Forest biomass change estimated from height change in interferometric SAR height models

Area of Science:

• Earth Observation
• Remote Sensing
• Forestry

Background:

• Need for advanced satellite remote sensing methods to monitor tropical forest carbon stocks.
• Advanced RADAR instruments offer novel capabilities, including cloud penetration and forest height measurement via stereo imaging.
• Forest height changes are directly related to biomass and carbon stock changes.

Purpose of the Study:

• To apply Tandem-X and SRTM RADAR stereo imaging data for deriving forest height information.
• To develop and demonstrate an interferometry-based approach for monitoring forest biomass and carbon stocks.
• To assess the feasibility of this method in tropical regions where terrain and biomass data are often scarce.

Main Methods:

• Utilizing interferometric processing of RADAR stereo image pairs from Tandem-X and SRTM missions.
• Developing a model relating RADAR echo height to above-ground biomass in boreal forests.
• Mapping biomass changes and comparing results with airborne laser scanning data.

Main Results:

• A model was developed where above-ground biomass increases by 15 t/ha for every 1m increase in RADAR echo height.
• Accurate estimates of biomass changes were achieved between 2000 and 2011, with plot-level accuracy of 65 t/ha (50% of mean biomass).
• The method proved effective even without precise terrain heights or prior in-situ biomass data, crucial for tropical applications. Logging impacts were accurately mapped.

Conclusions:

• Satellite-based stereo RADAR imaging is a promising technique for supporting REDD (Reducing Emissions from Deforestation and forest Degradation) initiatives.
• Interferometric processing of RADAR data yields forest height change maps, enabling reliable estimation of temporal biomass and carbon dynamics.
• This method offers a viable solution for monitoring forest carbon stocks in data-scarce tropical regions.