RAPID: Mapping drought stress and hydraulic refugia with repeat hyperspectral data

Increasing droughts accompanied by heat waves that are associated with climate change are harming ecosystems and economies worldwide. This project takes advantage of a unique time series of remote sensing images being produced by NASA and an ongoing drought in southern California to develop new techniques for mapping and monitoring plant drought stress.

Detailed measurements of plant drought stress, plant water use and plant water source (e.g. surface soil or groundwater) will be linked to remotely sensed measurements of plant water content to develop methods for remotely monitoring drought stress. These methods will be used to identify areas of drought resilience and drought vulnerability on the landscape during the ongoing drought, and will facilitate global drought monitoring for agriculture, forestry and water resource management using satellites being launched in the near future.

This project will also train graduate and undergraduate students and provide the foundation for new field-based undergraduate courses at the University of California, Santa Barbara.

This project seeks to understand spatial variation in drought stress with unprecedented spatial and temporal granularity. The project takes advantage of unique repeat airborne hyperspectral imagery from the NASA Surface Biology and Geology High Frequency Timeseries Pathfinder mission March-June of 2022 that coincides with an ongoing prolonged drought in southern California.

The proposed research framework will tackle some of the key outstanding questions surrounding drought-induced tree mortality, subsurface water access, and variations in stress resistance within a species. Detailed physiological measurements on two species of oak trees across topographic and edaphic gradients in water availability will be linked to remotely sensed metrics of plant canopy water content and leaf water content to follow the development of drought stress in thousands of trees across the landscape during the spring dry down.

This will increase understanding of how water stress develops spatially and identify landscape features such as topo-edaphically vulnerable sites and hydraulic refugia that likely have access to rock water. Rigorously linking ground-based measurements of physiological stress to hyperspectral airborne imagery at high temporal resolutions will provide the tools to understand topographic, geomorphic, and ecohydrological controls on plant drought stress, and develop methods for global drought monitoring using upcoming hyperspectral satellite missions.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.