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Numbers of Soil Microorganisms as Ecological Indicators of Changes Resulting from Moorland Reclamation on Exmoor, U. K.

E. Maltby
Journal of Biogeography
Vol. 2, No. 2 (Jun., 1975), pp. 117-136
Published by: Wiley
DOI: 10.2307/3038078
Stable URL: http://www.jstor.org/stable/3038078
Page Count: 20
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Numbers of Soil Microorganisms as Ecological Indicators of Changes Resulting from Moorland Reclamation on Exmoor, U. K.
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Abstract

As early as 1922 Waksman emphasized the use of microbiological analysis of soil as an index of soil fertility. Since that time there have been few comparative investigations of soil microbiology and related soil properties. For a part of Exmoor, three main soil phases were identified within the Ashcombe soil series: unreclaimed, relcaimed and reverted. At sites within these phases four major groups of microorganisms-filamentous fungi, yeasts, actinomycetes and bacteria -were enumerated at several depths in the profile, using a soil-dilution plate technique. Significant differences were found between soil phases in terms of the numbers of various groups of microorganisms at depths of between 30-50 mm and 0-20 mm. Microbial estimates generally declined with depth down the profile. For all depths in the relcaimed phase, actinomycetes and bacteria exceed filamentous fungi and yeasts by at least and order of magnitude. This distinction is not as clear-cut in the unreclaimed profiles. The reverted profiles occupy positions intermediate between the reclaimed and unrelcaimed patterns. The relations between different groups of microorganisms within and between profiles are described in some detail. Microbial ratios F : Y, A: B and F : B were determined. In the reclaimed phase F : Y is less than or close to unity, whilst in the reverted and unreclaimed phases the ratio is considerably greater than 1· 00. A: B is greater than 1· 00 in the case of two unlimed reverted sites, buth is less than 1· 00 for all other samples. The numerical estimates of microorganisms and selected ratios are used to illustrate soil phase differences resulting from the activities of man and his grazing animals in an upland environment. Ecological interpretations of the results are attempted.

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