Effects of long-term prescribed burning on the activity of select soil enzymes in an oak-hickory forest

In low-input or unmanaged ecosystems, the relationship between soil enzyme activity and plant biomass is expected and may be used as an early and sensitive indicator of soil productivity. This study was designed to (1) examine the long-term effects of burning on the activities of arylsulfatase, acid phosphatase, alpha- and beta-glucosidase, and urease; (2) determine the relationship between microbial biomass C and enzyme activities as affected by long-term prescribed burning; and (3) study the seasonal variations in activities of the above-mentioned enzymes. Soil samples (Typic Fragiudalf) were collected from southeastern Missouri where a long-term burning experiment was established in 1949. Treatments consisted of (1) annual burning; (2) periodic burning, every 4 years; and (3) control, unburned. Soil samples (0-15 cm) were collected before and after annual and periodic burning during 1992 and seasonally in 1993. Long-term burning treatments significantly reduced the activities of enzymes studied but did not affect the pH and organic C. The microbial biomass C, total N, available P. and available S content of soil samples from both annual and periodic burning plots were significantly reduced. A significant positive correlation between soil enzyme activities and the microbial biomass was established. The treatment effects were apparent over the background seasonal variability, with reduced enzyme activity for the annual and periodic burning plots as compared with the unburned plots.