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General sampling guide for timber tracking. How to collect reference samples for timber identification

  • Thünen-Institut für Holzforschung
  • Agroisolab GmbH


This is a guide for the collection of reference samples of trees to enable the identification of species and/or geographical origin of woody material. To enable the implementation of the different laws regulating the trade in illegal wood, reference databases for various timber tracking tools are urgently needed for at least the most traded and endangered tree species. In addition, to optimise the use of wood/wood product identification (taxonomic identity or geographic origin) in support of law enforcement, the guide anticipates upcoming developments to combine different timber identification methods such as wood anatomy, DNA-based methods, stable isotopes, DART TOFMS and NIRS. This sampling guide is written to make sharing of samples between researchers specialised in different timber tracking methods possible, as samples should ideally come from the same location in the tree, from the same individual and from well-identified trees when combining methods.
General sampling guide
Task 2: Development of international standards and
GTTN database
Activity 2.1: International standards
Deliverable 2.1.1: Reviewed GTTN guidelines on
sampling of reference material
Date: 7 February 2019
Recommended citation:
Schmitz, N. (ed.), Blanc-Jolivet, C., Boner, M., Cervera, M.T., Chavesta, M., Cronn, R., Degen, B., Deklerck, V., Diaz-Sala, C.,
Dormontt, E., Ekué, M., Espinoza, E.O., Gasson, P., Gehl, D., Gehre, M., Haag, V., Hermanson, J.C., Honorio, E., Koch, G.,
Lancaster, C., Lens, F., Liendo-Hoyos, E.P., Martínez-Jarquín, S., Montenegro, R., Paredes-Villanueva, K., Pastore, T.,
Ramananantoandro, T., Rauber-Coradin, V.T., Ravaomanalina, H., Rees, G., Sebbenn, A.M., Tysklind, N., Vlam, M.,
Watkinson, C., Wiemann, M. 2019. General sampling guide for timber tracking. Global Timber Tracking Network, GTTN
Secretariat, European Forest Institute and Thuenen Institute.
The following document is an output from GTTN, which is coordinated by the European Forest Institute (EFI) and
funded by the German Federal Ministry for Food and Agriculture (BMEL). The information expressed in this document
are the views of the authors and do not necessarily represent those of the donor or of the European Forest Institute.
General sampling guide for timber tracking
How to collect reference samples for timber identification
Nele Schmitz
Authors*: Céline Blanc-Jolivet1, María Teresa Cervera2, Manuel Chavesta3, Richard Cronn4, Victor
Deklerck5, Carmen Diaz-Sala6, Eleanor Dormontt7, Peter Gasson8, David Gehl9, Volker Haag10, John C.
Hermanson11, Eurídice Honorio12, Cady Lancaster13, Frederic Lens14, Estephanie Patricia Liendo Hoyos15,
Sandra Martínez-Jarquín16, Rolando Montenegro3, Kathelyn Paredes Villanueva17,18, Tereza Pastore19,
Tahiana Ramananantoandro20, Harisoa Ravaomanalina21, Alexandre Magno Sebbenn22, Niklas
Tysklind23, Mart Vlam18, Charlie Watkinson24, Michael Wiemann11
With contributions from*: Markus Boner, Bernd Degen1, Marius Ekué, Edgard O. Espinoza25, Matthias
Gehre26, Gerald Koch10, Vera T. Rauber Coradin19, Gareth Rees27
We also thank Tom De Mil and Priwan Srisom for their photo contributions.
*Names are listed in alphabetical order.
Edition 7 Feb. 2019
Thünen Institute of Forest Genetics, Grosshansdorf, Germany
Centro de Investigación Forestal, El Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-
CIFOR), Madrid, Spain
Laboratorio de anatomía e identificación de maderas, Universidad Nacional Agraria la Molina, Lima, Peru
US Forest Service Research & Development, Washington, DC, USA
Laboratory of Wood Technology, Ghent University, Belgium
Dept. Ciencias de la Vida, Universidad de Alcalá, Madrid, Spain
University of Adelaide, Adelaide, Australia
Royal Botanic Gardens, Kew, UK
Environmental Investigation Agency, Washington, DC, USA
Thünen Institute of Wood Research, Bergedorf, Germany
US Forest Service Forest Products Laboratory, Madison, WI, USA
Instituto de Investigaciones de la Amazonía Peruana (IIAP), Iquitos, Peru
Wood Identification & Screening Center, USFS International Programs, National Forensics Laboratory, U.S. Fish
& Wildlife Service, Ashland, OR, USA
Naturalis Biodiversity Center, Leiden, The Netherlands
Autoridad de Fiscalización y Control Social de Bosques y Tierra, Santa Cruz de la Sierra, Bolivia
Department of Biochemistry and Biotechnology, CINVESTAV Unidad Irapuato, Irapuato, Mexico
Universidad Autónoma Gabriel René Moreno, Santa Cruz, Bolivia
Wageningen University & Research, Wageningen, The Netherlands
Laboratório de Produtos Florestais, Serviço Florestal Brasileiro, Brasília, Brazil
Mention Foresterie et Environnement, Ecole Supérieure des Sciences Agronomiques, Université d'Antananarivo,
Antananarivo, Madagascar
Mention Biologie et Ecologie Végétales, Faculté des Sciences, Université d'Antananarivo, Antananarivo,
Instituto Floresta de São Paulo, São Paulo, Brazil
Institut National de Recherche Agricole, Kourou, Guyane Française
Agroisolab UK Ltd, York, UK
National Forensics Laboratory, US Fish & Wildlife Service, Ashland, OR, USA
Laboratory for Stable Isotopes, Department for Isotope Biogeochemistry, Helmholtz-Centre for Environmental
Research, Leipzig, Germany
Elementar UK Ltd, Stockport, UK
Table of Contents
RATIONALE ............................................................................................................................................................ 3
ABBREVIATIONS ...................................................................................................................................................... 4
QUICK GUIDE .......................................................................................................................................................... 5
CHECK LISTS ........................................................................................................................................................... 6
Checklist preparatory work ............................................................................................................................ 6
Checklist fieldwork ......................................................................................................................................... 7
1. PREPARATORY WORK ............................................................................................................................. 8
1.1 CODE OF CONDUCT ............................................................................................................................................ 8
1.2 BUDGET ........................................................................................................................................................... 8
1.3 LOCAL SUPPORT ................................................................................................................................................ 9
1.3.1 Find a local partner institute ................................................................................................................. 9
1.3.2 Set up a local sampling team .............................................................................................................. 10
1.4 SAMPLING DESIGN ........................................................................................................................................... 10
1.4.1 Scientific set-up ................................................................................................................................... 10
1.4.2 Practical set-up ................................................................................................................................... 15
2. FIELD WORK .......................................................................................................................................... 17
2.1 SPECIES IDENTIFICATION IN THE FIELD................................................................................................................... 17
2.2 THE SAMPLE RECORD: COLLECTING TREE & SITE INFORMATION ................................................................................. 18
2.3 COLLECTING SAMPLES ....................................................................................................................................... 20
2.3.1 Overview of reference material to be collected enabling species/origin identification by all methods
..................................................................................................................................................................... 21
2.3.2 How to collect leaves, fruits and flowers > herbarium specimen and DNA analysis ........................... 22
2.3.3 How to collect wood samples > all timber identification methods ..................................................... 23
3. TRANSPORT & STORAGE OF SAMPLES AND DATA ................................................................................. 25
3.1 FOREST-TO-LAB SAMPLE CHAIN & SAMPLE QUALITY ................................................................................................ 25
3.2 SAMPLE STORAGE IN THE FIELD ........................................................................................................................... 25
3.3 SAMPLE TRANSPORT ......................................................................................................................................... 28
3.4 LONG TERM SAMPLE STORAGE ............................................................................................................................ 28
4. REFERENCES .......................................................................................................................................... 29
5. APPENDICES .......................................................................................................................................... 32
APPENDIX 1: ILLUSTRATIONS TO THE SAMPLING GUIDE .................................................................................................. 32
APPENDIX 2: SAMPLING MATERIAL & EQUIPMENT ....................................................................................................... 39
APPENDIX 3: EXAMPLES OF FORMS TO COLLECT FIELD DATA ........................................................................................... 40
This is a guide for the collection of
reference samples
of trees to enable the
identification of species and/or geographical origin of woody material. It is an
update of the sampling section of the GTTN standards and guidelines (Ekué 2014)
and builds further on a discussion initiated during a workshop held in Hamburg at
the Thünen Institute for Wood Research in 2014. If you are looking for support on
how to collect
test samples
, see the UNODC guide (UNODC 2016).
To enable the implementation of the different laws regulating the trade in illegal
wood, reference databases for various timber tracking tools are urgently needed for
at least the most traded and endangered tree species. The Global Timber Tracking
Network (GTTN) is building a central database where not only the reference data can
be stored but which will also function as a sample locator. Having a common
sampling guide will facilitate meaningful exchange of samples.
In addition, to optimise the use of wood/wood product identification (taxonomic
identity or geographic origin) in support of law enforcement, the guide anticipates
upcoming developments to combine (Paredes Villanueva 2018) different timber
identification methods (Dormontt
et al.
2015, Lowe
et al.
2016) such as wood
anatomy (Koch and Schmitt 2015, Helmling
et al.
2018), DNA-based methods
(Jolivet and Degen 2012, Blanc-Jolivet
et al.
2018, Chaves
et al.
2018), stable isotopes
et al.
in preparation, Vlam
et al.
2018), DART TOFMS (Lancaster
and Espinoza 2012, Espinoza
et al.
2015, Deklerck
et al.
2017, Paredes-Villanueva
et al.
2018) and NIRS (Pastore
et al.
2011, Bergo
et al.
2016, Snel
et al.
2018). This sampling
guide is written to make sharing of samples between researchers specialised in
different timber tracking methods possible, as samples should ideally come from the
same location in the tree, from the same individual and from well-identified trees
when combining methods.
This guide is intended for scientists, to provide all the information needed to get
the most out of sampling campaigns for timber identification purposes. This
information should allow setting up a sampling protocol adapted to the specific goal
of the research project, the conditions of the sampling area and the background of
the people who will do the sampling. Note that this guide is to collect reference
samples and hence relatively high amounts of samples from different individuals are
needed to take the variability of a species into account. Once reference data have
been developed for a tree species for one or more identification methods, however,
only one sample of an unidentified wooden object is often sufficient to determine its
AAC Assiettes Annuelles de Coupe (Annual Cutting Area)
°C Degrees Celsius
Ca. Circa
CITES Convention on International Trade in Endangered Species of wild
fauna and flora
Ø Diameter
DART TOFMS Direct Analysis in Real Time Time-of-Flight Mass Spectrometry
DBH Diameter at Breast Height
DF10 Document specifying the timbers extracted from the forest
DNA DeoxyriboNucleic Acid
for example
EUTR EUropean Timber Regulation
GPS Global Positioning System
GTTN Global Timber Tracking Network
ID Identification
Min. Minimum
NGO Non-Governmental Organisation
NIRS Near InfraRed Spectroscopy
Pvc Polyvinyl chloride
RH Relative Humidity
Sample ID Sample IDentity
UNODC United Nations Office on Drugs and Crime
Quick guide
Check lists
Checklist preparatory work
Before all else:
1. Did I consider costs for permits, transport of the sampling team, transport of
samples back to the lab, payment of sampling team, accommodation and
subsistence, sampling material and equipment? 1.1-1.2
2. Did I get permits to do research in the different sampling sites, to collect
samples and to export and import them? 1.1-1.2
3. Did I explore the available local knowledge and expertise and find local
partners to build a local sampling team? 1.3
Specifying the aim of the mission:
4. Did I clarify the research question of the sampling campaign? 1.4.1
5. Did I do a scientific literature review on the species and sites that will be
sampled to collect all basic information required? 1.4.1
To decide beforehand:
6. Did I decide on how to select sites and trees within sites? Table 1, 1.4.1
7. Did I decide on the amount of material that will be sampled (based on budget
and essential quantities)? Table 1, 2.3.1
8. Did I decide on the site and tree data that will be collected and how? 2.2,
3.1, appendix 3
9. Did I decide on how samples will be stored in the field, during transport and
when back at the lab? 2.3.2-3, 3.2-3.4
10. Did I decide on the material and equipment to be used? Table 1, Appendix 2
11. Did I decide on a labelling code? 1.4.2
12. Did I decide on all other practicalities for the field work? 1.4.2
Checklist fieldwork
1. Do I have all required material and equipment for the amount of samples that
I want to sample? Appendix 2
2. Do I know how to label or is all material pre-labelled? 1.4.2
3. Do I have what is needed to identify the tree species of interest in the field?
At the field site:
4. Start recording the field trip in your notebook/on your template form 2.2,
Appendix 3
5. Collect site information 2.2
6. Collect herbarium material and leaf samples 2.3.2
7. Collect wood samples 2.3.3
8. Collect and record all tree info 2.2
At the field station/camping area:
1. Dry wood cores/samples and change humid silica for fresh one 3.2
2. Assemble herbarium specimens if not done yet, change humid newspapers for
dry ones or add alcohol if drying the herbarium material later 3.2
3. Check, complete and organise field notes where needed, digitise if already
possible 3.1
1. Preparatory work
1.1 Code of Conduct
The first principle that has to be considered is the sovereign rights of states over their
forest resources. Collection, transport, processing, management and storage of
material from forest trees have to be performed in accordance with the national and
local regulations (ask for information from
your local partner(s), forester,
concession/land owner, park authorities). In addition, the sampling campaign should
be in line with the existing regional regulations such as the EUTR, the US Lacey Act
and the Australia Illegal Logging Prohibition Act (see
here for more information)
and with international regulations such as CITES and the Nagoya protocol (an
explanatory guide can be found here). For information about the requirements
concerning CITES listed species you can contact national CITES authorities.
Accordingly, research permits for field collection, Material Transfer Agreements or
other appropriate documentation must be requested well in advance to ensure the
correct collection, transport and management of the forest tree material harvested
and stored as reference samples. In addition, the community/ies living in the area
of sampling need to be informed on the sampling campaign (as some might for
example be worried the bore holes will damage the trees).
1.2 Budget
Sampling costs are often underestimated. Before planning your sampling campaign
contact the GTTN network and the GTTN followers via the ResearchGate project page
to find out if you can team up with others interested in sampling in the region to
make the trip more cost-efficient. It is advisable to account for the following expenses
when budgeting:
Any fees related to getting permission and support from both national and
local authorities for the planned sampling and for transportation of the
samples from the field to the lab.
Transportation to the different sampling sites: costs will be related to
accessibility. Inform yourself on the means and duration of transportation
required to reach the different sampling sites and the related costs (vehicle,
driver, fuel costs).
Transportation and/or shipping of the samples to the laboratory, including
potentially required phytosanitary certificates.
Payment for assistance by people knowing (i) the area and (ii) the tree
species during the entire journey to and in the forest. Consider sampling
efficiencies as low as 10 trees per day for tree species with low densities.
Accommodation and subsistence.
Sampling material and equipment (see Appendix 2).
TIP: If you will need a car and you have the choice, pick one with a functioning
cigarette lighter (accessory power outlet). This will enable you to charge batteries (for
GPS, electric increment borer, laser meter, camera, computer) in the car when needed.
TIP: To be able to estimate the sampling work that can be done in one day if
samples are taken as described in
Collecting samples
, it is advisable to do field
tests with the sampling team. The duration of a sampling campaign will depend on
variables such as: species density, available equipment (
mechanical or hand
borer), time needed to get to the canopy (to collect leaves), chosen intensity of
herbarium specimen collection, number of timber identification methods material is
collected for, experience of the field team.
1.3 Local support
1.3.1 Find a local partner institute
TIP: It is recommended to include local partners from the project design onwards to
make sure that the project interests both sides and the local partner does not just
serve as a collector.
Identification of local partners (universities, research institutes, NGOs, companies, …)
which already have expertise and/or interest in timber identification techniques
and/or have some infrastructure, material and trained personnel.
The local partner will be able to advise on a local botanist/(para)taxonomist, an
experienced driver and a field guide, who know the area and its species as well as
its dangers. They are an indispensable part of the field team as guides in the forest to
find the targeted trees, facilitate interaction with local communities and to reduce the
risk of attacks from animals or hostile people (
illegal loggers, miners).
Get advice from your local partner on how to get the required permit(s) to collect
and export samples and who should be contacted before arriving at the different
sites you want to sample (
community leaders, officials, company personnel).
Check if some physical samples can be stored in a local herbarium (see Index
Herbariorum) and/or xylarium (see Index Xylariorum) and taxonomically identified by
specialists (start with checking the GTTN network to find contacts).
Identify local students who are working or might work on the species of interest and
might be interested in co-authoring the research papers and/or to participate in the
1.3.2 Set up a local sampling team
Create a base of trust both with the local community and within the sampling team
before starting the sampling campaign and make sure everyone knows the role and
responsibility of each other. In case the principal investigator cannot participate for
the full length of the sampling campaign, his/her presence at the start of the
sampling is necessary to train the people who will do the sampling and adapt the
sampling protocol if necessary.
Use the local knowledge on species identity, variability, density and sites of
occurrence provided by botanists, ecologists, local guides and collaborators.
At least one person should be scientifically trained and understand the
reasoning behind the sampling design and be responsible for oversight of the
sample collection accordingly, for note taking and for correct GPS reading.
At least one person should be technically trained and responsible for sample
collection according to protocol and maintenance of equipment.
Depending on the conditions additional expertise might be necessary: a
person that can use a gun, a driver used to the terrain that will be sampled, a
tree climber, a person trained in using a sling shot.
1.4 Sampling design
1.4.1 Scientific set-up
To be able to set-up the sampling design a scientific literature review and general
information search should be undertaken to collect as much information as possible
on the species and geographic locations of interest. The thoroughness of the review
on the geographic location(s) will depend on the goal of the sampling, species or
origin identification and the required resolution of the origin identification. Table 1
gives an overview of the reference material that needs to be collected to allow
species or origin identification using the different tracking methods.
Information that should be collected (where applicable for the specific wood
identification goal of the sampling):
To decide on where to go sampling (which countries and locations)
samples already available (check GTTN’s reference database)
species distribution (focus on natural occurrence not on political borders)
intraspecific species diversity (genetic variation, which might also influence
anatomical and chemical properties)
species abundance (a minimum of 20 individual trees per species of interest
should be available for sampling in an area of 1 km²
spatial distribution of species in forest concession (forest inventory map)
environmental variation (include as much as possible)
chance of getting a permit to sample at the sites of interest
accessibility and feasibility (infrastructure)
safety (political situation, terrain)
relevance for the timber trade (areas where legal and/or illegal harvesting is
currently happening, or where it is projected to happen)
risk of endangering the species population
possibility to partner with a concession holder and to sample during or
shortly after logging (within one week at most and with trees still lying at
the felling site, to guarantee fresh wood and leaves and the leaves’ origin)
To decide on when to go sampling, balancing the ease to identify species
(flowers or fruits available), the ease to do field work (dry season) and
minimising tree injury by coring (faster compartmentalisation of the wound in
the growing season
species phenology (months of leaf flushing, flowering, fruiting)
climatic conditions (see §1.4.2 practical set-up)
To decide on what to sample
taxonomically closely-related species or cryptic species
trunk diameter found in trade and diameter at which the species starts
forming heartwood in the location of interest
To anticipate potential identification issues
potential association with rhizobia (can influence isotope profile)
seed/tree source of species in the forest concession
For heavily harvested species where this might be impossible, select sites with the highest
tree density available.
et al.
Grissino-Mayer (2003), Tsen
et al.
Table 1. Overview of the essential and ideal amount of reference material that needs to be collected for species or geographic origin determination of wood
via the currently available techniques.
Design questions
Wood anatomy
Multi-element stable isotopes
For all questions
general requirements
Sample all material (leaves, wood) from mature trees (DBH larger than 20 cm), at breast height or 30 cm above buttressesI, where no stains or
damage from bacteria, fungi or insects are visible and from trees growing in as varied environments as possible (soil type, altitude, exposure,
fresh water access, …). Assure an even distribution of the number of individuals among sampling sites, with a preference for more sampling sites
with fewer trees per location.
type of material
Sap- and/or
Leaves, needles, buds and/or cambium
Sap- or heartwood or both
amount of material per
Block of 1 cm³ or a
20 mm diameter
core or (ideal) 1 x
7 x 11 cm wood
10 cm² of leaves/needles/buds or 3 cm
diameter punch of cambium layer or (but
less ideal) 1 cm³ of sapwood
Min. 8 growth years or ca. 10
cm of a 5 mm diameter core (5
g of wood in shavings)
A small core (3-5
slivers, 10-20
optimal, with a sliver
being of fingernail
size is enough)
BlocksIV of min. 2 cm²
in tangential or radial
longitudinal direction
1 per treeVI
3 per tree
3 per tree
1 per tree
3 per tree
preferred equipment
Increment borer,
chisel and
hammer, saw
Telescopic scissors or sharpened hook,
sling shot, puncher and mallet
Increment borerVII (manual or mechanical)
For species identification
botanical material
1 herbarium specimen (branch with leaves, fruits and/or flowers and optional a piece of bark) per tree
nr. of trees & sites
5 trees or 5 trees
per site if
50 trees over the whole species range
not possible with this method
15 trees
20 trees
outgroup (ideal)
At least 5 trees should be collected from each species that could be confused with the species of interest (same genus).
nr. of trees & sites
20 trees over the
whole species
range (for
machine vision)
10 trees per sampling site with a total
min. of 50 if covering the whole species
range. More sampling sites are better
than more trees per site.
not possible with this method
20 trees
30 trees
Table 1. (continued)
Design questions
Wood anatomy
Multi-element stable isotopes
For origin tracking to a region or country
botanical material
Pictures of trunk, leaves, and if possible fruits and/or flowers per tree and 1 herbarium specimen per siteVIII. If one tree is difficult to identify,
then a herbarium specimen should be taken.
nr. of trees & sites
not possible with
this method
20 trees per sampling site
5 trees per sampling site
50 treesIX in total for
1 region/country
50 treesIX in total for
1 region/country
nr. of trees & sites
30 treesX (at least 200 m apartXI) per
sampling site (at least 100 km apart) with
a total of 1000 trees and sites covering
the entire species range and all different
environmental conditions
Each time 10 trees per
sampling site and sampling
sites covering entire species
100 trees, sampling
sites covering entire
species range
100 trees, sampling
sites covering entire
species range
For origin tracking to a concession
botanical material
Pictures of trunk, leaves, and if possible fruits and/or flowers per tree and 1 herbarium specimen per siteXII.
nr. of trees & sites
not possible with
this method
Per focus concession 200 trees at least 50
m apartXI (5 x 40 trees in the annual
logging plot and 4 other well-distributed
areas) and from each neighbouring
concession 50 trees (can be along a
50 trees per concession and
from each neighbouring
concession 25 trees
50 treesIX
50 treesIX
nr. of trees & sites
Sample size depends on concession size
and distance to neighbour concessions
Depending on the climatic or
environmental variations in a
sample site
100 trees
100 trees
For origin tracking to an individual tree
botanical material
1 herbarium specimen (branch with leaves, fruits and/or flowers) per treeXIII
nr. of trees & sites
not possible with
this method
all trees which should be felled according
to management plan
not possible with this method
not possible with this
not possible with this
Wood characteristics change from roots to canopy and it is hence advisable to standardise the height of sample collection. Also near buttresses (and any other imperfections)
wood characteristics are deviant.
Heartwood in slivers, blocks, or sawdust is required for chemical analysis by DART TOFMS and NIRS. Heartwood has a higher content of extractives than sapwood which
allows easier discrimination between species. In addition, sapwood contains sugars that confuse the spectra for identification. Different species of trees have varying degrees
of depth at which heartwood forms so care should be taken to clearly identify and collect the heartwood.
Only possible from already felled trees.
Also powder of 4 mm granulometry can be used to obtain a NIRS spectrum. Only on wood pieces, however, can the method be used in the field. Besides, during the milling
process special care should be taken to not affect the chemical components in the wood.
Replicates might be needed to collect enough material and to account for intra-tree variation.
For machine vision it is however useful to sample from different positions in the tree to include as much intra-tree and intra-specific variation as possible (but while sampling
only mature wood).
Advice and tips for using an increment borer can be found in Grissino-Mayer (2003) and examples of mechanical borers are described at
(Kagawa and Fujiwara, 2018) and in Krottenthaler
et al.
Ideally, each reference sample should be connected to a herbarium specimen (preferably branch with leaves, flowers and/or fruits) deposited in a public herbarium.
However, this is not always possible (
when sampling 1000 trees for provenance determination).
Origin tracking with DART and NIRS is currently under development. The required number of trees might thus lower in future.
Double the number of individuals if congeneric species may confound species identification.
This condition is lifted when tree density is too low to otherwise reach the minimum sample size.
Also in concessions misidentifications can happen.
Even here herbarium specimens are essential because (1) many journals won’t accept wood identification papers that don’t reference herbarium specimens and (2) when
the material would ever be used in a court case, the absence of herbarium specimens would harm the case.
1.4.2 Practical set-up
Take the necessary personal precautions. Get an update on the latest political
situation at the sampling sites and check if specific health precautions should be
required vaccinations.
Check the climatic conditions of the region to identify an appropriate sampling
period. In tropical areas avoid rainy seasons and in mountainous/continental regions
avoid cold months, as strong rain or heavy snowfall may reduce or impair the
accessibility of sampling sites and thus increase the costs of sampling.
Decide on the means of transport to the different sampling sites (plane, boat,
4x4/car, taxi, bike, canoe, by foot or combination) and make the necessary
Decide on the sampling material and equipment (see Table 1 and Appendix 2) and
prepare. Provide also a spare set as replacement may not be possible at local
Decide on the amount of material you will collect (see Table 1 for the essential and
ideal amounts). Consider informing the GTTN members via the website or the
ResearchGate project page as there might be interest in joining forces and hence to
sample more material that can then benefit more researchers at once. At least 1
herbarium specimen is needed per tree or site (see Table 1) but preferably duplicates
are collected to be sent to other herbaria along with duplicate wood specimens in
order to safeguard the collection material.
Set up a robust and consistent labelling strategy. All reference material (wood,
cambium, bark, leaf, flower, fruit) collected from the same tree should be labelled
with the date of collection and the same, unique sample code that should reference
back to a sample record identifying at least:
the location
the species
the tree
the position around the tree’s circumference
the radial position in the tree where the sample was taken
Check regulations on import of wood and botanical material.
It is important to notice that the species can only be confirmed after accurate identification
(by a specialized taxonomist). The intended species to be collected in the field is, therefore,
not necessarily the actually collected species. The final ID might hence differ from the field ID.
Decide on the wood collection and herbarium you will use to store your wood
samples and herbarium specimens (check the Index Xylariorum and the Index
Herbariorum). Preferably, send your herbarium specimen and wood sample to the
same institute since it is not desirable that these two specimens are separated from
each other. If not possible, make sure the two institutions have the associated sample
TIP: To save work in the field (where conditions might also be less favourable to be
writing), sets of pre-labelled bags/vials can be prepared beforehand with different
sets per tree, per site, per species, … that can be grouped in a bigger bag or
container, or strung along a small cord. In this way, it also immediately becomes clear
when you forget to take a sample as then one bag will stay empty. Make sure to label
with water resistant and alcohol resistant marker pens.
TIP: Avoid editing the unique sample code of the samples. If you decide to do so,
remember to apply the change to all collected material (herbarium specimen, leaves,
cambium, wood, ).
2. Field work
2.1 Species identification in the field
Correct species identification is essential when collecting wood samples for a
reference database (to identify species or geographical origin of wooden material) as
mentioned in the UNODC guide (UNODC 2016):
Accurate taxonomy is critical. Reference material should be collected by (or in
collaboration with) experts on field identification of the taxa in question. Where
possible, trees already taxonomically verified
[by having collected an herbarium
specimen so that the taxonomic identity of the wood sample can be verified by other
can be utilized, such as those that are part of permanent study plots or
botanic gardens (although use of botanical garden specimens should be considered
carefully as misidentifications can occur, and should be avoided altogether for
anatomical or provenance research where the garden is outside of the taxon’s natural
range). When collecting from standing trees that have not yet been taxonomically
identified, herbarium voucher
specimens should be collected to allow post-hoc
confirmation of identity by herbarium taxonomists
[How to collect herbarium
specimens is described in
It is highly advisable to engage a local botanist/(para)taxonomist who can help with
identifying the species of interest in the field. Tree species can be recognised by
tree morphology and by the characteristics of their leaves, fruits, flowers (see
consult relevant literature for time of flowering/fruiting) and bark. By cutting the bark
with a machete the wood’s colour and smell can also assist in identification. A printed
picture of a herbarium specimen of the species could be taken along in the field.
In the case that it is not possible to identify the tree with 100 % certainty in the field,
it is still worth to take the sample along together with a herbarium specimen (make
one for at least one sample per species and per site) and a note of the uncertainty of
the identification in the sample record. The herbarium specimen can be examined at
the herbarium and in many cases assigned to the correct species.
Where it is impractical to collect vouchers for all individuals (e.g. where foliage is
high in a dense canopy or when deciduous trees are bare), identification should be
confirmed through other means by checking that samples cluster with taxonomically
A herbarium specimen is sometimes called a voucher.
verified individuals, such as through various genetic or chemical profiling approaches
(UNODC 2016).
2.2 The sample record: collecting tree & site information
For each tree sampled, information on the tree and the site should be collected to
make the sample suitable for species and/or origin identification. This is especially
important if the samples will be shared with other researchers, will be analysed via
different timber identification methods or if there were unexpected changes to the
sampling plan. In addition, this information is needed to prepare the herbarium
specimen label. Below you can find a list of all data that are recommended to be
recorded in a notebook or on a template, which can be developed for convenience in
the field (For examples see Appendix 3).
For each sampling campaign:
Collection season (this can influence fruit/flower size and hence species
Names of the members of the sampling team
For each sampling site:
Collection locality:
Political divisions (
country, province, region, district, commune, locality)
Concession (if applicable)
Habitat description (
forest type, altitude, list of other characteristic taxa,
other site characteristics)
Climatic zone
Name of collector
Name (if different from collector) and species identification qualifications of
the person who identified the species
Tree characteristics used to identify each species
For each tree sampled:
Collection date
GPS coordinates as latitude and longitude (in decimal degrees with at least
four decimals) and using WGS84 as datum
Unique labelling codes of all
samples taken (see
This applies to all types of tree material (leaves, bark, cambium, wood).
Scientific species name, or if not possible the local species name, and a note if
identification is uncertain
Specimen description (attributes which cannot be observed from the samples
Tree circumference or diameter at breast height (cm)
Tree height (m) (estimation using clinometer and laser meter/tape measure
or a hypsometer)
Position in the canopy (
lower, middle, upper)
Samples taken from a standing or recently felled tree (and inventory
number if sampled from a concession)
What other material was collected (note down which tissue types were
sampled for each tree)
Photos (advisable) with an object of known size (
ruler, pen, coin) as scale
bar and with the individual sample ID to later verify species identity and to
help your memory in case any peculiarities pop-up of:
Tree in its environment
General shape of the tree (incl. any buttress roots)
Tree with extraction site visible
Bark and other distinctive elements (close-ups of flowers, fruits, leaves)
Collected material when still fresh (leaves, fruits, flowers, wood)
GPS device with coordinates showing and sampled tree in background, or
use a sampling app that records the current location when you take the
photo of the tree
TIP: It is advised to tag each sampled tree with the unique sample code (
Fig. 1a).
It can help prevent sampling the same tree twice and would allow repeat visitation of
that tree (GPS coordinates are not always exact enough to get to an individual tree
TIP: If you have a smart phone in the field, instead of or in addition to taking GPS
coordinates, you can also use a GPS Logger app. Alternatively, geo-tagged photos
can be taken of the sample bag with the sample visible inside and the label visible.
Make sure that time and date are accurate on cell phone and that location tagging is
. Take your precautions to avoid running out of battery.
Be aware that location data accuracy comes down to an interplay of several factors,
including signal source (GPS signals, Wi-Fi, and cell tower triangulation), environment (area
density, skyline view, and indoor or outdoor location), and personal use (location data access
enabled, type of mobile app used, and operating system usage) [Ref.].
TIP: Combining the above two tips, a mobile phone app can be developed where
sample and site information as well as pictures can be put into a database directly in
the field and uploaded into the cloud as soon as networks are available.
2.3 Collecting samples
In Appendix 1-3, you can find (1) illustrations of the sampling procedure described
below, (2) a list of the material and equipment needed for the sampling, and (3)
examples of template field forms to record the sampling.
In Table 1, the type and amount of material, the number of trees and the number
of sites to be sampled are given. Here we describe how the material should be taken
and we give an overview of the material to be collected when sampling immediately
for different identification methods at once.
In chapter 3.2, more extensive information on sample storage is given.
Silica gel? We recommend the use of silica gel
since it is a good desiccant, is
lightweight and it has a humidity colour indication but if not possible you could use
rice husk
et al.
2017). Since it doesn’t change colour, test a range of samples
to get to know how fast you have to replace it. Put the rice husk for example in a tea
bag inside a ziplock bag with the sample to avoid contact with the desiccant.
How much silica gel is needed? As a rule of thumb a 1:10 ratio of sample to silica by
weight is advised. The silica is changed until the sample is fully dried and the silica
doesn’t change colour anymore.
What do we mean with contamination? In this guide it is regularly mentioned to
watch out for contamination. With this we mean contamination with DNA (which
would affect DNA analyses) or with chemical compounds (which would influence
stable isotopes, DART and NIRS analyses). Therefore, if you want to dry and reuse
silica gel beads, they should be put in for example tea bags closed with a piece of
thread to avoid contaminating samples. At the same time, the self-made silica bags
will facilitate exchange with bags containing fresh silica.
We recommend use of the larger (2-4 mm beads) orange/green silica gel crystals. The
indicator dye cobalt chloride used in the blue/pink ones has been classified as a carcinogen
in Europe. Methyl violet is offered as a safer alternative. The dust size gel is impossible not to
inhale when you handle it [from:].
Rice grains or salt is not recommended as their water absorption capacity is not high
enough for fast desiccation and hence to prevent DNA degradation and moulding (affecting
the chemical analyses).
2.3.1 Overview of reference material to be collected enabling species/origin
identification by all methods
Reminder: the following instructions are to fulfil the minimum requirements for the
different timber identification methods and hence to make method combinations
possible. Method-specific instructions can be found in Table 1.
Herbarium specimen: 1 branch with mature leaves, flowers and/or fruits per
tree (for species identification) or per site together with 1 set of pictures of
leaves, flowers and/or fruits per tree (for origin identification)
. For compound
leaves, make sure to sample the entire compound leaf and not just a fraction.
Material for DNA analysis: leaves or needles (or leaf buds if leaves didn’t
flush yet) with a minimum combined surface area of 10 cm². If leaves could not
be collected or as a safeguard, three 3 cm diameter punches of cambium or,
less ideal but possible, 1 cm³ of sapwood.
Material for stable isotope analysis: one but ideally three 20 cm long and 5
mm diameter (pieces of) wood cores providing 5 g of wood (for trees of very
light wood density more or longer cores might hence have to be taken).
Material for DART TOFMS and NIRS analysis: 5 cm of the innermost parts of
one but ideally three wood cores of 25 cm long and 5 mm diameter (the
required depth of coring will depend on heartwood formation in the species
and locations of interest)
Material for potential future identification methods: keep the bark of the
above mentioned punches and cores.
Material for wood anatomy: 5 mm diameter cores are not suitable as
reference material
. An extra wood sample needs to be taken at breast height
of at least 1 cm³. This will guarantee that good micro-sections can be cut along
all planes (even by less experienced wood anatomists), that there is a big
enough surface area to analyse anatomical variations, and to allow digital
image analysis.
Ideally, 2 herbarium specimens are collected so that one can remain in the herbarium and
the other can be send to a taxonomist (outside of the herbarium) if necessary. If absolutely
impossible to collect leaves, they can be looked at with binoculars to make a determination.
Only when the core goes straight to the pith, sections can be made along all planes using
the full size of the core. As test material, on the contrary, samples can be as small as a sliver
to be analysed by wood anatomy.
2.3.2 How to collect leaves, fruits and flowers > herbarium specimen and DNA
From the exact tree that will be sampled for wood (
., a mature tree): take two
branches with multiple mature leaves or at least 1 mature compound leaf (Be
sure the compound leaf contains all the leaflets and the whole rachis.). The
branch should be big enough to show the distribution of the leaves in the
branch. If available the branch should also contain flowers and/or fruits. Don’t
collect already fallen leaves from the ground, or from a nearby sapling.
Put one of the branches showing at least front and back side of a leaf and if
available a flower or fruit between newspapers in a botanical press for the
herbarium specimen. This step can also be delayed to the end of the day when
back at the field station. Label branches in the field (
with paper tags) and
transport them in big plastic bags to the field station. Press and dry samples as
soon as possible. When the climate is humid and when staying in the field for
more than two days, preserve the herbarium specimens in a plastic bag wetted
with 50 % alcohol (and dry in an oven later) (Fig. 3e-f).
When dealing with large fruits or fleshy flowers put them in teabags inside
ziplock bags with a silica gel bag.
The leaves of this second twig are stored for DNA analysis in a tea bag that is
put inside a ziplock bag together with a silica gel bag. This is to avoid losing
the leaf material as it may break into small pieces.
Make sure all material collected is labelled.
TIP: More information on collecting and preparing high quality botanical specimens
is available from Missouri Botanical Garden (Liesner, accessed 24 April 2018) or Royal
Botanic Gardens Kew (Jennings
et al.
TIP: If collection of botanical samples is not possible, take a photo that shows the
tree characteristics. Include a ruler or a scale bar to give an idea of the size of leaves,
fruits or flowers. Never collect leaves from young trees or sprouts as morphological
characteristics may differ to those expressed in adult trees.
TIP: To fasten desiccation, the leaves taken for later DNA analysis (not the ones for
the herbarium!) can be ruptured into small pieces using clean scissors (clean with
alcohol for each tree). The pieces are then put in tea filters in the ziplock bags with a
silica gel bag.
2.3.3 How to collect wood samples > all timber identification methods
From standing trees
From the same tree as you just sampled leaves, fruits and/or flowers:
At breast height, take at least one but ideally three (see Table 1) 25 cm long 5
mm diameter wood cores per tree at different positions around the stem’s
circumference. Clean the increment borer and extractor with ethanol (50-70 %)
each time before sampling a new tree. When the species has a very hard outer
bark, remove
only this very outermost, hard part of the bark to facilitate
coring but keep the rest of the bark (for potential future research). Store the
cores in paper straws ( storage essentials for DART analysis
) for transport
indicating orientation (pith/bark side) and closing both sides of the straws by
turning. Once back at the field station/camping area dry the wood inside the
paper straws by keeping them 20-30 cm above a small fire (Fig. 5d).
Alternatively, plastic straws can be used, which can be closed using a lighter.
However, special care should then be taken to prevent mould. At the end of
the day, cores should be taken immediately out of the straws for air drying in a
place with a good air flow
. Once dry and if already convenient at the field
station/camping area, break (don’t cut to avoid contamination) the core in the
following pieces and store them in separate paper bags, each labelled
differently to be able to identify the pieces as originating from different parts
of the stem.
b. FOR STABLE ISOTOPES: Outermost 20 cm of the core
c. FOR DART TOFMS AND NIRS: Innermost 5 cm of the core
If inconvenient, wait to break the cores until back at the lab and if cores were
taken out of the straws for drying, put them back in for transport to the lab.
FOR WOOD ANATOMY: Some 20 cm above or below the height where you took
the cores (to avoid damaging the tree too much), take a wood sample of at
least 1 cm³ with punch and mallet, chisel and hammer, a saw (cutting a small
wedge) or with an increment borer (Fig. 5h). Store samples in small vials with
50-70 % ethanol (essential for tree species with included phloem) or air dry.
When bark has deep furrows, it is sometimes also possible to just begin coring between
Attention is needed when storing cores for DART analysis. More information can be found in
chapter 3.2.
In case you are lucky and have access to a field station that is even equipped with an oven,
you can also dry the straws at 65 °C.
breast height (to avoid damaging the tree too much and as DNA anyway does
not change within the tree, in contrast to the other wood characteristics),
hammer with a 3 cm diameter punch (Fig. 4c) just 1 cm deeper than the bark
(punch the first time rather deep to get to know bark thickness). Take the
sample which will contain bark and cambium. If thicker than a few millimetres,
separate with a knife the outer layer of bark from the cambium (to speed up
desiccation of the cambium
) (Fig. 4d). Store both, bark and cambium samples
in separate tea bags in a ziplock bag together with a silica gel bag.
TIP: In addition to labelling on the outside of vials, small paper tags with pencil
marks can be put inside the vials. Marker pen labels might accidentally get rubbed off
by the ethanol (not all ‘permanent’ markers are permanent).
TIP: To date there is no evidence for the long term benefit of using any wound
treatment after coring (Grissino-Mayer 2003, Tsen
et al.
2016). If you are in for an
extra research project, you could thus plan more time for the sampling campaign and
in one go collect data to study taxa and environmental characteristics that could
explain sensitivity to deleterious damage after coring. Tsen
et al.
(2016) have already
developed a proforma to quantify and standardise such an assessment.
TIP: Use a single, simple lubricant that won’t interfere with DART chemical analysis for
the increment borer.
From already felled trees
In cases where freshly-felled trees, with still fresh leaves and still lying at the felling
site, can be sampled, do not attempt to core. Instead, collect leaves and cambium
material from the tree stump (Fig. 4f) [for DNA analysis] and a wood piece of min. 1
cm³ and ideally 1 x 7 x 11 cm including both sapwood and heartwood from the tree
stump [for wood anatomy]. Two other big samples are taken, one sample of 10 cm in
radial length, 1 cm thickness and 5 cm wide [for stable isotopes] and one sample of
10 cm³ of only heartwood [for DART TOFMS, NIRS]. For small trees an entire 2 cm
thick disc could be cut. Air-dry samples.
To improve the amount and quality of DNA that can afterwards be recovered from the
3. Transport &
Storage of samples and data
3.1 Forest-to-lab sample chain & sample quality
Tips to mitigate the risk for a reduced sample quality due to a long path, with many
handling steps of the samples from forest to lab:
Data from the sampling campaign (notebook data and/or completed sample
record templates, GPS coordinates, photos, ...) need to be digitized and well
organised as soon as possible and cross-checked with the samples.
The above should ideally be done by the field team itself (hand writing might
be difficult to read)
GPS coordinates should be checked with online services such as Google Earth.
Contact information from the field team should be available to answer any
question during sample processing in the laboratory.
3.2 Sample storage in the field
Correct sample storage is a critical step to avoid damage or staining caused by
bacteria, fungi or insects, which would make the samples useless. Fungal infection of
the samples is a considerable problem, especially in tropical countries, so correctly
storing the sample in the field is essential during the collection trip. Stains hinder
wood anatomical identification and micro-organisms influence the genetic and
chemical characteristics of the wood. Also the storage material can influence the
chemical characteristics of the wood. Therefore, special care needs to be taken when
sampling for DART analysis (see Box 2).
Storage advice for the various materials collected
The herbarium specimens should be checked regularly and the newspapers
exchanged with dry ones when damp to prevent the growth of mould
. In the
tropics, when staying longer than two days in the field, herbarium material is
best preserved by putting the specimens in a plastic bag wetted
with 50 %
alcohol. Back in the lab the herbarium specimens can then be dried in an oven.
Full length cores are stored in paper straws and dried by keeping them 20-30
cm above a small fire (Fig. 5d) or in an oven at 65 °C (if you have access to
one). If none of the above is possible they should be taken out of the straws
and air dried. If cores are stored in plastic straws or small diameter pvc tubes,
they certainly must be taken out immediately when back in the field
station/lodging area to leave the cores air drying to prevent them from
moulding. Cores can be soaked in sodium hypochlorite before putting in the
straws to delay fungi formation. Plastic straws can also be cut open lengthwise
to leave the moisture out. Alternatively, cores can already be broken in their
pieces at the field station and then stored in tea bags inside ziplock bags with
silica gel.
Samples for NIRS should not come into contact with any chemical product
glue at the sticky side of tape).
Leaves and cambium samples for genetic analyses should be stored in
ziplock bags or small tubes with silica gel, or in tea bags inside ziplock bags
and/or inside airtight plastic containers with a silica gel bag.
The wood samples for wood anatomical analysis and the extra set of
flowers and/or fruits (next to the ones attached to the herbarium specimen
that is stored between newspapers in a botanical press) are stored in ziplock
bags with silica, or in vials with 70 % ethanol, or air dried and stored in paper
bags. However, for species with interxylary phloem only storage in 70 %
ethanol will prevent phloem cells from collapsing.
For the same reason bark should be preserved in 70 % ethanol.
A field dryer can be built at low cost that can speed up the drying process if there is enough
sunlight (Sinnott 1983).
Add enough alcohol to prevent the growth of mould but be careful to not add too much
alcohol, which could damage the newspaper and the sample.
General storage instructions
To avoid the risk of unidentified bags lying around, it is good practice to
label the bag and to put a paper label written in pencil inside the bag. This will
also prevent labels from disappearing due to rain or leaking ethanol.
All samples stored with silica gel should be checked regularly. Ideally the silica
gel is checked in the evening after collection and the latest after 24 h and
replaced when it has changed colour with new, clean silica (for recycled silica,
see Box 1). Check the bags every 24 h for evidence of changing colour in the
silica. If it has changed, the silica is replaced. Keep checking bags until no
further change in silica colour is observed.
If it is impossible to stick to the recommended ratio of 1:10 when using
silica gel, it is better to air dry samples (although not recommended for
cambium) as samples will mould inside the ziplock bags.
All ziplock bags should be kept in a hermetic plastic box and/or in a dry area
(air conditioning) since ziplock bags are not air-tight.
There is a potential issue of paper bags or paper straws for storing wood samples
for DART analysis, as the paper can strongly influence the chemical signature of the
wood. However, for dense and/or dark wood this is less of a problem. The denser the
wood, the less likely it is to absorb the volatile molecules from the paper. The darker
the wood, the more likely it is that the inherent richness of small molecules in the
wood overwhelms the paper chemical signature.
The general recommendation is therefore to use paper straws and/or bags of a
single defined source. In addition, a few straws/bags should be kept apart so that
the storage material as such can be analysed.
Alternatively, samples can be stored in something that is more chemically inert (
plastic, aluminium,…). However, special care should be taken to dry samples as fast as
possible to prevent mould growth, which will influence the chemical signature
without doubt.
Little research has been done so far in this respect, some prior investigation is hence
recommended. The chemical signal of the storage material might disappear when
samples are left to the air for some time before doing the DART analysis. Dissecting
the sample so that the sliver used for analysis excludes wood that has been in
physical contact with the storage material may work as well.
3.3 Sample transport
Check the phytosanitary rules of the country of import if you are exporting
samples out of the country.
Choose reliable companies to transport the samples and do not forget to
provide the research and export permits for transportation.
If there are samples stored in ethanol and if this would cause a problem for
transport, empty the vials for the transport and refill them with ethanol as
soon as they arrived at destination.
3.4 Long term sample storage
Deposit the herbarium specimens in a herbarium.
Store duplicate wood material in a xylarium, with the associated herbarium
specimens to assist taxonomic identification (xylarium and herbarium
preferably in the same institute).
At arrival in the laboratory all samples should be further dried if necessary and
stored in a cool, dry place (18-22 °C; 45-55 % RH) or in the freezer at -20 °C.
Special care should be taken on sample labelling on the storage boxes and to
the maintenance of documentation and databases.
If possible, the local partners should keep a duplicate of each sample in case
something goes wrong during shipping. In general, it is advisable to keep
backup samples in several different laboratories and repositories.
TIP: For NIRS, storing wood samples at 20 °C and 65 % RH would be ideal but is not
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Tsen, E. W. J., T. Sitzia and B. L. Webber (2016). "To core, or not to core: the impact of
coring on tree health and a best-practice framework for collecting
dendrochronological information from living trees." Biological Reviews 91(4): 899-
UNODC (2016). Best Practice Guide for Forensic Timber Identification. New York,
United Nations.
Vlam, M., G. A. de Groot, A. Boom, P. Copini, I. Laros, K. Veldhuijzen, D. Zakamdi and
P. A. Zuidema (2018). "Developing forensic tools for an African timber: Regional
origin is revealed by genetic characteristics, but not by isotopic signature."
Biological Conservation 220: 262-271.
The icons used in the quick guide were designed by Freepik from
5. Appendices
Appendix 1: Illustrations to the sampling guide
Fig. 1 - Sampling material
a. Tags to mark sampled trees (codes are scratched onto the metal and written over
in pen), b. ziplock bags to store samples with silica gel, c. air-tight container to store
ziplock sample bags, d. colour indicating silica gel beads, e. tea bags to fill with silica
gel and to store several samples, separately in one ziplock bag, f. paper bags to store
air-dried wood samples, g. plastic pvc tubes with corks to seal ends and plastic straws
to store cores, h. herbarium press, i. herbarium material stored in newspapers inside
a plastic bag with alcohol during fieldwork (when drying and pressing can not be
done in the field).
Fig. 2 - Sampling equipment
a. GPS unit (
), b. examples of a clinometer (
), altimeter (
) and
hypsometer (
) to measure tree height, c. punch and hammer to take cambium
samples, d. increment borer and extractor to take wood samples, e. equipment to go
with wood borer (napkins, dowel, light oil for cleaning, a protective pouch made of
bubble wrap and tape, a cardboard tube for storage). To take herbarium material and
leaf samples: f. telescopic scissors and normal scissors, g. telescopic sharpened hook,
h. sling shot, i. tree climber gear.
Fig. 3 - Collection and storage of herbarium material
a-b. Photographic records of individual trees, c. branch sample for herbarium
specimen, d. field botanist making herbarium specimens at the end of the day (at the
research station camp), e-f. field botanist packing up completed herbarium
specimens and wetting them with alcohol for preservation and protection during the
remainder of the field work, g. herbarium material can directly be dried and pressed
when conditions allow, h. final herbarium specimens.
Fig. 4 - Sampling and field storage of leaf and cambium material
a-b. Leaves stored in ziplock bag with silica gel for DNA analysis, c-d. sampling
cambium material with punch and mallet for DNA extraction, e. tree after cambium
samples have been taken with cambium samples in ziplock bag with silica gel, f.
sampling cambium material from a freshly felled tree.
Fig. 5- Sampling and field storage of wood material
a. Collecting a 5 mm diameter wood core with a manual increment borer, b. storing
core in a straw for transport in the field, c. cores stored in plastic straws cut open
lengthwise to let the moisture out, d. cores stored in paper straws drying above a fire,
e-f. removing a stuck increment borer from a tree using a rope: by rotating the borer
the tension in the rope increases pulling the borer out, x collecting a 20 mm core
with a mechanical increment borer, g. piece of a core stored in a paper bag, h.
collecting a 20 mm diameter wood core with a mechanical increment borer, i. short
20 mm cores for wood anatomy that will be stored in paper bags for air drying.
Appendix 2: Sampling material & equipment
Sampling material
Tags to mark sampled trees
Permanent marker pens (alcohol and water resistant), pencils, labels,
weatherproof notebooks
Ziplock bags in different sizes
Plastic containers to store ziplock bags
Silica gel or rice husk
Tea filters and/or paper bags in different sizes
Paper straws, plastic pvc tubes or core holders
Sodium hypochlorite
Herbarium press, old newspapers, plastic bag, adhesive tape
50-70 % ethanol (to store samples and to clean material), vials
Sampling equipment
GPS, cell phone (with GPS Logger app)
Clinometer and laser meter/measuring tape (or hypsometer)
Binoculars, camera
Puncher, hammer
Increment borer
, napkins, dowel, light oil for cleaning, protective pouch
Machete, saw, pruning shears
Telescopic scissors, normal scissors
, slingshot, (tree climbing gear)
Spare batteries, battery chargers (for GPS, phone, laser meter)
Personal supplies
Food, water
First aid kit
Mosquito repellent
Check endnote VII to Table 1 for more information on increment borers.
Can be made of bubble wrap and tape, with a cardboard tube for storage (Fig. 2e).
To cut branches to the required size for a herbarium specimen.
Appendix 3: Examples of forms to collect field data
Field data collection form used in: Paredes Villanueva, K. (2018) “Tropical timber forensics: A
multi-methods approach to tracing Bolivian Cedrela”, PhD thesis, Wageningen University,
the Netherlands.
# Tree
Crown position
Crown shape
(1 - 5)
(1 - 5)
(1 - 4)
Crown position:
1. Emerging
2. Full top lighting
3. Some top lighting
4. Some lateral light
5. Absence of light
Crown shape:
1. Perfect: Complete circle
2. Good: Irregular crown
3. Tolerable: Half crown
4. Poor: Less than half crown
5. Very poor: one or few branches
Lianas infestation:
1. Free of lianas
2. Lianas present in the trunk
3. (Slight) presence of lianas in the trunk and crown
4. Presence of lianas in the trunk and crown (it affects tree grow)
Field data collection form used in: Honorio Coronado, E., Blanc-Jolivet, C., Mader, M., García-Dávila, C., Sebbenn, A. M., Meyer-Sand, B. R., Paredes-Villanueva, K.,
Tysklind, N., Troispoux, V., Masso, M. & Degen, B. (2019). Development of nuclear and plastid SNP markers for genetic studies of
tree species in
Conservation Genetics Resources
, 1-4
GPS model:
Sample type
precision (m)
Photo #
The objective of the Global Timber Tracking Network (GTTN) is to promote the
operationalization of innovative tools for wood identification and origin
determination, to assist the fight against illegal logging and related trade
around the globe. GTTN is an open alliance that cooperates along a joint vision
and the network activities are financed through an open multi-donor approach.
GTTN phase 2 coordination (2017-2019) is financed by the German Federal
Ministry of Food and Agriculture (BMEL).
Full-text available
Various problems worldwide are caused by illegal production and distribution of timber, such as deception about timber species and origin and illegal logging. Numerous studies on wood tracking are being conducted around the world to demonstrate the legitimacy of timber. Tree species identification is the most basic element of wood tracking research because the quality of wood varies greatly from species to species and is consistent with the botanical origin of commercially distributed wood. Although many recent studies have combined machine learning-based classification methods with various analytical methods to identify tree species, it is unclear which classification model is most effective. The purpose of this work is to examine and compare the performance of three supervised machine learning classification models, support vector machine (SVM), random forest (RF), and artificial neural network (ANN), in identifying five conifer species and propose an optimal model. Using direct analysis in real-time ionization combined with time-of-flight mass spectrometry (DART-TOF-MS), metabolic fingerprints of 250 individual specimens representing five species were collected three times. When the machine learning models were applied to classify the wood species, ANN outperformed SVM and RF. All three models showed 100% prediction accuracy for genus classification. For species classification, the ANN model had the highest prediction accuracy of 98.22%. The RF model had an accuracy of 94.22%, and the SVM had the lowest accuracy of 92.89%. These findings demonstrate the practicality of authenticating wood species by combining DART-TOF-MS with machine learning, and they indicate that ANN is the best model for wood species identification.
Full-text available
With increasing concerns about sustainable exploitation of tropical timber, there is a need for developing independent tools to check their origin. We evaluated the potential of tree-ring stable isotopes for identifying four Cedrela species (C. balansae, C. fissilis, C. odorata, and C. saltensis) and for identifying geographic origin of C. fissilis and C. odorata, two of the most intensively exploited species. We studied differences in 13C and 18O of wood among 11 forest sites (163 trees). We quantified isotope composition of 10-year bulk samples, and for a subset we also evaluated isotopic annual fluctuations for the last 10 years. Although annual isotopic variability was not correlated to precipitation or elevation, we found a significant relationship between the 10-year bulk stable-isotope composition and average precipitation and elevation. However these relationships were not consistent across all sites. We also explored isotopic site and species differentiation using Kernel Discriminant Analyses. Site discrimination was low: 30% accuracy for C. odorata, and 40% for C. fissilis sites. However, species discrimination was 57.5% for C. odorata and 95.3% for C. fissilis. These results suggest that although 13C and 18O isotopic analyses hold potential to verify species identification, discrimination of geographical origin within a country may still be challenging.
Full-text available
Preface Pulp production is increasing worldwide, especially in Southeast Asia and China (WWF 2009, Williams 2014, FAO 2015), and the use of tropical timbers from natural forests is not uncommon (Greenpeace 2012). To ensure that no protected timbers are used, those detected in pulp and paper products must be identified. Individual vessel elements are best suited for the microscopic identification of wood species in those products on the basis of typical morphological features such as type of perforation plates, presence vs. absence of helical thickenings, and type and arrangement of vessel-ray pits (Core et al. 1979, Carlquist 2001). To allow identification, a standardized morphological description of these features is required for commonly used timber. The fiber atlases by Carpenter and Leney (1952), Ezpeleta and Simon (1970 and 1971), Harders-Steinhäuser (1974), Parham and Gray (1982) and Ilvessalo-Pfäffli (1995) describe these characteristics for the main species grown in the temperate zone and in plantations. There is, however, no corresponding database available for important Asian timbers. In recent years, the rapid and reliable identification of wood species and their origin has become necessary (e.g. Dormontt et al. 2015, Koch & Schmitt 2015, Koch et al. 2015), owing to the following laws that have recently come into effect: the U.S. Lacey Act (USA, 1900/amended in 2008), the Illegal Logging Prohibition Act 2012 (Australia), and the European Timber Regulation (EUTR, No. 995/2010. implemented in 2013). Besides other timber products, these laws subject the fiber components of pulp and paper to strict controls, aiming to minimize the trade and use of illegally logged timber or products derived from it. Both producers and traders of wood products are responsible for the correct declaration of the species and origin (Koch & Schmitt 2015). To support the request for due diligence, our team from the University of Hamburg and the Thünen Institute (Hamburg, Germany) developed this atlas of vessel elements for the identification of Asian timbers, with funding from the German Environmental Foundation (Deutsche Bundesstiftung Umwelt, DBU). The vessel atlas describes 38 tropical and temperate Asian timbers, known for their potential in utilization of pulp and paper, including for the first time also lesser known species and the monocots Bamboo and Coconut palm. Each species is illustrated with high quality photomicrographs at standard magnification. Important diagnostic features are highlighted in the text and figures for easy identification. The taxonomy of the individual species is described in detail in PROSEA (1993, 1995, 1998). The selection of the taxa depends on the evaluation of about 2,150 official reports prepared at the Thünen Centre of Competence on the Origin of Timber since the implementation of the EUTR (2013) in Germany. Based on this distinct experience, the atlas includes the commonly used timbers regularly identified in fiber boards, pulp and paper from Asia, e.g. Liquidambar, Nyssa and Schima etc. Furthermore, taxa with wide distribution and high economic potential, e.g. of the families Dipterocarpaceae, Sapotaceae, etc. are considered (Helmling et al. 2016). Reference materials for the morphological description of the vessel elements are provided from vouchered specimens of the scientific wood collection (RBHw) of the Thünen Institute. Furthermore, proven assortments of mono-fractioned pulp (each pulp consists of specimens representing a single genus) were produced separately to study the influence of mechanical impact on the morphology of carefully macerated vessel elements (not damaged) and mechanically pulped fibers (partly damaged). Paper sheets of unknown mixtures (blind test) were also produced and microscopically analyzed to assess the applicability of the information contained in the atlas. The verifiable results of the blind tests clearly demonstrate its utility and practicability. Based on these experiences, the atlas should be understood as help for wood identification in pulp and paper and used as supplement to the existing fiber atlases, in particular the atlas of Ilvessalo-Pfäffli (1995) with descriptions of the wood genera mainly used in the pulp and paper production. We trust that by displaying the considerable variety of vessel elements in Asian timbers, this atlas will assist in identifying tropical and temperate wood genera in pulp, paper and fiberboards. We also hope that it may help to preserve protected tree species. S. Helmling, A. Olbrich, I. Heinz, G. Koch Hamburg, Germany 2017
Full-text available
Near-infrared spectroscopy (NIRS) is a potential, field-portable wood identification tool. NIRS has been studied as tool to identify some woods but has not been tested for Dalbergia. This study explored the efficacy of hand-held NIRS technology to discriminate, using multivariate analysis, the spectra of some high-value Dalbergia wood species: D. decipularis, D. sissoo, D. stevensonii, D. latifolia, D. retusa, all of which are listed in CITES Appendix II, and D. nigra, which is listed in CITES Appendix I. Identification models developed using partial least squares discriminant analysis (PLS-DA) and soft independent modeling by class analogy (SIMCA) were compared regarding their ability to answer two sets of identification questions. The first is the identification of each Dalbergia species among the group of the six above, and the second is the separation of D. nigra from a single group comprising the other species, grouping all Dalbergia as one class. For this latter study, spectra of D. cearensis and D. tucurensis were added to the broader Dalbergia class. These spectra were not included in the first set because the number of specimens was not enough to create an exclusive class for them. PLS-DA presented efficiency rates of over 90% in both situations, while SIMCA presented 52% efficiency at species-level separation and 85% efficiency separating D. nigra from other Dalbergia. It was shown that PLS-DA approaches are far better suited than SIMCA for generating a field-deployable NIRS model for discriminating these Dalbergia.
Full-text available
Deforestation - reinforced by illegal logging - is a serious problem in many tropical regions and causes pervasive environmental and economic damage. Existing laws which intend to reduce illegal logging need efficient, fraud resistant control methods. We developed a genetic reference database for Jatoba (Hymenaea courbaril), an important, high value timber species from the Neotropics. The data set can be used for controls on declarations of wood origin. Samples from 308 Hymenaea trees from 12 locations in Brazil, Bolivia, Peru, and French Guiana have been collected and genotyped on ten nuclear microsatellites (nSSRs), 13 chloroplast SNPs (spSNP), and 1 chloroplast indel marker. The chloroplast gene markers have been developed using Illumina DNA sequencing. Bayesian cluster analysis divided the individuals based on the nSSRs into eight genetic groups. Using self-assignment tests, the power of the genetic reference database to judge on declarations on the location has been tested for three different assignment methods. We observed a strong genetic differentiation among locations leading to high and reliable self-assignment rates for the locations between 50 to 100% (average of 88%). Although all three assignment methods came up with similar mean self-assignment rates, there were differences for some locations linked to the level of genetic diversity, differentiation and heterozygosity. Our results show that the nuclear and chloroplast gene markers are effective to be used for a genetic certification system and can provide national and international authorities with a robust tool to confirm legality of timber.
Full-text available
The invasive technique of increment coring may be unavoidable in forest ecology research requiring data on wood traits. Despite this, no study has examined the effects of increment coring on tropical forest trees. We cored 35 trees of 11 species from nine families, with wood densities ranging from 0.30 to 0.69 g cm-3, at two sites in Singapore. Tree survival, borehole closure and external signs of damage resulting directly from the coring were monitored for 1 year. Tree radial growth was estimated from changes in diameter at breast height. Of the cored trees, only one died after 1 year. Twenty-five out of the 35 trees had at least one closed borehole, and the median time to closure was 10 months. The species of tree cored was the only significant predictor of borehole closure. We observed three main categories of external damage: discoloured bark, surface wounds and the presence of fungal fruiting bodies or insects within the boreholes. Changes in the trunk diameter were not significantly different between cored and uncored trees. Our results suggest that increment coring in the tropics does not negatively impact the survival and growth of some species of tropical forest trees within the first year after coring.
We developed nuclear and plastid single nucleotide polymorphism (SNP) and insertion/deletion (INDEL) markers for Dipteryx species using a combination of restriction associated DNA sequencing (RADSeq) and low coverage MiSeq genome sequencing. Of the total 315 loci genotyped using a MassARRAY platform, 292 loci were variable and polymorphic among the 73 sampled individuals from French Guiana, Brasil, Peru, and Bolivia. A final set of 56 nuclear SNPs, 26 chloroplast SNPs, 2 chloroplast INDELs, and 32 mitochondrial SNPs identifying significant population structure was developed. This set of loci will be useful for studies on population genetics of Dipteryx species in Amazonia.
The verification of the geographical origin of timber is of increasing importance with the entry into force of new regulations having become effective (EU Timber Regulation, US Lacey Act and Australia Illegal Logging Prohibition Act) that regulate the trade of timber. Larch timber represents a significant portion of timber traded on the European market. It is mostly harvested in Russia, where trade of illegally harvested timber is known to occur. Although genetic data are available for Larix spp., robust and polymorphic marker tests are still lacking for timber DNA analysis. Using Restriction Site Associated DNA sequencing, we developed a set of 253 SNP loci which was screened on 916 Larix spp. individuals. Bayesian cluster analysis revealed the presence of eight genetic clusters showing a West-East pattern in Eurasia. This marker set resulted in assignment success rates to the region of origin ranging from 74 per cent to 88 per cent. From the full marker set, a subset of 76 loci was selected to allow cost-effective analysis of timber and was successfully tested on nine blind timber samples. The performance of genetic assignment methods and laboratory procedures for the analysis of timber DNA is discussed.
Combating illegal timber trade requires the ability to identify species and verify geographic origin of timber. Forensic techniques that independently verify the declared species and geographic origin are needed, as current legality procedures are based on certificates and documents that can be falsified. Timber from the genus Cedrela is among the most economically valued tropical timbers worldwide. Three Cedrela species are included in the Appendix III of CITES: C. fissilis, C. odorata and C. angustifolia (listed as C. lilloi). Cedrela timber is currently traded with false origin declarations and under a different species name, but tools to verify this are lacking. We used Direct Analysis in Real Time Time-of-Flight Mass Spectrometry (DART-TOFMS) to chemically identify Cedrela species and sites of origin. Heartwood samples from six Cedrela species (the three CITES-listed species plus C. balansae, C. montana and C. saltensis) were collected at 11 sites throughout Bolivia. Mass spectra detected by DART-TOFMS comprised 1062 compounds; their relative intensities were analysed using Principal Component Analyses, Kernel Discriminant Analysis (KDA) and Random Forest analyses to check discrimination potential among species and sites. Species were identified with a mean discrimination error of 15-19 per cent, with substantial variation in discrimination accuracy among species. The lowest error was observed in C. fissilis (mean = 4.4 per cent). Site discrimination error was considerably higher: 43-54 per cent for C. fissilis and 42-48 per cent for C. odorata. These results provide good prospects to differentiate C. fissilis from other species, but at present there is no scope to do so for other tested species. Thus, discrimination is highly species specific. Our findings for tests of geographic origin suggest no potential to discriminate at the studied scale and for the studied species. Cross-checking results from different methods (KDA and Random Forest) reduced discrimination errors. In all, the DART-TOFMS technique allows independent verification of claimed identity of certain Cedrela species in timber trade.
Manual sampling of large number of cores is an arduous task, especially when core diameter is large. We developed an automated tree-ring sampling device, the “smart increment borer”, to increase the sample throughput and minimize the need for muscular exertion. The lightweight, portable device employs a battery-powered electric wrench and the complete system to drive the boring operation weighs less than 10 kg. It is capable of taking both 5- and 12-mm diameter cores of more than 80-cm length. Compared to equipment used in previously published articles, this device enables more rapid sampling and demonstrates a superior torque output/total weight ratio. The device is also capable of facilitating the starting operation of a 12-mm increment borer. It facilitates a variety of effective sampling solutions for dendrochronology/climatology and wood anatomy/quality research.