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CHANGES IN DECOMPOSITION RATE, MICROBIAL POPULATION AND CARBOHYDRATE CONTENT OF AN ACID PEAT BOG AFTER LIMING AND RECLAMATION

K. C. IVARSON

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After 8 mo of decomposition, under laboratory conditions, the unlimed surface sample (0–15 cm, pH 3.8) of an acid peat bog contained about five times as many microbes as the unlimed subsurface material (15–41 cm, pH 4.1). As measured by CO2-C released and numbers of bacteria and actinomycetes, lime had greater effects on the microbial activity of the surface material. Nitrifying bacteria were present and needed lime to become active. Fungal numbers decreased with lime and only 12 genera were found. Temperature had little effect, whereas pH had a marked effect on the distribution of fungal genera. Fusarium oxysporum, Cephalosporium acremonium and a frequently isolated nematode-destroying fungus Harposporium lilliputianum were found only at pH 7.5 and thus appeared to be alien fungi that responded well to an environment of high pH and cultivation. Before incubation, the unlimed lower sample was higher in carbon, nitrogen and methoxyl but lower in hexose, pentose and uronic acid than the unlimed upper sample. During decomposition there was a tendency for hexose and pentose to decrease, this being more noticeable in the upper material. No appreciable changes in nitrogen, carbon, methoxyl and uronic acid content occurred in either sample. Dry matter lost in the surface ranged from 8 to 13% while in the lower material it was from 2.0 to 3.5%. Despite sufficient NPK and a substantial sugar content, Sphagnum litter decomposes at a slower rate than some tree leaf litters. From the literature it is speculated that the slowness is due to the presence of microbial-inhibiting substances such as phenolic compounds.