Urban, Marcel; Hese, Sören; Herold, Martin; Pöcking, Stefan; Schmullius, Christiane C (2012): A fractional vegetation cover remote sensing product on pan-arctic scale, Version 2, with link to geotiff image. Friedrich Schiller University Jena, PANGAEA, https://doi.org/10.1594/PANGAEA.780464
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In the high northern latitudes the vegetation cover and land surface structure is affected by seasonal freeze/thaw dynamics of the uppermost permafrost layer (active layer). The land cover in the arctic regions is characterized by low vegetation species (shrubs, grasses, mosses) in the northernmost regions as well as the boreal forest in the southern parts.
The pan-arctic data product presented here is based on user requirements which were defined in the ESA DUE Permafrost for the coarse resolution vegetation observation variable. The user requirements have shown the need of percentage cover information for different vegetation physiognomy and barren areas. Therefore, fractional cover information for trees, shrubs, herbaceous and non-vegetated areas were extracted using coarse resolution global land cover products in a harmonization approach (Urban et al. 2010, doi:10.1127/1432-8364/2010/0056).
As input MODIS Land Cover, GlobCover, Synmap as well as MODIS VCF (Vegetation Continuous Fields) were used. In the harmonization approach percentage cover values for different vegetation physiognomy and barren areas were extracted using the class description of each land cover legend. Therefore it was feasible to convert thematic classes to fraction cover values for each pixel. The fractional vegetation cover product has a spatial resolution of 1 km. As this dataset provides percentage information instead of thematic classes, a reduction of the spatial resolution for the integration in modeling approaches (spatial resolution 25 km or 0.5°) is feasible (Urban et al. 2010, doi:10.1127/1432-8364/2010/0056).
In the version 1 product we found, that there are cover information from trees north of the tree line (Circumpolar Arctic Vegetation Map, CAVM - Walker et al. 2005), which are reasoned by misclassification of the forest classes in the global land cover datasets. Based on these findings, the CAVM, which provides spatial information about the tree line, were used as thematic information to mask incorrect percentage tree cover information in the tundra regions. Hence, the product version 2 is providing percentage cover information for shrubs, herbaceous and non-vegetated areas in the high latitude tundra regions. No modifications have been done for the boreal regions in the version 2 product.
A validation of the version 2 product was done using Landsat imagery with a resolution of 30 m. To assess the accuracy, the Landsat imagery was classified into the four components of the version 2 products (trees, shrubs, herbaceous and non-vegetated areas). By using chessboards/fishnet segments with a resolution of 1 km, the percentage cover of the classes from the Landsat classification are compared with the components of the pan-arctic fractional cover product. The validation results has shown very good agreement for the taiga and tundra areas (trees 83 - 97 %, shrubs 87 - 91 %, herbaceous 66 - 78 % and non-vegetated areas 74 - 85 %). Within the taiga-tundra transitions zone, lower accuracies have been found. This is reasonable since these regions are characterized by heterogeneous landscapes, which are hardly to classify with coarse resolution earth observation data.
See "other version" for version 1 of dataset.
This dataset is part of the ESA Data User Element (DUE) Permafrost Full Product Set (doi:10.1594/PANGAEA.780111).