Contamination of the southern taiga forests (Middle Urals) by discharges from cooper smelters (heavy metals combined with SO2) not only decreases the mean rate of decomposition of pure cellulose, but also radically changes the spatial structure of the destruction process. Heterogeneity of distribution of the destruction rate is sharply increased near the source of discharge due to differentiation of the space into microregions with high and low destruction rates. The characteristic size of spatial heterogeneity amounts to several tens of centimeters and the distribution of microregions with a high rate is accidental within several tens of meters. A hypothesis has been put forward that the described changes in the spatial structure of the destruction process are related, above all, to disturbed colonization of the substrate by soil myxomycetes.