Radar can now detect tree water stress in forests, opening new monitoring tools
Researchers have demonstrated that radar signals can measure water content and stress in trees by analyzing how radio waves bounce through forest canopies. The breakthrough could enable cheaper, faster forest monitoring for climate adaptation, agriculture, and environmental management—without needing sensors on individual trees.
Originaltitel: Relations Between P- To L-Band Radar Tomography and Sub-Daily Tree Water Dynamics in a Boreal Forest
<p>In this study, for the first time, sub-daily radar reflectivity variations are compared with a hydraulic forest model. Multi-polarimetric time series at P- to L-band (435, 600 and 1270 MHz) over a coniferous boreal forest stand, acquired by the BorealScat-2 tomographic tower radar, are analyzed. Attenuation was measured by observing a large trihedral reflector in the forest. The hydraulic forest model was parameterized based on tree sensor data, and driven by evapotranspiration measurements. The forest canopy reflectivity is found to co-vary mainly with the crown water potential and content at P-band, and with the attenuation at L-band. A frequency dependence is apparent, with a positive linear relation at P-band transitioning to a negative nonlinear relation at L-band. The attenuation co-varies mainly with the stem water potential and content at P-band, while it varies in between that of the crown and stem at L-band. In conclusion, it is shown that radar can be used to sense forest hydraulic properties, with prospects of possibly driving forest hydraulic models.</p>