Accuracy Assessment of Stem Volume Retrieval from ERS-1/2 Multitemporal Coherence in Eurasian Boreal Forests

The sensitivity of the ERS-1/2 tandem coherence to forest biophysical properties is recognized to be sufficient for achieving accurate estimation of stem volume in boreal forest. Nonetheless, depending on environmental conditions and forest stand properties (e.g. size, structure) the retrieval accuracy can change significantly. For this reason methods are required for the identification of forest stands for which high retrieval accuracy can be obtained. From an analysis of multi-temporal coherence datasets at several test sites in Scandinavia and Siberia, we can conclude that optimal conditions for the retrieval are represented by stable winter frozen conditions with an at least moderate breeze. For such conditions, the retrieval accuracy increases if only stands larger than a few hectares and with a certain degree of homogeneity are considered. For such stands, the effective stem volume retrieval error that can be obtained in boreal forests ranges between 15 and 25%.To overcome the necessity of falling back on inventory data to identify such stands, multi-temporal consistency of coherence, of stem volume estimates and stand size can be used as stand selection criteria.