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Physical Foundations in Equivalent Water Thickness and Crop Water Stress Detection
Abstract
Monitoring crop water stress is critical to develop strategies for improving crop productivity and for mitigating water stress damage. The common means of monitoring crop water stress includes field crop measurement (e.g., leaf water potential and relative water content), Climate observation (e.g., soil moisture and precipitation), and Remote sensing data (e.g., vegetation indices). Equivalent Water Thickness (EWT), defined as the ratio of water mass to leaf area (leaf EWT) or ground area (canopy EWT), has been used as a direct field measurement of the vegetation water status and has shown to be measurable by remote sensing data. Therefore, there is increasing interest in the potential use of EWT in important economic crops (e.g., corn and soybean) for water stress detection. However, the utilities of crop EWT and water stress detection lack the physical foundation on three domains: responsive characteristics to environmental changes and plant physiological processes, limitations and advantages of remote sensing estimation at multiple spatial scales, and mechanism of the standardized anomalies in various drought conditions and their associations with vegetation indices. This dissertation is organized into five chapters. Chapter I introduced the dissertation's background, research objectives, and knowledge gaps. Chapter II examined the relationships between canopy EWT with latent heat flux, soil water content, vapor pressure deficiency, and leaf EWT with their associated leaf area index, gross primary productivity, and latent heat flux. Chapter III presented the heterogeneity of leaf EWT vertical distribution and the accuracy of remote sensing estimations in field scales. Finally, chapter IV showed the correspondences between canopy EWT standardized anomalies of corn and soybean with the United States Drought Monitor and their correlations with the Standardized Precipitation-Evapotranspiration Index. This chapter also presented the associations between Landsat 8 vegetation indices and leaf EWT standardized anomalies. Finally, chapter V summarizes the key findings of this dissertation. In summary, this dissertation has provided physical foundations in the EWT of corn and soybean and insight into crop water stress detection remote sensing.
Subject Area
Environmental science|Remote sensing|Agriculture
Recommended Citation
Ou, Wenqi, "Physical Foundations in Equivalent Water Thickness and Crop Water Stress Detection" (2023). ETD collection for University of Nebraska-Lincoln. AAI30528457.
https://digitalcommons.unl.edu/dissertations/AAI30528457