Felix et al. (2025) Probing Early and Long-Term Drought Responses in Kauri Using Canopy Hyperspectral Imaging

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Remote Sensing
• Year: 2025
• Date: 2025-12-03
• Authors: Mark Jayson B. Felix, Russell Main, Michael S. Watt, Taoho Patuawa
• DOI: 10.3390/rs17233914

Research Groups

Information not provided in the given text.

Short Summary

This study assessed the effectiveness of multitemporal canopy-scale hyperspectral imaging for detecting water stress in kauri trees under controlled and field conditions, demonstrating its capacity for early and sensitive stress detection within one week of drought initiation.

Objective

• To assess the utility of multitemporal canopy-scale hyperspectral imaging to characterise water stress in kauri (Agathis australis) trees under both controlled nursery and field conditions.

Study Configuration

• Spatial Scale: Canopy-scale of individual juvenile kauri trees.
• Temporal Scale: 10-week controlled-environment experiment; field assessment across multiple time points; stress signatures detectable within one week.

Methodology and Data

• Models used: Not applicable in the sense of large-scale environmental models (e.g., ISBA, mHM). Analytical methods involved time-series analysis of narrow band hyperspectral indices (NBHIs), including pigment-specific indices (e.g., Pigment Specific Simple Ratio Carotenoid (PSSRc), Carotenoid Reflectance indices (CRI700, CRI550)) and structural indices (e.g., Normalised Difference Vegetation Index (NDVI)).
• Data sources: Multitemporal canopy-scale hyperspectral imaging; measurements of stomatal conductance and assimilation; soil volumetric water content.

Main Results

• In controlled conditions, physiological responses (reductions in stomatal conductance and assimilation) emerged after three weeks, whereas hyperspectral stress signatures were detectable within one week after drought initiation.
• Early hyperspectral sensitivity was driven by structural and pigment-related indices, with pigment-specific indices becoming dominant predictors as stress progressed.
• These findings were consistent between controlled and field-based experiments.
• Variation in leaf equivalent water thickness (EWT) was strongly explained by pigment-sensitive indices (PSSRc, CRI700, CRI550), accounting for approximately 87% of the variance.
• Structural indices like NDVI also ranked among the top 20 predictors but had comparatively lower explanatory power (less than 75%).
• Overall, canopy-based hyperspectral imaging provides early, sensitive, and consistent detection of water stress in kauri.

Contributions

• Demonstrates a scalable approach for early and sensitive monitoring of drought impacts on kauri, a long-lived endemic tree species.
• Provides a foundation for developing operational forest health tools to address increasing climate pressure.
• Highlights the superior early detection capability of hyperspectral indices compared to traditional physiological measurements for water stress.

Funding

Information not provided in the given text.

Citation

@article{Felix2025Probing,
  author = {Felix, Mark Jayson B. and Main, Russell and Watt, Michael S. and Patuawa, Taoho},
  title = {Probing Early and Long-Term Drought Responses in Kauri Using Canopy Hyperspectral Imaging},
  journal = {Remote Sensing},
  year = {2025},
  doi = {10.3390/rs17233914},
  url = {https://doi.org/10.3390/rs17233914}
}