Soil and environmental science dictionary

Angers for the CANADIAN SOCIETY OF SOIL SCIENCE CANADIAN SOCIETY OF SOIL SCIENCE and Environmental Science DICTIONARY CRC PR E S S Boca Raton London New York Washington, D.C... Canadian

Edited by

E.G Gregorich L.W Turchenek M.R Carter D.A Angers

for the CANADIAN SOCIETY OF SOIL SCIENCE

CANADIAN SOCIETY OF SOIL SCIENCE

and

Environmental

Science DICTIONARY

CRC PR E S S

Boca Raton London New York Washington, D.C

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Library of Congress Cataloging-in-Publication Data

Soil and environmental science dictionary / edited by E.G Gregorich [et al.].

Gregorich, E.G II Canadian Society of Soil Science.

S592 S59 2001

CIP

Don't be surprised we don't know how to describe the world and only speak to things affectionately by their Þrst names.

Zbigniew Herbert

Never About You

Judicious treatment of environmental questions and challenges requires an integrated, disciplinary approach Whether working at a local, national, regional, or global scale, the knowl-edge and expertise resident in a variety of subject areas comes to bear on all questions ofsustainable development Soil scientists now collaborate with colleagues in many Þelds, and abasic working knowledge of the vocabulary of those Þelds improves understanding and enhancesthe ßow of information

cross-This dictionary brings together the conventional vocabulary of soil science with that of manyoverlapping disciplines such as geology, hydrology, and meteorology Its purpose is to deÞneand describe technical words for researchers, students of various levels, librarians, policy- anddecision-makers, and interested citizens working and studying in a wide variety of disciplinesrelated to soil science

The terms and deÞnitions for this dictionary were gathered from a wide variety of sources,including several existing glossaries and dictionaries The editors invited a panel of thirty reviewers,experts in selected subject areas, to help review, select, and update best deÞnitions The editorsacknowledge and thank Professor Alma Mary Anderson, Art Department, Indiana State University,for drafting the illustrations To reßect Canada’s bilingualism and make the dictionary more useful

to the international science community, French equivalents are given for English terms

Canadian Society of Soil Science

The Canadian Society of Soil Science is a non-governmental, non-proÞt organization for scientists,engineers, technologists, administrators, students, and others interested in soil science Its threemain objectives are:

• To promote the wise use of soil for the beneÞt of society

• To facilitate the exchange of information and technology among people and organizationsinvolved in soil science

• To promote research and practical application of Þndings in soil science

The Society quarterly produces the international scientiÞc publication, the Canadian Journal

of Soil Science, and each year hosts an international soil science conference Its well-known practicalsoils methodology book Soil Sampling and Methods of Analysis (Lewis Publishers, CRC Press,1993) is used throughout the world The Society publishes a newsletter to share information andideas, and maintains active liaisons and partnerships with other soil science societies Collaborativeprojects are currently under way in Sri Lanka, Costa Rica, and Thailand

For more information about the Canadian Society of Soil Science, please visit the followingWeb site:http://www.csss.ca

The Editors

Saskatchewan, and earned a Ph.D in soil science from the University of Guelph He has been aresearch scientist with Agriculture and Agri-Food Canada at the Eastern Cereal and OilseedResearch Centre, Ottawa, Canada, since 1989, focusing on carbon and nitrogen cycling in soil He

is a member of the Canadian Society of Soil Science and currently serves as an associate editorfor the Journal of Environmental Quality.

Saskatchewan, and earned a Ph.D in soil science from the Waite Agricultural Research Institute,University of Adelaide He held research positions at the University of Alberta and the AlbertaResearch Council from 1975 to 1994, and is currently a senior soil scientist with AMEC Earth andEnvironmental Ltd in Edmonton, Alberta He is a member of the Canadian Society of Soil Scienceand has been involved in research and consulting in environmental soil science, reclamation, andsoil survey

M.R Carter, Ph.D. holds degrees in agriculture and soil science from the University of Alberta,and earned a Ph.D in soil science from the University of Saskatchewan He has held agriculturalresearch positions with Agriculture and Agri-Food Canada since 1977 and is currently a researchscientist at the Crops and Livestock Research Centre, Charlottetown, Prince Edward Island, working

on soil quality evaluation A fellow of the Canadian Society of Soil Science, he currently serves

as editor-in-chief for Soil and Tillage Research and Agriculture Ecosystems and Environment.

and the University of Guelph, and earned a Ph.D in soil science from McGill University He hasbeen a research scientist with Agriculture and Agri-Food Canada since 1988 at the Soils and CropsResearch and Development Centre, Sainte-Foy, Québec, involved in research in applied soil physicsand organic matter dynamics He is an adjunct professor of soil science at Université Laval andserves on the Canadian Society of Soil Science council, and is an editorial advisor for Soil and Tillage Research and Plant and Soil.

Table of Contents

Using the Dictionary xvii

Dictionary (A–Z: English Terms and DeÞnitions with Equivalent French Terms) 1

English/French Index of Terms by Subject Area/Discipline 409

French/English Index of Terms by Subject Area/Discipline 481

References: Sources of Terms 555

References: Sources of Illustrations 559

Appendix A Units Table A.1 SI PreÞxes 561

Table A.2 SI Base Units 561

Table A.3 Conversion Factors for SI and Non-SI Units 562

Appendix B Soil Properties Table B.1 Types and Classes of Soil Structure 565

Figure B.1 Type, Kinds and Classes of Soil Structure 566

Figure B.2 Soil Texture Classes 566

Appendix C Geological Timescale Table C.1 The Geological Timescale 567

Appendix D Soil ClassiÞcation Table D.1 Canadian Soil ClassiÞcation at Levels of Order, Great Group, and Subgroup 569

Table D.2 Correlation of Horizon DeÞnitions and Designations 574

Table D.3 Correlation of United States and FAO Diagnostic Horizons with Nearest Canadian Equivalents 575

Table D.4 Taxonomic Correlation at the Canadian Order and Great Group Levels 576

Appendix E Ecozones of Canada Figure E.1 Terrestrial Ecozones of Canada 577

Using the Dictionary

Each term is printed in bold type, followed by the deÞnition In the case of multiple deÞnitions for

a single term, deÞnitions are listed in a numbered sequence Where a deÞnition pertains to a speciÞcdiscipline, the discipline appears italicized in parentheses at the head of that deÞnition

The French term equivalent to the deÞned English term or phrase is shown in bold type followingthe deÞnition If the French term differs for multiple English deÞnitions listed in a numberedsequence, the French terms are numbered correspondingly at the end of the list of deÞnitions

A word in italic font within a deÞnition indicates that it is deÞned elsewhere in the dictionary,unless it denotes a biological genus and species Where a term is deÞned elsewhere in thedictionary under a synonymous term, the reader is directed to this other deÞnition with theinstruction, “See ” At the end of a deÞnition, the reader is alerted to synonyms for this termwith the instruction, “Also called ”

Two indexes, located at the back of the dictionary, group dictionary terms according to disciplineand subject area These sections enable the English or French reader to determine if a particularterm, or group of related terms within a discipline, is deÞned in the dictionary Terms are arrangedalphabetically within each discipline The English/French index is sorted alphabetically by Englishterm with the corresponding French equivalent, and the French/English index by French term withthe corresponding English equivalent Several appendices provide additional information to aid inunderstanding certain terms or the context in which terms are used The literature used to deÞnesome of the terms is cited in References: Sources of Terms, and the sources used for some of theillustrations are given in References: Sources of Illustrations

OF TERMS BY SUBJECT AREA/DISCIPLINE 409AGRONOMY, AGRICULTURE, FERTILITY, PLANT NUTRITION 409BIOCHEMISTRY 411

BOTANY, HORTICULTURE, RANGE SCIENCE 412CHEMISTRY 417

CONSERVATION, SOIL MANAGEMENT, TILLAGE 424ECOLOGY 429

ENVIRONMENTAL SOIL SCIENCE, AGRICHEMICALS, PESTICIDES, POLLUTANTS 433

FORESTRY 434GEOMORPHOLOGY, GEOLOGY, CIVIL ENGINEERING 437HYDROLOGY, LIMNOLOGY, WATER QUALITY 445

IRRIGATION 448METEOROLOGY, CLIMATOLOGY, AIR QUALITY 449MICROBIOLOGY 451

MINERALOGY, GEOCHEMISTRY, WEATHERING 454MODELING, STATISTICS 457

PEAT, PEATLANDS 461PHYSICS, SOIL WATER 462RECLAMATION, REMEDIATION 467

SOIL GENESIS, PEDOLOGY, AND CLASSIFICATION 468SOIL INORGANIC/ORGANIC CHEMISTRY, SALINITY 473SOIL STRUCTURE, MICROMORPHOLOGY 475

SOIL SURVEY, REMOTE SENSING, LAND USE INTERPRETATION 476WASTE MANAGEMENT, COMPOSTING 478

ZOOLOGY 479FRENCH/ENGLISH INDEX

OF TERMS BY SUBJECT AREA/DISCIPLINE 481AGRONOMIE, AGRICULTURE, FERTILITÉ DES SOLS, NUTRITION DES PLANTES (AGRONOMY, AGRICULTURE, FERTILITY, PLANT NUTRITION) 481

BIOCHIMIE (BIOCHEMISTRY) 483BOTANIQUE, HORTICULTURE, PHYTOGÉOGRAPHIE(BOTANY, HORTICULTURE, RANGE SCIENCE) 485CHIMIE (CHEMISTRY) 490

CONSERVATION, GESTION DES SOLS, LABOURAGE(CONSERVATION, SOIL MANAGEMENT, TILLAGE) 499ÉCOLOGIE (ECOLOGY) 504

SCIENCES DU SOL ET DE L’ENVIRONNEMENT, PRODUITS AGRICHIMIQUES, PESTICIDES, MATIÈRE POLLUANTE

(ENVIRONMENTAL SOIL SCIENCE, AGRICHEMICALS, PESTICIDES, POLLUTANTS) 509

FORESTERIE (FORESTRY) 511GÉOMORPHOLOGIE, GÉOLOGIE, GÉNIE CIVIL(GEOMORPHOLOGY, GEOLOGY, CIVIL ENGINEERING) 514HYDROLOGIE, LIMNOLOGIE, QUALITÉ DE L’EAU

(HYDROLOGY, LIMNOLOGY, WATER QUALITY) 524IRRIGATION (IRRIGATION) 527

MÉTÉROLOGIE, CLIMATOLOGIE, QUALITÉ D’AIR(METEOROLOGY, CLIMATOLOGY, AIR QUALITY) 528MICROBIOLOGIE (MICROBIOLOGY) 531

MINÉRALOGIE, GÉOCHIMIE, ALTÉRATION MÉTÉRORIQUE(MINERALOGY, GEOCHEMISTRY, WEATHERING) 534MODÉLISATION, STATISTIQUES

(MODELING, STATISTICS) 538TOURBE, MILIEU TOURBEUX(PEAT, PEATLANDS) 542PHYSIQUE DU SOL, EAU DU SOL(PHYSICS, SOIL WATER) 544RESTAURATION DES TERRES, MESURES CORRECTIVES(RECLAMATION, REMEDIATION) 549

PÉDOGÈNESE, PÉDOLOGIE, ET CLASSIFICATION DES SOLS(SOIL GENESIS, PEDOLOGY, AND CLASSIFICATION) 551CHIMIE MINÉRALE/ORGANIQUE DU SOLS, SALINITÉ (SOIL INORGANIC/ORGANIC CHEMISTRY, SALINITY) 557STRUCTURE DES SOLS, MICROMORPHOLOGIE

(SOIL STRUCTURE, MICROMORPHOLOGY) 560PROSPECTION DES SOLS, TÉLÉDETECTION, INTERPRÉTATION DES DONÉES PÉDOLOGIQUES (SOIL SURVEY, REMOTE SENSING, LAND USE

INTERPRETATION) 561GESTION DES DÉCHETS, COMPOSTAGE

(WASTE MANAGEMENT, COMPOSTING) 562ZOOLOGIE (ZOOLOGY) 565

References:

Sources of Terms 567References:

Sources of Illustrations 571Units 573

Table 1 573

SI Prefixes 573 Table 2 573

SI base units 573 Table 3 574 Conversion Factors for SI and non-SI Units (Soil Science Society of America , 1997) 574

Soil Properties 577

Table 1 577 Types and classes of soil structure 577

geological timescale 581

Table C.1 581 The Geological Time Scale and Major Geological and Biological Events 581 Table D.1 583

Soil Classification at Levels of Order, Great Group, and Subgroup 583 Table D.2 588

Correlation of Horizon Definitions and Designations 588 Table D.3 589

Correlation of United States and FAO Diagnostic Horizons with Nearest Canadian Equivalents 589

Table D.4 590 Taxonomic Correlation at the Canadian Order and Great Group Levelsl 590

591Ecozones of Canada 593

A

A

which an amino group and an alkylgroup are attached to the carbonatom residing closest to the carboxylgroup acide aaaa-aminé

a axis (crystallography) One of the lographic axes used as reference incrystal description It is the axis that

crystal-is oriented horizontally, from front torear See b axis, c axis axe a

at or near the surface in the zone ofremoval of materials in solution and

accumulation of organic carbon, orboth The accumulated organic mat-ter is usually expressed morphologi-cally by a darkening of the surfacesoil (Ah) Conversely, the removal oforganic matter is usually expressed

by a lightening of the soil color, ally in the upper part of the solum(Ae) The removal of clay from theupper part of the solum (Ae) isexpressed by a coarser soil texture ascompared to the underlying subsoillayers The removal of iron is indi-cated usually by a paler or less redcolor in the upper part of the solum(Ae) relative to the lower part of thesubsoil The above horizon terms areaccording to the Canadian system ofsoil classiÞcation See Appendix D

usu-for equivalent U.S Soil Taxonomyand FAO soils terminology See B

horizon A

hori-zon showing properties of both an Aand B horizon in which properties ofthe A predominate. horizon AB

stem of a plant (e.g., the undersurface

of a leaf) See adaxial.abaxial

for determining the refractive index

of liquids, minerals, and gemstones

Its operation is based on the surement of the critical angle

mea-réfractomètre d’Abbe ABC soil A soil that has a complete proÞle,including an A, a B, and a C horizon

sol ABC

of live cells) excreted by live cellsduring growth and division, attached

to cell debris and dead cells, orleaked into soil solution from extant

or lyzed cells but whose originalfunctional location was on or withinthe cell enzyme abiontique

elements and compounds of the ronment abiotique

envi-abrasion (geology) The mechanical wearing(i.e., scratch, grind, or polish) effect

on rocks caused by frictional agents(e.g., sand, pebbles, boulders) trans-ported in various ways: by wind, run-ning water, ocean waves and currents,

or glacier ice abrasion

graph See ordinate abscisse

alcool absolu

mea-sured in degrees Celsius from lute zero, –273.16∞C Absolute tem-peratures are given on a scale ofKelvin (e.g., 150 K) température absolue

all thermal motion of atoms and 3115_book Page 1 Tuesday, August 12, 2003 11:25 AM

absorbance 2 acid

A molecules theoretically ceases;–273.16∞C zéro absolu

absorbance T h e a m o u n t o f l i g h t

absorbed by a solution; the measure

is used to determine the tion of certain ions or molecules in asolution absorbance

in a soil mass and having physicalproperties similar to ordinary water

at the same temperature and sure eau absorbée

absorbed by a body to that incidentupon it Also called absorption factor

absorptance, facteur d’absorption

which the energy of electromagnetic radiation is taken up by a moleculeand transformed into a different form

of energy (chemistry) The process

by which one substance is taken up

by another substance absorption

over which radiant energy is absorbed

by a speciÞc material that may bepresent on the Earth’s surface or in theatmosphere. bande d’absorption

radiation by a solid body, liquid, orgas The absorbed energy may betransferred or re-emitted. absorption

du rayonnement

water into the plant root resultingfrom the root’s metabolic processes,usually against an electrochemicalpotential gradient absorption active

water into the plant root as a result

of diffusion along an activity ent absorption passive

radi-ant energy absorbed in a unit area ofabsorbing material; measured inwatts per square centimeter pouvoir d’absorption, pouvoir absorbant

radiation absorbed by a body to themaximum amount it can absorb Asurface that is a poor reßector is a

good absorber If no radiation isreßected, the surface acts as a blackbody and has an absorptivity and

emissivity of 1. absorptivité

except the transition is between an Aand a C horizon in a proÞle lacking

a B horizon horizon AC

pro-Þle, including an A and a C horizon,but no clearly developed B horizon.Commonly, such soils are young,like those developing from alluvium

or on steep, rocky slopes sol AC

about 50 mm) inserted through thesoil root zone for passage of a neutron probe to determine the water content

of soil at various depths. tube d’accès accelerated erosion See erosion érosion accélérée

acclimation See acclimatization tation

behav-ioral adjustments of an organism inresponse to a change in environment

acclimatation

calcula-tion, measurement, or set of surements agrees with a true value or

mea-an accepted reference value racy includes a combination of ran-dom error (precision) and systematicerror (bias) components that are due

Accu-to sampling and analytical tions exactitude

estimate denitriÞcation by ing release of nitrous oxide fromacetylene-treated soil test de blo- cage à l’acétylène

of nitrogenase activity accomplished

by measuring the rate of acetylenereduction to ethylene test de réduc- tion de l’acétylène

acid A substance that contains hydrogen anddissociates in water to produce positivehydrogen ions (or H3O+) (i.e., Arrhe-nius theory) A substance that exhibits

a tendency to release a proton (i.e.,

acid deposition 3 acidity, salt-replaceable

A

Lowry-Brønsted theory) An acid is a

compound that can accept a pair of

electrons, and a base is one that can

donate an electron pair (i.e., Lewis

the-ory) acide

intro-duced to the ground or surface waters

including wet deposition from

precip-itation, dry deposition from particle

fallout, and acid fog Air

contami-nants, such as sulfur oxides and

nitro-gen oxides, from both anthropogenic

and natural sources react with water

in the atmosphere to form acids Often

called acid rain déposition acide

resi-due remaining after extraction of

herbage with acid detergent; cell wall

constituents minus hemicellulose

Þbre au détergent acide (ADF)

acid detergent Þber digestibility T h e

digestibility of acid detergent Þber

(ADF) of a forage, calculated as the

percent difference ADF measured

before and after in vitro or in vivo

digestion digestibilité de la Þbre au

détergent acide

acid dissociation constant (K a ) The

equi-librium constant for a reaction in

which a proton is removed from an

acid by H2O to form the conjugate

base and H3O+; a measure of the

strength of the acid. constante de

dissociation d’un acide

acid (e.g., hydrogen chloride) gaz

acide

by sulfuric acid produced by seepage

through sulfur-bearing spoil and

tail-ings from coal and metal mining

drainage minier acide

acid rain See acid deposition pluie acide

7.0 See reaction, soil sol acide

acid spoil Coal and metal mine tailings that

contain sulfur and generate acidity

déblais acides

acid-base indicator A s u b s t a n c e t h a t

marks the end point of an acid-base

titration by changing color teur acido-basique

indica-acid-forming fertilizer S e e f e r t i l i z e r

engrais acidiÞant acidic Having a low pH value (less than 7);

the opposite of alkaline acide

water, undergoes hydrolysis resulting

in an acidic solution Hydrated acidiccations donate protons to water toform hydronium ions (H3O+) and thus

in aqueous solution are acids sted deÞnition) Examples in soils are

(Bron-H+, Al3+, and Fe3+ cation acidique acidic rock Igneous rock that is high in sil-ica, generally greater than 52% One

of four subdivisions of a commonlyused system for classifying igneousrocks based on silica content (e.g.,acidic, intermediate rock, basic rock,and ultrabasic rock).roche acide

ion concentration is greater than itshydroxyl ion concentration, or whose

pH is less than 7.0. solution acide

standard solution of an acid is added

to the unknown (base) solution todetermine the amount of basepresent acidimétrie

acidity constant See acid dissociation stant constante d’acidité

con-acidity, exchangeable T h e a m o u n t o fexchangeable hydrogen and alumi-num ions in soil, as estimated byreplacement from a soil by an unbuf-fered salt solution such as KCl orNaCl Also called “salt-replaceableacidity.” acidité d’échange

acidity, residual Soil acidity that is ized by lime or other alkaline mate-rials, but which cannot be replaced

neutral-by an unbuffered salt solution; culated by subtraction of saltreplaceable acidity from total acidity

cal-acidité résiduelle

and hydrogen that can be replacedfrom an acid soil by an unbufferedsalt solution such as KCl or NaCl

acidité échangeable par un sel

acidity, total 4 adaptation

A acidity, totalclay, usually estimated by a bufferedThe total acidity in a soil or

exchange capacity – exchangeable bases] = total acidity Also approxi-mated by the sum of salt replaceableacidity + residual acidity Often cal-culated by subtraction of exchange-able bases from the cation exchangecapacity determined by ammoniumexchange at pH 7.0 It can be deter-mined directly using pH buffer-saltmixtures (e.g., BaCl2 plus triethano-lamine, pH 8.0 or 8.2) and titratingthe basicity neutralized after reactionwith a soil acidité totale

acidophilic Preferring or thriving in a

rela-tively acid environment acidiphile,

acidophile acidulation The process of treating a fer-

tilizer source with an acid or mixture

of acids (e.g., treating phosphaterock with sulfuric, nitric, or phos-

phoric acid) acidulation

actinometer An instrument which

mea-sures solar radiation The sponding term for a recording instru-

corre-ment is actinograph pyranomètre,

actinomètre actinomycetes Gram-positive bacteria that

form branching Þlaments They may

form true mycelia or produce

conid-iospores The pleasant odor offreshly plowed ground comes from

actinomycetes in the soil See Þgure.

actinomycète

activated carbon A highly absorbent form

of carbon, used to remove odors andtoxic substances from gaseous emis-sions and dissolved organic matter

from wastewater See carbon tion charbon activé ou actif

Þltra-activation energy The minimum amount of

energy required for a chemical reaction

to take place énergie d’activation

active organic matter The portion of soil

organic matter composed of materialthat is relatively easy to decompose

by soil microorganisms Also calledactive fraction of organic matter

matière organique active active ingredient The chemical compo-

nent(s) in a pesticide product or mulation that causes the desiredeffect on the speciÞc pest Usuallyexpressed as a percent and abbrevi-

for-ated as a.i matière active

active layer The top layer of soil in a

per-mafrost zone, subjected to seasonalfreezing and thawing which, duringthe melt season, becomes very

mobile couche active

activity (chemistry) (1) A dimensionless

measure of the deviation of thechemical potential of a substancefrom its value in some state which,for convenience, is chosen as a stan-dard state DeÞned by the equation:

m = m∞ + RT ln a, where m is the

chemical potential in a state in which

the activity is a, m∞ is the chemicalpotential in the standard state (where

a = 1.0), R is the molar gas constant,

and T is the absolute temperature (2)The effective concentration of a sub-

stance in a solution activité

actual use (range-pasture) The use of

for-age on any area by livestock and/orgame animals without reference topermitted or recommended use; usu-ally expressed in terms of animal unit

months or animal units utilisation

courante (parcours-pâturage) adaptation A change in the structure,

physiology, or behavior of an ism resulting from natural selection

organ-or variation of genetic characteristics

by which the organism becomes ter Þtted to survive in its environ-

bet-ment adaptation

Actinomycete

adaptive enzyme (enzyme induction) 5 adsorption

A

adaptive enzyme (enzyme induction) An

enzyme produced by an organism in

response to the presence of a speciÞc

substrate or a related substance Also

called an induced or inducible

enzyme enzyme induite

adaptive management Management

prac-tice in natural resource exploitation

that rigorously combines

manage-ment, research, monitoring, and

means of changing practices so that

credible information is gained and

management activities are modiÞed

by experience gestion adaptative

adaptive zone A unit of environment

occu-pied by a single type of organism,

because particular environmental

opportunities require similar

adapta-tions for diverse species Species in

different adaptive zones usually differ

by major morphologic or physiologic

characteristics zone adaptative

adaxial (botany) Facing toward the stem of

a plant (e.g., the upper surface of a

leaf) See abaxial adaxial

additive effects (1) The combination of

reactions or substances, acting

together or independently, to cause a

total response equal to or greater than

the sum of the separate reactions or

substances (e.g., the combined toxic

effects of more than one pollutant)

(2) Effects on biota of stress imposed

by one mechanism, contributed from

more than one source (e.g.,

sediment-related stress on Þsh imposed by

sed-iment derived from streambank and

land surface sources) See also

adenosine diphosphate (ADP) On

hydrol-ysis, adenosine triphosphate (ATP)

loses one phosphate to become

ade-nosine diphosphate (ADP), releasing

usable energy adénosine

diphos-phate (ADP)

adenosine triphosphate (ATP) An energy

storage compound common to all

biological systems The high-energy

intermediate is formed during

photo-synthesis or by the breakdown of

energy-containing material, such as

glucose Supplies the energy for allcellular reactions and functions

adénosine triphosphate (ATP) adenylate energy charge ratio (EC) A

measure of the metabolic state ofmicroorganisms and state of growth

of natural microbial communities

The energy charge ratio is calculatedusing the formula: EC = (ATP +1/2ADP)/(ATP + ADP + AMP) Thedenominator represents the total ade-nylate pool; the numerator, the por-tion charged with high energy phos-

phate bonds charge énergétique

adhesion (chemistry) A force that acts to

hold the molecules of dissimilar stances together The static attractiveforce at the contact surface betweentwo bodies of different substances

sub-(soil mechanics) The shearing

resis-tance between soil and another rial under zero externally applied

mate-pressure adhésion

adiabatic process A process that occurs

without heat entering or leaving asystem Generally involves a rise orfall in the temperature of the system

transformation adiabatique adobe soil Clayey and silty deposits found

in the desert basins of southwesternNorth America and in Mexico; usedextensively for making sun-dried

brick terre à briques

adsorbed water Water held in a soil by

physicochemical forces and havingphysical properties substantially differ-

ent from absorbed water or chemically

combined water at the same

tempera-ture and pressure eau adsorbée

adsorption The process by which atoms,

molecules, or ions are taken up andretained on the surfaces of solids bychemical or physical binding (e.g.,the adsorption of cations by nega-tively charged minerals) The twotypes of adsorption are physisorption,

in which the attractive forces are

purely van der Waals, and

chemisorp-tion, where chemical bonds are ally formed between the adsorbent(the material doing the adsorbing)

actu-adsorption complex 6 after-ripening

A and adsorbate (the material beingadsorbed) adsorption

adsorption complex The group of

sub-stances in the soil capable of ing ions and molecules Organic andinorganic colloidal substances formthe greater part of the adsorptioncomplex The noncolloidal materials,such as silt and sand, exhibit adsorp-tion to a much lesser extent than the

adsorb-colloidal materials complexe

d’adsorption adsorption isotherm A graph of the quan-

tity of a given chemical speciesbound to an adsorption complex(e.g., soil) at Þxed temperature, as afunction of the concentration of thespecies in a solution in equilibrium

iso-therme d’adsorption advection The movement of air, water, and

other ßuids in a horizontal plane

advection adventitious roots Roots that arise from

unusual parts of a plant, usually ing on aerial organs, rhizomes, andolder parts of the root body They candevelop under normal environmentalconditions or in response to pathogensand wounding They are found amongall vascular plants, and in some casesmay be essential to normal growth

form-and development racines adventives

aerate To impregnate with a gas, usually

air aérer

aerial photograph (remote sensing) A

pho-tograph of the Earth’s surface takenfrom airborne equipment; sometimescalled aerial photo or air photograph

An oblique aerial photograph is takenwith the camera axis directed betweenthe horizontal and vertical In a highoblique photograph, the apparent hori-zon is shown, and in a low obliquephotograph the apparent horizon is notshown A vertical aerial photograph ismade with the optical axis of the cam-era approximately perpendicular to theEarth’s surface and with the Þlm asnearly horizontal as practical See

aéri-enne aerial reconnaissance The collection of

information by visual, electronic, orphotographic means from the air

reconnaissance aérienne aerial survey A survey using photographic,

electronic, or other data obtained

from an airborne platform levé

aérophotogrammétrique

phototriangula-tion aérotriangulation

aerobe Organism requiring oxygen for

growth organisme aérobie

aerobic (1) Having molecular oxygen as a

part of the environment (2) Growingonly in the presence of molecularoxygen, such as aerobic organisms.(3) Occurring only in the presence ofmolecular oxygen, as applied to cer-tain chemical or biochemical pro-cesses such as aerobic decomposi-

tion aérobie

aerobic decomposition The

biodegrada-tion of materials by aerobic ganisms; the process produces car-bon dioxide, water, and other mineralproducts Generally a faster break-down than anaerobic decomposition

microor-décomposition aérobie aerosols Particles of matter, solid or liquid,

larger than a molecule but smallenough to remain suspended in the

atmosphere Particles can come from

natural sources (e.g., particles from seaspray or clay particles from the weath-ering of rocks, both of which are car-ried upward by the wind) or result fromhuman activities (Such particles are

often considered pollutants.) aérosols

afforestation The artiÞcial establishment of

forest crops by planting or sowing onland that has not previously, orrecently, grown tree crops See also

aßatoxin Toxins produced by the fungus

Aspergillus ßavus in grains or

grain-meals stored under moist conditions;

a known carcinogen aßatoxine

after-ripening A curing process sometimes

required by seeds, bulbs, and related

agar 7 agroecological resource region

A

structures of various plants before

germination will take place

post-maturation

agar A complex polysaccharide, derived

from a particular marine algae, that

is a gelling agent in the preparation

of nutrient media for growing

micro-organisms Consists of about 70%

agarose and 30% agaropectin Can

be melted at temperatures above

100∞C; gelling temperature is 40 to

50∞C agar

age structure The distribution of

individu-als in a population into age classes

structure d’âge

aggregate A soil structure unit formed by

biological and physical agents in

which soil primary particles (i.e.,

sand, silt, clay), along with colloidal

and particulate organic and inorganic

materials, are grouped together to

form larger secondary particles A

group of soil particles cohering in

such a way that they behave

mechan-ically as a discrete unit agrégat

aggregate distribution The

characteriza-tion of soil aggregates, usually on the

basis of a sieving procedure, based

on size range (e.g., 5 to 0.25 mm) or

speciÞc order (e.g., micro-aggregate

and macro-aggregate) distribution

des agrégats

aggregate stability The ability of soil

aggregates to resist rearrangement

and breakdown into primary

parti-cles by various disruptive forces,

especially the effects of water The

stability of aggregates to disruptive

processes is related to soil particle

size distribution, type of clay

min-eral, speciÞc ions associated with the

clay, the kind and amount of organic

matter present, and nature of the

microbial population stabilité des

agrégats

aggregated A broad category of soil

struc-ture, in which primary particles (e.g.,

sand, silt, clay) unite to form

second-ary particles or aggregates

struc-ture agrégée ou fragmentaire

aggregation The process whereby primary

soil particles (i.e, sand, silt, clay) are

bonded together to form aggregates,

usually by natural forces and stances derived from root exudates

sub-and microbial activity agrégation

agric horizon A diagnostic subsurface

illu-vial horizon (U.S system of soil onomy) formed under cultivation,containing signiÞcant amounts of

tax-illuvial silt, clay, and humus

hori-zon agrique agri-environmental indicator A measure

of a key environmental condition,risk, or change resulting from agri-culture; a measure of management

practices used by producers

indica-teur agro-environnemental agrichemical A chemical used in agricul-

ture (e.g., fertilizers, pesticides, andother chemicals used in crop produc-

tion) produit agrochimique

agroclimate A compilation of the average

and extreme weather as it affectsagricultural cropping in a given area

Agroclimatic classiÞcation in ada is based on limitations of avail-

Can-able heat and/or moisture

agrocli-mat agroecological resource area A n a t u r a l

landscape area more or less uniform

in terms of ecoclimate, landform,soils, and general agricultural poten-tial Agroecological resource areas

are subdivisions of agroecological

resource regions The extent of an

agroecological resource area is in theorder of tens to hundreds of square

km Introduced in Canada as nient planning units upon which todevelop databases for use in agricul-tural research These units can beused to study agricultural systems,land use, conservation, and theimpacts of various management and

conve-socio-economic practices aire de

ressource agroécologique agroecological resource region A l a r g e

area with broadly similar tural potential and types of farming

agricul-Separated on the basis of general

agroecological zone 8 air dry

A agro-climatic and physiographiccharacteristics, landform, soils, and

general agricultural potential Theextent of an agroecological resourceregion is large, in the order of hun-dreds of square km See agroecolog-

res-source agroécologique agroecological zone A geographic map-

ping unit developed by the Food andAgriculture Organization of theUnited Nations, based on climaticconditions and landforms that deter-mine relatively homogeneous cropgrowing environments Character-ization of agroecological zones per-mits a quantitative assessment of thebiophysical resources upon whichagriculture and forestry researchdepend The classiÞcation systemdistinguishes between tropicalregions, subtropical regions withsummer or winter rainfall, and tem-perate regions These major regionsare further subdivided into rainfedmoisture zones, lengths of growingperiods, and thermal zones, based onthe prevailing temperature regimeduring the growing season ClassiÞ-cations include tropical, subtropical,temperate, warm, cool, warm/cool,arid, semiarid, subhumid, and humid

zone de ressource agroécologique

agroecosystem A dynamic landscape

asso-ciation of crops, pastures, livestock,other ßora and fauna, atmosphere,soils, and water Agroecosystems arecontained within larger landscapesthat include uncultivated land, natu-

ral ecosystems, and rural

communi-ties They are open dynamic systemsconnected to other ecosystemsthrough the transfer of energy and

material agroécosystème,

éco-système agricole agroecosystem complexity ClassiÞcation

of agricultural systems on the basis

of biodiversity of species (i.e., crops,livestock, pests, trees), and spatial(e.g., Þeld size) and temporal (e.g.,type and length of crop rotation)

dimensions diversité ou complexité

d’un agroécosystème agroforestry Land use system in which

woody perennials are grown forwood production with agriculturalcrops, with or without livestock pro-

duction agroforesterie,

agrosylvi-culture agrohydrology The science dealing with

the distribution and movement ofrainfall and/or irrigation water andsoil solution to and from the rootzone in agricultural land See hydrol- ogy hydrologie agricole

agrology The study of applied phases of

soil science and soil management A

broader term than agronomy

agrol-ogie agronomic practices Soil and crop activi-

ties used in the production of farmcrops (e.g., seed selection, seedbedpreparation, fertilizing, liming,manuring, seeding, cultivation, har-vesting, curing, crop sequence, croprotations, cover crops, stripcropping,

pasture development) pratiques

agronomiques ou agricoles agronomically sustainable yield T h e

maximum yield that can be achieved

by a given crop cultivar in a givenarea, taking account of climatic, soil,and other physical or biological con-

straints rendement agronomique

durable agronomy The branch of agriculture that

deals with the theory and practice ofÞeld-crop production and soil man-

agement agronomie

agro-silvo-pastoral Land use system in

which woody perennials are grownwith agricultural crops, forage crops,

and livestock production

agro-sylvo-pastoral agrostology Study of grasses; classiÞca-

tion, management, and utilization of

grasses agrostologie

air dry The state of dryness (water content)

of a soil at equilibrium with the ture contained in the surrounding

mois-atmosphere séché à l'air

air entry value 9 Alfisols

A

air entry value The value of water content

or potential at which air Þrst enters

a porous medium point d’entrée

d’air

air frost Air at Stevenson screen level (1.2

m) with a temperature at or below

0°C gel atmosphérique

air pollution The presence of contaminants

in the air in concentrations that

pre-vent the normal dispersive ability of

air and interfere with human health,

safety, or comfort Air contaminants

can have a human origin (e.g.,

smokestacks) or a natural origin

(e.g., dust storms) pollution de l’air

air porosity The portion of the bulk volume

of soil that is Þlled with air at any

given time or under a given condition

(e.g., a speciÞed soil water potential)

Usually, this portion is made up of

large pores (i.e., those drained by a

potential of more than about -100 cm

of water) porosité d’air, teneur en

air

air dry (1) The state of dryness of a soil at

equilibrium with the moisture

con-tent of the surrounding atmosphere

The moisture content depends on the

relative humidity and the

tempera-ture of the surrounding atmosphere

(2) To allow a soil sample to reach

equilibrium in moisture content with

the surrounding atmosphere See

air-dry mass Mass of a substance (e.g.,

soil) after it has been allowed to dry

to equilibrium with the atmosphere

masse sèche à l’air

air-Þlled porosity A measure of the

rela-tive air content of a soil As an index

of soil aeration it is related

nega-tively to degree of saturation See air

porosity porosité d’air, teneur en

air

akinete A nonmotile spore formed singly

within a cell and with the spore wall

fused with the parent cell wall

akinète

alban (soil micromorphology) A

light-col-ored cutan composed of materials

that have been strongly reduced

albane albedo The ratio of reßected to incident

light, expressed as a percentage or afraction of 1 Snow-covered areashave a high albedo (up to about 0.9

or 90%) due to their white color,whereas vegetation has a low albedo(generally about 0.1 or 10%) due tothe dark color and the absorption of

light for photosynthesis Clouds have

an intermediate albedo and are themost important contributor to theEarth’s albedo, which is about 0.3

albédo albic horizon A subsurface diagnostic min-

eral horizon in the U.S system of soiltaxonomy from which clay and freeiron has been removed, or in whichthe oxides of iron have been segre-gated to the extent that the horizoncolor is determined primarily by thecolor of the primary sand and silt

particles An eluvial horizon

hori-zon albique Albolls A suborder in the U.S system of

soil taxonomy Mollisols that have an

albic horizon immediately below the mollic epipedon These soils have an argillic or natric horizon and mot-

tles, iron-manganese concretions, orboth, within the albic, argillic, or nat-

ric horizon Albolls

alcohol An organic compound that contains

the –OH group (e.g., simple alcoholsare methanol (CH3OH) and ethanol(C2H5OH)) alcool

aldehyde An organic compound that

con-tains the –CHO group (the aldehydegroup) which consists of a carbonylgroup attached to a hydrogen atom(e.g., methanol or formaldehyde(HCHO) and ethanol or acetaldehyde(CH3CHO)) aldéhyde

AlÞsols An order in the U S system of soil

taxonomy Mineral soils that have

umbric or ochric epipedons, argillic

horizons, and hold water at <1.5 MPatension during at least 90 days whenthe soil is warm enough for plants togrow outdoors AlÞsols have a mean

alga (plural algae) 10 alkalinity, soil

A annual soil temperature of <8°C or abase saturation in the lower part of

the argillic horizon of 35% or more

when measured at pH 8.2 AlÞsols

alga (plural algae) Phototrophic

eukary-otic microorganism Algae containchlorophyll and are unicellular ormulticellular They form the base ofthe food chain in aquatic environ-ments; some species may create anuisance when environmental condi-tions are suitable for proliÞc growth

algue

algal bloom A proliferation of living algae

on the surface of lakes, streams, orponds Algal blooms are stimulated

by phosphate enrichment

proliféra-tion algale algicide A chemical compound used to kill

Þlamentous algae and

phytoplank-ton algicide

algology The study of algae algologie

algorithm A series of well-deÞned steps

used in carrying out a speciÞc cess (e.g., a classiÞcation algorithm)

pro-An algorithm may be in the form of

a word description, explanatory note,diagram, labeled ßow chart, or com-

puter code algorithme

aliphatic compound A n o rga n i c c o m

-pound in which carbon and hydrogenmolecules are arranged in straight orbranched chains (i.e., no ring struc-tures present); a type of hydrocarbon

An organic compound that is an

alkane, alkene, or alkyne, or a

deriv-ative of these composé aliphatique

aliquot A subsample resulting from

divid-ing a liquid sample into a number ofequal parts Generally used to deÞneany representative portion of the

sample aliquote

alkali Any substance capable of furnishing

to its solution or other substances thehydroxyl ion (OH-); a substance hav-ing marked basic properties in con-

trast to acid alcali

alkali metals (group 1 elements) A group

of soft reactive metals, each senting the start of a new period inthe periodic table The alkali metals

repre-are lithium (Li), sodium (Na), sium (K), rubidium, (RB), cesium

potas-(Cs), and francium (Fr) métaux

alcalins alkali soil (1) A soil having a high degree

of alkalinity (pH of 8.5 or higher), orhaving a high exchangeable sodiumcontent (15% or more of theexchange capacity), or both (2) Asoil that contains enough alkali (i.e.,sodium) to interfere with the growth

of most crop plants sol à alcalis, sol

alcalin alkaline Having a high pH value (greater

than 7); also basic; the opposite of

acidic alcalin

alkaline soil A soil that has a pH greater

than 7.0 See reaction, soil sol alcalin alkaline solution A liquid whose hydroxyl

ion concentration is greater than itshydrogen ion concentration, or

whose pH is greater than 7.0

solu-tion alcaline alkaline-earth metals (group 2 elements)

A group of moderately reactive als, harder and less volatile than the

met-alkali metals The term met-alkaline earth

strictly refers to the oxides, but isoften used loosely for the elementsthemselves The elements are beryl-lium (Be), magnesium (Mg), calcium(Ca), strontium (Sr), barium (Ba),

and radium (Ra) métaux

alcalino-terreux alkalinity (1) The quality or state of being

alkaline; the concentration of OHions (2) A measure of the ability ofwater to neutralize acids It is mea-sured by determining the amount ofacid required to lower the pH ofwater to 4.5 In natural waters, thealkalinity is effectively the bicarbon-ate ion concentration plus twice the

-c a r b o n a t e i o n -c o n -c e n t r a t i o n ,expressed as milligrams per liter cal-

cium carbonate alcalinité

alkalinity, soil The degree or intensity of

alkalinity of a soil expressed by a soil

pH value greater than 7.0 alcalinité

du sol

alkalinity, total 11 alpha decay

A

alkalinity, total The total measurable bases

(OH, HCO3, CO3) in a volume of

water; a measure of the material’s

capacity to neutralize acids

alcalin-ité totale

alkalization The accumulation of sodium

ions on the exchange sites in a soil

alcalinisation

alkaloid One of a class of basic organic

compounds with nitrogen in their

structure; a secondary product of

plant metabolism alcalọde

alkane A type of saturated hydrocarbon

with the general formula CnH2n+2

The straight-chain alkanes form a

homologous series methane (CH4),

ethane (C2H6), propane (C3H8),

butane (C4H10), pentane (C5H12), etc

Low molecular weight alkanes are

gases; high molecular weight alkanes

are waxy solids Alkanes are fairly

unreactive alcane

alkene A type of unsaturated hydrocarbon

with the general formula CnH2n

Alk-enes contain one or more

car-bon–carbon double bonds and form

a homologous series beginning with

ethene (C2H4) and propene (C3H6)

alcène

alkyl group A group obtained by removing

a hydrogen atom from an alkane or

other aliphatic compound

groupe-ment alcoyle ou alkyle

alkyne A type of unsaturated hydrocarbon

with the general formula CnH2n-2 that

contains one or more triple

carbon-carbon bonds The simplest member

of the homologous series is ethyne

(acetylene, C2H2) alkine

allele Any of a group of alternative forms

of the same gene allèle

allelopathy Any direct or indirect harmful

effect of one plant or microorganism

on one or more other organisms

through the production and release

of chemical compounds into the

environment allélopathie

allitization See desilication allitisation

allochthonous Non-native or transient;

referring to organisms that are not

indigenous to a speciÞc habitat but

enter or are transported into the itat by various means (e.g., in precip-itation, diseased tissues, manure, orsewage) They may persist for sometime but do not contribute in a sig-niÞcant way to ecological transfor-mations or interactions, reproduce,

hab-or occupy the habitat permanently

allochtone allochthonous peat Peat formed from the

remains of plants brought in, mainly

by water, from outside the site ofdeposition Constitutes an integral

part of peat deposits that develop

from the Þlling in of water bodies bylateral or vertical transport or both

See autochthonous peat, limnetic

tourbe allochtone allogenic succession Changes in species

composition and environmentalproperties due to changes in extrinsicenvironmental factors (e.g., Þre)

succession allogène allopatric speciation Separation of a pop-

ulation into two or more evolutionaryunits as a result of reproductive iso-lation caused by geographic separa-

tion of two subpopulations

spécia-tion allopatrique allophane An aluminosilicate with prima-

rily short-range structural order;

occurs as very small spherical cles, especially in soils formed fromvolcanic ash Also occurs in podzolicsoils formed on weathered granite in

parti-a cool, moist climparti-ate parti-allophparti-ane

alloy A substance that contains a mixture of

elements and has metallic properties

alliage

alluvial Pertaining to alluvium alluvial

alluvial terrace See river terrace terrasse

alluviale alluvium Material (e.g., clay, silt, sand, and

gravel) deposited by running water,including the sediments laid down in

riverbeds, ßood plains, lakes, and

estuaries alluvion

alpha decay The spontaneous

decomposi-tion of the atom nuclei resulting in

the emission of alpha particles

dés-intégration alpha

alpha diversity 12 ammonia

A alpha diversity Diversity within a speciÞc community diversité alpha

première espèce, erreur de type I alpha particle A positively charged parti-

cle emitted by some radioactivematerials It is the least penetrating

of the three common types of tion (alpha, beta, and gamma) and isusually not dangerous to plants, ani-mals, or humans A high-energyhelium nucleus (two protons, twoneutrons) emitted by some heavy

radia-radioactive nuclei particule alpha

alpine Of, pertaining to, or like any high

mountain; implying high elevationand cold climate; referring to thatportion of mountains above treegrowth, or the organisms living there

alpin

alpine biome Considered as a biome or a

subtype of the tundra biome A

mountain area above the timberlinecharacterized by permanently frozensubsoil and a dominant vegetation ofmosses, lichens, herbs, and dwarf

shrubs biome alpin

alpine soil A mountain soil occurring

above the tree line sol alpin

alpine tundra The grassland area found

above the tree line on mountain

ranges toundra alpine

altimeter An instrument that indicates

height above sea level, based on theaverage decrease in atmosphericpressure with increasing height Thisaverages 3.4 kPa for every 300 m,but variations occur owing to differ-ences of air temperature and latitude

Used mainly in aircraft but also byground surveyors An altigraph is a

self-recording altimeter altimètre

aluminosilicate See silicate silicate

d’alu-minium aluminum A soft, moderately reactive

metal; the second element in groupIII of the periodic table There arenumerous minerals of aluminum; it

is the third most abundant element inthe Earth’s crust (8.1% by weight)

Commercially important minerals

are bauxite (hydrated Al2O3), dum (anhydrous Al2O3), cryolite(Na3AlF6), and clays and mica (alu-

corun-minosilicates) aluminium

amendment, soil The addition of

materi-als (e.g., lime, gypsum, sawdust,compost, animal manures, or syn-thetic soil conditioners) to soil toenhance plant growth Fertilizersconstitute a special group of soil

amendments amendement du sol

amensalism The suppression of one

organ-ism by another, often involving

tox-ins allélopathie

amictic lake A lake that does not

experi-ence mixing or turnover on a

sea-sonal basis See dimictic lake lac

amictique

amide Any of a group of herbicides

designed to retard root and shootgrowth, mostly effective on grassyweeds, causing stunted and mal-

formed seedlings amide

amines Organic compounds derived by

replacing one or more of the gen atoms attached to nitrogen byone or more organic groups The dif-ferent types of amines are named forthe number groups attached to thenitrogen atom: primary amines haveone hydrogen atom replaced (e.g.,methyline [CH3NH2]); secondaryamines have two hydrogen atomsreplaced (e.g., dimethylamine[(CH3)2NH]); and tertiary amineshave all three hydrogen atomsreplaced (e.g., trimethylamine[(CH3)3N]) Amines are producedduring the decomposition of organic

hydro-nitrogen amines

amino acid An organic acid containing

both an amino (NH2) and a carboxyl(COOH) group Amino acid mole-cules combine to form proteins

acide aminé ammate A chemical compound, ammo-

nium sulfamate, used as a relatively

short-lived herbicide ammate

ammonia The gaseous compound of

nitrogen and hydrogen (e.g., NH3);commonly known as anhydrous

ammonia volatilization 13 amorphous peat

A

ammonia in the fertilizer industry

ammoniaque

ammonia volatilization Mass transfer of

nitrogen as ammonia gas from soil,

plant, or liquid systems to the

atmo-sphere volatilisation de

l’ammoni-aque

ammoniation The process of introducing

various ammonium sources into

other fertilizer sources forming

ammoniated compounds (e.g.,

ammonium polyphosphates,

ammo-niated superphosphate)

ammonia-tion

ammoniÞcation A biochemical process

carried out by microorganisms in

which nitrogen-containing organic

compounds are degraded or

mineral-ized and ammoniacal nitrogen is

formed ammoniÞcation

ammonium entrapment See ammonium

Þxation Þxation ou intégration de

l’ammonium en position

inter-feuillet

ammonium Þxation T h e p r o c e s s o f

entrapment of ammonium ions in

interlayer spaces of phyllosilicates,

in sites similar to K+ in micas

Smec-tites, illites, and vermiculites all can

Þx ammonium, but vermiculite has

the greatest capacity The Þxation

may occur spontaneously in aqueous

suspensions, or as a result of heating

to remove interlayer water

Ammo-nium ions in collapsed interlayer

spaces are exchangeable only after

expansion of the interlayer See

p o t a s s i u m Þ x a t i o n Þ x a t i o n

d’ammonium

ammonium nitrate A colorless crystalline

compound readily soluble in water

(971 g per 100 g of water at 100°C),

produced by combining anhydrous

ammonia with nitric acid; NH4NO3

It is used in the manufacture of

explosives and, because of its high

nitrogen content, as a fertilizer

nitrate d’ammonium

ammonium phosphate A general class

of compounds used as phosphorus

fertilizers; manufactured by the

reac-tion of anhydrous ammonia withorthophosphoric acid or superphos-phoric acid to produce either solid orliquid products; (NH4)3PO4 phos-

phate d’ammonium ammonium sulfate A colorless crystalline

solid that is soluble in water;

(NH4)2SO4 When carefully heated itgives ammonium hydrogen sulfate,which on stronger heating yieldsnitrogen, ammonia, sulfur dioxide,and water Manufactured by the reac-tion of ammonia with sulfuric acid

A disadvantage as a fertilizer is that

it tends to leave an acidic residue in

the soil sulfate d’ammonium

amoeba (plural amoebae) Protozoa that

can alter their cell shape, usually by

extrusion of one or more

pseudopo-dium Existing in soil in large

num-bers; many live as parasites, andsome species are pathogenic to

humans See Þgure amibe

amorphous mineral (1) A mineral that has

no deÞnite crystalline structure (2)

A mineral that has a deÞnite line structure but appears amorphousbecause of the small crystallite size

crystal-(3) A noncrystalline constituent thateither does not Þt the deÞnition ofallophane or it is uncertain that theconstituent meets allophane criteria

minéral amorphe amorphous peat The structureless portion

of an organic deposit in which plantremains are decomposed to sizes toosmall to be visually recognized

tourbe amorphe

Amoeba

amphibole 14 anastomosing

A amphibole One of the ferromagnesian sili-cate mineral group, characterized by

prismatic, columnar, or Þbrous tals with a structure of cross-linkeddouble chains of tetrahedra (e.g.,

crys-hornblende) amphibole

amphoteric substance A substance that

can behave either as an acid or as a

base substance amphotère

amplitude (physics) The vertical distance

between the crest of a wave and the

base of the adjacent trough

(ecol-ogy) The range of tolerance of a

spe-cies amplitude

anabolism The metabolic process

involv-ing the conversion of simpler stances to more complex substances

sub-or the stsub-orage of energy Msub-ore erally, the synthesis of organic com-pounds within an organism Also

gen-called assimilation, biosynthesis, or

constructive metabolism See

anaerobe Organism that lives in the

absence of air (oxygen) organisme

anaérobie anaerobic (1) The absence of molecular

oxygen (2) Growing in the absence

of molecular oxygen (e.g., anaerobicbacteria) (3) Occurring in theabsence of molecular oxygen (e.g., a

biochemical process) anaérobie

anaerobic (soil) The absence of molecular

oxygen (O2); a condition that exists

in soils when they are ßooded or

compacted anaérobie (sol)

anaerobic decomposition The degradation

of materials by anaerobic ganisms living in oxygen-depletedsoil or water to form reduced com-pounds such as methane or hydrogensulÞde Generally slower than aero-

microor-bic décomposition anaérobie

anaerobic respiration A metabolic

pro-cess in which electrons are ferred from an organic compound to

trans-an inorgtrans-anic acceptor molecule otherthan oxygen The most commonacceptors are carbonate, sulfate, and

nitrate respiration anaérobie

anaglyph A stereogram in which the two

views are printed or projected imposed in complementary colors,usually red and blue By viewingthrough Þlter spectacles of corre-sponding complementary colors, a

super-stereoscopic image is formed

anag-lyphe analog A derivative of a naturally occurring

compound that an organism cannotdistinguish from the natural product.The uptake of this derivative results

in the formation of a biological ecule incapable of carrying out its

mol-proper function substance

ana-logue analysis The process of determining the

constituents or components of amaterial (i.e., sample) The twobroad major classes of analysis are,

qualitative analysis and quantitative

analysis analyse

analysis of variance, ANOVA (statistics)

The analysis of the total variability

of a set of data (measured by theirtotal sums of squares) into compo-nents which can be attributed to dif-ferent sources of variation A tablethat lists the various sources of vari-ation together with the correspond-ing degrees of freedom, sums ofsquares, mean squares, and values of

F is called an analysis of variancetable See one-way analysis of vari-

analyse de variance analyte The substance which is to be mea-

sured by chemical analysis analyte

analytical model A model in which all

functional relationships can beexpressed in closed form and theparameters Þxed so that the equa-tions can be solved by the classicalmethods of analytical mathematics

modèle analytique

anastomosing (geomorphology) Stream

patterns in which the channels cate, branch, and rejoin irregularly to

bifur-create a net-like formation

anasto-mosé

anchor 15 animal unit (A.U.)

A

anchor See tillage , anchor enfouir,

incor-porer

Andepts An obsolete term in the U.S

sys-tem of soil taxonomy for Inceptisols

that have formed in volcanic

mate-rials Andepts

andesite A Þne-grained volcanic rock

com-posed of andesine, similar in

miner-alogy to a diorite andésite

andic Soil properties related to volcanic

ori-gin of materials The properties

include organic carbon content, bulk

density, phosphate retention, and

iron and aluminum extractable with

ammonium oxalate andique

Andisols An order in the U.S system of

soil taxonomy Mineral soils

domi-nated by andic soil properties in 60%

or more of their thickness Andisols

Andosol Term used in some countries for a

soil developed on volcanic material

Characterized by a dark, organic

A-horizon and a barely altered

B-hori-zon See Inceptisol Andosol

anemometer Any instrument that

mea-sures wind speed anémomètre

angiosperm A plant with true ßowers, in

which the seeds are enclosed in an

ovary, comprising the fruit The two

subclasses are: the

Monocotyledo-neae (monocots), which are

herba-ceous and include such economically

important plants as grasses (e.g.,

maize, wheat, barley); and the

Dicot-yledoneae (dicots), which include

both woody and herbaceous

mem-bers angiosperme

angle of dip (geology) The angle that a

bed, vein, or stratum makes with the

horizontal See dip angle de chute,

pendage

angle of emergence The angle formed

between a ray of energy (e.g., optic,

acoustic, or electromagnetic) and the

horizontal It is the complement of

the angle of incidence angle

d’émergence

angle of incidence The angle that a ray of

energy (e.g., optic, acoustic, or

elec-tromagnetic) makes with the normal

to a boundary surface It is the

com-plement of the angle of emergence.

angle d’incidence angle of reßection The angle between a

ray of light reßected from a surface

and the normal to that surface angle

de réßexion angle of refraction The angle between a

ray of light that has been refracted(e.g., through water) and the normalfrom the surface at which the ray is

refracted angle de réfraction

angle of repose (rest) (geology) The

maxi-mum slope gradient at which a mass

of unconsolidated material (e.g., scree,

talus) will remain stable The angle

varies according to the character of thematerial If the slope angle becomessteeper than the angle of repose theslope becomes unstable, leading to alandslide or earth-ßow until the slopeangle returns to a state of stability Thecoarser the material, the higher the

angle of repose angle de repos

angular Having sharp angles or borders;

especially applied to sedimentaryparticles showing little or no evi-dence of abrasion, with all edges andcorners sharp Also, applied to theroundness class containing angular

particles anguleux

angularity S e e ro u n d n e s s fo r m e

anguleuse anhedral A form of minerals that are not

bounded by their own crystal faces butwhose forms are controlled by min-eral grains next to them Also called

allotriomorphic allotriomorphe

anhydrite A mineral, anhydrous calcium

sulfate, CaSO4 Orthorhombic, monly massive in evaporite beds

com-Under natural conditions it slowlyhydrates to form gypsum Used in themanufacture of cements and fertiliz-

ers anhydrite

animal unit (A.U.) A measurement of

live-stock based on the equivalent of amature cow (about 454 kg liveweight); roughly one cow, one horse,one mule, Þve sheep, Þve swine, or

six goats unité animale (U.A.),

unité-gros-bétail (U.G.B.)

animal unit month (A.U.M.) 16 anthropic epipedon

A animal unit month (A.U.M.) A measureof forage or feed requirement to

maintain one animal unit for one

m o n t h u n i t é a n i m a l e - m o i s

(U.A.M.) anion A negatively charged ion anion

anion exchange capacity The total amount

of exchangeable anions that a soil canadsorb It is expressed as centimoles,

or millimoles, of charge per kilogram

of soil or other adsorbing material

such as clay capacité d’échange

anionique anion exclusion The exclusion or repulsion

of anions from the vicinity of tively charged soil particle surfaces

nega-exclusion anionique anionic resin An ion-exchange material

that can exchange an anion, such as

Cl- and OH-, for anions in the rounding medium; used for a widerange of analytical and puriÞcation

sur-purposes résine anionique

anisotropic soils Soils not having the same

physical properties when the

direc-tion of measurement is changed sols

anisotropes anisotropy The condition of having differ-

ent properties in different directions

For example, in soil there is verticalanisotropy due to the presence of dif-ferent horizons; in geology, geologicstrata transmit sound waves with dif-ferent velocities in the vertical andhorizontal directions; in crystallogra-phy, crystalline materials not belong-ing to the cubic crystal system are

optically anisotropic anisotropie

annelid (zoology) Member of the phylum

Annelida containing red-blooded

worms such as earthworms annélide

annual plant A plant that completes its life

cycle (from germination to ßowering

to seed production and the death ofits vegetative parts) within a single

growing season See biennial plant ,

anomaly A deviation from the norm; a

devi-ation of an observed value from a oretical value due to an abnormality

the-in the observed quantity anomalie

de variance

antagonism (ecology) Production of a

sub-stance by an organism that candestroy or prevent the growth of one

or more organisms (plant nutrition)

The interference of one element withthe absorption or utilization of an

essential nutrient by plants

(chemis-try) Strong competition between pairs

of similar ions (e.g., Ca2+ and Sr2+, K+and Rb+) (pollution) The combined

reaction of several pollutants actingsimultaneously or independently tocause a total response less than their

separate effects antagonisme

antecedent moisture The soil water

con-tent prior to the sampling or

mea-s u r e m e n t ev e n t h u m i d i t é

antérieure anther The pollen-bearing portion of a sta-

men anthère

anthesis The time of ßowering in a plant,

which may respond to a combination

of environmental factors such as daylength, temperature, and rainfall

anthèse anthocyanins Group of water soluble ßa-

vonoid pigments that occur in oles of leaves during the autumn afterchlorophyll is destroyed due to envi-ronmental changes Their color (e.g.,red to purple) is related to the solu-

vacu-tion acidity anthocyanines

anthracite A hard, black, lustrous coal

con-taining a high percentage of volatilematter; often called hard coal

anthracite anthric saturation A variation of soil sat-

uration associated with controlledßooding, which causes reduction inthe surface soil layer and oxidation

of mobilized iron and manganese in

a lower unsaturated subsoil

satura-tion anthrique anthropic epipedon A surface layer of

mineral soil (U.S system of soil onomy) that has the same require-

tax-ments as the mollic epipedon with

respect to color, thickness, organiccarbon content, consistence, and

anthropic soil 17 apogee

A

base saturation, but has >110 mg P

kg-1 soluble in 0.05 M citric acid, or

is dry >300 days (cumulative) during

the period when not irrigated The

anthropic epipedon forms under long

continued cultivation and

fertiliza-tion épipédon anthropique

anthropic soil A soil body that has been

constructed by human actions

Excluded are natural soils that have

been altered by humans in a

progres-sive or accidental manner sol

anthropique

anthropogenic Derived from human

activ-ities anthropogénique

antibiosis The production of an organic

compound by one species that is

toxic at low concentrations to

another species antibiose

antibiotic A substance produced by a

spe-cies of microorganism and, in dilute

solution, has the capacity to inhibit

the growth of or kill certain other

organisms antibiotique

antibody A protein produced by the

immune system in response to the

presence of an antigen which

inter-acts with that speciÞc antigen to

remove or inactivate it anticorps

anticline (geology) A fold of rock beds that

is convex upward See fold,syncline

anticlinal

antigen A substance that can initiate

pro-duction of a speciÞc antibody and is

capable of inducing an

immunologi-cal response whereby the antibody

binds to the antigen antigène

anti-oxidant An organic compound that

prevents or retards the damage

caused by oxidation to living cells,

food, and other material such as

rub-ber and plastic It acts by scavenging

free radicals generated during the

oxidation process antioxydant

antitoxin An antibody that is formed in

response to bacterial toxins or

tox-oids and can neutralize or inactivate

those toxins antitoxine

apatetic (zoology) The coloration of an

ani-mal that causes it to resemble physical

features of its habitat apatétique

apatite A group of hexagonal minerals

con-sisting of calcium phosphate togetherwith ßuorine, chlorine, hydroxyl, orcarbonate in varying amounts and

h av i n g t h e g e n e r a l f o r m u l a

Ca5(PO4,CO3)3(F,OH, Cl) Also, anymineral of this group (e.g., ßuorapa-tite, chlorapatite, hydroxylapatite,carbonate-apatite, and francolite);

when not speciÞed, the term usuallyrefers to ßuorapatite The apatite min-erals occur as accessory minerals inigneous rocks, metamorphic rocks,and ore deposits, most commonly asÞne-grained and often impure masses

as the chief constituent of phosphaterock and of bones and teeth Also

called calcium phosphate apatite

apedal Condition of a soil that has no

struc-ture, i.e., having no peds, but rather

is massive or composed of single

grains apédal

apical meristem The growing point,

com-posed of meristematic tissue, at thetip of the root or shoot in a vascular

plant See Þgure méristème apical

apogee (remote sensing) The point in the

orbit of a satellite or in a missile jectory that is farthest from the center

tra-Apical meristem adapted from Dunster and Dunster,

1996).

apparent cohesion 18 Aquerts

apparent cohesion Cohesion in granular

soils due to capillary forces

associ-ated with water cohésion apparente

apparent density See bulk density masse

volumique apparente, densité apparente

applanation (geology) Reduction of the

relief of an area, causing it tobecome more and more plain-like,including lowering of the high parts

by erosion and raising of the lowparts by the addition of material

aplanissement

approximate original contour (land

rec-lamation) The surface conÞguration

achieved by backÞlling and grading

of mined areas so that the reclaimedarea, including any terracing or accessroads, closely resembles the generalsurface conÞguration of the land prior

to strip mining and blends into andcomplements the drainage pattern of

the surrounding terrain

conÞgura-tion approximative d'origine

apron (geology) An extensive, blanket-like

accumulation of alluvial, glacial, orother unconsolidated material com-monly formed at the base of a moun-

tain or in front of a glacier plaine

d’épandage aqua regia A mixture of one part concen-

trated nitric acid and three parts centrated hydrochloric acid It is apowerful oxidizing mixture and willdissolve all metals (except silver),including gold and platinum, hence

con-the name (“royal water”) eau régale

Aqualfs A suborder in the U.S system of

soil taxonomy AlÞsols that are

satu-rated with water for periods longenough to limit their use for mostcrops other than pasture or woodlandunless they are artiÞcially drained

Aqualfs have mottles, nese concretions, and gley colorsimmediately below the A horizon

iron-manga-and gray colors in the argillic

hori-zon Aqualfs

Aquands A suborder in the U.S system

of soil taxonomy Andisols that are

saturated with water for periodslong enough to limit their use formost crops other than pastureunless they are artiÞcially drained.Aquands have low chromas inredox depletions or on ped faces

Aquands aquatic Related to environments that con-

tain liquid water aquatique

aquatic plant A plant other than algae,

growing in or near water, with true

roots, stems, and leaves plante

aquatique Aquents A suborder in the U.S system of

soil taxonomy Entisols that are urated with water for periods longenough to limit their use for mostcrops other than pasture unless theyare artiÞcially drained Aquents havelow chromas or distinct mottleswithin 50 cm of the surface, or aresaturated with water at all times

sat-Aquents aqueous (1) Of or pertaining to water (2)

Made from or with water (e.g., ous solutions) (3) Produced by theaction of water (e.g., aqueous sedi-

aque-ments) aqueux

aqueous solution A solution in which

water is the dissolving medium or

solvent solution aqueuse

Aquepts A suborder in the U.S system of

soil taxonomy Inceptisols that are

sat-urated with water for periods longenough to limit their use for most cropsother than pasture or woodland unlessthey are artiÞcially drained Aquepts

have either a histic or umbric epipedon

and gray colors within 50 cm of the

surface, or an ochric epipedon laid by a cambic horizon with gray col-

under-ors, or have sodium saturation of 15%

or more Aquepts

Aquerts A suborder in the U.S system of

soil taxonomy Vertisols that are urated with water for periods longenough to limit their use for most

sat-aquic 19 arctic

A

crops other than pasture and

wood-land unless they are artiÞcially

drained Aquerts have in one or more

horizons between 40 and 50 cm from

the surface, aquic conditions for

some time in most years and chromas

of two or less in 50 percent of the

pedon or evidence of active ferrous

iron Aquerts

aquic A mostly reducing soil moisture

regime nearly free of dissolved

oxy-gen due to saturation by groundwater

or its capillary fringe and occurring

at periods when the soil temperature

at 80 cm below the surface is >5°C

aquique

aquiclude (hydrology) A low-permeability

formation located above and/or below

an aquifer A formation which contains

water but cannot transmit it rapidly

enough to furnish a signiÞcant supply

to a well or spring aquiclude

aquifer A geologic formation or stratum

which contains sufÞcient saturated

permeable material to yield

signiÞ-cant quantities of water to wells and

springs formation aquifère

aquifer, conÞned Aquifer located between

two relatively impermeable layers of

material and under pressure

signiÞ-cantly greater than atmospheric

pres-sure Also called an artesian aquifer.

nappe artésienne

aquifer, unconÞned An aquifer with no

low-permeability zones between the

zone of saturation and the surface

aquifère non captive

aquifuge A geologic formation or structure

that contains no interconnected

openings or interstices and therefore

neither absorbs, holds, nor transmits

water aquifuge

aquitard (hydrology) A low-permeability

underground formation that retards

but does not prevent the ßow of water

to or from an adjacent aquifer couche

semi-perméable capacitive

Aquods A suborder in the U.S system of soil

taxonomy Spodosols that are saturated

with water for periods long enough to

limit their use for most crops other than

pasture or woodland unless they areartiÞcially drained Aquods may have

a histic epipedon, an albic horizon that

is mottled, or a duripan, mottling orgray color within or immediately

below the spodic horizon Aquods

Aquolls A suborder in the U.S system of soil

taxonomy Mollisols that are saturated

with water for periods long enough tolimit their use for most crops other thanpasture unless they are artiÞcially

drained Aquolls may have a histic

epipedon, a sodium saturation in the

upper part of the mollic epipedon of >

15% that decreases with depth, or tles or gray colors within or immedi-ately below the mollic epipedon

mot-Aquolls Aquox A suborder in the U.S system of soil

taxonomy Oxisols that have ous plinthite near the surface, or that

continu-are saturated with water sometime ing the year if not artiÞcially drained

dur-Aquox have either a histic epipedon,

or mottles or colors indicative of poor

drainage within the oxic horizon, or

both Aquox

Aquults A suborder in the U.S system of soil

taxonomy Ultisols that are saturated

with water for periods long enough tolimit their use for most crops other thanpasture or woodland unless they areartiÞcially drained Aquults have mot-tles, iron-manganese concretions, andgray colors immediately below the A

horizon and gray colors in the argillic

horizon Aquults

arable Pertaining to land suited for tillage

and cultivation of crops arable

arboretum A collection of plants, trees, and

shrubs grown for public exhibition,public enjoyment, recreation, educa-

tion, or research arboretum

arbuscule Special dendritic (highly

branched) structure formed within

root cortical cells by

endomycor-rhizal fungus See vesicular

arctic (1) The region within the Arctic

Circle (66∞ 30' N) (2) Lands north

of the 10∞C July isotherm (or that

arctic tundra 20 argillipedoturbation

A

of whichever month is warmest),provided the mean temperature forthe coldest month is not higherthan 0∞C (3) Pertaining to cold,frigid temperature, or to features,climate, vegetation, and animalscharacteristic of the arctic region

arctique

arctic tundra The grassland biome

char-acterized by permafrost

(subsur-face soil that remains frozenthroughout the year); found inAlaska, Canada, Russia, and otherregions near the Arctic Circle

toundra arctique area mining The type of mining used to

extract mineral resources close to thesurface in relatively ßat terrain

Overburden is removed in a series ofparallel trenches to allow extraction

of the resource, and the overburdenremoved from one trench is used toÞll in the adjacent trench afterremoval of the resource Also called

area strip mining exploitation

minière de surface

area source The geographic source from

which air pollution originates

source diffuse ou étendue areal Pertaining to an area aréal

areal map (geology) A geologic map

show-ing the horizontal extent and bution of rock units exposed at the

distri-surface carte de surface

Arents A suborder in the U.S system of

soil taxonomy Entisols that contain

recognizable fragments of pedogenichorizons which have been mixed bymechanical disturbance Arents arenot saturated with water for periodslong enough to limit their use for

most crops Arents

Argids A suborder in the U.S system of

soil taxonomy Aridisols that have an

argillic or a natric horizon Argids

argillaceous Pertaining to rocks or

sub-stances composed of clay minerals,

or having a notable proportion ofclay in their composition, especiallysedimentary materials such as shale

argileux

argillan (soil micromorphology) A cutan

composed dominantly of clay

miner-als argilane

argillic Pertaining to clay or clay minerals.

Argillic alteration is a process inwhich certain minerals are converted

to minerals of the clay group

argilique argillic horizon A diagnostic subsurface

illuvial horizon (U.S system of soiltaxonomy) that is characterized bythe accumulation of layer-lattice sil-icate clays The argillic horizon has

a certain minimum thicknessdepending on the thickness of thesolum, a minimum quantity of clay

in comparison with an overlying

elu-vial horizon depending on the clay

content of the eluvial horizon, andusually has coatings of oriented clay

on the surface of pores, peds, or

bridging sand grains horizon

argilique argillipedoturbation Disruption and mix-

ing of soil material caused by ing and swelling, as indicated by the

shrink-Association of arbuscular mycorrhizal fungi and soil

aggregate of a plant root The external mycelium

bears large chlamydospores (CH) Infection of the

plant can occur through root hairs or between

epider-mal cells Arbusculae at progressive stages in

devel-opment and senescence are shown (A–F), as is a

vesicle (V), and macroaggregate (M) (adapted from

Paul and Clark, 1996)

arid 21 artificial soil body

A

presence of irregular shaped,

ran-domly oriented intrusions of

dis-placed materials within the solum,

and by vertical cracks, often

contain-ing sloughed-in surface materials

argilipédoturbation

arid Pertaining to a climate in which the

limits of precipitation vary

consider-ably according to temperature

condi-tions, with an upper annual limit of

about 25 cm for cool regions and 50

cm for tropical regions Regions with

this climate lack sufÞcient moisture

for crop production without

irriga-tion See semi-arid , humid ,

aridic A soil moisture regime that has no

water available for plants for more

than half the cumulative time that the

soil temperature at 50 cm below the

surface is > 5°C, and has no period

as long as 90 consecutive days when

there is water for plants while the soil

temperature at 50 cm is continuously

> 8°C aridique

Aridisols An order in the U.S system of

soil taxonomy Mineral soils that

have an aridic moisture regime, an

o c h r i c e p i p e d o n , a n d o t h e r

pedogenic horizons but no oxic

hori-zon Aridisols

arithmetic mean (statistics) The sum of all

the values of a set of measurements

divided by the number of values in

the set, usually denoted by ; a

mea-sure of central tendency; also called

average See measure of central

aromatic compound An organic

com-pound that contains a benzene ring

in its molecules Aromatic

com-pounds have a planar ring of atoms

linked by alternate single and double

composé aromatique

Arrhenius equation An equation with the

form k = Aexp(-Ea/RT) where k is the

rate constant of a given reaction, A

represents the product of the

colli-sion frequency and the steric factor,

and Ea/RT is the fraction of collisions

with sufÞcient energy to produce a

reaction équation d’Arrhénius

artesian aquifer A water-bearing bed that

contains water under hydrostatic

pressure nappe artésienne

artesian spring A spring from which water

issues under artesian pressure, erally through a Þssure in the conÞn-ing bed that overlies the aquifer

gen-source artésienne artesian water Pertaining to ground water

under sufÞcient hydrostatic pressure

to rise above the aquifer containing

it, but not necessarily to or above the

ground surface eau artésienne

artesian well A water well drilled into a

conÞned aquifer where enoughhydraulic pressure exists for thewater to ßow to the surface, or abovethe top of the aquifer without pump-

ing Also called a ßowing well puits

artésien

arthropod (zoology) Any one of a group of

invertebrates belonging to the lum Arthropoda, characterizedchießy by jointed appendages andsegmented bodies It includes,insects, spiders, centipedes, and bee-

phy-tles arthropode

artiÞcial brine Brine produced from an

underground deposit of salt or othersoluble rock material in the process

of solution mining saumure

artiÞ-cielle

Euro-pean usage, artiÞcial manure maydenote commercial fertilizers

fumier artiÞciel, compost

artiÞcial regeneration ( s i l v i c u l t u re )

Establishing a new forest by plantingseedlings or by direct seeding (asopposed to natural regeneration)

régénération artiÞcielle artiÞcial soil body A soil body that has

been constructed by human actions(e.g., the construction of artiÞcialsequences of horizons in landreclaimed from strip-mined areas,and similar activities to build human-made soils in lands reclaimed fromthe sea) Natural soils that have been

¥

asbestos 22 atmophile elements

A altered by humans in a progressiveor accidental manner are generally

excluded sol anthropique

asbestos A white, gray, green-gray, or

blue-gray Þbrous variety of amphibole,

usually tremolite or actinolite, or ofchrysotile Blue asbestos is crocido-lite Asbestos has several industrialuses It is a hazardous air pollutant

when inhaled amiante

ascospores The spores produced by

Asco-mycetes See Þgure ascospores

aseptic Procedure that maintains sterility.

aseptique ash The residue remaining after complete

burning of combustible organic ter; consists mainly of minerals in

mat-oxidized form cendre

aspect The compass direction toward which

a slope faces orientation,

exposi-tion asphalt A dark brown to black viscous liq-

uid or low-melting solid bitumen that

consists almost entirely of carbonand hydrogen, melts between 65°Cand 95°C, and is soluble in carbondisulÞde Natural asphalt is formed

as a residual deposit by evaporation

of volatiles from oil, and is alsoobtained as a residue from the reÞn-ing of certain petroleum types

asphalte

assimilation (biology) Conversion or

incor-poration of absorbed nutrients intoprotoplasm; the uptake of food mate-rial for production of new biomass

(pollution) The ability of a body of

water to purify itself of organic

pol-lution (geology) The incorporation

into a magma of material originally

present in the wall rock; the ilated” material may be present ascrystals, including wall rock ele-ments, or as a true solution in theliquid phase of the magma Theresulting rock is called hybrid Also

“called magmatic assimilation

assim-ilation assimilation efÞciency The proportion of

energy in ingested food that is ilated into the bloodstream of an

assim-organism efÞcacité d’assimilation

assimilatory nitrate reduction C o nv e r

-sion of nitrate to reduced forms ofnitrogen, generally ammonium, forthe synthesis of amino acids and pro-

teins réduction assimilatoire des

nitrates associate, soil A non-taxonomic, carto-

graphic grouping of soils or land ments which combines related soilsinto units having similar geomorphicposition, landform, edaphic, andmechanical properties of soils (e.g.,climate, drainage, particle size), andsome similarity in the geologicalnature of the soil materials and tax-

seg-onomic classes sol associé

association A grouping or combination of

entities (ecology) A group of species

occurring in the same place because

of environmental requirements or

tolerances (soil science) A grouping

of soils based on similarities in matic or physiographic factors and

cli-soil parent materials association

associative dinitrogen Þxation A n

enhanced rate of dinitrogen Þxationresulting from a close interactionbetween a free-living diazotrophic

organism and a higher plant Þxation

associative d’azote asymmetrical Without proper proportion

of parts; unsymmetrical

(crystallog-raphy) Having no center, plane, or

axis of symmetry asymétrique

atmophile elements (1) The most typical

elements of the atmosphere (H, C,

N, O, I, He, and inert gases) (2)Elements that occur in the uncom-bined state or were concentrated in

Ascospore ascospore

atmosphere 23 atomic bond

A

the gaseous primordial atmosphere

éléments atmosphiles ou

atmo-philes

atmosphere The mixture of gases

sur-rounding the Earth The Earth’s

atmosphere consists of about 79.1%

nitrogen (by volume), 20.9%

oxy-gen, 0.036% carbon dioxide, and

trace amounts of other gases The

atmosphere can be divided into a

number of layers according to its

mixing or chemical characteristics,

generally determined by its thermal

properties (temperature), as follows

Troposphere, the layer nearest the

Earth, reaching to an altitude of

about 8 km in the polar regions and

17 km above the equator

Strato-sphere, beyond the troposphere and

reaching to an altitude of about 50

km Mesosphere, beyond the

strato-sphere and extending up to 80–90

km Thermosphere, or ionosphere,

beyond the mesosphere and

gradu-ally diminishing to form a fuzzy

bor-der with outer space Relatively little

mixing of gases occurs between

lay-ers atmosphère

atmospheric attenuation (remote

sens-ing) The reduction of radiation

inten-sity due to absorption and/or

scatter-ing of energy by the atmosphere;

usually wavelength dependent; may

affect both solar radiation traveling

to the Earth and reßected/emitted

radiation traveling to the sensor from

the Earth’s surface atténuation

atmosphérique

atmospheric pressure T h e p r e s s u r e

exerted by the weight of the

atmo-sphere on the Earth’s surface The

average pressure at sea level is

101.325 kPa pression

atmo-sphérique

atmospheric windows (remote sensing)

Those wavelength ranges where

radi-ation can pass through the

atmo-sphere with relatively little

attenua-tion; in the optical portion of the

spectrum, approximately 0.3 to 2.5,

3.0 to 4.0, 4.2 to 5.0, and 7.0 to 15.0

micrometers fenêtres

atmo-sphériques atom The smallest part of an element that

can exist as a stable entity Atomsconsist of a small dense nucleus,

made up of neutrons and protons, surrounded by electrons The chem-

ical reactions of an element are mined by the number of electrons(which is equal to the number of pro-tons in the nucleus) All atoms of agiven element have the same number

deter-of protons (the proton number) Agiven element may have two or moreisotopes, which differ in the number

of neutrons in the nucleus atome

atom percent The percentage of an atomic

species in a substance, calculatedwith reference to number of atomsrather than weight, number of mole-

cules, or other criteria pourcentage

atomique atomic absorption (AA) spectroscopy A

technique that uses the absorption oflight to measure the concentration ofgas-phase atoms Samples are usu-

ally liquids or solids and the analyte

atoms or ions must be vaporized in

a ßame or graphite furnace Theatoms absorb ultraviolet or visiblelight and make transitions to higherelectronic energy levels The analyteconcentration is determined from the

amount of absorption spectroscopie

d’absorption atomique atomic bond Attraction exerted between

atoms and ions Four types are;

metallic, ionic or polar, homopolar

or coordinate, and residual or van

der Waals Bonding may be

interme-diate between these types liaison

atomique atomic emission spectroscopy (AES)

A technique that uses quantitativemeasurement of the optical emissionfrom excited atoms to determine ana-lyte concentration Analyte atoms in

a solution are aspirated into the tation region where they are desol-vated, vaporized, and atomized by aßame, discharge, or plasma These

exci-atomic mass unit 24 aufwuchs

A high-temperature atomizationsources provide sufÞcient energy to

promote the atoms into high energylevels The atoms decay back tolower levels by emitting light Sincethe transitions are between distinctatomic energy levels, the emissionlines in the spectra are narrow Thespectra of samples containing manyelements can be very congested, andspectral separation of nearby atomictransitions requires a high-resolutionspectrometer Since all atoms in asample are excited simultaneously,they can be detected simultaneouslyusing a polychromator with multipledetectors This ability to simulta-neously measure multiple elements

is a major advantage of AES

com-pared to atomic absorption (AA)

spectroscopy spectroscopie

d’émis-sion atomique atomic mass unit A unit of mass used for

atoms and molecules; equal to 1/12

of the mass of an atom of the isotopecarbon-12 and is equal to 1.66033 x

10-27 kg unité de masse atomique

atomic number The number of protons in

the nucleus of an atom Each element

has a unique atomic number

nom-bre atomique atomic radius Half the distance between

the nuclei in a molecule consisting

of identical atoms rayon atomique

atomic waste Radioactive byproducts

pro-duced during activities such as themining and processing of radioactivematerials, fabrication of nuclearweapons, and operation of nuclear

reactors déchet atomique

atomic weight For each element, the

weighted sum of the masses of theprotons and neutrons composing theisotopes of that element Approxi-mately equal to the sum of the num-ber of protons and neutrons found in

the most abundant isotope masse

atomique atomizer An instrument used to produce a

Þne spray or mist from a liquid

atomiseur

attapulgite See palygorskite attapulgite

attenuation (1) A reduction in the

ampli-tude or energy of a signal, such asmight be produced by passagethrough a Þlter (2) A reduction in theamplitude of seismic waves, as pro-duced by divergence, reßection andscattering, and adsorption (3) Thatportion of the decrease in seismic orsonar signal strength with distancethat is not dependent on geometricaldivergence, but on the physical char-acteristics of the transmittingmedium (4) Lessening or reduction

of the virulence of microorganisms

atténuation Atterberg limits See liquid limit and plas-

attitude (1) (remote sensing) The position

of a body as determined by the nation of the axes to some frame ofreference If not otherwise speciÞed,this frame of reference is Þxed to the

incli-Earth (2) (geology) The relation of

some directional features to a rock in

a horizontal surface (1) orientation

(2) disposition attribute (1) Any property, quality, or char-

acteristic of a sampling unit Theindicators and other measures used

to characterize a sampling site orresource unit are representations ofthe attributes of that unit or site (2)

A characteristic of a map feature(point, line, or polygon) described bynumbers or text; for example,attributes of a tree represented by apoint might include height and spe-

cies (1) variable qualitative,

attribut (2) attribut attribute of soil quality Properties that

reßect or characterize a soil process

or processes that support a speciÞc

soil function attribut de la qualité

des sols

aufwuchs (liminology) Slimy aquatic

com-munity consisting of diatoms andgelatinous green and blue-green

algae attached to substrate algue

épiphytique

auger, soil 25 available water (capacity)

A

auger, soil A tool for boring into the soil

and withdrawing a small sample for

observation in the Þeld or laboratory

The different kinds of augers include

those having worm-type bits that are

unenclosed, those having worm-type

bits enclosed in a hollow cylinder,

and those having a hollow

half-cyl-inder with a cutting edge on the side

that rotates around a stabilizing vane

tarière

autecology A subdivision of ecology that

deals with the study of the relation

of an individual species or

popula-tion to its environment See

authigenic (geology) Formed or generated

in situ Rock constituents that formed

at the spot where they are now found;

minerals that came into existence at

the same time as, or later than, the

rock of which they constitute a part

See autochthonous authigène

autocatalysis Catalysis in which one of the

products of the reaction is a catalyst

for the reaction autocatalyse

autochthonous (1) Native, or indigenous,

to a locale; the opposite of

allochth-onous (2) Used to describe soil

microorganisms that have the ability

to grow under low nutrient supply

They are thought to subsist on the

more resistant organic matter and are

little affected by the addition of fresh

organic materials autochtone

autochtonous peat Peat formed in situ.

autochtone

autoclave A chamber in which steam under

pressure is used to sterilize objects

and solutions autoclave

autocorrelation (statistics) The internal

cor-relation (cor-relationship) between

ele-ments of a stationary time series;

usu-ally expressed as a function of the time

lag between observations See

autolysis Self-destruction of cells by the

action of autolytic or intracellular

enzymes, resulting in cellular death

autolyse

autopoiesis The organizing principle of

life by which an entity’s boundarystructure (e.g., cell membrane), pro-cesses of metabolism, and energyexchange are determined by its inter-nal organization and the interchangewith its immediate surroundings

autopoièse autotoxic Chemicals that may be detrimen-

tal to individuals of the species that

make the chemical autotoxique

autotroph An organism that manufactures

its own food from inorganic pounds (e.g., carbon dioxide) in theenvironment, obtaining energy from

com-light (photoautotroph) or another ganic compounds (chemautotroph).

autotrophic nitriÞcation O x i d a t i o n o f

ammonium to nitrate through the

combined action of two

chemoau-totrophic organisms, one forming

nitrite from ammonium and the other

oxidizing nitrite to nitrate

nitriÞca-tion autotrophe autotrophy Self-production of food and

Þxation of energy by green plantsand some bacteria See heterotrophy

autotrophie auxin A hormone that promotes the longi-

tudinal growth in the cells of higherplants by increasing the rate of cellelongation rather than the rate of celldivision; produced at the growingpoints of stems and roots andinvolved in the curvature of plantparts towards light or gravity Syn-thetic auxins are used as herbicides

auxine

available moisture See available water.

eau disponible available nutrient The amount of a nutri-

ent element or compound in the soilthat can be readily absorbed and

assimilated by growing plants

élé-ment assimilable available water (capacity) The amount of

water released between in situ Þeld

capacity and the permanent wilting point (usually estimated by water

average 26 azonal soil

A content at soil matric potential of–1.5 MPa) eau disponible

Avogadro’s law Equal volumes of gases at

the same temperature and pressurecontain the same number of mole-

cules loi d’Avogadro

Avogadro’s constant The number of atoms

or molecules in a mole of a stance, equal to 6.022 x 1023 con-

sub-stante d’Avogadro axenic A system in which all biological

populations are deÞned, such as a

pure culture axénique

azimuth The horizontal angle or bearing of

a point measured from the true(astronomic) north Used to refer to

a compass on which the movable dial(used to read direction) is numbered

in 360∞ See bearing azimut

azonal soil Soil without distinct genetic

horizons Such soils may have Chernozemic Ah horizons or thinChernozemic Ah horizons, and lack

non-B horizons In Canada, they are

included in the Regosolic order sol

azonal

crystal-is oriented horizontally, right to left.

by one of the following: an ment in clay, iron, aluminum, orhumus (Bt or Bf); a prismatic orcolumnar structure that exhibits pro-nounced coatings or stainings asso-ciated with signiÞcant amounts ofexchangeable sodium (Bn or Bnt); analteration by hydrolysis, reduction,

enrich-or oxidation to give a change in colenrich-or

or structure from the horizons above

or below, or both (Bm) Other typesand combinations of types of B hori-zons include: Bg, Bfg, Btg, (charac-terized by gleying); Bmk (character-ized by presence of carbonate); Bs,Bsa (presence of salts); Bss (pres-ence of slickensides); Bv (character-ized by argillipedoturbation); By(affected by cryoturbation); andBmz (a frozen Bm) The above hori-zon terms are according to the Cana-dian system of soil classiÞaction See

Taxonomy and FAO soils ogy See A horizon , C horizon , hori-

present (day)” (as opposed to BC) It

is used in geochronology, especially

in carbon dating of the later nary period BP, avant le présent

spe-ciÞc physiologic characteristics

bacille

recy-clable materials from incinerator ash

(in a solid waste resource recoveryoperation). système de récupéra- tion

back furrow See tillage, back furrow ados backÞll (land reclamation) (1) The place-ment of spoils (waste soil and rock)

in the notches cut in the hills, andrestoration of the original slope Thisprocess reduces soil erosion andallows for the re-establishment ofvegetation (2) The operation of reÞll-ing an excavation Also, the materialplaced in an excavation in the process

of backÞlling remblayer, remblai

radio-activity of the environment, due tocosmic rays and the Earth's naturallyradioactive substances (2) The range

in values representing the normalconcentration of a given element in

a material under investigation, such

as rock, soil, plants, and water (3)The amount of pollutants present inthe ambient air owing to naturalresources bruit de fond, bruit

chemis-try) Samples that do not contain the

analyte of interest (blank) and thatare subjected to steps of the analyti-cal procedure (e.g., reagents, glass-ware, preparations, and analyticalinstrumental) to account for the pres-ence of spurious analytes, interfer-ences, and background concentra-tions of the analyte of interest

échantillons de référence, lons témoins

reßected back toward the source; theopposite of forward scatter; alsocalled backscattering rétrodiffu- sion

3115_book Page 27 Tuesday, August 12, 2003 11:25 AM

backslope 28 banding

B

out-side a river channel’s levee on a ßood plain dépression latérale humide

water in a direction opposite(upward) to the normal ßow of rawwater through rapid sand Þlters toclean the Þlters, in a water treatmentfacility. lavage à contre-courant, lavage par retour d’eau, nettoyage inversé

bacterium (plural bacteria) S i n g l e - c e l l

microorganism that lacks chlorophyll

and an evident nucleus; may be obic, anaerobic, or facultative; somebacteria can cause disease See Þg- ure bactérie

quan-tifying the number of bacteria in asample of solid or liquid substance

The sample is mixed and/or dilutedwith a suitable sterile diluent, and ameasured, small portion of the mix-ture is placed on the surface of a solidsubstrate suitable for the growth ofbacteria (a medium) Following incu-bation, the number of bacterial colo-nies that have grown on the medium

is counted, and the necessary ematical estimations are made on theassumption that each colony repre-sents one bacterium that was present

math-in the origmath-inal sample numération bactérienne sur plaque

bactericidal Able to kill bacteria cide

bac-teria and causes lysis of bacbac-terialcells bactériophage

bacteriostatic A substance inhibitory tobacterial growth but not necessarilylethal If a bacteriostatic material dis-sipates or lowers in concentration,bacterial growth may resume

bactériostatique

certain bacteria Refers particularly

to the swollen, vacuolated cells of

Rhizobium and Bradyrhizobium inlegume nodules bactérọde

vegetation and broken by an intricatemaze of narrow ravines, sharp crests,and pinnacles resulting from severeerosion of soft geologic materials.Badlands occur most commonly inarid or semiarid regions badland

juice is extracted from sugar cane orsugar beets bagasse

sepa-rates inorganic from organic matter

in a composting process séparateur par projection

en bandes band-elimination Þlter (remote sensing)

A wave Þlter that attenuates one quency band, neither the critical norcutoff frequencies being zero or inÞ-nite Þltre à élimination de bande, Þltre coupe-bande

fre-banding (geology) (1) A pattern of ing layers in igneous or metamorphicrock that differ in color or texture andmay or may not differ in mineral com-position (2) Thin bedding in sedi-mentary rocks consisting of differentmaterials in alternating layers, andconspicuous in cross-section (3)(agronomy) A method of applying fer-tilizers or agrichemicals above, below,

alternat-or alongside the planted seed row.Refers to either the placement of fer-tilizers close to the seed at planting or

A soil bacterium (adapted from Killham, 1994).