FUMIGATION-EXTRACTION AND SUBSTRATE-INDUCED RESPIRATION DERIVED MICROBIAL BIOMASS-C, AND RESPIRATION RATE IN LIMED SOIL OF SCOTS PINE SAPLING STANDS

The effect of liming on microbial biomass C and respiration activity w as studied in four liming experiments on young pine plantations. One o f the experimental sites had been limed and planted 12 years before, t wo 5 years before, and one a year before soil sampling. The youngest e xperimental site was also treated with ash fertilizer. Liming raised t he pH(KCl) of the humus layer by 1.5 units or less. Microbial biomass was measured using. the fumigation - extraction and substrate-induced respiration methods. Liming did not significantly affect microbial bio mass C, except in the experiment which had been limed 11 years ago, wh ere there was a slight biomass increase. Basal respiration, which was measured by the evolution of CO2, increased in the limed soils, except for the youngest experiment, where there was no effect. Ash fertiliza tion raised the soil pH(KCl) by about 0.5 unit, but did not influence microbial biomass C or basal respiration. Fumigation-extraction and su bstrate-induced respiration derived microbial biomass C values were co rrelated positively with each other (r = 0.65), but substrate-induced respiration gave approximately 1.3 times higher results. In addition, the effect of storing the soil samples at +6 and -18-degrees-C was eva luated. The effects were variable but, generally, the substrate-induce d respiration derived microbial biomass C decreased, and the fumigatio n-extraction derived microbial biomass C and basal respiration decreas ed or were not affected by storage.