Classification of forest humus forms: a French proposal

Jean-François Ponge

Description

In: Annales des Sciences Forestières, 1995, 52 (6), pp.535-546. A 2-way classification grid and a nomenclature are proposed for French forest humus forms but which could include mountain, Mediterranean and tropical forms as well. This proposal takes into account our present knowledge of biological mechanisms that take place in plant litter decomposition, transformation of soil organic matter, linkage of the latter to mineral particles and building of the structure in the A horizon. Basically, by adjoining free qualifiers, humus forms may be defined by accounting also for their chemical and physical particularities.

Sujets

• Humus
• Classification
• Decomposition
• Litter
• Soil biology

Informations

• Publié par: ponge
• Publié le: 16 octobre 2017
• Nombre de lectures: 3
• Langue: English
• Poids de l'ouvrage: 1 Mo

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article
Original

Classificationofforesthumusforms:
aFrench
proposal

ABrethes

JJ Brun

BJabiol

J Ponge

FToutain

citéadministrative
1
desrecherchestechniques,Coligny,
ONF,département
ruedu45042Orléanscedex;
131,Faubourg-Bannier,
2
CEMAGREF,
la
domaineuniversitaire,2,ruedePapeterie,
BP76,38402Saint-Martin-d’Hèrescedex;
3
54042
ENGREF,
14,rueGirardet,Nancycedex;
4
labor
Muséumnaturelld’écologiegénéra
nationald’histoiree,atoirele,
1800
4,avenueduPetit-Château,9Brunoy;
5
ru
centredeue,BP5,1 7,eNotre-Dame-des-Pauvres,
CNRS,pédologiebiologiq
France
54501Vandceuvrecedex,

218March
1994;
(ReceivedJanuaryaccepted1995)

forFrenchforest
classificationandanomenclaturearehumusforms
Summary —A2-waygridproposed
stakesinto

butwhichcouldn,tropical
includemountaiMediterraneanandformsaswell.Thiproposal
inlitter
thattake
accountourofmechanismsplant
presentknowledgebiologicalplacedecomposi-
sformationofsoilmatteofthelattertomineralandofthe
tion,tranorganicr,linkageparticlesbuilding
horifreehumusform

structureintheAzon.Bassbedefinedby
ically,byadjoiningqualifiers,may
alsofortheirchemicaland
es.
accountingphysicalparticulariti

humusform/ forest/ classification/ nomenclaturebiology
/ soil

Résumé —Laclassificationdes formesd’humusforestières :Unegrille
propositionfrançaise.
tréesetnomntleshumusrs
forestie
declassificationà2enuneenclaturesoproposéespourdeFrance,

maisaussiauxformesd’altitudproposi-
e,etméditerranéennes.Cette
pouvants’appliquertropicales
intervenant
tionenlesconnaissancesactuellesconcernantlesogiques
prendcomptephénomènesbiol
dansdécomdelalitière,latransformationdelamatièresesliensavecles
la
positionorganique,par-
etlastructurationl’horizonA.Parsonà
sminéralesdeprincipemême,grâcel’adjonctde
ticuleion
lesformesd’humusêtreàleurscaractères
dontlechoixestlibre,peuventpréciséesquant
qualificatifs
chimiquesouspa
physiquerticuliers.

dusol
formed’humus/forêt/ classification/ nomenclature / biologie

*
author
Corresponding

INTRODUCTION

Thehumus
isofdifferent
profilecomprised
scaleswhichbe
mayintegrated:regional
soil
climate,k,
parentrocvegetation,organ-
ismsb;Bemier and
(Toutain,1987a,Ponge,
for
disHumusmsareu
1993).nevenly
the
tributedoverwoforclimaticandhis-
rld,
toricalreasons.Asavarious
consequence,
classificationshavebeeninuseuntil
now,
eachfocusedon
regionalaspects.
Indescribed
Kubiëna
Europe,(1953)
numerousawide
humusforms,covering
ofrocksand
rangeclimates,parentvege-
tationHiscriteriawerederived
types.mainly
fromhisownobservations.
morphological
DuchaufourandBabellater
(1956)(1971)
differentchemicaland
investigated
microstructuralascientific
aspects,giving
basisformorerefinedclassifications.Dele-
courthenanidentification
(1980)proposed
formosthumusformswest-
in
keypresent
ern
Europe.
InNorththeneedforanother
America,
ofclassificationwas
typeemphasizedby
Wildeadetailed
(1954,1971).Morerecently,
ofhumusformswasachieved
taxonomyby
KlinkaandGreen1993).
et al (1981)et al (
Inoftheothers
otheregionsworld,
r
endeavouredtodescribeand
tropical
Mediterraneansoilsonthesamebasis

(Marin1985;Ferry,1992;Leroy
et al,et al,
1993).
inthescientificof
Progressknowledge
theinchemicaland
soil,both
its
biological
nowallowsustoafunc-
aspects,propose
tionalclassificationofforesthumusforms.A
worldwidetoolneededtoenablesoilsci-
is
entistsandforesterstodescribekind
every
ofhumusForthat
existingprofile.purpose,
weaclassificationwhichisnottax-
propose
onomical.Rather,aimsanswerthe
to
it
ofwtosee
questionho when
processes
thesoilwiththenakedand
observingeye
usethistohumusforms
knowledgeidentify
withmore
certainty.
Theclassificationisbasedon
proposed
thesameastheFrenchPedo-
principles
logicalReferenceBasefors
oil
types(AFES,
Thisisareferenceandnota
1992).system
hierarchicalandexhaustiveclassification.
Humusformsaredescribedbylinkingthem
tosomewell-definedreferenceformsand
asas
freelyadjoiningmanyqualifiers
needed.Aneffortwasmadetomakethis
classificationscientificand
pragmatic,pre-
flexible.
cise,but,nevertheless,

soilsand
Waterlogged(gleypseudo-gley)
andtheirhumusforms
will
(AFES,1992)
notbediscussedhere,asabetterknowl-
of
edgebiologicalmechanismspoor
in
ly
aeratedhorizonsisneeded.

STUDIESONFUNCTIONALASPECTS

Transformationof leaf litter

Recentstudiesthe
emphasizedimportance
ofeof
thechemicalnaturplantmacro-
moleculesinthefateofhumusIn
layers.
earlierobservations
particular,followingby
Handley(1954),Reisingeret al (1978),
and
Toutain(1981 )Françoiset al (1986)
describedthefollowedtannin-
pathwayby
foodwebs
soil
proteincomplexesthrough
indifferenthumusSeveralcritical
types.
wereatfirstthesenes-
phasesrecognized,
cenceoftreewithof
foliage,appearance
stabledarkwherewas
pigmentsnitrogen
70%
oftotalin
sequestered(egnitrogen
beechunavailablefor
foliage),rending
it
nutrition
plant(Toutain,1981).Investiga-
tionsondifferentscalesleaf
(soilslides,
trastructure,etc)showedthat
ul oafew
nly
biota,suchasearthwormsandwhite-rot
abletosuch
fungiweredisintegrate
(fig1),
recalcitrantmolecular
assemblages
these
(Toutain,1981).Whenorganisms
wereandthe
presentactive,disappearance
ofleafwasWhen
litter
rapid(mullhumus).
werelitterdis-
theyabsent,however,slowly
theofsmallani-
appearedthroughactivity
suchasand
mals,microarthropodsenchy-
traeidworms
(moderhumus).
thereisathresholdfornutrient
Thus,
thatnotbea
y
cyclesmay ormalockup,
ontheorbsenceof
a
dependingpresence
efficientTheir
organisms.presencedepends
onenvironmentalandhis-
(Toutain,1987a)
toricalconditionsthatleadtoaof
variety
functionalHereistheborderline
types(fig2).
betweenmullandmoder.moderhumus
In
iseffectivebutsoil
forms,biologicalactivity
foodchainsareTherinc
discontinuous.
p
ivisibletothenakedisthe
palactivity,eye,
transformationofalfae-
litterintoanim
plant
ceswherealotofmatterremains
organic
atleast
977;
untouched,temporarily(Webb,1
Toutain
et al,
onge,
1982;P1991 a,b).

Theborderlinebetweenmoderandmor
humusformsmoredetermine,
isdifficultto
andmoreon
knowledgebiologicalpro-
cessesisneededbeforecleartrendscan
beOurownobservationsindi-
perceived.
catedtha
twormswerepartic-
enchytraeid
abundantmorhumusforms
in
ularly(Bernier
et al,1993;thus,
Ponge,unpublisheddata);
theirdominancecouldbemorethanan
exclusionoftheotherthe
groups;however,
truemechanismsareunknown.

ofmatter
Assemblageorganic
withmineral
particles

Thechemicalnatureofmatterand
organic
intheA
itswithmineralmatter
assemblage
horizonontheaforementioned
dependpro-
cesses.We3main

aydistinguishpathm
et al,,
ways(Berthelin1994;Duchaufour
1995):
-
BiomacrostructuredAhorizon:
Clay-min-
eralbe
complexesmaycementingmacroag-
duetotheofsoil-
gregates,mixingactivity
earthwormsand
dwelling(BernierPonge,
1994);
-
"Insolubilisation"Ahorizon:Soluble
metabolicofwhite-rot
productsfungimay
on
precipitateclay-ironparticles;
-
horizon:Inherited
"Juxtaposition" Aorganic
mattermadeofcellwallsrec-
plant-fungal
transmission
in
ognizable(Toutain,1981)
oreven1991
lightmicroscopy(Ponge,a,b)
beinfaecalof
maypresentpelletsmany
smallanimals
(litter-dwellingearthworms,
sidesidewith
arthropods,enchytraeids),by
mineral
grains.

BASESFORANEWCLASSIFICATION
INTEGRATINGMORPHOLOGICAL
ANDFUNCTIONALFEATURES

Theexistenceofaclose
relationship
between and
morphologybiochemistry

hasbeenoften
(Duchaufour,1995)ques-
tioned.Thesamehumuswitha
typehigh
humusfromamor-
biologicalactivity(mull
ofwellcorre-
may
phologicalpointview)
toawideofvaluesand
spondrangepH
indicator
plantspecies(Duchaufour,1995).
different
Conversely,morphologicaltypes
havethesameorC/N.
maypH
Giventhesewiththecur-
discrepancies
rentviewthatofthehumus
morphology
isthereflectionofitschemical
profileprop-
erties,weusethelattequal-
decidedtoras
ifiersforbasedonmor-
groupsprimarily
th