SAR-based estimates of the size distribution of lakes in Brazil and Canada: a tool for investigating carbon in lakes

摘要

1. The size of lakes and the size distribution of lakes are important parameters controlling lake function, and how lakes interact with landscapes, the atmosphere and ecosystems. A baseline digital database of lakes could be used to improve understanding of lake function, to extrapolate lake information to regional and global scales, and as a basis for detecting future changes to lakes. 2. This paper examines the capabilities of synthetic aperture radar (SAR) imagery produced by the Japanese Earth Resources Satellite (JERS-1) to map the number and size distribution of lakes in western Arctic Canada, Central Canada and the Pantanal (Brazil). 3. For the Arctic and Pantanal, the total area found within one lake size category increases towards smaller lakes. The opposite was true for the area in Central Canada. The number of lakes in the smallest size category, 0.01 to 0.1 km2, was underestimated for all regions owing to the resolution of the mosaics - 100 X 100 m. The number of large lakes in the Pantanal was over-estimated through confusion with intermittent floodways that are scrubby grasslands and bare sand in the dry season and which exhibit low backscattering and therefore appear dark like lakes. 4. The lake distributions were combined with existing data to produce preliminary regional estimates of carbon accumulation. Lakes may accumulate as much as 1.7 and 1.3 t C km-2 yr-1 for the Arctic Canadian and Central Canadian areas, respectively. No estimates were produced for the Pantanal because there are no applicable data on carbon accumulation rates available for that region.