Potential of C and X Band SAR for Shrub Growth Monitoring in Sub-Arctic Environments

The Arctic and sub-Arctic environments have seen a rapid growth of shrub vegetation at the expense of the Arctic tundra in recent decades. In order to develop better tools to assess and understand this phenomenon, the sensitivity of multi-polarized SAR backscattering at C and X band to shrub density and height is studied under various conditions. RADARSAT-2 and TerraSAR-X images were acquired from November 2011 to March 2012 over the Umiujaq community in northern Quebec (56.55◦N, 76.55◦W) and compared to in situ measurements of shrub vegetation density and height collected during the summer of 2009. The results show that σ is sensitive to changes in shrub coverage up to 20% and is sensitive to changes in shrub height up to around 1 m. The cross-polarized backscattering (σHV ) displays the best sensitivity to both shrub height and density, and RADARSAT-2 is more sensitive to shrub height, as TerraSAR-X tends to saturate more rapidly with increasing volume scattering from the shrub branches. These results demonstrate that SAR data could provide essential information, not only on Remote Sens. 2015, 7 9411 the spatial expansion of shrub vegetation, but also on its vertical growth, especially at early stages of colonization.