Canadian Forest Service Publications
Estimates of forest growing stock volume for Sweden, Central Siberia and Québec using Envisat Advanced Synthetic Aperture Radar backscatter data. 2013. Santoro, M.; Cartus, O.; Fransson, J.E.S.; Shvidenko, A.; McCallum, I.; Hall, R.J.; Beaudoin, A.; Beer, C.; Schmullius, C. Remote Sensing 5(9):4503-4532.
Issued by: Northern Forestry Centre
Catalog ID: 35070
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A study was undertaken to assess Envisat Advanced Synthetic Aperture Radar (ASAR) ScanSAR data for quantifying forest growing stock volume (GSV) across three boreal regions with varying forest types, composition and structure (Sweden, Central Siberia and Québec). Estimates of GSV were obtained using hyper-temporal observations of the radar backscatter acquired by Envisat ASAR with the BIOMASAR algorithm. In total, 5.3·106 km2 were mapped with a 0.01° pixel size to obtain estimates representative for the year 2005. Comparing the SAR-based estimates to spatially explicit datasets of GSV generated from forest field inventory and/or Earth Observation data revealed similar spatial distributions of GSV. Nonetheless, the weak sensitivity of C-band backscatter to forest structural parameters introduced significant uncertainty to the estimated GSV at full resolution. Further discrepancies were observed in the case of different scales of the ASAR and the reference GSV and in areas of fragmented landscapes. Aggregation to 0.1° and 0.5° was then undertaken to generate coarse scale estimates of GSV. The agreement between ASAR and the reference GSV datasets improved; the relative difference at 0.5° was consistently within a magnitude of 20-30%. The results indicate an improvement of the characterization of forest GSV in the boreal zone with respect to currently available information.
Plain Language Summary
Forest inventory maps are useful tools in assessing the state of forest resources. Maps that show the volume of live standing trees can be used to estimate forest biomass and carbon. Uncertainties in these estimates, however, are caused by natural disturbances such as fire, insects, changes in land use, and variations in methods used to make the maps. We attempted to address these uncertainties by using global data sets of radar images from Envisat Advanced Synthetic Aperture Radar. This radar offers, for the first time, consistent measurements that could be used in models to predict land-atmosphere carbon dioxide exchange as an indicator of how well forests are growing. This study assessed the radar’s ability to estimate the volume of live standing trees over 3 areas in the boreal zone located in Sweden, Central Siberia and Québec, Canada. While these estimates are not sufficient for operational mapping, they do provide consistent data suited for global monitoring of the state of forests, particularly for northern boreal environments.