An image-based inventory of the spatial structure of West Siberian wetlands

Western Siberia contains the world's most extensive wetlands. Despite its recognition as a significant global carbon reservoir, the spatial structure and composition of micro-topographical elements in patterned wetlands have never been analyzed in detail. To address this uncertainty, we applied a multi-scale approach to make a general and realistic estimation of land cover in Western Siberia. Our approach was based on using a regional wetland typology map (1:2500 000 scale), further refined by satellite image classifications (LANDSAT TM, ETM+ in 1:200 000 scale) on test areas designated in the boreal region of Western Siberia. In addition, QuickBird imagery was used for evaluation the fraction of area occupied by micro-topographical elements within patterned wetlands. Finally, we estimated the areal fractions of these micro-landscapes composing the vegetation mosaic of 20 classes on the wetland typology map for each climatic region of the study area. The total area of peatlands was calculated at 68.5 × 10⁶ha, which is higher than earlier estimates. We found almost equal areal extents of ridge-hollow and ridge-hollow-pool patterned wetlands in almost all climatic regions of Western Siberia; in the northern boreal region, however, the ridge-hollow-pool wetland type became dominant and exceeded the areal extent of ridge-hollow wetlands in a proportion of 80-20%. Also, the open water fraction increased dramatically in the northern boreal region. The results of this survey can be used in models of ecosystem carbon dynamics and inventory of trace gas fluxes in wetlands.