The location of threatened species` populations is the most

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BRIEF
1
How to survey an area for
threatened tree species
Credit: Li Xiaoya/FFI
The location of
threatened species’
populations is the most
fundamental information
required for their
conservation
D. A. Keith (2000)
Introduction
Protecting and monitoring a tree species cannot
occur without first knowing where the population
can be found and how many of its individuals
remain. However, tree species under threat from
extinction are often rare, poorly known and grow
in areas that may be difficult to navigate. The
purpose of this brief is to provide basic guidance
on how to determine presence, distribution and/or
population size of target threatened species within
an area of interest.
Who is this guidance for?
This Brief
was written by
Steven Brewer
The Global Trees Campaign is a partnership between:
Copyright 2013 Global Trees Campaign.
Individuals in conservation organizations (NGOs,
forest departments, protected-area managers,
etc.) tasked with protection and conservation of
a particular species. Specialised training is not
required, but some basic skills (detailed on Page 3)
should be present within the survey team.
This brief was produced by Fauna & Flora International (FFI)
as a contribution to the Global Trees Campaign
www.globaltrees.org
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BRIEF
1
How to survey an area for
threatened tree species
Before you start
Two common mistakes made when conducting species surveys are (1) rushing out to the field before knowing
exactly what kind of prior information and skills are needed, and (2) trying to do too much too soon, rather than
taking a long-term view of what is trying to be accomplished. By following the step-by step guide below, you
will be able to complete more efficient and effective surveys.
Step 1: Determine the purpose of your survey
What is the primary purpose(s) of the survey? Is it to determine whether the species is present? Or is it
to determine distribution and/or the abundance of that species?
Step 2: Select your survey method
Your choice of method will depend on the primary purpose of your survey. Some methods focus
effort on areas of high potential habitat for the target species whereas others take a more systematic
approach. An appraisal of available survey methods is given in Pages 4-5.
Step 3: Know your species in advance
All existing information about the target species should be collated and stored in one place, with backup
copies stored elsewhere. This information can be gathered from published literature, reports and other
studies, herbarium specimens and collections databases, as well as from local loggers, hunters, and
villagers who use the species or spend time in habitats where they are found. If time is limited, at least
make sure you have an idea of where to go (see ‘Location’), when to go (see ‘Phenology’) and what to look
for (see ‘Identification issues’).
Location
What kind of environment
preferences does the species
have, if any? Start by examining
how rainfall, geology/soils,
topography, elevation, and
environmental disturbances such
as fire or storm damage helps or
hurts populations of the species.
Many herbarium specimens have
GPS coordinates attached to
them, helping you to determine
locations and suitable habitats
for fieldwork.
Phenology
What time of year does the
species fruit, flower or drops its
leaves (if it does so periodically)?
This may help inform the timing
of fieldwork – often, the quickest
way to find a tree species
growing in a mixed forest is to
look for the fruits, flowers, or
leaves of the target species.
Identification
issues
Are there any closely-related, or
unrelated, tree species that might
be mistaken for this species in
the area? If so, how do you tell
the differences? The best way
to gather this information is from
a botanist who specializes in the
relevant plant family. Botanists can
be found at herbaria (institutions
that house plant specimens,
data, and scientists). Other good
sources include floras (books on
the plants of a particular area).
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2
BRIEF
1
How to survey an area for
threatened tree species
Step 4:
Make sure your team has the right skills
Your team should have the following skills
1)Map Reading:
a) Looking at a topographic map and interpreting specific
landscape features, for example what parts of the map
show hilltops, slopes, streams, valleys etc.;
b) Reading approximate latitude and longitude from a specific
point on the map, or putting a marker on the map that
matches the location of a given latitude and longitude.
2) Navigation and use of a handheld GPS device:
a) R
ecording locations of trees on the GPS or re-locating a tree
already recorded on the GPS;
b) Following and laying-down “tracks” (records of where one
walked) on the GPS device.
3)Use of a compass: Finding a tree if given an azimuth
(compass direction in degrees) and walking along an azimuth.
4)Use of a meter and DBH (Diameter at breast height) tapes:
a) Reading distances along a tape and estimating distances
using a meter tape;
b) Determining the width of a tree stem using a DBH tape.
5)Plant identification: identification of the species of interest
is critical but does not necessarily require a botanist. Tree
spotters who work for logging operations are the best
immediate source for finding the target species, but anyone
who spends large amounts of time in forests can readily
pick up how to identify a particular species. When the
identification of a tree is in doubt, see GTC Brief 2 for advice
on how to collect voucher specimens.
How do you
measure DBH?
To measure the Diameter at
breast height of larger trees,
take readings (in cm) from a
diameter tape wrapped around
the tree stem (at 1.3 metres
above the ground) or use an
ordinary measuring tape and
divide the girth by Pi (3.14).
DBH of saplings and small
trees is typically measured
using callipers.
Step 5: Acquire field equipment
GPS and extra batteries
Compass
10X or 15X Hand lens for examining plant
material for identification
Topographic Maps
Daypack for carrying equipment
DBH Tape (optional for some methods)
Knife or machete for cutting tree bark
(aids in tree identification)
Weather-resistant field notebooks and
mechanical pencils
Camera for recording plant features (optional)
Field guide (if available) or notes
for identification
Meter Tape (optional for some methods)
Binoculars for identifying tall trees (looking at
leaves, flowers, fruits, etc. in the canopy)
Food, water, and other personal gear
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BRIEF
1
How to survey an area for
threatened tree species
Available methods for your field survey
Method 1: Focused or Intuitive-Controlled Surveys
This method focuses the intensity of surveys on areas of high potential habitat for the target species,
using the experience, field “intuition” and preparation of the surveyor to guide the survey.
ADVANTAGES:
DISADVANTAGES:
Enables you to cover most of the species’ likely
habitat without having to cover the entire survey area
Provides an incomplete survey; one cannot exclude
the possibility that the target species occurs in areas
not surveyed
Efficient and relatively low cost
Requires field experience in similar areas and habitats
May provide a preliminary estimate of population
size of the target species
Requires information on (a) the survey area and (b)
what constitutes suitable habitat for the target species
to be prepared beforehand
How this works in practice:
1. D
etermine your areas of high-potential habitat by marking them on a map. You can then plan survey
routes based on locations of major landscape features/habitat types and logistical considerations such as time
available, difficulty of the terrain, where to place campsites and number of personnel. Reconnaissance trips to
the field may be necessary for planning.
2. V
isit major habitats and landscape features (e.g., hill tops, slopes, valleys, etc.) on the way to high
potential habitats, in order to get a preliminary idea of whether or not the target species occurs in any type
of habitat other than those believed to be of high potential. Focus on covering features that influence what
kinds of plants grow there – i.e. anything that affects light, water availability and soils. These ‘microhabitats’
(disturbed areas, rock outcrops, moister areas, drier exposed areas, ravines, etc.) can be surveyed as
opportunities arise.
TOP
TIP
3. S
urvey high-potential habitats by walking
across all parts of them and by making
complete tree counts. You should collect
basic data on each tree you record
including its DBH and reproductive
condition (see Data Collection on
page 6).
Intuitive Controlled
The presence of seedlings is an indicator
that one or more larger individuals of the
species are or were somewhere nearby.
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BRIEF
1
4. E
stimate abundance of the target
species by assessing the extent of
each sub-population (different patches
of trees of the species). Walk the
approximate edges of patches and delimit a
‘minimum convex polygon’. Then estimate
the numbers of trees present inside each
delimited patch. In this method, a surveyor
walks through a patch of trees and simply
gives a visual estimate of the number of
trees within the area.
How to survey an area for
threatened tree species
Minimum convex
polygon
Drawn around the outside perimeter of the
population or patch of trees by walking in
6-8 compass bearings from a point near
an estimated center of the patch.
The trees farthest from the center are
used to mark the outside boundaries of
the patch. Not all tree locations have to be
determined. The area of the polygon can
be calculated with GIS software.
Method 2: Systematic & Complete
In this method, the surveyor walks systematically (regularly and evenly) through an entire area, locating
all trees at or exceeding a minimum size class.
ADVANTAGES:
DISADVANTAGES:
Provides an accurate measure of population extent
and abundance of the target species
Inefficient for very large areas (i.e. takes more time to
complete for a given size of habitat)
Works well for species that are poorly known in
habitat preferences or for generalist species that grow
in many habitat types
Relatively expensive compared to focused surveys
How this works in practice: using plots and transects
Two common types of methods used for biological surveys are plots (square, rectangular or sometimes circular
boundaries used to delimit areas) and transects (lines, or narrow strips of land of a set width, along which a
surveyor walks). These methods can be used to:
completely survey an entire area
provide a representative sample(s) of larger areas
survey species with no known habitat preferences and/or
monitor tree populations over time.
Plots are placed in different habitat types and are completely surveyed
for the target species. Due to its complexity, it is recommended
that the use of plots in this manner be guided by an ecologist
experienced in plot studies.
Plots in
Survey
Area
ransects are used to cover large, heterogeneous
T
areas in a rapid but more systematic manner than
focused surveys. Transect surveys involve a team of
1-2 tree spotters and 1 data collector recording target
trees. The team lays out a measuring tape and walks
along the tape, recording where target trees are located
along the tape to the nearest metre.
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BRIEF
1
How to survey an area for
threatened tree species
Transects may take several forms:
evenly spaced within the entire survey area
laced in at least one of each habitat type and/or topographic
p
feature (e.g. on hills, slopes, valleys) in the survey area or
in combination with focused surveys, concentrated in areas of
suitable habitat for the target species. Combining transects with
focused surveys is effective for finding target species that grow
in very small patches (<5 individuals in a patch) or as widelyscattered individuals.
Transects should have a uniform width (and length if possible), to
make data collection comparable among areas. For rapid surveys,
transect widths should be no more than 4m in closed forests. In woodlands or open savannahs transects can be
wider: as much as 50-100m. Transects can be curved, but the more so that they are, the less acceptable they
become as a survey method.
2. Missing trees
1. Close together transects may cause you to ‘double count’
the same individual tree from adjacent lines. Avoid this
by only collecting data on trees sighted within the
transect boundary.
TOP
TIP
1. Double counting
2. On the other hand, transects that are too far apart may
cause you to miss a large number of trees in the
space in between them.
Collecting and managing your data
The precise data you collect will depend on the survey method you employ. We suggest, as a minimum, that
you record the data collector’s name, the survey date and location (e.g. which site, plot or transect), the Map
Datum you are using and the location and names of the trees you observe. You should also have a unique
number associated with each individual tree and/or population and collect data on each tree’s DBH and
reproductive condition.
An example datasheet is provided that you may modify for your own purposes. Photo-documenting and taking
notes on characteristics of individual trees are strongly encouraged; these can be written on the back of the sheet
or in a separate notebook. This helps to document characteristics either not available in field guides or difficult to
describe, and may serve as a reference for trees of questionable identity.
Data Collectors Name: Jose Castello
Date: 30/11/2013
Location of survey: Threatened Tree National Park
Map Datum: WGS1984
Transect Number: 2
Transect Begins: 16.184120; -88.924030
Transect Ends: 16.184280; -88.923901
Tree Species
Latitude
Longitude
Point ID
DBH (cm)
Reproductive Condition
Dalbergia stevensonii
16.184116
-88.924026
001
20
Not-reproductive
D. stevensonii
16.184110
-88.924026
002
15
Not-reproductive
Quiina schippii
16.184110
-88.924020
003
29
In flower
D. stevensonii
16.184101
-88.924021
004
40
Not-reproductive
Q. schippii
16.184111
-88.924019
005
23
Fruiting
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BRIEF
1
How to survey an area for
threatened tree species
What Next?
Data collected in the field should be transferred from data sheets onto a computer for basic data analysis. By
analysing your survey data you may be able to answer key questions such as:
Where does the target species occur?
How large is/are the population(s) of the target species?
hat is the population structure of the species (e.g. the relative number of mature trees, saplings
W
and seedlings)?
oes the target species occur in specific habitat types or topographic/geological features in
D
the landscape?
Products from basic data analysis may include:
(1) A
topographic map of tree locations, produced by plotting coordinates by hand or in GIS software (usually very
basic software is included with your GPS).
(2) B
asic statistics on abundance, location, and habitat for your target species. These may include:
Total number of stems
Maximum, minimum and average DBH
% of trees in each category of reproduction
Elevation range of the species
(3) M
inimum convex polygons, or the total area, covered by the overall population or by each cluster
(sub-population) of individual trees.
Using your data
Survey data can be used to support a number of longer-term conservation actions for your target species including:
Identifying
priority locations for long-term
monitoring and patrolling (see GTC Brief 3
for advice on Monitoring)
Identifying ‘mother trees’ for future seed
collection (see GTC Brief 5 for advice on
Seed Collection).
Identifying suitable habitat types and locations
for planting (see GTC Brief 9 for advice on
reinforcing wild populations of threatened trees).
sing the data to predict the locations of other
U
populations in un-surveyed areas. This requires
the expertise of someone familiar with regression
models and GIS statistics.
haring the data with other scientists
S
and conservation organisations. Data can
contribute to national, regional or global Red
List assessments or can be used to inform
conservation action plans for the species.
Analysing data on the location of tree species will help you identify and revisit priority sites for
regular monitoring. Credit: Zhao Xingfeng/FFI
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7
BRIEF
1
How to survey an area for
threatened tree species
Selected references and further guidance
References and further guidance on some of the methods described in this brief are provided below.
Guidance on map reading:
National Wildfire Coordinating Group – Reading Topographic Maps and Making Calculations:
http://bit.ly/gtc_ref_1a
National Geographic – Basic Map & GPS skills: http://bit.ly/gtc_ref_1b
Guidance on navigation & use of a handheld GPS
GARMIN GPS guide for beginners: http://bit.ly/gtc_ref_1c
Guidance on how to use a compass
Black Owl Outdoors – Video – How to Use a Compass and Map: http://bit.ly/gtc_ref_1d
National Wildfire Coordinating Group – Using a Compass and Clinometer: http://bit.ly/gtc_ref_1e
Guidance on sampling design
Condit, R. (1998). Tropical Forest Census Plots. Springer-Verlag, Berlin: http://bit.ly/gtc_ref_1f
Keith, D.A. (2000). Sampling designs, field techniques and analytical methods for systematic plant population
survey. Ecological Management & Restoration, 1: 125–139.
Newton, A.C. (2007). Forest Ecology and Conservation: A Handbook of Techniques. Oxford University Press, UK.
Guidance on measuring trees
Washington State University Extension – Lesson 6: Measuring Trees: http://bit.ly/gtc_ref_1g
Husch, B., Beers, T.W. and Kershaw, J.A. (2003). Forest mensuration. Wiley, New York.
Guidance on analysing survey data
Kindt, R and Coe, R. (2005). Tree diversity analysis. A manual and software for common statistical methods for
ecological and biodiversity studies. Nairobi: World Agroforestry Centre (ICRAF): http://bit.ly/gtc_ref_1h
For more information, or to download the other briefs in this series, visit
www.globaltrees.org/resources/practical-guidance
The Global Trees Campaign is a partnership between:
This brief was produced by Fauna & Flora International (FFI)
as a contribution to the Global Trees Campaign
www.globaltrees.org
twitter.com/globaltrees
www.facebook.com/globaltrees
Copyright 2013 Global Trees Campaign.
8
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