INFLUENCE OF PRESCRIBED BURNING OF PINE STANDS IN NW SPAIN ON SELL MICROORGANISMS

The feasibility of prescribed burning as a tool for the prevention of wildfires in pine stands was evaluated through its effect on microbial groups such as total microflora, heterotrophic bacteria, filamentous fungi and algae as well as those that enter into biogeochemical cycle of carbon. An increase of the Most Probable Number (M P N) of anaerobi c cellulose and pectin decomposers was measured in areas burned by pre scribed fires with a linear intensity of 450 kw m(-1), for a period ex tending from one month and up to two years after the fire. Other group s were not affected and there was no statistically significant change in areas of more moderate intensity (100 and 60 kw m(-1)). Seasonal fl uctuations were also observed in all microbial groups except for total microflora, although there were differences in the fluctuations in di fferent groups and sites. Significant differences in the number of ana erobic cellulose decomposers were observed at different sites. The gro ups of soil microorganisms studied did not suffer long-term effects fr om these levels of fire intensities and some groups even increased sig nificantly.