Humus Form Classification

Taxonomk Classification of Humus Forms in Ecosystems of British Columbia

First Approximation

K. Klinka', R.N. Green', R.L. Trowbridge2 andL.E. Lowe3

'Ministry of Forests 3University of British Columbia Vancouver Forest Region 2357 Main Mall 355 Burrard Street University Campus Vancouver, B.C. V6C 2H 1 Vancouver, B.C. V6T 2A2

'Ministry of Forests Prince Rupert Forest Region P.O. Box 3369 Smithers, B.C.VOJ 2N0

1981

Province of British Columbia Ministry of Forests Canadian Cataloguing in Publication Data Main entry under title: Taxonomic classification of humus formsin ecosystems of British Columbia

(Land management report, ISSN 0702-9861; no. 8)

"Flrst approximation" Bibllography: p. ISBN 0-7719-8659-9

1. Humus - British Columbia. 2. Forest soils. British Columbla. I. Klinka, K., 1937- II. British Columbia. Ministry of Forests. 111. Series.

S592.8.T38 631.4'17'0971 1 C81-902262-2

:c :c 1981 Provlnce of Brltlsh Columbla

Publlshed by the Informatton Servlces Branch Mlnlstry of Forests Provtnce of Brltlsh Colurnbla Vtctorla. B.C V8W 3E7 Abstract

A hierarchical system for the classification of humus florms is proposed. The proposedsystem has been devel- osped because of difficulties encountered with previous systems in discriminating between humus forms, and in relating them toecosystems. It is based on earlier systems, but takes advantageof extensive recent field experience chained from the Ecological Classification Programme in British Columbia. The classification and methodology for description are based on morphologicalproperties of humusforms. Keys tothe taxa and descriptions of representative humus form profiles are presented and are intended as practicalaids to ordering knowledge,stimulating re- searchand improving interpretations about humus forms andecosystems. The classification is considered to be a first approximation andis open to refinement upon testing and further studies.

Non-conforming Materials ...... 44 Biota ...... 45 Soil Fauna ...... 45 Soil Flora ...... 47 Appendix I1 SAMPLINGMETHODS ANDOF ANALYSIS ...... 48 Sample Collection ...... 48 Sample Preparation ...... 48 Bulk Density ...... 49 Recommended Chemical Analysis ...... 51 1. Organic Fraction Analysis ...... 51 2 . Routine Analysis ...... 52 Appendix I11 SAMPLE OFTHE FORM USED IN HUMUS FORM DESCRIPTION ...... 54 Acknowledgements

Appreciation is expressed to those who offered gui- dance, assistance and support in preparing this first approximation. Valuablegeneral or specific comments were received from T.M. Ballard, Department of Soil Science, Universityof British Columbia; C. Tarnocai, Land Resource Research Institute, Department of Ag- riculture; T. Vold, Resource Analysis Branch, Ministry of Environment; and theEcological Program Staff, Min- istry of Forests, includingJ. Pojar (Prince RupertForest Region), F.C. Nuszdorfer(Vancouver Forest Region), W.J. Watt and C.A.S. Smith (Cariboo Forest Region),D. Lloyd and W. Erickson (Kamloops Forest Region), S.M. Hope and A.J. McLeod (Prince George Forest Region) and G.A. Utzig (Nelson Forest Region). Acknowledgementsfor assistance and co-operation are due to the members of the Working Group on Or- ganic Horizons, Folisols, and Humus Form Classifica- tion; to R.M. Laird, Ministry of Forests, for helping in preparing the final manuscript; to R. Carter and R.E. Carter for editing; toL. Skoda, Canadian Cartographics Ltd., and P. Frank, Ministry of Forests, for the preparation of the figures; toK. Valentine, Agriculture Canada, for photomicrography; and to L. Leclerc and K.L. Vil- lalobos, Ministry of Forests, for the typing and preparation of the manuscript. 1

readily determinable morphological features of humus Introduction forms (such as horizons, their thickness, colour, fabric, non-conforming materials and biota) for classification Background purposes. In addition to a detailed morphological de- Bernier’s (1968) descriptive outline of forest humus scription, some physical and chemical properties have form classification, adopted by the Canadian Soil Survey been determined.A meaningful set of chemical analyses Committee (Dumanski (ed.) 1978), has been used until for humus materials is still the subject of research. In recently by the British Columbia Ministry of Forests, in addition, how themorphological properties correlate classifying humus forms. Because humus forms can be with quantitative properties remains to be tested, and applied as differentiating oraccessory characteristics for precise definitions of class boundaries for horizons and various taxain the system of ecosystem classification usedtaxa still need to be determined by laboratory analyses. by the British Columbia Ministry of Forests, this classifi- The nomenclature employed for classes (taxa) at the cationsystem has greatly enhanced their ecological highest level of generalization is based on three interna- studies. However, during its decade of use, weaknesses tionally recognized terms: mor, moder and mull.Names havebeen exposed concerning definitions oforganic for taxa oflower level categories are formedby prefixing horizons, methods of describing humus forms, termin- modifiers, formed mostly fromGreek or Latinroots. ology, treatment of non-conforming materials, the defin-These modifiers suggest some of the more important ition of moder- humus forms, the tentative classification properties and, where possible, the taxonomic differ- status of humus forms associated with semi-terrestrial entiae for a particularclass. Such a system has been used andgrassland ecosystems, and inconsistencies in the consistently by Wilde (1966, 197 1) for humus forms and hierarchical structure. by Soil Survey Staff(197.5) in soil taxonomy. A reviewof existing c1a:rsificationsof humus forms used in the U.S.A. (Hoover and Lunt 1952, Wilde 197 1) Importance of the Taxonomy andin Europe (Hartmann 1952, Kubiena 19.53, Duchaufour 1960) indicated that they could not advan- Within the constraints imposedby both environmental tageouslyreplace Bernier’s system becausethey em- and management objectives, the general goal of forestry bodied similar weaknesses. In particular, the terms used management is to utilize and maintain the productivityof to describe and classify humus forms were found to be the ecosystems under- management and,when possible, inconsistent: expressions beingused internationally were to increase productivity. Because of the important rela- found to have two or more meanings, andthe same tionships belween the properties of humus forms and entities were known under several names. Doubts have forest productivity, meetingthis goal requires knowledge beenexpressed as towhether thesenames are really regarding humus forms and,in addition, a classification synonymous (Bernier 1968.. Howard 1969, Wilde I97 I). system which will permit the application of that know- Another difficulty is that even when the names of those ledge to similar humus forms in areas which have not humus formsrecognized by Kubiena ( 1953)or others are been studied in detail. The taxonomic classification, in employed, they are not applied uniformly. The same is other- words, provides an important tool which can be true of the horizon designation: the terms are not used used for developing interpretations for forest manage- uniformly nor do authorsclearly statehow they are using ment. The keys to the taxa and the descriptions of rep- the terms (Babel 197.5). resentative humus form profiles can be used as practical So, because of the weaknesses in the existing system aids in ordering knowledge and for improving interpre- andthose used elsewhere., the Ecological Programme tations about humus forms andecosystems. Staff’ suggested that a revision of Bernier’s classification Since 1975, the Ministry of Forests has been directing system be initiated. attention to the systematic development of a common scientific base for site (ecosystem)- specific management Approach of the forest resource (Schmidt 1978). The taxonomic classification system which is presented here is expected Ideally, a taxonomicclassification of humusforms to contribute to that goal. should ultimately be based011 the physical, chemicaland biological properties of humus forms which correlate readily with identifiable morphological properties. How- Synopsis ever, because of present inadequaciesin the existing data Inthe first part ofthis report, the taxonomicclassifica- base, purely morphological properties had to be used. tion of humus forms is presented. The methodsused to Thisapproach underlies ]most of the existing humus describe humus forms and the methodsof sampling and form classifications (Romell and Heiberg 193 1, Heiberg analysis are presented in Appendices I and 11. The clas- and Chandler 194 1, Mader 1953, Kubiena 1953, Barratt sification has beentested to a limited degree tosub- 1964, U’ilde I966 and 197 1, Bernier 1968). In particular, stantiate the significance of the differentiated units, and Romell and Heiberg ( 193 1 ;I, M‘ilde ( 1966 and 197 1) and the results have been encouraging. They are presentedin Babel (1975)have emphasized the importance of the the latter part ofthis report.

‘In the context of this study, the Ecological Programme Staff is a group of pedologists and ecologists responsiblefor an ecological classification programme carried out by the British Columbia Ministry of Forests. 2 Humus Form, Horizons and RelatedTerms Humus Humus Form‘ Humus, in a broad sense, refersto the complex organic The humus form, introduced by Muller (1878), is de- products of thedecomposition of plantor animal debris. fined as a group of soil horizons located at or near the These materials are more stable than their precursors, surface of a pedon, which have formed from organic and are generally dark incolour, colloidal, and com- residues, either separate from, or intermixed with min- monly associated with mineral constituentsin soil. In soils eral materials. Thus a humus formmay be comprised of in general, and particularly in organic material accumu- entirely organic, or both mineral and organic horizons. lating above the mineral soil surface, humus is closely The mineralhorizons which are included in humus associated with varying proportionsof undecomposed or forms are restricted to melanized A horizons character- semi-decomposed organic materials,which cannot prop- ized by a significant accumulation of organic matter from erly be termed humus.While “humus” is a valuable con- residues of root systems or theactivity of soil fauna, both ceptual term,in practical studiesit is often difficult(if not which may be associated with infiltration. Although or- impossible) to achieve a physical separation of humus ganic mattermay be foundin B andC horizons, theseare from other organic soil constituents. The term “humic not considered components of the humus form (Babel substances” is often applied to organic fractions isolated 1975, Barratt1964). Humus forms are considered from soil in the laboratory, andwhich are dominated by natural bodies, like the soil with which they are associ- materials with humus-like properties, butwhich may also ated. Inrelation to the rest of the pedon,they are charac- include substanceswhich do not meet the strict definition terized by the most intensivebiological activity. of humus. Humic substances includesuch operationally defined fractions as humic acid,fulvic acid and humin. Humus Form Profile The formationof humus is termed ‘humification’, and The sequence of organic ‘and mineral horizons in a subsequent modification of humus, involving oxidative humus form constitutes the humus form profile. This or otherchanges in chemicalstructure, can be referred to profile and its morphological and chemical properties as “maturation” of the humus orits fractions. are used in the classification of humus forms. “Forest floor” and “duff” are terms used by many It has been suggested that a definition of the smallest forest scientists and practitioners in North America to three-dimensional unit which canbe considered a humus designate humus forms and a kind of humus form, re- form is needed in order to provide a uniform taxonomic spectively. In this context, “forest floor” refersto organic basis. However, it is questionable whether its lateral di- materials that have formed at and near the mineral soil mensions should coincide with those for the pedon.Sev- surface and can include both humus and unhumified eral workers characterizing humus forms in British Col- material. “Duff’,in addition to a referenceto Corest floor umbia,Washington and Oregon noted their inherent in general, has also been used as a formative element in variability and indicated that the sequence and thickness naming the taxa of Mull humus forms, and is synony- of horizons in humus forms of forest ecosystems can mous with Mor in the systems of Rome11 and Heiberg change very abruptly. Thus, using a smaller lateral di- ( 193 I), Heiberg and Chandler (194 I) and Hoover and mension than 1 m for the humus formis appropriate. A Lunt ( 1952).The terms duff and forest floor areused not study investigating morphological variability of humus in the proposed classification. The term “forest humus” forms is in progress, but provisionally, a lateral dimen- has been used in the same sense as “forest floor” or its sion of 0.5 m is proposed. Thevertical dimensionis to the constituent layers, butwill be used here only to describe depth of the controlsection. true humus (see above) present in, or formed under a forest ecosystem. Control Section The continual interaction of all processes involved in The organic and mineral horizons that form at and humus and soil formation leads to the differentiation of near the surface of a pedon(Soil Survey Staff 1975, CSSC more orless distinct horizontal layers, termed horizons, which collectively constitutethe pedon.Both organic and mineralhorizons are recognized when describing a pedon. For the most part, organic horizons of mineral Hartmann (1952) and other workers applied in humus studies soils or, in the upper solum of organic soils can be de- the terms humus form and humus type. The definition of‘ signated as humus horizons, only if substantial transfor- humus form given by Hartmann agrees with that rendered above. The term “humus type” refers to the kind of humus mation of original compounds to humushas taken place. formation; i.e. to physical, chemical and/or biological processes controlling or influencing the formation of humus forms in a given ecosystematic setting. Hartmann recognized the zoogenous, fungal (mainly Eumycetes including Ascomycetes, Phycomycetes and Basidiomycetes), anaerobic, abiologic and aquatic types of humus formation. Evidently, a relationship exists between taxa ‘Duff- the intermediate layer, or the more or less decomposed at higher levels of our proposed classification and the humus organic matter, just below the litter (Waksman 1938). types, as defined by Hartmann. This follows from the selection

Duff mull - a tvDe/I of forest humus transitional between mull of differentiae for the taxa: the ‘IDroDerties that reflect the and mor (Glossary of Soil Science Terms, SSSA 1970). environment or resulting from processes of humus formation. 3

1978) constitute the control!section of humus forms. All entire control section, only if the mineral horizons organic horizons, but not all mineral horizons of the within the latter are enriched by organic matter, as control section makeup a humus form profile. previously defined. 1. In organic soils, the control section extends from the In the latter case the concept of the epipedon (Soil surface' to a depthof 40 lcm (e.g. it approximates the Survey Staff 1975) was adopted and the proposed25 cm depth at the surface tier used in the classification of thickness is over the minimum depth requirement used organic soils). If a lithic, paralithicor permafrost con- for most ofthe defined epipedons. The controlsection as tact, or fragmental materials occur at a depth shal- defined above is adequate to characterize humus forma- lower than 40 cm, the controlsection extends from the tion in mineralsoils. surface to the contact (Fig. la). In thesecases, the control sectionis identical to the humus form profile. Horizons The classification of humus forms is based on the des- aorganic soils criptions of organic and mineral horizons in a humus {ground surface form profile.A soil horizon has been defined as a layer of organic or mineral soil mattrial approximatelyparallel to '"E the ground surfacewith characteristics produced by soil 20 forming processes (Soil Survey Staff 1975, CSSC 1978). The horizons in the humus form profile manifest the genesisand properties of humusforms and alsoin- fluence those of the whole soil. Since the definitions of taxa arebased on thekinds, sequence, and properties of horizons,the precise definitions and designations of the horizons in the humus form profile are essential to classification. - y//I control section Designations for Horizons Capital letters are used for master horizons. Theyin- b mineral soils clude L, F, H, 0 and A (horizons), indicating dominant kinds of organic materials degree ofcomposition, or enrichment of organic matter. Inaddition to the master horizons, the S layer (Forsslund 1945)is adopted. Thislayer is one containing a dense mat of living bryophytes (e.g. Sphagnum) in the humus form control section. However, it is not used for classification. Lowercase letters are used as suffixes to indicate variations in the range of propertiesof master horizons. If a horizon designated by these symbols is further subdivided vertically, the subdivisions are indicated by placing an arabic number after alowercase suffix. If no Figure 1. Control section of humus forms in organic lowercase suffix is suitable to indicate a specific attribute (a) and mineral soils (b). of a horizon, an arabic numberis placed after the capital letter (e.g. F 1) and thereason for the subdivision is exp- lained in the horizon description. Transitional horizons, 2. In mineral soils, the control section extends from the whose parts cannot be conveniently separated, are de- surface to a depth of 25 cm beneath the boundary signated by a combination of capital letter symbols (e.g. betweenorganic and mineral horizons. If a lithic, FH). paralithic or permafrost contact, or fragmental mate- There is a need to improve conventions governing the rials occur at a depthless than 25 cm from the organic/ use of symbols to indicate variations within master or- mineral horizon interface, the controlsection extends ganic horizons. When comparedto mineral horizons, the fromthe surface to the contact (Fig. Ib). In these absence of provision for morespecific characterizationis cases, the humus form profile corresponds with the striking. Therefore, the consistent use of lowercase suffixes for all organic master horizons is recommended. Definitions for thesubdivisions follow. ' The soil surface is interpreted here as the surface of the first soil horizon. Although in most cases the soil surface is identical to Definitions of Master Horizons the ground surface, in some ecosystems the ground surface may be continuously or discontinuously covered by materials Four master organic horizons arerecognized: L, F, H, which are not considered to be a part of a soil horizon, either and 0; themaster mineral horizon is A. Anorganic due to their nature (eg a layer of live S~hagnummosses) or horizoncontains more than 17% organiccarbon (ap- location in relation to the ground surface (e.g.partly detached proximately 30% organic matter) by weight in the min- or suspended organic residues). eral soil fraction finer than 2 mm. 4

The CSSC (1978) recognizes two groups of master The following definitions were proposed to the Expert organic horizons: theL, F, and H, and 0 horizons. The L, Committee onSoil Survey by Trowbridge (1980). F, and H horizons are terrestrial (upland) master organic horizons of most mineral soils and the Folisol (Folists)’ L - (litter, foma): aterrestrial master organic horizonconsist- great group of the Organic order. The 0 horizon is a ing of relatively fresh organic residues in which virtually entire original structures are discernible. May be discol- semi-terrestrial (wetland) master organic horizon of the oured and show some signs of biotic activity but is not Fibrisol(Fibrists), Mesisol (Hemists)and Humisol substantially comminutedand does not show macroscopi- (Saprists) great groups of the Organic order.may It also cally obvious signs of decomposition. overlie mineral horizons of the Gleysolic order (“aqu” subordersthat have an aquic moisture regime) and The organic materials of the L horizons appear as gleyed subgroups of other orders. These groups have recently fallen foliage, twigs, wood and other detached been separated according to origin of minerals and soil organic materials and forma layer approximately paral- moisture regime’. It is difficult at times to designate an lel to the ground surface. Thus,in pedons that have anL organic horizon in one or the otherof these two groups horizon, the ground surface coincides with the soil sur- given present definitions and criteria. Furthermore,L, F, face. These materials are essentially unaltered, but, oc- and H, and 0 master organic horizonsmay develop in a casionally, they may be discolouredand leached of most conlmon humus formprofile. Although not statedin the of the solubleconstituents. Abiological disintegration CSSC (1978), pedologists usually use a combination of and chemical alteration (Babel 1975) may be very slight. several criteria to judgeif the organic horizonbelongs to Rooting is absentin the L horizons. The L horizons either of these two groups. These criteria are presented correspond in part to the 0 1 horizon (Soil Survey Staff in Table 1. 1975).

?‘ABLE 1. Gudelinesfor the Dijferentiation of Organic Master Horizons (aJier Trowbndge 1980)

I,, F and H horizons 0 horizons Criteria [Terrestrial (upland) [Semi-terrestrial ecosystems] (wetland) ecosystems] Physiography Generally sloping to level Generally depressional Soil moisture regime Very xeric to(hygric)’ (hygric) to subhydric to (hydric) Drainage class ofthe underlying Rapid to imperfect (canbe poor Poor to very poor mineral soil to very poor) Water table Absentin horizons(may fluctuate in At or nearsoil surfacefor a significant responsewaterto input) duration during frostthe free period (may declineduring growing seasondue to evapo-transpiration,not. drainage) Dissolved 02 Present Absent or present Origin of materials Non-hydrophytic vegetation Hydrophytic vegetation Biota Predominantlyaerobic; fungal mycelia Anaerobic (few flora or faunaobserved and/or actinomycetescommonly present, beneath surface) mites and springtails present at some time during year

‘Parenthesis indicate featuresor attributes of less significance.

‘Names of soil taxa in parenthesis in this study refer to Soil warmer) regional climate. Thisis in contrast to other schemes Taxonomy (Soil Survey Staff 1975). The names of soil taxa of characterizationof soil moisture regimes whichfeature abso- preceding the parenthesis refer to the Canadian System of Soil lute scales (Soil Survey Staff 1975, CSSC 1978). A functional Classification (CSSC 1978). approach to the characterization of the nature of soil moisture 2Soil moisture regime (hygrotope; Pogrebnyak 1930, Krajina regimes, has beenproposed, i.e. by variations in available water 1969), refers to the available soil water for plants. Nine classes as it changes with the seasons, and by relationships to climate (very xeric, xeric, subxeric, submesic,mesic, subhygric, hygric, and plant growth. This approach, based on Thornthwaite’s subhydric, and hydric) on the relative and qualitative scale haveconcept (Thornthwaite 1948, Thornthwaite and Mather 1955, been usedin characterizing soil moisture regimes of ecosystemsThornthwaite et al. 1957) of balancing water added to eco- within the context of a biogeoclimatic subzone, representinga systems by precipitation against losses by evapotranspiration, regional climate. Therefore, there is a unique set for each was used by Major ( 1963),Soil Survey Staff( 1975),Klinka et al. regional climate;e.g. a xeric class in one regional climate is not ( 1979),and is currently being tested atthe Soil Science Depart- identical to the xeric class in another (drier, wetter, cooler or ment of the Liniversity of British Columbia. 5

F - (formultningsskiktet, fermented,’ decayed materials): a Lowercase Suffixes master organic horizon characterizedby more-or-less disintegrated plant residues’ in which partial (rather than Lowercase suffixes are used to indicate variations in entire), macroscopically discernible vegetativestructures the range of properties of master horizons. Selected let- are dominant. ters were notalways connotative because of overlapswith The remainsof more-or-less disintegrated organic lowercase suffixes for mineral horizons used by CSSC materials may be identified as to their origin, but macro- (1978). The use of duplicate letterswith different mean- morphological decomposition is very apparent. The or- ings for organic and mineral horizonsis clearly undesir- ganic material may be comminuted by and may contain able.Therefore, the followingletters were chosen to excrement of soil fauna and/or permeated by fungal apply tospecific master organic horizons:0, v, q, a, r, and hyphae. Roots are commonly present in the F horizons, d. Lowercase suffixes may also be applied to any organic particularlyin forest ecosystems.Brownish-yellow to horizons without restrictions. The following Greek let- brownish-red macroscopicallyrecognizable plant resi- ters were chosen to represent these suffixes: p (beta), dues either predominateor are equivalent to organic fine L (iota), 8 (theta), X (lambda), and u (sigma). substances‘. The F horizons correspond partly to the0 1 Organic horizons represent an entity completely dif- and 02horizons (Soil Survey Staff 1975). ferent from mineral horizons. For this reason, and for H - (humus materials): a terrestrial master organic horizon eliminating any overlap with mineralhorizon desig- dominated by fine substances in which theoriginal struc- nations, it is proposed that letters of the Greek alphabet tures aremacroscopically indiscernible. be used for all lowercase suffixes of master organichori- The organicmaterials in the H horizons may be com- zons. Such a proposalis included for considerationin the minuted by and contain excrementof soil fauna, and/or following definitions of subordinate horizons: permeated by fungal hyphae. Microbiotic activity is gen- Lo - [original, new (Babel, 1975): proposed suffix - v (“nu”)]: erally consideredto be high. Black-brown to nearlyblack an L horizon composed of newly accreted organic mate- finesubstances predominate overplant residues and rials. These materials are usually loose, show no struc- rooting is generally common. Except for root residues, tural change, may be slightly discoloured,and are found the plant residues are not recognizable macroscopically on the ground surface, particularly during and after the or only in small amounts. The H horizons correspond growing season. partly to the 02horizons (Soil Survey Staff 1975). Lv - [variative (Babel, 1975): proposed suffix - w (“omega”)]: 0 - (“organic material^")^; a semi-terrestrial master organic an L horizon composed of less recently accreted organic horizon. materials, usually showing some abiological disintegra- The 0 horizons are characteristically associated with tion and strongdiscolouration. semi-terrestrial(wetland) ecosystems.Consequently, Fq - [non-connotative:proposed suffix - p (“mu”)]: an F humus formingprocesses are influenced by a water table horizon which is composed primarily of macroscopi- at or near thesoil surface for a significant duration dur- cally recognizable,structurally well-preserved, plant re- ing the frost free period. The 0 horizons may also be sidues. The materials have a matted banded fabric in- found in terrestrial (upland) ecosystems in which com- terwoven by abundant fungal hyphae. Faunaldroppings pensating edaphic factors provide for non-freely drained or dropping residues are either absent or found only in organic horizons. small amounts (Figure 2). A - a master mineral horizon containing 17% or less organic carbon (about 30%organic matter)by weight. It is formed at or near the soil surface in the zoneof leaching or eluvia- tions of materials in solution or suspension, or of maximum in situ accumulati’on of organic matter or both (CSSC 1978).

‘The strict definition of the term“fermented” implies processes not found in terrestrial humus forms andwas originally usedby Pasteur to designate anaerobic processes, or “life without oxy- gen”. However, it hascome to mean the decompositionof carbohydrates with the evolution ofgas or the formation of acid or both (Waksman 1938) and is used extensively in literature pertaining to this horizon. *Babel ( 1975) defined “plant residues” as coherent tissue parts which are recognizable, as such, microscopically; “organic fine Figure 2. Poorly decomposed plant residues showing matted substances” (hereafter, “finesubstances”), refers to organic structure characteristic of an Fq horizon. Fungal my- materials without definite microscopically recognizable struc- celia are common throughout (Orthihemimor). tures. Cell wall fragments, small pieces oftissue comprised of a few cells, and fragments of fungal hyphae are included. The maximum size is approximately 100,~. Organicfine sub- Fa - [non-connotative:proposed suffix - r#~ (“phi”)]: an F stances do not correspond (entirelyto colloidal substances, horizon which is composed primarily of macroscopi- which a of 1p. have maximim size cally recognizableplant residues which havebeen partly 3The term “organic” should not be used as a synonym for this fragmented or comminuted by soil fauna.The materials horizon. are loose, not matted; fungal hyphae may be found in small amounts. Faunal droppings and dropping resi- Hd - [decomposed: proposed suffix - 6 (“delta”)]: an H hori- dues are numerous and can be easily observed under zon in which organic fine substances predominate with magnification (Figure 3). very few plant residues. Their colours are usually dark gray-brown or black. Hda - [proposed suffix -6+ (“delta, phi”)]: an H horizon in which organic fine substances predominate. Droppings resulting from active populations of soil fauna constitute almost the entire fabric. The criteria proposed as guidelinesto dif-ferentiate between the Hr and Hdhorizons are presented in Table 2: The following subordinate 0 horizons are used; the definitions are those ofCSSC (1978): Of - (fibric, Oi - Soil Survey Staff 1975): an 0 horizon that consists largely of materials thatare readily identifiable as tobotanical origin.It has 40% or more rubbedfiber by volume and a pyrophosphate index of 5 or more. If the rubbed fiber volume is75% or more, the pyrophosphate criterion does not apply. Fiber is definedas the organic Fzpre 3. Partiallydecomposed plant residues showing very material retained on a 100-mesh sieve(0.15 mm) except weak structure characteristic of an Fa horizon. Insect for wood fragments that cannot be crushed in the hand droppings are common throughout (Oryhilepto- and are larger than 2 cm along the smallest dimension. moder). Rubbed fiber is the fiber that remains after rubbing a sample about 10 times between thumb and forefinger. Faq- [proposed suffix -c#+ (“phi, mu”)]: an intergrade F hori- Fabric materials are classified in the von Post scale of zon in which the materials show the presence of both decomposition as class 1 to class4. fungal hyphae and faunal droppings. Droppings and Om -’ (mesic, Oe - Soil Survey Staff1975): an 0 horizon consist- dropping residues increase toward thelower part of the ing of partly decomposed materials whichare at a stage F horizon. of decompositionintermediate between fibricand Babel (1975) proposed two subdivisions of the F hori- humic materials. The mesic material is partly altered zon: Fr (a high ratio of plantresidues to fine substances) both physically and biochemically and is usually clas- and Fm (a medium ratio of plant residues to fine subst- sifiedin-thevon Post scaleof decomposition as class 5 or 6. The Om horizon does not meet the requirements of ances). In this study the discrimination between the Fq either the Of or Oh horizons. and Fa horizons was considered to be more significant Oh - (humic, Oa - Soil Survey Staff 1975): an 0 horizon in than that based on the degree of decomposition. How- which the original organic materials have been trans- ever, Fq,Fa and Faq horizons can be further subdivided formed intohumic materials. This horizon has the low- according to the degree of decompositionby placing an est aqount of fiber, the highest bulk density and the arabic number after therespective lowercase suffix. lowest saturated water-holding capacity of the 0 hori- Hr - [residues: proposed suffix - p (“rho”)]: an H horizon in zons. It isvery stable and changes verylittle physically which macroscopically recognizable plant residues or chemically with timeunless it is draihed.The rubbed from fine roots, wood and bark (rarely foliage) are pre- fiber content is less than 10%by volume and the pyro- sent but do not predominate over fine substances. Yel- phosphate index is 3 or less. Humic materials are us- low, brownand particularly red colours or their combi- ually classified inthe von Post scale of decompositionas nations often prevail. class 7 or higher and very occasionally as class 6.

TABLE 2. Guzdelinesfor the Dffoentiation of Hr and Hd Horizons

Criteria Hr Hd Materials Fine substances predominate; macroand micro Fine substances clearlypredominate; macroscopically recognizable plant residues which scopically recognizable plant residuesare very disintegrate upon rubbingare common; dark few or absent; dark coloured materialsrub coloured materials do not rub out onfingers out on fingers Colour At leastone but oftentwo huesredder than the Not as red asthe 2.5 YR.; usually verydark gray underlying Hd, if present; colours oftenin the or nearly black 2.5 YR hue, usually reddish brown Structure Generally fineto medium, blocklike Generally massiveor coarse, blocklike Character Slightly greasy when moist Very greasy when moist Bulk Density Lower; similar to F horizons Higher; generallyless pore space than in F horizons 7

The followingsuffixes are used with theA master fine (colloidal) organic materials. The suffix “d ” is mineral horizon (the definitions and usagefollow CSSC used alone with H (Hd ) and 0 (Od ) master organic 1978): horizons. Ah - an A horizon enriched with organic matter; it hasa color Table 3 gives a synopsis of horizonsconstituting a value less than 4 and at least one unit lower than the humus form profile and demonstrates how lowercase underlying horizon and 0.5% more organic carbon than IC. suffixes are used. The Ah horizons canbe further suffixed usinge (eluvi- ated, Ahe); j - (incipient, weakly expressed, Ahj): p - TABLE 3. Synopsis of‘ Organic Horizons Constituting a Humus (disturbed by man’s activities, Ahp); u - (disturbed by Form Profile and Usage of‘lowercmeSujjxes

physical or faunal processes other than cryoturbation, ~ ~ Ahu); y - (cryoturbation, Ahy). Subordinate Horizons RestrictedUnrestricted Lowercase Suffixes The use of Greek letters as lowercase suffixes are not Master Lowercase restricted to any particular horizon layer or in the humus Horizons Suffixes Alone In combination form profile. They are definedas follows: L Lo LA, Lr fl - [(beta) burned]: a horizon in which organic material is Lv Lve , LVA predominantly (>50% volume) or entirely charcoal. It is used with subordinate horizons of F, H and 0 master Fq Fqh , Fqc , FqP, FqO F Fa organic horizons (e.g. (FqQ) to indicate a predominance FA , Fr , Ffi Fah , Far , Fafi Faqh , Faqc , Faq@ of charcoal materials, or with F (FQ) and H (He ) alone, Faq to indicate “charcoala horizon”. Hr Hrh , Hrr , Hrfl I - [(iota) incorporated inorganic materials]: anorganic hori- H Hd HA ,Hr ,HP, HdX , Hdc , Hdp zon in which organic materials are intermixed with min- Hda He ,Ha, HdaX , Hdac , Hdao eral particles finer than 2 mm. It contains more than Of Ofh , Of6 , Of@ 17% but less than 35% organic carbon by weight. It is 0 Om Oa OmX , Om1 ,Om@ used with subordinate horizons of L, F, H, and 0 organic Oh OhX , Ohc , Ohp horizons (e.g. HI )’. Thisintermixing of mineral particles with organic materials may result from several different processes (or Horizon Combinations their combination). The process should be indicated in the description using thefollowing terms: Wilde (1958, 1966, 197 1) introduced several terms for various general combinationsof horizons includedin the 1. Colluvial humus formprofile. The following terms were adopted: 2. Eolian 3. Alluvial ectorganic - apart of ahumus form formed by 4. Cryoturbation organic horizons, referred to collec- 5. Silvoturbation tively as ectorganic horizons; 6. Zoological endorganic - a part of a humus form formed by Ah e - [(theta) non-connotative]: an organic horizon which is horizons,referred to collectively as comprised almost entirely of fungal mycelia. The colour endorganic horizons; is generally light grey; consistence and character are holorganic - a humus formformed entirely by a resilient andfelty respectively. It is most often used with combination of organic horizons; and Fq horizons as partially decomposed plant residues are usually incorporated. It may be used with H master amphimorphic - a humus form formed by a combina- horizons where applicable.. tion of organic and mineralhorizons. a - [(lambda)ligneous]: an organic horizon or layer in which The endorganicAh horizons are enrichedby residual, organic material is predominantly (>50% by volume) incorporated or infiltrated organic matter. Incorpora- wood in variousstages of decomposition. It is used with tion or intermixing may occur by several processes des- subordinate horizons of I., F, H and 0 master organic cribed previously. Infiltration of solid organic matter by horizons (e.g. Of A) to indicate a predominance of de- rain water is a process by which great amounts are trans- caying wood, or with L (L X ), F (F X ), and H (HA ) alone, to indicate “decayinga wood horizon”. ported in all humus forms (Babel 1975). Podzolic B horizons that are enrichedwith precipitated humusmaterials u - [(sigma) organic sediments]: an organic horizon that due to the movementof dissolved organic matter along has developed by sedimentation usually containing with sesquioxides are not considered endorganic.

‘He horizon currently under !study. Percent ash may prove to be a more meaningful distinguishing characteristic. 8 Humus Form Classification

The purpose of humus formclassification is to organ- The Outlineof the System ize knowledge about humus forms. Theobjective of the proposed taxonomic classification of humus forms is to A synopsis of the three-category taxonomic classifica- create a hierarchy ofclasses which permit an understand- tion is presented in Table 4. In order of decreasingcate- ing,within constraints of present knowledge, of the gorical rank and increasing number of differentiae, the natural relationships between humus forms and thefac- categories are “humusform order”, “humus form tors involved in their formation. Inthis first approxima- group” and “humus form subgroup.” These are simp- tion the differentiae chosen for theseclasses are proper- lified in the text to “order”, “group” and “subgroup”, ties which are observable in the field or inferred from respectively. other propertiesobservable in the field. An attempt has been made to providetaxa for all Categories humus forms known to occur in British Columbia and The attributes which were considered to result from other places under theinfluence of comparableclimates. the genesis of humus forms wereselected for the charac- However, some humus forms have not yet been ade- terization of orders and groups;whereas those thought quately described and studied. When reasonable defini- to be important to plant growth butof less significance to tions and predictions from other workers wereavailable, genesis were selected for subgroups and phases. they were included in the system.Efforts were made to Thus,the taxonomic differentiae for orders and define each taxon explicitly, to identify meaningful and groups are based on the presenceabsence or of diagnos- useful class boundaries and to select thoseproperties tic organicand mineral horizons (ie. a characteristic which are useful as taxonomic differentiae. humus form profile), relative thickness of the horizons,

TA1% [.E 4. A Synopsis of Humus Form Taxa

Order Group Subgroup Group Order, Subgroup 1. Mor 1 1. Velomor 1 1 1. Orthivelomor 23. Mormoder 23 I. Orthimormoder I 12. Neovelomor <“2.32. Humimormoder 1 13. Amphivelomor 233. Mineromormoder 12.Xeromor 12 1. Orthixeromor 234. Amphimormoder 122. Lignoxeromor 24. Leptomoder 241. Orthileptomoder 123. Amphixeromor 242. Hemileptomoder 13.Hemimor 13 1. Orthihemimor 243. Mineroleptomoder 132. Mycohemimor 244. Amphileptomoder 133. Lignohemimor 25. Mullmoder 25 1. Orthimullmoder 134. Amphihemimor 252. Vermimullmoder 14. Hemihumimor141. Orthihemihumimor 253. Rhizomullmoder 142. Mycohemihumimor 26. Hydromoder 26 I. Orthihydromoder 143. Lignohemihumimor 262. Ectohydromoder 144. Granulohemihumimor 263. Saprihydromoder 145. Residuohemihumimor 27. Histomoder 27 1. Orthihistomoder 146. Amphihemihumimor 272. Fibrihistomoder 15. Humimor 15 1. Orthihumimor 273. Saprihistomoder 152. Mycohumimor 274. Hydrohistomoder 153. Lignohumimor Mull3. 3 1. Rhizomull 3 1 1. Orthirhizomull 154. Granulohumimor 3 12. Crustorhizomull 155. Residuohumimor ?I 13. Vermirhizomull 156. Amphihumimor 3 14. Xerorhizomull 16. Hydromor 16 1. Orthihydromor 32. Vermimull 32 1. Orthivermimull 162. Residuohydromor 322. Microvermimull 163. Hemihydromor 323. Macrovermimull 164. Saprihydromor 33. Hydromull 33 1. Orthihydromull 17. Histomor 17 1. Orthihistomor 332. Humihydromull 172. Fermihistomor 333. Saprihydromull 173. Saprihistomor 34. Saprimull 34 1. Orthisaprimull 174. Hydrohistomor 342. Parasaprimull 2. Moder 2 1. Velomoder 2 1 1. Orthivelomoder 343. Histosaprimull 2 12. Minerovelomoder 344. Humisaprimull 2 13. Amphivelomoder 345. Hydrosaprimull 22.Xeromoder 22 1. Orthixeromoder 222. Mineroxeromoder 223. Amphixeromoder .-~ 9

and features of humus forms that are indicative of the ment “orthi”is used for the subgroup that represents the dominant sets of humus-forming processes. Orders are centralconcept of the group. Each “orthi”subgroup differentiated by horizon combinations and by the kind exhibits a clear expressionof all diagnostic properties of of F horizon in the humus form profile inferred to be theorder and group to which it belongs; therefore, indicative of essential differencesin the natureof humus “orthi” subgroups have neither transitional propertiesto formation (Le. mineralization(decomposition of fresh another subgroup nor aberrant properties that require organic orsynthesized humus materials into simple solu- special recognition. Other formative elements designate ble compounds); humification(a synthesis of humus the subgroups that have,in addition to the properties of materials); and the kind ancl degree of incorporation of their group, some aberrant properties requiringspecial humus materialswith mineral soil. recognition. The subgroups presented in the synopsis The differentiae for groups vary with the order. In (Table 4) arenot the onlypossible subgroups in the general,they provide for segregation along the soil classification. Intergrade subgroups may be recognized, moisture gradient into xeromorphic, mesomorphic and i.e. those having properties of another subgroup in the hydromorphic humus form!<,and according to kind and same group. They are namedby prefixing two formative arrangement of horizons. These differentiaewere selec- elements used for the subgroups to the group name. ted to emphasize genetic homogeneity. Thus, the Lignohumimorswhich feature abundant fun- The subgroupswere intended toplace together humus gal mycelia or a mycelial layer are called Myco-Ligno- forms that have close similarities in kind and fabric of humimors. An illustration of the nomenclature as it re- materials and horizon sequence. There are threekinds of lates to the different categoriesin the system is as follows: subgroups: Mor ...... Order 1. subgroups that conformto the central concept of the Hemimor ...... Group group; Orthihemimor ...... Subgroup 2. subgroups that deviate from the central concept by Names of phases arepolynomial. They consist of one having aberrant, apparently genetically subordinate or more modified Latin or Greek adjectives preceding a features, and; subgroup, group or order name (Table 7). This list of 3. subgroups havingproperties intergrading to other adjectives indicates properties requiring recognition for subgroups or groups. interpretative purposes. For example, Humimors under Phases are used to provide flexibility in the system by the influence ofsubalpine-boreal a climate feature a high taking into consideration properties other than those bulk density, and are thus called Compactic Humimors. used to differentiate the taxa. These propertiesgenerally If they are also influenced by litterfall of yellow cedar, relate to plant growth or other management interpreta- rich in macronutrients, they have a higher base satura- tions. Phases of subgroups, groups and orders may be tion than that commonly found for Humimors; hence, recognized. they arecalled Eutrophic Compactic Humimors. Adjectives which describe formative elements used in the namingof groups and subgroupscan be also used for phasing.Thus, one can formthe term “LignicMor Nomenclature phase” to refer to all Mors with properties which are Nomenclature for the proposed classification was de- influenced by a high amount of decaying wood. To use veloped following the principles applied by Soil Survey “lignic” in this way is equivalent to creating an informal Staff ( 1975).The name of each taxon indicatesits position group (taxon). Adjectivesin names of phases are ar- in the classification, as well as its class in all categories of rangedaccording to interpretativesignificance. Re- which it is a member. Eitherexisting names were usedor dundancy in names of phases of subgroups should be new ones coined using formative elements andadjectives avoided. If a propertyis specified for a subgroup,which derived mostly from Greek orLatin roots. These forma- may or may not be used inits name, it should not be used tive elements and adjectives suggest prominent proper- in a phase name. Thefirst lettersin names ofall taxa and ties, preferably thoseused as taxonomic differentiae. their phases are capitalized. Three internationally recognized terms form the taxa The taxonomic class of a specific humus form can at the ordercategory level: hfor, Modorand Mull (Table firstly bedetermined by using thekeys, figures ofcharac- 4). Mor and Mull were described by Muller (1878). The teristic humus form profiles and definitions that follow. term Moder was introduced at a meeting of workers One should subsequently consult the definition of the studying humus forms in Eisenach in 1904 (Hartmann taxon with which one is concerned. The definition of the 1952). first group with the formative element “orthi”is followed Names of groups are formed by adding a formative by a description of the humus form profile. Analytical element to the name of the order (Table 5); names of data of some humus forms representing groups andor- subgroups are formed by adding a formative element ders is givenin the sectionentitled “Testing of the (Table 6) to the name of the group. The formative ele- Taxonomy”. 10

TABLE 5. Formative Elements in Names of Groups

Form ative element Formative ConnotationAdjective Hemi Hemic (Hemi) half; implying intermediate decomposition. It designates terrestrial Mors that have prominent F horizons. Histo Histic (Hirtos) tissue; implying the least and intermediate decomposition in the semi-terrestrial environment. It designates the Mors and Moders that feature well developed Of or Om horizons. Humi Humic Humus; implying the dominant presence of organic fine substances. It designates the terrestrial Mors that have a prominent H horizon. Hydro Hydric (Hydor) water; designates the humus forms formed under the influence of hygricor subhydric soil moisture regimes. Lepto Leptic (Leptos) thin, fine; refers to smalldroppings, dropping residues and exo- skeletons of soil mesofauna characteristic ofthe Fa horizon. It is used to designate the representativegroup of Moders. Mor Moric Implying properties of Mors. Mull Mullic Implying properties of Mulls. Khizo Rhizic (Rhiza) root; refers to the rhizogenous Ah horizon in Mulls. These Ah horizons are formed from the decomposition of roots of herbaceous plants, mainly grasses. Sapri Sapric (Sapos) rotten; implying most advanced decomposition. It designates semi-terrestrial Mulls with an Oh (or Ohr ) horizon formed under the influence of a sybhydricor hydric soilmoisture regime. Velo Velic (Velum) veil, curtain or covering; denotes thin ectorganic horizonsdom- inated by litter materials. Vermi Vermic (Vmir) worm; refers to the zoogenous Ah horizon in Mulls. Earthworms (Lumbnczdae) are the representative soil fauna. Xero Xeric (Xeros) dry; implying a xeric soil moisture regime. Xeric maybe used as the more generalclass including very xeric, xericand subxeric classesof moisture regime.

TABLE 6. Formative Elements in Names of Subgroups

Formative element Adjective Connotation Amphi Amphic (Amphi) of both kinds; designates amphimorphic Morsand Moders that have well developed endorganic horizons. Crusto Crustic (Crzlst) hard, crisp; designatesRhizomulls that have, in theupper portion of the humus form profile,dry, brittle and firm fabric. Ecto Ectic Ectorganic; indicates Hydromoders lacking Ah horizons. Fermi Fermic (Fennentutum) fermented; implying anaerobic decomposition. It designates the Histomors thatfeature a well developed Om horizon. Fibri Fibric (Fibra) fiber; designates the presence of awell developed Of horizon in the humus form profiles of Histomoders. Granulo Granulic (Granulum) grains, granules; designates the Mors that have a friable, moderately to strongly granular H horizon. Hemi Hemic (Hai) half, cf. Table 5; implying intermediate decomposition. It designates Hydromors and Leptomoders that feature a well developed F horizon. Histo Histic (Histon) woven fabric, tissue, cf. Table 5; implying the least and intermediate decomposition inthe semi-terrestrial environment.It designates Saprimulls that feature well a developed Of or Om horizon. Humi Humic Humus; implying the dominant presence of colloidal organic substances. It designates the terrestrial Mors that haveprominent a H horizon. Hydro Hydric (Hydor) water, cf. Table5; designates intergrade subgroups of all orders formed in a semi-terrestrial environment (hygric to hydric soilmoisture regime). TABLE 6. Fonnatiue Elements in Names OfSubgroups - Continued

Form ative element Adjective ConnotationAdjective element Formative

Ligno Lignic (Lignum) wood;designates Mors that have more than 50% decaying wood by volume withinthe humus form profile. Macro Macric (Makros) long; designatesthe zoogenous Ah horizonsof Vermimulls that have moderate to strong, medium to very coarsegranular structure. Micro Micric (ilfzkros) small;designates the Ah horizonsof Vermimulls that have moderate to strong, very fine to fine, granular structure. Minero Mineric (Mineralis); designatesXeromoders, Mormoders and Leptomoders which contain significantamounts of intermixed mineral particles, as indicated byFat , Hdl or Hdal horizons. M yco Mycic (Mukes) mushroom, mucor; designates Mors that have a horizon comprised almost entirelyof fungal mycelia. Orthi Orthic (Orthos) true; designates the subgroup thatis thought to typify the group. Para Paric (Para) beside; designates Saprimullsthat lack Oh1 or Ahg horizons. Residuo Residuic Residues; designates Mors in which an Hr horizon, characterized by the presence of fine plant (mainly root) residues, is dominant in the humus form profile. Rhizo Rhizic (Rhizo) root, cf. Table 5; designates Mullmoders that have rhizogenous Ah horizons. Sapri Sapric (Sapro) rotten, cf. Table 5; designates the subgroups of Hydromors, Histomors, Hydromoders, Histomoders,and Hydromulls, that feature a well developed Oh horizon. Neo Neoic (Neos) recent, young; implying initial humus formation. It designates Velomors that consist entirelyoflitter materials. Vermi Vermic (Vermis) worm, cf. Table 5; refers to a zoogenous Ah horizon in the humus form profileof Rhizomulls. Xero Xeric (Xeros) dry, cf. Table5; designates Rhizomulls that have formed in semiarid (to subhumid)climates in xeric (very xeric, xeric or subxeric) ecosystems.

TABLE 7. Adjectives in Names $Phases and Their Meaning'

Adjective Connotation

Acidic (Acidus) acid; designates humus forms that have high acidity. Aeric (Aer) air; designates humus forms that havelow a bulk density (high porosity). Albic (Albus) white; designates humus forms thatare underlain by a well developed Aehorizon. Charcic Charcoal; designates humus forms that possess significant amounts(>20% by volume) of charcoal. Clastic (Clastos) broken; designates humus forms that contain many(>20% by volume) coarse fragments. Compactic (Compactus) concentrated; designates humus forms that have a high bulk density(low porosity). Crustic (Crusta) hard, crisp;designates humus forms inwhich the upper horizonshave a dry, brittle and firm fabric. Dystrophic (Dys ...trophe) ill ...food; infertile; designates humus forms thatare nutrient deficient. Eutrophic (Eu... trqhe) well ... food; fertile; designatesthe humus forms thatare nutrient rich. Hygric (Hypos) wet; designates humus forms thatfeature subsurface water flow (seepage) within the humus form profile. Lignic (Lignum)wood, cf. Table6; designates humus forms possessing significant amounts(>50% by volume) of decaying wood. Ochric (Ochros) pale; designates humus forms that have an Ah horizon with a moistcolour value 2 3. Pachic (Pachys) thick; designates thick humus forms. Pellic (Pellos)dusky, dark coloured; designates humus forms that haveAh horizonan witha moist colour value < 3 and low chroma. ” 1 2 - TABLE 7. Adjectives in Names ofphases and Their Meaning’ - Continued Adjective Connotation

Rhodic (Rhodon) rose; designatesresiduic Mor humus forms that have a prominently reddishcoloured Hr horizon, usually derived from decayingwood materials. Ruptic (Ruptus) burst or broken; designates humus forms that have a broken horizon(s)in the control section. Spodic (Spodos) wood ash; designates humus forms that have well developedpodzolic horizons, high in organic matter content, directly underlying entorganichorizons. Tenuic (Tenuis) thin; designates thin humus forms. Terric (Tem’c) earth; an inorganic substance; designates humusforms that have a mineral horizon in the humus form profile. Turbic (Turbo) stir up; designates humus forms that have a truncatedprofile or have been markedly disrupted by physical processes. Ustic (Ustus) burnt; designates humus forms that have been recently affected by fireand feature a black, crusty (hard, brittle and tenacious) surface horizon.

‘These adjectives indicatenon-conformity .” in properties relative to the central concept of a formal taxon. The list is not exhaustive and will be edarged as required.

Description of Taxa 7a. Fq horizonpresent; Ah or Ahg horizons are absent or < 5 cm thick Key to Orders Mor 7b. Fa horizonpresent. Ah orAhg la. Well aerated, terrestrial humus forms that can be horizons are > 5 cm thick temporarilysaturated (xeric to hygricmoisture Moder regimes) 6b.Ectorganic horizons are very thinand 2a.Ectorganic horizons are predominant in the insignificant in the humus form profile humus form profile; both F and H horizons (generally< 2 cm thick). Well developed are each > 1 cm thick Ahg or Ah horizons 5 cm thick domi- 3a. F horizonsare predominantly myco- > nate the profile genous (Fq) Mull Mor 3b.F horizons are predominantly zoogenous (Fa) or zoogenous-mycogenous 1. Mor Order (Faq) The Mor order encompasses the least biologically ac- Moder tive humus forms of the three orders.is Itrelated to the 2b. Ectorganic horizons are very thin and insignif- Moder order in that terrestrial humus forms of both icant in the humus form profile; both F Hand orders often possess similar master horizon sequences. horizons are each < 1 cm thick; well devel- This has led to the grouping of these two major humus oped rhizogenous or zoogenous Ah horizons forms into a single humus formation, “mor”, in English are > 2 cm thick and American classifications. They are, however, differ- Mull entiated on the basis of fungi being dominant in the F 1 b. Poorly aerated, terrestrial to semi-terrestrial humus horizon of Mors, while soil fauna are dominant in the F forms influenced by prolonged or permanent sat- horizon of Moders. These genetic differences arereflec- uration (hygric to subhygric moisture regimes) tedin their respectivemicro- andmacromorphology 4a. 0 horizonscomprise > 50%of thicknessof (Babel 1975). organic horizons in the humus form profile The diagnostic F horizon (in Histomors, thediagnostic 5a. Of horizons are dominant in the humus horizon is Of),is often relatively thick, reflectingthe slow form profile decomposition processes taking place (Babel 1975). It is Mor composed primarily of partly decomposed, structurally 5b. Om horizons are dominantin the humus well preserved plant residues. These materials havea form profile matted, plate-like fabric, interwoven by fungal hyphae. Moder Decomposition of plant residuesis carried out primarily 5c. Oh or OhL horizons aredominant in by cellulose-decomposing fungi (Waksman 1938). Bac- the humus form profile teria play aminor rolebecause oftheir intolerance toacid Mull conditions typical of Mors. Acid-tolerant protozoa and 4b. 0 horizonscomprise< 50% ofthickness of soil fauna contribute to decomposition in a limited de- organic horizons in the humus form profile gree, the latterrestricted generally to mites, collembola, 6a. Ectorganic horizons generally exceeding and enchytraeids (Pritchett 1979). As a result, very few 2 cm thickness are significant in the faunaldroppings are present (Babel1975, Kubiena humus form profile 1953, Bernier 1968). In addition to litter materials, fine 13

roots and their residues constitutesignificant a portion of TABLE 8. Synopsis of Taxa of the Mor Order - Continued the plant residues of the F horizon. Often they form a dense network that permeates the remaining materials. Group Subgroup This feature is morecommonly associated with Mors than other humus forms(Babel 1975). 162. Residuohydromor 163. Hemihydromor Other organic horizons foundin Mors include LandH 164. Saprihydromor (in Histomors and some Hydromors these are Of, Om 1’7. Histomor 17 1. Orthihistomor and Oh). Due to small the degree of mineral grain mixing 172. Fermihistomor by mor-inhabiting fauna, €I horizons are generally free 173. Saprihistomor of mineral particles (Barratt 1964). However, significant 174. Hydrohistomor quantities of mineralparticles may be intermixed onsites where humus forms are subjected to repeated disturb- ance or to geomorphic processes of degradation or ag- Key to Groups of the Mor Order gradation. F horizons may be affectedin a similar way. la. Well aerated Mors thatcan be temporarilysatur- Mor humus forms generally consist entirely of ector- ated by water ganic horizons. However, “amphi” subgroups have an 2a. L horizons comprises > 80% of the thickness underlying mineral horizon enriched in humus in the of ectorganic horizons humus form profile (Bernier 1968, Babel 1975). This Velomor horizon contains humus materials infiltrated from the 2b. L, horizons comprises < 80% of the thickness ectorganic horizonsas solid particles in suspension. Both of ectorganic horizons its upper andlower boundaries are abrupt. The humusis 3a.Prolonged moisture deficiency in the not incorporatedby the actilon of soil fauna. growingseason (xeric moisture Chemical properties of Mors indicate that the humus regimes)’ materials are generallyvery acid to acid.High C/N values Xeromor and high cation exchangecapacities (ammonium acetate 3b.None or shortterm moisture deficien- method) are also typical. This suggests that they repre- cies sent a storage of nutrientswhich are slowly released and 4a. H horizon comprises < 30% of the made available to plants. Furthermore, the acid humus combined thickness of Fq and H materials contribute to translocation of inorganic con- horizons stituents from the upper to lower solum. Hemimor Mors develop primarily under boreal forests but also 4b. H horizon comprises > 305%of the elsewhere where climatic and/or edaphic conditions are combined thickness of Fq and H unfavourable for the deve.lopment of the more biologi- horizons cally active humus forms. 5a. H horizoncomprises > 30% The Mor order is subdivided into seven groups on the but < 70% of the combined basis of soil moisture regimes and the kind and arrange- thicknessof Fq and H ment of horizons (Table8, Figure 5). horizons Hemihumimor TABLE 8. Synopsis of Taxa of the Mor Order 5b. H horizoncomprises > 70% of the combined thickness of Fq and H horizons Group Subgroup Humimor 1 1. Velomor 1 1 1. Orthivelomor 1b. Poorly aerated Mors; prolonged or permanent sat- 1 12. Neovelomor 1 13. Amphivelomor uration by water(hygric to subhydric moisture regimes)’ 12. Xeromor 12 1. Orthixeromor 122. Lignoxeromor 123. Amphixeromor 13. Hemimor 13 I. Orthihemimor ‘Xeric (very xeric, xeric, subxeric) moistureregimes: inputs of 132. Mycohemimor water by precipitation are removed from the soil very rapidly in 133. Lignohemimor 134. Amphihemimor relation to other ecosystems. Soils are characterized by a low water storage capacity, which may be attributed to coarse tex- 14. Hemihumimor 14 1. Orthihemihumimor ture, shedding slopeposition (physiographic prominences, 142. Mycohemihumimor steep upperslopes) or very shallowdepth, either individuallyor 143. Lignohemihumimor 144. Granulohemihumimor in combination. 145. Residuohemihumimor ‘Hygric moisture regime: wateris removed from the soil slowly 146. Amphihemihumimor in relationto supply so that thesoil remains wetfor most of the 15. Humimor 15 1. Orthihumimor growing season. Permanent seepage is 30 to 60 cm below the 152. Mycohumimor soil surface. 153. Lignohumimor Subhydric moistureregime: wateris removed from soil so 154. Granulohumimor slowly that the water table remains ator near the surface for the 155. Residuohumimor greater part ofthe year. Permanent seepageis less than 30 cm 156. Amphihumimor below the surface, or there is a stagnant or fluctuating water 16. Hydromor 16 1. Orthihydromor table. 14

Velomor Xeromor Hemimor Hemihumimor

2o r

Humimor Hydromor Histomor

Figure 5. Characteristic humus form profiles of groups of the Mor order represented by orthi subgroups. 15

6a. Fq and/or H horizons comprise > 50% of the very fine and light coloured, making themdifficult to see thickness of organic horizons in the humus with the nakedeye. H horizons are either thin ormissing form profile; endorganic horizons arelacking entirely. All horizons are generally dry or desiccated for Hydromor much of the growing season, except forrelatively short 6b. 0 horizons comprise > 50% of the thickness durations following precipitation. When dry, the mor- of organic horizons in the humus form pro- phology is typically firmly consolidated and crust-like. file; the Of horizons comprise > 50% of the Xeromors aregenerally < 5 cm thick. combined thickness of these0 horizons Xeromors develop under prolonged moisture defici- Histomor encies and, as a result, decomposition of organic matter by biological agents tends to be suppressed. Ecosystems 11. Velomor which support Xeromors often experience a history of [n.n.; Kubiena 1953: Raw,Soil Humus (in part); Wilde repeated fire (both underburns and crown fires). This 1958: Velum (in part);Wilde 1966, 197 1: Velor (inpart)] repeated destruction of the humus impedes the build-up of organic horizons. In addition, production of litter is Characteristic humus form profile: L, (Fq)', (Ah) often sparse on thesesites as a result ofthe low ecosystem Velmors consist essentially of an accumulation of un- productivity. decomposed, usually coniferous forest litter.Specifically, Xeromors are found mostfrequently in ecosystems L horizons comprise>SO% of thethickness of ectorganic with extremely shallow or very coarse textured soils. horizons. They have single particle structure, loose con- Forest stands are generally open lacking or entirely. sistency and acerose character; theirthickness generally ranges from 1 to 10 cm. H and endorganic horizons are Key to subgroups usually absent. 3a 1. Xeromors that conform to the central concept of These humus forms are considered to represent the the group early stages of development, either primary or secon- Orthixeromor dary, of Mors, or eventually Moders. They show a low Xeromors that have 50% by volume of decaying degree of decomposition which, in forested ecosystems, 3a2. > wood in the humus formprofile is attributed to a high amount of litterfall and a climatic Lignoxeromor environmentof young dense canopied coniferous 3a3. Xeromors that have a continuous Ah horizon 2 stands. Decomposition increases following the opening > cm thick in the humus formprofile of the canopy which, in turn, renders more favourable Amphixeromor conditions for thesynthesis of humus materials. Velomors have been rela.tively little studied; thus, the Description of an Orthixeromor proposed subgroups are tentative. The following description of a humus form profile has the characteristics of the central concept of Xeromors. Key to subgroups The profile is located near Blue River in the Kamloops 2a 1. Velomors that have a thin Fq horizon, which com- Forest Region. The ecosystem is classified as the Picea prise < 20% of the ectorganic horizons (engelma'nnii) - Pinus (contorta)- Vaccinium (membran- Orthivelomor aceum) - Cladonia Association on a very shallow, loamy- 2a2. Velomors that consist entirelyof litter materials skeletal Orthic Humo-FerricPodzol formed on colluvial Neovelomor materials overlying granitic bedrock. 2a3. Velomors that have a1 continuous Ah horizon > 2

cm thick in the humus formprofile ~~ ~~~ ~~~~ ~~ ~ ~~ ~~~ ~~ ~~~ -~ Amphivelomor Horizon Depth Description (cm) ~ ~ ~~ ~ -~ ~--~ ~- ~~ 12. Xeromor L 3.5-2.5 Coniferousneedles and lichens; desiccated; Duchaufour 1960 [n.n.; Wilde 1958: Crust Mor; Wilde single-particle;loose; acerose: no roots; no 1966, 197 1: Crustar; Bernier 1968: Lichen0 Fibrimor; visible biota; abrupt, smooth boundary. Hartmann 1952: Waldtrocltentorf (in part)] Fq 2.5- I Desiccated; compact matted, firm; crusty; Characteristic humus form profile: L, Fq, (H), (Ah) plentiful, fine roots; common, fine, coarse Xeromors are Mors that are influenced by prolonged fragments;few, white mycelia: abrupt, moisture deficiencies during the growingseason result- smooth boundary. ing primarily fromclimatic and/or edaphiclimitations. Hd 1-0 Desiccated; very dary gray (IOYR 3/1 m); The humus formprofile typically has a thin L horizon plentiful, fine roots; common, fine, coarse derived primarily from coniferous needles and lichen fragments; abundant, white mycelia; abrupt, and bryophyte tissues. The underlying F horizon has a wavy boundary. ~ ~~~ ~ ~- ~ ~~ -~ - ~~- ~~~~~ characteristic compact matted structure, and firm tofri- able consistence (consistence varieswith moisture status). Fungal mycelia are usually present but in many cases are 13. Hemimor [n.n.; Romell and Heiberg 1931: Fibrous Duff; Hoover andLunt 1952: ThinMor, Imperfect Mor;Kubiena 'Parenthesis indicate features or attributes of less significance. 1953: Raw Humus; Wilde1958: Ligno-Mycelial Mor, 16

Lean Mor (in part); Wilde 1966, 1971,: Lentar (in part); Fq 6-2Moist; brown (7.5 YR 3/2 m); compact mat- Bernier1968: Fibrimor (in part); Hartmann 1952; ted; strongly tenacious; felty; plentiful, fine Waldtrockentorf (in part)] roots; common, pale yellow and white mycelia; abrupt, smooth boundary. Characteristic humus form profile: L, Fq, (H), (Ah) Hd 2-0 Moist; verydark gray (10 YR 3/1 m); mas- Hemimors areMors that have prominent Fq horizons sive; pliable; abundant, fine roots; common, relative to other organic horizons in the humus form fine charcoal; common, pale yellow mycelia; profile. Specifically, the H horizon comprises < 30% of abrupt, smooth boundary. the combinedthickness of the F andH horizons.’ ~~~ ”~~~~~ ~ ~~~~~~ The diagnostic Fq horizon is comprised of partially 14. Hemihumimor decomposed leaves and needles, as well as relatively sig- nificantquantities of fine rootresidues (Babel 1975). [n.n.;Hoover and Lunt 1952: Thick Mor (in part); Fungal hyphae are common.A non-compact to compact Kubiena 1953: Raw Humus (in part); Wilde 1966, 1971: matted structure is typical. Faunal droppings are rarely Lentar (in part); Bernier 1968: Humi-Fibrimor (in part); observable. H horizons arerelatively thin or even absent. Hartmann 1952: Waldtrockentorf (in part)] Hemimors commonly range from5 to 10 cm in thickness. Characteristic humus form profile: L, Fq, H, (Ah) The dominant Fq horizon implies nutrient conserva- Hemihumimors are Mors that have both Fq and H hori- tion resulting from slower rates of decomposition of lit- zons which show no particular dominancein the humus ter, and of synthesis of humus materials. It may also form profile. Specifically, the thickness of the H horizon reflect the maturity of the humus form. In ecosystems comprises between 30 and 70% of the combined thick- which have been disturbed by fire, there has been insuf- ness of F and H horizons. ficient time for the build-up of a well developed H The Fq horizon is comprised of partially decomposed horizon. litterand fine root residues. Both the Fq andthe L Hemimors are found in a wide range of ecosystems. horizons typically have a non-compactto compact matted They areparticularly prevalent in dry boreal climates or structure. Fungal mycelia are commonly present. They under young coniferous forests. are generally concentrated in the F horizon but some- Key to subgroups times permeate the entire humus profile.Roots are plentiful or abundant in all or part of the profile. Faunal 4a 1. Hemimors that conform to the central concept of droppings are rarely observable in the Fq horizon. Fine the group droppings may be observed under magnification in the Orthihemimor H horizon and occasionally constitute a significant por- 4a2. Hemimors that have a horizon comprised almost tion of the fabric (Babel1975). entirely of fungal mycelia (designated by ‘‘e ” The similarity of thickness of the Fq and H horizons suffix) implies rates of decomposition and humification of or- Mycohemimor ganic materials intermediate between that of Hemimors 4a3. Hemimors that have > 50% by volume of decaying and Humimors. The stages of development of humus wood in the humus form profile formation may also be reflected. Thus, Hemihumimors Lignohemimors may represent in somecases an intermediatesuccessional 4a4. Hemimors that have continuous Ah horizons > 2 stage advancing towards a Humimor. cm thick in the humus form profile Hemihumimor is a modified consolidation of Bernier’s Amphihemimor Fibri-Humimorand Humi-Fibrimor groups. His two taxarepresenting a transitionbetween Hemimors Description of an Orthihemimor (Fibrimors) and Humimors were consolidated into one taxonon the basis of low correlation with chemical The following description of a humus form profile hasproperties. the characteristics of the central concept of Hemimors. The profile is located near Clearwater in the Kamloops Key to subgroups Forest Region. The ecosystem is classified as the Abies (lasiocarpa) & (Picea (engelmannii)) - Rhododendron (al- 5al. Hemihumimors that conform to the central con- biflorum) - Valeriana (sitchensis) Association on a loamy cept of the group Orthic Humo-Ferric Podzol formed on morainal mate- Orthihemihumimor rials overlying phyllite bedrock. 5a2. Hemihumimors that have a horizon comprised almost entirely of fungal mycelia (designated by ‘‘ e ”

~~ ~~ ~ ~- ~ ~ ~~~~ ~~ ~ ~ ~~~. suffix) Horizon Depth Description Depth Horizon Mycohemihumimor (cm) ~~~~ ~~ ~~~~ 5a3. Hemimors that have > 50% by volume of decaying wood in the humus form profile L 7-6 Coniferousneedles; dry; weak,non-compact Lignohemihumimor matted; loose; acerose; no roots; no visible 5a4. Hemimors that have friable H horizonswith a mod- biota; abrupt, smooth boundary. erate to strong granular structure Granulohemihumimor

‘The value of‘ 30% is a modification of Bernier’s “ < 10%” crite- 5a5. Hemimors that have Hr > Hd horizons rion for Fibrimor. Residuohemihumimor 17

5a6. Hemimors that have continuous Ah horizons > 2 under climax coniferous forestsin humid and perhumid, cm thick in the humus form profile temperate, mesothermal and subalpine to borealclimates Amphihemihumimor where humus formationis not influenced by frequently occurring fires. Description of an Orthihemihumimor The following descriptionof ahumus form profilehas Key to subgroup thecharacteristics of the central concept of Hemi- 5b 1. Humimors which conform to the central conceptof humimors. The profileis located near Clearwater in the the group Kamloops Forest Region. The ecosystem is classified as Orthihumimor the Tsuga (heterophylla)- Thuja (plicata) - Hylocomium 5b2. Humimors which have a horizon comprised almost

(splendens) - Pleurozium(schreberi) Association ona entirely of fungal mycelia (designated by “ ,g ” loamy-skeletal Brunisolic Gray Luvisol formed on mor- suffix) ainal materials over granitic bedrock. Mycohumimor 5b3. Humimors which have 50%’by volume of decay- ~ ~ ~ ~-~- ~~ ~ ~~ -~ -~~- ~- > HorizonDepth Description ing wood within the humus form profile (cm) Lignohumimor ~~ ~~ - __ -~- ~-~ ~ 5b4. Humimors which have friable H horizons with a L 5-4 Needlesandfeather mosses; dry; moderate, moderate to strong granular structure compact matted; loose; acerose; few, very Granulohumimor fine roots; no visible biota; abrupt, smooth 5b5. Humimors which have Hr > Hd horizons boundary. Residuohumimor 5b6. Humimors which have continuous Ah horizons >2 Fq 4-2 Moist;dark brown (7.5 YR 3/2 m); moderate, compact matted; moderately tenacious; cm thickin the humus form profile fibrous; plentiful, very fine roots; common, Amphihumimor very fine, whitemycelia; abrupt, smooth boundary. Description of an Orthihumimor Hd 2-0 Moist;dark brown (7.5 YR 3/2 m); moder- The following description ofa humus form profilehas ate, fine, granular;pliable; plentiful, fine the characteristics of the central concept of the Humi- roots;common, fine decaying woodand mors. The profileis located in the Koprino River water- charcoal; few,very fine, white mycelia; shed in the Vancouver Forest Region. The ecosystem is clear, wavy boundary. classified as the Tsuga (heterophylla)- Abies (amabilis) - ~~ ~ ~~ ~~~ ~ ~ ~ ~~~ ~~~ [Picea(sitchensis)] - Vaccinium(alaskaense 8c parvifolium) - Rhytidiadelphus(loreus) Association on a 15. Humimor loamy-skeletal Orthic Ferro-Humic Podzol formed on colluvial veneer over conglomerate bedrock. Bernier 1968 [n.n.; Romell and Heiberg 1931:Greasy Duff; Hoover and Lunt1952: Thick Mor (in part); Hart- ~~~~ ~ ~~ ~~ ~ ~- ~ mann 1952: AnaeroberWalldnasstorf (in part)] DescriptionHorizon Depth (cm) Characteristic humus form1 profile: L, Fq, H, (Ah) ~~~ ~~ ~~~~ ~. ~ -~ ~~~~ ~~ - ~~~~ Humimors are Mors thlat have more prominent H L 18- 17 Coniferousneedles; moist; non-compact horizons than F horizons. Specifically, H horizons com- matted;loose; acerose; no visible biota; prise over 70% of the combined thickness of F and H abrupt wavy boundary. horizons. Fq 17-15Moist; dark reddishbrown (7.5 YR 2/2 m); The F horizon typically :shows a non-compact to com- compact-matted; moderately tenacious; pact matted structure. The diagnostic H horizon is gen- fibrous; plentiful fine to medium roots; few erally massive with a greasy character when wet, or fri- larvae;common yellow mycelia; abrupt, able with a fine blocky or granular structure whenmoist. wavy boundary. Roots are common to abundant in all or part of the Hd 15-0 Moist; verydark gray (10 YR 31 1 m); mas- humus form profile. Fung;al hyphae are always present sive, pliable; greasy; plentiful roots of all and are usually concentrated in the F horizon, although sizes; abrupt, wavy boundary they may occur throughout the profile. Faunal drop- .~~~~ ~~~ ~ ~ ~ ~~ pings are rarely observablein the F horizon. Tiny spherical or cylindrical droppings may beobserved under 16. Hydsomor magnification in the H horizon and occasionally consti- Lafond1952, Duchaufour 1960 [n.n.;Mader 1953: tute a significant portion of the fabric(Babel 1975). Swamp Mor; Wilde 1958: Sog Mor; Wilde 1966, 1971: The humus form profile commonly ranges from 5 to Uliginor; Hartmann 1952: Anaerober Waldnasstorf (in cm in thickness, with exceptional cases near to, or 20 part)] exceeding 40 cm. The well developed H horizons of Humimorsindicate Characteristic humus form profile:,L, Fq, H, [O (Of, Om an intensive rate ofsynthesis and accumulation of humus or Oh)] materials in the humus form. They may also reflect the Hydromors are poorly aerated Mors which are under maturity of the humus form. They arecommonly found the influence of prolonged but not permanent saturation. As a result,0 organic horizons may be developed in vironment, decomposition of organic material is slow, the lower part ofthe humusprofile; however, Fq and H resulting in a build-up of ectorganic horizons. horizons comprise >50% of the thicknessof organic Hydromors are distributed in boreal, cool mesother- horizons. Theassociated soils are eitherGleysols, gleyed mal andtemperate climatesin physiographic and/or subgroups of other mineral soil orders with well expres- edaphicenvironments where prolonged saturation of sed gleying within 50 cm of the mineral surface,or occa- the soils is common. sionally organic soil. Hydromors are generally <40 cm thickbut may occasionallyexceed this in exceptional Key to subgroups (Figure 6) cases. Endorganic horizons arelacking. Hydromors rep- 6al.Hydromors inwhich theHd horizons comprise resent a transition between terrestrial and semi-terres- >70% ofthe combined thickness of F andH trialhumus forms. They weredesignated as hydro- horizons morphichumus forms by Wilde (1958)and Bernier Orthihydromor ( 1968). 6a2.Hydromors in which theHr horizonscomprise Hydromors develop under the direct influencefluc- of 70%' of the combined thickness of F and H tuating, stagnant orslowly moving water which is gener- > horizons ally between 30 and 60 cm below the soil surface. They typically have a thin L horizon (or S layer) on the surface, Residuohydromor 6a3.Hydromors inwhich the H horizonscomprise overlying F and H horizons occupying the upper partof of the combined thickness of F and H the humus form profile. The F horizon is matted and < 70% horizons derived primarily from moss tissues, coniferous litter or Hemihydromor residues of hydrophytic vegetation. The H horizons us- 6a4. Hydromors in which 0 horizons comprise between ually have a very weak structure and greasy character. 25 and 50% of the total thickness of' organic hori- The lower part of the humus formprofile may comprise zons in the controlsection any combination of Of, Om and Oh horizons. These Saprihydromor horizons have a massive structure and mushy character. A characteristic feature of Hydromors is that their 0 horizonshave fewer living roots than their- F and H Description of an Orthihydromor horizons. The following description of a humus form profilehas Hydromors developin part underhydrolysis and peri- the characteristics of the central concept of the Hydro- odic anaerobic fermentation (Wilde 1958). Fungal and mor Group. Theprofile is located in the Koprino River minormicrofaunal (microarthropods) activities often watershed in the Vancouver Forest Region. take place, however, this is generallyrestricted to the The ecosystem is classified asthe Tsuga (heterophylla) upper horizons which are not subjected to prolonged - Abies(amabilis) - [Picea(sitchensis)] - Vaccinium saturation. Because of this unfavourableedaphic en- (alaskaense & parvifolium) - Rhytidiadelphus(loreus)

Orthihydromor Residuohydromor Hemihydromor Saprihydromor

L, L, I I L, A I \ I

30 ' Figure 6. Characteristic humus form profiles of subgroups of the Hydromor group. 19

Association ona loamy-skeletal Gleyed Ferro-Humic oped in theupper portion of theprofile. Histomors Podzol formed on a morainal blanket over conglomerategenerally exceed 40 cm in thickness. The associated soils bedrock. are most frequently organic butmay occasionally include Gleysols. ~~~ ~ ~~ ~ ~~~ ~~ ~ Description Histomors develop under conditions of prolongedsat- uration due to a stagnant water table, generally located - ~~ ~~ ~~ ~~~ . ~ within 30 cm of the ground surface. They typically pos- L 36-34 Feathermosses and needles; moist:non- sess a layer ofliving mosses(S) mixed with litter materials compact matted; loose; acerose; no visible from vascular plants and typically overlie a thick Of hori- biota; abrupt, smooth boundary. zon, which is derived primarily from bryophytes, particularly Sphagnum mosses, and is always wet and fibrous. Fq 34-29 Wet; dark reddish brown (7.5 YR 2/2 m); compact-matted; moderately tenacious; Occasionally Om or Ohhorizons may occur towards the fibrous; plentiful fine to coarse roots; few to lower portion of the controlsection. common white mycelia; few, medium,clus- Histomors, resulting from a combinationof low temp- tereddecaying wood fragments; abrupt, eratures, aeration and nutrient content associated with wavy boundary. the excessive water supply, are representativeof the most inert humus forms. They are distributed in subarctic, Hd 29-0 Hd Wet; dark reddish brown (5 YR 2.5/2 m); boreal, subalpine boreal and cool temperate (marginal) massive;pliable; greasy; common fine to climates in physiographic and/or edaphic environments mediumroots; no visible biota: common, where a high and permanent water table in the soils is medium, random decaying wood fragments; common. Under a perhumid climate,Histomors may abrupt, wavy boundary. ~ ~~ ~ ~~ ~~ ~~ ~~ ~ ~~ .~ occur in organic soils which originated in upland depres- sions and have subsequently spread over surrounding terrain (“paludification”, Heinselman 1963). Histomors generally occur in ecosystems which are sparsely or non- [n.n.; Kubiena 1953: High .Moor; Wilde 1958: Moss Mor forested. (in part); Duchaufour 1960: Peat; Bernier 1968: Fibric Peaty Mor; Hartmann 1952: Abiologischer Sphagnum- Key to subgroups (Figure 7) Waldnasstorf] 6bl. Histomors inwhich the Of horizonscomprise Characteristic humus form. profile: S or L, F, H; Of (Om, >70’jZ of the total thickness of O horizons in the Oh) humus form profile Histomors are verypoorly aerated Mors which are Orthihistomor under the influence of more or less permanent satura- 6b2. Histomors in which the Of horizons comprise be- tion by dystrophicwaters. They are dominated by 0 tween 50 and 70% of the 0 horizons in the humus horizons, particularly Of, which comprise >50% of the form profile and are underlain by predominantly humus form profile. L, F a.nd H horizons may be devel- Om horizons Fermihistomor

Orthihistomor FermihistomorOrthihistomor HydrohistomorSaprihistomor

-Om

Fzgure 7. Characteristic humus form profiles of subgroups of the Histomor group. 20

6b3. Histomors in which Of horizons comprise between numbers of bacteria, actinomycetes, and protozoa contri- 50 and 70% of the 0 horizons in the humus form bute to the decompositionprocess. profileand are underlain by predominantly Oh In the Mormoder group, theF horizon takes on char- horizons acteristics of both Fa and Fq horizons (thus designatedas Saprihistomor Faq). Fungal mycelia may be fairly common and plant 6b4. Histomors in which L, F, H horizons comprise be- residues may appear somewhat matted, however, many tween 25 and 50% of the total thickness of organic small insect droppings can still be observed. horizons in the humus form profile Hd horizons are found in most Moder humus forms. Hydrohistomor They are often permeatedby loose, incoherent mineral particles(Kubiena 1953, Bernier 1968, Babel 1975). Description of an Orthihistomor Such horizons are designated by the lowercasesuffix The following description of a humus form profile has“ L ”. However, this feature is not considered diagnostic the characteristics of the central concept of Histomors. of Moders since Mor humus forms may possess similar The profile is located adjacent to the North Thompson horizons. Babel’s (1975)observations of humus form River in the Kamloops Forest Region. The ecosystem is micromorphologyindicated that H horizonshave no classified as the Picea (mariana) - Ledum (groenlandi- clear,distinguishing features whichwould indicate cum) - Sphagnum Association on a TypicMesisol formed& whether they are fromMors or Moders. on an organicblanket. Moder humus forms may be comprised of ectorganic horizons only or ectorganic horizons underlain by end- ~~ organichorizons. This horizon contains fine humus Horizon Description Depth materials whichhave infiltrated into themineral soil. or Layer (cm) Although organic matter may be transported into the S 4-0 A layer of living Sphagnum mosses. upper portion ofthis horizon by soil fauna, this will only occur over verya short distance(Babel 1975).The upper Wet; light brown (7.5 YR 6/4 w); erect; Of I 0-27 boundary of theAh horizon is generally gradual,in con- abundant, moderatelytenacious; mushy; trast to the abrupttransition typical of similar situations fine roots; ants and spiders common; gradual, in the Mor humus forms. smooth rubbed fibre approx.90%. boundary; In comparison toMors, in general, chemical properties 0f2 27-40+ Wet; reddishbrown (5 YR 5/4 w); erect; of Moders showlower acidity, totalcarbon, carbon: nitro- moderately tenacious; mushy; abundant,fine gen ratio, and cation exchangecapacity, and higher total roots; no visible biota; clear, smooth, bound- nitrogen and base saturation. This suggests that Moders ary: rubbed fibre approx. 80%. provide moreavailable nutrients than Mors. ~~ - Modersdevelop under the influence of semiarid, temperate and mesothermalclimates, particularlyunder Moder Order forest stands which yield easily decomposable litter, gen- 2. erally from deciduous overstory or understory vegeta- Humus forms of the Moder order mav be considered tion. Mormoder and Mullmoder, the intergrade groups transitional between Mors and Mulls. They aresimilar to of the Moder order,may be found under3ess favourable Mors in thatthey generally represent an accumulation of and more favourable “hydrothermal”’ conditions, res- partially to well humified organic materials resting on pectively. the mineral soil. On the other hand,they are similar to TheModer order is subdividedinto seven groups Mulls in that they are zoologically active (Kubiena 1953, based on soil moisture regime, and kind and arrange- Wilde 1966, Bernier 1968, Babel 1975). Because Moders ment of horizons (Table9, Figure 8). encompass both of these characteristics,they represent a kind of humus formationdistinctly different from either TABLE 9. Synopsis ojTaxa of the Moder Order Mors or Mulls. As Wilde put it, Moders (termed “Leptor” ___ -~ inhis classification) are“the most biologically active Group Subgroup forms of ectohumus”. 2 1. Velomoder 2 I 1. Orthivelomoder Terrestrial Moders are characterized by the diagnostic 2 12. Minerovelomoder Fa horizon. This horizonis comprised primarily of partly 2 13. Amphivelomoder decomposed plant residueswhich have been fragmented 22. Xeromoder 22 1. Orthixeromoder or comminuted by soil fauna and which are loosely ar- 222. Mineroxeromoder ranged, not mattedas in the Fq horizons (Kubiena 1953, 223. Amphixeromoder Bernier 1968). Occasionally an abundance of fine roots may create a matted appearance (Armson1977). In addi- 23. Mormoder 23 1. Orthimormoder 232. Humimormoder tion to the loose consistency, a characteristic feature of 233. Mineromormoder the Fa horizon is the numerous soil fauna droppings 234. Amphimormoder which are readily observable under magnification. These droppings originate frommany types offauna, including 24. Leptomoder 24 1. Orthileptomoder 242. Hemileptomoder centipedes,millipedes, collembola,mites, isopods and various insect larvae. Fragmentationof plant residuesby soil fauna promote an increased rate of decomposition. ‘Hydrothermal - combination of temperature and moisture Although fungi still play an important role, increasing regimes (Kononova 196 I). 21

Vdomoder Xeromoder Mormoder Leptomoder

40 Mullmoder Hydromoder Histomoder

L I 9 10 a

50 22

TABLE 9. Synopsis of Taxa of the Moder Order- Continued 6b. (Of), Om(and Oh) horizons comprise > 50% of the thicknessof organichorizons in the humus form profile. The 243. Mineroleptomoder Om horizons comprise>50% 244. Amphileptomoder of the combined thickness of 25 1. Orthimullrnoder these 0 horizons 252. Vermimullmoder Histomoder 253. Khizornullmoder 26. Hydromoder 26 1. Orthihydromoder 262. Ectohydromoder 263. Saprihydromoder 2 1. Velomoder '17. Histomoder 27 1. Orthihistomoder [n.n; Kubiena 1953: Raw Soil Humus (in part); Wilde 272. Fibrihistomoder 1958: Velum (inpart); Wilde 1966, 197 1 : Velor (inpart)] 253. Saprihistornoder 274. Hydrohistomoder Characteristic humus form profile: L, (Fa), (Ah) Velomoders consist essentially of an accumulation of litter materials, usually coniferous foliage, underlain by very thin Fa horizons. Specifically, L horizons comprise Key to Groups of the Moder Order > 80% of the thickness of the ectorganic horizons. They havesingle particle structure, looseconsistency and acerose character. They are generally under 10 cm in 1 a. Well aerated Moders; can be temporarily saturated thickness. by water These humus forms are considered to represent the 2a. I, horizons comprise > 80% of the total thick- early stages of development, either primary or secon- ness of ectorganic horizons.Thin Fa horizons dary, of: Moders. They show a lack of humus materials, are always pr-esent which, in forestedecosystems, may be attributed toa high Velomoder amount oflitterfall andthe climatic environment in 2b. I, horizons comprise < 80% of the total thick- young, dense coniferous stands. As these stands mature ness of ectorganic horizons. Fa or Faq hori- and openingsin the canopy occur, the rate ofdecomposi- zons always present tion is increased with F horizons becoming more promi- Ya. Prolongedmoisture deficiency during nent andH horizons appearing. Velomodersmay also be thegrowing season (xeric moisture associatedwith some climax stands which experience regimes) periodic destruction of humus horizons through under- Xeromoder burning. 3b.None orshort term moisture deficiencies la. Fa horizons present in humus form Key to subgroups profile 5a. Total thickness of endorganic 2a 1. Velomoders that conformto the central conceptof horizons > total thickness of the group ectorganichorizons (exclud- Orthivelomoder ing L) 2a2. Velomoders which contain significant amounts of Mullmoder ' mineralparticles intermixed throughout the 5b. Total thickness of endorganic humus form profile, as indicated by LL and Fa1 horizons < total thickness of horizons ectorganichorizons (exclud- Minerovelomoder ing L) Leptomoder 2a3. Velomoders that have a continuousAh horizon > 2 4b.Faq horizonspresent in humus cm thick in behumus form profile form profile; Fa horizons minor or Amphivelomoder absent Mormoder Ib. Poorly aeratedModers, prolonged or permanent Description of an Orthivelomoder saturation by water (hygric to subhygric moisture The following description of a humus form profile has regimes) the characteristics of the central conceptof Velomoders. 6a. F horizons and/or H horizons The profile is located near Campbell Lake in the Van- comprise > 505%of the thick- couver Forest Region. The ecosystem is classified as the nessof organichorizons in immature variant of the Thuja (plicata) - Pseudotsuga the humus form profile. Ah (menziesii) - Mahonia (nervosa)- Polystichum (munitum) or Ahg horizons > 5 cm thick Association on a loamy OrthicHumo-Ferric Podzol present formed on morainal materials overlying volcanic bed- Hydromoder rock. 23

~~~ Key to subgroups Description

~ ~~~ ~~~~ ~ ~~~~ ~~~ ~~ 3a 1. Xeromoders that conformto the central concept of Douglas-firneedles; moist; single particle the group (non-compact matted in lower portion); Orthixeromoder loose; acerose; no roots; no visible biota; 3a2. Xeromoders which contain significant amounts of abrupt, smooth boundary. mineralparticles intermixed throughout the Fa 0.5-0 Moist; weak, non-compact matted; loose to humus profile, as indicated by Far and Hr hor- friable; acerose; no roots;common, fine izons droppings, common insects (wood-lice, Mineroxeromoder nematode!;, centipedes), mycelialacking; ' 3aY. Xeromoders thathave a continuousAh horizon > 2 abrupt, smooth boundary. cm thick in the humus form profile (Hd) discon- Incipient horizon forming in small pockets. Amphixeromoder tinuous ~~~~~ Description ofan Orthixeromoder The following descriptionofa humus formprofile has 22. Xeromoder the characteristics of the central concept of Xeromoders. (n.n.; Duchaufour 1960: Xeromorphic Moder) The profile is located near Kamloops in the Kamloops Characteristic humus form profile: L, Fa, (H), (Ah) Forest Region. The ecosystem is classified as the Pinus (ponderosa) - Agropyron(spicatum) Association ona Xeromoders are well aerated Moders that are influ- sandy OrthicEutric Brunisol formed onfluvial materials enced by prolongedmoisture deficiencies duringthe over volcanic bedrock. growing season, resulting]primarily from climatic and/or edaphic limitations. As limited data is available, the fol- ~ ~~ ~~~~~ Horizon Depth Description Depth Horizon lowing characteristics of Xeromoders are tentative and (cm) subject to further study. ~~~ ~ ~~~ ~~ ~~~~ The humus form profile typically has thin L horizons L 3-2 Ponderosapineneedles; dry; singleparticle; derived primarily from coniferous needles, lichen and acerose;loose; no roots; novisible biota; bryophyte tissues and residues of herbaceous(grami- abrupt, smooth boundary. noid) plants. The underlying Fa horizon is comprised of a loose to weakly consolidated accumulation of partially Fa 2-0.2 Dry; weaknon-compact matted; loose; acer- decomposed plant residues, not matted as in Xeromors. ose; very few, fine roots;few, mediumdrop- Fungal mycelia are of minor significance. If present, they pings, abundant, white mite eggs, and micro- are generally very fine and scattered in isolated pockets. centipedes commonly observed; few, small Bryophyte rhizoids may b'e abundant, creating a fibrous clusters of very fine, felty mycelia; abrupt, character. UnlikeLeptomoders, faunal droppings are smooth boundary. notreadily observable in the F horizon. Becauseof Hdl 0.2-0 Dry; weak, fine granular; gritty; very friable; moisturelimitations, the fauna which are most active few fine roots; common quartz grains; no includemites, collembola andother tiny microfauna. visible biota; clear, smooth boundary. ~~ ~~ ~ ~~ ~ ~~ These species generally produce very small (less than approx. 0.1 mm) droppings which are difficult to observe (Hodgson 1978). Scattereddroppings of larger fauna may occasionally be found. 23. Mormoder H horizonsare generally thin or lacking entirely. [n.n.; Kubiena 1953: Coarse Moder; Wilde 1966: Velor Where present,they are often permeatedwith loose min- (in part); Bernier 1968: Raw Moder;Hartmann 1952: eral grains. All horizons are typically dry or desiccated Eumycetischer Moder (Pilzmoder)] during muchof the growing season, except forrelatively short durationsfollowing ]precipitation. Characteristic humus form profile: L, Faq, H, (Ah) Decomposition and humificationof organic matter Mormoders arewell aerated Moders which are transi- tendto be suppressed in Xeromoders as a result of tional to Mor humus forms. They are characterized by moisture deficiencies. F horizons, therefore, tend to be the Faq horizons present in the humus form profile. This dominant in many profiles. Biological activity is greatest Faq horizon generally has characteristics of both Mors during periods of favourable hydrothermal conditions, and Moders in that both soil animals and fungi may be usually in the early growing season.Ecosystems support- active. Some of thefollowing characteristics are tentative ing Xeromoders may experience a history of repeated due toa lack of data. underburns. This repeated destructionof the humus The Faq horizon is comprised of partially decomposed impedes the build up of organic horizons, particularly needles and leaves arranged into a weak to moderate, the H. In addition, litter production is often sparse on compact or non-compact matted structure. The mate- these sites resulting fromlow ecosystem productivity. rials are seldom as strongly matted as in true Mors. Fun- Xeromoders are frequlently found inecosystems in gal mycelia are generally present but are seldom abund- semiaridclimates or on edaphically dry sites in tem- ant. Insect droppings are observable in most cases, al- perate, subhumid and humidclimates. Forest stands are though they are usually smaller and less common than in generally open orlacking entirely. Leptomoders. 24

H horizons are generally thin, but they occasionally 24. Leptomoder comprise > 50% of the profile (excludingL). Their struc- [n.n.;Hoover and Lunt 1952:Duff Mull (inpart); ture is fine to medium granular andmay contain a signif- Kubiena 1953: Moder; Wilde 1958: Duff Mull (in part); icant proportion of insect droppings. The H is often Wilde 1966,1971: Leptor; Bernier 1968: TypicalModer; permeated by loose mineral grains. Hartmann 1952: Arthropodenmoder (Insektenmoder)]. Mormoders aremorphologically similar to Hemimors or Hemihumimors. They are most frequently under 10 Characteristic humus form profile: L, Fa, H, (Ah) cm in total thickness. The dominant Faq horizon indi- Leptomoders are well aerated Moders which have a cates that the rates of decomposition are somewhat less distinct Fa horizon underlain by an H horizon that may than the zoologically more active Leptomoders. In com- or may not contain intermixed mineral grains. Specifi- parisonto sites commonlysupporting Leptomoders, cally, Leptomoders have distinct Hdl or Hd horizons Mormoders tend to develop on drier habitats in eco- overlain by Fa horizons. The total thickness of ectorganic systems yielding less easily decomposed litter. They are horizons (excluding L horizons) exceeds the total thick- frequentlyfound under coniferous ecosystemsinflu- ness of endorganic horizons,if present. enced by subhumid to humid, temperateto mesothermal The Fa horizon is comprised of partially decomposed climates. plantresidues whichhave beencomminuted by soil fauna. Thesematerials are typically arranged into loosea Key to subgroups to weak, non-compact matted structure. Occasionally a 4bI. Mormoders that conformto the central conceptof matted appearanceprevails due to an abundanceof fine the group roots. Many faunaldroppings are readilyobservable, Orthimormoder particularlyunder magnification. Fungal mycelia are 4b2. Mormoders inwhich the Faq horizonscomprise either absent or are present in minor amounts. The Fa < 50% of the combined thickness of the F and H horizons are typically thin, seldom exceeding 3 cm. H horizons horizons are better developed than Fa the horizons. They Humimormoder are often permeated by loose mineral grains and may 4b3. Mormoders which contain significant amounts of contain a significant proportion of droppings,occasion- mineralparticles intermixed throughout the ally constituting the entire fabric. The ectorganic hori- humusprofile, as indicated by Faq L and H L zons commonly range from to5 15 cm in total thickness. horizons Leptomoders represent humus forms that containac- Mineromormoder tive populations of arthropods and other fauna, which 4b4. Mormoders that have a continuousAh horizon > 2 promote“far-going but not complete humification” cm thick in the humus form profile (Kubiena 1953) of organicresidues. They develop in Amphimormoder response to favourable conditionsof moisture, temperature and aeration, commonly under stands which yield Description of an Orthimormoder easily decomposable litter (i.e. deciduous overstory and The following description of a humus form profile hasunderstory species). the characteristics of the central concept of Mormoders. The profile is located near Sayward in the Vancouver Key to subgroups Forest Region. The ecosystem is classified as the Thuja 5b 1. Leptomoders which conform to the central concept (plicata) - Pseudotsuga(menziesii) - Polystichum (munitum) - Mahonia(nervosa) on a loamy Orthic of the group Orthileptomoder Humo-Ferric Podzol formed on colluvial materials overlying volcanic bedrock. 5b2. Leptomoders in which the thickness of the Fa is 2 the H horizon

~~~ ~~ Hemileptomoder Horizon Depth Description 5b3. Leptomoders which contain significant amounts of

(cm)~ ~~ ~~~~~ ~ ~ ~~~~ ~ mineralparticles intermixed throughout the humus form profile, as indicated by Far and H L Douglas-fir needles; moist; single particle to L s -4 horizons non-compact matted in lower portion; loose; Mineroleptomoder acerose; no roots; no visible biota; abrupt, 5b4. Leptomoders thathave continuous Ah horizons > 2 smooth boundary. cm thick in the humus form profile Faq 4- I .S Moist; weak, compact matted; friable to very Amphileptomoder weakly tenacious; slightly felty; few, fine roots; common, coarse white “flecks” and Description ofan Orthileptomoder common fine, felty, brown mycelia, clusters ofmedium and coarse droppings, few to The following description of a humus form profilehas commoninsects (nematodes, woodlice, the characteristics of the central concept of Lepto- spiders); abrupt, smooth boundary. moders. The profileis located near Sayward in the Van- couver Forest Region. The ecosystem is classified as the Hd 1 .5-0 Moist; weak, medium, granular; very friable; Thuja (plicata) - Pseudotsuga (menziesii) - Polystichum greasy; common, fine roots; common, coarse (munitum) - Tiarella (trifoliata) Association on a loamy white “flecks” of mycelia in upper portion: OrthicHumo-Ferric Podzol formedon amorainal abrupt, wavy boundary. ~~ ~~~~~~~ ~ ~~~ ~ ~ ~~~~~~~ ~ blanket. 25

~~~ ~~~ ~~~ ~~ ____~ to HorizonDepth Description Key subgroups (cm> 3b 1. Mullmoders which conform to the central concept ~~ ~~~ ~~~ __~~~~~~~ of the group L 6.5-6.0 Douglas-firneedles and Polystichum foliage; Orthimullmoder moist;single particle; loose; acerose; no 3b2. Mullmoders in which earthworms are active in the roots; few clusters of fine and medium drop- humus formprofile pings; abrupt, smooth boundary. Vermimullmoder Fa 6.0-4.5 Moist;non-compact matted; loose; (soft) 3b3. Mullmoders that have a dense network of finely acerose; no roots; common, fine and medium divided roots. The Ah horizon is rhizogenous droppings in clusters, few, aggregated worm Rhizomullmoder casts,common insects (woodlice, centipedes,spiders, nematodes, large larvae); Description of an Orthimullmoder few,scattered clusters of very fine, felty The following description ofa humus form profile has mycelia; abrupt, smooth boundary. the characteristics of the central conceptof Mullmoders. Hd 4.5-1 Moist;fine granular; friable; greasy; com- The profile is located near Campbell River in the Van- mon, fine roots; few, medium, clusters of couver Forest Region. The ecosystem is classified as the charcoal; ;abundant, medium droppings; my- Thuja(plicata) and Abies (grandis) - Pseudotsuga celia lacking; abrupt,smooth boundary. (menziesii) - Polystichum (munitum)- Tiarella (trifoliata) on a sandy Gleyed Dystric Brunisol formed on fluvial Hdr 1-0 Moist;finegranular; friable; gritty; com- materials. mon,fine roots; common, medium droppings;mycelia lacking; abrupt, wavy boundary ~ ~ ~~ ~ -~-~~

Lv 5.0-4.5 Coniferousneedles, herbaceous and decidu- 25. Mullmoder ousleaves; moist; single particle; loose; leafy; noroots; abundant springtails,few [n.n.Kubiena 1953: Mull-like Moder(in part); Wilde fine droppings; abrupt,smooth boundary. 1958:Microbiotic Mull (in part); Wilde 1966, 197 1 : Parvital(in part);Bernier 1968: Mull-like Moder (in Fa 4.5-4.0 Moist; single particle; loose; no roots; part); Hartmann1952: Salurer Waldmull] abundantspringtails; common millipedes, abundant aggregates of droppings; abrupt, Characteristic humus for profile: (L), (Fa), H, Ah smooth boundary. Mullmoders are well-aerated Moderswhich are transi- Hdac 4.0-0 Moist;moderate, very fine, granular; very tional to Mull humus forms. They differ fromMulls in friable; gritty; common,fine roots; common that they haveH horizons greater than1 cm thick. Speci- millipedes; abundant droppings dominating fically, Mullmoders have Ah horizons greater than cm 2 the fabric; clear, wavy boundary. thick, overlain byFa and H horizons whose combined thickness is less than thetotal thicknessofthe endorganic Ah 0-6 Moist;moderate, medium, granular; friable; horizons. siltloam; abundant, medium roots; few Hd horizons containing significant amounts of inter- earthworms and casts; clear, smooth bound- mixed mineral grains are usually present. Soil fauna, ~- ~ ~~~ a!?- ~~~ ~ ~~ ~ ~- includingarthropods, nematodes, and occasionally earthworms, are generally active in these humus forms, contributing to the intermixingof mineral grains. Where 26. Hydromoder this activityresults in Hd horizonscontaining clearly Duchaufour 1960 [n.n.; WiIde 1966, 197 1: Uliginorm (in identifiable insect droppings,the designation Hda or paw1 Hdar maybe used. The fabric of the H horizons is typically very fine or medium granular with a greasy or Cliaracteristic humus form profile: L, F(a), H, (Oh), gritty character and high porosity. Ah(?$ Mullmoders undergo relatively rapid decomposition Hydromoders are poorly aerated Moders which are of organic residues. However, decomposition and inter- under the influence of prolonged but not permanent mixing promotedby large soil fauna suchas earthworms saturation. They have L, F and H horizons which com- is not extensive enough J"or complete incorporation of prise > 50% of thetotal thickness of organic horizonsin humus materials with the uppermost mineral horizons, the humus formprofile. As a result of prolonged satura- as in Mulls. Mullmoders rnay be associated with internal tion, 0 horizons (primarily Oh)may be developed in the input and decomposition offinely divided root systems, lower portion of the profile. Ah horizons>5 cm thick are in whichcase the Rhizomullmoderis recognized. usually present in the control section.If they are lacking, Mullmoders are distributed most frequently in meso- the H horizons must contain intermixed mineral mate- thermal, temperate and occasionally boreal climates in rials.Associated soils areeither Gleysols, gleyedsub- ecosystems providing favourable moisture and nutrient groups of other mineralsoil orders with well expressed supply forsoil fauna andmicroflora, and yielding easily gleying within50 crn of the mineral surface,or occasion- decomposable litter. ally organic soils. Hydromoders represent a transition 26 betweenterrestrial and semi-terrestrial humus forms common.Base-rich soil parentmaterials are often and havebeen designated as hydromorphic by Wilde associated. ( 1958) and Bernier ( 1968). Key to subgroups (Figure 9) Hydromoders develop under direct influenceof fluctuating orslowly moving waterwhich is generally located 6a 1. Hydromoders that conform to the central concept between 30 and 50 cm from the soil surface. They typi- of the Group. Ohhorizons comprising< 25% of the cally have thin L horizons on the surface, overlaying F thickness of organic horizonsmay be present horizons derived primarily from coniferous litter, bryo- Orthihydromoder phyte tissues and residues of hydrophyticvegetation. 6a2. Hydromoders in which Ah horizons are either ab- Their structure is usuallynon-compact or compact sent or < 5 cm thick. H horizons > 5 cm thick are matted. always present Soil fauna are active in the upper portion of the hori- Ectohydromoder zons which is not subject toprolonged saturation. Fungal 6a3. Hydromoders in which Oh horizons comprise from mycelia are generally present in minor amounts. 25-50% of the totalthickness oforganic horizons.If The H horizons generallyhave weak or massive struc- Ohr horizons >5 cm thick are present, Ahg hori- ture and are greasy in character.They often contain zons may be lacking; otherwise, Ahg horizons > 5 significant amounts of intermixed mineral material,us- cm thick mustbe present ually from siltation and sedimentation. Saprihydromoder Ah horizons aretypically friable with weak granular or Description of an Orthihydromoder blocky structure, occasionally showing evidence of gleying. Ectorganic horizons of Hydromoders average from The following description of a humus form profile has 10 to 20 cm in total thickness while endorganic horizons the characteristicsof the central concept of Hydro- are generally in the 15 to 30 cm range. moders. Theprofile is located near the Nechako River in Hydromoders develop in part under hydrolysis and the Prince Rupert Forest Region. The ecosystem is clas- periodic anaerobic fermentation (Wilde 1958). Decom- sified as the Picea (glauca) - Ribes (lacustre) - Aulocom- position by soil fauna and fungiis generally restricted to mium (palustre) Association on a clayey RegoHumic the upper- horizonswhich are not subjected to prolonged Gleysol formed on a lacustrine veneer. saturation. Hydromoders generally develop under less ~ ~~ ~~~~ acid conditions than Hydromors.Chemical properties of HorizonDepth Description Hydromoders show higher levels of exchangeable bases (cm) and base saturation, and lower C/N values than Hydro- mors, indicating more favourable nutrient regimes for L I I- 10 Coniferousneedles; moss tissues; moist; plant growth. single particle; loose; acerose; no roots; no Hydromoders are distributedin temperate, mesother- visible biota; clear, smooth boundary. mal and boreal climates, in physiographic and/or edaphic F(4 10-4 Moist; non-cornpactmatted; slightly tena- environments where prolonged saturation of the soil is cious; fibrous; few, fine roots, common in-

Orthihydromoder SaprihydromoderEctohydromoder 30 r L, I I

Fzgure 9. Characteristic humus form profiles of subgroups of the Hydromoder group. 27

sects in upper portion; few, white mycelia; Histomoders represent humus formsin whichldecom- clear, smooth boundary. position and synthesis of organic materialsis suppressed Hd 4-0 Moist; black ( 10 YR 2/1 m): weak compact due to low temperatures andlow aeration brought onby matted; moderately tenacious; greasy: plen- saturatedconditions. However, decomposition has tiful, fine and medium roots; no visible biota; reached a moderately advanced state, primarily as a re- clear, smooth boundary. sult of greater levels of nutrients in the water. Histo- moders may be considered as semi-terrestrialhumus Ah 0- 15 Wet; black (IO YR 2/1 m); weak, fine, sub- formsintermediate between the relatively undecom- angular blocky; friable; clay; few, medium posedHistomors and the well humifiedSaprimulls. roots; no visible biota;clear, smooth bound- Theyare distributed in mesothermal,temperate or ary . ~ ~~ -~ - ~-~~~ ~ ~~ ~ ~ ~~ ~~ ~ ~ boreal climatesin physiographicand/or edaphic environments where a high and permanent water table is common in the soils. Groundwater in the ecosystems is gener- 27. Histomoder ally weakly acid. [n.n.; Bernier 1968: Mesic Peaty Mor]

Characteristic humus form profile: S or L, F, H; (Of), Key to subgroups (Figure 10) Om, (Oh) 6b 1. Histomoders in which the Om horizons comprise Histomoders are very poorly aerated Moders which >70% of the total thickness of 0 horizons in the are under the influence of permanent saturation. They humus formprofile are dominated by wetland (0)organic horizons, in par- Orthihistomoder ticular Om, which comprises >50% of the humus form profile. L, F, and H horizons may occasionally be devel- 6b2. Histomodel> in which the Om horizons comprise oped in the upper portionof the profile.Associated soils between 50 and 70%'of the0 horizons in the profile are most frequently Organic, butmay include Gleysols. and areoverlain by Of horizons Histomoders form in environments of prolonged sat- Fibrihistomoder uration resulting from a slow moving subsurface water 6bS. Histomoders in which the Om horizons comprise flow or a stagnant water table,generally located within30 between 50 and 70% of the0 horizons in the profile crn of the ground surface. They typically possess a thin and are underlainby Oh horizons layer of living mosses(S) mixed with litter materials from Saprihistomoder vascular plants, overlying thick Om horizons. These are derived primarily fromtissues of bryophytesand sedges, 6b4. Histomoders in which I,, F and H horizons com- and arealways wet.Thin Of horizons may befound in the prise between 25 and 50% of the total thickness of upper profile. Occasionally Oh horizons occur towards organic horizons in the humus form profile the lower portionof the controlsection. Hydrohistomoder

1 0- HydrohistomoderSaprihistomoderFibrihistomoderOrthihistomoder

1 0-

'0 - $2

L 5 9 30 -

40 -

!50 -

I60 -

Figure 10. Characteristic humus form profiles of subgroups of the Histomoder group. 28

Description of an Orthihistomoder amount of available nutrients toplants, in particular, The following description of a humus form profile hasnitrogen. the characteristics of the central concept of Histomoders. Mulls develop under the influence of relatively a wide The profile is located near Williams Lake in the Cariboo range of temperate, semiarid, mesothermal, subtropical Forest Region. The ecosystem is classified as the Betula and tropical climates. They are generally found in eco- (glandulosa) - Carex(rostrata & aquatilis) - Tomen- systemsdeveloped on base-rich soil parentmaterials, thypnum (nitens) Association on a TypicMesisol formed which may beinfluenced by minerotrophicseepage on an organicblanket. waters. Subtropical and tropicalMulls (Wilde 197 1) were not includedin the taxonomy. ~~ The Mull order is subdivided into four groups based HorizonDepth Description on soil moisture regime, and kind and arrangement of (cm) horizons (Table 10, Figure 1 I). S 3-0 Layer of living mosses. TABLE IO. Synopsis $Taxa the Mull Order Om 0-40 Saturated;reddish-brown (5YR 5/4 m); of massive;tenacious; mushy; plentiful, fine Group Subgroup and medium roots; no visible biota; gradual, - irregularboundary; rubbed fibre approxi- 3 1. Khizomull 3 1 1. Orthirhizornull mately 30%; von Post class 5. 3 12. Crustorhizomull ~ ~~ ~ ~ ~~ 3 13. Vermirhizomull 3 14. Xerorhizomull 3. Mull Order 32. Vermimull 32 1. Orthivermimull 322. Microvermimull The Mull order encompasses humus forms in which 323. Macrovermimull organic matteris intimately incorporated into the upper 33. Hydromull 33 1. Orthihydromull mineral soil instead of accumulating on its surface as in 332. Humihydromull Mors and Moders. Decomposition of organic materials 333. Saprihydromull and f'ormation of humus substances takes place rapidly in 34. Saprimull 34 1. Orthisaprirnull comparison to theMor and Moder orders. Undera sub- 342. Parasaprimull hydric moisture regime, humificationalso proceeds rela- 343. Histosaprimull tively rapidly. However, in these cases, intermixing with 344. Humisaprimull mineral soil does not necessarily take place. Because of 345. Hydrosaprimull the predominance of well humified materials, the semi- terrestrial Mulls are considered to belong to the Mull Key to Groups of the Mull Order Order.This contrasts with semi-terrestrialMors and Moders inwhich moderate to poorly decomposed or- la. Well aerated Mulls which can be temporarily satur- ganic residues predominate over humifiedmaterials. ated by water; Ah horizons >2 cm thick always hlull humus forms are characterizedby Ah horizons or present; F horizons < 1 cm thick inSaprimulls by Ohchorizons. These are generally 2a. Rhizogenous Ah horizons developed from de- overlain by thin L horizons and occasionally Fa horizons composition of dense networkof fine roots of which do not exceed 1 cm in thickness. The Ah horizons herbaceous vegetation, creating a sod'; struc- contain organic matterwhich has beenincorporated into ture is generally blocky the mineralsoil either by active burrowing and comminu- Rhizomull tion by soil fauna, particularly earthworms, or by partial 2b.Zoogenous Ah horizonsdeveloped primarily decomposition of finely divided root systemsof herbace- by active populations of earthworms. Struc- ous (graminoid) plants. In some hydromorphic Mulls, ture is always granular the intermixing of organic matter and mineral soil may Vermimull resultfrom inwashing ofmineral sediments. The Ah 1b. Poorly aerated Mulls; prolonged or permanent sat- horizons of Mulls typically have granular oroccasionally uration by water(hygric to subhydricmoisture (subangular)blocky structure. Thelower boundary gen- regimes) erallymerges gradually into the underlying mineral 3a.Humus form profile dominated by Ah@) horizon. horizons; F horizons always < 1 cm thick. Oh Rapiddecomposition and humification of organic horizons, if present, areless than thethickness materials in Mulls is promoted by active populations of of the Ah(g) soil fauna and abundant colonies of bacteria (Waksman Hydromull 1938).Habitat conditions which promote this activity includegood aeration, balanced moisture supply, 3b. Humus form profile dominated by Oh hori- nutrient-rich soils or seepage water effects, favourable zons; the combined thickness of F, Of, Om temperatures and asupply of easily decomposable litter. and Ah horizons is always less than the thick- Chemical properties indicate thatMull humus formstyp- ness of the Ohhorizons ically have significantly higher values of pH and base Saprimull saturation, and lower C/N ratios relative to Moder and Mor humus forms. In comparison to the other orders, 'Sod - (turf, sward) stratum of soil tilled with roots of grass, Mullsmay be considered as providingthe greatest herbs, etc. (Webster 1959). 29

IC - Rhizomull Vermimull Hydromull Saprimull

L. F. Of. Om c F- -a

2 2o L 5 9 3 30

60 Fzff-Lre11. Characteristic humus form profiles of groups of the Mull order represented by 07thi subgroups.

3 I. Rhizomull 2a2.Rhizomulls that have brittle andfirm, crust-like [n.n.; Wilde 1958: Sward; Barratt 1964: Grassland Mull; horizons in the upper portion of the humus form Wilde 1966, 1971: Rhizol; Hartmann 1952: Kalkreicher profile Mull (Kalkmull) (in part), SalzreicherMull (Salzmull) (in Crustorhizomull part)l 2a3.Rhizomulls in which earthwormsare common; Characteristic humus form profile: (L), (F), Ah structure of the Ah horizons is generally granular Vermirhizomull Rhizomulls are well aerated Mulls in which the Ah horizons are formed through decomposition the of finely 2a4. Rhizomulls which experience prolonged moisture divided root systems of herbaceous (primarily gramin- deficiencies during the growing season (i.e. semi- oid) plants. They typically -possessthin, occasionally dis- arid climates; xeric (to submesic) moisture regimes continuous L horizons overlaying the Ah horizons. F in subhumid climates) horizons may be present, hlowever, they are always very Xerorhizomull thin because oflow levels of above-ground litter production. H horizons aregenera.lly lacking. Description ofan Orthirhizomull The typically dark coloured Ah horizon is characteri- The following descriptionof a humus form profile has zed by subangular blocky or occasionally granular struc- the characteristics of the central conceptof Rhizomulls. ture. A dense network of fine roots is always present The profile is located near Princeton in the Kamloops creating a “sward” or “turf’. Earthworms are generally Forest Region. The ecosystem is classified as the Erio- absent, but where the humus form develops on moist gonum (heracleoides) - Festuca (idahoensis) Association soils influenced by groundwater, they may become more on a loamyOrthic Black Chernozem formed on morainal significant. The humus formprofile averages 10 to 15 cm materials over volcanic bedrock. in thickness butmay extend over25 cm in extreme cases. ~-~~ ~~~ ~~~ ~ ~~ ~~~ ~ ~-~-~ ~ Rhizomulls develop most commonly in subhumid to HorizonDepth Description semiarid climates under anextensive cover of perennial (cm) grasses. Associated soils are typically rich in bases. They ~~~ ~~ ~.~~- ~~ ~~ ~~ ~ ~~~~ ~-.~ ~~ may also form undermoister and cooler climates, provid- L 0.3-0 Leaves and stems of graminoid plants; ing thesite supports well-developeda community ofher- dry; single particle; acerose; loose;no roots; baceous vegetation producing dense rootnetworks. no visible biota; abrupt, broken boundary. Ah 0-10 Moist; black (IO YR 2/ 1 m) to verydark Key to subgroups gray ( 10 YR 3/ 1 d); moderate, medium gran- 2a 1. Rhizomulls which conform to the central conceptof ular; friable; sandyloam; abundant fine the group roots; no visible biota; gradual, smooth boundary. Orthirhizomull ~~~~~~~~ ~ ~ ~~ ~ ~~ ~~ - ~~ ~~ ~~ ~~~ ~~ -~~- ~~ 32. Vermimull HorizonDepth Description [n.n.; Wilde 1954, 1958: Earthworm Mull; Wilde 1966: (cm) ~ ~ ~ - ~~ - ~ ~ ~~~ Vermiol (in part); Romell and Heiberg 193 1: Crumb- L 1-0 Moist;non-compact matted; loose; acerose; mull; Bernier 1968: Fine Mull; Hartmann 1952: Milder common insects, few mycelia; abrupt, bro- Mull] ken boundary. Characteristic humus form profile: (L), (Fa), Ah Ah 0-8 Moist;dark reddish brown (5 YR 3/2 m); Vermimulls are characterizedby thin or discontinuous strong, mediumgranular; friable; loam; 1, and F horizons overlaying well formed, dark coloured, plentiful, fineand medium roots; many zoogenous Ah horizons. Specifically, the F horizons are earthworms; abrupt, irregular boundary. ~~ - < 1 cm, and the Ah horizons are>2 cm. H L horizons, if present, are < 1 cm. The Ah horizons, which are always granular (crumb-like) in structure, have developed by the predominantactivity of soil fauna, particularly earth- 33. Hydromull worms. A strong organo-mineral complex (“clay-humus Duchaufour 1960 [n.n.;Wilde 1958: Fenmull;Wilde complex”)’ results fromthis activity. Earthworm casts are 1966, 197 1: Sapronel; Bernier 1968: Humic Peaty Mor diagnostic fbr these horizons. Dense, fine rootsin the Ah (in part); Kubiena 1953: Anmoor] horizon are absent. The subgroups are derived from the size of the dominant granular structure. Characteristic humus form profile: (L), (Fa), Ah(g) Ver-mimulls show very rapid decomposition and syn- Hydromulls are poorly aeratedMulls which are under thesis of organic materials (thinor absent I, and F). They the influence of prolonged but not permanent satura- are usually found in moisture and nutrient rich habitats tion. They typically possess thin L and F horizons over- in nlesother-maland subtropical climates. Vermimullsare laying the Ah(g) horizons. Due to the influenceofa high the characteristic humus forms of the most productive water table, Oh horizons may form in the profile, but ecosystems forthe growth of severalconiferous tree they never exceed thethickness of the underlying Ah(g). species in southwestem British Columbia. They are us- H or H L horizons may occasionally be found in the ually associatedwith deciduous, coniferous-deciduous or profile. coniferous stands,on well to poorly drainedalluvial habi- Hydromulls develop under direct influence offluctu- tats, with an understory vegetation that yields easily de- ating, slowly moving water generallylocated between 30 composable deciduous litter. and 60 cm from the surface. The humus formremains Key to subgroups saturated during wet periods of the year but becomes moist, at least in the upperprofile, in response to a drop 2b 1. Vermimulls in which the dominantsize of granular in the watertable during summer months. aggregates is 2 - 5 mm The Ah(@ horizons are typically very dark coloured Orthivermimull due to significantamounts of finely dispersed, well 2b2. Vermimulls in which the dominantsize ofgranular humified organic matter. Their structure is generally aggregates is < 2 mm subangular blocky or, occasionally, granular whenmoist. Microvermimull During saturated periods, the structurebecomes massive 2bS. Vermimulls in which the dominantsize of granular with a mucky character. The mineral component of the aggregates is > 5 mm Ah horizon originateslargely from in-washingof mineral Macrovermimull sediments. Hydromulls are formed under the influence of hydrolysis and the intense activity of anaerobic organisms Description of an Orthivermimull (Wilde 1958). Rich populations of aerobic organismsin- cluding earthworms may be present, particularly in the The following description of a humus form profile is upper humus form profile where saturation is less pro- characteristic of the central concept of the Vermimulls. longed. Chemical properties are characterized by high The profile is located in MacMillan Park(Vancouver values of base saturation andmildly acid to neutral pH. Island) in the Vancouver ForestRegion. The ecosystem is Synthesis and decomposition of fresh organicmaterials classifiedas theThuja (plicata) 8c Abies (grandis) - proceeds rapidly. Pseudotsuga (menziesii) - Polystichum (munitun) - Tia- Hydromulls are formed in temperate and mesother- rella(trifoliata) Association on a fine-loamyOrthic mal climates in physiographic or edaphic environments Humo-Ferric Podzol, Sombric phase formed on an allu- where prolonged saturation of the soil is common. vial terrace. Ground water feeding the sites is enriched with bases. Associated soils are eitherGleysols, gleyed subgroups of ‘Clay-humus corrlplex refers to the stable binding of tinely di- other mineral soil orders with well expressed gleying vided humus substances with clay mineral particles. Organic within 50 cm of the surface,or occasionally organic soil. matter is precipitated onto surfaces of clay particles, forminga “pigment” (Babel 1975). Fornlation of these complexes is pro- Key to subgroups (Figure 12) moted by intimate blending of mineral and organic constituents in the gut of earthworms (Kubiena 3953). Although the 3a 1. hydrom mulls that conform to the central conceptof concept of clay-humus complexes is valid, there is little ana- the group lytical evidence to prove their existence in forest humus forms. Orthihydromull 31

Orthihydromull Humihydromull SaprihydromullHumihydromull Orthihydromull 2o r

Fzpre 12. Characteristic humusform profiles of subgroup; -\f the €!ydromull group.

Ya2. Hydromulls in which H( L ) horizons are present 34. Saprimull within the humus form profile. thicknessThe ofthe H( r ) is < the thickness of theAh@) horizons [n.n; Berrlier 1968: Humic Peaty Mor (in part); Kubiena Humihydromull 1953: Pitch Peat Anmoor (in part)] 3a:I. Hydromulls in which Oh or Oh1horizons are pre- Characteristic humus form profile:(L), (F), (Of),(Om), sent within the humus formprofile. The thickness Ohr of the Oh(L ) is < that of the Ah(g) horizons Saprimulls are very poorly aerated Mulls which are Saprihydromull under the influence of more or less permanent saturation. They are dominated by Oh1 horizons, which al- Description ofan Orthihydromull ways comprise more than 50% of the humus form profile. The characteristic horizon sequence includes thinL, The following description ofa humus form profilehas F, Of or Omhorizons, generally under 2 cm thick, over- the characteristics of the central concept of Hydromulls. layingthe prominent Oh r horizons. These horizons The profile is located in the U.B.C. Research Forest in may not contain incorporated mineralsoil, in which case the VancouverForest Region. The ecosystem is classified the Parasaprimull Subgroup is recognized. Associated as the Thuja(plicata) - Ruibus (spectabilis) - Polystichum soils are most frequently Organic. However, they may (munitum) Association on a clayey Orthic HumicGleysol occasionally be formed onGleysols. formed onglaciolacustrine over glaciomarine materials. Saprimulls develop under conditions of prolonged saturation from a stagnant water table, generally located

~~~ ~~ within 30 cm of the ground surface. The humus form HorizonDepth Description remains wet for the greater portion of the yearwith the (cm) upper horizons becomingmoist for short periods during ~ ~~~ dry months. L 2-0.5 Herbaceous foliage and moss tissues; moist; The Ohl horizons are typicallyvery dark coloured, weak non-compact matted; leafy; loose; no with massive structure and greasycharacter. The horizon roots; no visible biota; abrupt, wavy boun- is generally always wet. The intermixed mineral particles dary. generally originate fromin-washed sediments. Humificationproceeds rapidly in Sapx-imulls. The H 0.5-0 Moist;weak, medium granular; greasy; nlinerotrophic groundwaterwhich influences the humus very friable; few, fineroots; common, med- form promoteschemical “weathering” andactive decom- ium droppings; abrupt,wavy boundary. position by predominantlyanaerobic organisms. Peri- odic aerobic decompositionmay take place in the upper Ah 0-20 Moist; very dark gray-brown ( 10 YR 3/2 m); profile.However, decomposition products tend to ac- medium,sub-angular blocky; clayloam; cumulate due to excessive moisture. As in Hydromulls, friable; abundant, fine to coarse roots; few chemical properties of Saprimulls are characterized by earthworms in upper horizon; clear, wavy high values of base saturation, exchangeable bases, par- boundary. ~~ ~ ~~ ticularly Ca, andmildly acid to neutral pH. 32

Saprimulls are most frequently distributed in temp- 3b5. Saprimulls in whichthe combined thickness ofF, Of erateand mesothermal climatesin physiographic or and Omhorizons is < 2 cm. Ah(g) horizons>5 cm edaphicenvironments where a high andpermanent thick are presentwithin the humus form profile but water table is common. Groundwater of ecosystems is do not exceed the thickness of the Oh or Ohc always high in bases, particularly Ca. Ecosystems associ- horizons ated with Saprimullsare generallysparsely or non- Hydrosaprimull forested withhydrophytic herbaceous vegetation predominating. Description of an Orthisaprimull Key to subgroups (Figure 13) The following descriptionof a humus form profilehas the characteristics of the central concept of Saprimulls. 3bl. Saprimulls in which the combinedthickness ofF, Of The profile is located in the U.B.C. Research Forest in and Om horizons is < 2 cm. The remaining humus the Vancouver Forest Region.The ecosystem is classified form profile is comprised of Oh c horizons as the Thuja(plicata) - Lysichitum (americanum) Associ- Orthisaprimull ation on a Typic,- Humisol, Lithic phase, formed on an 3b2. Saprimulls in which the combinedthickness of F, Of Organic veneer Over quartzdiorite bedrock. and Om horizons is<2 cm. The remaining humus ~ ~ ~~~~~~~~~ - ~ ~~ ~ ~~ form profileis comprised of Oh horizons DescriptionHorizon Depth

Parasaprimull (cm) ~ ~~~~~~ ~ ~~~~ ~~~~~~ ~ ~~ 3 b3. Saprimulls inwhich F, Of orOm horizons are > 2 L 2-0 Red alderfoliage; moist; non-compact mat- cm thick but do not exceed 50%ofthe totalthick- ted; loose;leafy; noroots; few clusters of ness of 0 horizonsthehumusin form profile fine, whitemycelia; abrupt, brokenboun- Histosaprimull dw. 3b4. Saprimulls inwhich thecombined thickness of F, Of Oh1 0-45 Wet;very dark gray (10 YR 3/1 m); weak; andOm horizons is

Humisaprimull ~~~~~~ ~ boundary. ~ ~~~~~ ~ ~~

Orthisaprimull Parasaprimull Histosaprimull Humisaprimull HydrosaprimullHumisaprimullHistosaprimullParasaprimullOrthisaprimull

Fzgure I?. Characteristic humus form profiles of subgroups of the Saprimull group. 33 Testing of the Classification

Theproposed taxonomic classification of humus parameters plus thickness of ectorganic horizons in the forms was tested to substantiate the significance of the humus form profile were the seventeenvariables used in differentiated taxa. The testing was carried out in rela- testing. Analytical methods werethose used in the Pedol- tion to a range of chemical properties'.was It designed to ogy Laboratory Manual (Lavkulich1978). demonstrate the relationships of taxa to the properties A discriminant analysis was employed to determine which had not been used as differentiae. The results relationshipsof the differentiated taxato theabove presented have severallimitations: they are based on chemical properties. The number of recognized taxa is materials from a small geographical area, hence, only the same as the number of groups used in the analysis. some taxa of the presentsystem are included; they deal Usingdiscriminant analysis, one canmathematically only with orders and groups,since properties needed for select the chemical parameter(s) which in combination classificationof subgroup:j were not consistently de- are able to separate the taxa recognized independently. scribed;the parameters analyzed may notrepresent Each group is characterized by a unique linear function, those chemical properties which reveal the different na- which in this case is generated from the chemical para- ture of humus forms; and, finally, the results for cat- meters whichbest serve to distinguish between the egories are evidently dependent on the representationof groups. classes in each category. In this test, representation for A stepwise discriminantanalysis was performed on the some classesmay notbe adequate, so thereader is data using a computer program (Halm1970) available at cautioned to view the presented datawith this in mind. the Computing Centre, University of British Columbia. Sampling was done during asynecological study con- F-probability for inclusion and deletion of parameters ducted by Klinka (1976) atthe University of British Col- (variables)were 0.100 and0.101, respectively. Inthe umbia Research Forest near Haney, approximately 60 analysis, the chemical parameters are entered into linear km east of Vancouverin southwestern British Columbia. functions in a stepwise manner. Each time a parameteris The study was carried outin that portion of the Forest added, astatistical testis done to determineif the distinc- located within theCoastal Western Hemlock(CWH) Bio- tion between the groups has increased.If its inclusion is geoclimaticZone of British Columbia. The area is not beneficial,it is dropped; otherwise,it is retained. The characterized by a mesothermal climate and is underlain usefulness of each parameter is tested every time a new by acid igneous rocks, mainly quartzdiorite. Glacial till is one is added, and those no longer making a significant the most common parent material with loose till, fre- contributionare dropped. Parameters are ranked ac- quently overlying compacted till. The soils are typically cording to their performance in maintaining the group coarse-textured, contain a high amount of coarse frag- separation. This order of importance is displayed in the ments and areacidic with acidity decreasing with depth. following tables. In addition,canonical variables for each The soils are classified mailnly as Humo-Ferric or Ferro- parameter chosen for the discriminant function arecal- Humic Podzols (CSSC 19713) with prevailing Mor humus culated and plottedto give a two-dimensional illustration forms. The forests are dominated by western hemlock of the degree of separation of groups.calculation The of [Tsugu heterophyllu (Raf.)S'arg.] but contain significant canonical variables is from the statistics for the chemical amounts of western redcedar(Thujaplzcutu Donn ex Don parameters and can be used only on a relativebasis. For inLamb). Douglas-fir [I'seudotsugu menziesii (Mirb.) specific formulae concerning any steps described, the Franc01 is common at lower elevations and amabilis fir reader should consult the documentationavailable at the [Abies urnubilzs (Dougl.) Forbes], at higher elevations. University of B.C. Computing Centre. Compositesamples of ectorganic horizons in the The entireset of chemical data for 166 humus forms humus form profiles werecollected from the 166 pedons was subjected to discriminant analysis to distinguish be- within a number of ecosystems (biogeocoenoses) repre- tweenthe three orders, Mor, Moder and Mull. The senting a wide range of ecological conditions and pro- chemical properties conform closely to the original clas- ductivity levels. Using the present system, the following sification; nearly 90 percent of the samples were sep- humus form groups were identified: Hemimor, Hum- arated into the three orders on the basis ofchemical imor, Hydromor, Mormoder, Hydromoder, Vermimull, properties (Table 1 1). andHydromull. A more complete description of the study area, sample preparation and analytical methods TABLE 1 1. Clasxfication Table -Percentage of Humus Form has been givenby Klinka (1976). Classified into Each Order The samples were analyzed for pH (inH20), organic matter content (OM%), total nitrogen (N%), exchange- Original classification Discriminant analysis able cations (Ca, Mg, Na and K) and cation exchange Mor Moder Mull capacity (CEC, in NH40AC extraction, pH 7), and total Mor 98 2 0 Ca, Mg, Na, K, Fe, AI and Mn. Carbon:nitrogen (C/N) Moder 11 80 9 ratio and base saturation (BS%) were calculated. These Mull 0 'LO 80

'Similar testing involving organic andinorganic constitutents of It appears that themorphological properties of Mors humus forms has been carried out in the CWH Zone by Klinka correlate well with common chemical properties, while and Lowe ( 1975, 19'76a, 197611)and Lowe and Klinka (1 98 1). for Moders andMulls, there is some overlap.Since Mod- 3 4

ers are considered by many workers to be transitional similar humus forms may differ in other properties can- between Mors and Mulls, the suggested “misclassifica- not be ruled out. tion” of 20% of the Modersis not surprising. However, Eleven variables, among them pH andC/N ratio, were thiscould also be indicative of errors in theoriginal selected as contributingsignificantly to the discriminant classification, in which case it may reveal problems in the functions. They are located in the order of importance identificationof those humus forms described in the from top to bottom in Table 12. Six variables, among absence of the currently applied standards. Discriminant them thickness of ectorganic horizons and organic mat- analysis provides an efficient basis for examining such ter content, were not included,mainly becauseof similar discrepancies because the “misclassified” samples can be valuesthroughout the whole set or large values of identified. However, thepossibility that morphologically standarddeviations. The plot ofcanonical variables shows the relationship between Mor, Moder and Mull I’AB1.E 12. Means and Standard Deuz2ztions for Discriminating orders(Figure 14).Despite a considerabledispersion Chemical Properties of Mor, Moder, and MullOrders around means for orders, separation intoclusters three is in the U.B.C.Research Fore.ct‘ evident. On the other hand, it is also apparent that affinities exist between orders, which points out the con- Humus form order Mor Moder Mull tinuous natureof humus forms. Number ofsamples 25 .5 6 2.5 - Other humus forms cannow be classified into orders Discriminating parameters on the basis of this chemical analysis using computed Keaction (pH) 3.8 4.3 5. I linear functions (Table13). (0.27)* (0.4 1) (0.47) Carbon:nitrogen ratio 38.1 24.8 22 .0 TAB1.E 13. An Example of Chslfication Functions Determined in (9.24) (5.98) (5.66) the Discriminant Analysis Rase saturation (%) 12.4 17.9 40. I (5.65) (9.49) (17.46) l‘otal magnesium (ppm) 730 1840 2600 Humus form order Mor Moder Mull (428) ( 1349) (1370) Constant -224 -195 -270 .. ~ Cation exchange capacity Parameter (meq/ IO0 gm) 122.3 102.2102.5 (37.19) (29.83) (126.85) Reaction (pH) 57.9156.57 50.22 X1 Exchangeable potassium Carbon:nitrogen ratio x2 2.3432.2 17 2.332 (meqi I00 gm) 1.91 1.1 1 1.55 Base saturation (5%) x3 -0.530-0.554 -0.0856 (0,962) (0.533) (0.82 I) Total magnesium (5%) 0.0073X4 0.0083 0.0099 Total aluminum (ppm) 8190 1438014610 (I 1452) (128’79) (1 1509) Cation exchange capacity (meqi 100 gm) X5 -0.0056 -0.0 100 0.0222 62301667014070 (6060) ( 1497 1) ( 10707) Exchangeable potassium (meq/ 100 gm) -0.543X6 -1.175 -1.745 Total nitrogen (5%) 1.741.53 1.28 (0.275)(0.390) (0.426) Total aluminum (ppm) x7 -0.0010-0.0012-0.001 1 Total sodium (ppm) 180 140 I90 Total iron (ppm) 0.00040.00060.0005X8 (40) (74) (76) Total nitrogen (ppm) x9 67.53 7 1.87 79.15 Exchangeable magnesium Total sodium (ppm) 0.2380.246X100.286 4.63 (meqi 100 gm) 2.25 2.72 Exchangeable magnesium (0.893) (1.479) (2.337) (meqi 100 gm) XI 1 -2.379-2.102 -3.009 Remaining parameters ~- Thickness of humus form (cm) 13.1 8.3 6.8 Using the above table, it can be determined that the (10.77) (5.85) (10.33) functions are: Organic matter (%) 80.0 64.6 65.6 YMOR = - 195 + 50.22 (XI) + 2.343 (X2) - (1 1.88) (18.51) (17.00) 0.530 (X3) ...... -2.379 (X I I)

Exchangeable calcium YMODER = -224 + 56.57 (XI) + 2.2 I7 (X2) - (meqi 100 gm) 9.28 14.2932.02 0.554 (X3) ...... -2. 102 (XI 1) (4.538) (8.558) (16.199) YMULL = -270 57.91 (XI) 2.332 (X2) - Total calcium (ppm) 3650 645013000 + + 0.0856 (X3) ...... -3.009 (X I 1) ( 1524) (2948)(4822) Total potassium (ppm) 840 8‘30 I 100 (304) (430)(349) The data areclassified into the groupwith the largest Y value. Total manganese (ppm) 260 1230 I4 IO m9) ( 17’33) ( 1988) In’the next step, the dataset for the Mor Order, includ- ‘Based on ectorganic portionof humus forms. ing 85 samples,was subjected to discriminant analysis to ‘Numbers in parenthesis are standard deviations. distinguish between the three groups, Hemimor, Humi- 35

Moders -4.01 0 Mulls 0 * group mean -5.011 I 1 1 I 1 I I -6.0 -5.0 ~4 0 -3.0 -2.0 -1.0 0 1.0 2 0 3 0 4.0 5.0 6.0 7.0

Figure 14. The plot of canonical variables for chemical properties which were used to discriminate between Mors, Moders, and Mulls.

-2.0

Humimor -3.0 c Hydromor * group mean

-4.01 I -80 ~7.0 -6.0 -5.0 ~4 0 -30 -2.0 ~1 0 0 1 0 2 0 3.0 4.0 5 0

Figure 15. The plot of canonical variables for chemical properites which were used to discriminate between Hemimors, Humimors and Hydromors. 36 mor and Hydromor. Thechemical properties, however, TABLE 15. Means and Standard Deviationsfor Discriminating conform less satisfactorily to the original classification; Chemical Propertiesof Hemimor, Humimorand only 68 percentof sample forms separated into the three Hydromor Groupsin the U.B.C.Research Forest groups (Table 14). Humusform group HemimorHumimor Hydromor TABLE 14. Classzfication Table - Percentage ofHu7nu.sFom Number of samples 37 37 11 Classzfied into Each Group Discriminating parameters Y.

Original Classification Discriminant analysis Total calcium (ppm) 3750 4290 1150 Hemimor Humimor Hydromor (1 183)’ (1 188) (995) Thickness (cm) 8.7 17.3 14.2 Hemimor 27 70 3 (5.20) (13.49) (9.28) Humimor 62 38 0 Total magnesium (ppm) 740 840 350 Hydromor 18 0 82 (424) (423) (2 13) Total aluminum (ppm) 4950 5780 27180 (5315) (5020) (2 1263) Canonical variables complement the results given in Carbon:nitrogen ratio 36.0 39.2 4 1.0 the classification table (Figure 15). While the Hydromor (5.50) (1 1.88) (8.42) humus form appearto be well separated, a considerable overlap exists between Hemimors and Humimors. Remaining parameters Assuming that the identification of F and H master Organic matter (5%) 81.3 78.6 80.7 horizons was correct, it might be found that the“misclas- ( 10.91) (12.04) (14.87) sification” is due to the fact that an intermediate class Reaction (pH) 3.7 3.8 4.2 between Hemimors and Humimors had not beenrecog- (0.23) (0.17) (0.44) nized in the study used for the testing, while the Hemi- Total nitrogen (7%) 1.33 1.25 1.19 humimor, which includes in part, Bernier’s (1968)Fibri- (0.229) (0.784) (0.366) Humimor and Humi-Fibrimor,is recognized in the present system. It is also possible that a satisfactory separa- Exchangeable calcium tion based entirely on these chemical properties cannot (meqi 100 gm) 9.89 10.49 3.18 (3.82 1) (4.198) (3.048) succeed. This should be determined by further studies. The minor non-conformity in the classification of‘ Hy- Exchangeable magnesium dromors may be related to uncertainty in the identifica- (meqi 100 gm) 2.38 2.40 1.31 tion of F and Omhorizons, or it may indicate affinities in (0.762) (0.77 1) (1.168) chemicalproperties betweenHemimors and Hydro- Exchangeable potassium mors. A Hemihydromorgroup in thistaxonomy has (meq/ 100 gm) 2.16 1.79 1.5 1 been provided for such segregation. (1.051) (0.869) (0.793) Five variables were selected as contributing signific- Cation exchange capacity antly to the discriminant functions. They are listed in (meqi 100 gm) 115.3 130.9 1 16.6 order of importance in Table 15. Total Mg and C/N ratio (33.35) (37.73) (44.7 1) had been used previously, whereas total Ca, thickness, Base saturation (5%) 13.8 12.3 7.7 and total AI were added todiscriminate between the (5.04) (3.78) (9.68) groups of the Mor order.A low content oftotal Ca and a Total sodium (pprn) 140 140 I40 high content of total AI, which are characteristic for the (40) (4 1) (42) Hydromors, contributed to their separation fromHemi- Total potassium (ppm) 920 770 790 mors and Humimors. (336) (264) (275) The data set for the Moder Order, including 56sam- Total iron (ppm) 4820 7000 8040 ples, was subjected to discriminant analysisto distinguish (3990) (6303) (9798) between the two groups, Mormoder and Hydromoder. Total manganese (ppm) 300 240 230 The chemical properties conform well to the original (254) (306) (472) classification; 80 percent of samples were identicallyclas- sified (Table 16). ‘Numbers in parenthesis are standard deviations. Only two variables, organic matter content and total Fe, were selectedas contributing significantly to the dis- TABLE 16. Classification Table -Percentage ofHumus Fom criminant functions. They arelisted in order of import- Chsfied into EachGroup ance in Table 17 andare followed by theremaining variables.For the most part, there are close affinities Original classification Discriminant analysis between the properties listed for these two groups. A MormoderHydromoder relatively low organic matter contentin the organic horizons seems to be a common characteristic for Mormod- Mormoder 19 81 ers. Similarly, totalFe appears to increasewith increasing Hydromoder 75 25 mineral matter contentas well as moisture content. 37

The classification discrepancies between Mormoders tween the two groups, Vermimull and Hydromull. The and Hydromoders may be related either to an uncer- chemical properties conformwell to theoriginal classifi- taintyin the identification of terrestrialand semi- cation; 84 percent of samples were identically classified terrestrial organic horizons or to the possibility that a (Table 18). perfect separation based entirelyon these chemicalproperties cannot succeed. TABLE 18. Classfiation Table - Percentage of Humus Fom Chsfied into each Group TABLE 17. Means and Standard Deviationsfor Discriminating Variables of Morntoder and Hydromoder Groups in the U.B.C. Research Forest Original classificationDiscriminantanalysis VermimullHydromull

Humus form group Mormoder Hydromoder Vermimull 16 84 17 83 Number of samples 48 8 Hydromull Discriminatinp Darameters Onlytwo variables, C/N ratioand total AI, were Organic matter(%) 62.3 78.4 selected as contributingsignificantly to the discriminant (18.44)' (12.56) functions. They are listedin order of importance to- Total iron (ppm) 16260 19160 gether with the remainingvariables inTable 19. Total AI (15013) (15047) and/or Fe appear tobe useful in separating humus forms

~~ ~ ~ (Hydromors,Hydromoders, Hydromulls) under the Remaining parameters permanent influence of excessive moisture.However, the selection of a nearly identical C/N ratio as a discrim- Thickness (cm) 7.6 12.1 inating variablebetween the Vermimulls and Hydro- (5.31) (7.77) mulls was not expected and was attributed to different Reaction (pH) 4.3 4.4 valuesfor the standard deviations of the respective (0.40) (0.42) means. Total nitrogen (%) 1.50 1.76 (0.389) (0.336) TABLE 19. Means and Standard Deviationsfor Discriminating Carbon:nitrogen ratio 24.4 27.0 Variables of Vernimull and Hydromull Groupsin the (5.33) (9.16) U.B.C. Research Forest Exchangeable calcium 14.21 14.78 (meqi 100 gm) Humus form group Verrnimull'Hydromull' (8.787) (7.528) of samplesNumber of 19 6 Exchangeable magnesium - (meqi 100 gm) 2.69 2.9 1 Discriminating parameters (1.493) (I .468) ratio 22.1 2Carbon:nitrogen 22.1 ratio 1.8 Exchangeable potassium (8.52)(4.74)2 (meqi 100 gm) 1.14 0.9 1 (0.550) (0.383) Total aluminum (ppm) 2776010460 (6503). (1452 1) Cation exchange capacity (meqi 100 gm) 101.7 107.6 Kemaining parameters (31.85) (12.08) Thickness (cm) 16.7 3.7 Base saturation (R) 18.0 17.5 (14.49) ( 17.96) (9.87) (7.28) Organicmatter content ('3) 53.5 69.4 Total calcium (ppm) 6600 5550 (3.23) (19.98) (3073) ( 1952) Reaction (pH) 5.1 5.0 Total magnesium (ppm) 1990 9 10 (0.29) (0.52) (1387) (489) Total nitrogen (5%) 1.44 1.83 Total sodium (ppm) 180 150 (0.254)(0.432) (79) (34) Exchangeable calcium Total potassium (ppm) 940 580 (meqi 100 gm) 20.57 34.64 (459) (229) (16.6(7.624) 19) Total aluminum (ppm) 13840 17620 Exchangeable magnesium ( 12649) (14661) (meqi 100 gm) 5.2 1 2.79 Total manganese (ppm) 1100 2050 (0.675)(2.382) (1501) (302 1) ~- Exchangeable potassium (meqi 100 gm) 1.6 1 1.38 'Numbers in parenthesis are standard deviations. (0.733) (1.1 19) Cation exchange capacity The data set for theMull Order, including25 samples, (meqi 100 gm) 79.1 133.1 was subjected to discriminantanalysis to distinguish be- (7.96)(143.87) 38

TABLE 19. Means and Standard Deviations for Discriminating The classification discrepancies likely originated from Variables of Vermimull and Hydromull Groupsin the using ectorganic horizons (for themost part, litter mate- U.B.C.Research Forest - Continued rials) as representative of Vermimulls. Although a discrimination using organic horizons could be successful, Humas form moup Vermimull’Hydromull‘ representing“terrestrial” Mulls by diagnosticmineral horizons is considered to be more meaningful. However, Base saturation (%) 42.8 3 1.6 not all Mulls, particularly those under the permanent (18.95) (7.36) influence of excessive moisture, need to have a dark- Total calcium (ppm) 13640 10980 coloured surface mineral horizon enriched in organic (5703) (2769) matter in thecontrol section.Consequently, the rep- Total magnesium (ppm) 2490 2960 resentation of Mull humus forms by both mineral and (1311) (1617) organic horizons seemsto be unavoidable. Total sodium (ppm) 173 263 In general, discriminantanalysis substantiated thesig- (64.4) (80.9) nificance of the differentiated taxa recognized on the Total potassium (ppm) I110 1060 basis of morphological properties. It showed that mor- (346) (388) phological properties canbe used as predictorsof chemical properties (inorganic constitutents), thus confirming Total iron (ppm) 1 1350 22670 (8823) (12381) the approach adopted for humus form classification. It also provides an efficient tool for examining the nature Total manganese (ppm) 960 28 10 of any differences which are found and canprovide (933) (3568) equations for numericalclassification. For these reasons, it should be usedin testingthe system, in preparing akey ‘Values refer to ectorganic horizons (mainly litter materials) tothe classification and in determiningquantitative above Ah horizons, or to Oh horizons. properties; a moreprecise definition of taxain the system ‘Numbers in parenthesis are standard deviations. will result. 39 Literature Cited

Agriculture Canada, Research Branch.1976. Glossary of ing Centre, University of British Columbia, Van- terms in soil science. Publication 1459.44 p. couver, B.C.,revised 1975. 14 p. Armson, K.A., 1977. Forest !soils: properties and proces- Hartmann, F., 1952. Forstokologie. George Fromme & ses. University ofToronto Press, Toronto. 390 p. Co., Wein. 460 p. Babel, V., 1975. MicromorphLology of soil organic matter. Heiberg, S.O., andR.F. Chandler. 1941. A revised p. 369-473. In J.E. Geiseking (ed.)Soil components. nomenclature of forest humuslayers for the north- Vol. 1 Organic components. Springer Verlag, New eastern United States. Soil Sci. 52: 87-99. York. Bardsley, C.E. and J.D.Lancaster. 1965. Sulfur. p. 1102- Heinselman, M.L., 1963. Forest sites, bog process, and 11 16. In C.A. Black el al. (eds.) Methods of soil peat land types in the Glacial Lake Agassiz Region, analysis. Agronomy 9, Amer. Soc. Agron., Madi- Minnesota. Ecol. Mon. 33(4): 327-374. son, Wis. Hodgson, J.M., 1978. Soil sampling and soil description. Barratt, B.C., 1964. A classification of humus forms and Clarendun Press, Oxford. micro-fabrics of temperate grasslands. J. Soil Sci. Hoover, M.D. and H.A. Lunt.1952. A key for theclassifi- 15: 35 1-356. cationof forest humus types. SoilSci. SOC.Am. Bascomb, C.L., 1968. Distribution of pyrophosphate ex- Proc. 16: 368-370. tractable iron and organic carbonin soils ofvarious Howard, P.J.A., 1969. The classification of humus types groups. J. Soil Sci. 19(2): 25 1-268. in relation to soilecosystems. p. 4 1-54.In J.G. Sheals Bernier, B., 1968. Descriptive outline of forest humus- (ed.) Thesoil ecosystem. System.Assoc. Publ. No. 8. form classification. Proc. 7th meeting of CSSC Ed- Klinka, K., 1976. Ecosystem units,their classification, monton. 16 p. interpretation and mapping in the University of Bremner, J.M., 1965. Nitrogen availability indexes.p. BritishColumbia Research Forest. Ph.D. thesis, 1324-1345. In C.A. Black etal. (eds.) Methodsof soil University of British Columbia, Vancouver, B.C. analysis. Agronomy 9, Amer. SOC. Agron., Madi- 622 p. son, Wis. Klinka, K., F.C. Nuszdorfer and L. Skoda. 1979. Biogeo- Brewer, R., 1964. Fabric and mineral analysis of soils. climatic units of central and southern Vancouver Wiley Publishers, New York. 470p. Island. Province of British Columbia, Ministry of Canadian Soil SurveyCommittee (CSSC), 1978. The Forests. 120 p. Canadian system ofsoil classification. Canada Dept. Klinka, K. and L.E. Lowe. 1975. Organic constituents of ofAgriculture, Publ. 1646. Supplyand Services forest humus layers in the Coastal M’estern Hem- Canada, Ottawa. 164 p. lock BiogeoclimaticZone of BritishColumbia in Chapman, H.D., 1965. Caticm-exchange capacity. p. 1- 89 relation to forest ecosystems. 1. Proximate analysis. 901. In C.A. Black el! al. (eds.)Methods ofsoil Research Note No. 74. B.C.F.S. Research Division, analysis. Agronomy 9, Amer. SOC.Agron., Madi- Victoria, B.C. 16 p. son, Wis. Cline, M.D., 1944. Principles of soil samples. J. Soil Sci. -~ l976a. Organic constitutents of forest humus 58: 275-288. layers in the Coastal Western Hemlock Biogeocli- matic Zone of British Columbia in relation to forest Duchaufour, P., 1960. Precis de pedologie.Masson, ecosystems.2. Humus fraction distribution. Re- Paris. 418 p. search Note No. 75B.C.F.S. Research Division, Vic- Dumanski, T., (ed.) 1978. R4anual for describing soils in toria, B.C. 7 p. the field.Land Resource Research Institute, Re- search Branch, Agriculture Canada.92 p. -~ 1976b. Organic constituents of forest humus layers in the Coastal Western Hemlock Biogeocli- Flaig,W., 1975. Biochemistry of soil organicmatter. matic Zone ofBritish Columbia in relation to forest p. 3 1-68. tn Organic material as fertilizer. Soil Re- ecosystems. 3. Optical properties of humic acid sources,Development and Conservation Service, fractions. Research Note No. 76. B.C.F.S. Research Landand Water Development Division, FAO, Division, Victoria, B.C. 17 p. Rome. Forsslund, K.H., 1945. Studier over det lagre djurlivet i Kononova, M.M., 196 1. Soil organic matter. Transl.T.Z. nordsvenskskogsmark. Medd. Skogsforsoksanst Nowakowskiand G.A. Greenwood. Permagon 34: 1-283. Press, New York. 450 p. Gardner, W.H., 1965. Water content. p. 82-127. In C.A. Kowalenko, G.F. and L.E. Lowe. 1972. Observations on Black et al. (eds.) Methods of soil analysis. Agron- the bismuth sulfidecolorimetric procedure for sul- omy 9, Amer.SOC. Agron., Madison,Wis. fate analysis in soil. Comm. Soil Sci. Plant Anal. 3: Halm, J., 1970. Stepwise discriminant analysis. Comput- 79-86. 40

Krajina, V.J., 1969. Ecology offorest trees in British Romell, L.G. and SO. Heiberg. 1931. Types of humus Columbia. Ecology of Western North America2( 1): layers in the forest of northeastern United States. 1-146. Ecology 12: 567-608. Kubiena, W. 1953. The soils of Europe. Thomas Murby Schmidt, R.L. 1978. Activities of the B.C. Forest Service & Co., London.3 18 p. in ecological classification. p. 13-17.In Proc. eco- Lafond, A. 1952. La conservation de I’humus. Compt. logical classification of forest land in Canada and Rend. Assoc. Can. Conserv. p.23-30. northwestern U.S.A. Can. Inst. of For. and Uni- versity of British Columbia, Vancouver, B.C. Lavkulich, L.M. 1978. Methods manual. Pedology Lab- oratory. Soil ScienceDepai-tment, University of Soil Science Society of America(SSSA). 1970. Glossary of British Columbia, Vancouver,B.C. 224 p. soil science terms. SSSC, Madison. Wis. 27 p. Lowe, L.E., 1974. A sequential extraction procedure for Soil Survey Staff. 1975. Soil taxonomy. Handbook No. studying the distribution of organic fractions in 436, U.S. Dept. of Agriculture, Soil Conse:vation forest humuslayers. Can. J. For. Res. 4: 446-454. Service, Washington,D.C. 754 p. Lowe, L.E., 1975. Fractionation of acid-soluble compo- Sukachev, V.N. and H. Dyllis. 1964. Fundamentals of nents of soil organic matter using polyvinyl pyr- forestbiogeocoenology. Oliver and Boyd Ltd., rolidone. Can.J. Soil Sci. 55: 119-126. Edinburgh and London.672 p. Thornthwaite, C.W. An approach towarda ra- Lowe, L.E. and K. Klinka. 198 1. Forest humus layers in 1948. the Coastal Western Hemlock Biogeoclimatic Zone tional classificationof climate. Geogr. Rev. 38: of British Columbia in relation to productivity and 55-94. pedogenesis. Province of British Columbia, Min- Thornthwaite, C.W. and J.R. Mather. 1955. The water istry of Forests (inpress). balance. Drexel Inst. of Technol., Publ. in Clima- tology 1): 1- Mader, D.L. 1953.The physical and chemical character- 8( 104. istics of the major types of forest humus found in Thornthwaite, C.W., J.R. Matherand D.B. Carter. 1957. the United States and Canada. Soil Sci. Soc. Am. Instructions and tables for computing potential Proc. 17: 155-158. evapotranspiration and the water balance. Drexel Major, J. 1963.A climatic index tovascular plant activity. Inst. of Technol., Publ. in Climatology lO(3): 183- Ecology 44: 485-498. 31 1. Trowbridge, R. (ed.) 1980. First progress report of the Muller, P.E., 1878. Studier over Skovjord. Tidskr. Skov- working group on organic horizons, folisols, and brug. 3: 1- 124. humusform classification.Land Resource Re- Olsen, S.R. and L.A. Dean. 1965. Phosphorus. p. 1035- searchInstitute, Research Branch, Agriculture 1099. Zn C.A. Black et al. (eds.)Methods of soil Canada. 36 p. analysis.Agronomy 9, Amer. Soc. Agron., Madi- Waksman, S.A. 1938. Humus - origin, chemical composi- son, Wis. tionand importance in nature. Williams and Parkinson, J.A. and S.E. Allen. 1975. A wet oxidation Wilkins, Baltimore. 526 p. procedure suitable for the determination of nitro- Waring, S.A. and J.M. Bremner. Ammonium pro- gen and mineral nutrients in biological material. 1964. duction in soil under waterlogged conditions as an Comm. Soil Sci. and Plant Anal. 1): 6( 1- 1 1. index of nitrogenavailability. Nature 20 1 : 95 1-952. Peech, M., 1965. Hydrogen-ion activity. p. 914-925.In Whistler, R.L. and M.L. Wolfram. 1962. Methods in C.A. Black et al. (eds.) Methodsof soil analysis. carbohydrate chemistry 1. Analysis and prepara- Agronomy 9,Amer. Soc. Agron., Madison, Wis. tionof sugars. AcademicPress, New York and London. 589 p. Peterson, R.G. and L.D. Calvin, 1965. Sampling. p. 54- 72. Zn C.A. Black et al. (eds.)Methods of soil Wilde,S.A. 1946. Forest soils andforest growth. analysis.Agronomy 9, Amer. Soc. Agron., Madi- Chronica Botanica, Waltham, Mass. William Daw- son, Wis. son & Sons, London.24 1 p. Pogrebnyak, P.S. 1930. Uber die Methodik von Standor- 1954. Humus form: its genetic classification. tuntersuchungen in Verbindung mit Waldtypen. Trans. Wis. Acad. Sci. 43: 137-163. Ver. I1 Int. Congr.Forstl. Versuchsanstalten, 1929, 1958 Forestsoils. Ronald Press, New York. Stockholm. p.455-47 1. 537 p. Pritchett,W.L. 1979. Propertiesand management of 1966. A new systematic terminology of forest forest soils. John Wiley and Sons, New York. 500 p. humus layers. Soil Sci. IO l(5): 403-407. Richards, B.N. 1974. Introduction to the soil ecosystem. 197 I. Foresthumus: its classificationon a Longman Group Ltd., London.266 p. genetic basis. Soil Sci. 3( 1): 1-12. 41 Appendices

Appendix I Methods of Describing Humus Forms

A horizon approach to the descriptionof humus forms In a mineral soil, the top of the first mineral horizon has been adopted. In making humus form examinations,has zero depth; in an organic soil the top of the first all distinguishablehorizons and layers are separately recognized horizon has zero depth. Thus, the depth of described. According to Soil Survey Staff (1975) “these organic horizons in mineral soils is measured upward descriptions need to be completely objective and clearly from zero depth, whereas in organic soils the depth is able ‘to stand on their own’, regardless of presumed measured downward from zero depth. Thickness mea- genesis ornomenclature. Nothing can substitute for surements are indicatedin terms of mean, minimum and them. The more laboratory data there areavailable for maximum thickness in centimetres. The proposed mini- collected samples, the more important the descriptions mum thickness for describing and sampling humus form become; without them, the laboratory data cannot be horizons is 0.5 cm. safely interpreted; if indeed, they arerelevant at all.” Boundaries are classified according to their distinc- The properties thatwill be described may not be found tions and form using followingthe scales (Table 1 and 2): in each horizon or layer and may not be used as tax- onomicdifferentiae. However, as in describing a soil TABLE 1. Boundary - Chses of Distinctness pedon, a complete descriptionof morphological properties for humus forms is recommended. Morphological Class Description properties are describedin the field using the nakedeye and a hand lens ( IOX to 20~).A binocular scopeis used Abrupt < 5mm for a more detailed examinationin the laboratory. Clear 5- 10mm Gradual 11-20mm In describing a humus form, one usually locates the Diffuse > ‘LO mm boundaries of the controlsection, decidesabout thelimits of the humus form profile, locates the boundaries be- TABLE 2. Boundary - Classes of Form tween horizons, and exam:ines the profileas a whole before naming andDescription describing the individual horizons. Class Sampling forphysical and chemical analysis of individual horizons, or horizon combinations (composite samples)is Smooth Nearlyplane a carried out as required. WavyPockets wider than deep The written description of individual horizons in the Irregular Pockets deeper than wide Broken Discontinuous,some parts are unconnected humus profile includes identification and listing of the following attributesin thissequence: horizondesignation and thickness, kind of materials, moisture status, colour, Moisture Status fabric, roots, non-conforming materials, biota, reaction, and boundaries. Reaction is determinedaccording to Some morphological propertiesof materials described mode of sampling. may be affected by their moisture content. Therefore,as Some aspects of thedescrirption are presented in detail in the description of thewhole pedon, the moisturestatus by the Working Group on :Soil Survey Data [Dumanski of horizons at the time of sampling(otherwise a transient (ed.) 19751 in the “CanSIS Manual for DescribingSoils in property) is indicated using thescale in Table 3. the Field”. The CanSIS Malnual is used to describe the properties of all mineral horizons and some propertiesof TABLE 3. Classes ofMoisture Status the 0 horizons. Since no terms or methods areavailable for describing the propertiesof the L, F and H horizons, this Appendix Description provides such a methodology. Class- DesiccatedExtremely dry condition;organic tissueswill crack or snap when broken or crushed Horizon Designation, Depth Dry Moisture is not apparent; materialwill not rub and Boundaries colour out on fingers MoistMoisture is apparent; colour will rub out on Once master horizonsin the humus form profile have fingers; if material is squeezed inhand, no water been identified, they have to’be subdividedin the manner will be observed (generallybelow field capacity) previously indicated in the text so that descriptions are Wet Ifmaterial issqueezed or rubbedin hand, water correctly recorded and the sampling of humus forms will be observed (generally above field capacity) proceeds in an organized fashion. Laboratory work may beneeded for positive identification of thekind of Saturated Water isobserved without squeezing or rubbing of material horizon. - 42

Colour TABLE 8. Classes ofChuracter - Continued The colour property of materialsis classified according Class Description to its hue, value and chroma, using the Munsell colour Gritty Refers toa rough tactility produced by mineral notations whenpossible. Rubbed field colours (according granules or coarse fragments to field moisture status at the timeof description) and dry Leafy Refers to the. tactility of materials producedby colours (following the sample preparation for analysis) deciduous foliage showinga shingle-like layer- are recorded. ing (banded structure) The colour selectionavailable fordescribing soils Mossy Refers tothe tactility produced by bryophytes might not besufficient for describing organic materials, with more or less preserved vegetative structures e.g. for brightred colour of decaying wood. And,due to Acerose Refers to thetactility produced by particles the prevailing grey hue, the colour of organic and min- having a tip, as the needlesof conifers eral materials within the humus form profile may be of less interpretive significance than that for mineral soil Felty Refers to the tactility produced by abundant horizons.However, colour isstill usedas an indirect fungal mycelia measure of characteristics or qualities which cannot be Fibrous Refers to tactility producedby an abundanceof easily or accurately observed. Colour is applied as one of fibrous plant residueswhich do not break down the differentiaeidentifying Ah and Hrhorizons. upon rubbing (ze. fine roots) Ligneous Refers to the tactility produced by coniferous or Consistence deciduous wood fibres Consistence is a measure of the strength and nature of Crusty Refers to a hard and brittletactility of dry or forcescombining materials together, which is deter- desiccated materials mined by the kind ofdeformation or rupture which occurs when pressureis applied and then released. Fabric l‘AB1.E 7. Con~istence- Chses of Consistence The terms “fabric” and “fabric analysis” havebeen ~~ ~~ used in studiesof soil and humus (Kubiena1953, Brewer Class Description .~ 1964, Babel 1975, Soil Survey Staff 1975, and Agricul- Loose There is no consistence of thematerial ture Canada1976). In this study, the term fabric has been applied to the description of structure, consistence and Friable A materialthat crumbles easily under gentle pressure character of organic materialsin the humus profile. The term“materials” refers here to plant residues and/or Firm A materialthat can be crushed under moderate organic finesubstances, with or without a minor mineral pressure; resistence is noticeable component. PliableMaterial is softand plastic ResilientMaterial that is springy or elastic and assumes Structure original state after forcesof deformation have Structure is classified according to the grade, type and been applied and released kind andsize, of the macromorphological aggregation of Tenacious’ Material is cohesive, not easily pulled apart the materialwithin a horizon or layer. The gradeis the degree of distinctions of arrangement ‘Degree of tenacity may be further described as weak, medium of what is observable in materials (Table4). or strong. TABLE 4. Structure - Classes of Grade Character There arecertain Description terms which have been found useful Class in describing thedistinctive quality (tactility) of materials ~~ in the humus formprofile. They arelisted and definedin WeakDisaggregated materials are dominant; < 20% Table 8 and may be used whereapplicable. Among them distinction of aggregation. areterms whichdescribe tactile qualities,particulate ModerateSome disaggregated material is found; 20 - 60% shapes, and other noteworthyqualities. Determining the distinction of aggregation character requiresa qualitative examination of thefabric. StrongAggregated materials aredominant; most materialconforms to thesame arrangement; TABLE 8. Classes ofCharacter >SO% distinction ofaggregation.

Class Description Class The type of structureis divided into four classes. The first indicates that there is no structure (random); the MushyMaterials are wet or saturated, soft andspongy second that the predominant structureis blocklike; the MuckyMaterials are usuallywet, smooth and sticky; third that it is platelike; and the fourth thatit is column- they contain silt andclay sized mineral particles like. The types are further classified according tokinds of GreasyMaterials are smoothand greasy when moistand structure (Table5, Figure 1). easily workable; fine mineral particlesare Blocklike structures are further classified in accord- usually absent ance with the scale in Table6. 43

Massive

STRUCTURELESS

Single particle

Blocky

BLOCKLIKE

Granular

Non-compact matted

PLATELJKE

Compact matted

Erect

COLUMNLIKE

Recumbent

Figure 1. Schematic illustratio'nsof classes of types and kindsof structure. 44

in the CanSIS Manual were modifiedto provide for more precise root description. Both classes are biased toward small-sized roots prevailing in the humus form profile. The reference unitarea surface is 2.5 X 2.5 cm square for Class ClassDescription Description fineand very fiqe roots and 25 X 25 cm squarefor ~ .~ medium, coarse and very coarse roots. Presently, all liv- Structureless No observableMassive A coherent mass aggregation showing no evi- ing and dead roots are to be counted due to the dif- dence of aggreg- ficulties involved in distinguishing the two. If roots are ation obviously dead, they may be excluded. Ifpossible, record the species or general type of plant (ie. tree, shrub,etc.) Single An incoherent particle mass of individual from which roots originate. particles (may he of various sites) TABLE 9. Roots - Classes ojA6undance with no aggregation Class NumberClass ofroots/unitsurface area Blocklike Materialsar- Blocky Faces rectangular ranged around few and flattened; Very < 3 a point bound- vertices sharply Few 3 - IO ed by flat or angular Common I 1-20 rounded sur- Plentiful 21 -30 f..aces Abundant > 3 0 Granular Spheroidal and characterized by rounded or sub- TABLE 10. Roots - Classes of Size rounded vertices

Platelike Materials ar- Non-compact Materials arrang- Class Size (diameter in mm) rangedhori- matted ed along horizon- zontally and tal planes with no Very fine 25 flat horizontal surfaces Compact Materials arrang- TABLE 1 1. Roots - Classes of Orientation matted ed along horizontal planes with ev- Class Description ident compaction Class Columnlike Materials ar- ErectMaterials in ver- RandomRoots are oriented in all directions ranged verti- tical position tical verti- ranged Oblique Roots are orientedalong oblique planes cally Horizontal Roots are oriented along horizontal planes RecumbentMaterials in re- VerticalRoots are oriented alongvertical planes cumbent (reclin-

ing)U' IDosition Non-Conforming Materials '1'AHL.E 6. Structure - Claws cf Sizfor Blocklike Agpegutes Some materials may not conform to most of the or- Class Description ganic materials comprising the humus form. They seem Fine < 5mm to persist for longer periodsof times asadmixtures to the Medium 5-2Omm materials in the horizons, or they may form a distinct c:oarse > 20 mm horizon in the humus form profile. "~ The mostcommonly encountered non-conforming materialsare charcoal, decaying wood andmineral Roots coarse fragments. Their description includes the kind of material, their distribution,size and abundance; butit is Roots are described by noting their abundance, size given only when they form an admixture to prevailing andorientation (Table 9, 10 and 11). Distribution of materials in horizons. roots, i.e. inped or exped, is described only for mineral Non-conforming materials are either distributed horizons. Since the modeof root patternin humus forms throughout (regular distribution) or distributed only in differs substantially from that in the rest of the pedon, certain parts ofthe horizon (irregular distribution). Thus the abundance andsize scales and the reference unit areaclassification according to the general kindof material is 45 followed by a description of the specific kind of distribu- TABLE 14. Non-Corforming Materials - Classes ofAbundance tion. Distribution and size of the non-conformingmaterials are describedare usingcommon scales (Table 12 and 13). Class Description FewOccasional and scattered pieces;volume < 5% TABL.E 12. Non-Cvnfomzngh4ateriah - Classes of Distribution (afterBrewer 1944.1 Common Frequent occurence; volume 5 - 20% Many Numerous, usuallycoarse pieces; volume >'LO%

Class Description Class Otherrelevant characteristics of non-conforming RandomMaterials are disl.ributedrandomly; there is no materialssuch as ColOur, degree Of decomposition,ori- recognizable,specific pattern of distribution gin, etc.may be recorded. Clustered Materials are diswibutedin clusters or groups Banded Materials are distributed in bands.sheets or layers Biota

The activity of soil floraand faunaplay such an import- TABLE 13. Non-Conforming Materials - Clusses of Szu' ant role in humus formation that their description cannot be overlooked. For the purposeof humus form description and taxonomy, the emphasis is placed on general Class Diameter (mm) Length (mm) qualitative and quantitative description. Very fine <2 <5 Soil Fauna Fine 2- 10 5 - 20 Medium 11-50 21 - 100 Soil fauna are those animals that "pass one or more Coarse 51 - 250 101 - 500 active stages wholly or largely in the soil or surface litter, Very coarse > 250 > 500 excluding thosespecies which occurthere only in passive 'The diameter measurements are used for rounded or sub- stages e.g. eggs, cysts or pupae(Richards 1974, Figure 2). rounded particles; the length measurementsare used for parti- The activity offauna in the soil has aprofound influence cles with distinctly uneven axes. on humus formation. Throughprocesses of burrowing, comminution and ingestion, soil fauna may participate Abundancerefers to the volumeoccupied by non- actively in decomposition, in synthesis of humus mate- conforming materials for each size class (Table 14) ex- rials and in the intermixing of humus and the mineral pressed as a percentage of the horizon volume. soil.

G H

1" 1" I

?cfL

Fzgure 2. Major kinds of animals foundin the soil. 46

Explanation of symbols in Figure 2: The following general types of droppings can berec- ognizedusing a hand lens or binocularscope (from A. Mites (Acarina) G. Woodlice (Isopoda) Hodgson 1978): B. Springtails(Collembola) H. Centipedesand millipedes C. Spiders (Areneida) (Myriapoda) i) Mite-type:usually formed by mites,Collembola, D. Fly larvae (Diptera) I. Termites (Isoptera) and Diptera larvae. Small (< 0.1 mm in diameter), E. Beetlesand larvae J. Earthworms(Lumbricida) discrete, spherical or oval, humified, rust to dark (Coleoptera) K. Potworms (Enchytraeida) brown, lacking mineral grains. F. Ants (Hymenoptera) L. Nematodes(Nematoda) ii) Enchytraeid-type: associated particularly with enchytraeid populations. Small (0.05 - 0.2 mm), dis- ‘l’heseclasses maybe further grouped into three broad classes crete, sub-spherical,rugose, generally well-humi- according to body size (Table15). fied,brown, but containing varying amounts of mineral grains andclay. iii) Arthropod-type: formed by larger arthropods and TABLE 15. Size Classes .f Soil Fauna (aferAmon 1977) smallsurface-feeding earthworms. Visible to the naked eye (1.0 - 3.0 mmlong), discrete, well- humified, dark brown, containing mineral grains Size Class Description Class Size but low in clay. Macrofauna Animals with a body size greater than 1 cm (in i v) Wormcasts: largely due to surface-castingearth- the longest dimension); includes earthworms, worms. Well-humified, generally brownor greyish vertebrates, molluscs and largearthropods brown, containing mineral grains andclay, spongy Mesofauna Animals with a body size in the range of 1 cm to or coarse rugose cast granular structure (5-10 mm 0.2 mm includes some mites and springtails, pot- in diameter). worms and most of the larger nematodes.The lower limit is about thelimit of viewing with a 10 X hand lens. Microfauna Organisms less than 0.2 mm in size; includes the protozoa as well as manyofthe smaller mites and nematodes

Faunal populations may be determined by direct observation or by indirect observation through the presence of droppingsor casts. a) direct observation - an estimate of the relative abundance of soil fauna observed in the humus formmay be made providing thatdis- criminations can be madein terms of the general kindsand sizeclasses describedpre- viously. The following classes of abundance may be used (Table16):

Figure 3. Droppings from the Hdal horizon of an Orthilepto- TABLE 16. Soil Fauna - Classes of Abundance moder.

Class Description Class Droppings may be described by their abundance and distribution according to thefollowing classes (Table 17 None No organismsobserved and Table 18). If possible, an indication of the average Few Organismsoccasionally observed, but only size of droppings should be recorded. scattered CommonOrganisms observed commonly Abundant Organismsobserved frequently throughout the TABLE 17. Droppings - Classes of Abundance profile. Class Description Class b) indirect observation - a good indication of the None visibleNo droppings activity of insects may be provided by their Few Droppingsoccasionally observed butonly excrement(“droppings” or “casts”) found scattered within the horizon.Droppings constitute a CommonDroppings commonly observed significant portion of many organic horizons and in some cases can form entire horizons Abundant Droppingsfrequently observed inrelatively (Figure 3). large numbers throughout the horizon 47

TABLE 18. Droppings - Classes ofDistinction (after Brewer 1964) Fungal mycelia are described by noting their abundance (Table 19), colour and distribution (Table20). The Class Description presenceor absence of mycorrhizal root tips is also recorded. Random Droppings are distributedrandomly, there isno recognizable pattern of distribution Clustered Droppings are distributedin clusters or groups TABLE 19. Fungal Mycelia - Classes $Abundance Banded Droppings are distributed in bands,sheets or layers Class Description Soil Flora NoneFungal mycelia visiblenot Soil flora includes bacteria, actinomycetes, algae and FewFungal mycelia occasionally present butonly scattered and not easily observed fungi. In routine studies, the descriptionof the soil flora is narrowed to the fungi that inhabit the humus form Common Fungalmycelia commonly observed profile. Abundant Fungalmycelia observed continuously through- The organisms referred to as fungi form a large and out the horizon, often “matting” materials to- varied group. Rusts, moulds,yeasts and mushroomsare a gether and creating a “felty” tactility few of the major kinds of fungi. Inmost cases, the presence of fungi can be detected by observing a mass of hyphae (thread-like filaments)called a mycelium. A fun- TABLE 20. Fungal Mycelia - Classes of Distribution (after Brewer gal mycelium constitutes th’e “vegetative” phase of the 1964) development of a fungus. While individual hyphae are generally toosmall Description to be seen, themycelial mass is usually Class visible. RandomFungal mycelia are randomlydistributed, there Some mycelia are easily irecognized by their colour, is no recognizable pattern ofdistribution while othersare transparent. Many are brown, black Clustered Fungalmycelia are distributed inclusters (dark grey), grey, white, red, yellow or blends of these or groups colours. In acid materialsand humid environments,mas- ses of fungal mycelia may form in the Fq horizon, pro- Banded Fungalmycelia are distributedin bands, sheets ducing a felty feel (tactility). or lavers 48

Appendix I1 Methods of Sampling and Analysis

Sample Collection As with other soil samples for analysis, the selection of drying. The importanceof dryingarises from the need to sampling methods for humus formsamples depends on minimize any biochemical transformations in the sample the objectivesof the study and on the analysesto be which will affect the constituent to be measured. Such undertaken. Details about sampling is given in several transformations are likely to be enhanced by moisture authoritative texts (Cline1944, Peterson and Caloin 1965). and elevated temperature since these conditions favour The long-term objective of the proposed humus form microbial and enzymatic activity.The longer these condi- classification is to provide characterizations of biological, tions persist, the greater will be the transformations so physical and chemical properties of the recognized taxa. the longer the period oftime between sampling and Thus, the humus formpopulation to be sampled should analysis, the more importantit becomes to adopt appro- be subdivided (stratified)horizontally into homogeneous priate sample handling procedures. Someanalyses, espe- sampling units corresponding totaxa. The sampling un- cially for more labile constituents, require either freeze- its are furthersubdivided vertically according to the rec- drying or analysis of moist samples immediately after ognized horizons constituting the humus form profile. sampling.For such constituents, both air-dryingand The intensity with which a particular humus form must oven-drying areunsatisfactory, as is prolonged storageat be sampled to estimate the desired characteristics with ambient temperatures in the moist state. If immediate givenaccuracy will dependon the magnitude of the analysis or freeze-drying are not feasible, storing in a variation within the humus form population under con- freezer is the next best alternative. While the analyses sideration. The purposeof sampling is to estimate these described in this report do not fall in this category, it is characteristics with an accuracy which will meet theobjec- recommended that soil pH should be measured as soon tive at thelowest possible costs. as possible after sampling since a somewhat lower pH is In the first phase of the ecological classification pro- commonly encountered in drier and/or stored samples. gramme, humus forms are sampled from sample plots It is also advisable to avoid prolonged storage of any subjectively chosen to represent various kinds of eco- moist samples and to avoid subjecting them to elevated systems whichare non-randomly distributed on the land-temperatures (e.g. by leaving them lying in the sun in scape. Sampleplots are approximately 500 m2 in size. At plastic bags). arepresentative locationwithin each plot thehumus For many commonanalyses ofsoil samples (organicor form is sampled alongwith the rest of the pedon.A result mineral), including those for total elemental content or of using this methodis that variations within and among exchangeablecation content, none of the drying sample plots cannotbe assessed. methods is likely to havevery significant effectson subse- Humus forms may be sampled either by individual quent analysis. However, some analyses (e.g. extractable horizons or by composite samples of ectorganic and en- sulphate) can be influenced by oven-drying (105”C), so dorganic horizons constituting the humus form profile. the normal (and most convenient) practice is to air-dry Savingscan be achieved both in the field and in the soil samplesas soon as possible aftersampling. The laboratory by collectingcomposite samples, providing results of all soil chemical analyses are conventionally that information on individual horizonsis not required. reported on an oven-dry(105°C) basis, regardless of the The procedure consists of cutting blocks about 10 X 10 moisture contentof the sample used for analysis.Thus, a cm (plan view) through ectorganic horizons. A similar separate air-dried sample has to be analyzed to deter- procedure can be applied to endorganic horizons,or they mine hygroscopic moisture content. may be sampled according to standard soil survey prac- The heterogeneity of soil materials, especially I. and F tices. Sincethe ultimate goalis the characterization of the horizon materials, requires the reductionof particle size entirehumus form rather than its parts,sampling to a low enough level to permit representative subsampl- natural cross-sections is, for most of the characteristics, ingfor individualanalysis so dried samplesmust be rational and also expedient. ground. This is particularly important when small subsamples (< Ig) are tobe used, as is commonly the case with Sample Preparation organic samples (e.g. fortotal C or total N). While various The purposes forwhich the analytical results are to be grinding toolscan be used (e.g. Wileymill for highly used, in addition to the natural variation in the samples, organic samples), samples shouldin all cases be ground to will determine how much care will be required in sample pass a2 mm sieve, and further groundto pass finer sieves preparation and how precise the analytical methods will (35, 60 or 100 mesh) when smaller subsamples are to be have to be. used. Finer grinding and bettermixing will improve the The two primary considerations in preparing humus precision of subsequent analysis but, at the same time, form samples for analysis are ‘drying’ and ‘grinding’. will increase the time needed for sample preparation.As There are fourbasic alternatives for dryingsoil samples, a general guideline, recommended mesh sizes are given namely: no-drying, air-drying, oven-drying and freeze- in Table 2 1. 49

TABLE 2 1. Recommended Mesh Sizes and horizons that are notflat may prevent widening the hole. The alternative is to take several smaller Sample size for analysis (g) - Mesh Size samples and bulk them together. 3. Forsloping horizons the flattened surface will not 15 10 (2 mm) be level but will conform to the desired sample. 1-5 35 (.5 mm) <1 60 (2.5 mm) After the sample has been removed, the hole is out- While the principlesdiscussed above apply toall mate- lined as closely as possible with thin plastic. Where cre- rials, different types of samples may call for different vices or pores are evident the outsideof the hole may first procedures. For example, in preparing foliage samples be lined with stiffer material such as tin or plastic sheet- for analysis, removing moisture andinhibiting enzymatic ing. Rounded sand orsmall glass beads are then poured activity as quickly as possiblie are overriding considera- into this hole to thelevel of the original flattened surface. tions. In this case, it is recommended that samples be If sloping horizons were sampled,all but the top partof dried rapidly (at70°C) in a forced-air oven and thatthey the surface must be covered with tin or plastic sheeting. be kept cold while being tramported fromfield the to the Sand or glass beads are poured in through the opening laboratory. However, even these procedures will be un- left at the top of thehole. Then, the thinplastic liner and satisfactory for morelabile plant constituents. its contents are removed and emptied into a 1000 ml (1 ml = 1 cm3) graduated cylinder. The volumeis recorded Bulk Density' both on the data form used for soil profile description Determining importantp.t-operties of soil, suchas pore and the label for the sample. The plastic bag with the space and nutrients on a quantitative basis requires a sample andlabel are carefully sealed (if the bagis < 4 mil knowledge of thesoil's bulk density and coarse fragment in thickness, it is enclosed inside another). content. Since the methods used for agriculturalsoils do Inthe laboratory the wet sample is weighed;the not work well in forest soils which have abundant coarse weight, minus bag(s) andlabel, is recorded. The sampleis fragments, a different methodbased on a techniquesug- then removed from theplastic bag and placed in a heat- gested by Gardner (1965, p. 95) is used. It consists of two proofcontainer (small paper bags areadequate) and separate steps: in the first, the bulk density of organic dried at 105°C until there is no longer any change in materials, mineral materials< 2 mm in diameter, and the weight. Usually 24 hours is a sufficient period of time. coarse fragment volumeof .all mineral materials L 2 mm Dry weight is then recorded. and 5 4 cm in diameter are determined; in the second, Mineral materials 22 mm in diameter (coarse frag- the coarse fragment volumeof all mineral materials > 4 ments)are separated from dried organic material by cm in diameter is determined. Thesecond stepwill not be hand while a 2 mm mesh sieve is used for mineral mate- required for those forestsoils with no coarse fragments. rials. As much fine material as possible is brushed from Bulk density and coarse fragment volume determina- the coarse fragments, which are then weighed. Their tions should be made for each horizon sampled for chem-volume is determined by measuring the amountof water ical analysis. However, whereseveral horizonsare similar they displace in a graduatedcylinder. in physical characteristics, one determinationof bulk de- The coarse fragment-free bulkdensity of a sample may nsity and coarse fragment volume froma representative be calculatedas follows: horizon (or several horizons if they are thin)will suffice. Specific details concerning sampling will be dealt with in 1) Db=(Md-M>2rnm)/(Vb-V? 2mm) the following sections. 1. Bulk Density and 2 mm to 4 cm Coarse Fragment Where: Volume Db = bulkdensity of mineralmaterials < 2 mm in diameter or of organic materials In this step 500 to 1000 cm3 of organic or mineral material should be sampled.A flattened surface20 cm in (g.cm-3) diameter is cleared at the top of the desired sample. In Md = mass of drysample (g) the centerof thissurface acircular holeapproximately 10 M 2 2 mm = mass of mineral materials 2 mm (g) cm in diameter is cut with a knife, pruning saw or pruning clippers to a depth of approximately8 cm. Materials Vb = volumeofhole sampled for bulk density from the hole are removedwith a small trowel or tables- determination (an3) poon and placed into a plastic sample bag. Some situa- V 2 2 mm = volumeof mineral materials 2 2 mm tionsthat may ariseand suggested solutions are as (cm3)); use volume of water displaced, or follows: approximate by the following equation: 1. If roots > 1 cm or stones >4 cm areencountered M L2mm/2.65(g.cm-3) another attempt should be made nearby to obtain Gravimetricmoisture content on a dry-mass basis that sample. In some soils or horizons, very high ( 6 dw) may be calculated as follows: contents of large roots or large coarse fragments will make sampling fo'r this step impractical. 2. When the material to be sampled is under 8 cm in depth, the hole might be widened to attain the desired volume. Large roots, large coarse fragments Where: Mw = massof wet sample(g) 'This section was prepared bly F.C. Nuszdorfer, Ministry of' Forests. Md = mass of drysample (g) 50

Gravimetric moisture content on a coarse fragment- Where: free basis ( 8 ) may also be calculatedas follows: V 1: 2 mm = volume of mineral materials 2 2 mm and 5 4 cm in diameter as determined in step 3) O=((Mw-M> 2mm)/(Md-M?2mm))-l I (cm3) Vb = volumeof hole sampled instep 1 (cm3) Where: Mw = mass of wet sample (g) Mg > 4 cm = mass of gravel >4 cm (g) M 2 2 mm = mass of mineral materials 2 2 mm (g) VPg = bulkvolume of soil from which the gravel > 4 cm was taken (cm3) Md = massof dry sample(g) 2.65 = approximate particledensity mineralof F0.r comparisons of moisture content between loca- materials (g.cm-3) tions, the figure for the coarse fragment-free basis (3 above) is more meaningful than thatbased on drymass (2 Cobble content on volume a basis (CFvolc) is calculated above). as follows: Water content on a bulk volume basis (evb) may be calculated as follows: 6) CFvoIc = Mc / Vpc(2.65)

4) t9 vb = (Mw - Md) / Vb (1.0) Where: Mc = masscobblesof (g) Where: VPC = bulkvolume of soil from which the cob- Mw = massof wet sample(g) bles were taken (cm3) Md = massof drysample (g) 2.65 = approximateparticle density mineralof materials (g.cm-3) Vb = volume of holesampled for bulk density determination (cm3) Stone content on a volumebasis (CFvols) is calculated as follows: 1 .o = approximate density of water (g.cm-3) This permits calculation of volume of water available 7) CFvols = Ms / Vps(2.65) for plant growthif the zone of supplyis defined. 2. Coarse Fragments > 4 cm Where symbols are as for equations5, and Ms = massstonesof (g) As a soil pit is excavated, rocks > 4 cmin diameter should be removed from thesoil and separated by hori- VPS = bulkvolume of soil from which thestones zon into gravel(< 7.5 cm), cobble (7.5 - 25 cm) and stone were taken (cm3) ( >25 cm) components. When horizons are thin indis- or 2.65 = approximate particledensity of mineral cernible, the separation may he by depth increments. materials (g.cm-3) After a decision has been made regarding the number The total coarse fragment content on a volume basis and location of samples to be taken for step1 (above), the (CFvol) is obtained by summing the results from equa- coarse fragments > 4 cm may be combined together to tions 5,6, and7: correspond to these samples.The mass of all components is determined with spring scales which have been cali- CFvol = CFvolg + CFvolc + CFvols bratedfor accuracy.Occasionally, cobbles and stones or, if the bulk volumes of soil from which the gravel >4 may occupya volume corresponding to more than a cm, cobbles, and stones were taken were equal, i.e. Vpg= singlesample from step 1. When this is the case, an Vpc = Vps, then, given Vpt = Vpg = Vpc = Vps: estimate of the proportions in the respective layers will have to be made. 8) CFvol=(V_>2mm/Vb)+((Mg>4cm+Mc+ Measurement of the dimensionsof the soil excavation Ms) / Vpt (2.65)) from which the coarse fragments were taken permits the volume tobe calculated. This is facilitated if the shapeof Where: the excavationapproximates a square or rectangular V 2 2 mm = volume of mineral materials 2 2 mm and box. 5 4 cm in diameter (cm3) Where there is a high content of evenly distributed gravel > 4 cm and cobbles, it will be sufficient to sample Vb = volumeof hole sampled in step 1 (cm3) only a portionof the total volume ofthe soil pit. A section Mg > 4 cm = mass of gravel > 4 cm (g) of predeterminedthickness couldbe sliced from aface of Mc = mass of cobbles (g) an established soil pit and used to determine gravel and cobble content.The entire pit must be used to determine Ms = massstonesof (g) stones content. 2.65 = approximate particledensity of mineral Gravel content on volumea basis (CFvolg) is calculated materials (g.cm-3) as follows: Total porosity in organic materials (Sto) is the percentage oftotal volume not occupied by solids: 5) CFvolg = (V 22mm / Vb) + (Mg >4 cm / Vpg (2.65)) 9) St0 = 100( 1 - CFvol) (( 1 - (Db / 1.5)) 51

Where: continue to collect information on a, number of para- CFvol = coarsefragment content ona volume metersthat can not as yet be interpreted with any

basis confidence. I. The methods recommended below are based on the Db = bulkdensity (inthis case, organicof materials) (g.cm-3) current understandingof relationships between properties of humus form horizons, and both productivity and 1.5 = approximate particledensity organicof humus form taxa. In particular, recent studies in the materials (g.cm-3) Coastal Western HemlockBiogeoclimatic Zone of British Total por'osity in mineral materials (Stm) is calculated Columbia have generated a numberof useful hypotheses as follows: with regardto these relationships (Lowe and Klinka I98 1). The specificmethods outlined were selected 10) Stnl = 100 (1 - CFvol) (( 1- (Db / 2.65)) eitheron the basisof common usein routine soil characterization, or demonstratedsignificance in differ- Where symbols are as for equation9 (above) and: entiating between humus forms (in the CWH Zone), in combination with relative speed and simplicity of labora- Db = bulkdensity (inthiscase, mineral of materials < 2 mm indiameter) (g.cmV3) tory procedures. For discrimination purposes, thefollowing analyseson 2.65 = approximate particledensity mineralof humus form' samples are presently considered the most materials (g.cm-3) promising: The quantity of nutrients available for plant growthis 1. Organic fractionanalysis. indexed as follows: a. lipid fraction b. carbon and bound sugars in solublepolysaccharide 1 1) kg :sugar content of clear to which category some common analyses belong. Nor isit clertain whichof many possible analyses will 'A humus form sample may include a sample of endorganic prove most valuable for diagnostic or interpretive pur- horizons which should be treated as a different entity in collec- poses. Accordingly, the authors considerit important to tion and analysis. 52 fraction B is determined by the phenol-sulphuric acid metric or steam distillation methods (see CEC below). procedure(Whistler and Wolfram 1962), following The C/N ratio is calculated from C and N values. hydrolysis with IN HySO4. Nitrogen contents of fractions H 1 and F 1 are determined by semimicrokjedahl, Mineralizable nitrogen: Is determined by the anaerobic and designatedNH I and NFI. The fulvic acid fraction is incubation method of Waring and Bremner (1964). Ke- f'urther fractionated on polyvinylpyrrolidone to separate leased ammonium is determined colorimetrically using the polyphenolicmoiety (termed fraction FA) of this the same methods describedas fortotal nitrogen. f'raction (Lowe 1975). Cation exchange capacity (CECmeq/ 100 gm): l'he Details of the recommended analysis concerning or- neutral IN ammonium acetate procedure (NHqOAc,pH ganic fraction analyses are given by Lowe ( 1974) and 7.0) (Chapman 1965) usingsteam distillation-titration Lowe and Klinka (198 I). Itshould, however, be em- (kjeldahl)or the colorimetric phenol hypochlorite re- phasizedthat as moreinformation becomesavailable, action(autoanalyser or manual) for determination of substantial revisions in these recommendations may be- NH4-N displaced. come necessary. There is some doubt as to whether this widely used procedure is the best for organic samples. Certainly it 2. Routine Analysis cannot be expected to give a reliable estimate of' CEC Reaction (pH): Determined electrometrically in 1 :8 sus- under field conditions in strongly acidic soils,due to the pensions in distilled water and in 0.0 1 M CaCIy (Peech pH-dependence of charge on organic colloids. Alterna- 1965) for organic samples.For mineral horizon samples, tive approaches using unbufferedsalts or 'summation of a soil: solution ratio of I:2 (mass:volume) us suggested, cations' are discussed by Chapman (196.5). More work is although I : 1 is more commonly used for pH determina- needed onthis problem. tion in water. Exchangeable base cations (ExCa, ExMg, ExK, ExNa Totalcarbon ((2%): By inductionfurnace and carbon meq/ 100 gm): Displacement with neutral 1 N ammonium analyser(Leco and other equivalent equipment). It acetate (first stage of CEC analyses above) and cation should be noted that some interpretation problems exist determination by atomic absorption analysis. Care must for samples containing charcoal or free CaCO3. be taken to circumvent the common problemsof matrix Total nitrogen (NT): By semi-microkjeldahl (Bremner and interference effects and reagent blanks. Nitrous ex- 1965) digestion and NH4-N determination by colori- ode flameis preferable forCa and Mg.

SAMPLE 1 Extract with ethanol: benzene (1 :1) RESiDUE I FRACTION A 1 Extract with 0.1N H2SO4 RESIDUE I FRACTION B I Extract with0.1 N NaOH-cold RESIDUE ALKALINE EXTRACT I Acidify to pH 1.5 I 1 H2SO4with I Precipitate - Supernatant - HUMIC ACID(Hl) I ACID FULVIC (Fl)

I Redissolve NaOHabsorbed Absorbed Not FRACTIONF1 C FRACTIONF1 A

Fipw 3. Separation of' organic fractions fr-om humus form samples. 53

Pyrophosphate-extractableFe and Al: Extraction of Fe TABLE 22. Recommended Chemical Analysis and A 1 with sodium pyrophosphate at pH 10 and 25"C, following the procedureof Balscomb (1968). Fe and A1 are determined by atomic absorption spectroscopy. Recommended analysis Extractable phosphorus: In mineral horizon samples is pH (CaC12)' determined by the Braymethod of acid ammonium Total C' fluorideextraction as described by Olsenand Dean Total and mineralizable N' (1965) followed by colorimetricdetermination of the P using the nlolybdenum blue method. Cation exchange capacity and exchangeable cations' Extractable sulphate-sulphur: In mineral horizon sam- Lipid fraction" ples is determined by ammoniumacetate extraction Carbon and bound sugarsin fraction R2, ' (Bardsley and Lancaster 1965). Extracted sulphate is re- duced to sulphideby HI and :sulphide is then determined Carbon and nitrogen in humic acid extract2!' co1orimetric;dly (Kowalenko and Lowe 1972). Carbon and polyphenol carbonin fultic acid extract" Total Ca, Mg, K, Fe, Al, Na, Mn and P are determined Optical properties(E3 and E4/E6) of following wet oxidation with Caro's acid (H2SO4 + humic acid extract" '' H202). using a modification of the method of Parkinson Total Ca, Mg, K, Na, Fe, AI, Mn and P.' and Allen (1975). P in the (digest is determined colori- metricallywith themetavanadate procedure, and Ca, Pyrophosphate-extractable Fe and AI' Mg, K, Fe, AI, Na andMn by atomic absorptionanalysis. Extractable-P' Nitrogen canalso be determined on thesedigits. Extractable-S4 A summary of recommended chemical analyses for humus form studiesis given in Table22. Determination 'All samples of the measurements recommendedbelow will also allow 'Samples of ectorganic horizons calculation of theadditional derived variables:ExCa/ 3San~plesof' endorganic horizons ExMg, ExCa/ExK, and others. 'Samples of A & B mineral horizons 54

Appendix I11 Sample of the Form Used In Humus Form Description

I w -" t-"