The effects of biocidal treatments on metabolism in soil .3. The relationship between soil biovolume, measured by optical microscopy, and the flush of decomposition caused by fumigation

A - Papers appearing in refereed journals

Jenkinson, D. S., Powlson, D. S. and Wedderburn, R. W. M. 1976. The effects of biocidal treatments on metabolism in soil .3. The relationship between soil biovolume, measured by optical microscopy, and the flush of decomposition caused by fumigation. Soil Biology and Biochemistry. 8 (3), pp. 189-202.

AuthorsJenkinson, D. S., Powlson, D. S. and Wedderburn, R. W. M.
Abstract

The hypothesis that the flush of decomposition following fumigation is a measure of the amount of biomass in a soil was tested by comparing the biomass thus found, and as calculated from direct microscopic measurement of the soil biovolume. Eight soils developed under contrasting systems of management and climate were used, six from England and two from Nigeria. The biovolume was measured by a modification of the Jones and Mollison procedure, in which agar films prepared from known amounts of soil were stained with phenolic aniline blue. Fluorescent stains were less satisfactory in that they did not stain as wide a range of organisms as phenolic aniline blue. Spherical organisms were divided into 13 size classes, with diameters ranging from 0·3 to 19 μm, and the numbers in each size class counted. Hyphae were divided into seven diameter classes, with dia. ranging from 1 to 11 μm, and the lengths in each class measured. For seven of the soils there was close agreement between the two different methods of measuring biomass C. With an acid woodland soil (pH 3·9). the biomass C, as calculated by direct microscopy, was seven times that calculated from the size of the flush; it is suggested that this discrepancy arose because stainable cell walls from dead organisms persist for much longer in the strongly acid soil than in the other, more nearly neutral, soils.

Both methods were used to follow the effects of fumigation on the soil biomass. A near-neutral soil was fumigated with CHCl3, the fumigant removed and the soil incubated for 53 days at 25° C. The decrease in biomass caused by fumigation was less as measured by direct microscopy than as measured from the size of the flush, suggesting that stainable cell walls of killed organisms can persist for a considerable time after fumigation.

Data on the relationship between the size of soil organisms and their contribution to soil biovolume are presented graphically. The biovolume in hyphae and in ‘spherical’ organisms was roughly equal in all soils. There was a linear relationship between the cumulative biovolume and the logarithm of organism volume lor ‘spherical’ organisms over the volume range 0·05 μm3 to 100 μm3. If, for a given soil, the volume range is divided into equal volume classes on a logarithmic basis, each class contains the same biovolume. Thus, comparing equal logarithmic volume classes, a class of rare large organisms contains as much biovolume as a class of numerous small organisms.

Year of Publication1976
JournalSoil Biology and Biochemistry
Journal citation8 (3), pp. 189-202
Digital Object Identifier (DOI)doi:10.1016/0038-0717(76)90003-1
Open accessPublished as non-open access
Output statusPublished
Publication process dates
Accepted14 Aug 1975
Copyright licensePublisher copyright
ISSN0038-0717
PublisherElsevier

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