ICP Forests Manual 2020 Basic Design
Source: environment.data.gov.uk (2026-01-05)

NFI+ Soil Condition & Health. This dataset contains comprehensive soil chemical and physical indicators collected as part of the NFI+ (National Forest Inventory Plus) programme and the BioSoil forest soil and biodiversity monitoring network. The dataset covers forest soil sampling sites across Great Britain and provides baseline and monitoring data on soil condition and health in forest ecosystems.

Chemical indicators measured include: soil pH (measured in water and CaCl2), organic carbon content (%), total nitrogen (%), available phosphorus (mg/kg), exchangeable cations (Ca, Mg, K, Na in cmol/kg), cation exchange capacity (cmol/kg), base saturation (%), and heavy metal concentrations where applicable.

Physical indicators measured include: soil texture (% sand, silt, clay), bulk density (g/cm³), porosity (%), aggregate stability, moisture content at sampling, and soil depth profiles.

Samples were collected at multiple depth intervals (0-10cm, 10-20cm, 20-40cm) using standardised protocols aligned with ICP Forests and BioSoil methodologies.  Each sampling location includes associated metadata on forest type, soil type, elevation and forest origin (plantation or natural).  The data include chemical and physical soil properties.

Quality assurance procedures included duplicate sampling, laboratory reference standards, and inter-laboratory comparisons.

Limitations:  Data coverage is limited to forest soils only. Some historical samples may have incomplete heavy metal analysis. Seasonal variation should be considered when interpreting results.

Data are georeferenced using a delocalised grid. The bounding coordinates for each grid square are included in the dataset. Further information about the delocalisation process is provided in the dataset evidence pack.

The 'NFI+ Soil Condition & Health' is a project funded by the UK Government through Defra’s Natural Capital and Ecosystem Assessment programme (NCEA), England sites, and the Department for Energy, Security and Net Zero (DESNZ), Scotland sites.  Users should ensure they have read the supporting documentation before viewing or making use of the data. This includes the NCEA Analysis Ready Data Limitations Statement and dataset specific limitations/caveats outlined in the supporting documentation, please refer to the 'Metadata' tab on the 'Soil Condition Data 2022-24' dataset  Attribution statement: © Forestry Commission copyright and/or database right 2025. Includes data from Ordnance Survey, British Geological Survey, and the Met Office. All rights reserved.

United Nations Economic Commission for Europe (UNECE)
Convention on Long-range Transboundary Air Pollution (CLRTAP)
International Co-operative Programme on Assessment and
Monitoring of Air Pollution Effects on Forests (ICP Forests)
MANUAL
on
methods and criteria for harmonized sampling, assessment,
monitoring and analysis of the effects of air pollution on forests
Part II
Basic Design Principles for the
ICP Forests Monitoring Networks
Version 2020-2
(Last update 11/2021)

Prepared by:
Marco Ferretti, Richard Fischer, Volker Mues, Oliver Granke, Martin Lorenz, Walter Seidling,
Manuel Nicolas
Ferretti M, Fischer R, Mues V, Granke O, Lorenz M, Seidling W, Nicolas M, 2020: Part II:
Basic design principles for the ICP Forests Monitoring Networks. Version 2020-2. In: UNECE
ICP Forests Programme Co-ordinating Centre (ed.): Manual on methods and criteria for
harmonized sampling, assessment, monitoring and analysis of the effects of air pollution on
forests. Thünen Institute of Forest Ecosystems, Eberswalde, Germany, 33 p + Annex.
[http://icp-forests.net/page/icp-forests-manual]
ISBN: 978-3-86576-162-0

Acknowledgements: The authors are grateful to Sue Benham, Roberto Canullo, Sébastien
Cecchini, Luc Croisé, Bruno De Vos, Hans-Peter Dietrich, Stefan Fleck, Elena Gottardini,
Karin Hansen, Morten Ingerslev, Till Kirchner, Sébastien Macé, Alexa Michel, Nenad Potočić,
Stephan Raspe, Tanja Sanders, Kai Schwärzel, Sigrid Strich, András Szepesi, Anne
Thimonier, Iben Thomsen, Volkmar Timmermann, Arne Verstraeten, and Lars Vesterdal, for
providing written comments.
The compilation of the first edition of this Manual part was co-financed by the European
Commission under the LIFE Regulation and supported by Corpo Forestale dello Stato
(Rome/Italy).
All rights reserved. Reproduction and dissemination of material in this Manual for educational
or other non-commercial purposes are authorized without any prior written permission from
the ICP Forests Programme Co-ordinating Centre provided the source is fully acknowledged.
Reproduction of material in this Manual for resale or other commercial purposes is prohibited
without written permission of the ICP Forests Programme Co-ordinating Centre of ICP
Forests.
Application for such permission should be addressed to:
Programme Co-ordinating Centre of ICP Forests
Thünen Institute of Forest Ecosystems
Alfred-Möller-Str. 1, Haus 41/42
16225 Eberswalde
Germany
Email: xxx@xxx.xx
Eberswalde, 2020

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CONTENTS

1
INTRODUCTION .............................................................................................................................5
2
SCOPE AND APPLICATION ..........................................................................................................5
3
OBJECTIVES ..................................................................................................................................5
4
MONITORING DESIGN ...................................................................................................................6
4.1
DEFINITIONS ............................................................................................................................................ 6
4.1.1
Definition of monitoring intensity levels ............................................................................................. 6
4.1.2
Definition of monitoring plots and sites ............................................................................................. 7
4.1.3
Definition of mandatory and optional variables ................................................................................. 8
4.1.4
Definition of types of measurement .................................................................................................. 8
4.2
MONITORING SITES AND PLOT DESIGN ............................................................................................... 8
4.2.1
Large-scale (Level I) monitoring plots ............................................................................................... 8
4.2.2
Intensive (Level II) monitoring sites ................................................................................................ 10
5
GENERAL INFORMATION ON MONITORING PLOTS AND STANDS ..................................... 13
5.1
MEASUREMENTS AND REPORTING UNITS ........................................................................................ 13
5.1.1
Plot description (stored in ‘System Instalment’) .............................................................................. 13
5.1.2
Stand description ............................................................................................................................ 15
5.1.3
Management operations and natural disturbances ......................................................................... 23
5.1.4
Surveys and measurements at plot and site level ........................................................................... 31
5.2
QUALITY ASSURANCE AND DATA QUALITY REQUIREMENTS ......................................................... 33
6
DATA SUBMISSION .................................................................................................................... 33
6.1
DATA TRANSMISSION TO PROGRAMME CO-ORDINATING CENTRE ............................................... 33
6.2
DATA VALIDATION ................................................................................................................................. 33
7
REFERENCES ............................................................................................................................. 34
ANNEX I – RECOMMENDATIONS FOR FUNCTIONAL INTEGRATION OF LEVEL I AND
NATIONAL FOREST INVENTORIES FOR TREE CONDITION ASSESSMENTS .............................. 35
ANNEX II – RECOMMENDATIONS FOR CONVERTING CROSS-CLUSTER PLOTS INTO FIXED
AREA LEVEL I PLOTS ......................................................................................................................... 36
ANNEX III – MINOR CHANGES AFTER 2020 ..................................................................................... 37
ANNEX IV – SHOULD LEVEL II PLOTS ENTERING THE STAND REGENERATION STAGE BE
MAINTAINED UNDER MONITORING OR RELOCATED? ................................................................. 38

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1 Introduction
Most of the success of a monitoring programme rests on its design. Design can follow a top-
down approach when administrative structure, aims and objectives of the monitoring are
simple and can be easily identified (Parr et al. 2002). On the other hand, design may be quite
complex when the programme has to face multiple objectives and purposes, carried out by
an international and multi-agency co-operation (when different conceptual and operational
perspectives have to be considered), and have to integrate existing monitoring “traditions”
(which are always reluctant to change) (Parr et al. 2002). Under such circumstances, a top
down approach is hardly feasible, and the bottom-up approach remains the only option (Köhl
et al. 2000, Parr et al. 2002).
This is particularly true for the two ICP Forests monitoring networks: although developed
following generally agreed principles, given the nature of the programme the national
networks originate from national initiatives and - as such - reflect more or less country-based
design concepts. For example, the large-scale (Level I) network is in many cases a
subsample of National Forest Inventories. As such, for example, the definition of the target
statistical population and the plot design may be different from country to country (Cozzi et
al. 2002). The same applies to the intensive monitoring (Level II) network, with a number of
different plot designs being used in ICP Forests. After 35 years of monitoring this situation
cannot be denied, ignored or changed. Rather it can and must be acknowledged and
managed as responsibly as possible.
Part II of the ICP Forests Manual provides guidelines about (i) how to achieve basic design
requirements and at the same time (ii) allow the continuation and consistency of the existing
data series.
2 Scope and application
Part II of the ICP Forests Manual focuses on the description of the overall monitoring
structure, the selection and design of sample plots (Level I and Level II), data collection (plot
and stand description and geo-referencing, the variables to be measured) and data
submission.
The guidelines provided here permit a minimum level of harmonization which is essential to
ensure data comparability across participating institutes and proper data processing. To have
their data added to the international ICP Forests database and used in evaluations, National
Focal Centers and their scientific partners participating in the UNECE ICP Forests
programme should follow the methods described in this Manual.
3 Objectives
Monitoring design has the objective to ensure consistency between the aims of the
programme and the activities carried out to achieve them. In this context, it is worth recalling
the two main features of ICP Forests described in the Strategy Paper 2016–2023 (c.f. Annex
1 in Part I of this Manual: http://www.icp-forests.net/page/icp-forests-manual):
•
The systematic large-scale monitoring (Level I) provides periodic overviews of the
spatial and temporal variation in forest health, vitality, and forest soil condition.

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•
The intensive monitoring (Level II) is carried out on permanent, highly equipped forest
monitoring plots to foster integrative studies on cause-effect relationships based on
consistent and harmonized long-term data series.

Given these objectives, relevant design issues are:
1 the type, number and characteristics of large-scale and intensive monitoring plots that
will permit quantitative estimates with known uncertainty of forest condition at a given
time and changes over time (Aim 1); and the identification of relationships between a
given set of predictors and response variables (Aim 2). These issues will be covered in
Chapter 4.
2 The set of investigations necessary to obtain data on forest condition (Aim 1) and on
the stress factors of concern (Aim 2). This will be covered in Chapter 5.1
3 The set of variables to be measured within each survey is under the responsibility of
individual Expert Panels and will be covered within individual parts of the Manual.
4 The Quality Assurance procedures, summarized in Chapter 5.2, were developed
following the approach described in Part III and will be described for each survey in
Parts IV–Part XVII of the Manual.
5 The rules for data submission are summarised in Chapter 6.
4 Monitoring design
4.1 Definitions
4.1.1 Definition of monitoring intensity levels
The two objectives of ICP Forests provide already some guidance for design and ask for two
different levels of monitoring intensity: the systematic, large-scale (Level I) and the intensive
(Level II) monitoring. The two intensity levels of the monitoring are defined by the number,
depth, and temporal resolution of investigations carried out on the plot and by the number of
plots covered by the investigations. The two monitoring levels differ for the following three
elements:
•
Network design: Level I requires data to be formally representative at a large-scale,
intentionally covering the UNECE region (56 countries, most of which are located in
Europe or in the EECCA1 region). As such, a probabilistic sampling is required in
order to allow design-based inference. On the contrary, no formal representativeness
is required for Level II, and monitoring plots can be allocated according to different
criteria (purposive sampling).
•
Variables to be assessed: Level I plots are mostly concerned with forest condition,
and attributes to be measured are typically those able to describe tree condition.
Level I is also the basis for large-scale assessments of forest soils, foliar nutrient
content, and biodiversity. In short, Level I envisages a limited number of assessments
on a large number of plots. Level II aims at understanding cause-effect relationships
between the condition of forest ecosystems on one side and anthropogenic as well as
natural drivers and stress factors on the other. As such, it requires assessments to

1 Eastern Europe, Caucasus and Central Asia (Armenia, Azerbaijan, Belarus, Georgia, Kazakhstan,
Kyrgyzstan, Moldova, Russian Federation, Tajikistan, Turkmenistan, Ukraine and Uzbekistan)

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cover a range of responses (from tree condition to growth and biodiversity), predictors
(e.g. deposition, gaseous air pollutants, meteorology) and intermediate variables
(having the role of response and predictors, according to the analysis, e.g. soil, soil
solution and foliar nutrition) (Vos et al. 2000). In short, Level II envisages – according
to the general trade-off between number of objects (plots) and number of parameters
– a large number of assessments on a limited number of plots.
•
Plot design: given the differences in the assessments to be carried out and the
distinct aims, Level I and II vary also in plot design, both in shape and size. Unlike
Level I, Level II must accommodate a number of different investigations while at the
same time prevent conflicts between them. Level II can be considered as a long-term
monitoring and research infrastructure hosting permanent equipment. A shared
requisite for Level I and II is the area frame: both Level I and II plots should have a
known area.
4.1.2 Definition of monitoring plots and sites
4.1.2.1 Level I plots
A Level I plot is an area of defined dimension and shape. Most commonly plots are circular
plots defined by the coordinates of the centre and by a radius. However, the design of the
plot is under the responsibility of the individual countries but should at least be consistent
within each country.
Level I plots are allocated over the statistical population of concern according to defined
sampling design which may be different from country to country (see below), provided it is on
a probabilistic basis. In the past, in some cases there was no fixed/defined plot: a fixed
number of trees for crown condition were selected around co-ordinates of grid intersections
and following a standardized scheme. This kind of design is not – by definition – a plot in
formal terms, and has limitations with respect to area related statistical estimates. For
countries wanting to keep such a design, it is worth noting that data can be processed only to
derive sample statistics but are not suited for estimation purposes and will not be considered
in that respect. However, for the sake of time series it is possible to maintain the existing
sample trees. Guidelines how to achieve a proper plot design while maintaining the former
sample trees (and the existing time series) are provided in Annex II.
4.1.2.2 Level II sites
A Level II site is a designated forest area of homogeneous ecological condition within which
a Level II plot is installed. The area is not necessarily of defined shape and size, but must be
large enough to accommodate the set-up of a Level II plot of a minimum size of 0.25 ha and
a surrounding buffer zone (see below). The plot plus the buffer zone constitute the Level II
site.
4.1.2.3 Level II plot
A Level II plot is an area of defined shape and size (mostly 0.25 ha) located within a Level II
site. Desirably, all the in-site measurements are carried out within the plot’s boundaries and
according to appropriate statistical requirements. When it is not possible (e.g., limited area,
destructive sampling), some measurements can be located outside the plot, but within the
Level II site boundaries. Data collected within the plot and with a proper statistical design can
be considered formally representative for the plot. Data originated from measurements
located outside the plot, or within the plot but with an incorrect design, cannot be considered
formally representative for the plot. They can however be assumed to be indicative for the
site, although with unknown confidence.

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4.1.2.4 Level II sub-plots
For specific purposes (e.g. tree condition in dense stands, deposition sampling, ground
vegetation assessment), one or more sub-plots may be necessary. A sub-plot is an area of
defined dimension and shape within which the measurements are carried out. To be
representative for the plot, the sub-plots must be selected according to a statistically sound
procedure.
4.1.2.5 Level II buffer zone
The buffer zone is an area surrounding the Level II plots designated to ensure plot protection
against direct influence of nearby paths, roads and disturbances. The size and shape of the
buffer zone depends on local conditions. However, it must be large enough to protect the plot
from direct disturbances and – at the same time – still be characterized by the same
homogeneous ecological conditions in terms of aspects, slope, canopy cover and soil
condition. The buffer zone must be used for in-site measurements that cannot be carried out
within the plot’s boundaries. By definition, these measurements are not formally
representative for the Level II plot. However, they can be considered indicative for the site.
4.1.3 Definition of mandatory and optional variables
Two main sets of variables are defined, called “mandatory” and “optional” variables. The
status means that within the respective surveys the mandatory variables must be measured.
On the other hand, “optional” identifies those variables that may or may not be measured.
This status must not be confused with the obligation of EU-member states to assess and
submit data under relevant EU regulations.
4.1.4 Definition of types of measurement
Two series of measurements are defined: in-site and off-site measurements.
In-site measurements are all those assessments that are carried out within the Level II sites.
They include tree condition, tree growth, tree phenology, biodiversity, ozone injury on a plot’s
main tree species, soil sampling, soil solution, foliar sampling, throughfall and stemflow
deposition sampling, litterfall sampling, leaf area index, soil moisture and temperature, and
below-canopy meteorological conditions.
Off-site measurements are those that – by definition – are carried out outside the forest
stand, in an open area close to the plot. They include open field bulk deposition, open field
meteorology, gaseous air pollutants, and ozone injury at the forest edge (light exposed
sampling site (LESS)).
4.2 Monitoring sites and plot design
4.2.1 Large-scale (Level I) monitoring plots
The selection and characteristics of Level I plots are always within the responsibility of the
countries. However, to facilitate data evaluation, the following guidelines must be considered.
4.2.1.1 Plot density
The minimum number of plots per country should be equal to the forest area of the country
(in km2) divided by 256. This is to keep consistency with the traditional plot density adopted
within the ICP Forests. For small countries and/or infrequent forest types, denser sampling
should be considered (e.g. Köhl et al. 1994). Data from possibly denser national grids are not
submitted to the central database.

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4.2.1.2 Plot selection
A probabilistic sampling design is essential to ensure that large-scale monitoring plots fit the
aims of the Level I monitoring. Plots should be allocated over the target statistical population
in a way that – for each element of the population – a non-zero probability of being selected
is ensured. When setting-up a new Level I network, different designs can be adopted (e.g.,
random sampling, systematic sampling, tessellation stratified sampling) which fit the above
requirement. The definition of the sampling scheme is under the responsibility of the
individual countries.
4.2.1.3 Plot selection to achieve harmonization/integration with existing networks
Different forest monitoring networks may already exist within a country. Due to their nearly
ubiquitous presence in European countries, the most common networks are National Forest
Inventories (NFI) and Level I. Two cases may exist (Ferretti, 2010):
(1) Level I and NFI are already merged in the same network. This may be the case because
Level I was established on existing NFI networks (most frequent) or the other way round. In
general, a subsample of NFI plots was used for Level I (Köhl et al. 1994; Neumann 1993). In
these cases, networks are already integrated and harmonized or at least co-located. Some
further harmonization may be necessary due to a possible adaptation of survey methods in
agreement to international procedures, but this can be traced and documented.
(2) Countries with separate NFI and Level I networks. This may have happened because (i)
there was no NFI in the past, and Level I was created prior to the NFI; (ii) NFI and Level I
were developed independently; (iii) countries with a former joint NFI-Level I network (Case 1)
abandoned (for a variety of reasons) their original NFI for a newly designed one, thus having
now two separate networks. The result is that Level I and NFI are carried out on different
networks.
In Case 2, it may be useful to apply some harmonization/integration concept that may allow
maximum use of existing networks and information. A functional integration of networks (in
the sense of Ferretti 2010) is suggested in Annex I.
4.2.1.4 Plot design and selection of sample trees and sample locations for other
surveys
Plot design is under the responsibility of the countries, and must be reported when submitting
data. Figure 1 shows different plot designs adopted for Level I in ICP Forests. While different
designs are possible, it is important that plots are designed on a fixed area basis, a condition
necessary for estimation purposes and to allow a better integration with NFIs. Deviations
from the fixed area concept are only possible in exceptional cases for tree condition
assessments in order to ensure time series. When such deviations are adopted (e.g. fixed
number of trees without area related information), data can be used for descriptive statistics,
but not in design-based inference. Although desirable, it is not necessary that plots are of the
same size and shape between different countries; rather it is essential that they are of the
same design within a country, respectively the federal states within Germany or Belgium.
When NFI and Level I networks are separated, it is recommended that the Level I plots will in
addition adopt the country-specific NFI design (see Chapter 4.2.1.3). As an alternative, and
since it was already used for assessing tree diameter at breast height (dbh), dead wood, and
ground vegetation, the BioSoil design is also recommended.
Annex II provides recommendations on how to move from a fixed-number of trees sample
point to a fixed area plot, without losing the connection with existing data series.
On Level I, annual tree crown condition assessment is mandatory. On a voluntary basis tree
growth, ground vegetation and foliar chemistry are assessed according to the respective
methods (see Manual Parts V, VII and XII). To date a European-wide soil condition survey
has been carried out twice on Level I plots. The concept foresees a repetition of the soil
survey in larger time intervals (e.g. every ten to twenty years). Soil surveys should be carried

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out temporally synchronized in all participating countries. Methods for soil condition surveys
are described in Part X.

Figure 1: Examples of designs adopted for Level I plots. A. Cross-cluster sample; B. Circular
plot: 1, subplot for all trees above given dbh thresholds; 2, subplot for large trees only; C. BioSoil plot:
1.30 m2 subplot; 400 m2 subplot; 2000 m2 subplot. (drawing by M. Ferretti)
4.2.2 Intensive (Level II) monitoring sites
The selection and characteristics of Level II sites are always within the responsibility of the
countries. However, to facilitate data evaluation, the following guidelines must be considered
4.2.2.1 Number of sites
The number of Level II sites should equal at least approximately 10% of the Level I plots.
4.2.2.2 Selection of sites
Sites are selected on a preferential basis taking into account:
•
Ecological and logistic issues: The situation shall be as homogeneous as possible
(regarding e.g. tree species composition, stand type and ecological conditions within
the site). However, the more homogeneous the site, the higher is the chance its
homogeneity will decrease with time as result of different factors (Palmer 1993). Sites
should be accessible to allow routine operations;
•
The importance of forest ecosystems within a country: One important selection
criterion is that the Level II sites in a country should be located in such a way that the
most important forest species and most widespread growing conditions in the country
are represented. In order to facilitate data analyses; it is advisable to give priority to
replicates within the same forest ecosystem type, rather than spreading plots over a
huge variety of forest types;
•
The existence of data series and the importance of their continuation: Whenever
possible, sites should be selected which have been monitored during the last years.
The great advantage of existing data on air quality and meteorological parameters
from nearby stations should be taken into consideration whenever establishing
Level II sites.
4.2.2.3 Site and plot design
There are different designs adopted for Level II sites and plots (Figure 2). Countries are
responsible for selecting the most appropriate design, provided they can conduct the
investigations as described in the Manual, Parts III-XVII. While different designs are allowed,
some requirements must be attained:
•
Plot boundaries must be permanently identified and geo-referenced.
N
25 m
E
S
A. Cross-cluster sample,
undefined shape and area
C. BioSoil plot,
defined shape and area
B. Circular plot,
defined shape and area
1
2
3
1
2

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•
Plots must have a minimum size of 0.25 ha. The area of the plot must be always
reported.
•
Sub-plots are allowed, and the sub-plot selection criteria must be described. Sub-plot
boundaries must be permanently identified and geo-referenced. The area of the sub-
plots must always be reported.
The selection of sample trees and/or the positioning of measuring devices is described in the
respective part of the Manual dealing with the concerned survey.
Examples of the location of a Level II site and plot with in-site and off-site measurements is
given in Figure 2.
There should be no differences in the management of the plot, its buffer zone and the
surrounding forest during the whole monitoring period (e.g. management operations should
be comparable and disturbances by the monitoring should be kept to a minimum).

Figure 2: Example of the location of a Level II monitoring site and its organization, with buffer
zone, plot and sub-plots. In-site measurements are those that must be carried out within the site; off-
site measurements are those to be carried out in an open area close to the plot. Note that different
shapes (e.g. rectangles, polygons) and sizes (min 0.25 ha) are possible, as well as different types of
internal organization of the plot. Size and shape must, however, be known and reported (drawing by
M. Ferretti)
4.2.2.4 Types of Level II sites and plots
Two types of Level II sites/plots are identified:
(1) Level II standard: on these sites the following surveys are mandatory
•
Crown condition (annually)
•
Tree growth (every 5 years)
•
Foliar chemistry (every 2 years)
Open areas
Monitoring site
in-site measurements:
Tree condition
Tree growth
Tree phenology
Ozone injury on MTS
Soil
Soilsolution
Foliarchemistry
Litterfall
Throughfall/stemflow
Access road
Forest
off-site measurements:
Meteorology
Bulk deposition
Gaseous pollutants
Ozone injury at forest edge
Access road
Buffer zone
Plot
Sub-plots (when
necessary)
Path to access the site
in-site measurements:
Tree condition
Tree growth
Tree phenology
Ozone injury on main tree
species
Soil
Soil solution
Foliar chemistry
Litterfall
Throughfall/stemflow deposition
Ground vegetation
LAI
Soil moisture & temperature
Below-canopy meteorology

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•
Ground vegetation (every 5 years)
•
Deposition (continuously)
•
Soil solid phase (every 10-20 years)
•
Meteorology (at least on 10% of the plots) (continuously)
It is acknowledged that deposition is currently not monitored on all Level II plots because it
was initially not mandatory. Participating countries are, however, highly encouraged to
extend the deposition survey to all Level II plots.
(2) Level II core: these sites are a sub-sample of the previous standard Level II sites. On
core sites, the same surveys as on the standard Level II sites are carried out. In addition, the
following surveys are conducted:
•
Litterfall (continuously)
•
Leaf area index (annually)
•
Tree phenology (several times within a year)
•
Tree growth (intensive) (every year by growth bands)
•
Soil solution (continuously)
•
Soil water (continuously)
•
Air quality (passive and/or active sampling, continuously)
•
Visible ozone injury (at least once per year, where relevant)
•
Meteorology (continuously)
Core plot surveys are carried out on a voluntary basis. In case that countries are willing and
interested to carry out intensified monitoring beyond standard Level II surveys, it is strongly
recommended to carry out the complete set of core plot surveys in order to facilitate
transnational and integrated statistical data evaluations and process-based modelling.
Preference shall be given to a smaller number of intensive monitoring plots with complete
sets of core plot surveys instead of operating bigger numbers of plots that carry different
combinations of surveys beyond the Level II standard surveys. (In response to specific
national interests and needs and/or thematic focuses - different combinations of surveys can
be applicable.)
4.2.2.5 Options for Level II monitoring sites after a severe disturbance or during the
stand regeneration stage
Unplanned severe disturbances (e.g. by storm, fire or insect attack) can cause large gaps in
the canopy, so that a Level II site (i.e. plot plus buffer zone) does no longer satisfy the
requirement for homogeneity in ecological conditions. As a result the collected data can
hardly be assumed to still represent the whole site area.
In addition, at some point in time, forest stands under even-aged silvicultural systems are to
be regenerated into young stands, which can lead to practical difficulties for the continuity of
some monitoring activities and may fail to result into a new stand of interest (e.g. if the main
targeted tree species doesn’t succeed to regenerate).
Different options are possible to handle such situations:
-
to relocate the plot to an adult stand with homogenous canopy cover,
-
to keep measuring the plot at the same location, providing that methods can be
adapted to overcome the practical difficulties induced by such contexts,
-
to do both (which is recommended, as it combines advantages from the former two
options but it does require additional resources).

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Since this choice relies on local capacities, it is preferably given to the NFCs. It must be
noted, however, that either choice can have strong strategical implications for the whole
international Level II network. E.g. whereas the Level II plots have generally been installed in
adult forest stands, an increasing share of plots in juvenile stands can help considering the
stand development stage as an additional explanatory factor for ecosystem responses, while
possibly lowering the capacity of the network to detect and evaluate impacts due to
environmental changes. As a consequence, plots that have achieved very heterogeneous
canopy cover after severe disturbances or/and that have turned to the regeneration stage
must be systematically reported as well as the choice made to handle them. In addition, for
all stands under even-aged silvicultural systems the approximate year when they are
supposed to enter the regeneration stage must be estimated and reported, so that the
occurrence of such situations can be foreseen in the coming decades and taken into account
in the ICP Forests strategy.
To help NFCs in their choice, pros and cons of either option are synthesized in Annex IV.
In case the choice is made to relocate a plot, care should be taken to keep trace of the exact
position of the abandoned plot area and of the monitoring devices in order to be able to
reuse the same location later. The replacement plot can be located either close to the
replaced one or in a different context, but in any case it must be identified with a different plot
code.
5 General information on monitoring plots and stands
5.1 Measurements and reporting units
5.1.1 Plot description (stored in ‘System Instalment’)
Plot descriptive information has to be submitted once at plot installation or whenever
changes have occurred (e.g. due to storm damage, species change) (Table 1).

Table 1: Quick reference of variables to be reported for the general plot description (o – optional, m
– mandatory)
Variable
Reporting
unit/type/format
Target plot type
Level I
Level II
standard
Level II core
Country code
Code
m
m
m
Plot number
Number
m
m
m
Plot size
Hectare
m
m
m
Plot design
Code
m
m
m
Installation date
Date
m
m
m
Plot status
Active/not active
o
m
m
Latitude
WGS84
m
m
m
Longitude
WGS84
m
m
m
Altitude class
Code
m
m
m
Altitude
Meters
o
o
o
Orientation
Code
m
m
m
Slope
Degrees
o
m
m
Relocated plot
Number
m
m
m

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5.1.1.1 Plot number
The plot number is an identifier and must be unique within each participating country or
region (e.g. federal state). For each new plot a new plot number has to be used and
submitted. In case that an existing plot is replaced by a newly installed plot, a new plot
number (never been used before) has to be chosen for the new plot.
5.1.1.2 Plot design
The plot design of Level I and Level II plots is described by codes:
Code
Description
110
Level I cross-cluster plot
120
Level I circular fixed area (one radius defined)
121
Level I circular fixed area (more than one radius for one centre point defined)
122
Level I more than one circle (distinct centres)
123
Relascope used to determine trees
130
Level I combination of 110 and 120
131
Level I combination of 110 and 121
140
Level I quadratic plot
141
Level I rectangular plot
150
Level I polygonal plot
199
Other Level I plot design
210
Level II quadratic plot
211
Level II rectangular plot
220
Level II polygonal plot
230
Level II circular fixed area (one radius defined)
231
Level II circular fixed area (more than one radius for one centre point defined)
232
Level II more than one circle (distinct centres)
299
Other Level II plot design
For Level II plots, a map or a scheme should be added as a data accompanying report to
better describe the plot design within the site, including: scale, location and size of the
subplots, perimeter of fence(s), location of the sample trees and samplers, ungulate species
actually excluded or not excluded from fenced areas. The design of the open field plot can be
described in a separate map or scheme within the same document accompanying report.
5.1.1.3 Plot coordinates:
A plot centre, so called “reference point” has to be marked permanently. Its geographic
coordinates are specified in geographic degrees, minutes and seconds. Format description is
made available in the online documentation on the ICP Forests website.

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Figure 3: Exemplary definition of a plot area providing the exact coordinates for the SW-corner
of the plot as well as the azimuth from North and the distance to the other corner points
5.1.1.4 Relocated plot
In case a new plot is installed in order to replace another one, the number of the replaced
plot is to be reported.
5.1.1.5 Additional information
For definitions of additional attributes, see the online documentation.
5.1.2 Stand description
Information on the stand must be reported every five years. Reporting should occur every full
and half decade (year 2010, 2015, 2020, …). Table 2 presents an overview of variables to be
reported. Each variable is explained in the following text.

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Table 2: Quick reference of variables to be reported for the general stand description
(o – optional, m – mandatory)
Variable
Reporting
unit/type/format Target plot type

Level I
Level II
Level II
core
Country code
code
m
m
m
Plot number
number
m
m
m
Stand history
code
o
m
m
Previous land use
code
o
m
m
Origin of current stand
code
o
m
m
Main tree species
code
m
m
m
Type of tree species mixture
code
o
m
m
Top height
meter
o
m
m
Determination of top height
code
o
m
m
Forest type
code
m
m
m
Age class
code
m
m
m
Number of tree layers
code
o
m
m
Coverage of tree layers
5% steps
o
m
m
Canopy closure
5% steps
o
m*
m*
Protection status
code
o
m
m
Fencing
code
o
m
m
Non-timber utilisation in the plot code
o
m
m
Non-timber utilisation in the
buffer zone
code
o
m
m
Management type
code
o
m
m
Intensity of management in the
plot
code
o
m
m
Intensity of management in the
buffer zone
code
o
m
m
Silvicultural system
code
o
m
m
Forest ownership
code
o
m
m
Estimated year of final cutting
code
o
m**
m**
Canopy gaps
code
o
m
m
Stand rotation number
integer
o
m
m
NFI status
Y/N
m
o
o
Other observations
text
o
o
o
*: mandatory only for plots with inhomogeneous canopy closure (e.g. due to severe damage caused by storm or
biotic agents). **: unless the stand is managed to keep a permanent cover of adult trees.

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5.1.2.1 Stand history
The continuity of forest cover is of relevance for a number of ecological forest functions,
including forest species composition. Stand history is reported in 5 classes according to
Bastrup-Birk et al. (2006):
Code
Description
1
Forested more than 300 years
2
Forested more than 100 years
3
Forested 25 - 100 years ago
4
Forested in the past 25 years
9
Unknown
5.1.2.2 Previous land use
Previous land use refers to the land use before the establishment of the first forest stand
monitored in the plot. It is reported in 9 classes:
Code
Description
1
Farmland, cropland
2
Grassland
3.1
Shrubland, including heathland / moors
4.1
Wetland
5
Primary forest
5.1
Forest and woodland (other than primary forest)
6
Other
7
Reclaimed land from mining or industrial activities
9
Unknown
5.1.2.3 Origin of current stand
The origin of the stand on the plot is reported in 5 classes according to Bastrup-Birk et al.
(2006):
Code
Description
1
Planted
2
Seeded
3
Natural regeneration
4
Mixed
9
Unknown
5.1.2.4 Main tree species
The tree species dominating the forest canopy in terms of canopy closure of the plot is
reported using a three-digit code (see online documentation).

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5.1.2.5 Type of tree species mixture
The type of tree species mixture on the plot is reported in 6 classes (Anonymous 2005):
Code
Description
1
Monoculture
2
Single tree-wise mixture
3
Group-wise mixture
4
Mixture by layers
9
Irregular, none of the above
99
Unknown
Monoculture refers to a tree population in which more than 90 % of the stand basal area
consists of one tree species.
5.1.2.6 Top height
Top height is defined as the mean height of the 100 trees with the largest diameter at breast
height (dbh) per ha. It can be derived from measured values (usually the case on Level II
plots) or from estimates.
5.1.2.7 Determination of top height
The method of determination of top height is to be indicated in 7 classes.
Code
Description
1
All heights measured and top height calculated from them
2
Heights of at least 10 trees of the 100 thickest were measured
3
Top height was calculated based on earlier measurement of all relevant trees
4
Top height was calculated based on earlier measurement of at least 10 trees of the
100 thickest trees
5
Top height was calculated based on locally adapted dbh/height tables
9
Other method (please specifiy in data accompanying report)
99
Unknown
5.1.2.8 Forest type
The forest type of the plot is reported following the nomenclature of the European
Environment Agency (EEA 2006), and further developed by UNECE/FAO (2010): see online
documentation on the ICP Forests website.
5.1.2.9 Age class
The mean age of the dominant tree story is given in 20-year age classes between ≤20 years
and >120 years or coded as irregular for uneven-aged stands (see online documentation on
the ICP Forests website).

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5.1.2.10 Number of tree layers
The number of tree layers is reported in 5 classes (Anonymous 2005):
Code
Description
1
One Layer
2
Two layers (each with a minimum of 10 % coverage)
3
Multilayered (each with a minimum of 10% coverage)
9
Irregular
99
Unknown
5.1.2.11 Coverage of tree layers
The coverage of each layer is reported in 5 % steps; only layers are included that have at
least a 10 % coverage. The sum of the coverage of all tree layers may be > 100 %. The
coverage of a tree layer is estimated as the proportion of the plot area covered by the vertical
projection of living branches and foliage of that layer. (Note: If the subplots for ground
vegetation can be assumed to be representative of the plot area, the assessments made of
the coverage of the tree layer and of the high shrub sublayer during the ground vegetation
survey can be used to estimate the coverage of tree layers at the plot scale).
5.1.2.12 Canopy closure
Canopy closure is defined as the proportion of sky hemisphere obscured by vegetation when
viewed from a single point It can be clearly distinguished from canopy cover which is the
proportion of an area covered by the vertical projection of tree crowns (cf. Jennings et al.
1999). Canopy closure is directly measured with optical methods. A view angle of 45°
(equalling 3 rings of the LAI-2200 sensor) is to be employed during its assessment in ICP
Forests for standardization purposes. Canopy closure represents the complement of the
measured gap fraction:
Canopy closure = 100% - gap fraction (45°)
Optical measurements to derive canopy closure should preferentially be made in the month
of maximum foliation. A range of different assessment methods is acceptable as long as they
have been validated against hemispherical photographs (cf. Manual Part XVII). Canopy
closure must be evaluated from multiple sampling points evenly distributed over the plot
area.
5.1.2.13 Protection status
The protection status of the monitoring plot is described following the MCPFE classification
(MCPFE 2006).
MCPFE Class 1: Main Management Objective ‘Biodiversity’:
•
MCPFE Class 1.1: No Active Intervention
No active, direct human intervention is taking place. Activities other than limited public
access and non-destructive research not detrimental to the management objective are
prevented in the protected area.
•
MCPFE Class 1.2: Minimum Intervention
Human intervention is limited to a minimum. Activities other than listed below are prevented
in the protected area: ungulate/game control, control of diseases/insect outbreaks2, public

2 In case of expected large disease/insect outbreaks control measures using biological methods are allowed
provided no other adequate control possibilities in the buffer zone are feasible.

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access, fire intervention, non-destructive research not detrimental to the management
objective, subsistence resource use3.
•
MCPFE Class 1.3: Conservation Through Active Management
A management with active interventions directed to achieve the specific conservation goal of
the protected area is taking place. Any resource extraction, harvesting, silvicultural practices
detrimental to the management objective, as well as other activities negatively affecting the
conservation goal are prevented in the protected area.
•
MCPFE Class 2 : Main Management Objective ‘Protection of Landscape and Specific
Natural Elements’
Interventions are clearly directed to achieve the management goals landscape diversity,
cultural, aesthetic, spiritual and historical values, recreation, specific natural elements. The
use of forest resources is restricted. A clear long-term commitment and an explicit
designation as specific protection regime defining a limited area are existing. Activities
negatively affecting characteristics of landscapes or/and specific natural elements mentioned
are prevented in the protected area.
•
MCPFE Class 3 : Main Management Objective ‘Protective Functions’
The management is clearly directed to protect soil and its properties or water quality and
quantity or other forest ecosystem functions, or to protect infrastructure and managed natural
resources against natural hazards. Forests and other wooded lands are explicitly designated
to fulfil protective functions in management plans or other legally authorised equivalents. Any
operation negatively affecting soil or water or the ability to protect other ecosystem functions,
the ability to protect infrastructure and managed natural resources against natural hazards is
prevented.
5.1.2.14 Fencing
Fencing is reported in 3 classes according to Bastrup-Birk et al. (2006):
Code
Description
1
Fenced
2
Not fenced
3
Fenced in parts
5.1.2.15 Non-timber utilization in the plot
Non-timber utilisation is reported in 6 classes:
Code
Description
1
Grazing
2
Firewood collection
3
Litter raking
4
Other
9
No non-timber utilization
99
Unknown
Only regular non-timber utilization is to be reported which may have a measurable impact on
nutrient and water cycles. Very occasional utilizations are not to be reported.

3 Subsistence use to cover the needs of indigenous people and local communities, in so far as it will not adversely
affect the objectives of management.

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5.1.2.16 Non-timber utilization in the buffer zone
Same definition and classes as for non-timber utilization in the plot.
5.1.2.17 Management type
Management type is reported in 4 classes:
Code
Description
1
High forest
2
Coppice without standards
3
Coppice with standards
99
Unknown
5.1.2.18 Intensity of management in the plot
Intensity of management in the plot is reported in 4 classes according to Bastrup-Birk et al.
(2006):
Code
Description
1
Unmanaged (no evidence)
2
Management (evidence but more than 10 years ago)
3
Managed (within the last 10 years)
99
Unknown
5.1.2.19 Intensity of management in the buffer zone
Same definition and classes as for intensity of management in the plot.
5.1.2.20 Silvicultural system
Silvicultural system at the site is reported in 5 classes (adapted from Anonymous 2005):
Code
Description
1
Clearcut system
2
Clearcut system with reserves
3
Selection system
4
Shelterwood system
99
Unknown
According to the Silvicultural-Systems Handbook for British Columbia (2003), terms can be
defined as below:
•
The clearcut system manages successive even-aged stands by cutting the entire
stand of trees at planned intervals (the rotation) then regenerating and tending a new
stand in place of the old.
•
Reserves are forested patches or individual trees retained during harvesting to
provide habitat, scenic, biodiversity, or other values, for at least one rotation. Any
incidental seed or shelter to the regenerating stand and site that reserve trees supply
is secondary to their purpose as reserve trees. Standards in coppice are a kind of
reserve.
•
Selection systems remove mature timber either as single scattered individuals or in
small groups at relatively short intervals, repeated indefinitely, where an uneven-aged
stand is maintained.

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•
In a shelterwood system the old stand is removed in a series of cuttings to promote
the establishment of a new even-aged stand under the shelter of the old one.
Generally, shelterwood systems aim at natural regeneration, although some planting
may occur to diversify the species mix, bolster stocking and introduce improved seed.
5.1.2.21 Forest ownership
Forest ownership is reported in classes following the FAO Forest Resource Assessment
2010 (FRA 2010) (https://icp-forests.org/documentation/ExplanatoryItems/23.html)
•
Public ownership: forest owned by the State, by administrative units of the public
administration, or by institutions or corporations owned by the public administration.
•
Private ownership: forest owned by individuals, families, communities, private co-
operatives, corporations and other business entities, private religious and educational
institutions, pension or investment funds, NGOs, nature conservation associations and
other private institutions.
- Individuals: Forest owned by individuals and families.
- Private business entities and institutions: Forest owned by private corporations, co-
operatives, companies and other business entities, as well as private non-profit
organizations such as NGOs, nature conservation associations, and private religious
and educational institutions, etc.
- Local communities: Forest owned by a group of individuals belonging to the same
community residing within or in the vicinity of a forest area. The community members are
co-owners that share exclusive rights and duties, and benefits contribute to the
community development.
- Indigenous or tribal communities: Forest owned by communities of indigenous or tribal
people.
•
Other types of ownership: Other kind of ownership arrangements not covered by the
categories above. Also includes areas where ownership is unclear or disputed.
5.1.2.22 Estimated year of final cutting
Unless the stand is managed to keep a permanent cover of adult trees, the year of the final
cutting must be approximately estimated (while assuming that no unplanned disturbance will
destroy the stand earlier).
5.1.2.23 Canopy gaps
Stand heterogeneity is evaluated with the cumulated area of large gaps in the canopy (gaps
larger than those caused by thinning operations) due to e.g. storm damages. This is reported
as a percentage of the plot area in 3 classes (less than 10 %, from 10 % to 50 %, more than
50 %).
5.1.2.24 Stand rotation number
The stand rotation number aims to count the successive tree populations that have been
monitored in the same plot area. It starts from 1 with the first forest stand monitored since
plot installation.

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5.1.3 Management operations and natural disturbances
All noticeable forest management operations and all natural causes of tree losses in Level II
plots since plot installation – and even from earlier if the information is available – must be
listed, dated (as precisely as possible) and documented (as far as known), so that they can
be taken into account as potential explanatory factors of ecosystem responses. This
information must be updated at least every 5 years. The known absence of such events over
a given time period is also useful information to be reported as well. Table 3 presents an
overview of variables to be reported depending on the event type/category. Each variable is
explained in the following text.
To be properly described, some events may require to be recorded as a combination of
several lines in the same form. As an example, tree dieback due to bark beetles may be
followed by the harvest of dead trees (to be reported as one line for a damage due to biotic
agents + another line for sanitation cutting or final cutting), or dead trees can be left in the
plot (to be reported as a single line for damage). Another example can be that one
management operation or natural disturbance has different impacts in the plot area and in
the buffer zone, which can be reported into two separate lines so as two concomitant
operations conducted in each of the two areas with different attribute values.
Table 3: Quick reference of variables to be reported describing management operations and
natural disturbances (o – optional, m – mandatory)
Variable
Reporting
unit/type/format
Related event
types/categories
Target plot type
Level I
Level II
standard
Level II
core
Event type
Code
All
o
m
m
Event location
Code
o
m
m
Starting date
Date
o
m
m
Ending date
Date
o
m
m
Number of trees before
Number per ha
Disturbance,
Felling, Cleaning,
Creating
pathways
o
o
o
Loss in trees
% number per
ha
o
o
o
Stand basal area before
m² par ha
o
o
o
Loss in stand basal area
%
basal
area
per ha
o
o
o
Cutting/planting/sowing
tools
Code
Felling, cleaning,
creating
pathways,
planting, sowing
o
o
o
Logging method
Code
Felling
o
o
o
Extraction tools
Code
o
o
o
Extraction method
Code
o
o
o
Slash disposal
Code
o
o
o
Size of woody residues
cm
o
o
o
Soil
compaction
under
pathways
Yes/No/Possible
o
o
o
Soil compaction over the
whole area
Yes/No/Possible
o
o
o
Used product/material
Text
All but
Disturbance
o
o
o
Chemical composition
Text
Liming,
Fertilization,
Chemical
treatment
o
o
o
Quantity
of
input
per
hectare
kg/ha
o
o
o
Method of application
Text
o
o
o

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Aim of treatment
Code
Chemical
treatment, Soil
mechanical
preparation
o
o
o
Main targeted plant species Code
Chemical
treatment,
Formative
pruning, Pruning,
Cleaning,
Weeding
o
o
o
Detailed site preparation
type
Code
Site preparation
o
o
o
Thickness of prepared soil
cm
Soil mechanical
preparation
o
o
o
Share of handled area
% total area
Soil mechanical
preparation,
creating
pathways
o
o
o
Sown/planted tree species
Code
Sowing, Planting
o
o
o
Seed provenance – country Code
o
o
o
Seed provenance – locality
Text
o
o
o
Planting stock type
Code
Planting
o
o
o
Seedling age
Years
o
o
o
Seedling height
Cm
o
o
o
Management
system
in
forest nursery
Code
o
o
o
Share of living seedlings
one year after plantation
% number per
ha
o
o
o
Height of pruning
m
Pruning
o
o
o
Density of individuals
Number per ha
Sowing, Planting,
Formative
pruning, Pruning,
Cleaning,
Weeding
o
o
o
Other information
Text
All
o
o
o

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5.1.3.1 Event type
The types of event are described by codes ordered by categories as following:
Code
Description
Category
00
No event (known absence of any kind of event)
No event
01
No management operations (known absence of any of them)
02
No natural disturbances (known absence of any of them)
D1
Damage – storm
Disturbance
D2
Damage – fire
D3
Damage – biotic agents
D4
Damage – abiotic agents (other than storm and fire)
S1
Soil – mechanical preparation
Site preparation
S2
Soil – liming
S3
Soil – fertilization
S4
Slash removal
S5
Stumping
F1
Thinning / Selection cutting
Felling
F2
Sanitation cutting / Salvage cutting
F3
Shelterwood cutting
F4
Final cutting
N1
Weeding
Non-remunerative
silvicultural
operations
N2
Cleaning
N3
Planting
N4
Sowing
N5
Pruning
N6
Formative pruning
N7
Cutting of vines to preserve tree health
I1
Creating / maintaining a drainage system
Infrastructure
I2
Creating / maintaining pathways for pedestrians
I3
Creating / maintaining pathways for harvesting machines
I4
Fence installation
I5
Fence removal
I6
Cleaning to preserve proper conditions for monitoring activities
C1
Chemical treatment of the vegetation
Chemical
99
Other events – to be described in other observations or a DAR-Q
-
As adapted from Ford-Robertson & Winters (1983):
•
Weeding is a cultural operation eliminating or suppressing undesirable vegetation,
mainly herbaceous, during the seedling stage of a forest stand and therefore before
the first cleaning, so as to reduce competition with the seedling stand.
•
Cleaning is a cultural operation eliminating or suppressing undesirable vegetation,
mainly woody (and including climbers), during the sapling stage of a forest stand and

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therefore before – or at the latest along with – the first thinning, so as to favour the
better trees.
•
Thinning is a felling made in an immature stand in order primarily to accelerate
diameter increment but also, by suitable selection, to improve the average form of the
trees that remain, without permanently breaking the canopy.
•
Selection cutting is the annual or periodic removal of trees (particularly the mature),
individually or in small groups from an uneven-aged forest in order to realize the yield
and establish a new stand of irregular structure (cf. selection systems).
•
Salvage cutting is the exploitation of trees that are dead, dying or deteriorating
(because overmature or materially damaged by fire, wind, insects, fungi, or other
injurious agents) before their timber becomes economically worthless.
•
Sanitation cutting is the removal of dead, damaged or susceptible trees, essentially to
prevent the spread of insects or pathogens.
•
Shelterwood cutting is any regeneration cutting in a more or less regular and mature
stand, designed to establish a new stand under the protection (overhead or side) of
the old (cf. shelterwood systems).
•
Final cutting is the removal of the last trees left in a stand.
Besides silvicultural purposes, cutting operations primarily intended to maintain the
infrastructure are to be reported as such. They include the creation or maintenance of
pathways, either for pedestrians or for harvesting machines. The removal of some of the
understory vegetation e.g. to preserve the visibility of canopy crowns or to make room for
measurement or sampling devices is to be reported as cleaning to preserve proper
conditions for monitoring activities.
5.1.3.2 Event location
The location of the event is described as one of the following codes: in the plot, in the buffer
zone, or in both the plot and buffer zone.
5.1.3.3 Starting date
For any actual event, if the exact starting date is unknown, the closest known date when the
event had not started yet is to be reported instead, so as to include the potential uncertainty
into the time interval. Inversely, periods of known absence of a kind of event must be
reported as strictly excluding time intervals reported for actual events of this kind (i.e. with no
overlapping with the latter).
5.1.3.4 Ending date
For any actual event, if the exact ending date is unknown, the closest known date when the
event was finished is to be reported instead, so as to include the potential uncertainty into the
time interval. Inversely, periods of known absence of a kind of event must be reported as
strictly excluding time intervals reported for actual events of this kind (i.e. with no overlapping
with the latter).
5.1.3.5 Number of trees before
The number of living trees before any disturbance or felling or cleaning operation is to be
reported per hectare.
5.1.3.6 Loss in trees
The loss in trees due to any disturbance or felling or cleaning operation is to be reported as a
percentage of the number of trees per hectare before the event.

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5.1.3.7 Stand basal area before
The stand basal area before any disturbance or felling or cleaning operation is to be reported
in m²/ha.
5.1.3.8 Loss in stand basal area
The loss in stand basal area due to any disturbance or felling or cleaning operation is to be
reported as a percentage of stand basal area per hectare before the event.
5.1.3.9 Cutting/planting/sowing tools
Cutting trees (during felling and cleaning operations and when creating/maintaining
pathways) or planting or sowing can be done either with tools hold in hands (e.g. chainsaw),
or with forestry vehicles (e.g. harvester, equipped tractor) which may cause physical
damages to the soil. This is to be reported in 4 classes.
Code
Description
1
Tools hold in hands
2
Forestry vehicle
3
Mixed
99
Unknown
5.1.3.10 Logging method
The method used to cut trees is to be described in 3 classes. This is important to know
whether the nutrients especially contained in fine branches and leaves/needles may have
been exported from the ecosystem.
Code
Description
1
Trees are cut into pieces where they have fallen down (before extraction)
2
Whole trees are extracted from the area, then cut into pieces outside
99
Unknown
5.1.3.11 Extraction tools
The tools used to extract fallen wood from the area are to be reported in 6 classes.
Code
Description
1
Forestry vehicle inside the area
2
Cable skidder positioned outside the area
3
Human or animal power
4
Aerial cableway or aircraft
5
Mixed tools including forestry vehicles inside the area
6
Mixed tools without forestry vehicles inside the area
9
Other (to be described in other information)
99
Unknown

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5.1.3.12 Extraction method
The method used to extract the fallen wood from the area is to be reported in 4 classes.
Code
Description
1
Skidding
2
Carrying
3
Mixed
99
Unknown
Skidding means that the wood slides more or less wholly along the ground, potentially
causing damages to the vegetation, and to the humus and topsoil layers. Carrying means
that the wood is wholly off the ground while being moved.
5.1.3.13 Slash disposal
The method used to treat the woody residues after a felling operation is to be reported in 4
classes.
Code
Description
1
Piling
2
Lopping and scattering
3
Burning
4
Harvesting
9
Other (to be described in other information)
99
Unknown
5.1.3.14 Size of wood residues
The large-end diameter threshold below which woody residues are left on the ground after a
felling is to be reported in cm.
5.1.3.15 Soil compaction under pathways
The compaction of the soil caused by felling operations on predefined pathways is to be
described as actually observed (“yes”), absent (“no”), or as “possible” (if harvesting machines
may have used predefined pathways but no field observation was made about the presence
or absence of impacts).
5.1.3.16 Soil compaction over the whole area
The compaction of the soil caused by felling operations on the whole area is to be described
as actually observed (“yes”), absent (“no”), or as “possible” (if harvesting machines may have
been driven through the area without restriction but no field observation was made about the
presence or absence of impacts).
5.1.3.17 Used product/material
The product or material used for a management operation event is to be described as text.
5.1.3.18 Chemical composition
The chemical composition of the product used for soil liming, soil fertilization, or chemical
treatment of the vegetation is to be reported.

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5.1.3.19 Quantity of input per hectare
For soil liming, soil fertilization, or chemical treatment of the vegetation, the input quantity is
to be reported in kg/ha.
5.1.3.20 Method of application
For soil liming, soil fertilization, or chemical treatment of the vegetation, the method used for
the application of the product is to be described as text.
5.1.3.21 Aim of treatment
The aim of a chemical treatment of the vegetation or of a soil mechanical preparation is to be
reported in classes as following.
Code
Description
11
Soil mechanical preparation – Mainly aiming to restore soil physical properties
12
Soil mechanical preparation – Mainly aiming to help artificial regeneration
13
Soil mechanical preparation – Mainly aiming to help natural regeneration
19
Soil mechanical preparation – With another aim (to be described)
21
Chemical treatment of the stumps of cut trees against pathogenic fungi
22
Chemical treatment of trees against processionary moth
29
Other chemical treatment to help the targeted plant species (to be described)
31
Chemical treatment to eliminate the targeted plant species
99
Unknown
5.1.3.22 Main targeted plant species
The main plant species targeted is to be reported following the same code list as defined for
ground vegetation assessments (cf. Manual Part VII.1). It can be the main species to which a
chemical treatment is applied, or the main tree species benefitting from cultural operations
(formative pruning, weeding, cleaning, pruning).
5.1.3.23 Detailed site preparation type
Site preparation operations are to be further described in classes as following.
Code
Description
11
Soil mechanical preparation – Any kind limited to the humus and topsoil (<10 cm
depth)
12
Soil mechanical preparation – Ploughing
13
Soil mechanical preparation – Deep loosening with a subsoiler
14
Soil mechanical preparation – Bed shaping (to build ridges in wet sites)
15
Soil mechanical preparation – Preparation by isolated spots for one or few seedlings
19
Soil mechanical preparation – Other (to be described in other information)
21
Soil liming – With crushed limestone
22
Soil liming – With crushed dolomite
23
Soil liming – With wood ash
29
Soil liming – With another type of material (to be described in other information)
31
Soil fertilization – With synthetic fertilizer
32
Soil fertilization – With sewage sludge

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33
Soil fertilization – With paper mill sludge
39
Soil fertilization – With another type of material (to be described in other information)
41
Slash removal – Windrowing
42
Slash removal – Burning
43
Slash removal – Harvesting
44
Slash removal – Grinding and scattering
49
Slash removal – Other (to be described in other information)
51
Stumping – Excavating then windrowing
52
Stumping – Excavating then burning
53
Stumping – Harvesting
54
Stumping – Grinding and scattering
59
Stumping – Other (to be described in other information)
99
Unknown
5.1.3.24 Thickness of prepared soil
The maximum depth reached during soil mechanical preparation is to be reported in cm.
5.1.3.25 Share of handled area
For soil mechanical preparation and for the creation or maintenance of pathways, the share
of handled area is to be reported as a percentage of the whole area.
5.1.3.26 Sown/planted tree species
The sown or planted tree species is to be reported using a three-digit code (see online
documentation).
5.1.3.27 Seed provenance – country
The country – or state of the United States of America – of provenance of the seeds of the
tree species used in artificial regeneration (either sowed or planted) is to be reported with a
code (see online documentation).
5.1.3.28 Seed provenance – locality
The locality of provenance of the seeds of the tree species used in artificial regeneration
(either sowed or planted) is to be reported as text.
5.1.3.29 Planting stock type
The planting stock type is to be reported in 3 classes.
Code
Description
1
Bare-rooted seedlings
2
Container-grown seedlings
99
Unknown
5.1.3.30 Seedling age
The age of the seedlings at the time of the plantation is to be reported in years.

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5.1.3.31 Seedling height
The mean height of the seedlings at the time of the plantation is to be reported in cm.
5.1.3.32 Management system in forest nursery
To promote the development of the rooting system of the seedlings, management system in
forest nursery may include transplanting or undercutting operations. This is to be reported in
4 classes.
Code
Description
1
With transplanting
2
With undercutting
3
Without transplanting or undercutting
99
Unknown
5.1.3.33 Share of living seedlings one year after plantation
The success of a plantation can be evaluated through the percentage of planted seedlings
that are still living one year later.
5.1.3.34 Height of pruning
In case of pruning (excluding formative pruning), the height of pruning is to be reported as
the maximum height below which branches were removed in meters.
5.1.3.35 Density of individuals
The density of individuals is a quantitative indicator of the effort made in any kind of non-
remunerative silvicultural operation. In case of sowing or planting, it is respectively the
number of seeds or seedlings artificially installed per hectare. In case of weeding, cleaning or
pruning, it is the number per hectare of seedlings, saplings, poles or trees, to the benefit of
which the operation is made.
5.1.4 Surveys and measurements at plot and site level
Several assessments are carried out within individual surveys at the large-scale plots
(Level I) and/or at the intensive monitoring (Level II) sites. Table 4 provides a quick reference
to the various surveys foreseen, their target plots and expected frequency. Specific
measurements foreseen within individual surveys as well as their status (mandatory/optional)
are described and reported in detail in the individual parts of the Manual, also indicated in
Table 4.

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Table 4: Quick reference for surveys to be carried out on different plot types (Install – at plot instalment, project – within dedicated projects;
*: recommended frequency may differ from the frequencies specified in the respective Manual Parts)
Survey
Provide data on
Methods
described
in
Target plots and frequency of
assessment/measurement/sampling*
Level I
Level II
Level II core
Plot description
Location, size and status of the plot
Part II
Install
Install
Install
Stand description
Basic characteristics of the stand
Part II
5 yrs
5 yrs
5 yrs
Management operations
and natural disturbances
Forest management operations and natural
disturbances
Part II
-
5 yrs
5 yrs
Tree condition
Indicators of crown, branches and stem status of
the trees
Part IV
1 yr
1 yr
1 yr
Tree growth and yield
Actual periodic growth of the stand and of individual
trees
Part V
-
5 yrs
5 yrs
Tree growth and yield
(intensive)
Intra-annual and annual growth of individual trees
Part V
-
-
1 yr to
continuously
Tree phenology
Timing of the annual development stages of forest
trees (plot level)
Part VI
-
-
weekly
Tree phenology (intensive)
Timing of the annual development stages of forest
trees (individual tree level)
Part VI
-
-
continuously
Ground vegetation
Species richness and abundance
Part VII
project
5 yrs
5 yrs
Ozone injury on plants
Presence on visible injury attributable to
tropospheric ozone
Part VIII
-
-
1 yr
Meteorological
measurements
Basic (T, P, wind speed) meteorological variables,
soil moisture and temperature
Part IX
-
continuously
continuously
Soil sampling and analysis
Soil profile and chemical concentration of elements
and ions in soil solid phase. Information on soil
water retention characteristics.
Part X
project
10-20 yrs
10-20 yrs
Soil solution collection and
analysis
Chemical content of elements and ions in soil liquid
phase
Part XI
-
-
1-2 weeks
Foliar sampling and
analysis
Chemical concentration of elements in foliage of
trees
Part XII
project
2 yrs
2 yrs
Sampling and analysis of
litterfall
Amount, composition and chemical content of litter
Part XIII
-
-
2-4 weeks
Sampling and analysis of
deposition
Chemical concentration of elements and ions in
open field, throughfall and stemflow precipitation
Part XIV
-
1-2 weeks
1-2 weeks
Ambient air quality
Concentration of SO2, NOx, O3 in the air
Part XV
-
-
1-2 weeks
Leaf area index
Total canopy leaf area
Part XVII
-
-
1 yr

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5.2 Quality Assurance and Data Quality Requirements
At its 22nd Task Force Meeting in 2007, ICP Forests adopted an overall Quality Assurance
(QA) perspective. The overall concept and the QA components are described in Part III,
while individual QA/QC measures are reported in detail in individual Manual Parts for the
respective survey based exclusively on field measurements, and in Part XVI for
investigations involving laboratory analysis.
6 Data Submission
Data is submitted yearly to the central data storage facility at the ICP Forests Programme
Co-ordinating Centre (PCC) using formats specified in standardized documents available
under ICP Forests website.
6.1 Data Transmission to Programme Co-ordinating Centre
Data will be sent to the PCC using a data submission web application at any time of the year,
however, deadlines for annual reporting should be considered. Data is submitted survey by
survey and year by year. Thus, each NFC has to submit a complete set of files/forms per
survey and year via the submission module. In general, this set includes a reduced plot file
and data files. Additionally, all files containing respective QA/QC information (e.g. results of
laboratory ring tests or field comparison courses) and data accompanying reports (word
documents) should be submitted together with the data files.
An exception to the annual submission is the general plot information which is submitted only
in case of a need for updating the ICP Forests database (e.g. new plots or improved/updated
plot relevant information).
6.2 Data Validation
Submitted data will be tested in three stages: Compliance, Conformity and Uniformity tests
(Houston & Hiederer 2009). Only those data which pass those stages successfully will be
uploaded to the ICP Forests database.
Compliance tests will test the format of the submitted data.
Conformity tests focus on the submitted values and compare them with test ranges or test
their relation to the values of other attributes or of the same attribute from former years.
Uniformity tests check the spatial and temporal comparability of the data by the production of
graphs and maps. Whereas compliance and conformity checks will be applied in time by the
submission application of the database during the transmission procedure, uniformity checks
will be applied by the staff of the PCC data centre.

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7 References
Anonymous, 2005: Stand structure assessments including deadwood within the EU/ICP Forests
Biodiversity Test-Phase (ForestBIOTA). http://www.forestbiota.org/ (accessed 17 June 2010).
Bastrup-Birk A, Neville P, Chirici G, Houston T, 2006: The BioSoil Forest Biodiversity Field Manual.
http://www.icp-forests.org/EPbiodiv.htm (accessed 17 June 2010).
Boulanger V., Dupouey J.L., Archaux F., Badeau V., Baltzinger C., Chevalier R., Corcket E., Dumas
Y., Forgeard F., Marell A., Montpied P., Paillet Y., Picard J.F., Saïd S., Ulrich E., 2018.
Ungulates increase forest plant species richness to the benefit of non-forest specialists. Glob
Change Biol, 24(2): e485-e495, DOI: 10.1111/gcb.13899.
British Columbia. Ministry of Forests. Forest Practices Branch, 2003. Silvicultural Systems Handbook
for British Columbia. For. Pract. Br., BC. Min. For., Victoria, BC..
Cozzi S, Ferretti M, Lorenz M, 2002: Quality assurance for crown condition assessment in Europe.
UN/ECE, Geneva: 111 p.
EEA, 2006: European Forest types. Categories and types for sustainable forest management
reporting and policy. EEA Technical Report No 9/2006. European Environment Agency.
Ferretti M, 2010: Harmonizing forest inventories and forest condition monitoring - the rise or the fall of
harmonized forest condition monitoring in Europe? iForest 3:1-4. DOI: 10.3832/ifor0518-003.
Ford-Robertson FC, Winters RK, 1983. Terminology of forest science technology practice and
products. 2nd edition revised and expanded. Bethesda (USA), Society of American foresters,
370 p.
FRA, 2010: Global forest resources assessment. [www.fao.org/forestry/fra, accessed 31 March 2016].
Houston TD, Hiederer R, 2009: Applying quality assurance procedures to environmental monitoring
data: a case study. J Environ Monit 11:774–781. DOI: 10.1039/B818274B.
Jennings SB, Brown ND, Shel D, 1999: Assessing forest canopies and understorey illumination:
canopy
closure,
canopy
cover
and
other
measures.
Forestry
72(1):59-73.
DOI:
10.1093/forestry/72.1.59
Köhl M, Innes JL, Kaufmann E, 1994: Reliability of differing densities of sample grids used for the
monitoring of forest condition in Europe., Environ Monit Assess 29:201-220. DOI:
10.1007/BF00547987.
Köhl M, Traub B, Päivinnen R, 2000: Harmonisation and standardisation in multi-national
environmental statistics – mission impossible? Environ Monit Assess 63:361-380. DOI:
10.1023/A:1006257630216.
MCPFE, 2006: MCPFE information document on data collection and compiling the statistics on
protected and protective forest and other wooded land in Europe. Warsaw, 16 p.
[http://www.foresteurope.org/docs/reporting/MCPFE_INFO_DOC
_on_data_collection_on_Protected_forests.pdf, assessed 31 March 2020].
Neumann M, 1993: Forest Damage Assessments in Austria. Environ Monit Assess 28:183-188. DOI:
10.1007/BF00547036.
Palmer MW, 1993: Potential biases in site and species selection for ecological monitoring. Environ
Monit Assess 26:277–282. DOI: 10.1007/BF00547504.
Parr TW, Ferretti M, Simpson IC, Forsius M, Kovács-Láng E, 2002: Towards a long-term integrated
monitoring programme in Europe: Network design in theory and practice. Environ Monit Assess
78:253–290. DOI: 10.1023/a:1019934919140.
UNECE/FAO, 2010: Annex to Enquiry State of Forests and Sustainable Forest Management in
Europe
2011.
New
European
Forest
Types.
Complementary
documentation.
http://timber.unece.org/fileadmin/DAM/publications/european-forest-type.pdf
(accessed
18
March 2010).
Vos P, Meelis E, Ter Keurs WJ, 2000: A framework for the design of ecological monitoring programs
as a tool for environmental and nature management. Environ Monit Assess 61:317–344,. DOI:
10.1023/A:1006139412372

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Annex I – Recommendations for functional integration of
Level I and National Forest Inventories for tree condition
assessments
Marco Ferretti
(adapted after Ferretti M. 2010: Harmonizing forest inventories and forest condition
monitoring - the rise or the fall of harmonized forest condition monitoring in Europe? iForest
3:1-4).
Adopting Level I methods on NFI plots
In addition to the ongoing annual assessments of tree condition on the existing Level I plots,
Level I variables are assessed on (a subsample of) NFI plots (to be selected according to the
country-specific NFI design). Permanent numbering on trees should be avoided in order to
keep the plot as anonymous and undisturbed as possible. The Level I assessment on the
selected NFI plots may be carried out at every NFI repetition (e.g. every 5 or 10 years) to
favour data integration.
Adopting NFI methods on Level I plots
At the same time, the country-specific NFI plot design and variables are adopted on the
existing Level I plots. This includes the selection of new sample trees on existing Level I plots
while former sample trees at the Level I plots are retained. Annual Level I assessments are
carried out on the old as well as on the newly selected sample trees.
Advantages
This functional integration will result in several advantages:
•
the existing time series is maintained by the continuation of the assessment on
existing sample trees;
•
a comparison between the two datasets (Level I and NFI) will be possible at defined
time intervals (e.g., at each NFI cycle);
•
combined and more precise estimates may be possible at defined time intervals (e.g.,
at each NFI cycle).
This latter possibility depends, however, on the nature of the Level I network (its origin and
target statistical population), and on the assumption that Level I and NFI samples concern
the same statistical population. NFI plots will stay undisturbed. The disadvantage is a slight
increase of costs (Level I plots adaptation in the first year; some new attributes in addition on
NFIs every 5 or 10 years).

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Annex II – Recommendations for converting cross-cluster
plots into fixed area Level I plots
Marco Ferretti
Figure A1 shows an approach to convert a cross-cluster design (with undefined shape and
size) into a fixed area plot, while keeping the original sample trees. This kind of procedure is
applicable for different plot sizes (e.g., different radii, according to the country) and/or may
allow sub-sampling of trees (e.g. angle count sampling; concentric plots for smaller DBH
classes) in case of dense stands and/or stands with many small trees where the assessment
of all the trees is not feasible. This procedure can be of interest for those countries facing the
integration of NFI and Level I.
Note that – according to this procedure – data series on original sample trees can be kept. At
the same time, the adoption of a fixed area plot will favour the estimation process.

Figure A1: Example of change from a cross-cluster sample to a circular fixed area plot. Left,
cross-cluster plot with six trees (dark green ones) selected at each cardinal direction, 25 m from the
centre; middle, a 25 m radius plot is designed; right, the trees within the 25 m radius plot previously
not considered are now incorporated into the sample of trees (red ones). The old sample trees are
kept to ensure the continuation of the data series. The same procedure is applicable for different plot
sizes (e.g. 18 m radius). Drawing by M. Ferretti

N
N
N

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Annex III – Minor changes after 2020
Date
Minor change to latest published
version in 2020
Affected sections of this document
17.11.2021
NFI status is saved in STA table in the
database, not in PLT, because NFI status
might change after some years. In STA, it
can be updated every 5 years, but in PLT
the status would be static.
“NFI status” was moved from Table 1 to
Table 2.

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Annex IV – Should Level II plots entering the stand
regeneration stage be maintained under monitoring or
relocated?
None of these two options is perfect. Both have advantages and disadvantages, which are
summarized in the tables below, and which correspond to one another. Making a choice
between them requires to consider both practical and strategical points of view.
Several strategical implications should be considered:
-
Should the stand development stage be integrated as an additional explanatory factor
in the Level II monitoring? On one hand, studying the development of a stand over a
complete rotation period can be of great scientific interest. On the other hand, the
severe effects of a final cutting and the frequent changes during the early stages of
the development of a young stand may hide the impact of other environmental
changes, which are primarily targeted at by the ICP Forests’ scope and objectives. As
a result, if Level II plots which were generally installed in adult stands, begin to
consist of an increasing share of plots with young stands, the capacity of the network
to detect and evaluate impacts due to environmental changes by other major
stressors like air pollution and climate change may reduce.
-
The continuity of the data series can be better maintained if monitoring activities are
continued on the same plot during stand regeneration. But it is important to note that
in such a case the data will be heavily impacted by the sudden environmental
changes after a large natural disturbance or final cutting and following the
establishment of a new stand. However, if the continuity of the data series at the
scale of the whole network is to be considered, all plots are not likely to enter into the
regeneration stage at the same time and large-scale monitoring results will be greatly
affected by a significant proportion of plots in the regeneration stage.
-
The longer the plots are monitored at the same location, the more the potential biases
due to monitoring activities on the observed ecosystems – e.g. exclusion of ungulates
by fencing (Boulanger et al., 2018), diverging forest management practices inside
plots compared to the surrounding forest, soil trampling due to frequent assessments
– are likely to accumulate and become of predominant influence. In general, care
should be taken to minimize their occurrence and to quantify their impacts.
-
Relocating plots gives the opportunity to adapt the set of sampled forest ecosystems
to changes in the forest cover (e.g. forest expansion dynamics on former agricultural
lands or grasslands, changes in the relative importance of tree species in the forested
area) and/or to put more effort on ecological contexts where the impacts of climate
change are more likely to be observed (e.g. ecological margins of tree species
distribution).
Several practical consequences should be considered too:
-
Monitoring plots entering the regeneration stage requires efforts and methods
adapted to young stands. For example, trees can be too small for measuring some
variables (e.g. DBH), for installing some devices (e.g. litterfall traps, throughfall and
stemflow collectors), or for selecting permanent sample trees. They can also be too
numerous (especially in naturally-regenerated stands) for labelling and surveying all
of them on the whole plot area, and some may have to be cut for accessing the plot.
-
Stand establishment may fail. Monitoring plots at the same location may then no
longer be of interest.
-
Relocating plots requires additional resources when properly abandoning the
replaced plot (making additional assessments to properly end the data series,
precisely georeferencing the area and the monitoring devices to keep able to reuse

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the same location later, removing devices) and installing a new one (searching for a
proper location, installing devices, …).
Table A1: Advantages and disadvantages of maintaining under monitoring Level II plots that
have entered the stand regeneration stage.
Advantages
Disadvantages
1. Opportunity for studying forest
ecosystem dynamics over a complete
stand rotation including the
regeneration stage (which is only rarely
documented in the literature)
2. Maximizing site lifetime, and the length
of the data series that can be continuously
collected despite the practical difficulties
induced by young stands (e.g. solid soil,
flora, and all open-field surveys)
3. Knowledge about tree growth and
management practices from one forest
generation to the next (despite
discontinuity in growth survey due to stand
removal)
4. No need for moving sites (saving costs)

1. Need for more plots if it is intended to
consider stand development stage as an
additional factor while maintaining the
same capacity of the network to evaluate
the impacts of environmental changes
2. Need for protocols adapted to young
stand conditions and/or need to
interrupt some surveys until conditions
are suitable again (e.g. throughfall, litterfall,
growth survey of all trees in dense
naturally-regenerated stands)
3. Biases effects on monitored
ecosystems can accumulate over the
long term and become a predominant
factor
4. Risk for stand regeneration to fail and so
for wasting effort on monitoring plots that
are no longer of interest
5. Possibly no control on the main tree
species of the next generation to be
monitored (If the NFC has no influence on
forest management)

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Table A2: Advantages and disadvantages of relocating Level II monitoring plots that have
entered the stand regeneration stage.
Advantages
Disadvantages
1. Monitoring activities focused on
ecosystem responses to environmental
changes in adult forest stands (no
additional effect of stand regeneration
stage)
2. Maintaining optimal conditions for
monitoring activities thus maximizing
the number of variables that can be
surveyed
3. Reduction of accumulated biases
caused by monitoring activities to
observed ecosystems, when plots are
relocated
4. Opportunity to adapt the set of sampled
forest ecosystems by installing new
plots at a new location (e.g. to better
represent the main forest conditions, or to
increase the chance to detect impacts of
climate change)
5. Keeping the possibility to maintain
continuity in open-field surveys (if plots
are relocated nearby) and to keep
abandoned sites available for future
research
1. No evaluation of the effect of stand
development stages on the ecosystem
2. Data series start again from zero in new
plots : at least about 15 years are needed
to start considering trends in ecological
conditions
3. Also the knowledge on site condition,
stand growth and management start
again from zero in new plots (knowledge
acquired on the replaced plots can still be
made available in case they are reused
later)
4. Additional effort is needed to move plots
(to properly abandon the replaced plots and
to install new plots)