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THE SOIL POPULATION. AN INVESTIGATION OF THE BIOLOGY OF THE SOIL IN CERTAIN DISTRICTS OF ABERYSTWYTH

Annals of applied biology, 1924-10, Vol.11 (3‐4), p.349-394 [Peer Reviewed Journal]

ISSN: 0003-4746 ;EISSN: 1744-7348 ;DOI: 10.1111/j.1744-7348.1924.tb05717.x

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  • Title:
    THE SOIL POPULATION. AN INVESTIGATION OF THE BIOLOGY OF THE SOIL IN CERTAIN DISTRICTS OF ABERYSTWYTH
  • Author: THOMPSON, MABYN
  • Is Part Of: Annals of applied biology, 1924-10, Vol.11 (3‐4), p.349-394
  • Description: 1 An attempt has been made to give an account of a systematic qualitative and quantitative seasonal investigation of the macroscopic soil fauna of a limited area, and to correlate the data obtained with the general environmental conditions. The piece of land most carefully investigated was a pasture field from which soil samples were obtained fortnightly throughout two successive years, but for purposes of comparison, observations were also made in connection with ungrazed grassland, similar ungrazed land with the turf recently removed and cultivated land; the soil of these areas is very similar in physical, chemical and geological characteristics. 2 The method of investigation included the taking of standard nine‐inch cube samples. A preliminary sorting of the soil particles was followed by sieving the soil in water and placing the residue with water in a shallow dish, when the smaller organisms floated to the surface. a.  The main area studied has been in pasture for over 40 years and has a typically mesophytic vegetation. Water content percentages were fairly high. The temperature of the soil varied with depth, being usually higher at 9 inches depth than at 41/2 inches; it varied much less than tha temperature of the atmosphere. b.  With rare exceptions the population in the surface three inches was markedly greater than that in the lower depths, probably because the majority of soil organisms are root feeders and the average root level ends at about three inches depth; carnivorous forms would naturally tend to concentrate here also. Another reason may be found in the better aeration of the soil in the surface layers. c.  The orders Collembola, and Acarina together determine the trend of the total fauna curve, i.e. they are the markedly dominant groups of the soil population as regards the number of individuals. A very few species are in turn responsible for the trend of the Collembolan and Acarine curve (Fig. 3); the high total numbers of the population are mainly contributed by the Collembolans, Onychiurus ambulans, O. armatus and to a lesser extent by Isotoma viridis and Folsomia fimetaria. d.  Some orders such as Collembola and Acarina persist in varying numbers throughout the year, while other groups such as Oligochaeta and Nematoda entirely or almost entirely fall out for varying lengths of time. In the persistent groups, the same species remain dominant throughout the year. e.  The maximum population occurs in the winter months; in part probably due to the relative absence of drought conditions in the winter, water content being more constant. The two summers have low totals for the fauna. Water content presumably plays an important part in connection with the small white Oligochaeta. Some preliminary experiments were carried out with regard to the effect of drought on Collembola and Acarina; it was found that life was very much curtailed by drought conditions. 4 The fauna of the ungrazed grassland area was similar to the pasture field except that the population was much greater. The richer character of the fauna is probably due to the protection of the long grass and the prevention of undue evaporation of moisture from the soil; being ungrazed the soil is less compressed. 5 The examination of land recently ploughed resolved itself into a survey of the results following (i) a removal of the turf layer; (ii) the further result of allowing the land so treated to be untouched for a definite time. With the removal of the turf, also goes the main source of food supply together with the majority of the soil fauna, and temporary conditions of drought are set up in the surface layers of soil. The main points of interest were: (i) the scarcity of the fauna except the Collembola; (ii) before weeds were allowed to grow the population of the upper three inches was less than that of lower levels, the numbers increasing with depth; (iii) with the growth of weeds the fauna showed some approach once more in density, variety and distribution to the grassland population. 6 The examination of cultivated land gave results very similar to those obtained for the previous area. The population is considerably less than that of the pasture. Generally speaking, the population of the surface three inches of soil hardly exceeds that at a depth of three to six or six to nine inches. The same orders occurred as in the other areas. 7 Organisms injurious to the vegetation were present in all areas, but not usually in sufficient numbers to cause any damage. An exception occurred in cultivated land in which the roots of Perennial Rye grass were eaten away by the Diplopod Polydesmus collaris. 8 Parasitism was infrequent but at least the Achorutidae were subject to attack by small Nematodes. Fungi were not normally found parasitic on the soil fauna; such attack appeared to be restricted to injured specimens. 9 A brief review has been given of work previously published and comparisons made with the present paper.
  • Publisher: Oxford, UK: Blackwell Publishing Ltd
  • Language: English
  • Identifier: ISSN: 0003-4746
    EISSN: 1744-7348
    DOI: 10.1111/j.1744-7348.1924.tb05717.x
  • Source: Alma/SFX Local Collection
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