TABLE 1. PopulatIOn density (thousands/m.') and number of species of Acari and Col/embola ingrassland soils. (Number of species in parentheses.)

Author Habitat Acari Collembola TotalSalt et al old pasture 232 ( -) 66 (25) 298 ( -)Macfadyen M olinia fen t72 ( 52) 32 (21) 204 ( 73)Hairston and Byers old meadow 22t ( 87) 14 (20) 235 (107)Haarlov old pasture ("Level Pasture") 179 (161) 109 (32) 288 (193)Wood Sesleria (III) 153 (103) 25 (25) 178 (128)

Festuca+Agrostis (IV) 152 ( 87) 7.3 (26) 225 (113)Nardus (V) 176 ( 90) 59 (25) 235 (115)

Weis-Fogh old pasture ("Plain") 24 ( 83) 8 (16) 32 ( 99)Sheals old grassland 34 ( 36) 23 (18) 57 ( 54)Wood old pasture 33 ( -) 26 (21) 59 ( -)Dhillon and Gibson old pasture 32 ( 19) 26 (16) 58 ( 35)Davis reclaimed ironstone workings (1) t5 ( 43) 20 (23) 35 ( 66)

old pasture (100) 18 ( 5t) 18 (21) 36 ( 72)

WOOD: THE FAUNA OF GRASSLAND SOILS 79

THE FAUNA OF GRASSLAND SOILS WITH SPECIAL

REFERENCE TO ACARI AND COLLEMBOLA

T. G. WOOD

Department of Scientific and Research, Entomology Division, Nelson*

INTRODUCTION

Soil animals may be classified into variouscategories depending on size (Fenton 1947;van del' Drift 1951), degree of dependence onthe soil (Jacot 1940), mode of locomotion(KUhnelt 1955) or life form (Gisin 1943;Klima 1956). The first is the most widely usedand a simple division is into micro-fauna(O.OOlmm-O.lmm), meio-or meso-fauna(0.lmm-l0rmn) and macro-fauna (over10mm). The micro-fauna includes protozoa,nematodes, tardigrades; the meso-fauna, mites,collemboles, enchytraeids; and the macro-fauna,earthworms, molluscs and many insects,myriapods and spiders. This classification isobviously arbitrary, and some grou.ps (e g.spiders) have representatives in more than onecategory.Grassland soils contain many individuals

and many species from each of these groups.Acari and Collembola are generally the mostabundant arthropods, and in this paper theirecology will be considered with particularreference to their population density, com-munities and role in certain soil processes.

POPULATIONS OF ACARI AND COLLEMBOLA

IN GRASSLAND SOILS

The population densities and numbers ofspecies in different grassland soils in Britain,continental Europe and northern United States

of America are shown in Table 1. Despitetheir variety the first seven habitats (moorland,fenland and old pasture soils in England, an oldpasture in Denmark and an old meadow innorthern U.S.A.) have remarkably similar popu-lation densities (178,000/m.'-298,000/m.').eonsidering the populations in mosses of280,000/m.2 (Wood 1963) and in naturalheathland of 162,000/m.2 (Murphy 1963),it appears that population density of thesesmall arthropods cannot be usefully usedas a distinguishing characteristic of a par-ticular habitat. This suggestion is not necessar-ily discredited by the very low populationdensities (35,000/m.'-59,000/m.2) recordedfrom the last six sites shown in Table 1, as theextraction methods used in these particularinvestigations (with the possible exception ofDhillon and Gibson's method) almost certainlyin<;urred serious losses of certain groups, thusmaking an unknown contribution to the lowrecorded populations. Because of the greatdifferences in efficiency between the variousextraction methods it is not profitable tospeculate about causes of possible differences inpopulation densities.

. Present address: C.S.I.R.O., Division of Soils, PrivateBag N. 1, Glen Osmund, South Australia.

Macfadyen

Frenzel Nipp.

Neu.

A

B

Weis-Fogh M

Haarf{lfv Knurr.

L.P

Davis 1

100

Salt et al

Wood V.

IV

III

Dhillon & Gibsan

Shea Is

Weis-Fogh P

Ford

OS

81-100

61-80

41-60

21-40

0-20

WOOD: THE FAUNA OF GHASSLAND SOILS

Mean density of Acari and Collembola isprobably meaningless in itself, and the figuresquoted indicate that it may not even be usefulfor comparative purposes. In fact, a featureof most investigations on soil micro-arthropodsis the great seasonal variation in populationdensity in any particular site, with the resultthat fluctuations in density are more readilyrelated than the mean to site conditions.COMMUNITIES OF ACAHA AND COLLEMBOLA

IN GHASSLAND SOILS

Over .100 species are found in most grasslandsoils (Table 1), and whereas the variety of

D'IGUHE 1. Conzparison of species-compositionexplanation see text. Details of authors and

Haarlov (1960)-Ll1: "Leyel Pasture" (see Table 1).-Knurr: old pasture, north and southfacing sides of ant. mounds, Knurre-vang. Brown earth, sandy lO<1m.

.

(1g.}8)-P: "Plain" (see Table 1).-M: old me<:lclo\'\', "l\1eadow" and"Southern Meadow", Brov n earth,sand.

Collembola (16-32 species) is fairly uniform,that of Acari (19-161 specics) is not. Dhillon

and Gibson (1962) comparcd the published listsof species from ten old grasslands in Britain,although in most cases the fauna was incom-pletely identified and there were unavoidablcerrors in identification. However they vvereable to show that the species composition ofthese apparently similar habitats was veryvariable, and of the 63 species of Collembolarecorded, only five \vere recorded from seven ormore of the ten fields and 40 were recordedfrom only one.

of Collembola in various grassland soils. Forhabitats as in Table 1 with the addition 0/:-

Ford (1937)-Ungrnzed Bromus grassland (tussockfauna only).

Frenzel (1936)-A: Hundsfeld, dry meadow, Ull-manured.

-B: Hundsfeld, dry meadow, manured.-Neu: Neuhaus, moist meadow.-Nipp: Nippern, wet Cyperuceaemeadow. Poland, nr. Wroclaw(Breslau).

80

WOOD: THE FAUNA OF GRASSLAND SOILS

A comparison of the species of Acari andCollembola from several grassland soils inBritain and continental Europe is shown inFigs. 1 and 2. With one exception (Ford1937) the comparison includes only thosestudies where identification of species wasreliable and reasonably complete. For thisreason the information on mites refers only toMesostigmata and Cryptostigmata. The .listsof species from each habitat were comparedusing Sorensen's (1948) quotient of similarity(QS) which is given by-

2cQS = X 100

a + bwhere, for any two habitats, c is the numberof species common to both and a and barethe total number of species from each habitat.The figures obtained enable the habitats to becompared with each other in the form of atrellis diagram in which the habitats with themost similar faunas (highest QS values) areplaced closest together.

The most obvious conclusion from the com-parison of Collembola (Fig. 1) is that com-munities in different soils in the same locality(Frenzel's, Haarlov's. Davis's, and Wood's sites)are more similar (QS values of 52-90) thancommunities from different localities (QSvalues of 10-68). Excluding Weis-Fogh's siteP, the Collembola communities of differentgrasslands in continental Europe (Frenzel's,Weis-Fogh's M and Haarlov's sites) showreasonable similarities to each other (meanQS ~ 54). There is less similarity among the

Collembola of British grasslands (meanQS = 38), and in fact greater similarities arefound between the very different sites studiedby Davis and by Wood (mean QS between10calities = 49) than between the four oldagricultural grasslands (mean QS = 30) studiedbv Davis (site 100), Dhillon and Gibson,Sheals and Salt el al. It is perhaps surprisingthat the Collembola of Macfadyen's Moliniafen near Oxford have closest affinities withFrenzel's east European sites.

The comparison of Acari (Fig. 2) shows veryclearly that the communities of different grass-land soils in the same locality are very similar(QS values of 60-83), whereas there are fewsimilarities betwecn soils from different locali-ties (OS values of 0-56). Similar conclusionsmav be drawn from Franz's (1963) com-

HI

parisons of the oribatid mites in a variety ofheathland and forest soils in Finland, Swedenand central Europe.

These comparisons of Acari and Collembolain 18 different grassland soils involved over 500species. Very few occurred in more than 12sites and among these were Tullbergia kraus-baueri (Born), Foisomia quadrioculata(Tullb.), 'soloma viridis BourI. (Collembola),Rhodacarus rose us Oudms. (Mesostigmata),Teclocepheus velalus (Mich.), Minunlhozelessemirufus (C.L.K.) and Puncloribales punclum(C.L.K.) (Cryptostigmata). The majority(more than 90% of the total) might appearto be distributed by chance and to substantiateHaarlov's (1960) suggestion that micro-arthropod communities may be made up ofspecies derived from the species-complex inthe immediate surroundings (in a geographicalsense), and that the species-composition of aparticular habitat may be quite different fromthat of similar habitats in different localities.However, as Davis (1963) expressed it, theessence of community ecology rests on the"conviction that the presence and relativeabundance of a number of species in a circum-scribed area means more than that each ofthem happens to be there separately". Thusthe occurrence of a particular group of speciesin a number of habitats would lead one toexpect that the habitats in question had certainproperties in common. For example theZygoribalula exelis (Nic.)-Eremeus oblongusC.L.K. community of dry mosses, is of fairlyconstant species-composition in such widely-separated areas as northern England (Wood1963), Germany (Strenzke 1952; Kntille 1957)and Austria (Pschorn-Walcher and Gunhold1957). In more complex environments, suchas grassland soils, the pattern (if it exists) isless obvious rmd the factors determining theoccurrence of species are so little understoodthat more often than not what appears to be auniform habitat as regards vegetation, soil typeand various physical and chemical propertiesof the soil, may consist of a numher of distincthabitats as far as the small soil arthropods arcconcerned. The environment of these anima]sconsists of the network of soil cavities and the'jungle' of root hairs and fungal hyphae, andit is unlikely that this environment can beadequately described in terms of soil type,vegetation or by quantitative measurements ofsoil properties such as pore spar.e and organicmatter. The lack of adequate descriptions of

82

Frenzel A

8

Neu.

Nipp.

Wood V

IV

III

Macfadyen

Davis 1

100

Haarl\1>v L.P.

Knurr.

Shea Is

Weis-Fogh M

p

Dhillon & Gibson

Ford

WOOD: THE FAtJNA OF GRASSLAND SOILS

«

.

='vaJ Z

.

Q.Q..-Z - -

.oo~>>

.

(!)

o/J

Ci

oo~

a.:

...J

..r;(/)--

these animals' envj:-onments may go a long waytowards accounting for such apparent anomaliesas an old pasture in Northamptonshire (Davis'site 100) having proportionately as many ormore species of Collem bola in common witheach of three very different moorland soils(Wood's sites III, IV and V) as it has withthree other old grassland soils in Britain (Salt's,Sheals' and Dhillon and Gibson's sites).

ROLE OF ACAHI AND COLLEMBOLA IN

SOIL PROCESSES

The significance of mites and Collembola inthe life of the soil can be considered only in

FIGURE 2. Comparison of species-compo~ition of Acari (Mesostigmata and Cryptostigmata only)in various grassland soils. For explanatwn see text, Table 1 and Fig. 1.

relation to total animal activity. Of the manyaspects of this subject, cnly two win be con-sidered here: the pedological significance andcontribution to total soil metabolism of thesetwo groups.

Pedological significance

Interest in the pedological significance of soilanimals was increased by Kubiena's (1943,1953) studies of thin soil sections from differenthumus forms, which led him to state (Kubiena1955) that the progress of humification (i.e.decomposition of organic matter) movedparallel with the accumulation of animal

\tV'OOD: THE FAUNA OF GRAtitiLAND SOILS

excrement in the soil. A recent classificationof grassland humus forms (Barratt 1964) indi-cates that soil animals play an important rolein determining the characteristic features oftheir micro-fabrics. Edwards and Heath (1963)demonstrated, by a series of exclusion experi-ments, that there was no breakdown of Etterin the absence of soil animals. Their experi-ments showed that earthwonns removed litterthree times faster than other invertebrates, themost important of which appeared to beCollembola, Enchytraeidae and Diptera larvae.Oribatids, although numerically abundant didnot appear to be important in the breakdownof litter.

The role of soil animals in litter breakdownand the development of humus forms may beclearly seen by comparing three moorlandsoils in northern England. Their pedologicalfeatures were studied by Barratt (1960) andtheir fauna by vVocd (1963). The soils are,a mull-like rendzina developed from limestoneand found under Sesleria caerulea (L.), abrown earth of low base status developed fromheavy textured, shaley drift and found underFestuca-Agrostis, and a gleyed, weakly podsolicbrown earth developed from similar driftmaterial and found under N ardus grassland.These are sites III, IV and V respectively inTable 1 and Figs. 1 and 2. The activities ofsoil fauna may be considered in relation to thedifferent processes influencing the fate of plantmaterial:

1. Accumulation of litter2. Comminution of litter3. Incorporation with mineral soil-

(a) mechanical incorporation(b) chemical incorporation involving

the formation of "clay-humuscomplexes" .

The mull-like rendzina is a shallow (8cm.),black, A/C soil developed on Carboniferouslimestone. There is no surface accumulationof litter, and initial comminution of the denseSesleria tussocks appears to be due to the densepopulation (about 3,OOO/m.') of snails (fivespecies, the most abundant of which is Lauriacylindracea da Costa) which feed principallyat the soil surface and in the base of the tus-socks. These snails skeletonise the plant materialand produce a mass of fine, black excrement.Further comminution .of vegetable debris andits thorough incorporation with mineralmaterial (calcite) can be largely attributed towoodlice, (Oniscus asellus L.) aided by a small,

83

specialised earthworm fauna (Lumbricusfestivus (Sav.) and Allolobophora chlorotica(Sav.) ). The effectiveness of woodlice in com-minuting plant material and incorporating itwith mineral soil is evident from laboratorycultures where these animals rapidly converta loose mixture of soil and plant litter into amass of cylindrical droppings. Under fieldconditions factors such as high rainfall andthe activities of earthworms are probablyrcsponsible fcr the rapid breakdown of thisexcrement. The absence of clay minerals fromlimestone weathering precludes the formationof clay-humus complexes, and the humus fabrichas the appearance of a mull-like rendzinamoder.

The brown earth and the podsolic browncJrth are developed on heavy-textured, non-calcareous, shaley drift (30- 70 cm. deep), andhave acid (pH 3.5-4.8) surface horizons. Thereis no accumulation of litter in the brovvn earth,although there is a distinct organic-rich Athorizon. Comminution of plant material islargely caused by insect larvae, living pre-dominantly in the At horizon, and earthworms(about 300/m.'). The fabric of the A, horizonis a mull-like model' of which the dominantconstituents are the excrement of insect larvae. .particularly that of larvae of Bibionidae (Bibiolepidus Loew, > 3,OOO/m.') in which organicand mineral material are mixed. Surface-active earthworms, of which the most abundantare Eisenia rosea (Sav.) and Allolobophoracaliginosa (Sav.), give a superficial mull-likeappearance to this horizon, and the pre-dominantly coprolitic nature of the fabric isevident only in microscopic preparations. Theworkings of Lumbricus terrestris L. and to someextent A. caliginosa are evident in the A2 andB horizons of the soil where the fabric hasthe appearance of a weak mull humus.

The accumulation of dead and partly decom-posed plant material in distinct L, F and Hlayers in the gleyed podsoJic brown earth canbe related to the absence of effective com-minuting agents such as earthworms« 35/m.') and saprophagous or phytophagousDiptera larvae. The L layer has a raw humusfabric consisting almost entirely of undecorn-posed Nardus litter with abundant fungalhyphac and little animal excrement. Partlydecomposed plant material is the dominant con-stituent in the F layer, but there is somecomminution and. in microscopic preparations,excrement of micro-arthropods is evident. In

S4 ''''ODD: THE FAUNA OF GRASSLAND SOILS

the H layer decomposition is more completeand the excrement of micro-arthropods lessdistinct, possibly because of their destructionby enchytraeids and Diptera larvae, althoughthere is no apparent incorporation of organicilnd mineral material. The fabrics in the Hand F layers are coarse (silica) mocler and fine(silica) model' respectively.

These three soils occur within a distance of250 yd. That they have very similar popula-tion densities of micro-arthropods and ofEnchytraeidae suggests that when other inver-tebrates are abundant, as in the mull-likerendzina and the brown earth, these groups ofanimals (the meso-fauna) have little pedo-logical significance. The three processes.,enumerated above, influencing the fate of plantmaterial may now be considered in the light ofour knowledge of the fauna of these three soils.In the absence of comminution and incorpora-tion, litter accumulation leads to raw humusformation (L layer, gleyed podsolic brownearth); accumulation and comminution with-out incorporation leads to moder formation(F and H layers, g]eyed podsolic brown earth);comminution and mechanical incorporationproduce mul1-like model' fabrics (mul1-likerendzina and A, horizon of the brown earth)and, with chemical incorporation, lead to mullformation.

Contribution to total soil metabolism

The pedological approach emphasises mor-phological aspects of the effects of soil animalson soil; and, of the many hundreds of speciesof invertebrates present in most soils, only afew are of direct pedological significance.Another approach to assessing the significanceof a particular species or group of soil animalsis to study its position in the "food web", thusassessing in a qualitative way its contributionto the circulation of nutrients through the soil.No such food web has been constructed for soilanimals, but Brauns (1954) has shown howcomplex such relationships are among Dipteralarvae in forest litter. Macfadyen (1963) hasattempted to overcome these complexities byestimating the flow of energy at various trophiclevels in a grazed meadow. He estimates thatabout 80-90 per cent. of the total soilmetabolism stems from micro-organisms(bacteria, protozoa, etc.) and the remaining10-20 per cent. from soil animals. of whichthe small decomposers (Acari, Collembola,Enchytraeidac, Nematoda) contribute two

fifths, that is, less than 10 per cent. of thetotal. However, he (1961, 1963) suggeststhat the activities of these small arthropodsmay have indirect effects on the total soilmetabolism far greater than the direct effectsof their own metabolic rates. This could arisethrough stimulation of microbial activityby means of distribution of spores, eliminationof mycostasis and bacteriostasis and the en-couragement of microbial growth by grazingon senescent colonies. If this hypothesis istrue, the effect of insecticides in inducingquantitative and qualitative changes in soilfauna is likely to be reflected in changes insoil fertility. On the one hand the markedreduction in saprophagous micro-arthropodsafter the application of certain insecticides, suchas BHC (Sheals 1956), could result in adecrease in total soil metabolism and thelocking up of energy in the form of undecom-posed plant debris. On the other hand, certainsaprophagous micro-arthropods, such as Collem-bola (Satchell 1955; Sheals 1956) are notaffected by DDT, whereas predaceousarthropods such as Mesostigmata and variousColeoptera are kiUed and the significantincrease in Collembola populations followingapplications of DDT (Sheals 1956) could resultin an increase in energy flow and liberation ofnutrients.

REFEHENCES

BAl\M'tT, B. c., 1960. An investigation of the morphologyand development of some grassland humus forms.Ph.D. Thesis, University of Durham.

BARRATT,B. c., 1964. A classification of humus formsand micro-fabrics of temperate grasslands. J. SoilSci. 15: 342-56.

BRAUNS, A., 1954. Terricole Dipterenlarven. Unter-suchungen zur angewandten Bodenbiologie G6t-tingen Frankfort, Berlin. 1; 179 pp.

DAVIS, B. N. K., 1963. A study of micro-arthropod com-munities in mineral soils near Corby, Northants.J. Anim. Ecol. 32: 49-71.

DHILLON, B. S., and GIBSON, N. H. E., 1962. A studyof the Acarina and Collembola of agricultural soils.Pedobiologia 1: 189-209.

DRIFT, J. VAN DEn, 1951. Analysis of the animal com-munity of a beech forest floor. Tijdschr. Ent. 94;

1-68.EDWARDS, C. A., and HEATH, G. ,~,r., 1963. The role of

soil animals in breakdown of leaf material. Soilorganism (ed. Doekscn and van del' Drift): 76-84.North-Holland, Amsterdam.

FENTON, G. R., 1947. The soil fauna: with special refer-ence to the ecosystem of forest soiJ. J. Anim. Ecol.16, 76-93.

FORD, J.. 1937. Fluctuations in natural populations ofCollembola and Acarina. J. Anim. Eeal. 6; 98-111.

\V 000: THE FA UN A OF GHASSLAND SOILS 85

FRANZ, R., 1963. Biozonotische unci synokologischeuntersuchungen ubcr die Bodenfauna und ihrebeziehungen zur Mikro--und Makroflora. Soilorganisms (ed. D02ksen and van del' Drift): 346-66. North Holland, Amsterdam.

l'RENZEL, G., 1936. Untersuchungen fiber die Tierwcltdes Wiesenbodens. Gustav Fischer, Jena. 130 pp.

GISIN, H., 1943. Okologie and Lehensgemeinschaftcn del'collembolen in schweiz8rischen ExcursionsgebietBasels. Rev. Suisse Zool. 50: 131-224.

HAARLOV, N., 1960. Microarthropods from Danish soils:ecology, phenology, Oikos, Suppl. 3: 176 pp.

HAIRSTON, N. G., and BYERS, G. W., 1954. The soilarthropods of a field in southern Michigan: n studyin community ecology. Contr. Lab. Vert. BioI. Univ.Mich. 64: 37 pp.

JACOT, A. P., 1940. The fauna of the sOlI. Quart. Rev.BioI. 15: 28--58.

KLIMA, J., 1956. Strukturklassen und Lebensformen del'Oribatidcn (Acari). Oikos 7: 227-42.

KNULLE, W., 1957. Die Verteilung dcI' Acari: Oribateiim Boden. Z. Morph. Okol. Tiere. 46: 397-432.

KUBIENA, W. L., 1943. L'investigation microscopique del'humus. Z. Weltforstwirt. 10: 387-410.

KUI3IENA, W. L., 1953. The soils of Europe (Englishedition). Murby, London.

KUBIENA, vV. L., 1955. Animal activity in soils as adecisive factor in establishment of humus forms.Soil zoology (ed. Kevan): 73-82. Butterworth'sLondon.

KUHNELT, \1V., 1955. An introduction to the study ofsoil animals. ibid: 3-22.

MACFADYEN, A., 1952. The small arthropods of aMolinia fen at Cothill. J. Anim. Ecol. 21: 87-117.

M.'\CI~ADYEN,A., 1961. Metabolism of soil invertebratesin relation to soil fertility. Ann. Appl. BioI. 49:216-9.

MACFADYEN, A., 1963. The contribution of the micro-frmna to tot;11 soil J"Jlctf\holism. Soil organisms (e(LDoeksen and van del' Drift): 3-16. North Holland,Amersterdam.

MURPHY, P. W., 1953. Some aspects of the mesofaunalpopulations of moorland soils, with particularreference to the il((luence of certain members onthe pedology of S".1ch soils. D.Phil. Thesis, OxfordUniversity.

PSCHORN-VVALCHEIt, H., and GUNHOl.D, P., 1957. ZUI'

kenntnis del' Tiergemeinschaft in Moos~undFletchtenrasen an Park-uncI \"'aldbaiimen. Z.Morph. Okol. Tiere, 46: 342-54.

SALT, G., HOLIJCK, F. S.. RAW, F., and BRIAN, 1\1. V.,1948. The arthropod population of pnsture soiLJ. Anim. Ecol. 17: 139--52.

SATCI-IELL, J. E., 1955. The effects of BHC, DDT andparathion on soil f<luna. Soils and Fertilily 18:279-85.

SHEALS, J. G" 1956. Soil population studies I. Theeffects of cultivation and treatment with insecticides.Bull. Enl. Res. 47: 302-22.

SHEALS, J. G., 1957. The Coilemhola and Acarina ofuncultivated soiL J. Anim. Ecol. 26: 125-34.

SonENsEN, T., 1948. A method of establishing groups ofequal amplitude in plant sociology based onsimilarity of sp2cies content and its applicDtion toDnalysis of the vegetation of Danish commons.BioI. SkI'. 5: 1-34-.

STI\ENZKE, K., 1952. Untersuchungen iiber dieTiergemeinschaften des Bodens: Die Oribatiden undihre Synusien in den Boden Norcldeutschlands.Zoolo~ica 37: 1-172.,

'iVEIS-FOGH, T., 1948. EcologiC<l1 investigations on mitesand coliemholes in the soiL Nat. Jutland 1: 135-270.

''''000, T. G., 1963. The fauna of certain moorland soilsdeveloped on limestone and non.calcareous drift.Ph.D. Thesis, Nottingham University.

NOTES:

Salt, Hollick, Raw and Brian (1948): mean of 8 samples(Nov. only) (numbers 12-20), 12 in. deep; flotationextraction 0.1 mm. mesh. Cambridge, England.Brown eurth, ciay loam.

Macfadyen (1952): mean of 120 samples, 5 em. deep,corrected to depth of 15 em. from lVIacfadyen's date;Tullgren funnel extraction. Oxford, England.Organic peat.

Hairston and Byers (1954): mean of 35 samples, 8.5in. deep; Tuligren funnel extraction. SouthernMichigan, U.S.A. Brown earth, sandy loam.

Haarlov (1960): mean of 26 samples, 6 em. deep; Tull-gren funnel extractjon. Denmark. Brown carth,sandy loam.

vVood (1963): means of 20 samples, 8 cm. deep (III),or 12 em. deep (IV and V); Tuilgren funnelextraction. Yorkshire, England; IIl-mull-likerendzina, organic loamy sand; IV -bl"O'.sn earth,silty ciay loum; V-podsolic brown earth; organiclayered mor.

vVeis-Fogh (19"~8): mean of 270 samples, 5 em. deep,plots I to VII only; Berlese funnel extraction. Den-mark. Brown earth, sand.

Sheals (1957): mean of 40 samples, 6 in. deep; notationextraction, 0.15 mm. mesh. GlasgO\y, Scotland.Bro\'vn eorth, clay loam.

'Vood (unpub.): mean of 42 samples, 9 in. deep;notation extraction, 0.15 mm. mesh. Northumber.land, England. Brown earth, clay loam.

Dhillon and Gibson (1962): mean of 90 sumples 6 in.deep; Tullgren funnel extraction. Leeds, England.Brown carth, sandy loam.

Davis (1963): means of 36 samples, 3 in. deep correctedto depth of 9 in. from Davis' data; flotation extrac-tion, 0.15 mm. mesh. Northamptonshire, England.Brown earth, sandy clay.