responses to water stress have been a major uncertainty in predicting terrestrial ecosystem sensitivity to drought. Different theories have been developed to represent plant water stress. However, the relationships between these approaches, and their underlying connections to ecohydrologic processes, are not sufficiently understood. In this dissertation, I first proposed a unified theoretical framework that reconciles the relationships between different theories and helps identify the water stress characteristics and the most efficient modeling approach for different environmental conditions. I then applied the framework to the US Midwest and demonstrated the importance of plant hydraulic transport in crop responses to severe atmospheric dryness. I then investigated the monitoring of a critical stress factor, soil moisture, at sub-field levels using extensive fieldwork and satellite data, thus informing a new integrative approach for high-resolution soil moisture estimation. Finally, I used the state-of-the-art satellite evapotranspiration data to constrain and improve land surface modeling at high resolutions. This dissertation work contributes to an improved understanding of plant water stress and better monitoring and management of a more sustainable agroecosystem.
