ISO/DTS 18721
(Main)Ecological soil functions — Characteristics, indicators and methods
Ecological soil functions — Characteristics, indicators and methods
This standard provides generic guidance on how core Ecological Soil Functions (ESF) can be evaluated in different contexts of land use and management (e.g. agricultural, forest or contaminated lands) for environmental monitoring. Ecological soil functions can be assessed the same way no matter which soil use is being considered. For each ESF, the standard specifically proposes biotic and abiotic parameters to be measured and associated indicators. It focuses on parameters and indicators that are either available as ISO standards or published in peer reviewed papers. This document does not apply to non-ecological soil functions such as geotechnical functions (foundation support for buildings, tunnels, etc.) or geothermal functions. Methods based on proxy indicators (e.g. soil occupation, hydrography parameters) are not included in this standard.
Fonctions écologiques du sol — Caractéristiques, indicateurs et méthodes
General Information
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FINAL DRAFT
Technical
Specification
ISO/TC 190
Ecological soil functions —
Secretariat: DIN
Characteristics, indicators and
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methods
2025-11-21
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Reference number
FINAL DRAFT
Technical
Specification
ISO/TC 190
Ecological soil functions —
Secretariat: DIN
Characteristics, indicators and
Voting begins on:
methods
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© ISO 2025
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Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Indicators of ecological soil functions . 1
4.1 General .1
4.2 Methods for measuring general soil characteristics and indicators, sampling and soil
preparation .4
4.3 Methods for measuring specific soil characteristics and indicators .7
Bibliography .15
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO’s adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 190, Soil quality.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
In recent years, the concern for soil sustainability has considerably increased. Many countries are setting
targets to reduce soil artificialisation and reinforce ecosystem rehabilitation and biodiversity conservation.
In Europe, the recent proposal for a directive on soil monitoring and resilience will set foundations for
member states to consider.
[86][97][98]
In this context, concepts of soil health and soil quality are being discussed and ecological soil
[87][90]
functions are being proposed . However, although several promising propositions have been made to
define lists of indicators of soil health and soil quality in different contexts (e.g. Reference [94]), there is
presently no consensus.
Based on the definitions of soil health and soil quality presented in ISO/TS 18718, this document aims to
provide an overview of the existing indicators and characteristics that are linked to soil functions and the
available methods to assess them whether they are internationally standardized, nationally standardized or
exist as peer-reviewed work.
Figure 1 — Links between ISO/TS 18718 and this document (ISO/TS 18721) on the soil functions
and related ecosystem services
v
FINAL DRAFT Technical Specification ISO/DTS 18721:2025(en)
Ecological soil functions — Characteristics, indicators
and methods
1 Scope
This document provides a generic description of the methods available for measuring soil characteristics and
indicators of core ecological soil functions. No distinction of context is made, i.e. no differentiation of land
use and management (e.g agricultural, forest, urban, natural or contaminated lands). For each ecological soil
function, the document specifically lists biotic and abiotic characteristics that can be measured. It focuses on
characteristics and indicators that are either available as ISO documents or published in peer-reviewed papers.
This document applies to ecological soil functions and is not applied to soil functions such as geotechnical
functions (foundation support for buildings, tunnels, etc.) or geothermal functions. Indeed, ecosystem
services do not address soils without a topsoil, or with a covered topsoil (buildings, infrastructure,
greenhouse farming, solar panel parks).
Methods and indicators for ecological soil functions can help in the assessment of soil-related ecosystem
services but the overall assessment of ecosystem services is not covered in this document.
Other methods based on proxy indicators (e.g. soil occupation, hydrography parameters) can also be used
for land planning at large scale. These indicators are not included in this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 11074, Soil quality — Vocabulary
ISO/TS 18718, Soil functions and related ecosystem services — Definitions, descriptions and conceptual
1)
framework
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11074 and ISO/TS 18718 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Indicators of ecological soil functions
4.1 General
Soil functions are one or a combination of soil processes that drive the dynamics of the ecosystem structure
or composition (see Table 1). Each function can be divided into different sub-functions (see Table 1). Soil
1) Under preparation. Stage at the time of publication: ISO/DTS 18718.
processes are the interactions among physical, chemical and biological soil components underlying soil
functions.
Table 1 details soil functions and illustrates how these functions and sub-functions are influenced and
connected to either biological or physico-chemical processes or both. Further descriptions of each function
and sub-function are provided in ISO/TS 18718.
Table 1 — Soil functions and underling processes
Biological processes Physico-chemical processes
Soil function Sub-function
(examples) (examples)
Water retention by soil texture
Bioturbation, aggregation,
Water retention and organic matter (adsorption,
Water regulation,
fragmentation
retention)
retention and
release
Infiltration and Macropore formation, root foraging,
Diffusion
percolation bioturbation, aggregation
Biotic fragmentation, microbial
Fragmentation linked to climate
Decomposition grazing, microbial respiration,
conditions
Organic matter
methanogenesis
storage,
Resource Aggregation, bioturbation, exudation,
transformation Leaching, adsorption
reallocation food web assimilation
and recycling
Biochemical Methanotrophy, nitrification,
Leaching, adsorption
transformation denitrification
Fragmentation of litter,
Fragmentation of rocks
mineralization,
Nutrient (e.g. frost/thaw), physical and
nitrogen transformations,
transformation chemical weathering of rocks,
sulfur transformation,
precipitation, dissolution
biochemical weathering
Adsorption/desorption, atmos-
Nutrient cycling
Nutrient pheric deposition, precipitation/
Aggregation, bioturbation
reallocation dissolution, erosion/run-off,
leaching, N volatilization
Food web assimilation, mycorrhizal
Nutrient
acquisition, nitrogen fixation, root
assimilation
uptake
Biosorption, bioassimilation,
Retention Sorption, complexation, …
bioaccumulation
Contaminant
retention, Photodegradation,
Transformation Biotransformation
transformation oxido-reduction
and degradation
Photodegradation,
Degradation Biodegradation, mineralization
oxido-reduction
Organismal activity (e.g. respiration,
Emission nitrous oxide and methane Diffusion, exchange
Gas exchanges with
production)
atmosphere
Organismal activity (e.g. nitrogen
Captation Diffusion, exchange
fixation, methane consumption)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Biological processes Physico-chemical processes
Soil function Sub-function
(examples) (examples)
Abiotic conditions (e.g. moisture
Biotic foraging (e.g. plants,
and temperature, pH, organic
earthworms)
matter, porosity, …)
Abundance, diversity and activity of
soil biota
Habitat provision
Interactions/networks as antibiosis,
competition and invasive
alien species, predation,
parasitism, microbial grazing
Resistance and defence, plant
metabolism enhancement
Abiotic aggregation (texture,
Inherent soil Aggregation linked to biological
stone and OM content, pH), ero-
stability activity
sion (water and wind), lixiviation
Physical stability
Macropore formation, bioturbation,
Stability evolution Freeze-thaw alternation
roots
Soil is a very complex ecosystem of which the functioning and thus ecosystem service provision relies on
interactions between the abiotic and biotic components. This document proposes to separate general soil
characteristics and indicators, which need to be measured as they influence soil processes, from specific
ones, which directly reflect soil processes. This organisation is presented in Figure 2.
Figure 2 — Differentiation between general soil characteristics and specific soil characteristics
Many methods have been developed to measure these characteristics and indicators. Among these
methods, some are normalized and applicable worldwide while others are based on normalized methods
but applicable only at a sub-worldwide scale. Finally, emerging approaches are available and used in the
scientific literature but are not yet normalized or do not yet dispose of an interpretation referential. These
two levels of standardization are considered here and are so after named:
— Level 1: Standardized methods applicable worldwide (ISO);
— Level 2: Standardized methods applicable or standardized at a sub-worldwide scale (proxies or
modelling) or emerging methods not yet standardized or without an interpretation reference (scientific
literature).
4.2 Methods for measuring general soil characteristics and indicators, sampling and soil
preparation
General soil characteristics reflect the physico-chemical composition of soils and give a first assessment
of a sample. Some are required to interpret specific soil characteristics and indicators. General soil
characteristics and indicators include texture, soil depth, soil density, pH (acidity), cation exchange capacity
(CEC), cations (Ca, K, Mg, Na), total carbon, nitrogen and phosphorus, the amount of coarse elements, calcium
carbonate (CaCO ,), and the presence of contaminants. The assessment of all or part of these characteristics
is a pre-requisite for assessing soil processes and should be carried out.
Moreover, assessing general soil characteristics or specific characteristics requires representative sampling
[1-7]
and soil preparation before analysis (see the ISO 18400 series ).
The existing methods for measuring general soil characteristics are presented in Table 2 according to their
level of standardization.
Table 2 — Existing methods to measure general soil characteristics and indicators
General soil
characteristics and Level 1 Level 2
indicators
a) Soil texture (particle ISO 11277, Soil quality — Determination of particle size distribu- Adaptation of ISO 13320, Particle size analysis — Laser diffraction
[9]
size distribution) tion in mineral soil material — Method by sieving and sedimenta- methods for the measurement of soil texture (REFS)
[8]
tion
[10] [96]
b) Bulk density ISO 11272, Soil quality — Determination of dry bulk density Pedotransfer functions (Reference )
NF X 31-501, Soil quality - Physical methods - Measuring of the bulk
[11]
density of an undisturbed soil sample - Cylinder method
ISO 10390, Soil, treated biowaste and sludge — Determination of
c) pH (acidity)
[12]
pH
d) Cation exchange ISO 23470, Soil quality — Determination of effective cation ex-
capacity (CEC) change capacity (CEC) and exchangeable cations using a hexammi-
[13]
necobalt(III)chloride solution
ISO 11260, Soil quality — Determination of effective cation ex-
change capacity and base saturation level using barium chloride
[14]
solution
[93]
e) Soil structure and ISO 10930, Soil quality — Measurement of the stability of soil ag- Spade-test: Visual evaluation of soil structure (Reference )
[15]
[105]
stability gregates subjected to the action of water
Mini 3D soil profile (Tomis et al. 2019)
[92]
Slake test (Reference )
[95]
Aggregate stability (Reference )
[101]
Visual Soil Assessment (Reference )
[85]
Profil cultural (Reference )
f) Exchangeable cations ISO 23470, Soil quality — Determination of effective cation ex-
+ + + +
(Ca , K , Mg , Na ) change capacity (CEC) and exchangeable cations using a hexammi-
[13]
necobalt(III)chloride solution
ISO 11260, Soil quality — Determination of effective cation ex-
change capacity and base saturation level using barium chloride
[14]
solution
g) Organic carbon ISO 10694, Soil quality — Determination of organic and total car- Rock-Eval pyrolysis combined with PartySOC model (Reference [89])
[16]
(organic matter) bon after dry combustion (elementary analysis) for assessing stable and active fractions of total organic carbon in
temperate ecosystems
ISO 17184, Soil quality - Determination of carbon and nitrogen by
[17]
near-infrared spectrometry (NIRS) NF X 31-516, Soil Quality - Granulo-densimetric fractionation of soil
[18]
organic particulate material in water
h) Carbonates ISO 10693, Soil quality — Determination of carbonate content —
[19]
Volumetric method
Table 2 (continued)
General soil
characteristics and Level 1 Level 2
indicators
[100]
i) Contaminants ISO 54321, Soil, treated biowaste, sludge and waste — Digestion of Pesticide Multi-residue method (Reference )
[20]
(depending on the aqua regia soluble fractions of elements
context)
ISO 11504, Soil quality — Assessment of impact from soil contami-
[21]
nated with petroleum hydrocarbons
ISO 21268-1, Soil quality — Leaching procedures for subsequent
chemical and ecotoxicological testing of soil and soil-like materi-
als — Part 1: Batch test using a liquid to solid ratio of 2 l/kg dry
[22]
matter
ISO 21268-2, Soil quality — Leaching procedures for subsequent
chemical and ecotoxicological testing of soil and soil-like materi-
als — Part 2: Batch test using a liquid to solid ratio of 10 l/kg dry
[23]
matter
ISO 21268-3, Soil quality — Leaching procedures for subsequent
chemical and ecotoxicological testing of soil and soil-like materi-
[24]
als — Part 3: Up-flow percolation test
ISO 21268-4, Soil quality — Leaching procedures for subsequent
chemical and ecotoxicological testing of soil and soil-like materi-
als — Part 4: Influence of pH on leaching with initial acid/base
[25]
addition
ISO 17402, Soil quality — Requirements and guidance for the selec-
tion and application of methods for the assessment of bioavailability
[26]
of contaminants in soil and soil materials
ISO 16198, Soil quality — Plant-based test to assess the environ-
[27]
mental bioavailability of trace elements to plants
j) Dry matter ISO 11465, Sludge and solid environmental matrices — Determina-
tion of dry residue or water content and calculation of the dry matter
[28]
fraction on a mass basis
Required for the physico-chemical analysis, it allows calculation of
element concentration in the dry matter
k) Total N ISO 13878, Soil quality — Determination of total nitrogen content
[29]
by dry combustion (“elemental analysis”)
l) Total P ISO 11263, Soil quality — Determination of phosphorus — Spec-
trometric determination of phosphorus soluble in sodium hydrogen
[30]
carbonate solution
4.3 Methods for measuring specific soil characteristics and indicators
Soil processes are linked to soil sub-functions and functions as described in ISO/TS 18718. To assess soil
processes, many methods exist to measure specific soil characteristics and indicators. As for general soil
characteristics, these are standardised at different levels.
Some of the methods are direct measurements of a function or sub-function whereas others are indirect. For
example, microbial biomass is an indirect indicator of organic matter mineralisation potential whereas soil
respiration is a direct measurement.
Tables 3, 4 and 5 are organised as follows: in Table 3, soil functions and sub-functions are linked to soil
characteristics and indicators reflecting soil processes. Tables 4 and 5 further link the soil functions with
the characteristics and indicators at level 1 and level 2, respectively, and provide references.
Table 3 — Specific soil characteristics and indicators reflecting soil processes associated to soil functions and sub-functions
Specific soil characteristics and indicators Specific soil characteristics and indicators
Functions Sub-functions
a b
associated to level 1 methods associated to level 2 methods
L1-C1. Total organic carbon content
SF1-Water retention
F1 - Water
L1-C2. Water retention
regulation,
L2-C1. Soil structure assessment via X-ray computed
retention and
tomography
SF2-Infiltration and percolation L1-C3. Permeability
release
L2-C10. Permeability
L1-C4. Microbial soil biomass L2-C2. Organic matter mineralisation in soil
SF3-Decomposition
L1-C5. Feeding activity L2-C3. Litter bag
F2 - Organic matter
SF4-Resource reallocation L1-C1. Total organic carbon content
storage,
L2-C4. Carbon quality – active and stable organic
transformation
L1-C1. Total organic carbon content
carbon
and recycling
SF5-Biochemical transformation
L1-C6. Microbial respiration (carbon mineraliza-
L2-C5. Functional diversity: Genes coding analysis
tion)
L2-C6. Microbial catabolic activities
L1-C4. Microbial soil biomass
L1-C7. Enzymatic activities
SF6-Nutrient transformation L2-C7. Microbial catabolic activities
L1-C8. Total nitrogen content
L1-C9. Assimilable phosphorus content
F3 - Nutrient cycling
L1-C10. CEC and exchangeable cations
SF7-Nutrient reallocation L2-C11. CEC and exchangeable cations
L1-C7. Enzymatic activities
L2-C8. Microbial activities (denitrification)
SF8-Nutrient assimilation L1-C11. Available NO and NO
2 3
L2-C5. Functional diversity: Genes coding analysis
L1-C12. Bioavailability of metal contaminants.
SF9-Retention
L1-C13. Total and extractable metal trace element
F4 - Contaminants
SF10-Transformation L2-C6. Microbial catabolic activities
retention,
transformation
L1-C7. Enzymatic activities
a
and degradation
SF11-Degradation L1-C14. Soil microbial diversity L2-C6. Microbial catabolic activities
L1-C15. Degradation of organic chemicals
SF12-Emission L2-C6. Microbial catabolic activities
F5 - Gas exchanges
L2-C4. Carbon quality – active and stable organic
with the atmosphere
SF13-Captation
carbon
Table 3 (continued)
Specific soil characteristics and indicators Specific soil characteristics and indicators
Functions Sub-functions
a b
associated to level 1 methods associated to level 2 methods
L1-C1. Total organic carbon content
L2-C4. Carbon quality – active and stable organic
L1-C4. Microbial soil biomass carbon
L1-C16. Ecotoxicological quality L2-C1. Soil structure assessment via X-ray computed
F6 - Habitat
tomography
L1-C17. Effect of chemicals macrofauna
provision
L1-C14. Abundance and diversity of microbial
L2-C8. Taxonomic diversity (bacteria and fungi)
L1-C18. Abundance and diversity of soil inverte-
L2-C9. Fungal, bacterial ratio
brates
L2-C1. Soil structure assessment via X-ray computed
SF16-Inherent soil stability
tomography
F7 - Physical
Salinisation requires:
L2-C1. Soil structure assessment via X-ray computed
stability
tomography
SF17-Stability evolution L1-C16. Electrical conductivity
L2-C11. CEC and exchangeable cations
L1-C10. CEC and exchangeable cations
a
Level 1 methods are provided in Table 4.
b
Level 2 methods are provided in Table 5.
Table 4 — References and description of level 1 specific soil characteristics and indicators
Specific soil
Related
characteristics Description and references
functions
and indicators
[31]
ISO 23400, Guidelines for the determination of organic carbon and nitrogen stocks and their variations in mineral soils at field scale
L1-C1. Total F1-SF1;
[16]
organic carbon F2-SF5; ISO 10694, Soil quality — Determination of organic and total carbon after dry combustion (elementary analysis)
[17]
content F5-SF11
ISO 17184, Soil quality — Determination of carbon and nitrogen by near-infrared spectrometry (NIRS)
L1-C2. Water
[32]
F1-SF1 ISO 11274, Soil quality — Determination of the water-retention characteristic — Laboratory methods
retention
[33]
L1-C3. Permeability F1-SF2 ISO 17892-11, Geotechnical investigation and testing — Laboratory testing of soil — Part 11: Permeability tests
[34]
ISO 14240-1, Soil quality — Determination of soil microbial biomass — Part 1: Substrate-induced respiration method
[35]
ISO 14240-2, Soil quality — Determination of soil microbial biomass — Part 2: Fumigation-extraction method
[36]
ISO 16072, Soil quality — Laboratory methods for determination of microbial soil respiration
[37]
ISO 17155, Soil quality — Determination of abundance and activity of soil microflora using respiration curves
[38]
F2-SF3;
ISO 11063, Soil quality — Direct extraction of soil DNA
L1-C4. Microbial
F3-SF6;
ISO 17601, Soil quality — Estimation of abundance of selected microbial gene sequences by quantitative polymerase chain reaction
soil biomass
F6-SF14
[39]
(qPCR) from DNA directly extracted from soil
ISO/TS 29843-1, Soil quality — Determination of soil microbial diversity - Part 1: Method by phospholipid fatty acid analysis (PLFA)
[40]
and phospholipid ether lipids (PLEL) analysis
ISO/TS 29843-2, Soil quality — Determination of soil microbial diversity — Part 2: Method by phospholipid fatty acid analysis (PLFA)
[41]
using the simple PLFA extraction method
...
Sept 10, 2025
ISO/TC 190
Secretariat: DIN
Date: 2025-11-06
Ecological soil functions – — Characteristics, indicators and methods
DTS stage
Warning for WDs and CDs
This document is not an ISO International Standard. It is distributed for review and comment. It is subject to change
without notice and may not be referred to as an International Standard.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which
they are aware and to provide supporting documentation.
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. Phone: + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
www.iso.org
iii
Contents
Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Indicators of ecological soil functions . 1
4.1 General . 1
4.2 Methods for measuring general soil characteristics and indicators, sampling and soil
preparation . 4
4.3 Methods for measuring specific soil characteristics and indicators . 8
Bibliography . 18
iv
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawnISO draws attention to the possibility that some of the elementsimplementation of this
document may beinvolve the subjectuse of (a) patent(s). ISO takes no position concerning the evidence,
validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this
document, ISO had not received notice of (a) patent(s) which may be required to implement this document.
However, implementers are cautioned that this may not represent the latest information, which may be
obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for
identifying any or all such patent rights. Details of any patent rights identified during the development of the
document will be in the Introduction and/or on the ISO list of patent declarations received (see ).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation onof the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO'sISO’s adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT)), see
www.iso.org/iso/foreword.htmlthe following URL: .
This document was prepared by Technical Committee ISO/TC 190, Soil quality, Working Group WG 3,
Assessment of soil functions/ecosystem services.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
Introduction
In recent years, the increasing concern for soil sustainability has considerably risenincreased. Many countries
are setting targets to reduce soil artificialisation and reinforce ecosystem rehabilitation and biodiversity
conservation. In Europe, the recent proposal for a Directivedirective on Soilsoil monitoring and resilience will
set foundations for member states to consider.
[ ][ ][
In this context, concepts of soil health and soil quality are being discussed 86 97 98 (Kibblewhite et al., 2008;
] [ ][
Jenzen et al., 2021; Bonfante et al., 2020) and ecological soil functions are being proposed 87 90 (Bünemann
]
et al., 2018; Creamer et al., 2022). . However, although several promising propositions have been made to
define lists of indicators of soil health and soil quality in different contexts (e.g. Reference [94de Haan et al.,
2021),]), there is presently no consensus.
Based on the definitions of soil health and soil quality presented in ISO/TS 18718, this document aims to
provide an overview of the existing indicators and characteristics that are linked to soil functions and the
available methods to assess them whether they are internationally standardized, nationally standardized or
exist as peer-reviewed work.
vi
Figure 1 — Links between ISO/TS 18718 and this document (ISO/TS 18721) on the soil functions and
related -ecosystem services
vii
Ecological soil functions – — Characteristics, indicators and methods
1 Scope
This document provides a generic description of the methods available for measuring soil characteristics and
indicators of core ecological soil functions. No distinction of context is made;, i.e. no differentiation of land use
and management (e.g agricultural, forest, urban, natural or contaminated lands). For each ecological soil
function, the document specifically lists biotic and abiotic characteristics that can be measured. It focuses on
characteristics and indicators that are either available as ISO documents or published in peer-reviewed
papers.
This document applies to ecological soil functions and is not applied to soil functions such as geotechnical
functions (foundation support for buildings, tunnels, etc.) or geothermal functions. Indeed, ecosystem services
do not address soils without a topsoil, or with a covered topsoil (buildings, infrastructure, greenhouse farming,
solar panel parks).
Methods and indicators for ecological soil functions can help in the assessment of soil-related ecosystem
services but the overall assessment of ecosystem services is not covered in this document.
Other methods based on proxy indicators (e.g. soil occupation, hydrography parameters) can also be used for
land planning at large scale. These indicators are not included in this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies *.
ISO 11074 (2025), Soil quality — Vocabulary
ISO/TS 18718, Soil functions and related -ecosystem services - — Definitions, descriptions and conceptual
1)
framework
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11074 and ISO/TS 18718 apply.
ISO and IEC maintain terminologicalterminology databases for use in standardization at the following
addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
4 Indicators of ecological soil functions
4.1 Introduction
4.1 General
Soil functions are one or a combination of soil processes that drive the dynamics of the ecosystem structure
or composition (see Table 1Table 1).). Each function can be divided into different sub-functions (see
1)
Under preparation. Stage at the time of publication: ISO/DTS 18718.
Table 1Table 1).). Soil processes are the interactions among physical, chemical and biological soil components
underlying soil functions.
Table 1Table 1 details soil functions and illustrates how these functions and sub-functions are influenced and
connected to either biological or physico-chemical processes or both. A further descriptionFurther
descriptions of each function and sub-function are provided in ISO/TS 18718.
Table 1 — Soil functions and underling processes
Soil Biological processes Physico-chemical processes
Sub-function
functionsfunction (examples) (examples)
Water retention by soil texture
Bioturbation, aggregation,
Water retention and organic matter (adsorption,
Water regulation,
fragmentation
retention)
retention and
release
Infiltration and Macropore formation, root foraging,
Diffusion
percolation bioturbation, aggregation
Biotic fragmentation, microbial
Fragmentation linked to climate
Decomposition grazing, microbial respiration,
conditions
methanogenesis
Organic matter
storage,
Resource Aggregation, bioturbation, exudation,
transformation Leaching, adsorption
reallocation foodwebfood web assimilation
and recycling
Biochemical Methanotrophy, nitrification,
Leaching, adsorption
transformation denitrification
Fragmentation of litter,
Fragmentation of rocks
mineralization,
Nutrient (e.g. frost/thrawthaw), physical
nitrogen transformations,
transformation and chemical weathering of
sulfur transformation,
rocks, precipitation, dissolution
biochemical weathering
Adsorption/desorption,
Nutrient cycling atmospheric deposition,
Nutrient
Aggregation, bioturbation precipitation/dissolution,
reallocation
erosion/run-off, leaching,
N volatilization
FoodwebFood web assimilation,
Nutrient
mycorrhizal acquisition, nitrogen
assimilation
fixation, root uptake
Biosorption, bioassimilation,
Retention Sorption, complexation, …
bioaccumulation
Contaminant
retention, Photodegradation,
Transformation Biotransformation
transformation oxido-reduction
and degradation
Photodegradation,
Degradation Biodegradation, mineralization
oxido-reduction
Organismal activity (e.g. respiration,
Emission nitrous oxide and methane Diffusion, exchange
Gas exchanges with
production)
atmosphere
Organismal activity (e.g. nitrogen
Captation Diffusion, exchange
fixation, methane consumption)
Abiotic conditions (e.g. moisture
Biotic foraging (e.g. plants,
Habitat provision and temperature, pH, organic
earthworms)
matter, porosity, …)
Soil Biological processes Physico-chemical processes
Sub-function
functionsfunction (examples) (examples)
Abundance, diversity and activity of
soil biota
Interactions/networks as antibiosis,
competition and invasive
alien species, predation,
parasitism, microbial grazing
Resistance and defensedefence, plant
metabolism enhancement
Abiotic aggregation (texture,
Inherent soil Aggregation linked to biological stone and OM content, pH),
stability activity erosion (water and wind),
Physical
lixiviation
Stabilitystability
Macropore formation, bioturbation,
Stability evolution Freeze-thaw alternation
roots
Soil is a very complex ecosystem of which the functioning and thus ecosystem service provision relies on
interactions between the abiotic and biotic components. This document proposes to separate general soil
characteristics and indicators, which need to be measured as they influence soil processes, from specific ones,
which directly reflect soil processes. This organisation is presented in Figure 2Figure 2. .
Figure 2 — Differentiation between general soil characteristics and specific soil characteristics.
Many methods have been developed to measure these characteristics and indicators. Among these methods,
some are normalized and applicable worldwide while others are based on normalized methods but applicable
only at a sub-worldwide scale. Finally, emerging approaches are available and used in the scientific literature
but are not yet normalized or do not yet dispose of an interpretation referential. These two levels of
standardization are considered here and are so after named:
— Level 1: Standardized methods applicable worldwide (ISO);
— Level 2: Standardized methods applicable or standardized at a sub-worldwide scale (proxies or
modelling) or emerging methods not yet standardized or without an interpretation reference (scientific
literature).
4.2 Methods for measuring general soil characteristics and indicators, sampling and soil
preparation.
General soil characteristics reflect the physico-chemical composition of soils and give a first assessment of a
sample. Some are required to interpret specific soil characteristics and indicators. General soil characteristics
and indicators include texture, soil depth, soil density, pH (acidity), cation exchange capacity (CEC), cations
(Ca, K, Mg, Na), total carbon, nitrogen and phosphorus, the amount of coarse elements, calcium carbonate
(CaCO ,), and the presence of contaminants. The assessment of all or part of these characteristics is a pre-
requisite for assessing soil processes and is strongly recommended. should be carried out.
Moreover, assessing general soil characteristics or specific characteristics requires representative sampling
[ - ]
and soil preparation before analysis (see the ISO 18400 series 1 7 [1,2,3,4,5,6,7]). ).
The existing methods for measuring general soil characteristics are presented in Table 2Table 2 according to
their level of standardization.
Table 2 — Existing methods to measure general soil characteristics and indicators
General soil
characteristics and Level 1 Level 2
indicators
a) a) Soil texture
ISO 11277:2020, Soil quality — Determination of particle size Adaptation of ISO 13320: 2020, (, Particle size analysis — Laser
(particle size
[ ]
distribution in mineral soil material — Method by sieving and diffraction methods 9) for the measurement of soil texture (REFS)[9])
distribution) [ ]
sedimentation 8[8]
b) b) Bulk density
[ ]
ISO 11272:2017, Soil quality — Determination of dry bulk “Pedotransfer functions (Reference 96” (Hollis et al., 2012) )
[ ]
density 10[10]
NF X 31-501, Soil quality. - Physical methods. - Measuring of the bulk
[ ]
density of an undisturbed soil sample —- Cylinder method 11[11]
ISO 10390:2021, Soil, treated biowaste and sludge —
c) c) pH (acidity)
[
Determination of pH 12[12]
]
d) d) Cation
ISO 23470:2018, Soil quality — Determination of effective cation
Exchange
exchange capacity (CEC) and exchangeable cations using a
Capacityexchange
[ ]
hexamminecobalt(III)chloride solution 13[13]
capacity (CEC)
ISO 11260:2018, Soil quality — Determination of effective cation
exchange capacity and base saturation level using barium chloride
[ ]
solution 14[14]
e) e) Soil
ISO 10930:2012, Soil quality — Measurement of the stability of soil Spade-test: Visual Evaluationevaluation of soil structure
structure &and stability
[ ] [ ]
aggregates subjected to the action of water 15[15] (Reference 93Soil Structure (Guimaraes et al., 2011) )
[ ]
« Mini 3D soil profile » (Tomis et al. 2019) 105
[ ]
Slake test (Reference 92Fajardo et al., 2016) )
[ ]
Aggregate stability (Reference 95Herrick et al., 2001) )
[ ]
« Visual Soil Assessment (Reference 101 » (Sheperd 2009) )
[ ]
« Profil cultural (Reference 85 » (Boizard et al., 2017) )
f) f)
ISO 23470:2018, Soil quality — Determination of effective cation
Exchangeabl
exchange capacity (CEC) and exchangeable cations using a
+ + +
e cations (Ca , K , Mg , [ ]
hexamminecobalt(III)chloride solution 13[13]
+
Na )
General soil
characteristics and Level 1 Level 2
indicators
ISO 11260:2018, Soil quality — Determination of effective cation
exchange capacity and base saturation level using barium chloride
[ ]
solution 14[14]
g) g) Organic
ISO 10694:1995, Soil quality — Determination of organic and total Rock-Eval pyrolysis combined with PartySOC model
carbon (organic matter)
[ ]
carbon after dry combustion (elementary analysis) 16)[16] (Reference [89Cécillon et al., 2021)]) for assessing stable and active
fractions of total organic carbon in temperate ecosystems. (ISO
ISO 17184:2014, Soil quality - Determination of carbon and nitrogen by
document in preparation)
[ ]
near-infrared spectrometry (NIRS) 17)[17]
NF X 31-516, Soil Quality —- Granulo-densimetric fractionation of soil
[ ]
organic particulate material in water 18[18]
h) h) Carbonates
ISO 10693:1995, Soil quality — Determination of carbonate content —
[ ]
Volumetric method 19[19]
i) i) [ ]
ISO 54321:2020, Soil, treated biowaste, sludge and waste — Digestion of Pesticide Multi-residue method (Reference 100Rösch et al 2023) )
[ ]
Contamina
aqua regia soluble fractions of elements 20[20]
nts (depending on the
ISO 11504:2017, Soil quality — Assessment of impact from soil
[ ]
context)
contaminated with petroleum hydrocarbons 21[21]
ISO 21268-1:2019, Soil quality — Leaching procedures for subsequent
chemical and ecotoxicological testing of soil and soil-like materials —
[
Part 1: Batch test using a liquid to solid ratio of 2 l/kg dry matter 22
]
[22]
ISO 21268-2:2019, Soil quality — Leaching procedures for subsequent
chemical and ecotoxicological testing of soil and soil-like materials —
[
Part 2: Batch test using a liquid to solid ratio of 10 l/kg dry matter 23
]
[23]
ISO 21268-3:2019, Soil quality — Leaching procedures for subsequent
chemical and ecotoxicological testing of soil and soil-like materials —
[ ]
Part 3: Up-flow percolation test 24 [24]
ISO 21268-4:2019, Soil quality — Leaching procedures for subsequent
chemical and ecotoxicological testing of soil and soil-like materials —
[
Part 4: Influence of pH on leaching with initial acid/base addition 25
]
[25]
General soil
characteristics and Level 1 Level 2
indicators
ISO 17402:2008, Soil quality — Requirements and guidance for the
selection and application of methods for the assessment of bioavailability
[ ]
of contaminants in soil and soil materials 26 [26]
ISO 16198:2015, Soil quality — Plant-based test to assess the
[ ]
environmental bioavailability of trace elements to plants 27 [27]
j) j) Dry matter
ISO 11465:1993, Soil quality, Sludge and solid environmental
matrices — Determination of dry matter andresidue or water content
[
and calculation of the dry matter fraction on a mass basis 28 —
]
Gravimetric method [28]
Required for the physico-chemical analysis
→, it allows calculation of element concentration in the dry matter
k) k) Total N
ISO 13878:1998, Soil quality — Determination of total nitrogen content
[ ]
by dry combustion ("(“elemental analysis”) 29")[29]
i) l) Total P
ISO 11263:1994, Soil quality — Determination of phosphorus —
Spectrometric determination of phosphorus soluble in sodium hydrogen
[ ]
carbonate solution 30 [30]
4.3 Methods for measuring specific soil characteristics and indicators
Soil processes are linked to soil sub-functions and functions as described in ISO/TS 18718. To assess soil
processes, many methods exist to measure specific soil characteristics and indicators. As for general soil
characteristics, these are standardised at different levels.
Some of the methods are direct measurements of a function or sub-function whereas others are indirect. For
example, microbial biomass is an indirect indicator of organic matter mineralisation potential whereas soil
respiration is a direct measurement.
Tables 3The following tables 3, 4, 4 and 55 are organised as follows: in Table 3Table 3,, soil functions and sub-
functions are linked to soil characteristics and indicators reflecting soil processes. Tables 4Tables 4 and 55
further link the soil functions with the characteristics and indicators at level 1 and level 2, respectively, and
provide references.
Table 3 — Specific soil characteristics and indicators reflecting soil processes associated to soil functions and sub-functions
Specific soil characteristics and indicators Specific soil characteristics and indicators
Functions Sub-functions
1 a 2 b
associated to level 1 methods methods associated to level 2 methods methods
L1-C1. Total organic carbon content
SF1-Water retention
F1 - Water
L1-C2. Water retention
regulation,
L2-C1. Soil structure assessment via X-ray Computed
retention and
Tomographycomputed tomography
SF2-Infiltration and percolation L1-C3. Permeability
release
L2-C10. Permeability
L1-C4. Microbial soil biomass L2-C2. Organic matter mineralisation in soil
SF3-Decomposition
L1-C5. Feeding activity L2-C3. Litter bag
F2 - Organic matter
SF4-Resource reallocation L1-C1. Total organic carbon content
storage,
transformation
L2-C4. Carbon quality – active and stable organic carbon
and recycling
L1-C1. Total organic carbon content
SF5-Biochemical transformation L2-C5. Functional diversity: Genes coding analysis
L1-C6. Microbial respiration (carbon mineralization)
L2-C6. Microbial catabolic activities
L1-C4. Microbial soil biomass
L1-C7. Enzymatic activities
SF6-Nutrient transformation L2-C7. Microbial catabolic activities
L1-C8. Total nitrogen content
L1-C9. Assimilable phosphorus content
F3 - Nutrient cycling
L1-C10. CEC and exchangeable cations
SF7-Nutrient reallocation L2-C11. CEC and exchangeable cations
L1-C7. Enzymatic activities
L2-C8. Microbial activities (denitrification)
SF8-Nutrient assimilation L1-C11. Available NO2 and NO3
L2-C5. Functional diversity: Genes coding analysis
L1-C12. Bioavailability of metal contaminants.
SF9-Retention
F4 - Contaminants
L1-C13. Total and extractable metal trace element
retention,
SF10-Transformation L2-C6. Microbial catabolic activities
Level 1 methods are provided in Table 4.
Level 2 methods are provided in Table 5.
Specific soil characteristics and indicators Specific soil characteristics and indicators
Functions Sub-functions
1 a 2 b
associated to level 1 methods methods associated to level 2 methods methods
transformation
L1-C7. Enzymatic activities
a
and degradation
SF11-Degradation L1-C14. Soil microbial diversity L2-C6. Microbial catabolic activities
L1-C15. Degradation of organic chemicals
SF12-Emission L2-C6. Microbial catabolic activities
F5 - Gas exchanges
with the atmosphere
SF13-Captation L2-C4. Carbon quality – active and stable organic carbon
L1-C1. Total organic carbon content
L2-C4. Carbon quality – active and stable organic carbon
L1-C4. Microbial soil biomass
L2-C1. Soil structure assessment via X-ray Computed
L1-C16. Ecotoxicological quality
F6 - Habitat
Tomographycomputed tomography
L1-C17. Effect of chemicals macrofauna
provision
L1-C14. Abundance and diversity of microbial L2-C8. Taxonomic diversity (bacteria &and fungi)
L1-C18. Abundance and diversity of soil invertebrates L2-C9. Fungal, bacterial ratio
L2-C1. Soil structure assessment via X-ray Computed
SF16-Inherent soil stability
Tomographycomputed tomography
F7 - Physical Stability
Salinisation requires:
L2-C1. Soil structure assessment via X-ray Computed
stability
Tomographycomputed tomography
SF17-Stability evolution L1-C16. Electrical conductivity
L2-C11. CEC and exchangeable cations
L1-C10. CEC and exchangeable cations
a
Level 1 methods are provided in Table 4.
b
Level 2 methods are provided in Table 5.
Table 4 — References and description of level 1 specific soil characteristics and indicators
Specific soil Related
characteristics function Description and references
and indicators s
[ ]
ISO 23400:2021, Guidelines for the determination of organic carbon and nitrogen stocks and their variations in mineral soils at field scale 31 [31]
L1-C1. Total F1-SF1;
[ ]
organic carbon F2-SF5; ISO 10694:1995, Soil quality — Determination of organic and total carbon after dry combustion (elementary analysis) 16)[16]
content F5-SF11
[ ]
ISO 17184:2014, Soil quality - — Determination of carbon and nitrogen by near-infrared spectrometry (NIRS) 17) [17]
L1-C2. Water
[ ]
F1-SF1 ISO 11274:2019, Soil quality — Determination of the water-retention characteristic — Laboratory methods 32 [32]
retention
[ ]
L1-C3. Permeability F1-SF2 ISO 17892-11:2019, Geotechnical investigation and testing — Laboratory testing of soil — Part 11: Permeability tests 33 [33]
[ ]
ISO 14240-1:1997, Soil quality — Determination of soil microbial biomass — Part 1: Substrate-induced respiration method 34 [34]
[ ]
ISO 14240-2:1997, Soil quality — Determination of soil microbial biomass — Part 2: Fumigation-extraction method 35 [35]
[ ]
ISO 16072:2002, Soil quality — Laboratory methods for determination of microbial soil respiration 36 [36]
[ ]
ISO 17155:2012, Soil quality — Determination of abundance and activity of soil microflora using respiration curves 37 [37]
[ ]
F2-SF3;
ISO 11063:2020, Soil quality — Direct extraction of soil DNA 38 [38]
L1-C4. Microbial soil
F3-SF6;
ISO 17601:2016, Soil quality — Estimation of abundance of selected microbial gene sequences by quantitative PCRpolymerase chain reaction
biomass
F6-SF14
[ ]
(qPCR) from DNA directly extracted from soil 39 [39]
ISO/TS 29843-1:2010, Soil quality — Determination of soil microbial diversity - Part 1: Method by phospholipid fatty acid analysis (PLFA) and
[ ]
phospholipid ether lipids (PLEL) analysis 40 [40]
ISO/TS 29843-2:2021, Soil quality — Determination of soil microbial diversity — Part 2: Method by phospholipid fatty acid analysis (PLFA) using
[ ]
the simple PLFA extraction method 41 [41]
L1 – C5. Feeding ISO 18311:2016, Soil quality — Method for testing effects of soil contaminants on the feeding activity of soil dwelling organisms — Bait-lamina
F2-SF3
[ ]
activity test 42 [42]
L1-C6. Microbial
[ ]
ISO 16072:2002;, Soil quality — Laboratory methods for determination of microbial soil respiration 36 [36]
respiration (carbon F2-SF5
[ ]
ISO 23265:2022, Soil quality - — Test for estimating organic matter decomposition in contaminated soil 43 [43]
mineralization)
[
L1-C7. Enzymatic F3-SF6; ISO 20130:2018, Soil quality — Measurement of enzyme activity patterns in soil samples using colorimetric substrates in micro-well plates 44
]
activities F3-SF7 [44]
...
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