Regional mapping of forest growing stock volume with multitemporal ALOS PALSAR backscatter

The paper presents advances in regional mapping of forest growing stock volume (GSV, unit: m³/ha) using multitemporal ALOS PALSAR images. For this, an approach based on the Water Cloud Model has been used. Fine Beam Dual (FBD) and Wide Beam (WB) mode backscatter data acquired during 2010 were inverted to GSV; the individual GSV estimates were then combined to form an improved estimate. Examples of regional mapping for the boreal, temperate and tropical zone are here presented. Estimates were obtained at 25 m resolution using FBD data only and at 75 m combining multi-looked FBD estimates and WB estimates. The inclusion of multi-temporal WB data served to improve the spatial characterization of GSV. At pixel level, the discrepancy with respect to other estimates from Earth Observation data was large (relative RMSE ~ 90%). Aggregation to lower resolution (e.g., 1 km) increased the agreement and a relative RMSE mostly below 30% was obtained.