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Figure 8.2 summarizes these concepts , along with applications achievable by simple differencing of DEMs . Sanitation - - or removal of any spent flower blooms , infected buds , leaves and stems - - is best done during a dry , calm time of the day . Good sanitation ( including prompt removal of spent flower blooms ) and following the cultural recommendations above will greatly reduce Botrytis problems . The earlier you detect fourlined plant activity , the better your chances of minimizing plant injury . When it is violated because natural phenomena generate large displacements and displacement gradients ( e.g ., volcanic eruptions , landslides ) , simple differencing of before and after topographic data should be adequate to define the changes to the degree of accuracy required for their study . Repeated mapping missions , even in the absence of correlation , can be used to assess large-scale changes through the differencing of elevation measurements . These atmospheric processes are being imaged via differential roughness at the short Bragg wavelengths of the ocean surface wave spectrum . The physiological activity of living biomass and the fate of dead biomass determine the fluxes of carbon from the terrestrial biosphere to the atmosphere , and , thus , the accumulation or removal of important greenhouse gases ( primarily carbon dioxide and methane ) in the atmosphere . On the other hand , local changes may be large and observable by simple differencing of " before " and " after " DEMs .