Vegetation Cover in the Eurasian Arctic: Distribution, Monitoring, and Role in Carbon Cycling

Comparison of several recent, publicly available and widely used land-cover products for the Eurasian Arctic revealed important differences in their representations of vegetation distribution. Such disparities have important implications for models that use these products as driving data sets to monitor vegetation and its role in carbon dynamics. The differences between GLC-2000 and MODIS.PFT are concentrated at borders between biomes, as well as in parts of the region where a significant presence of open-canopy vegetation is expected. In these two maps, tree cover is represented more consistently than shrub or herbaceous cover, and the MODIS.VCF product corroborates the general pattern of tree-cover distribution. The comparison of the MODIS.VCF and AVHRR.VCF maps over northeastern Europe indicates good agreement in the south with increasing disagreement further north primarily due to differences in definitions of the mapped variables. The analysis of land-cover maps at two Landsat validation sites showed different patterns of agreement and disagreement. At the forest dominated St. Petersburg site, the GLC-2000 and MODIS.PFT classifications both exaggerated tree cover and under-reported shrub and herbaceous vegetation. At the tundra site (Komi), the over-reporting of tree cover by GLC-2000 and the failure of MODIS.PFT to separate shrub and herbaceous vegetation were the major issues in representing the overall land cover. A simple analysis that extrapolated results of biogeochemical modeling showed that a very different picture of the regional carbon balance emerges when different vegetation maps are used as model inputs.