Nativa, Sinop, v. 9, n. 3, p. 318-326, mai./jun. 2021.
Pesquisas Agrárias e Ambientais
DOI: https://doi.org/10.31413/nativa.v9i3.12042 ISSN: 2318-7670
Crown morphometry for two valuable timber species from Miombo
woodland in Mozambique
Noé dos Santos Ananias HOFIÇO1*, Emanuel Arnoni COSTA2, Frederico Dimas FLEIG3,
César Augusto Guimarães FINGER3
1Department of Forest Engineering, Zambeze University – UniZambeze, Mocuba, Zambézia, Mozambique.
2Department of Forest Engineering, Federal University of Uberlândia, Monte Carmelo, MG, Brazil.
3Department of Forest Sciences, Federal University of Santa Maria, Santa Maria, RS, Brazil.
*E-mail: noe.hofico@gmail.com
(Orcid: 0000-0003-2554-4576; 0000-0002-0644-2403; 0000-0003-1683-3157; 0000-0003-1622-2399)
Recebido em 06/04/2021; Aceito em 12/07/2021; Publicado em 19/07/2021.
ABSTRACT:
Pterocarpus angolensis
DC and
Bobgunnia madagascariensis
(Desv.) J. H. Kirkbr. & Wiersema are two
hardwood species found in Miombo woodland. Crown size, being closely related to the photosynthetic capacity
of a tree, is an important parameter in studies of the growth of individual trees. In this sense, the present study
aimed to study the morphometric relationships of
P. angolensis
and
B. madagascariensis
as a resource to describe
the
morphometric
features
of
these
species.
Data
were
sampled
in
60
rectangular
plots
of
20
x
50
m,
systematically distributed within the forest. In each plot, the diameter at breast height (DBH), height (h), crown
insertion point (cih) and four crown radii of all trees with DBH ≥ 10 cm were measured. Results indicated that
crown diameter and crown length of
P. angolensis
grow as DBH and height increase, the larger the crown, the
greater
the
trees
dimensions;
as
for
B.
madagascariensis,
crown
features
have
shown
low
correlation
when
considering DBH. It was concluded that crown features influence on tree growth and are important measures
of
description
and
planning
of
silvicultural
activities
to
be
performed
in
natural
forests.
The
results
are
of
interest to forest managers since they make decisions about silvicultural operations.
Keywords:
crown dimensions; prediction models; umbila; pau-ferro; forest management.
Morfometria da copa para duas espécies madeireiras comerciais da floresta
de Miombo em Moçambique
RESUMO:
Pterocarpus
angolensis
DC
e
Bobgunnia
madagascariensis
(Desv.)
J.
H.
Kirkbr.
&
Wiersema
são
duas
espécies
de
madeira
de
lei
encontradas
na
floresta
de
Miombo.
O
tamanho
da
copa,
está
intimamente
relacionado
à
capacidade
fotossintética
de
uma
árvore,
e
é
um
parâmetro
importante
nos
estudos
do
crescimento de árvores individuais. Nesse sentido, o presente estudo teve como objetivo estudar as relações
morfométricas de
P. angolensis
e
B. madagascariensis
como recurso para descrever as características morfométricas
dessas
espécies.
Os
dados
foram
obtidos
em
60
parcelas
retangulares
de
20
x
50
m,
distribuídas
sistematicamente na floresta. Em cada parcela, foram medidos o diâmetro à altura do peito (DAP), altura (h),
altura de inserção da copa (hic) e quatro raios da copa de todas as árvores com DAP ≥ 10 cm. Os resultados
indicaram que o diâmetro e o comprimento da copa de
P. angolensis
crescem com o aumento do DAP e da
altura; quanto maior a copa, maior dimensão das árvores, enquanto que para
B. madagascariensis, as características
da
copa
mostraram
baixa
correlação
ao
considerar
o
DAP.
Concluiu-se
que
as
características
da
copa
influenciaram no crescimento das árvores e são importantes medidas de descrição e planejamento das atividades
silviculturais a serem realizadas na floresta. Estes resultados são de interesse dos manejadores florestais, pois
são eles que tomam decisões sobre as operações silviculturais.
Palavras-chave:
dimensões da copa; modelos preditivos; umbila; pau-ferro; manejo florestal.
1. INTRODUCTION
Pterocarpus angolensis DC (known as Umbila) and Bobgunnia
madagascariensis (Desv.) J. H. Kirkbr. & Wiersema (known as
Pau-ferro) are deciduous trees species of the Fabaceae family
found in Dry tropical forests in Southern and Eastern Africa,
including Miombo woodland (VAN WIK; VAN WIK,
2011). Miombo woodland is a vast African Dryland Forest
ecosystem covering close to 2.7 million km2 across Angola,
Democratic Republic of the Congo, Malawi, Mozambique,
Tanzania, Zambia and Zimbabwe. The Miombo woodland is
dominated by trees of the genera Brachystegia, Julbernardia and
Isoberlinia, in association with others species (CAMPBELL et
al., 2008). The woodland plays a crucial role in formal and
informal economies, supporting the livelihoods of millions of
rural and urban people, by providing important resources
such as timber, food, medicines, also play an important role
in the ecosystem dynamics, particularly with respect to
biodiversity, water, carbon and energy balance (KALABA et
al., 2014; RYAN et al., 2016).
In Mozambique, forestry is one of the 10 largest
industries in the country and accounted for a significants
Hofiço et al.
Nativa, Sinop, v. 9, n. 3, p. 318-326, mai./jun. 2021.
319
share of annual exports. For example, in 2019 the overall
forest sector accounted for approximately $570 million to the
gross domestic product (WORLD BANK, 2020). Despite
the large number of valuable tree species in Mozambique,
two species – P. angolensis and B. madagascariensis, represented
the bulk (44%) of timber harvest between 1999 and 2014, and
despite strict national-level Regulation of harvest, many are
concerned that harvest may be occurring in an unsustainable
manner (EGAS et al., 2013; MITADER, 2018).
Recently (March 2018), as a result of massive illegal
logging and exports the Government of Mozambique has
banned the harvest of two out of the six most exploited
timber species (e.g., Combretum imberbe and Bobgunnia
madagascariensis) and the export of Afzelia quanzensis, Millettia
stuhlmannii and Pterocarpus angolensis and has suspended the
development of new timber concession areas (REMANE;
THERRELL, 2019). Even with reforms in the forestry
sector, there remains doubt regarding strategies that could
allow interventions of sustainable management and ways to
optimize timber production in forests and raised the need for
their conservation.
Despite the economic value of these species, relatively
little research has focused on determining appropriate,
biological-based crown variables and morphometric features
schemes to help ensure that it is growth (including biomass),
productive potential of several native species in Mozambique
and make decisions about silvicultural operations
(GELDENHYUS, 2005; HOFIÇO et al., 2018; MITADER,
2018). The current demand for timber from these species in
the country, creates a need for tools for specific
measurements that support the management and use of the
existing stock.
A detailed investigation about crown features can
contribute to understanding the management of ecosystem
features such as forest productivity, biodiversity, and wildlife
habitats (WEISKITTELL et al., 2011). Thus, in order to
manage native forest species, it is necessary to know the
characteristics of tree dynamics throughout time, what
requires the description of morphometric relationships of
species to optimize silvicultural techniques (SEIFERT et al.,
2014; HESS et al., 2016).
Understanding morphometric relationships allows to
provide information about features of the adjustment of
crown morphology caused by competition for environmental
resources in forest communities (SEIFERT et al., 2014;
HESS et al., 2016), and studies about crown features (size and
architecture) are fundamental to model tree growth
(PRETZSCH, 2009). Modelling factors that influence on tree
growth, reflected on the variation of size and shape, allow to
establish strategies for the management of forest resources
(WEISKITTELL et al., 2011).
Considering individual trees, it allows to infer about each
one specifically by applying directly in forests and
populations of different ages, in trees of distinct social
positions because it mainly provides information about the
suitable living space according to tree size (SEIFERT et al.,
2014). Thus, size, structure, shape, and distribution of crowns
are intimately related to tree growth, growth strength and
productivity (GONZALEZ-BENECKE et al., 2014),
volume and biomass (MATE et al., 2014; JUCKER et al.,
2016), as well as wood quality, branch diameter, length of
growth ring, trunk conicity, knot features, core and sapwood
proportion (GONZALEZ-BENECKE et al., 2014; VON
HOLSBEECK et al., 2016).
Moreover, crown dimensions reflect the competition the
tree was subject to during its past growth (RUSSELL et al.,
2014, FU et al., 2017), this being relevant information for the
forester.
Models
that
describe
growth
regarding
individual
trees are usually
based on diameter at breast height, crown
length and its interactions with dendrometric variables, with
emphasis
on
the
morphometric
indexes
such
as
h/DBH
relationship,
crown
proportion,
salience
index,
coverage
index and formal of crown (COSTA et al., 2016; HESS et al.,
2016).
In light of this, the present study aimed to investigate the
dimensional
relationships
of
P.
angolensis
and
B.
madagascariensis
as
a
resource
for
the
description
of
morphometric
features
of
these
species
in
a
Miombo
woodland in Mozambique. The proposed model can be used
for
predictions
of
crown
morphometry
involving
these
important
species
and
provide
resources
for
the
country’s
management
plans
and
make
decisions
about
silvicultural
operations.
2. MATERIAL AND METHODS
2.1. Study area
The
study
was
performed
in
a
forest
concession
that
managed
by
Sotomane
Construction
and
Industry
Lda
(16°33'S
and
36°32'E,
16°49'S
and
36°47'E),
located
in
Mocuba District, Zambézia Province, in central Mozambique
(FIGURE
1).
The
main
activity
in
the
forest
concession
is
the
selective
cut
for
wood-producing
purposes.
However,
family subsistence agriculture is the predominant activity of
local
communities,
characterized
by
slash
and
burn
of
the
whole forest cover (clear cuts), resulting in annual fires and
degradation of these areas (HOFIÇO; FLEIG, 2015).
The
climate
in
the
region
is
Aw
(tropical
savanna)
according
to
the
Köppen
classification
system,
with
well-
defined seasons, dry winter from April to October, and wet
season from November to March. The annual mean rainfall
is
1200
mm
and
mean
temperature
is
24.3
ºC.
Soils
are
predominantly
red
argisoils
in
hydromorphic
conditions
(MAE, 2005). Topography is slightly undulated between 200
m and 400 m above sea level.
Figure 1. Study area in Mocuba District, Zambézia Province,
Mozambique.
Figura 1. Área de estudo no Distrito de Mocuba, Província
da Zambézia, Moçambique.
Crown morphometry for two valuable timber species from Miombo woodland in Mozambique
Nativa, Sinop, v. 9, n. 3, p. 318-326, mai./jun. 2021.
320
2.2. Description of studied species
The Miombo woodland covers an area of 26.9 million ha
in Mozambique and corresponds to 67% of its total forest
area, being the main source of hardwood in the country
(MITADER, 2018). P. angolensis is a medium to large-sized
tree, up to 16 m tall that can reach 28 m. It has a rectilinear
and uniform trunk, a robust round-shaped crown, with a
dark-brown core and yellow-greyish sapwood, wood is hard
and moderately heavy, relatively easy to handle (Figure 2a).
As for B. madagascariensis, it is a small-sized tree varying
between 4 and 16 m tall, with rectilinear uniform trunk and
dense, robust and round-shaped crown (Figure 2b), its wood
is hard and very heavy, hard to be handled, and it shows no
significant difference in colour between core and sapwood
(BUNSTER, 2006; MOJEREMANE; LUMBILE, 2016).
Figure 2. Typical growth forms of tree species in Miombo
woodland, in Mocuba District, Mozambique, dry season 2020. (a)
Pterocarpus angolensis; and (b) Bobgunnia madagascariensis.
Figura 2. Formas de crescimento típicas das duas espécies árboreas
na floresta de Miombo, no Distrito de Mocuba, Moçambique,
estação seca de 2020. (a) Pterocarpus angolensis; e (b) Bobgunnia
madagascariensis.
Due to their physico-mechanical features such as
durability, resistance, density and colour, B. madagascariensis
and P. angolensis are species of high commercial value used in
the construction, naval and furniture industry, as well as
vehicle bodies, railroad ties, wood floor and decks, and
beehives (BUNSTER, 2006; ALI et al., 2008). Additionally,
parts of these species are widely used in traditional medicine
to treat diseases such as malaria, cornea ulcer, mycosis, fever,
and syphilis (STEVENSON et al., 2010; MOIEREMANE;
LUMBILE, 2016).
2.3. Data acquisition
Data were obtained from 60 plots of 20 x 50 m (1000 m2)
systematically distributed within a forest concession, with a
distance of 50 m between plots, and 100 m between lines.
For each objective tree, dendrometric and morphometric
variables of all trees with DBH ≥ 10 cm were measured,
totaling 171 trees of P. angolensis and 115 trees of B.
madagascariensis, covering the full range of diameters. The
measured variables were diameter at breast height (DBH) at
1.3 m above ground; height (h), corresponding to the
distance between ground level and crown top; commercial
height (ch), corresponding to the trunk with commercial
value; and height from the crown insertion point (cih)
corresponding to the distance between ground level and the
beginning of living crown. DBH was measured with a
precision dendrometric caliper (cm), height (m) with the
Blume-Leiss tool, and four crown radii in the cardinal points
north, south, east, and west, with a measuring tape and
compass. Crown length (cl) was obtained with the difference
between h and cih, in the expression [cl = h – cih]. Crown
diameter (cd) was calculated in meters with the mean crown
radium (cr), in the expression [cd = cr × 2] obtained from
four radii.
2.4. Data analysis
Descriptive statistics characterized the measured
variables. The diametric distribution was determined with the
class range of 5 cm, with the lower limit of the first class at
10.0 cm, and 14.9 cm as upper limit. For the analysis of the
morphometric relationships, the variables used were crown
length (cl), crown diameter (cd), the h/DBH relationship, or
slenderness coefficient (SC), the cd/cl relationship, known as
formal of crown (FC), the cd/DBH relationship, or salience
index (SI), and the cd/h relationship, or coverage index (CI),
according to the methodology described by Roman et al.
(2009), Hess et al. (2016) and Costa et al. (2016). From the
sampled data, the mean, minimal and maximum values of the
morphometric variables and dimensional relationships of P.
angolensis and B. madagascariensis were obtained, as shown in
Table 1.
To describe the dimensional characteristics (h, cih, ch, cl,
cd) according to DBH, the biometric model 1 was adjusted
in the non-linear model:
y = β0.exp (β1/x) + εi (01)
where: y – dimensional variable: h; cih; ch; cl; cd; x – DBH
(diameter at breast height, measured at 1.30 m above ground,
in cm); β0, β1 – estimated regression coefficient; εi – residual
error.
And in order to describe the relationship of the
morphometric variables (SC, FC, SI, CI), the biometric
model was adjusted in the non-linear model:
y = β0.Xβ1 + εi (02)
where: y – dimensional variable: SC; FC; SI; CI; x – DBH
(diameter at breast height, measured at 1.30 m above ground,
in cm); β0, β1 – estimated regression coefficient; εi – residual
error.
All statistics were processed with the SAS software
version 9.1 (SAS Institute Inc. 2004). For the performance of
the model, the coefficient of determination (R2), root mean
squared error (RMSE), and the graphic distribution of
residues in percentage (Table 2). The dimensional variable by
DBH and morphometric relationship of P. angolensis and B.
madagascariensis was used to draw graphs in eight figures using
the Microsoft Excel (2019).
Hofiço et al.
Nativa, Sinop, v. 9, n. 3, p. 318-326, mai./jun. 2021.
321
Table 1. Biometric characteristics of Pterocarpus angolensis and Bobgunnia madagascariensis in Miombo woodland in Mocuba
District, Mozambique.
Tabela 1. Características biométricas de Pterocarpus angolensis e Bobgunnia madagascariensis na floresta de Miombo no Distrito de
Mocuba, Moçambique.
Variable Unit
Pterocarpus angolensis
Bobgunnia madagascariensis
Mean
–
SD
Range
Mean
–
SD
Range
DBH
cm
25.3 ± 12.9
10.0
-
6
6.7
19.4 ± 5.20
10.0
-
38.6
h
m
11.1 ± 3.10
5.60
-
17.6
11.0 ± 2.10
6.5
-
16.0
cih
m
5.70 ± 1.60
2.60
-
8.80
4.10 ± 1.00
2.00
-
6.0
ch
m
4.50 ± 0.90
1.50
-
7.80
4.50 ± 1.20
2.00
-
7.0
cl
m
5.40 ± 1.70
2.50
-
10.5
6.90 ± 2.00
2.00
-
12.0
cd
m
6.70 ± 1.30
3.80
-
9.30
2.00 ± 0.50
0.80
-
3.6
SC
-
0.48 ± 0.10
0.26
-
0.72
0.58 ± 0.12
0.31
-
0.90
FC
-
2.61 ±
0.51
1.69
-
4.20
0.64 ± 0.29
0.21
-
2.20
SI
-
61.0 ± 17.4
27.6
-
103.9
21.4 ± 5.60
7.70
-
36.0
CI
-
1.24 ± 0.18
0.95
-
1.81
0.36 ± 0.09
0.17
-
0.63
where: SD – standard deviation; DBH – diameter at breast height, measured at 1.30 m above ground (cm); h – total height
(m); cih – height from the crown insertion point (m); ch – commercial height (m); cl – crown length (m); cd – crown diameter
(m); SC (slenderness coefficient) – h/DBH; FC (formal of crown) – cd/cl; SI (salience index) – cd/DBH; CI (coverage index)
– cd/h.
Table 2. Statistic criteria used to evaluate the adjusted models.
Tabela 2. Critérios estatísticos usados para avaliar os modelos
ajustados.
Statistical
criteria Expression
Coefficient of
determination
(3)
R
=
1
−
∑
Y
−
Y
∑
(
Y
−
Y
)
(Root Mean
Square Error
(4)
RMSE
=
(
n
−
p
)
(
Y
−
Y
)
Residual value
(%) (5)
Residual
value
(
%
)
=
Y
−
Y
Y
.
100
Where: Yi – observed variable; Y
– estimated variable; Y
–
mean observed variable; n – number of observations; p –
number of estimated coefficients.
3. RESULTS
3.1. Population structure
The studied population of P. angolensis showed a typically
decreasing diameter distribution, with trees up to the class of
67.5 cm. B. madagascariensis also showed a decreasing
distribution, with a smaller number of trees in the first class,
probably resulting from the already established lack of natural
regeneration, what can lead to population decrease
throughout time (Figure 3). In the sample, 171 P. angolensis
(10.0 ≤ DBH ≤ 66.7 cm) and 115 B. madagascariensis (10.0 ≤
DBH ≤ 38.6 cm) were measured in 6 ha, corresponding to
28.5 and 19.2 trees.ha-1, respectively.
3.2. Morphometric relationship
The mean height for the two species was ≈ 11.0 m, with
a similar height range for both P. angolensis (5.6 m and 17.6 m)
and B. madagascariensis (6.5 m and 16.0 m). The measured
values of crown diameter varied between 3.80 ≤ cd ≤ 9.30
for P. angolensis, and 0.80 ≤ cd ≤ 3.6 for B. madagascariensis.
DBH also showed an expressive difference between the two
species, being 10.0 ≤ DBH ≤ 66.7 cm and 10.0 ≤ DBH ≤
38.6 cm, respectively, for P. angolensis and B. madagascariensis.
The other measured variables showed homogeneous
dimensions. The biometric model showed a specific
performance for each morphometric variable assessed as
dependent variable for P. angolensis and B. madagascariensis
(Table 3).
All P. angolensis regressions that describe the
morphometric variables according to DBH as well as the
regression coefficient (for α = 5%) were significant. The
lowest expression of the R2 coefficient was 0.13 in the ch
relationship, indicating the low adjusted in cl the increase of
tree diameter, also confirmed by the RMSE of 0.86 m. The
relationships of FC with R2 = 0.34 and CI with R2 = 0.35,
confirmed the lower dependence to DBH. The adjusted
regressions for the other variables had R2 values higher than
0.80 and significant coefficients.
Figure 3. Diameter distribution of Pterocarpus angolensis (grey
pillar) and Bobgunnia madagascariensis (black pillar) in Mocuba
District, Mozambique.
Figura 3. Distribuição diamétrica de Pterocarpus angolensis (pilar
cinza) e Bobgunnia madagascariensis (pilar preto) no Distrito de
Mocuba, Moçambique.
0
5
10
15
20
25
30
35
40
45
50
12,5 17,5 22,5 27,5 32,5 37,5 42,5 47,5 52,5 57,5 62,5 67,5
Density (n/ha)
Diameter class (cm)
P. angolensis
B. madagascariensis
Crown morphometry for two valuable timber species from Miombo woodland in Mozambique
Nativa, Sinop, v. 9, n. 3, p. 318-326, mai./jun. 2021.
322
The evaluated for B. madagascariensis showed similar
results for the variables FC and CI with a non-significant
regression coefficient (β1), indicating that there is no trend
data for the assessed equations. Though the morphometry of
P. angolensis and B. madagascariensis was adjusted with distinct
accuracy, the biometric model allowed to precisely describe
the mean development of morphometric variables of the two
species. The graphs in Figure 4, evidence the variables cd and
cih as the ones with the highest difference between species,
affecting the other morphometric indexes that contain these
variables.
Table 3. Estimated regression coefficients and statistics of adjustment and precision of the dimensional variables of Pterocarpus
angolensis and Bobgunnia madagascariensis, in Miombo woodland in Mocuba District, Mozambique.
Tabela 3. Coeficientes de regressão estimados e estatísticas de ajuste e precisão das variáveis dimensionais de Pterocarpus
angolensis e Bobgunnia madagascariensis, na floresta de Miombo no Distrito de Mocuba, Moçambique.
Variables
Species
n
β
0
β
1
F value
p
value > F
R²
RMSE
h
Pterocarpus angolensis
171
203
.
631
-
129
.
856
19426.1 <0.0001 0.94 0.76
(<0.
0001)
(<0.0001)
cih
99
.
362
-
117
.
056
7453.71 <0.0001 0.83 0.63
(<0.0001)
(<0.0001)
ch
5.284
-
3.472
2170.16 <0.0001 0.13 0.89
(<0.0001)
(<0.0001)
cl
9.998
-
8.429
17000.8 <0.0001 0.87 0.86
(<0.0001)
(<0.0001)
cd
10.477
-
14.409
5929.56 <0.0001 0.85 0.67
(<0.0001)
(<0.0001)
SC
167.379
-
0.402
11703.8 <0.0001 0.83 4.24
(<0.0001)
(<0.0001)
FC
5.429
-
0.237
3405.19 <0.0001 0.34 0.42
(<0.0001)
(<0.0001)
SI
330.491
-
0.553
7964.05 <0.0001 0.86 6.54
(<0.0001)
(<0.0001)
CI
2.190
-
0.184
5923.58 <0.0001 0.35 0.15
(<0.0001)
(<0.0001)
h
Bobgunnia madagascariensis
115
17.165
-
8.201
2452.08 <0.0001 0.36 1.69
(<0.0001)
(<0.0001)
cih
5.270
-
4.598
957.65 <0.0001 0.07 1.01
(<0.0001)
(<0.006)
ch
7.532
-
9.461
1111.61 <0.0001 0.25 1.03
(<0.0001)
(<0.006)
cl
2.866
-
6.729
1355.75 <0.0001 0.18 0.41
(<0.0001)
(<0.0001)
cd
12.199
-
10.549
887.67 <0.0001 0.24 1.77
(<0.0001)
(<0.0001)
SC
274.6
-
0.529
2367.21 <0.0001 0.45 9.27
(<0.0001)
(<0.0001)
FC
1.117
-
0.190
276.58 <0.0001 0.01 0.29
(<0.0375)
(<0.2451)
SI
118.173
-
0.587
1413.26 <0.0001 0.37 4.37
(<0.0001)
(<0.0001)
CI
0.463
-
0.078
1002.74 <0.0001 0.01 0.09
(<0.0001)
(<0.3653)
where: n – number of measured trees in the 6.0 ha sampled; h – total height, in m; cih – crown insertion height, in m; ch –
commercial height, in m; DBH – diameter at breast height, in cm; cl – crown length, in m; cd – crown diameter, in m; SC
(slenderness coefficient) – h/DBH; FC (formal of crown) – cd/cl; SI (salience index) – cd/DBH; CI (coverage index) – cd/h;
β0, β1 – estimated regression coefficients; R2 – coefficient of determination; RMSE – root mean squared error; p value > F –
probability value of the F-test; ( ) – probability value of t-test for estimated regression coefficients.
4. DISCUSSION
The negative exponential diametric distribution (Figure 3)
for P. angolensis suggests that the natural regeneration process
and the continued survival of the species in the forest are
ensured (CARO et al., 2005; DE CAUWER et al., 2014;
VAN HOLSBEECK et al., 2016; HOFIÇO et al., 2018).
According to Caro et al. (2005), this behaviour is due to the
fact that the species is adapted to survive and tolerate severe
environmental conditions such as fires and droughts.
Nevertheless, the unimodal diametric distribution of B.
madagascariensis can indicate the critical absence of natural
regeneration or plant mortality due to anthropic action,
which is recurrent in the region, as reported by Williams et al.
(2008) and Ryan; Williams (2011), in woodland recovery
during Miombo regeneration in Central Mozambique.
Hofiço et al.
Nativa, Sinop, v. 9, n. 3, p. 318-326, mai./jun. 2021.
323
Figure 4. Adjusted regressions lines according to the dimensional variables for Pterocarpus angolensis (solid line) and Bobgunnia
madagascariensis (dotted line) trees in Miombo woodland in Mocuba District, Mozambique.
Figura 4. Linhas de regressões ajustadas de acordo com as variáveis dimensionais para árvores de Pterocarpus angolensis (linha
contínua) e Bobgunnia madagascariensis (linha pontilhada) na floresta de Miombo no Distrito de Mocuba, Moçambique.
In addition to the anthropic action in the area, there is the
hypothesis that it occurs due to fires, which eliminate a
considerable number of regenerating trees when it goes
beyond human control, altering the structure of specific
populations in the Miombo ecosystem (WILLIAMS et al.,
2008; CHIDUMAYO, 2013; RIBEIRO et al., 2017). This
fact is integrated with studies in the Miombo ecosystem, in
which the negative influence of fires and the anthropic
disturbances in species ecological process – including natural
regeneration – are reported (CARO et al.; 2005; WILLIAMS
0
4
8
12
16
20
24
0 10 20 30 40 50 60 70 80
h (m)
DBH (cm)
(a)
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70 80
cih (m)
DBH (cm)
(b)
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70 80
cl (m)
DBH (cm)
(c)
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70 80
cd (m)
DBH (cm)
(d)
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80
SC
DBH (cm)
(e)
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
0 10 20 30 40 50 60 70 80
FC
DBH (cm)
(f)
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80
SI
DBH (cm)
(g)
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
0 10 20 30 40 50 60 70 80
CI
DBH (cm)
(h)
Crown morphometry for two valuable timber species from Miombo woodland in Mozambique
Nativa, Sinop, v. 9, n. 3, p. 318-326, mai./jun. 2021.
324
et al., 2008; SYAMPUNGANI et al., 2016). In the specific
case of P. angolensis, it is possible to affirm that there still is
anthropic action for wood extraction in the study site.
Heights had a great significance in the understanding of
the features of these two species, which showed a high
structural complexity, reflected in the low R2 values of the
equations developed for the analysed morphometric
variables of B. madagascariensis. Sampled B. madagascariensis
trees were relatively young, with low variability of the
analysed dimensional characteristics.
These differences can be explained by the phenotypical
resilience of tree response to climate and other
environmental conditions such as altitude and soil features
(KALABA et al., 2013; SEIFERT et al., 2014), as well as the
action of fires, observed in the woodland, in which some
trees of B. madagascariensis had their trunks and crowns
damaged. It is important to mention that both B.
madagascariensis and P. angolensis are species of the same forest
formation and belong to the same family (Fabaceae) but to
different ecological groups: the first is a late-climax secondary
species whereas the latter is a pioneer species
(GONÇALVES et al., 2017; CHITECULO; SUROVY
2018), in other words, ecological strategies are different to
obtain better results for species growth and survival
(WILLIAMS et al., 2008; CHIDUMAYO, 2013). Chidumayo
(2019) report different strategies of trees in the Miombo
canopy where he found that most pioneer species grow
slower in the initial stages.
Crown length (cl) increased with DBH for both species
(Figure 3c), and B. madagascariensis was higher than P.
angolensis. This fact can be B. madagascariensis explained by the
shape of some B. madagascariensis trees observed in the studied
forest, which had multiple high stems and sparse crown,
contrary to the common feature of trees in the Miombo
woodland, which typically have flat and round umbel-shaped
crowns like P. angolensis (MATE et al., 2014; DE CAUWER
et al., 2014). Feldpausch et al. (2011) observed that the apical
growth speed of leafy species is higher for some species than
the mortality of branches in the crown basis, what results in
a higher crown proportion, being this variable an indicator of
tree vitality as well as an indicator of degree of competition.
The same increase was verified for crown diameter in
which P. angolensis and B. madagascariensis varied between 3.8
and 9.3 m, and 0.8 and 3.6 m, respectively (Table 1). It was
noted that B. madagascariensis showed a slight reduction in the
increase rate of crown diameter in higher DBH classes
(Figure 4d), what can indicate that a smaller space is needed
for side growth, consequently displaying a smaller area of
crown projection (ROMAN et al., 2009; SYAMPUNGANI
et al., 2016; HESS et al., 2016). P. angolensis showed an
increase in insertion height crown and crown diameter as
trees grew in diameter (Figure 4b and 4d). The high variability
in the dimensions of the crown can be related to the different
degrees of competition to which the tree is subjected
(SEIFERT et al., 2014; HESS et al., 2021).
However, this aspect, in the present work, is conflicting,
since the trees of P. angolensis and B. madagascariensis have little
influence from competition (MUGASHA et al., 2013; DE
CAUWER et al., 2014; MATE et al., 2015), as competition
becomes relevant only when there is light restriction
(PRETZSCH, 2009; ROMAN et al., 2009). Mugasha et al.
(2013) reported that as crowns grow their height increases,
and crowns are wider and need more space for growth, what
justifies the crown dimensions and tree height relationship.
Trees with large and healthy crowns are related to higher
growth rates as a result of the increase in the photosynthesis
rate (VON HOLSBEECK et al., 2016; FU et al., 2017).
Taking the slenderness coefficient (h/DBH) into
consideration, B. madagascariensis showed higher values than
P. angolensis (Table 1; Figure 4e). However, this feature tends
to decrease as DBH increases, indicating a higher stability of
trees, provided by the smaller DBH/total tree height
relationship, regardless of age (FELDPAUSCH et al., 2011;
MUGASHA et al., 2013). The decrease of the slenderness
coefficient is a positive physiological factor for stability since
trees with very high stems and small diameters are more
unstable, specially under the action of wind, which is
impossible to be controlled (MUGASHA et al., 2013;
SEIFERT et al., 2014) and can cause irreversible damage
such as crown breakage or tree fall (GONZALEZ-
BENECKE et al., 2014).
The FC with mean value of 2.61 for P. angolensis (Table 1)
indicates large crowns distinctive of the species, which has
ellipsoidal, flat or umbel-shaped crowns according to De
Cauwer et al. (2014). B. madagascariensis showed mean FC of
0.64, with slender and sparse crowns. The SI which expresses
how larger the crown diameter is than the DBH
(MUGASHA et al., 2013; HESS et al., 2021), was 61.0 for P.
angolensis¸ in other words, the crown diameter is 61 times
larger than the DBH – and 21.4 for B. madagascariensis (Table
1, Figure 4g).
A lower value of the SI means that the tree has a
proportionally higher crown surface area, making a more
efficient use of space, thus considering a given crown
projection area. Therefore, as trees grow within the forest,
this index can be used as a thinning indicator, establishing the
space to be cleared (GETZIN et al., 2011; GONZALEZ-
BENECKE et al., 2014).
The variable of the CI can also be used for species
management as it indicates the necessary space for the target
height (JUCKER et al., 2015; HESS et al., 2016). The mean
value for P. angolensis and B. madagascariensis was 1.24 and 0.36,
respectively (Table 1). This index showed an almost
curvilinear tendency as trees grew in height, as demonstrated
by this study (Figure 4h). This trend is a result of the small
increase of crown diameter with the increase of height in the
sampled classes, although no increase in height was observed.
The higher the value for this index, evidences that their
growth is larger in height than in DBH (FELDPAUSCH et
al., 2011).
We believe that for these activities to be successful,
growth data for valuable timber species such as those
presented in this study need to be widely available and we
hope this information can help inform the sustainable
management of timber in Mozambique.
5. CONCLUSIONS
There are significant and statistically precise relationships
for interdimensional and morphometric features of P.
angolensis, where crown diameter and crown length increase as
DBH and height increase, the larger the crown, the larger the
species growth, except for B. madagascariensis, whose crown
features were little related to DBH.
The high variability of canopy diameters probably occurs
due to the specific and adverse environmental conditions that
influence the growth of the species, confirming the resilience
characteristic of the same, high adaptation capacity. Crown
Hofiço et al.
Nativa, Sinop, v. 9, n. 3, p. 318-326, mai./jun. 2021.
325
features are the main factors that influence tree growth and
timber quality, and they are important information for forest
management measures, due to the simplicity and practicality
of application in natural forests.
This study can contribute through silvicultural
interventions that result in better increment rates and native
species growth in the context of management of individual
tree and conservation of species in a natural forest. The
results are relevant to conservation and sustainable
management for P. angolensis and B. madagascariensis trees in
central of Mozambique.
6. ACKNOWLEDGMENTS
We thank Sotomane concession staff and colleagues from
the Department of Forest Engineering at UniZambeze for
their support. Special thanks are due to Mr. Jaime Macuacua,
Marchante Assura and Miguel da Costa for important
contributions during the execution of this work. This
research was supported by the National Research Fund of
Mozambique (FNI: Project_12B/2018).
7. REFERENCES
ALI, A. C.; UETIMANE JUNIOR, E.; LHATE, I. A.;
TERZIEV, N. Anatomical characteristics, properties
and use of traditionally used and lesser-known wood
species from Mozambique: a literature review. Wood
Science and Technology, New York, v. 2, n. 6, p.
453-472, 2008. DOI: https://doi.org/10.1007/s00226-
008-0186-5
BUNSTER, J. Commercial timbers of Mozambique:
Technological Catalogue. Traforest Lda, Maputo,
Mozambique. 2006. 63p.
CAMPBELL, B.; ANGELSEN, A.; CUNNINGHAM, A.;
KATERERE, Y.; SITOE, A.; WUNDER, S. Miombo
woodlands: Opportunities and barriers to
sustainable forest management. Centre for
International Forestry Research (CIFOR), Bogor,
Indonesia. 2008. 41p.
CARO, T. M.; SUNGULA, M.; SCHWARTZ, M. W.;
BELLA, E. M. Recruitment of Pterocarpus angolensis in
the wild. Forest Ecology and Management,
Amsterdam, v. 219, n. 2-3, p. 69–175, 2005. DOI:
https://doi.org/10.1016/j.foreco.2005.07.004
CHIDUMAYO, E. N. Forest degradation and recovery in a
Miombo woodland landscape in Zambia: 22 years of
observations on permanent sample plots. Forest
Ecology and Management, Amsterdam, v. 291, p. 154-
161, 2013. DOI:
https://doi.org/10.1016/j.foreco.2012.11.031
CHIDUMAYO, E. N. Management implications of tree
growth patterns in Miombo woodlands of Zambia.
Forest Ecology and Management, Amsterdam, v. 436,
n. 1, p. 105-116, 2019. DOI:
https://doi.org/10.1016/j.foreco.2019.01.018
CHITECULO, V.; SUROVY, P. Dynamic Patterns of trees
species in Miombo Forest and management perspectives
for sustainable production - case study in Huambo
Province, Angola. Forests, Basel, v. 9, n. 6, p. 321, 2018.
DOI: https://doi.org/10.3390/f9060321
COSTA, E. A.; FINGER, C. A. G.; FLEIG, F. D. Influência
da posição social nas relações morfométricas de
Araucaria angustifolia. Ciência Florestal, Santa Maria, v.
26, n. 1, p. 225-234, 2016. DOI:
http://dx.doi.org/10.5380/rf.v47i4.49667
DE CAUWER, V.; MUYS, B.; REVERMANN, R.;
TRABUCCO, A. Potential, realised, future distribution
and environmental suitability for Pterocarpus angolensis
DC in southern Africa. Forest Ecology and
Management, Amsterdam, v.315, n. 1, p. 211-226, 2014.
DOI: https://doi.org/10.1016/j.foreco.2013.12.032
EGAS, A. Assessment of harvested volume and illegal
logging in Mozambican natural forests. Faculty of
Agronomy and Forest Engineering, Eduardo Mondlane
University. Maputo, Moçambique. 2013. 176p.
FELDPAUSCH, T. et al. Height-diameter allometry of
tropical forest trees. Biogeosciences, Hoboken, v. 8, p.
1081-1106, 2011. DOI: https://doi.org/10.5194/bg-8-
1081-2011
GELDENHUYS, C. J. Basic guidelines for silvicultural
and management practices in Mozambique. Report
FW-04/05, Forestwood, Pretoria, 2005. 78p.
GETZIN, S.; WORBES, M.; WIEGAND, T.; WIEGAND,
K. Size dominance regulates tree spacing more than
competition within height classes in tropical Cameroon.
Journal of Tropical Ecology, Cambridge, v. 27, n. 1, p.
93-102, 2011. DOI:
https://doi.org/10.1017/S0266467410000453
GONÇALVES, F. M. P.; REVERMANN, R.; GOMES, A.
L.; AIDAR, M. P. M.; FINCKH, M.; JUERGENS, N.
Tree species diversity and composition of Miombo
woodlands in South-Central Angola: A chronosequence
of forest recovery after shifting cultivation.
International Journal of Forestry Research, London,
v. 2017, n. 1, p. 1-13, 2017. DOI:
https://doi.org/10.1155/2017/6202093
GONZALEZ-BENECKE, C. A.; GEZAN, S. A.;
SAMUELSON, L. J.; CROPPER Jr., W. P.; LEDUC, D.
J.; MARTIN, T. A. Estimating Pinus palustris tree
diameter and stem volume from tree height, crown area
and stand-level parameters. Journal of Forest Research,
v. 25, n. 1, p. 43–52, 2014. DOI:
https://doi.org/10.1007/s11676-014-0427-4
HESS, A. F.; MINATTI, M.; COSTA, E. A.; SCHORR, L.
P. B.; ROSA, G. T. da; SOUZA, I. de A.; BORSOI, G.
A.; LIESENBERG, V.; STEPKA, T. F.; ABATTI, R.
Height-to-diameter ratios with temporal and
dendro/morphometric variables for Brazilian pine in
south Brazil. Journal of Forestry Research, v. 32, p.
191–202, 2021. DOI: https://doi.org/10.1007/s11676-
019-01084-8
HESS, A. F.; LOIOLA, T.; SOUZA, I. A. de;
NASCIMENTO, B. Morphometry of the crown of
Araucaria angustifolia in natural sites in southern Brazil.
Bosque, Valdivia, v. 37, n. 3, p. 603-611, 2016. DOI:
http://dx.doi.org/10.4067/S0717-92002016000300017
HOFIÇO, N. S. A.; COSTA, E. A.; FLEIG, F. D.;
NANVONAMUQUITXO, S. J. A. Regulation of the
diametric structure of the Miombo woodland using the
De Liocourt method in Mozambique. Nativa, Sinop, v.
6, n. 4, p. 407-414, 2018. DOI:
http://dx.doi.org/10.31413/nativa.v6i4.5396
HOFIÇO, N. S. A.; FLEIG, F. D. Diversity and structure of
Miombo woodlands in Mozambique using a range of
sampling sizes. Journal of Agricultural Science and
Technology, Tarbiat, v. 5, n. 10, p. 679-690, 2015. DOI:
10.17265/2161-6264/2015.10.005
Crown morphometry for two valuable timber species from Miombo woodland in Mozambique
Nativa, Sinop, v. 9, n. 3, p. 318-326, mai./jun. 2021.
326
JUCKER, T.; BOURIAUD, O.; COOMES, D. A. Crown
plasticity enables trees to optimize canopy packing in
mixed-species forests. Functional Ecology, Oxford, v.
29, p. 1078-1086, 2015. DOI:
https://doi.org/10.1111/1365-2435.12428
KALABA, F. K.; QUINN, C. H.; DOUGILL, A. J.; VINYA,
R. Floristic composition, species diversity and carbon
storage in charcoal and agriculture fallows and
management implications in Miombo woodlands of
Zambia. Forest Ecology and Management,
Amsterdam, v. 304, p. 99–109, 2013. DOI:
https://doi.org/10.1016/j.foreco.2013.04.024
KALABA, F. K.; QUINN, C. H.; DOUGILL, A. J. The role
of forest provisioning ecosystem services in coping with
household stresses and shocks in Miombo woodlands,
Zambia. Ecosystem Services, v. 5, p. 143-148, 2014.
DOI: https://doi.org/10.1016/j.ecoser.2013.07.008
MAE. Perfil do distrito de Mocuba. Província da
Zambézia. Ministério da Administração Estatal. Série
Perfis Distritais, Maputo, Mozambique. 2005. 50p.
MALMER, A. General ecological features of Miombo
woodlands and considerations for utilization and
management. p. 34-42. 2007. (Working Papers of the
Finnish Forest Research Institute, v. 50).
MATE, R.; JOHANSSON, T.; SITOE, A. Biomass
equations for tropical forest tree species in Mozambique.
Forests, Basel, v. 5, p. 535-556, 2014. DOI:
https://doi.org/10.3390/f5030535
MATE, R.; JOHANSSON, T.; SITOE, A. Stem Volume
Equations for Valuable Timber Species in Mozambique.
Journal of Sustainable Forestry, v. 34, n. 8, p. 787-806,
2015. DOI:
http://dx.doi.org/10.1080/10549811.2015.1039043
MITADER. Inventário Florestal Nacional. Ministry of
Land, Environment and Rural Development, Maputo,
Mozambique. 2018. 118p.
MOJEREMANE, W.; LUMBILE, A. U. A review of
Pterocarpus angolensis DC. (Mukwa) an important and
threatened timber species of the Miombo
woodlands. Research Journal of Forestry, v. 10, n. 1, p.
8-14, 2016. DOI: https://doi.org/10.3923/rjf.2016.8.14
MUGASHA, W. A.; BOLLANDSÅS, O. M.; EID, T.
Relationships between diameter and height of trees in
natural tropical forest in Tanzania. Southern Forests: a
Journal of Forest Science, Makhanda, v. 75, n. 4, v. 221-
237, 2013. DOI:
https://doi.org/10.2989/20702620.2013.824672
PRETZSCH, H. Forest dynamics, growth and yield.
Heidelberg: Springer Verlag Berlin. Germany, 2009.
664p.
REMANE, I. A. D.; THERRELL, M. D. Tree-ring analysis
for sustainable harvest of Millettia stuhlmannii in
Mozambique. South African Journal of Botany,
Pretoria, v. 125, p. 120-125, 2019. DOI:
https://doi.org/10.1016/j.sajb.2019.07.012
RIBEIRO, N. S.; CANGELA, A.; CHAUQUE, A.;
BANDEIRA, R. R.; RIBEIRO-BRROS, A. I.
Characterisation of spatial and temporal distribution of
the fire regime in Niassa National Reserve, northern
Mozambique. International Journal of Wildland Fire,
Rosyn, v. 26, n. 12, p. 1021–1029, 2017. DOI:
https://doi.org/10.1071/WF17085
ROMAN, M.; BRESSAN, D. A.; DURLO, M. A. Variáveis
morfométricas e relações interdimensionais para Cordia
trichotoma (Vell.) Arráb. ex Steud. Ciência Florestal,
Santa Maria, v. 19, n. 4, p. 473-480, 2009. DOI:
http://dx.doi.org/10.5902/19805098901
RYAN, C. M.; PRITCHARD, R.; McNICOL, I.; OWEN,
M.; FISHER, J. A.; LEHMANN, C. Ecosystem services
from southern African woodlands and their future under
global change. Philosophical Transaction B, London,
v. 371, ID 20150312, 2016. DOI:
https://doi.org/10.1098/rstb.2015.0312
RYAN, C. M.; WILLIAMS, M. How does fire intensity and
frequency affect Miombo woodland tree populations and
biomass? Ecological applications, Washington, v. 21,
n. 1, p. 48–60, 2011. DOI: https://doi.org/10.1890/09-
1489.1
SEIFERT, T.; SEIFERT, S.; SEYDACK, A.; DURRHEIM.
G.; GADOW, K. V. Competition effects in an
Afrotemperate forest. Forest Ecosystems, New York,
v. 1, n. 13, p. 1-15, 2014. DOI:
https://doi.org/10.1186/s40663-014-0013-4
SHIRIMA, D.; TOTLAND, O.; MUNISHI, P. K. T.; MOE,
S. R. Does the abundance of dominant trees affect
diversity of a widespread tropical woodland ecosystem in
Tanzania? Journal of Tropical Ecology, Cambridge, v.
31, n. 4, P. 345-359, 2015. DOI:
https://doi.org/10.1017/S0266467415000231
STEVENSON, P. C.; NYIRENDA, S. P.; VEITCH, N. C.
Highly glycosylated flavonoids from the pods of
Bobgunnia madagascariensis. Tetrahedron Letters,
Elmsford, v. 51, n. 36, p. 4727-4730, 2010. DOI:
https://doi.org/10.1016/j.tetlet.2010.07.013
SYAMPUNGANI, S.; GELDENHUYS, C. J.; CHIRWA, P.
W. Regeneration dynamics of Miombo woodland in
response to different anthropogenic disturbances: forest
characterisation for sustainable management.
Agroforestry Systems, Dordrecht, v. 90, p. 563-576,
2016. DOI: https://doi.org/10.1007/s10457-015-9841-7
VAN WYK, B.; VAN WYK, P. Field guide to trees of
Southern Africa. Cape Town: Struik publishers, 2011.
536p.
VAN HOLSBEECK, S.; CAUWER, V. de; RIDDER, M. de;
FICHTLER, E.; BEECKMAN, H.; MERTENS, J.
Annual diameter growth of Pterocarpus angolensis
(Kiaat) and other woodland species in Namibia. Forest
Ecology and Management, Amsterdam, v. 373, n. 1, p.
1-8, 2016. DOI:
https://doi.org/10.1016/j.foreco.2016.04.031
WEISKITTELAR, H.; KERSHAWJA, D. W.; VANCLAY,
J. K. Forest growth and yield modeling. Chichester:
John Wiley & Sons Ltda, 2011. 415p.
WORLD BANK. Trading economics. Mozambique
GDP 1980-2019. 2020. Disponível em:
https://tradingeconomics.com/mozambique/gdp.
