EFFECT OF LIMING ON SOME CHEMICAL, BIOCHEMICAL, AND MICROBIOLOGICAL PROPERTIES OF ACID SOILS UNDER SPRUCE (PICEA-ABIES L)

Soil pH, total organic C, total N, exchangeable Al, available P, CO2 evolution, microbial biomass C and N, phosphatase and dehydrogenase acivities were determined in acid soils sampled under spruce subjected to acid deposition, before and after liming. A slight decrease in pH values was observed from the edge of a tree canopy to the base of the trunk in acid soils. Liming drastically reduced exchangeable Al and increased CO2 evolution, microbial biomass, and the metabolic quotient. The microbial biomass C to total organic C ratio increased after liming but did not reach 2%, the average value considered valid in soils where the C content is in equilibrium, that is when C inputs are equal to C outputs. The microbial biomass C:N ratio decreased after liming, thus indicating that bacteria became predominant over fungi when soil acidity decreased. Dehydrogenase activity but not phosphatase activity was increased by liming. The decrease in phosphatase actitvity was not completely related to the increase in available P, but was also dependent on microbial growth and the decrease in acid phosphatase, the predominant component of acid soils.