The Unstable Relationship Between Drought Status and Leaf Water Content Complicates the Remote Sensing of Tree Drought Stress.

Abstract

Remote sensing holds promise for ecosystem-level monitoring of plant drought stress but is limited by uncertain linkages between physiological stress and remotely sensed metrics of water content. Here, we investigate the stability of relationships between water potential (Ψ) and water content (measured in situ and via repeat airborne VSWIR imaging) over diel, seasonal, and spatial variation in two xeric oak tree species. We also compare these field-based relationships with ones established in laboratory settings that might be used as calibration. Due to confounding physiological processes related to growth, both in situ and remotely sensed metrics lacked consistent relationships with stress when measured across space or through time. Relationships between water content and physiological drought stress measured over the growing season were stronger and more closely related to established laboratory-based drydown methods than those measured across space (i.e., between wet trees and dry trees). These results provide insight into the utility of "space for time" approaches in remote sensing and demonstrate both important limitations and the potential power of high temporal resolution remote sensing for detecting drought stress.

Plant phenotyping relevance

樹木の干ばつストレスを対象に、航空機VSWIR画像による含水量推定と水ポテンシャルとの関係を時空間的に検証しており、リモートセンシング手法の妥当性・限界評価が中心です。

Code and data availability

The paper's Data Availability Statement explicitly deposits the study's data and analysis code on Zenodo (DOI 10.5281/zenodo.15110087), and the AVIRIS-NG reflectance data used for the canopy water content analysis is publicly archived at ORNL DAAC (DOI 10.3334/ORNLDAAC/2376). Both are paper-specific, public, and match