The tallest canopy and the highest carbon stock for a forest stand in Sri Lanka

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SHORT COMMUNICATION
244 TAPROBANICA VOL. 09: NO. 01
The tallest canopy and the highest carbon
stock for a forest stand in Sri Lanka
The height of the canopy of a forest has been
noted as an important structural parameter in
characterizing particular forest types in Sri
Lanka (Ashton et al. 1997, Koelmeyer 1957,
Peeris 1975). However, only limited studies
have been carried out on the carbon stocks of
different natural forest types, which is also an
important structural parameter of forests. As per
the scientific literature mentioned above, the
tallest canopy forests are wet zone lowland rain
forests in the south western part of the country.
The forests are dominated by trees of the family
Dipterocarpaceae and reach a maximum canopy
height of 45 m (Gunatilleke et al. 2008).
A preliminary botanical survey conducted in
the hitherto unexplored Udakeeruwa forest in
the eastern intermediate zone climatic zone, in
Badulla district, revealed an unusually tall
canopy of a natural forest patch dominated by
dipterocarp trees. With the guidance of the local
community, it was possible to record the height
of a newly fallen mature tree of Dipterocarpus
zeylanicus. The total height from the base of the
stem to its apex green point was recorded as
72.3 m. However, there could have been an error
of 1–2% since the natural green apex point was
difficult to recognise in the fallen tree.
Moreover, some slender woody branches of the
top part of the tree were broken away. This
observation prompted a further study into the
forest canopy height levels, and forest carbon
content, which is often higher in taller forests.
There were two objectives for this study: (1)
to understand the natural forest vertical structure
with particular reference to canopy height, and
(2) to investigate total carbon content of the tree
flora. The studied forest area is located adjacent
to Udakeeruwa Village (7.050902 N, 81.233480
E; alt. 513 m a.s.l.), in Badulla District, Sri
Lanka. The area falls within the eastern
intermediate climatic zone with mean annual
rainfall from 2,000–2,500 mm (Survey
Department 1988). It was observed that the
dipterocarp-dominated tall canopy forest patch
under investigation is not widespread locally but
confined to a small geographic area of
approximately 2 km2, in a valley bottom
surrounded by low hills (Fig. 1A).
Study of forest vertical structure and
canopy height: Vertical structure of the forest
was studied by drawing a forest profile diagram.
A transect of size 100 m × 5 m, which was
representative of the least disturbed area of
mature forest was selected. A profile diagram
was drawn to show the overall vertical
appearance of the forest. Scaled line drawings of
all trees above or equal to 50 cm girth at breast
height were made. Trees of higher girth classes
were measured to better highlight taller trees in
the profile diagram. The height of each tree was
measured using a Suunto hypsometer (Suunto
Oy Company, Finland) which is based on simple
trigonometric principles. The vertical forest
profile (Fig. 2) drawn for the sample site shows
that large diameter trees are vertically organized
into three strata; canopy (55–67 m), sub canopy
(30–40 m) and under story (15–25 m). It is
interesting to note that none of the natural forest
canopies elsewhere in Sri Lanka are reported to
be 55–67 m high. This unusual height may be
due to the following reasons: (a) the forest being
situated in a valley flanked by two hills ensures
it is well protected from strong winds and hence
trees can grow to great heights with no natural
obstructions; (b) the hills on both sides run north
to south, which limits the period of direct
sunlight reaching the valley floor (Fig. 1B).
Therefore, it is likely that strong competition for
light has promoted vertical growth; and
apparently, the valley being a fertile area, can
sustain high biomass forests.
The tallest tree recorded was a 67 m Shorea
dyeri (Diperocarpaceae). This tree is 6.3 m
shorter than the fallen Dipterocarpus zeylanicus
measured previously in the same forest stand.
However, even when used correctly, the Sunnto
hypsometer can have an error of about 2.5%
(Brack & Wood 1998). So far, the tallest tropical
TAPROBANICA, ISSN 1800–427X. November, 2020. Vol. 09, No. 02: pp. 244–247.
© Research Center for Climate Change and Department of Biology, Faculty of Mathematics &
Natural Sciences, University of Indonesia, Depok 16424, INDONESIA.
http://www.taprobanica.org/
https://doi.org/10.47605/tapro.v9i2.242

THE TALLEST CANOPY & CARBON STOCK FOR A FOREST STAND IN SRI LANKA
245 TAPROBANICA VOL. 09: NO. 01
tree in the world has been measured as 94.1 m
using laser technology; a tree in Borneo,
tentatively identified as Shorea species (Dockril
2016).
Assessment of forest carbon: Enumeration
was done for woody plants (mainly trees and
some lianas) having a girth at breast height of 10
cm or above (Table 1). Trees were enumerated in
20 plots, 10 ×10 m in size. All the plants species
enumerated were identified using field guides
and referring specimens to the National
Herbarium of Sri Lanka. Plots were laid
randomly in areas judged to be representative of
dipterocarp forest in the field. Girth values of
plants were used in calculating species specific
carbon content using the following allometric
equations:
Above ground biomass in kg (AGB) =21.297–
6.953 (DBH) + 0.740 (DBH)2 (Brown1997).
DBH=diameter at breast height in centimetres.
Below Ground biomass in kg (BGB) =AGB (kg)
× 0.127 (Brown & Iverson 1992). Total biomass in
kg=AGB+BGB; total carbon content=total biomass
[kg] × 0.474 (Martin & Thomas 2011).
The overall analysis of the girth data shows
that the total carbon stock of the woody flora of
a 2,000 m2 area is 140,816.85 kg (704.08
Mt/ha). That amount of sequestered carbon is
distributed among 53 woody plant species
(Table 1) with 627 individuals. The five leading
woody species in descending order of
percentage carbon stock are Dipterocarpus
zeylanicus (59.75%), Shorea dyeri (22.74%),
Mallotus fuscescens (5.06%), Artocarpus nobilis
(2.16%) and Bhesa ceylanica (1.68%). The total
forest carbon stock per ha in this forest is higher
than that of comparable forest types in the wet
zone of Sri Lanka, assessed by Chave et al.
(2008). Once AGB data from Chave et al.
(2008), is converted to total carbon content, it
amounts to 403.35 Mt/ha for woody plants equal
to or above the 1 cm diameter at breast height
used in that study. The pattern of distribution of
carbon content among species is highly
asymmetric, with 82.49% of the total carbon
stock in two species: Dipterocarpus zeylanicus
and Shorea dyeri. Both species are massive trees
of the Dipterocarpaceae family (Fig. 1C).
Moreover, 91.39% of the total carbon stock is
within the first five leading species. The balance
of 8.51% carbon stock is spread over 49 other
woody species.
Table 1. Estimated carbon content of different woody species
No
Plant species
Carbon (kg)
No
Plant species
Carbon (kg)
1
Dipterocarpus zeylanicus
84,140.72
28
Stemonurus apicalis
58.40
2
Shorea dyeri
32,022.16
29
Rourea minor
38.07
3
Mallotus fuscescens
7,120.89
30
Syzygium aqueum
29.38
4
Artocarpus nobilis
3,039.43
31
Syzygium makul
27.46
5
Bhesa ceylanica
2,369.72
32
Areca catechu
26.16
6
Mangifere zeylanica
1,510.13
33
Strombosia ceylanica
17.15
7
Hydnocarpus venenata
1,443.29
34
Eugenia rufo-fulva
16.95
8
Artocarpus heterophyllous
1,162.45
35
Palaquium hinmolpedda
15.19
9
Ficus drupacea
846.82
36
Acacia pennata
12.92
10
Myristica ceylanica
803.25
37
Semecarpus nigro-viridis
10.68
11
Horsfieldia iryaghedhi
796.32
38
Caryota urens
9.49
12
Goniothalamus hookeri
739.18
39
Cinnamomum verum
9.49
13
Garcinia quaesita
671.77
40
Uncaria elliptica
9.28
14
Macaranga peltata
567.25
41
Euonymus walkeri
9.28
15
Dimocarpus longan
545.53
42
Pandanus ceylanicus
9.11
16
Agrostistachys indica
444.73
43
Nothopegia beddomei
8.41
17
Uvaria semecarpifolia
429.17
44
Connarus monocarpus
6.84
18
Timonius flavescens
321.46
45
Mangifera indica
5.37
19
Aporusa acuminata
264.24
46
Calophyllum calaba
5.35
20
Calophyllum tomentosum
251.17
47
Gomphia serrata
4.75
21
Alstonia scholaris
229.18
48
Diospyros ebenoides
2.78
22
Litsea longifolia
183.36
49
Glochidion nemorale
2.78
23
Antidesma sp.
152.23
50
Pterospermum suberifolium
2.78
24
Entada pusaetha
137.54
51
Crptocarya wightiana
2.72
25
Dalbergia pseudo-sissoo
110.07
52
Gomphandra coriacea
2.71
26
Flacourtia indica
86.80
53
Salacia oblonga
2.65
27
Olax zeylanica
81.86
Total carbon 140,816.85 kg/2,000 m2

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244 TAPROBANICA VOL. 09: NO. 01
Figure 1. (A) The study site in relation to larger
landscape view; (B) Lofty dipterocarp trees in the
forest; and (C) Frequent occurrence of large trees
close to each other largely contributes to high level of
carbon stock in the forest.
The dipterocarp-dominated forest stand at
Udakeeruwa can be classified as the tallest
canopy natural forest in Sri Lanka. Dipterocarp-
tree species are the prominent component of the
uppermost layer of the forest canopy. This forest
stand has the potential for attracting eco-tourists,
researchers and other interest groups on account
of its outstanding botanical features and
charisma. Meanwhile, due attention has to be
paid to strengthening its conservation in a
socially beneficial manner, considering the on-
going anthropogenic pressures on the forest. It
seems likely that taller trees, than those noted
here, are to be found in this forest. The use of
advanced techniques like laser scanning (Dockril
2016) for the accurate non-destructive
measurement of tree heights might be used and
could add valuable data to help conserve the
forest.
The present initial study on forest carbon
stocks of Udakeeruwa forest enriches the current
knowledge base on the carbon sequestration
potential of another forest in a remote locality in
Sri Lanka. As per available literature, the forest
carbon stock of this forest is the highest for a
natural forest in Sri Lanka, which calls for
policy and programs to protect this carbon rich
natural forest for climate benefits. Information
on taller tree species with higher carbon stocks
provide guidance on plant selection for
restoration forestry for enhancing ecosystem
services in degraded sites having climatically
similar conditions.
Figure 2. Profile diagram of a forest patch at
Udakeeruwa; Bhesa ceylanica (7), Dipterocarpus
zeylanicus (2, 8, 12, 18), Mallotus fuscescens (3, 5, 6,
10, 11, 14, 16), Pometia pinnata (13, 17), Shorea
dyeri (1, 9) and dead stumps of large trees (4, 15);
transect size: 100 m × 5 m; minimum GBH of
selected trees: 50 cm.
Acknowledgment
We thank Biodiversity Secretariat (the Ministry
of Environment and Mahaweli Development of
Sri Lanka) for providing financial assistance for
this study. Also, we appreciate the support
provided by the staff of Forest Department and
National Herbarium of Sri Lanka. Finally we
thank Chris Margules (James Cook University,
Australia) for reviewing the manuscript.
A
B
C
EKANAYAKE & FERNANDO 2020
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THE TALLEST CANOPY & CARBON STOCK FOR A FOREST STAND IN SRI LANKA
245 TAPROBANICA VOL. 09: NO. 01
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Submitted: 05 March, Accepted: 31 October 2020
Section Editor: Gbadamassi G.O. Dossa
S. P. Ekanayake1,2 & R.H.S.S. Fernando1
1 Center for Applied Biodiversity Research and
Education (CABRE), 209/3, Allen Avenue, Dehiwala,
Sri Lanka
2 E-mail: sekanayake@gmail.com
Published date: 28 November 2020
247