American Journal of Plant Sciences, 2011, 2, 733-743
doi:10.4236/ajps.2011.26088 Published Online December 2011 (http://www.SciRP.org/journal/ajps)
733
Ecological Structure and Fruit Production of
African Fan Palm (Borassus aethiopum)
Populations
Christine Ouinsavi, Charlemagne Gbémavo, Nestor Sokpon
Laboratoire d’Etudes et de Recherches Forestières (LERF), Faculté d’Agronomie, Université de Parakou, Parakou, Benin.
Received July 6th, 2011; revised August 22nd, 2011; accepted September 9th, 2011.
ABSTRACT
Ecological structure and fruit production of African fan palm stands in Benin were studied on the basis of surveys laid
out in ten (10) populations located in three ecological zones. Dendrometric and fruit production parameters such as:
diameter at breast height (dbh), total height (TH), number of fruit bunch per tree, number of fruits per tree, number of
seeds per fruit, fruit length and width were measured on all African fan palm trees within thirteen (13) plots of 1,000 m2.
Diameter and height classes distribution of the palms in each ecological zone adjusted to Weibull distribution showed a
bell shaped curve with left dissymmetry, characteristic of young stands (form coefficient between 1 and 3.6). African fan
palm stem number was 156 trees/ha. Variation of dbh, TH, number of fruit bunch per tree were highly significant
between populations and ecological zones (P < 0.05%). Trees from Sudanian zone were highly grown (mean dbh =
52.2 cm) while those of Sudano - Guinean transition zone were less (mean dbh = 32.73 cm) and dominated by female
trees. African fan palm stands of Pahou is suitable for seed collection for in situ conservation of the species while those
of Ouorghi and Akomiah could provide fruits for edible hypocotyls production.
Keywords: Ecological Structure, African Fan Palm, Fruit Producti on, Population
1. Introduction
Tropical forests are an important reservoir of biodiversity
and they play a fundamental role in giving satisfaction to
many needs of the people. Nowadays, the non timber
forest products, exploited and consumed by local people
are becoming very scarce due to high human pressure,
over exploitation, non sufficient silvicultural data, cli-
mate changes highlighted by the recurrent dry seasons,
all situation that compromises local people food security
and income. It is the case of African fan palm (Borassus
aethiopum) which provide people with a wide usefulness
on ecological, nutritional, therapeutically, small scale
producing and culturally plans [1-5]. African fan palm
roots are used as anti asthmatic. Its leaves are used in
many craftsmen products. The petioles are used as fenc-
ing, firewood and the hypocotyls are edible [4]. The male
flowers are used as soils fertilizers and as fodder [6].
They are considered as an excellent fodder and their nu-
trients content are similar to those of ground nut and cow-
pea haulm [7]. The bole of the palm is used in carpentry
for house and bridge building. Its wood is very resis-
tant to termites and fungi attacks and to climate varia-
tions.
In Benin, a research work carried out by [3] and [4]
revealed that from the sampled population, 90% of the
households eats African fan palm hypocotyls, 16% eats
the fruits and 13% consume the almonds. The same au-
thors showed that African fan palm contributes to cure
33 diseases and is of great importance to Lokpa and Yom
ethnic groups in the Northern Benin. African fan palm
products are sold and can allow the traders to draw month-
ly gross margin ranging from 20,920 to 112,975 FCFA for
hypocotyls, 332 to 1925 FCFA for fans selling, average
of 6500 FCFA for hats and 1616 to 3264 FCFA for
sieves selling. According to [3], more than 88% of the
organs of African fan palm are useful (hypocotyls, fruits,
almonds, leaves, petioles, blades, boles) and harvested
from natural forests. Meanwhile, African fan palm can ge-
nerate a lot income to the rural population and contribute
to poverty alleviation only few works were carried out on
the structure and dynamics of its populations.
This paper aims to assess ecological structure and pa-

Ecological Structure and Fruit Production of African Fan Palm (Borassus a ethiop um) Populations
734
ttern of fruit production of Borassus aethiopum for a
better management of the tree populations in Benin.
2. Material and methods
2.1. The Study Area
This study was carried out in the Republic of Benin
located in West Africa between 1˚ and 3˚40'E and 06˚30'
and 12˚30'N. It is bordered by Niger in the north, Bur-
kina Faso in the northwest, Togo in the west, Nigeria in
the east and the Atlantic Ocean in the south and covers
an area of 112,622 km2 (Figure 1).
Benin is located in the Dahomey gap which is charac-
terized by numerous physical constraints. The mean an-
nual rainfall is low (900 - 1300 mm) compared with neigh-
bouring countries in the Guineo-Congolean zone such as
Ghana and Côte d’Ivoire (average of 1500 mm) and Ca-
meroon (1800 - 3000 mm).
Reference [8] distinguished four major types of vege-
tation in Benin which are described as follows:
The coastal and sub-coastal zone, which extends from
the coast (6˚20'N up to 7˚N), is composed of beach ve-
getation with an abundance of Remirea maritima and
Ipomea pescaprae, anthropic vegetation of mangrove
swamp forests characterized by Rhizophora racemosa,
Avicennia germinans and Dalbergia ecastaphylum, ri-
parian forests, oil palm and coconut plantations. This zone
has a subequatorial climate type with two rainy seasons
(from mid-March to mid-July and from mid-September
to mid-November) which alternate with two dry seasons
(from mid-July to mid-September and from mid-Nove-
mber to mid-March).
The Guineo-Congolean zone composed of relict semi-
deciduous forests characterized by species such as: Dia-
lium guineense, Triplochiton scleroxylon, Strombosia glau-
cescens, Cleistopholis patens, Ficus mucuso, Cola cordi-
folia, Ceiba pentandra, Trilepisium madagascariense,
Celtis spp, Albizia spp, Antiaris toxicaria, Diopyros
mespiliformi s, Drypetes floribunda, Memecylon afzelii,
Celtis brownii, Mimusops andogensis, Daniellia oliveri,
Parkia spp and Vitellaria paradoxa [9-11], some savan-
na and plantation areas.
The Guineo-Sudanian Transition zone with a mosaic
of forest woodlands, sometimes dry forests and wooded
savanna crossed by gallery forests. The most abundant
species found in this zone are: Isoberlinia doka, I. tomen-
tosa, Monotes kerstingii, Uapaca togoensis, Anogeissus
leiocarpa , Antiaris toxicaria, Ceiba pentandra, Blighia
sapida, Dialium guineense, Combretum fragrans, Entada
Africana, Maranthes polyandra, Pterocarpus erinaceus,
Terminalia la xiflora and Detarium microcarpum.
These two zones are characterized by a Guinean cli-
mate type with two rainy seasons and two dry seasons
distributed as above but the short rainy season of this
region is sometimes absent. The total annual rainfall rea-
ches 1100 mm.
The Sudanian zone composed of dry forests, savanna
woodlands, shrub savanna and savanna grassland. The
gallery forests are characterized by species such as: Hae-
matostaphis barteri, Lannea spp, Khaya senegalensis,
Anogeissus leiocarpa, Tamarindus indica, Capparis spi-
nosa, Ziziphus mucronata, Combretum spp and Cissus
quadrangularis. This zone has a Sudanian climate type
with one rainy season (from April to October) followed
by one dry season (from November to March). The aver-
age rainfall varies from 1100 mm in the southern part of
this zone to 900 mm in the northern part.
According to the FAO world classification of soils, the
major types of soil distinguished in Benin are: Leptosols
in the coastal zone, Acrisols, Ferralsols or Lixisols and
Vertisols in the Guineo-Congolean zone, Luvisols, Lixisols,
Alisols, Plinthosols and Arenosols in the Sudano-Guinean
transition and the Sudanian zones. Human pressure on land
for agricultural purposes and forest exploitation is consi-
derable. In southern Benin where population density
varies from 200 to 450 inhabitants/km2, average farm-
land area is 0.5 ha and the fallow system is more or less
absent. In the north, where mean population density is 14
inhabitants per km2, average farmland area is 5 ha and
fallow length is about 5 years.
Forest over-exploitation has led to declines in the num-
ber of some trees species per hectare. Species such as Mi-
licia excelsa, Khaya senegalensis, Afzelia Africana and
Pterocarpus erinaceus have become scarce in their natural
habitat [12]. Human pressure on forest ecosystems has
also reduced the occurrence of relict forests, mainly sacred
groves [13] and individual trees of some species, such as
Milicia excelsa, Triplochiton scleroxylon, Borassus aeth io-
pum, protected by traditional ethno botanic conservation
practices [14].
2.2. B. aethiopum Description and Populations
Sampling
Borassus aethiopum is a common palm in West African
humid savannas. It is found in drier areas but is then re-
stricted to riversides [15]. It is a savannah tree of 20 to
30 m high and 0.30 to 0.-0 m of diameter. It is a dioe-
cious, tall, solitary and pleonanthic palm of the Bora-
sseae tribe [16]. Male and female flowers appear on se-
parate trees. Leaves are fan-shaped, induplicate and cos-
tapalmate with petioles of 1.5 to 3 m long. The stem is
massive and covered with leaf bases abscising clearly in
older individuals. The male flowers are abundant and
small, inserted at the base of a bract. The female flowers
are larger than the males. Female bear 50 - 100, 1.0 - 1.5

Ecological Structure and Fruit Production of African Fan Palm (Borassus a ethiop um) Populations 735
Figure 1 . Distributio n of African fan palm populations ac c ording to the ecological zones of [17].
kg fresh weight fleshy fruits [15]. Fruits are globulous or
ovoid, yellowish when mature with one to four seeds.
The sap is used to make palm wine [18]. Stems and leaves
are used to construct houses. The tree’s roots are used in
medicine and the bowl is used in bridge construction and
carpentry. Fruits and young seedlings are edible [19].
Seed germination is remote-tubular [16]; [20]: the cotyle-
donary axis extends downward into the soil and carries the
seedling to a depth of 40 cm, where the first roots and
leaves develop.
African fan palm is originated from Sahelian Africa
and its distribution area ranges from Senegal to Tchad.
The species is found in Benin, Niger, Togo, Ghana, Côte
d’Ivoire, Gambia, Senegal, Burkina-Faso, Mali, Mauri-
tania, Nigeria and Tchad.
In Benin, African fan palm populations were sampled
according to three ecological zones as follows: Goroubi,
Loumbou-loumbou, Niaro and Kongourou in the Suda-
nian zone; Akomiah and Ouorghi in the Sudano-Guinean
Transition zone; Se, Grand-Popo, Pahou and Ouidah in
the Guinean zone (Table 1).
2.3. Data Collection
Rectangular plots of 1000 m2 were laid in each sampled
population of African fan palm. The plot number varies
according to the area covered by African fan palm popu-
lation. Diameter at breast high and the total height of all
the fan palm trees contained in each plot were measured.
In total, 203 palm trees covering 13,000 m2 were mea-
sured (Table 2).
The sex of each tree, the number of fruits bunch and
the number of fruits per female tree were recorded. The
size (length and width) of each fruit and the number of
seeds per fruit were also recorded. In total 82 males and
121 female trees were sampled to estimate tree fruit
production.
2.4. Data Analysis
African fan palm trees distribution within population and
according to the ecological zones was adjusted to the
Weibull function, commonly nowadays used in Forestry
surveys [21-23]. The Weibull distribution is as follows:
1
() exp
cc
cxa xa
fx bb b


 
 
 
 


a = position parameter; a = 20 cm (diameter); a = 5 or
7 m (Height according to the sites);
b = scale parameter or size parameter;
c = form parameter linked with the observed structure.
Trees diameter or trees height distribution were ad-
justed to Weibull function with Minitab 14 Software. A
one way Analysis of Variance was performed to test for
statistical difference between different ecological zones

Ecological Structure and Fruit Production of African Fan Palm (Borassus a ethiop um) Populations
736
Table 1. Distrib ution of B. aethiopum populations acco rding to the three e cological zones.
Ecological zones B. aethiopum populations Latitude Longitude Rainfall gradient
Goroubi 11˚55.055 003˚15.484
Lombou-loumbou 12˚14.217 002˚54.218
Niaro 10˚23.433 002˚25.039 700 to 900 mm
Sudanian
Kongourou 10˚22.571 002˚50.308
Akomiah 08˚06.241 002˚32.432
Sudano-Guinean
Transition Ouorghi 08˚10.201 002˚37.221 1000 to 1200 mm
Se 06˚29.037 001˚50.152 1100 mm
Pahou 06˚23.177 002˚14.069 1200 mm
Grand Popo 06˚17.484 001˚49.278 900 mm
Guinean
Ouidah 06˚23.429 001˚58.538 1200 mm
Table 2. Descript ion of B. aethiopum studied pop ulations .
Ecological zones B. aethiopum populations Plot number Trees number Total plots number per
ecological zones
Total trees number per
ecological zones
Goroubi 1 3
Lombou -loumbou 1 21
Niaro 1 21
Sudanian
Kongourou 1 17
4 62
Akomiah 2 30
Sudano-Guinean
Transition Ouorghi 2 30 4 60
Se 1 20
Pahou 1 18
Grand Popo 2 22
Guinean
Ouidah 1 21
5 81
Total 13 203 13 203
for variable such as: dbh, total height, fruits number per
tree, fruits cluster number per tree, seeds number per
fruit, fruit size (length and width) using SPSS for Win-
dows V. 16 Software. Turkey Homogeneity test allows
us to separate the site and ecological homogeneous groups.
The correlations between growth parameters and fruits
production were performed with Minitab 14 Software.
3. Results
3.1. Diameter Classes’ Distribution of
B. aethiopum Trees
Figure 2 showed the class distribution of the fan palm
trees diameter according to the different ecological zones.
The Weibull distribution of fan palm trees per diameter
classes shows a left dissymmetric bell shaped curve with
a c form coefficient comprised between 1 and 3.6 for the
three ecological zones. This value of c means that the
stands were dominated by young trees. In the Sudanian
zone, trees of diameter class centre 35 and 65 were do-
minant in the stand while in the Sudano-Guinean Tran-
sition zone and Guinean zone, trees of diameter class
centre 25 were dominant.
3.2. Total Height Classes Distribution of
B. aethiopum Trees
Figure 3 showed the total height class distribution of
trees of African fan palm according to the three ecologi-
cal zones. This distribution well adjusted to the Weibull
function showed a bell shaped curve with a left dissym-
metry (1 ≤ c ≤ 3.6). Like the diameter class distribution,
the stands were dominated by young trees. In the Su-
danian zone, trees of class (8 - 12 m) were dominant in
the population while in the Sudano-Guinean Transition
zone and the Guinean zone, trees of height class (12 - 14
m) were dominant in the stands.
3.3. Structural Characteristics of B. aethiopum
Populations
Table 3 showed the number of tree per stand and per
ecological zones of the studied African Fan Palm popu-

Ecological Structure and Fruit Production of African Fan Palm (Borassus a ethiop um) Populations737
Center of diameter classes
Frequency ( trees/Class)
85756555453525
20
15
10
5
0
Shape 2,235
Scale 37,08
Thresh 20
N6
3-Parameter Weibull
Sudanean zone populations
2
2.235
37.08
Center of diameter classes
F re quenc y (trees/class)
55453525
40
30
20
10
0
Shape 2,031
Scale 14,71
Thresh 20
N60
3-Parameter Weibull
Sudano-Guinean transition zone populations
2.031
14.71
C enter of diam eter classes
F re q uency ( trees/class)
756555453525
40
30
20
10
0
Shape 1,498
Scale 17,26
Thresh 20
N81
3-Parameter Weibull
Guinean zone populations
1.498
17.26
Figure 2. Diameter classes’ distributio n of trees of African fan palm population s.
Center of height c lasses
Frequency ( trees/Class)
242016128
20
15
10
5
0
Shape 1,659
Scale 7,087
Thresh 7
N6
3-Parameter Weibull
Sudanean zone p o pulat ions
2
1.659
7.087
Center of height classes
Frequenc y (tree s/Classe)
18161412
40
30
20
10
0
Shape 2,347
Scale 3,307
Thresh 11
N60
3-Parameter Weibull
Sudano -Guinea n transitio n zone populations
2.347
3.307
Ce nter of he ight classes
F re que ncy (tree s/Class)
181614121086
40
30
20
10
0
Shape 3,530
Scale 8,290
Thresh 5
N81
3-Parameter Weibull
Guinean zone populations
3.530
8.290
Figure 3. Total height classes distribution of trees of African fan palm populations .

Ecological Structure and Fruit Production of African Fan Palm (Borassus a ethiop um) Populations
738
Table 3. Trees number per st and and per ecological zones of the stu died B. aethiopum populations.
Ecological zones B. aethiopum populations Sampled area (m2)Number of
trees
Number of trees
per ha
Number of trees per
ecological zones (trees/ha)
Goroubi 1000 3 30
Lombou-loumbou 1000 21 210
Niaro 1000 21 210
Sudanian zone
Kongourou 1000 17 170
155
Akomiah 2000 30 150
Sudano-Guinean
Transition zone Ouorghi 2000 30 150 150
Se 1000 20 200
Pahou 1000 18 180
Grand Popo 2000 22 110
Guinean zone
Ouidah 1000 21 210
162
Total 13,000 203 - -
lations. The average number of trees of African fan palm
was 156 trees per hectare across the study area. The den-
sity varies from 150 trees per hectare with stands of Su-
dano-Guinean Transition zone to 162 trees/ha when con-
sidering populations of Guinean zone. The lower number
of trees /ha were recorded in populations of Goroubi (30
trees/ha); Grand-Popo (110 trees/ha), Ouorghi and Ako-
miah (150 trees/ha). Table 4 showed the structural charac-
teristics and fruit production of African Fan Palm trees.
The mean diameter at breast high of the palm trees
ranged from 25.56 cm (Population of Se) to 62.03 cm
(Population of Niaro) and Kongourou (62.05 cm). For
the populations of Ouorghi, Akomiah, Goroubi, Grand
Popo and Loumbou-loumbou, the mean diameter was
respectively 31.55 cm; 33.92 cm; 34.43 cm; 33.88 cm
and 36.32 cm. When considering the populations of
Ouidah and Pahou, the mean diameter of the fan palm
trees was as follows: 42.99 cm and 39.1 cm. There is a
highly significant difference within and between the trees
populations as far as the trees diameter is concerned (P <
0.001). When considering the ecological zones, the mean
tree diameter was 52.20 cm with the Sudanian popula-
tions; 32.73 cm in the Sudano-Guinean Transition zone
and 35.34 cm in the Guinean zone. The mean diameter of
the African fan palm trees highly varied according to the
ecological zones.
The mean total height of the trees varied from 9.77 m
(Population of Kongourou) to 17.52 m (Population of
Loumbou-loumbou). When considering the population of
Akomiah, Goroubi, Ouidah and Ouorghi, the mean total
height of the trees was respectively 13.98 m; 13.50m;
12.79 m and 13.96 m. There is a highly significant dif-
ference between the African fan palm trees populations
as far as the trees total height is concerned (P < 0.001).
When considering the ecological zones, the mean total
height of trees varies from 12.38 m (populations of Gui-
nean zone to 13.16 m (Populations of Sudanian zone)
and 13.97 m (Population of Sudano-Guinean Transition
zone).
3.4. Fru i t s P r od u ction of B. aethiopum
Populations
The fruit number increased with size as shown on Figure
4. The minimum fruiting diameter was 25 cm with a
maximum of 85 cm. The maximum average number of
fruit per tree (120 - 140 cm) was obtained for the dia-
meter class centre 55 cm while in the younger diameter
class (25 - 45 cm) this average number ranged from 60 to
80. Table 3 also showed fruit production feature of
African fan palm populations. The average number of
fruit per tree started to decrease from diameter class cen-
tre 85 cm. The average number of fruits bunch varied
from 3 (Population of Grand-Popo) to 10 (Population of
Loumbou-loumbou). For the populations of Niaro, Ouidah,
Ouorghi, Kongourou, the average number of fruit bunch
was respectively: 7.4; 7.83; 7.47 and 8.2. There is a
significant difference between the African fan palm po-
pulations as far as the number of fruit bunch per tree is
concerned. When considering the ecological zones, the
average number of fruit bunch was 8.65 for the po-
pulations of the Sudanian zone; 6.12 in the Sudano-
Guinean Transition zone and 7.21 for the populations of
Guinean zone.
The average number of fruit per tree varied from 14.5
(Population of Grand Popo) to 103.4 (Population of
Pahou). When considering the populations of Loumbou-
loumbou, Niaro, Ouidah, Ouorghi and Kongourou, the
average number of fruit per tree was respectively: 50.77;
86; 91.17; 89.74: 89.20. When considering the different
ecological zones, the average number of fruit per tree
was 62.58 for Sudanian zone populations; 77.48 for po-
pulations of Sudano-Guinean Transition zone and 85.41

Ecological Structure and Fruit Production of African Fan Palm (Borassus a ethiop um) Populations739
Table 4. Structural characterist ics and fruit production of African fan pal m trees. Means with the same letter are not statis-
tically different according to Turkey homogeneity test.
B. aeth iopum
populations Mean DBH (cm) Mean total height (m) Average number of bunch of fruit per treeAverage number of fruit per tree Average number of seeds per fruit Fruit length Fruit width
Akomiah 33.92ab 13.98c 6.12ab 77.48ab 2.50a 12.95a 14.98a
Goroubi 34.43ab 13.50bc 7ab 35.67ab 2.75a 13.23a 12.87a
Granp Popo 33.88ab 9.92a 3a 14.50a - - -
Loumbou-lombou 36.32bc 17.52d 10b 50.77ab 1.69a 13.29a 14.26a
Niaro 62.63d 11.50ab 7.40ab 86.00ab 2.11a 12.42a 13.56a
Ouidah 42.99c 12.79bc 7.83ab 91.17ab - - -
Ouorghi 31.55ab 13.96c 7.47ab 89.74ab 2.54a 13.39a 14.16a
Pahou 39.1bc 13.38bc 7.7ab 103.40b - - -
Sè 25.56a 13.77c 5.8ab 64.6ab 2.67a 12.47a 14.53a
Kongourou 62.05d 9.77a 8.20ab 89.20ab 2.00a 14.30a 14.70a
Probability (%) 0.000 0.000 0.030 0.020 0.155 0.939 0.557
Ecological zones
Sudanian 52.20b 13.16ab 8.65b 62.58a 2a 13.03a 13.84a
Sudano-Guinean
Transition 32.73a 13.97b 6.12a 77.48a 2.67a 12.47a 14.53a
Guinean 35.34a 12.38a 7.21ab 85.41a 2.52a 13.20a 14.52a
Probability (%) 0.000 0.003 0.023 0.092 0.089 0.851 0.415
Figure 4. Diameter class distribution of number of fruits
per African fan palm tree.
for populations of Guinean zone. The mean length of the
fruits varied from 12 cm (Populations of Niaro, Se) to
14.3 (Population of Kongourou) while the mean width of
the fruit varied from 12 cm (Population of Goroubi) to
14.98 cm (Population of Akomiah).
3.5. Correlations between Fruit Production
Parameters
Table 5 showed the correlation patterns between trees
dbh, the fruit number and the number of fruit bunch per
tree. The number of fruit bunch and the number of fruits
per tree were not correlated with the diameter at breast
height. However, the number of fruit per tree was strongly
correlated with the number of fruit bunch it bears. There
was strong correlation between fruit size (length and width)
and the number of seeds per fruit (Table 6). Table 7
showed the number of seed per fruit according to popu-
lations and ecological zones. When considering the eco-
logical zones, fruits in populations of the Sudanian zone
(Goroubi, Loumbou-loumbou, Niaro) and in Sudano-
Guinean transition zone (Akomiah, Ouorghi) have three
seeds while those of Guinean zone have one or two seeds.
The average fruit number per female tree varies between
the populations within a given ecological zone but not
from one ecological zone to the other. African fan palm
trees in the Sudanian populations were larger (high mean
dbh, high total height and high number of fruit cluster)
but did not have the higher number of fruits per tree.
Trees in the Ouidah population produced the highest
number of fruit (91.17 fruit per tree in average). Tees in
the Guinean zone produced the highest number of fruits
with an average of 85.4 fruits per tree. Most of the palm
trees in the Sudano-Guinean transition zone were female
while those in the Sudanian zone were almost equal in
sex (Table 8).
4. Discussion
4.1. Structural Characteristics of B. aethiopum
Populations
The mean number of palm trees per hectare recorded in

Ecological Structure and Fruit Production of African Fan Palm (Borassus a ethiop um) Populations
740
Table 5. Correlation between trees dbh, fruit number and
number of fruit bunch per trees.
Number of fruit bunch Fruit numberDbh
Number of fruit bunch 1
Fruit number 0.707*** 1
Dbh 0.157 0.159 1
Table 6. Correlation between fr uit l ength and width and the
number of seeds per fruit.
Fruit length Fruit width Seeds number
Fruit length 1
Fruit width 0.825*** 1
Seed number 0.677*** 0.568*** 1
*** Significant Correlation at the level of 1%.
Table 7. Number of seed per fruit according to B. aethio-
pum populati ons and ecological zones.
Fruits number with:
B. aethiopum populations 1 kernel 2 seeds 3 seeds4 seeds
Goroubi 1 0 2 1
Loumbou-loumbou 5 4 3 0
Niaro 3 2 4 0
Sudanian
Kongourou 0 1 0 0
Akomiah 2 1 7 0
Sudano
-Guinean
Transition Ouorghi 1 4 8 0
Ouidah - - - -
Se 0 1 2 0
Pahou - - - -
Guinean
Grand popo - - - -
Total 12 13 27 1
Table 8. Sex ratio of trees of B. aethiopum populations.
Means with the same letter are not statistically significant
according to Student t test at the level of 5%.
Ecological zones B. aethiopum
populations
Male trees
number
Female trees
number
Ratio
male/female
Goroubi 0 3 -
Loumbou-
loumbou 8 13 0.61a
Niaro 11 10 1.1a
Sudanian
Kongourou 12 5 2.4a
Akomiah 5 25 0.2a
Sudano-Guinean
Transition Ouorghi 8 22 0.36a
Ouidah 9 12 0.75a
Se 9 11 0.81a
Pahou 8 10 0.8a
Guinean
Grand popo 12 10 1.2a
Total 82 121 -
the different ecological zones is similar to those obtained
by [24] in Wolokonto village in Burkina-Faso. The dia-
meter at breast high for the palm trees in the Sudanian
zone was higher than those of trees in Guinean and
Sudano-Guinean transition zone. According to [25], Suda-
nian climate was suitable for the optimal development of
the African fan palm trees. However, there is generally a
relationship between species temperament and their stem
diameter class distribution. The shade tolerant species
have an all-age population structure which gives the cha-
racteristic inverse J-shaped curve or negative exponential
stems distribution. These species are stable species as far
as the equilibrium stand distribution is concerned [26-31].
The bell-shaped distribution species are generally light
demanding species. They are generally gap depending
for their regeneration. Mortality is higher in earlier stage
under closed forest canopy. The number of large trees is
higher. More caution is required as far as species tem-
perament and stem class distribution are concerned. The
stem diameter distribution of species greatly varies with
observed plot size. Some species having a bell-shaped
distribution within small plot could show inverse J- sha-
ped when plots are larger (regular distribution to aggre-
gative, [32]. In Ghana, for instance, [33] showed that on
a national level, the majority of the forest species have
sufficient natural regeneration and most species show
inverse J-shaped curves.
Furthermore, finding patterns among life histories is a
challenge for modern ecology [34]. It requires linking
evolution and demography and has led to many theore-
tical models and field studies [35]. According to [23], the
use of Weibull distribution probability density function is
becoming increasingly popular for modeling the dia-
meter distributions of both even and uneven-aged forest
stands. The popularity of Weibull is derived from its fle-
xibility to take on a number of different shapes corres-
ponding to many different observed unimodal tree-
diameter distributions. In addition, the cumulative distri-
bution function of Weibull exists in closed form and thus
allows for quick and easy estimation of the number of
trees by diameter class without integration of the proba-
bility density function once the parameters have been
fitted. The bell shaped function obtained with the dia-
meter or height classes distribution of the palm trees with
a left dissymmetry corroborate the results of [36] with
the African fan palm population of Wolokonto in Burkina-
Faso. Similar results were also obtained by [37] with the
Shea butter trees of Donfelgou in Togo. Also [23] ob-
tained the same distribution as far as Afzelia africana
trees populations are concerned in Benin. However this
structure might not be derived only from the species
temperament but also from human pressure.

Ecological Structure and Fruit Production of African Fan Palm (Borassus a ethiop um) Populations741
4.2. Fru i t and H y pocotyls Pro duct io n an d
Sustainable Management of the
B. aethiopum Populations
Even though, the average number of fruit per tree did not
vary significantly from one ecological zone to the other,
trees in the Guinean zone and mainly the population of
Pahou were more productive in term of number of fruit
(103.4 fruits per tree). The palm tree with the higher
number of fruits was from Pahou population (270 fruits).
According to [16], [38] in [39], this number is higher
than those obtained with the populations of African fan
palm in Niger (250 fruits per tree) and in Côte d’Ivoire
(50 - 100 fruits per tree).
When we considered the number of seeds per fruit,
trees of populations of the Sudano-Guinean transition
zone have in majority (15 out of 23) three seeds. The
number of fruit with three seeds is higher in the popula-
tions of Sudano-Guinean Transition zone than other po-
pulations indicating that seeds from Sudano-Guinean
Transition zone are suitable for hypocotyls production.
B. aethiopum tree is nowadays subjected to high pres-
sure and this situation was emphasized by [13] who clas-
sified the species as an endangered species on which
many conservation actions should be focused. This pres-
sure on the species is related to severe fruits and hypo-
cotyls harvesting that hypothesised natural regeneration
of the species.
As each organ of the tree is of great importance, long
term management of B. aethiopum populations is needed
to improve local population livelihood. Therefore, sus-
tainable management of African fan palm populations for
providing woods for housing, fencing and fuel woods
should mainly rely on the male trees with a sex ratio of
three females for one male and an optimal number of 100
trees per hectare. On this basis, we suggested that the
number of trees to be harvested should be:
- 3 males from the population of Loumbou-loumbou, 7
from Niaro and 9 from Kongourou population as far
as the Sudanian zone is concerned;
- 10 and 2 female trees from Akomiah and Ouorghi po-
pulations respectively as far as the Sudano-Guinean
transition zone is concerned;
- 5 male trees from each Ouidah, Sè and Pahou popu-
lations in the Guinean zone.
Natural regeneration of the palm trees should be pro-
moted as well as hypocotyls production from nursery
seed germination.
5. Conclusions
Ecological structure of the African fan palm populations
of Benin, adjusted to Weibull distribution showed a bell
shaped curve with a left dissymmetry proving the pre-
dominance of young trees within these populations. Stru-
ctural characteristics of the stands greatly varied from
one population to the other and from one ecological zone
to the other. The trees mean dbh varied from 25.56 cm to
62.63 cm while the total height of the trees from 9.77 m
to 17.52 m. The average number of fruit clusters varied
from 3 (Population of Grand Popo) to 10 (Population of
Loumbou-loumbou). The average number of fruits per
tree varied from 14.5 (Population of Grand Popo) to
103.4 (Population of Pahou). The average number of
seeds per fruit varied from 1 to 3. Most of fruits from
populations of Sudanean and Sudano-Guinean Transi-
tion zones had 3 seeds per fruit. The mean length of the
fruits varied from 12.42 cm (Population of Niaro) to 14.3
cm (Population of Kongourou). The fruit mean width
varied from 12.87 cm (Population of Goroubi) to 14.98
cm (Population of Akomiah). Environmental factors
(Rainfall and temperature) seemed to discriminate the
African fan palm populations of Benin and were key
factors for the fruit production. When considering the
ecological zones, trees of Guinean zone were higher fruit
producers with an average fruits per tree of 85.4. Most of
the fan palm trees of the Sudano-Guinean transition zone
were female while those of the Sudanean zone were al-
most equal in sex. Therefore sustainable management of
African fan palm populations for providing woods for
housing, fencing, and fuel woods should mainly rely on
the male trees with a sex ratio of 3 females for 1 male
and an optimal number per hectare of 100.
However, as the species has particularly important
socio-economic value for local people, there is a priority
need to address the impact of its organs’ exploitation and
eventually human-caused habitat fragmentation on its ge-
netic structure for conservation purposes.”
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