1. science
2. biology
3. zoology
4. endangered species

Dr Arne Pommerening
Lecturer in Experimental Silviculture
School of Agricultural & Forest Sciences
University of Wales Bangor
Bangor
Gwynedd LL57 2UW, UK
Survey Protocol for the Establishment of Growth Series with
Permanent, Sample Plots in Planted and Semi-natural Forests
of Wales1
1
Introduction
The objectives of the establishment and measurement of permanent experimental plots as
part of so-called growth series (Æ section 1.1) are to collect data on the site, stand, and
tree characteristics, covering a range of stand ages.
Data of this kind are used particularly
ƒ
ƒ
ƒ
ƒ
for spatial analysis of stand structure
to evaluate the effects of silvicultural practices and environmental change on
stand structure and biodiversity
to develop sampling designs for (uneven-aged) mixed forest stands
to develop site dependent, distance dependent, individual tree growth models.
This survey protocol has been developed with special attention to research in mixed and
uneven-aged forests which are commonly the result of continuous cover forestry.
1.1
The growth series concept
Data gathered over a tree’s or stand’s lifetime provide the best source of information for
research into forest growth. However, where time is a limiting factor for data collection
or when information is required quickly, this approach is not possible. This has led to the
development of alternative methods one of the most common of which is the use of
growth, or unreal, time series. In a growth series a number of plots are established in
stands of varying age, the information from which is used to approximate the true
chronological sequence of stand development. For example six plots may be established
in stands of 20 to 120 years of age with 20 years between each stand. The plots of a
growth series should be established on similar site types and be as close to each other as
possible. Within the plots an enumeration of trees is carried out along with various
increment measurements which enable the development of the trees between the specific
plot ages to be interpolated. In this way we can obtain a steady picture of the change in
the most important aspects of forest yield over time.
1
This survey protocol is based on a version developed by Professor Hans Pretzsch, Chair of Forest Yield
Sciences and Forest Systems Analysis, Technical University of Munich, for the survey of the growth
dynamics of Bavarian mixed forest stands with the help of a network of growth series. It was extended
and adapted to Welsh conditions by Arne Pommerening, Francis Gwyn Jones, Jens Haufe, Steve
Murphy, Owen Davies and Mark Rogowski, SAFS, Bangor.
2
In the past both time series and growth series, have proved successful in
monitoring sum and mean values of forest stands for the derivation of yield tables. Both
concepts now have to be adapted to the specific needs of modelling the growth of
individual trees in pure even-aged forest stands and for well-structured uneven aged and
mixed stands. The main focus of this approach is the individual tree, not the forest stand.
Information is collected on the increment of individual trees dependent on tree
properties, parameters of the immediate vicinity of each tree, stand properties and
treatment effects. For a wide age range the change in diameter, height and crown width,
the shift of the base of the live crown, and mortality (or survival probability) of
individual trees has to be measured in different competition and neighbourhood
situations for every tree species. Therefore it is desirable to have a good number of trees,
which have grown under extreme neighbourhood circumstances with an exceptionally
high or low competition pressure. These extreme conditions are very productive for
modelling the reaction of individual trees dependent on growth and competition
constellation. To survey the competition and neighbourhood effects among the different
tree species there should be a wide range of mixtures and homogeneous forest stands
should be avoided. The individual tree, rather than the forest stand, is the unit of
information. Although the focus is mainly on individual tree variables, square or
rectangular plots with an extent of 0.6 - 1 hectare are desirable, because it is easier and
cheaper to survey and measure control trees in a defined area.
1.2
Terms
plot
time series
growth series
2
permanent experimental site
data from one plot covering a certain period through repeated
measurements
data from a series of plots with stands or trees of different age, but
on the same site type
Establishing a new growth series
The first step is the identification of a suitable area (with uniform site conditions, target
tree species, range of age class, etc.); this should be undertaken by SAFS staff members
in cooperation with the relevant Forest District Office (FDO). Before further steps to
select the appropriate areas are taken, the FDO should be informed and asked for
comment, permission and any support they may be able to offer. An initial field
reconnaissance should be carried out to select suitable sites. Together with members of
the FDO, sites should be selected, which contain suitable mixed stands; the selection
should have 4 - 5 stands and take into account the required age- and height-range.
If a stand seems to be suitable during an on-site inspection:
ƒ The plot boundaries should be marked roughly (flagging tape); approximately 100 m
x 100 m as standard size.
ƒ The total plot size of 0.6 to 1.0 ha is applicable to young stands, however for these
different survey instructions apply.
ƒ The stands should be described (Æ appendix 1); sample height measurements are
very important (with 5 plots per growth series there has to be 4 m to 5 m of height
difference, which corresponds with bigger age differences in older-age stands); at
3
least three height measurements have to be taken per tree species; the mean diameter
of each species must also be estimated.
ƒ The proportion of differing tree species should be small; differing tree species are
those which are not a typical element of the growth series; e.g. Sitka spruce is not
usual in a stand of oak and ash; but rowan or birch would be acceptable in a stand of
oak and ash.
ƒ All the tree species which are relevant for the particular growth series should be found
in the canopy layer, preferably in even proportions; heterogeneous stand-structures,
i.e. alternating dense and open areas are advantageous.
ƒ After a pre-selection of 4 to 5 stands (stand description and sample height
measurements will be available at this point), the areas should be inspected for a
second time by the SAFS survey team. After this second inspection confirmation of
the suitability of the plots will take place in conjunction with the FDO.
3
Plot establishment and recording
Plots should be square or rectangular 0.6 – 1.0 ha in size and consist of a core, outer area
and buffer zone (Æ appendix 2). All trees should be given a unique reference number
before any measurements are taken and this must be used throughout the survey. There
should be no measurements without tree numbers being used.
It is essential to obtain extracts of the relevant subcompartment database and as many
records as possible that are available about the past stand development and treatment for
all the plots from the FDO.
It is important to document and record all work activity carried out, particularly if this
deviates from the standard protocol. This record should include number of staff and
hours worked and the equipment used. With this information it should be possible to plan
future work from a reasonably good foundation.
3.1 Plot establishment
3.1.1 Angle trenches and boundary posts
Plot corners (and, if necessary, plot edges) should be marked with wooden posts. We
have used CCA treated posts and marked each with its station number (e.g. stn1,
stn2,…). We have also considered using buried metal with a view to using a metal
detector in the future. The corners of the core area should be marked as well. Internal
survey points may be established within the plot boundary as necessary and should be
marked in the same way. It is very important that all the boundary posts and internal
survey points (e.g. sti1, sti2,…) are marked as permanently as possible. Boundary posts
may be complemented by angle trenches. These should be dug, if possible, at every post
(30 cm wide, 20 cm deep and in each direction 100 cm long). If required and if available
stones could be used to replace or supplement the trenches. The arms of the trenches
should point directly either way to the next posts.
3.1.2 Additional plot identification
In an ambit of 15 m around the plot a number of trees, that are likely to be permanent,
should be marked with a contrasting colour to that used in the main plot. Yellow has
been found to be satisfactory for this purpose. Marking should encircle these trees at a
height of 1.5 m using a band width of approximately 5 cm. Not every tree need be
4
marked and a distance of 8 – 10 m between marked trees should suffice to safeguard the
plot.
3.1.3 Experiment number
On one of the boundary trees the number of the experiment as well as the number of the
plot should be painted, so as to be visible from the inside of the plot.
3.1.4 Enumeration
All trees with a DBH greater than 5 cm should be numbered and a line painted at DBH;
It is probably best to number the trees at the same time as marking the DBH point. The
tree number and DBH line should be close to each other and at the same side of the tree.
On a sloping site DBH is normally established on the uphill side of the tree and it is on
this side that the number should be painted unless there is reason for not doing so.
A variety of marking methods have been tried and where possible exterior grade
white paint (e.g. Williamson’s Titanium Tree Paint) should be used. DBH marks and
numbers should be checked annually and repainted if necessary. Prior to painting the
bark should be cleaned. The methods will depend on species and may range from using a
rag on smooth and thin barked species to partially removing bark with a billhook or a
slasher on thick-barked species such as pine; this preparation has a strong effect on the
durability of the marks but should not be done so as to damage the tree. The bark should
be dry prior to painting and also should not be done in frosty weather. Where trees are
too small to be painted numbered aluminium discs should be attached to a branch of the
tree using strong, clear sticky tape.
It has been found advantageous to divide the plot into strips of approximately 3 to
5 m (older forest stands 10m) and to number the trees in the strips in sequence; it will be
found that doing this will facilitate later data collection and recognition. There should be
no difference in the range of numbers in the core area and the outer area. Numbers and
marks should be discrete, e.g. not visible from foot paths and roads so as not to draw
undue attention. Dead, but standing trees, should only be numbered if they have
obviously died in the last two years.
3.1.5 DBH-line
The DBH-line should be applied at 1.3 m
above ground level (on a slope this should
be on the uphill side). This measurement
should be from where the soil covers the
base of the tree. Care should be taken with
older trees, e.g. pine, because a thick
humus cover at the base caused by e.g.
detached bark pieces could cause the
measuring point to be higher than it ought.
The figure on the right might help to
identify the DBH of trees in critical
situations.
5
3.1.6 Boundary trees
Boundary trees are trees which have their coordinates on the plot boundaries or outside
the plot, but whose crowns reach into the area of the sample plot. The boundary trees are
marked with numbers >900. If the number of trees in the plot is greater than 900, the
marking of the boundary trees starts with numbers >9000. The marking of the boundary
trees should be on the side facing into the plot. They should be recorded in the same way
as any other tree in the plot (see section 3.2).
3.1.7 Stumps, other deadwood and corners
Stumps from previous fellings and windblows are given a number greater than 5000.
Standing deadwood can be surveyed in a similar way to the living trees. Lying deadwood
should be recorded using two coordinates, one at the base the other at the tip. The
corners and intermediate boundary posts are numbered sequentially, e.g. stn1, stn2 etc.
3.2 Survey protocol for all numbered trees
All information is collected on a field computer. The following characteristics are
recorded.
3.2.1 Tree species
Tree species should be identified using scientific names as they are pre-installed in the
PenMap software in this way. A list of species names is attached (Æ appendix 3)
3.2.2 Crown class
Dominant (D)
Supressed (S)
Crowns above level of main canopy. Receive light from above,
plus some from the side (code 1).
Main canopy trees. Receive light from above but not from the side
(code 2).
Crowns extended into main canopy. Only the tops receive light
(code 3).
Crowns completely overtopped (code 4).
Dead
code 5
Co-dominant (CD)
Sub-dominant (SD)
6
3.2.3 DBH
DBH to nearest 0.1 cm (e.g. d = 16.7 cm, girth measurement, crosswise calliper
measurement if required). For the position of the DBH refer to section 3.1.5.
3.2.4 Particularities
Forked trees, crown snap, squirrel damage, beetle damage, extraction damage, overall
health etc.; encoding in accordance to instructions and PenMap pre-installation. The
preliminary site inspection will indicate anything out of the ordinary which may have to
be taken into account in customising the PenMap software.
3.2.5 Diameter at stump height/ ground diameter
The diameter at stump height has to be measured on at least 30 standing trees per tree
species and over the entire diameter range. Stump height should be considered in the
preliminary site inspection and will be above the point of root buttressing (usually at 30
cm above ground level).
3.2.6 Tree height and base of crown
At least 40 height and base of crownmeasurements per tree species should be
taken in m and measures to the nearest 0.1
m (e.g. h = 12.4 m).
ƒ Crown base per definition is defined by
the first living branch that is
contiguous with the crown; on a slope
(≥10°), the crown base is measured
once from uphill and once from
downhill side establishing an average.
ƒ As many measurements as possible are taken from the core area (at least 25 trees per
species).
ƒ Height measurements should cover the whole diameter range.
These measurements will serve to calculate a height curve typical for the stand. If the
stand is clearly divided into different layers, e.g. understorey of beech in a stand of
mature oak/beech; at least 40 heights in each layer have to be collected.
3.2.7 Tree locations
Tree locations should be surveyed, incl. stumps and boundary points using x-, y-, zcoordinates (cartesian coordinates).
3.2.8 Stump assessment
Stump assessment should take place during the survey of tree positions.
ƒ Numbers ≥5000
ƒ Tree species, if no identification possible state whether coniferous/ broadleaved tree
ƒ Diameter in cm (girth tape or calliper) to nearest 0.1 cm; estimation of original
diameter over bark may be necessary in case of decomposition
ƒ If stumps are in good enough conditions, disks may be sampled for increment
analysis.
ƒ If no disk is taken record age in grades - 1: <5 years; 2: 5-10 years; 3: 10-20 years; 4:
>20 years); if necessary the available records may have to be used. For stumps that
obviously belong to the previous rotation the age grade 5 is to be given instead of 4.
7
ƒ For every stump the reason for death should be specified if possible: 1 thinning, 2
dead standing, 3 dead lying, 4 broken, 5 windblow, 6 unknown, 7 dead hanging
3.2.9 Crown survey
Using a ‘crown window’ device
(Hussein et al., 2000), two crown shape
images should be produced for a sample
of trees covering the whole DBH range.
The crown window is a transparent
device superimposed by grid squares and
mounted on a tripod through which the
tree can be viewed. An acetate is used to
draw the shape of the crown that can be
seen through the transparent device. The following steps need to be undertaken:
1. Select appropriate position from where you can clearly see a representative outline of
the desired tree crown, distance to stem foot should be at least equal to the tree height.
2. Set up tripod with attached crown window, gridlines have to be parallel to stem axis
and window should be vertical.
3. Get bearing and distance to tree, tree height and height of crown base (Vertex).
4. Draw carefully outer shape of crown from base to top, use head stabilizer to maintain
firm distance from your eye to the window, don’t move, or do anything that could
change the perspective … assign tree number for identification, mark stem axis.
5. Additional drawings should be taken from positions shifted by ± 90° at a time.
ArcView GIS software is used to produce a series of co-ordinates tracing the outline of
each crown shape, scaled according to the measured crown length. For a form for the
survey of crown shapes Æ appendix 4.
Reference
Hussein, K. A., Albert, M. and Gadow, K. v. (2000) The Crown Window – a simple device for measuring
tree crowns. Forstw. Cbl. 119, 43-50.
3.3 Survey protocol restricted to core area
3.3.1 Estimation of crown radii
8 radii (N, NE, E etc...) should be taken. Although a
crown mirror or a spherical densiometer may be used it
has been found that that the “look up method” is
perfectly satisfactory. The results of this method,
however, should be checked or calibrated against one
of the above measuring devices. Overall the crowns of
at least 200 trees per plot (if that number is available)
should be measured. The main tree species of the plot
should be represented. These trees should be standing
in a contiguous part of the core area. Therefore it is
often necessary in older stands to measure the crown
radii of the complete core area or perhaps even the total
area.
8
In younger stands with tree numbers >200 in the core area, only a part of the area need
be recorded. However, this area need not be marked, but it should be rectangular or
square, e.g. 30m x 30m. Where the tree is leaning the centre of gravity of the crown will
not lie directly over the tree's position. It is, then, necessary to determine the projection
of the centre of gravity onto the ground and mark this with a ranging rod. The crown
radii are then taken from this point. The position of the ranging rod, in relation to tree
position (distance and angle), should be meausured and noted.
3.3.2 Height and base of crown measurements
All the trees in which the crown radii have been measured should also be measured to
establish their total height and the base of crown. These measurements may reduce the
number of trees necessary for estimating height curves, however, they may not be
representative of the whole area. Thus an extra 20 trees should be measured to create
accurate height curves.
3.3.3 Inventory of regeneration
Regeneration, i.e. young trees that have not been given individual co-ordinates (DBH
less than 5 cm) should be surveyed in a 10 m x 10 m grid system. To facilitate this the
grid will have to be permanently marked out with posts. Around each grid point a sample
quadrat with 4 m x 4 m is established so that the grid point is its centre. An accurate
sketch of this area and the numbers given to the nodes (posts) should be drawn.
In each sample quadrat
ƒ The species and number of the regenerating trees should be noted in the following
50cm-height-classes (height-class: 0=seedling; approximately less than 10 cm in
height and less than one year old, 1=10-50 cm, 2=50-100 cm, 3=100-150 cm,...).
ƒ The growth extension of the previous 5 years should be measured in the three tallest
trees per tree species and if these have reached 1.3 m height the DBH should be
measured in mm and additionally a diameter at 10 cm above ground level.
ƒ It is the apical shoot length that should be measured, not the height increment. This is
important especially for young trees which often have curved shoots and stems, e.g.
beech.
3.3.4 Stem analysis inside the experimental plot
Windblows, thinnings, etc. inside the plot should be used to carry out stem analysis. If
there are none of the latter, selected trees may even be felled for that reason. On standing
trees, North should be marked on the stem before felling. Measurement of annual shoot
growth should be carried out as far backwards as possible and snedding has to be done in
a way that does not complicate this. The stem should then be marked for disk sampling.
Disks should be taken at 2 m intervals, starting at 1.3 m height (i.e. at 3.3, 5.3, 7.3 m
etc.). Additional disks should be taken at 0.3 m and at 30% of total tree height. North
should be marked at each disk before cutting the disks off. Disks are to be labelled with
plot number, tree number, and disk position. The use of an electric planer has proved to
facilitate further analysis; small disks may be planed on a lathe. Analysis or scanning of
the disks should be done not later than 48 hours after sampling.
3.3.5 Soil survey
On each experimental plot a soil pit should be dug in the approximate centre of the plot.
The pit should be large enough to allow adequate description and sampling, and be
constructed in such a way to allow easy entrance and exit and escape for small creatures.
The headwall of the pit should be at least two thirds the crown radius away from any
9
tree. The soil should be described using standard soil survey procedures and identified
using FC nomenclature. If permission is obtained the pit should be left open for teaching
and demonstration purposes. In this case it should be fenced to avoid any forest visitor
falling into it. Soil heterogeneity should be checked over the whole plot and any major
variations described and sampled if necessary.
3.4 Survey protocol restricted to the outer area
3.4.1 Increment boring
Increment cores should be taken from a sample of trees, which should cover the whole
DBH range. On every tree of the outer area with a DBH ≥ 40cm two increment cores
should be taken, one from the NE, one from the SW preferably at a height of 1.1m
(boring height should be recorded). The increment core of old trees should reach at least
40 years into the past.
ƒ The use of 8mm borers is preferable.
ƒ Broadleaved trees: DBH ≥ 12cm boring once from NE; DBH ≥ 20cm both from NE
and SW.
ƒ Conifers: DBH ≥ 10cm drilling once from NE; DBH ≥ 15cm both from NE and SW.
3.4.2 Tree diameter at 1.1m height
If increment boring is performed at a height of 1.1 m and not at 1.3 m above ground
level, the diameter at 1.1 m (boring height) of at least 30 standing trees per species
should be measured; this should cover the complete diameter range.
3.4.3 Age cores
If tree age is unknown, cores from the bases of 3-5 trees per species should be taken
(boring height should be noted) in order to determine tree age; if the centre is not hit reboring should be limited to two more attempts. If a thinning is planned, these age cores
become unnecessary as the annual rings can be counted on the fresh cut stumps (stump
height should be noted).
3.4.4 Stem analysis outside the experimental plot
If the analysed tree was located outside the plot, the tree itself as well as all neighbour
trees affecting its growth space should be numbered (using a sub-range of numbers), and
tree position, species, DBH, crown class, and height should be recorded. A sketch should
10
be drawn of this "sample circle" and its position in relation to the nearest experimental
plot should be recorded with the total station. The tree that is to be analysed should be
treated as in section 3.3.6 above.
3.4.5 Boundary trees
See section 3.1.6.
Arne Pommerening, Francis Gwyn Jones,
Jens Haufe, Steve Murphy, Owen Davies and
Mark Rogowski, October 2002
11
Appendix 1
Stand description
Growth series:
Compartment:
Planting year:
General stand description:
Mixture distribution:
Species mixture (in %):
Crown density (% of sky - % of canopy):
Mean diameter:
Mean height:
Height measurements:
1
2
3
4
5
6
tree species
Reconstructable position sketch:
height
DBH
12
Appendix 2
Area layout for all age classes ( incl. young stands)
ƒ
ƒ
ƒ
ƒ
total area = core section/inner area + outer section
required size of the total area: 0.6 to 1.0 ha
buffer: at least 10m wide
for distances and areas horizontal projections should be used
buffer zone
outer area
core area
at least 30 m x 30 m
>5m
> 40 m
> 10 m
ƒ The outer area surrounds the core area to a width of at least 5m (e.g. total area 60m x
50m, core section 50m x 40m)
ƒ Core and outer area have to be square or rectangular
13
Appendix 3
Forestry Commission Species Codings
Common Name
Scots pine
Corsican pine
Lodgepole pine
Austrian pine
Maritime pine
Weymouth pine
Mountain pine
Bishop pine
Monterey pine
Ponderosa pine
Macedonian pine
Other pines
Sitka spruce
Norway spruce
Omorika spruce
Other spruces
European larch
Japanese larch
Hybrid larch
Douglas fir
Western hemlock
Western red cedar
Lawson's cypress
Leyland cypress
Grand fir
Noble fir
Silver fir
Other firs (Abies)
Japanese cedar
Coast redwood
Wellingtonia
Other conifers
Mixed conifers
Oak
Pendunculate oak
Sessile oak
Red oak
Beech
Sycamore
Norway maple
Ash
Birch
Poplar
Sweet chestnut
Horse chestnut
Alder
Common alder
Grey alder
Red alder
Sitka alder
Green alder
Lime
Common lime
Small-leaved lime
Large-leaved lime
Elm
English elm
Wych elm
Smooth-leaved elm
Wild cherry, Gean
Bird cherry
Hornbeam
Roble
Rauli
Raoul
Hazel
Other broadleaves
Mixed broadleaves
Code
SP
CP
LP
AUP
MAP
WEP
MOP
BIP
RAP
PDP
MCP
XP
SS
NS
OMS
XS
EL
JL
HL
DF
WH
RC
LC
LEC
GF
NF
ESF
XF
JCR
RSQ
WSQ
XC
MC
OK
POK
SOK
ROK
BE
SY
NOM
AH
BI
PO
SC
HCH
AR
CAR
GAR
RAR
SAR
VAR
LI
CLI
SLI
LLI
EM
EEM
WEM
SEM
WCH
BCH
HBM
OBN
PRN
RAN
HAZ
XB
MB
Botanical Name
Pinus sylvestris L.
Pinus nigra var. maritima (Alton) Melville
Pinus contorta Douglas
Pinus nigra var. nigra Harrison
Pinus pinaster Ait.
Pinus strobus L.
Pinus uncinata Miller
Pinus muricata D. Don
Pinus radiata
Pinus ponderosa Douglas
Pinus peuce Griseb.
Pinus spp.
Picea sitchensis (Bong.) Carr.
Picea abies(L.) Karst
Picea omorika (Pancic) Purkyne
Picea spp.
Larix decidua Miller
Larix kaempferi (Lambert) Carr.
Larix eurolepsis Henry
Pseudotsuga menziesii (Mirb) Franco
Tsuga heterophylla (Raf.) Sarg.
Thuja plicata D. Don
Chamaecyparis lawsoniana (A. Murr.) Parl
Cupressocyparis leylandii (Jacks. and Dallim) Dallimore
Abies grandis Lindl.
Abies procera Rehd.
Abies alba Mill.
Abies spp.
Cryptomeria japonica (L.f.) Don
Sequoia sempervirens (D.Don) Endl.
Sequoiadendron giganteum (Lindl.) Buchholz
Quercus spp.
Quercus robur L.
Quercus petraea (Matt.) Lieblein
Quercus borealis Michx. f.
Fagus sylvatica L.
Acer pseudoplatanus L.
Acer platanoides L.
Fraxinus excelsior L.
Betula spp.
Populus spp.
Castanea sativa Mill.
Aesculus hippocastanum L.
Alnus spp.
Alnus glutinosa (L.) Gaertn
Alnus incana (L.) Moench
Alnus rubra Bong.
Alnus sinuata
Alnus viridis (Chaix) DC.
Tilia spp.
Tilia europaea L.
Tilia cordata Miller
Tilia platyphyllos Scop.
Ulmus spp.
Ulmus procera Salisb.
Ulmus glabra Hudson
Ulmus carpinifolia Gleditsch
Prunus avium (L.) L.
Prunus padus L.
Carpinus betulus L.
Nothofagus obliqua (Mirb.) Blume
Nothofagus procera (Peopp. and Endl.)
Nothofagus nervosa
Corylus avellana L.
SS
SS
SS
SS
SS
SS
Crown base ht 2
Height 2
Distance 2
Bearing 2
Crown base ht 1
Height 1
Distance 1
Bearing 1
Crown base height
Height
Dbh
Tree no.
Species
14
Appendix 4
Crown radius
(to be measured with tape from stem
surface at 1.3 m height, horizontally)
E
SE
S
SW
W
NW
N
NE