Synthetic aperture radar sensitivity to forest changes: A simulations-based study for the Romanian forests

Area of Science:

• Earth Observation
• Forestry Science
• Remote Sensing

Background:

• Forest ecosystems face increasing threats from natural and human-induced disturbances.
• Effective forest condition monitoring requires continuous, reliable, and accurate systems for early warnings.
• Integrated Earth Observation systems are crucial for assessing forest health and detecting changes.

Purpose of the Study:

• To evaluate the utility of C-, L-, and P-band synthetic aperture radar (SAR) sensors for monitoring forest condition.
• To assess the sensitivity of different SAR bands to vegetation water content, leaf area index, and forest disturbances.
• To inform the development of integrated Earth Observation monitoring systems for European forests.

Main Methods:

• Utilized state-of-the-art electromagnetic simulation models.
• Simulated SAR sensor responses (C-, L-, and P-band) for Romanian beech, oak, and coniferous forests.
• Analyzed sensor sensitivity to vegetation parameters and disturbance types (defoliation, drought, logging).

Main Results:

• SAR sensor sensitivity varied significantly with wavelength, forest structure, and disturbance type.
• C-band showed sensitivity to foliage volume (defoliation) but limited response to drought (<1 dB) and clear-cuts (1.5 dB).
• P-band is necessary for detecting subtle disturbances like selective logging or thinning, which are missed by C- and L-bands.

Conclusions:

• No single SAR frequency is sufficient for comprehensive forest disturbance monitoring.
• Combining dense time series and multi-sensor (active/passive) data is essential to overcome limitations.
• Simulation findings are applicable to European forests with similar characteristics, aiding global forest monitoring efforts.