## 7 Conclusion  
We used high-resolution TerraSAR-X (TSX) images in combination with Landsat-5 TM-based Normalized Difference Vegetation Index (NDVI) to explore the application of SAR data for characterizing post-drainage succession in thermokarst lake basins on the Seward Peninsula, Alaska. Backscatter and NDVI properties of 60 known drained thermokarst lake basins (DTLBs) that drained partially or completely since 1950 (modern DTLBs), as well as the properties of 14 DTLBs radiocarbon-dated to be up to 10,000 years BP (young, medium-aged, old and ancient DTLBs) were investigated in three subsets: (1) 0-50 years since drainage, modern basins; (2) 50-10,000 years since drainage, radiocarbon-dated basins; and (3) 0-10,000 years since drainage, modern and radiocarbon-dated basins. Our findings indicate that TSX backscatter and Landsat NDVI can trace long-term (0-10,000 years) succession dynamics of DTLBs related to vegetation, soil and permafrost changes. The logarithmic relationships of basin age with mean basin backscatter and with mean basin NDVI resulted in R\({}^{2}\) = 0.36 (p \(<\) 0.05) and R\({}^{2}\) = 0.53 (p \(<\) 0.05), respectively. For the 50-10,000 years period, TSX backscatter data outperformed NDVI in discriminating basin successional stage, likely due to its ability to partially detect soil moisture conditions. We here found R\({}^{2}\) = 0.58 (p \(<\) 0.05) between radiocarbon-dated basin age and mean basin backscatter. Overall, there was a decreasing trend in both backscatter and NDVI as basin age increased as a result of post-drainage changes in basin surface properties that include decreasing vegetation productivity after an initial productivity spike, decreasing soil moisture, renewed ice-wedge growth and development of either ponded or dry polygonal networks. However, in modern basins, the 50 year time scale was insufficient to find a clear relationship of basin age with TSX backscatter and NDVI. We noticed that not only time since drainage, but a combination of local environmental factors highly influences the successional stages of a basin. This was more prominent in modern basins. Over time with continuing basin succession and stabilization of basin floor, variability in basin surface properties decreased within a basin, as well as among basins of an age class. Since DTLB dynamics likely affect landscape-scale carbon fluxes in high northern latitudes, it is necessary to better understand the spatial and temporal distribution of thermokarst lakes and DTLBs across large regions. Our study highlights the excellent opportunity to use and combine various remote sensing tools for better estimation of the areal extent of high latitude carbon pools and sources of greenhouse gases associated with thermokarst dynamics. Future research should be directed toward utilizing high-resolution topographic data with SAR data, including short and long wavelengths, as well as optical remote sensing data, to better understand the processes driving the evolution of basins. Additionally, multi-temporal analysis of SAR data for basins would increase our understanding of seasonal soil moisture dynamics and their influence on post-drainage vegetation and soil succession.