INFLUENCE OF HUMIDITY ON MICROBIAL CELLULASE ACTIVITY IN PEAT FROM A RAISED BOG

The dynamics of cellulase activity (CA) was followed during incubation of ombrotrophic peat at different moisture levels. The highest CA was observed at the lowest tested humidity of peat (40 to 60%). During th e course of incubation, CA gradually increased over two weeks, reachin g the maximum value of 0.4 mg reducing sugars (RS)/(h dm(3)) on the ni nth day. Feat with a high moisture content (92 - 93%) preserved low CA [0.05 mg RS/(h dm(3))], characteristic for the native peat. On the ba sis of the dynamic data, it was concluded that the rise of CA in dried peat was due to the activation of microorganisms, including hydrolyti c ones, by the stress of drying and rewetting rather than to optimizat ion of the peat water regime per se. This conclusion was confirmed in special experiments with peat samples subjected to drying-rewetting cy cles. The highest CA was always observed immediately after rewetting d ried peat. During subsequent incubation under high moisture content (9 2 - 93%), CA remained high, oscillating within the range from 0.4 to 1 .0 mg RS/(h dm(3)).