Summary

Drought in California and much of the western United States has been severe enough over the last two decades to be considered a mega-drought, possibly the worst in a millenium.  Prolonged drought such as this reduces agricultural yields, and increases forest mortality and wildfire risk.  Despite the importance of tracking vegetation water stress over large areas, monitoring systems that can scale from plots to the globe are lacking.  In this study, doctoral student Krishna Rao, working with Earth System Science professor Alex Konings and other faculty, has developed and tested a proof-of-concept microwave radar system to track the water status of forest plots on the scale of several hectares.  A side-facing transmitter sends electromagnetic waves through the forest plot, and a receiver about 200m away detects them.  The system is based on the idea that the received wave amplitude will be affected by the amount of vegetation water due to its effects on scattering and attenuation of electromagnetic waves. To test the system, the amplitude of received waves is compared with measurements of the water status of individual trees between the transmitter and receiver.  Krishna’s goal for the monitoring system is “an accurate, low-cost, rapidly deployable, and scalable system to measure vegetation water status. Such a system could enable the study of vegetation water in terms of its: 1) global variations, 2) response to changes in climate, 3) link to plant functional types, and 4) influence on terrestrial carbon and water fluxes.”

▶VIDEO: Krishna Rao explains forest hydrology monitoring system

Krishna Rao testing radar system.jpg