ArticlePDF Available

Geographical distribution, tree density and fruit production of Tamarindus indica L. (Fabaceae) across three ecological regions in Benin

Authors:

Abstract and Figures

Introduction. There has been increasing interest in the domestication potential of indigenous fruit trees. Nevertheless, our understanding of how these species' abundance and yield of fruit is altered by ecological conditions, which is critical to foresee realistic sustainable management plans, is limited. Material and methods. We used local ecological knowledge, presence/absence data and quantitative methods to examine the effect of ecological conditions on the distribution, abundance and yields of tamarind trees (T. indica) across three ecological regions in Benin, West Africa. Results and discussion. Rural communities’ knowledge on the species’ ecological range was congruent with scientific findings. The natural distribution of tamarind individuals was limited to the Sudanian and the Sudano-Guinean regions and their density declined with increasing moisture, being highest (2 trees·km–2) in the Sudanian region and lowest in the Guineo-Congolian region (scarce). On the other hand, fruit and pulp mass and number of seeds per fruit varied significantly, being higher in the Guineo-Congolian wetter region. However, no significant variation occurred among ecological regions for estimated overall fruit yields per tree. This might indicate that tamarind trees tend to invest in a small number of very large fruits under wetter conditions and a very large number of small fruits under dryer conditions. Conclusion. The results showed that semi-arid lands would best suit T. indica domestication. Nevertheless, its productivity could be higher under wetter conditions. Because of its affinity for gallery forests, we recommend thorough studies on its capacity to survive the increasing drought in its current ecological range.
Content may be subject to copyright.
Original article
Fruits, vol. 66 (2) 53
Geographical distribution, tree density and fruit production of Tamarindus
indica L. (Fabaceae) across three ecological regions in Benin.
Abstract –– Introduction. There has been increasing interest in the domestication potential
of indigenous fruit trees. Nevertheless, our understanding of how these species' abundance and
yield of fruit is altered by ecological conditions, which is critical to foresee realistic sustainable
management plans, is limited. Material and methods. We used local ecological knowledge,
presence/absence data and quantitative methods to examine the effect of ecological conditions
on the distribution, abundance and yields of tamarind trees (T. indica) across three ecological
regions in Benin, West Africa. Results and discussion. Rural communities’ knowledge on the
species’ ecological range was congruent with scientific findings. The natural distribution of
tamarind individuals was limited to the Sudanian and the Sudano-Guinean regions and their
density declined with increasing moisture, being highest (2 trees·km–2) in the Sudanian region
and lowest in the Guineo-Congolian region (scarce). On the other hand, fruit and pulp mass
and number of seeds per fruit varied significantly, being higher in the Guineo-Congolian wetter
region. However, no significant variation occurred among ecological regions for estimated ove-
rall fruit yields per tree. This might indicate that tamarind trees tend to invest in a small number
of very large fruits under wetter conditions and a very large number of small fruits under dryer
conditions. Conclusion. The results showed that semi-arid lands would best suit T. indica
domestication. Nevertheless, its productivity could be higher under wetter conditions. Because
of its affinity for gallery forests, we recommend thorough studies on its capacity to survive the
increasing drought in its current ecological range.
Benin / Tamarindus indica / population distribution / population density /
fruiting / indigenous knowledge
Répartition géographique, densité des arbres et production de fruits de
Tamarindus indica L. (Fabaceae) dans trois régions écologiques au Bénin.
Résumé –– Introduction. Le potentiel de domestication des arbres fruitiers indigènes a suscité
un intérêt croissant. Néanmoins, la façon dont l’abondance de ces espèces et leur rendement
en fruits sont affectés par les conditions écologiques, élément essentiel pour prévoir des plans
de gestion durable réalistes, est peu documentée. Matériel et méthodes. Nous avons utilisé
des connaissances écologiques locales, des données de présence / absence et des méthodes
quantitatives pour étudier l'effet des conditions écologiques sur la répartition, l'abondance et
les rendements des tamariniers (T. indica) dans trois régions écologiques du Bénin, en Afrique
de l'Ouest. Résultats et discussion. La connaissance de l'aire de répartition écologique par les
communautés rurales a été en accord avec les résultats scientifiques. La répartition naturelle des
tamariniers a été limitée aux régions soudanaise et soudano-guinéenne et leur densité a diminué
avec l’accroissement du taux d'humidité; la densité a été la plus élevée (2 arbres·km–2) dans la
région soudanaise et la plus basse dans la région guinéo-congolaise (présence rare). D’autre
part, la masse de pulpe et de fruits ainsi que le nombre de graines par fruit ont sensiblement
varié; ces caractères ont été les plus élevés dans la région humide guinéo-congolaise. Cepen-
dant, aucune variation significative n’est apparue d’une région écologique à l’autre en ce qui
concerne les rendements globaux de fruits par arbre. Cela pourrait indiquer que les tamariniers
tendent à produire un petit nombre de gros fruits en milieu plus humides et un grand nombre
de petits fruits en milieu plus sec. Conclusion. Nos résultats pourraient suggérer que les zones
semi-arides pourraient mieux convenir à la domestication de T. indica. Néanmoins, la produc-
tivité de l’espèce pourrait être plus élevée en conditions plus humides. Sur la base de son affinité
pour les forêts-galeries, nous recommandons des études approfondies sur sa capacité à survivre
à des stress hydriques croissants dans son environnement écologique actuel.
Bénin / Tamarindus indica / distribution des populations / densité de
population / fructification / connaissance indigène
Lab. Appl. Ecol., Fac. Agron.
Sci., Univ. Abomey-Calavi, 01
BP 526, Cotonou, Benin,
bfandohan@gmail.com
Geographical distribution, tree density and fruit production
of Tamarindus indica L. (Fabaceae) across three ecological
regions in Benin
Belarmain FANDOHAN*, Achille Ephrem ASSOGBADJO, Romain Glèlè KAKAÏ, Brice SINSIN
* Correspondence and reprints
Received 19 February 2009
Accepted 3 June 2009
Fruits, 2011, vol. 66, p. 53–62
© 2011 Cirad/EDP Sciences
All rights reserved
DOI: 10.1051/fruits/2010043
www.fruits-journal.org
RESUMEN ESPAÑOL,p.62
54 Fruits, vol. 66 (2)
B. Fandohan et al.
1. Introduction
Until recently, little interest has been
shown in indigenous multipurpose tree spe-
cies compared with their industrial timber
counterparts. Available information gener-
ally lacks adequate quantitative analysis for
the development of economic opportunities
based on local resources as an alternative to
excessive import of exotic products. Thus,
initiatives in agroforestry seek to integrate
indigenous trees whose products have tra-
ditionally been gathered from natural forests
into tropical farming systems [1]. This is also
to provide marketable products from farms
that will generate income for resource-poor
rural households. As such, it has led to an
increasing interest in the domestication
potential of some traditionally valued agro-
forestry trees in Africa, i.e.,Detarium micro-
carpum Harms [2], Irvingia gabonensis
(Aubry Lecomte ex O'Rorke) Baill. [3] and
Sclerocarya birrea (A.Rich.) Hochst.) subsp.
caffra (Sond.) [4], to cite just a few.
The growing number of studies on the
domestication potential of indigenous trees
have provided information about morpho-
logical and genetic diversity [5, 6], potential
productivity [7] and nutritional and medici-
nal properties [8]. However, as local envi-
ronmental conditions influence variation in
plants [9], domestication programs should
also consider the impact of ecological fac-
tors on distribution, abundance and fruiting
potential of the targeted species. Such
aspects are poorly explored but critical for
identification of priority sites for planting
and genetic improvement. In addition, such
information may highlight the extent to
which natural populations could supply
market demand with products (i.e. fresh
fruit and pulp) depending on ecological
conditions. Although a number of studies
have demonstrated that the distribution,
abundance and fruiting potential of indige-
nous multipurpose trees depend on envi-
ronmental conditions [7, 10], the effect of
environmental conditions may vary with
plant species. In addition, the accuracy of
abundance estimation may be strongly
dependent on the method used and robust
statistical methods should be used when-
ever possible.
T-Square sampling [11] is a distance-
based sampling method which has been
used in ecology to estimate sizes and den-
sities of many plant populations [12]. It is a
robust method that can provide informative
results even if no prior information exists
about the randomness or the uniformity of
the spatial pattern of the species studied,
and is especially suited to large-scale pop-
ulation studies [13]. T-square sampling can
therefore be used to evaluate the abundance
of indigenous fruit trees or multipurpose
trees nationwide or regionwide. In addition,
recent ethnoecological studies advocate an
integration of local ecological knowledge
and ecological studies to advance our
understanding of ecological processes and
develop better plans for sustainable
resource use [14]. To enable such integra-
tion, it is important to evaluate the congru-
ence of local ecological knowledge with
available scientific findings [14].
Tamarindus indica L. is a semi-ever-
green tree widespread in the tropics (Africa,
Asia, Madagascar, South America), featuring
prominently in riparian habitats [15]. In
efforts to enhance the species’ genetic
resource conservation and utilization, it has
recently been identified as one of the top
ten agroforestry tree species to be priori-
tized for future crop diversification pro-
grams and development in sub-Saharan
Africa [16]. There has been extensive inter-
est in tamarind's biochemical, medicinal
and nutritional properties, reproductive
biology, morphology, cultivation and genet-
ics [17]. Studies on the species in Asia, Africa
and Latin America have documented its
domestication potential in terms of socio-
cultural and nutritional values, and aptitude
for seed and vegetative propagation [17].
Tamarind’s global distribution map has
given strong evidence of its plasticity in the
tropics [18]. Studies on the species’ native
populations in Africa have provided data on
biochemical analysis of its fruits [19], genetic
diversity, phenology, reproductive biology
including pollinators, biometrical characters
of seeds and seedlings [20–23], and impact
of habitat type on its conservation status
[24]. However, little scientific information is
available on how ecological conditions
locally influence its distribution, abundance
T. indica in three ecological regions of Benin
Fruits, vol. 66 (2) 55
and productivity in Africa. In this study, we
used LEK and ecological studies to examine
the distribution and productivity of tama-
rind trees in Benin as a case study. The fol-
lowing questions were addressed: (1) What
is the distribution range and abundance of
T. indica in relation to the ecological con-
ditions it lives in? (2) How do ecological and
tree-level factors alter its productivity of
fresh fruits, pulp and seeds?
2. Materials and methods
2.1. Study area
Our study was conducted in Benin (West
Africa). Ongoing work on the ecological
niche of T. indica in Benin has confirmed
the presence of tamarind individuals in the
three ecological regions of the country
(the Sudanian, Sudano-Guinean and sub-
humid Guineo-Congolian regions [25]).
Thus, this study was conducted nationwide
(114 673 km²) [26].
In the Sudanian region (9°45’–12°25’ N),
rainfall is unimodal. Mean annual rainfall is
often less than 1000 mm, the relative humid-
ity varies between 18% and 99% (highest in
August) and temperature varies between
24 °C and 31 °C. The Sudanian region has
hydromorphic soils, well-drained soils and
lithosols.
In the Sudano-Guinean region (7°30’–
9°45’ N), rainfall is unimodal, from May to
October, and lasts for about 113 days with
an annual total rainfall varying between
900 mm and 1110 mm. Mean annual tem-
perature ranges from 25 °C to 29 °C, and the
relative humidity from 31% to 98%. The soils
in this zone are ferruginous.
In the Guineo-Congolian region (6°25’–
7°30’ N), rainfall is bimodal with a mean
annual rainfall of 1200 mm. Mean annual
temperature varies between 25 °C and 29 °C
and the relative humidity varies between
69% and 97%. The soils are either deep fer-
rallitic or rich in clay.
The principal ethnic groups are the
Dendi, Bariba, Fulani, Waama and Gour-
mantché in the Sudanian region; the Fon,
Tchabè, Nago, Agnin and Idatcha in the
Sudano-Guinean region; and the Yoruba,
Adja, Tori, Holi, Péda and Xwla in the
Guineo-Congolian region. We focused on
these 16 aforementioned ethnic groups dur-
ing this study because they were the most
ancient in their locations throughout the
study area.
2.2. Ethnoecological survey
Our survey aimed at documenting local
perceptions about the distribution of tama-
rind trees in Benin. We applied semi-struc-
tured individual interviews to five traditional
hunters / healers and five Fulani herders
randomly sampled within each of the
77 state districts of Benin (770 respond-
ents). The sampling was limited to persons
of at least fifty, so that only experienced
informants were questioned. We targeted
Fulani herders because they are culturally
associated with the species and usually keep
the fruits during migrations (personal field
observation). The healers and hunters were
chosen because of their local reputations in
plant knowledge. These socio-professional
groups are more likely to hold very inform-
ative knowledge about the past and present
distribution of the species. The following
questions were asked: (i) As an indicator of
its presence in earlier times, we asked
whether tamarind had a local name in the
language of the most ancient indigenous
ethnic groups of each district; (ii) Is the spe-
cies currently found in the natural vegeta-
tion? If yes, in which habitats? (iii) Was the
species present in the native vegetation in
earlier times? If it was present in earlier times
but is not currently present, then why has
it disappeared?
2.3. Characterization
of the distribution patterns
and density of tamarind
In each of the 77 state districts, we made
a visual confirmation of the species’ pres-
ence/absence within protected areas, for-
ests and farmlands, following unfixed
transect lines across natural vegetation, with
the help of transhumants or hunters recom-
mended by local leaders.
56 Fruits, vol. 66 (2)
B. Fandohan et al.
Then, we performed a sampling plan for
tamarind density estimation based on the
ten phytogeographical subdivisions of the
three ecological regions [27]. We randomly
selected one to two sites (protected areas
and surrounding farmlands) within each
phytogeographical district where tamarind
natural populations were observed
(table I). The density of the species was esti-
mated using the T-Square sampling
method. Each phytogeographical district
was represented by 45–90 sampled points
for density estimation (overall 630 points
for 112622 km²), following a protocol
already published [28]. To address any
underlying heterogeneity in tamarind trees’
pattern, a stratification of the vegetation and
a systematic sampling approach were per-
formed. Thus, each selected site was first
stratified into three habitats: forest, savan-
nah and farmland. We established 15 points
in each habitat. The 15 points were distrib-
uted on five azimuth transects of 15 km, so
that each transect was divided into
3 equally spaced marks (5 km) (Si); then,
from each marked point, the distance (xi)to
the nearest tamarind individual (T1) was
measured using a global positioning system
(GPS Garmin 76). Next, the distance (yi)
between T1and its nearest neighbor (T2)
situated in the ‘half-plane’ excluding Siwas
measured [29] (figure 1). We used a GPS
instead of a tape measure or a decameter
since “x” and “y” distances were often over
500 m, except in gallery forests.
2.4. Estimating average yield
of fresh fruit, pulp and seeds
Data were collected on a total of 65 trees
sampled among the trees that we located
when estimating tree density. Thirty trees
were sampled in both the Sudanian and
Sudano-Guinean regions while only five
trees were selected in the Guineo-Congolian
Table I.
Sampling plan for assessing geographical distribution, tree density and fruit production of Tamarindus indica L.
in three ecological regions of Benin.
Ecological regions Phytogeographical district State district Study site Coordinates
Lat. E Long. N
1 Sudanian Atacora Chain Tanguiéta Pendjari National Park 1° 44’ 11° 07’
2 Mekrou-Pendjari Karimama W National Park 2° 54’ 12° 06’
3 Mekrou-Pendjari Tanguiéta Pendjari National Park 1° 30’ 11° 25’
4 Borgou North Banikoara W National Park 2° 40’ 11° 55’
5 Borgou North Pehunco Upper Alibori Forest 2° 17’ 10° 59’
6 Sudano-Guinean Borgou South Tchaourou Monts Kouffé Forest 2° 08’ 9° 00’
7Borgou South Kalalé Three Rivers Forest 3° 19’ 10° 50’
8 Bassila Bassila Penessoulou Forest 1° 64’ 9° 21’
9 Zou Djidja Gbadagba Forest 2° 01’ 7° 57’
10 Guineo-Congolian Oueme Valley Zogbodomey Locoly Swamp Forest 2° 36’ 7° 10’
11 Plain Kétou Kétou-Dogo Forest 2° 60’ 7° 73’
12 Plain Houéyogbé Houéyogbé Forest 1° 85’ 6° 50’
13 Pobè Pobè Pobè Forest 2° 68’ 7° 07’
14 Coast Ouidah Ahozon Forest 2° 16’ 6° 37’
Figure 1.
T-Square sampling method
[tamarind trees (T); sampling
point (mi); distances labeled x
and y; planes labeled L and R;
region of interest (Ω,)] (adapted
from Diggle [29]).
T. indica in three ecological regions of Benin
Fruits, vol. 66 (2) 57
region. The lower number in the latter
region was due to the scarcity of tamarind
trees in that region. For consistency and to
make realistic comparisons, sampling was
limited to trees with a diameter at 1.3 m
above ground (D130) of at least 20 cm. Sam-
pled trees were measured for D130, total
height and crown diameter. Crown areas
were computed according to a method pub-
lished elsewhere [30]. For each fruit-bearing
tree, fruits were harvested and weighed
together.
To estimate fruit and pulp mass and
number of seeds per fruit, 30 fruits were
sampled per fruit-bearing tree as described
elsewhere [31]. After weighing, fruits were
oven-dried at 65 °C for 48 h to obtain dry
mass. Dried fruits were broken and the con-
tent extracted (pulp + seeds + fibers). Pulp
was removed by soaking in water. The
remainder (seeds and fibers) was oven-
dried at 65 °C for 48 h and weighed. Pulp
mass was computed as: dry mass of the fruit
minus dry mass of the remainder. Finally,
the number of seeds per fruit was also
counted.
Climatic data for over 30 years (1978–
2008) were obtained for each sampling site
within ecological regions from the World-
clim data [32].
2.5. Data analysis
For ethnoecological data, we computed
a response rate per question using the fol-
lowing formula [33]: F=[100×(S/N)],
where Sis the number of responses to a par-
ticular question and Nis the total number
of persons interviewed.
The density of T.indica in each phyto-
geographical district was calculated accord-
ing to the following formula [29]:
, where: λis
the estimate of the number of adult trees
(D130 10 cm) per km², mis the number of
sampling points, xiis the distance from the
ith point to the nearest tamarind (T1) tree,
yiis the distance between T1and its closest
neighbor (T2) in the opposite plane which
does not contain the ith sampling point, and
πis approximately equal to 3.14.
The distribution and abundance of
T. indica were then mapped using Arcview
software.
The mass of the pulp content (wp) in each
fruit was computed using the following for-
mula: wp =wPiwRi, where wp is the pulp
content of a fruit for a given tree; wPiis the
total dry mass of the fruit (i); and wRiis the
total dry mass of seeds, fibers and husk of
the fruit (i). Overall yield of pulp and
number of seeds of the sampled trees were
estimated based on total yield of fresh fruits
and mean values obtained for fresh mass
and dry mass of fruit.
The climatic index of Mangenot (IM),
which is a measure of water availability [27],
was computed for each sampled site as fol-
lows:
, where Pis the mean
annual rainfall (mm); MSis the mean rainfall
of dry months (rainfall less than 50 mm); nS
is the number of dry months; is the max-
imum of annual relative humidity (%) ; and
is the minimum of annual relative
humidity (%). This index provides a better
quantitative assessment of climatic condi-
tions than any single climatic variable and
was used here as the indicator of the envi-
ronmental conditions in each ecological
region [27].
Because productivity of fresh fruits and,
pulp and seed values were not normally dis-
tributed (Ryan-Joiner test of normality) [34],
the non-parametric test of Kruskal-Wallis
was applied to describe and compare the
three ecological regions. To investigate the
correlation between ecological conditions,
tree characteristics (D130, height, crown
area) and differences in tamarind produc-
tivity, a Standardized Principal Component
Analysis (PCA) was first performed on the
productivity traits of the species (pulp mass,
number of seeds per fruit, overall yield of
fruits and pulp, and number of seeds per
λm
π
-----1
x1
2
i1=
m
1
2
---y1
2
i1=
m
×
-----------------------------------------------
×=
I
M
P
100
---------MSU
X
++
nS 500
Un
---------+
--------------------------------------
=
Ux
Un
58 Fruits, vol. 66 (2)
B. Fandohan et al.
tree). The principal components obtained
from the PCA were then correlated with
D130, height, crown area of tamarind trees
and the climatic index of Mangenot using
Pearson’s correlation coefficient. This
method was used to avoid evident correla-
tion between the productivity traits of the
species that could bias the estimation of the
degree of link they have with the dendro-
metric and ecological parameters.
3. Results
3.1. Local perception on past
and present distribution of tamarind
All the respondents knew the species
because of their profession. From this sur-
vey, it appeared that except for the Yoruba
ethnic group, tamarind had no local name
within the Guineo-Congolian region
(table II). According to the respondents
from the Sudano-Guinean and Guineo-Con-
golian regions and all questioned Fulani
herders (78% of respondents), the current
distribution of the species is limited in the
south by the Sudano-Guinean region. How-
ever, the species was said to have totally dis-
appeared or to be fading out of some
locations where it used to be abundant due
to tree felling for urban construction and
agricultural purposes in that region (near its
borders with the Guineo-Congolian region).
Other human practices (debarking for med-
icine, pruning for fodder and fruit harvest)
were also mentioned as threats to the spe-
cies. In state districts within the Sudano-Gui-
nean region, local ethnic groups generally
associated tamarind trees with Fulani peo-
ple. Furthermore, in this region, Fulani peo-
ple still have the tendency to appropriate the
harvest from any tamarind, even if trees are
on farmers’ land. Tamarind fruits are impor-
tant for the Fulani as a laxative during tran-
shumance trips.
3.2. Characterization
of the distribution patterns
and abundance of tamarind
Tamarind is widespread in Benin (fig-
ure 2). It was identified in all state districts
except those in the phytogeographical dis-
trict of Oueme-valley. However, as sug-
gested by the survey on local ecological
knowledge, tamarind trees are extremely
rare in the native vegetation within the
Guineo-Congolian region. Observed trees
were reported to have been planted 20-
60 years ago. On the other hand, in the
Sudanian and Sudano-Guinean regions,
tamarind stands (with gregarious patterns of
trees) were only found along water courses
in gallery forests. Beyond gallery forests, the
species was observed as isolated individuals
and was sometimes shrub-shaped in open
savannah ecosystems.
Density of tamarind adult trees declined
from the Sudanian region (approximately
2 trees per km²) to the Guineo-Congolian
region (totally absent) (figure 2). Based on
the densities obtained, estimation of tama-
rind adult tree abundance per phytogeo-
graphical district was estimated (table III).
The overall number of tamarind adult trees
in Benin was estimated at 68,114 trees,
meaning approximately an average of
0.6 trees per km² for the whole country.
Table II.
Tamarind local names according to ethnic groups in Benin.
Ecological region Ethnic group Names
Sudanian Bariba Môkôssô - Môhôhô
Dendi Bobosséi - Bosséi
Fulani Djêtami
Gourmantché Bu pugubu
Waama Pusika
Sudanian-Guinean Agnin Gougnémou
Fon Djêvivi
Idatcha Arinran
Nago Kaïma
Tchabè Adjagbon
Guineo-Congolian Adja
Holi –
Ouémè –
Péda –
Xwla –
Yoruba Adjagbon
T. indica in three ecological regions of Benin
Fruits, vol. 66 (2) 59
Figure 2.
Distribution patterns and
density of tamarind according
to the phytogeographical
subdivision of the three
ecological regions of Benin.
60 Fruits, vol. 66 (2)
B. Fandohan et al.
3.3. Estimating tamarind productivity
of fresh fruit, pulp and seeds
according to ecological regions
Significant differences were observed
among ecological regions for individual fruit
and pulp mass, and number of seeds per
fruit (p< 0.001; H = 314.96; H= 216.99 and
H = 35.57, respectively; table IV). Fruits
from the Guineo-Congolian region had the
highest values for fruit and pulp mass and
number of seeds per fruit. In contrast, no sig-
nificant differences were found between
ecological regions regarding overall yields
in fruits, pulp and number of seeds per tree
(p= 0.05; H = 1.79; H = 3.55; H = 2.57,
respectively). However, the coefficients of
variation (cv) suggested considerable tree-
to-tree variation for the majority of the inves-
tigated variables (table IV).
Table III.
Abundance of tamarind according to the phytogeographical districts within three ecological regions of Benin.
Ecological region Phytogeographical district Area
(km²)
Density
(trees·km–2)
Abundance1
(trees)
Sudanian Atacora Chain 6,905.46021 0.25 1,726.365
Mekrou-Pendjari East 10,579.0816 2.04 21,581.326
Mekrou-Pendjari West 6,261.25419 2.04 12,772.959
Borgou North 32,676.6419 0.51 16,665.087
Sudano-Guinean Borgou South 9,599.48146 0.15 1,439.922
Bassila 24,726.4271 0.50 12,363.214
Zou 10,431.6667 0.15 1,564.750
Guineo-Congolian Plain-East 2,071.22318 Very rare
Plain-West 5,098.4805 Very rare
Coast 686.07915 Extremely rare
Pobé 1,613.20103 Extremely rare
Oueme Valley 1,973.0031 Absent
1Abundance = area × density.
Table IV.
Mean and coefficient of variation of yields of fruits, pulp and seeds of tamarind according to their location in one
of the three ecological regions in Benin.
Ecological
region
Fruit mass Pulp mass per fruit Number of seeds per
fruit
Fruit yield per tree Pulp yield per tree Seed yield per tree
Mean
(g)
Coefficient
of variation
(%)
Mean
(g)
Coefficient
of variation
(%)
Mean Coefficient
of variation
(%)
Mean
(kg)
Coefficient
of variation
(%)
Mean
(kg)
Coefficient
of variation
(%)
Mean Coefficient
of variation
(%)
Sudanian 11.29 40.57 4.1 51.22 8.12 28.20 34.42 46.19 12.39 40.07 24758 45.18
Sudano-
Guinean
17.54 37.69 5.51 45.55 7.68 31.51 39.07 125.75 12.89 105.62 20550 125.76
Guineo-
Congolian
48.85 26.64 14.59 30.23 9.73 20.76 74.73 94.53 22.42 91.16 14889 89.01
Significance1< 0.0001 < 0.0001 < 0.0001 0.41 0.26 0.049
1According to the Kruskal-Wallis non-parametric test.
T. indica in three ecological regions of Benin
Fruits, vol. 66 (2) 61
The Principal Component Analysis (PCA)
performed on productivity characteristics
showed that the first two axes explained
85.83% of the observed variations in fruit
and pulp mass and number of seeds
(table V). The first axis is the productivity
axis; it shows a positive relationship with
and between all the productivity character-
istics. The correlation between this axis and
the dendrometric and ecological parame-
ters shows a relatively significant and posi-
tive correlation between IM(the climatic
index of Mangenot, which is a measure of
water availability) and productivity charac-
teristics. This means that fruit and pulp
mass, number of seeds per fruit, and overall
yield of fruits, pulp and number of seeds
per tree increased with higher IMvalues
(i.e., wetter regions). Correlation between
the first axis component of the PCA and
D130, height and crown area were not sig-
nificant (P> 0.05) and cannot be used here
to explain the observed variations. The sec-
ond axis did not take into account produc-
tivity traits of T. indica species and was not
used to assess and describe the link
between productivity of the species and the
dendrometric and ecological parameters.
4. Discussion
Our findings provide insight into the
effect of ecological conditions on the distri-
bution, abundance and productivity of tam-
arind. They also reflect the effect of human
disturbance on its distribution. The nonex-
istence of local names for the species in
some ethnic groups suggests a very recent
contact with the species and thus its very late
migration to their locations. This matches
the hypothesis which assumes the species
to have a dry ecosystem origin and suggests
its very late introduction into humid regions.
By contrast, the affinity of the species for
water courses (gallery forests) suggests that
habitats with less arid conditions better suit
its establishment and expansion. The pre-
cise origin of T .indica is still under debate.
Remnants of orchards dating back from
400 BC are known from Egypt [35], but Bud-
dhist scriptures refer to it as 650 BC [21]. What
is broadly accepted is that the species have
a tropical African, Madagascarian and Asian
origin [22]. Considering biogeographical
regions in Africa, tamarind is most common
in the Sahelian and the Sudanian ecological
regions [25]. Nonetheless, it is established in
Table V.
Correlation between productivity characteristics, tree-level and ecological parameters of
tamarind trees in Benin, and the axes 1 and 2 of Principal Component Analysis factors
(in brackets is the proportion of variation explained by each axis, expressed in
percentage).
Characteristics Axis 1
(73.93%)
Axis 2
(11.9%)
Fruit yield per tree 0.954 -0.243
Pulp yield per tree 0.937 -0.322
Seed yield per tree 0.686 -0.409
Fruit mass 0.745 0.320
Pulp mass per fruit 0.669 0.23
Number of seeds per fruit 0.544 0.139
Diameter at 1.3 m above ground (D130) 0.023 -0.400*
Height 0.257 -0.307
Crown area 0.318 -0.367
Climatic index of Mangenot (IM) 0.534** 0.531**
** significant at p< 0.01.
62 Fruits, vol. 66 (2)
B. Fandohan et al.
more humid zones and in coastal regions
[36]. Hypotheses have assumed that the cli-
matic variation observed from 20,000 to
10,000 Before Present and from 2,800 to
2,000 Before Present [37], and the subse-
quent replacement of dense forests of Equa-
torial Africa by savannah landscapes might
have allowed the natural establishment of
some savannah tree species (i.e., Adansonia
digita L., Vitellaria paradoxa C.F. Gaertn.,
Borassus aethiopum Mart.) within zones of
higher rainfall [7]. The latter authors have
also suggested that high density of these
species within the highest rainfall zone of
Benin may have to do with the Dahomey
Gap phenomenon which dried the humid
green forest block. But tamarind might have
colonized these regions before those climate
change periods. During the last two dec-
ades, scientific interest has increased in the
Holocene vegetational history of West Africa
[38–40], and the Dahomey gap in Benin
more specifically [41]. However, none of
these studies, including studies in areas
where tamarind is currently found, have
mentioned T. indica, suggesting a very late
migration of the species. This overlaps with
our results on local ecological knowledge.
However, the absence of T. indica from
paleobotanical findings might be linked to
its erratic occurrence at very low frequen-
cies, which might result in a large under-rep-
resentation compared with other taxa. In
addition, considering that tropical trees are
often ecologically highly plastic (at least
within the tropics), their natural distribution
may rather be strongly correlated to their
natural dispersion strategies than local var-
iation in environmental conditions. The cor-
relation between spatial patterns of plant
species and their dispersion strategies has
been highlighted [42]. Since tamarind is a
zoochorous species (monkeys and humans
are its natural dispersal agents), its distribu-
tion out of its native areas might be linked
to monkey and human migrations. It has
been illustrated that gene flow related to
Fulani migrations might explain the low
inter-population genetic diversity noticed
within tamarind populations in West Africa
[21]. The prevalence of some economically
important tree species in the savannahs of
Africa north of the equator, combined with
paleobotanical and historical evidence, are
strong indicators of human involvement in
tree dispersal [43]. However, Fulani herders’
passings (i.e., transhumance) are very recent
in some Sudano-Guinean localities where
natural and very old tamarind trees were
observed, and thus transhumance cannot
explain the presence of these trees (Sinsin,
pers. commun.). The contribution of human
migrations to the distribution of T. indica
may be addressed through the study of the
pattern of lineages among the species’ pop-
ulations across the main migration corridors,
using chloroplastic DNA analyses [21]. With
regard to the observed gregarious pattern of
tamarind trees along water courses (i.e., gal-
lery forests), two questions may need to be
further addressed: which are the factors or
events underlying the affinity of a species
typical of arid lands for wetter habitats (e.g.,
gallery forests)? Was the paleo-climate
which favored the establishment of the spe-
cies wetter than the current climate it is fac-
ing? And, in the case of a positive answer,
how far could the adaptability of the species
allow its persistence in arid ecosystems?
The findings from this study confirmed
the species’ erratic distribution in Benin. The
marked reduction of tamarind tree density
between phytogeographical districts within
the Sudanian and the Sudano-Guinian
regions might be due to tree felling and mor-
tality of natural regeneration caused by field
burning for agricultural purposes. The nat-
ural range of the species (especially in the
phytogeographical districts of Borgou North
and Borgou South, as well as Zou) is char-
acterized by extensive agriculture such as
cotton (Gossypium spp.) production. In
addition, according to our field surveys, in
Borgou South and Zou the species is less
important to the people except for the
Fulani tribes. Thus, tamarind trees were not
spared when land was cleaned for agricul-
tural purposes. Though it is frequently
observed on hillsides, tamarind was found
in low density in landscapes dominated by
hills and mountains such as the phytogeo-
graphical districts of the Atacora chain and
partly that of Zou. This observation contrasts
with findings on baobab trees [7] and may
be linked to the preference of tamarind for
well-drained and deep soils [17]. Three rea-
sons may explain the presence of tamarind
on hillsides: (i) tamarind seeds might have
T. indica in three ecological regions of Benin
Fruits, vol. 66 (2) 63
been disseminated by monkeys; and/or (ii)
when dry periods start, hillsides have plen-
tiful grass plants and are ideal pasture lands
for cattle, so Fulani herders might have dis-
seminated tamarind seeds while roaming
with their cattle; (iii) cattle might also have
contributed to the species' dispersion since
they also feed on its fruits.
Productivity (fruit and pulp mass, and
number of seeds per fruit) of tamarind trees
significantly varied with ecological condi-
tions. This is consistent with other studies
that have shown that environmental varia-
bles can affect fruit size and shape, and ker-
nel mass [7, 38]. However, estimated overall
fruit yields per tree did not significantly dif-
fer across ecological regions, suggesting that
tamarind trees may tend to invest in a small
number of very large fruits under wetter
conditions and a very large number of small
fruits under dryer conditions.
Fresh fruit yield per tamarind tree in this
study was 3 to 6 times lower than the figure
in East Africa [(150 to 300) kg] [36]. Produc-
tivity, including overall fruit yield per tree,
was weakly correlated to tree-level factors
(diameter, height and crown area) and the
results did not show a linear increase in pro-
ductivity with tree size, in contrast with
other studies [44, 45]. However, a positive
correlation was observed with the climatic
index of Mangenot (IM), suggesting produc-
tivity to be relatively higher under more
humid conditions. Successful fruiting in one
year is often followed at the cost of vegeta-
tive growth and some woody plants alter-
nate supra-annual schedules of low and
high production years [46]. This may explain
the high tree-to-tree variation revealed by
the coefficients of variation (cv). It can also
explain why some trees with greater diam-
eter or crown area showed very low fruit
yield. This also provides strong evidence
that ecological conditions which are much
less variable than production itself are not
the only determinants of variation in tama-
rind productivity [47]. For example, disease,
herbivores, adverse weather such as high-
speed winds, particularly during key phe-
nological events such as pollination or fruit
development, seasonal fire [48], and severe
pruning can reduce yield [49]. Variation in
productivity may also reflect genetic differ-
ences [50]. In addition, because tree produc-
tivity may greatly fluctuate with time, a
single census study can hardly provide an
accurate estimation. Besides, the results on
seed production irrespective of ecological
regions indicate that the often observed lack
of regeneration in the species' populations
is not driven by lack of seed production.
Other factors such as insect feeding pressure
on seeds and soil degradation and vegeta-
tion fire could be involved.
5. Conclusion
Our study has highlighted the difficulty in
understanding the current distribution of
tamarind and the need for greater research
on this topic. It has also provided useful pre-
liminary information on the variation in fruit
yield in tamarind. Savannah landscapes
where natural populations of the species
exist (i.e., the phytogeographical districts
within the Sudanian and the Sudano-Guin-
ean regions) are obviously suitable for tam-
arind plantation. However, the affinity of the
species for gallery forests elicits further inter-
est in its capacity to survive the increasing
drought stress in its current ecological range.
Multi-year census studies are needed to con-
sistently model the impact of environmental
characteristics (including soil characteris-
tics), dendrometric characters, genetic vari-
ation and human harvesting pressure
(pruning) on the inter-annual variation in
fruit yield in order to understand the species’
productivity better.
Acknowledgments
This study was supported by Domestica-
tion and Development of Baobab and Tam-
arind (EU-DADOBAT project). We
especially thank Patrick Van Damme for
comments on an earlier version of the man-
uscript. We are very grateful to the Fulani
herders, local hunters and healers for their
help during the field survey and the anon-
ymous reviewers for their useful comments
on improving the manuscript.
64 Fruits, vol. 66 (2)
B. Fandohan et al.
References
[1] Leakey R.R.B., Simons A.J., The domestica-
tion and commercialization of indigenous
trees in agroforestry for the alleviation of
poverty, Agrofor. Syst. 38 (1998) 165–176.
[2] Kouyaté A.M., Van Damme P., Caractères mor-
phologiques de Detarium microcarpum Guill.
et Perr. au sud du Mali, Fruits 57 (2002) 231–
238.
[3] AtanganaA.R., Ukafor V., Anegbeh P., Asaah E.,
Tchoundjeu Z., Fondoun J-M., Ndoumbe M.,
Leakey R.R.B., Domestication of Irvingia
gabonensis: 2. The selection of multiple traits
for potential cultivars from Cameroon and
Nigeria, Agrofor. Syst. 55 (2002) 221–229.
[4] Leakey R.R.B., Shackleton S., du Plessis P.,
Domestication potential of marula (Scleroca-
rya birrea subsp. caffra) in South Africa and
Namibia: 1. Phenotypic variation in fruit
traits, Agrofor. Syst. 64 (2005) 25–35.
[5] Bouvet J-M, Kelly B., Sanou H., Allal F., Com-
parison of marker- and pedigree-based
methods for estimating heritability in an
agroforestry population of Vitellaria paradoxa
C.F. Gaertn. (shea tree), Genet. Resour. Crop
Evol. 55 (2008) 1291–1301.
[6] Ekué M.R.M., Gailing O., Finkeldey R., Transfe-
rability of Simple Sequence Repeat (SSR)
Markers developed in Litchi chinensis to Bli-
ghia sapida (Sapindaceae), Plant. Mol. Biol.
Rep. 27 (2009) 570–574.
[8] Leakey R., Fuller S., Treloar T., Stevenson L.,
Hunter D., Nevenimo T., Binifa J., Moxon J.,
Characterization of tree-to-tree variation in
morphological, nutritional and medicinal
properties of Canarium indicum nuts, Agro-
for. Syst. 73 (2008) 77–87.
[7] Assogbadjo A.E., Sinsin B., Codjia J.T.C., Van
Damme P., Ecological diversity and pulp,
seed and kernel production of the baobab
(Adansonia digitata) in Benin, Belg. J. Bot.
138 (1) (2005) 47–56.
[9] Schlichting C.D., Pigliucci M., Phenotypic evo-
lution: a reaction norm perspective, Sinauer
Assoc., Sunderland, Mass., U.S.A., 1998.
[10] Gaoue O.G., Ticktin T., Impacts of bark and
foliage harvest on Khaya senegalensis
(Meliaceae) reproductive performance in
Benin, J. Appl. Ecol. 28 (2008) 34–40.
[11] Diggle P.J., Robust density estimation using
distance methods, Biometrika 62 (1) (1975)
39–48.
[12] Young L.J., Young, H., Statistical ecology: a
population perspective, Kluwer Acad. Publ.,
Boston, U.S.A., 1998.
[13] Diggle P.J., Besag J., Gleaves J.T., Statistical
analysis of spatial point by means of distance
methods, Biometrics 32 (1976) 659–667.
[14] Gaoue O.G., Ticktin T., Fulani knowledge of
the ecological impacts of Khaya senegalensis
(Meliaceae) foliage harvest in Benin and its
implications for sustainable harvest, Econ.
Bot. 63 (3) (2009) 256–270.
[15] Maundu P.M., Ngugi G.W., Kabuye C.H.S.,
Traditional food plants of Kenya, Natl. Mus.
Kenya, Nairobi, Kenya, 1999.
[16] Eyog Matig O., Gaoué O.G., Dossou B.,
Réseaux "Espèces Ligneuses Alimentaire",
C. R. Prem. Réun. Réseau, 11–13 déc. 2000,
CNSF, Ouagadougou, Burkina Faso, Inst.
Int. Ressour. Phytogénét., 2002.
[17] El-Siddig K., Gunasena H.P.M, Prasad B.A.
Pushpakumara D.K.N.G., Ramana K.V.R.,
Vijayanand P., Williams J.T., Tamarind, Tama-
rindus indica L, Southampt., Cent. Underutil.
Crops, Southampt., U.K., 2006.
[18] Bowe C., Haq N., Quantifying the global envi-
ronmental niche of an underutilized tropical
fruit tree (Tamarindus indica) using herba-
rium records, Agric. Ecosyst. Environ. (2010)
doi:10.1016/j.agee.2010.06.016.
[19] Soloviev P., Niang T.D., Gaye A., Totte A.,
Variabilité des caractères physico-chimiques
des fruits de trois espèces ligneuses de
cueillette récoltés au Sénégal : Adansonia
digitata,Balanites aegyptiaca et Tamarindus
indica, Fruits 59 (2004) 109–119.
[20] Diallo B.O., Biologie de la reproduction et
évaluation de la diversité génétique chez une
légumineuse : Tamarindus indica L. (Caesal-
pinioideae), Univ. Montp. II, Sci. Tech. Lan-
guedoc, thèse, Montp., France, 2001.
[21] Diallo B.O., Joly H.I., Mckey D., Hossaert-
Mckey M., Chevallier M.H., Genetic diversity
of Tamarindus indica populations: Any clues
on the origin from its current distribution?,
Afr. J. Biotechnol. 6 (7) (2007) 853–860.
[22] Diallo B.O., Mckey D., Chevallier M-H., Joly
H.I., Hossaert-Mckey M., Breeding system
and pollination biology of the semi-domesti-
cated fruit tree, Tamarindus indica L. (Legu-
minosae: Caesalpinioideae): Implications for
fruit production, selective breeding, and
conservation of genetic resources, Afr. J.
Biotechnol. 7 (22) (2008) 4068–4075.
T. indica in three ecological regions of Benin
Fruits, vol. 66 (2) 65
[23] Diallo B.O., Joly H.I., McKey D., Hossaert-
McKey, M., Chevallier M.H., Variation des
caractères biométriques des graines et des
plantules de neuf provenances de Tamarin-
dus indica L. (Caesalpinioideae), Fruits 65 (3)
(2010 153–167.
[24] Fandohan B., Assogbadjo A.E., Glèlè Kakaï,
R., Sinsin, B., Van Damme P., Impact of habi-
tat type on the conservation status of tama-
rind (Tamarindus indica L.) populations in the
W National Park of Benin, Fruits 65(1) (2010)
11–19.
[25] White F., The vegetation of Africa, UNESCO
Paris, France, Nat. Resour. Res. 20 (1983)
1–356.
[26] Anon., Troisième recensement général de la
population et de l'habitation (RGPH-3),
Résultats définitifs : Caractéristiques géné-
rales de la population, Inst. Natl. Stat. Appl.
Econ. (INSAE), Cotonou, Bénin, 2003.
[27] Adomou C.A, Sinsin B., van der Maesen
L.J.G., Phytosociological and chorological
approaches to phytogeography: a meso-
scale study in Benin, Syst. Geogr. Plants 76
(2006) 155–178.
[28] Grais R.F., Coulombier D., Ampuero J., Lucas
M.E.S., Barretto A.T., Jacquier G., Diaz F.,
Balandine S., Mahoudeau C., Brown V., Are
rapid population estimates accurate? A field
trial of two different assessment methods,
Disasters 30 (3) (2006) 364–376.
[29] Diggle P.J., Statistical analysis of spatial point
processes, Second ed., Arnold, Lond., U.K.,
2003.
[30] Lamien N., Tigabu M., Guinko S., Oden P.C.,
Variations in dendrometric and fruiting cha-
racters of Vitellaria paradoxa populations
and multivariate models for estimation of
fruit yield, Agrofor. Syst. (2007) DOI 10.1007/
s10457-006-9013-x.
[31] Leakey R.R.B., Fondoun J.-M., Atangana A.,
Tchoundjeu Z., Quantitative descriptors of
variation in the fruits and seeds of Irvingia
gabonensis, Agrofor. Syst. 50 (2000) 47–58.
[32] Hijmans R.J., Cameron S.E., Parra J.L., Jones
P.G., Jarvis A., The WorldClim interpolated
global terrestrial climate surfaces, Vers. 1.3.,
http://biogeo.berkeley.edu/, 2004.
[33] Kouyaté A.M., Aspect ethnobotaniques et
étude de la variabilité morphologique, biochi-
mique et phénologique de Detarium micro-
carpum Guill et Perr. au Mali, Univ. Ghent,
Thèse, Ghent, Belg., 2005.
[34] Ryan T.A., Joiner B.L., Normal probability
plots and tests for normality: technical report,
Univ. Park, Stat. Dep., Pa. State Univ., State
Coll., Pennsylvania, U.S.A., 1976.
[35] Aubréville A., Flore forestière soudano-gui-
néenne, AOF-Cameroun-AEF, Soc. Ed. ,
Marit. Colon., Paris, France, 1950.
[36] Jama B.A., Mohamed A.M., Mulatya J., Njui
A.N., Comparing the ‘‘Big Five’’: A fra-
mework for the sustainable management of
indigenous fruit trees in the drylands of East
and Central Africa, Ecol. Indic. 8 (2) (2008)
170–179.
[37] Maley J., Brenac P., Vegetation dynamics,
palaeoenvironments and climatic changes in
the forests of West Cameroon during the last
28,000 years, Rev. Palaeobot. Palynol. 99
(1998) 157–188.
[38] Salzmann U., Waller M., The Holocene vege-
tational history of the Nigerian Sahel based
on multiple pollen profiles, Rev. Palaeobot.
Palynol. 100 (1998) 39–72.
[39] Salzmann U., Are savannas degraded
forests? A Holocene pollen record from the
Sudanian zone of NE Nigeria, Veg. Hist.
Archaeobot. 9 (2000) 1–15.
[40] Salzmann U., Hoelzmann P., Morczineck I.,
Late Quaternary climate and vegetation of
the Sudanian zone of NE Nigeria, Quat. Res.
58 (2002) 73–83.
[41] Salzmann U., Hoelzmann P., The Dahomey
gap: An abrupt climatically induced rain forest
fragmentation in West Africa during the late
Holocene, Holocene 15 (2) (2005) 190–199.
[42] Collinet F., Essai de regroupement des princi-
pales espèces structurantes d’une forêt
dense humide d’après l’analyse de leur répar-
tition spatiale (Forêt de Paracou-Guyane),
Lab. Biom., Génét. Biol. Popul., UMR CNRS
5558, Group. Intérêt Sci. Sylvolab, Guyane,
France, 1997.
[43] Maranz S., Wiesman Z., Evidence for indige-
nous selection and distribution of the shea
tree, Vitellaria paradoxa, and its potential
significance to prevailing parkland savanna
tree patterns in sub-Saharan Africa, north of
the equator, J. Biogeogr. 30 (2003) 1505–
1516.
[44] WadtL.H.O., Kainer K.A., Gomes-Silva D.A.P.,
Population structure and nut yield of Berthol-
letia excelsa stand in southwestern Amazo-
nia, For. Ecol. Manag. 211 (2005) 371–384.
[45] Zuidema P.A., Boot R.G.A., Demography of
the Brazil nut tree (Bertholletia excelsa) in the
T. indica in three ecological regions of Benin
Fruits, vol. 66 (2) 66
Bolivian Amazon: Impact of seed extraction
on recruitment and population dynamics, J.
Trop. Ecol. 18 (2002) 1–31.
[46] Kelly D., Sork V.L., Mast seeding in perennial
plants: why, how, where?, Annu. Rev. Ecol.
Evol. Syst. 33 (2002) 427–447.
[47] Koenig W.D., Knops J.M.H., Patterns of
annual seed production by Northern Hemis-
phere trees: a global perspective, Am. Nat.
155 (2000) 59–69.
[48] Stephenson A.G., Flower and fruit abortion:
Proximate causes and ultimate functions,
Annu. Rev. Ecol. Evol. Syst. 12 (1981)
253–279.
[49] Ghosh S.N., Bera B., Kundu A., Roy S., Dutta
Ray S.K., Fruit production and quality impro-
vement in aonla (Emblica Officinalis Gaertn.)
through canopy management, J. Agric. Tech-
nol. 3 (8) ser. n°21 (2009) 40–43.
[50] Assogbadjo A.E., Kyndt T., Sinsin B., Gheysen
G., Van Damme, P., Patterns of genetic and
morphometric diversity in Baobab (Adanso-
nia digitata) populations across different cli-
matic zones of Benin (West Africa), Ann. Bot.
97 (2006) 819–830.
Benin / Tamarindus indica / distribución de la población / densidad de la
población / ructificación/ conocimiento indígena
... This land-use change has had a serious impact on the Tamarind tree population, because it depends on natural regeneration [16]. Furthermore, the available information generally lacks adequate quantitative analysis for the development of economic opportunities based on local resources such as Tamarind trees as an alternative to excessive import of exotic products [17]. Although some studies have been undertaken to investigate the fruit, morphological characteristics, and use of Tamarind in different localities in Ethiopia [14,16], the species is still inadequately characterized. ...
... Although fruit yield varies seasonally, the number of fresh fruit and the yield per Tamarind tree on farmland was 42% and 64% higher, respectively, than that in bushland. Although the seasonal variation of the yield is usually related with the environmental conditions, the effect may vary with plant species [17]. These results are consistent with the findings of other studies that wild edible trees on farms produce more fruit than unmanaged trees in woodlands [44,45]. ...
... Such significant differences in fruit yield under different land-use types might be attributable to differences in environmental variables, such as soil type, landforms, and moisture content [46]. For example, the study on fruit production of T. indica across three different ecological regions in Benin indicated that Tamarind trees tend to invest in a small number of very large fruits under wetter conditions and a very large number of small fruits under dryer conditions, indicating the effect of ecological conditions such as temperature and rainfall on the productivity of Tamarind fruits [17]. The level of tree management on farmland has also been reported to significantly influence the degree of competition among trees for available resources such as nutrients [45] and, thus, the productivity of trees in terms of fruit weight and size [44]. ...
Article
Full-text available
In this study, we evaluated stand status, dendrometric variables, and fruit production of Tamarind (Tamarindus indica L.) trees growing in bushland and farmland-use types in dryland areas of Ethiopia. The vegetation survey was conducted using the point-centered quarter method. The fruit yield of 54 trees was also evaluated. Tree density and fruit production in ha were estimated. There was a significant difference in Tamarind tree density between the two land-use types (p = 0.01). The mean fruit yield of farmland trees was significantly higher than that of bushland trees. However, Tamarind has unsustainable structure on farmlands. Differences in the dendrometric characteristics of trees were also observed between the two land-use types. Predictive models were selected for Tamarind fruit yield estimations in both land-use types. Although the majority of farmland trees produced <5000 fruit year−1, the selection of Tamarind germplasm in its natural ranges could improve production. Thus, the development of management plans to establish stands that have a more balanced diameter structure and thereby ensure continuity of the population and fruit yields is required in this area, particularly in the farmlands. This baseline information could assist elsewhere in areas that are facing similar challenges for the species due to land-use change.
... and Parinari curatellifolia Planch. ex Benth. in Burkina Faso, Sanogo et al. (2015) on Adansonia digitata L. in Senegal, Assogbadjo et al. (2005a;2005b) on A. digitata, Fandohan et al. (2011) on Tamarindus indica L. and Dicko et al. (2019) on Lophira lanceolata Tiegh. ex Keay in Benin. ...
... In efforts to enhance the species' genetic resource conservation and utilization, it has recently been identified as one of the top ten agroforestry tree species to be prioritized for future crop diversification programs and development in sub-Saharan Africa. However, little scientific information is available on how ecological conditions locally influence its distribution, abundance and productivity in Africa (Fandohan et al. 2011). ...
Chapter
Full-text available
Non-Timber Forest Products (NTFPs) designate goods of biological origin other than timber from natural, modi ed or managed forested landscapes. A number of short cycle and cultivated species contributing to food security that remain traditional tend to get less research attention, training and extension. Such plant resources are termed Orphan Crops (OCs), also referred to as minor crops. Due to the increased demands, harvest/ collection of minor crops has tremendously escalated threat of biodiversity loss. Besides, the increased market value of minor crops and their importance in improving livelihood of people in the rural areas raises the need of sustainable management of those crops, which entails e orts toward domestication, selection and improvement. This chapter presents the methods and principles for the genetic improvement of Non- Timber Forest Products & Orphan Crops. It established a 7 steps general roadmap for breeding minor crops. The exercise begins with appropriate goals setting, then germplasm is gathered through collection missions, followed by their morphological and molecular characterization, to provide basic information of lines and guide choice of parental lines. It is very common to encounter narrow genetic base in minor crops. This is dealt with by creating new variants through massive hybridization and more speedily, using mutagenesis. Hybridization has got many designs that serve various purposes, also selection methods are diverse. In case of low inherited traits, the detection of Quantitative Trait Loci (QTL) that set prospects for marker-assisted selection (MAS) has been emphasized. Also, newer breeding tools such as genome-wide association studies (GWAS) and genomic selections (GS) have been discussed. Keywords: Hybridization, Genetic improvement, Marker-assisted selection, Mutation, Orphan Crops
... and Parinari curatellifolia Planch. ex Benth. in Burkina Faso, Sanogo et al. (2015) on Adansonia digitata L. in Senegal, Assogbadjo et al. (2005a;2005b) on A. digitata, Fandohan et al. (2011) on Tamarindus indica L. and Dicko et al. (2019) on Lophira lanceolata Tiegh. ex Keay in Benin. ...
... In efforts to enhance the species' genetic resource conservation and utilization, it has recently been identified as one of the top ten agroforestry tree species to be prioritized for future crop diversification programs and development in sub-Saharan Africa. However, little scientific information is available on how ecological conditions locally influence its distribution, abundance and productivity in Africa (Fandohan et al. 2011). ...
... La figure 3 indique les pays africains où il est observé à l'état naturel. En dépit de son absence à l'état naturel du centre d'endémisme Guinéo-Congolais plus arrosé, l'espèce a une plus forte capacité de régénération et une plus forte densité en forêts galeries ou en bordure de rivière à travers toute son ère de distribution en Afrique et à Madagascar (Fandohan et al., 2011b;Mojeremane et Tshwenyane, 2004 ;Blumenfeld-Jones et al., 2006). Cette attraction pour les milieux humides sous climat sec pourrait suggérer des inquiétudes quant à sa capacité à s'adapter aux changements climatiques. ...
Article
Full-text available
Tamarindus indica is an agroforestry fruit species very popular in Africa and Asia. This review aimed to document the contributions and the gaps of research efforts on the species, in order to identify the research prospects. Literature search was carried out with the search engine and database “Google Scholar” and AGORA on the basis of the Latin name “Tamarindus indica” over a period of 25 years. Analysis of the literature showed that T. indica is widely exploited for its food and medicinal uses, mainly. It constitutes a cash crop in Asia while it is still undervalued in Africa. A considerable amount of research has focused on ecology, the structure of natural populations, pests and the chemical properties of its organs. Domestication and sustainable use of this species in Africa demand further research endeavors in silviculture, ecological genetics and phytopathology. This would facilitate integration of tamarind into formal production and conservation policies.
... To date, no prior study on shea morphotype abundance had been conducted. For Fandohan et al. [39], rural communities' knowledge on Tamarindus' ecological range was congruent with scientific findings. This is why there is a crucial need to fill the gap for the shea tree to better understand the factors that influence this state of affairs which should meet farmers' preferences. ...
Article
Full-text available
Trait diversity is crucial in undertaking the domestication of useful species such as Vitellaria paradoxa which makes a significant contribution to the rural household economy in Africa. This study aims to document the criteria farmers use to distinguish shea trees; how they vary according to age, education level and sociolinguistic group; and their perception of trees’ abundance and production. We surveyed 405 respondents across shea parklands in Benin using a semi-structured questionnaire. We used the Kruskal-Wallis test to evaluate the influence of sociodemographic attributes on relative criteria citation frequency and principal components analysis to characterize farmers’ perception on morphotypes’ abundance, fruits, and butter yields. The five most cited criteria were fruit size (55.5%), tree fertility (15.40%), bark colour (10.51%), timing of production (5.38%), and pulp taste (3.42%). The citation frequency of criteria varied significantly depending on the sociodemographic factors considered. Trees having small fruit (‘Yanki’) were reported to be widespread and high fruit/nuts and butter producers. Farmers perceived five important traits with variable importance depending on the sociocultural factors studied. This finding is a key step toward the development of a shea improvement program that could focus on the morphotype Yanki reported to potentially be a high fruit and butter producer.
... Indigenous and local knowledge may also serve as inspiration for conventional science. It is often perceived as locally superior, drawing on the collective experience of many generations, for example, where traditional fishers have a better understanding of the abundance or migratory patterns of certain fish species than scientists (Berg Hedeholm et al., 2016;Jauharee et al., 2021) or local knowledge about the location of plants and fruits may help ecologists to identify the ecological range of species (Fandohan et al., 2011). That said, the potential to integrate indigenous knowledge into environmental policy and management is frequently missed (Hanspach et al., 2020) and it is also necessary to acknowledge that there is disagreement in the literature about whether indigenous and local knowledge is an accurate representation of ecological data, and/or always translates into more sustainable management and conservation (see e.g. ...
Article
Full-text available
Globally, the importance of indigenous and local knowledge systems for science, policy, environmental conservation and the cultural heritage of indigenous peoples is increasingly being recognised. The Amazon region in particular is home to many indigenous peoples who have conserved their cultural traditions and knowledge, despite growing threats to the environment and traditional lifestyles and cultures. Based on insights from ethnographic research in three indigenous communities, here we present a case study on the indigenous knowledge of the Urarina people of the Chambira Basin in the Peruvian Amazon and its implications for conservation. We describe, for the first time, a series of anthropomorphic and territorial "wetland spirits", who are associated with particular wetland ecosystems and range in character from the benign to outright aggressive. Their presence may indirectly benefit conservation of wetlands, as humans fear or respect these wetland spirits and adapt their behaviour accordingly. While benign spirits may be seen as positive models to follow, aggressive spirits may deter unsustainable harvesting of resources through fear of disease or death. However, their cultural status is not adequately captured by such rational-scientific explanations. Wetland spirits are important characters within the indigenous cosmos of humans and non-humans, which is built on a relational, rather than extractive model of connecting humans and nature. We discuss our findings in the context of wider conceptual debates on recognising relational ontologies in environmental policy and conservation, the paradigm of biocultural conservation, as well as their implications for land titling, and incorporating indigenous perspectives in local education.
... To date, no prior study on shea morphotypes abundance had been conducted. Since rural communities' knowledge on Tamarindus' ecological range was congruent with scienti c ndings [47], then, there is a crucial need to ll this gap to better understand factors that in uence this state of affairs which should meet farmers' preferences. In addition, perceptions were scattered among farmers about this morphotype' fruit production which can be high, medium and sometimes very low. ...
Preprint
Full-text available
Background: Local knowledge and perception are crucial to undertake the domestication of useful species such as Vitellaria paradoxa that makes significant contribution to rural household economy in Africa. This study aims to document shea morphotypes diversity based on folk knowledge especially the main criteria farmers used to distinguish shea trees and to examine the influence of sociodemographic characteristics on that knowledge. Methods: 405 respondents were surveyed across shea parklands in Benin using semi-structured questionnaire. We used the relative citation frequency of criteria followed by Kruskal-Wallis test to evaluate the influence of sociodemographic attributes on local knowledge of Shea morphotypes variation. Factorial Correspondence Analysis described the links between the different morphotypes and parklands, and Principal Components Analysis was used to characterize farmers perception on morphotypes’ abundance, fruits and butter yields. Results: Respondents identified 13 morphotypes based on the five most cited criteria which are fruit size (55.5%), tree fertility (15.40%), bark colour (10.51%), timing of production (5.38%) and pulp taste (3.42%). The citation frequency of classification criteria varied significantly depending on the age, the education level and the sociolinguistic group of the respondent. The Bembèrèkè zone shea parkland revealed higher diversity of morphotypes traits. The small fruit type (‘Yanki’) was reported to be widespread. It produces higher fruit and butter yields according to respondents. Conclusions: From our findings, farmers perceived an important diversity of shea traits that are used to classify morphotypes with economic or sociocultural importance. The revelation of that natural variation in shea tree is a key step toward the development of shea improvement program that could focus on the morphotype Yanki reported to be potentially high in fruit production and butter yield.
... The rainfall ranges from 900 to 1300 mm with an average of 1200 mm while the annual temperature ranges between 25 and 39°C with an average of 28°C. The region experiences a relative humidity ranging between 69 and 97% [5,34], and dominant soil types include ferralitic and ferruginous soils. The Deciduous forest ecological zone (DF) in Ghana also has a bimodal rainfall pattern with an annual rainfall varying from 1200 to 1600 mm with an average of 1500 mm [35]. ...
Article
Full-text available
Background Understanding end-users’ preferred breeding traits and plant management practices is fundamental in defining sound breeding objectives and implementing a successful plant improvement programme. Since such knowledge is lacking for Synsepalum dulcificum , a worldwide promising orphan fruit tree species, we assessed the interrelationships among socio-demography, ecology, management practices, diversity and ranking of desired breeding traits by end-users of the species (farmers, final consumers and processing companies) in West Africa. Methods Semi-structured interviews, field-visits and focus groups were combined to interview a total of 300 farmers and final consumers belonging to six sociolinguistic groups sampled from three ecological zones of Benin and Ghana. One processing company in Ghana was also involved. Data collected included socio-demographic characteristics; crop management systems and practices; and preferences of farmers, final consumers and processing companies and ranking of breeding traits. Data were analysed using descriptive statistics, independence, and non-parametric tests, generalized linear models, multi-group similarity index and Kendall’s concordance coefficient. Results Men (86.33% of respondents) were the main holders of S. dulcificum in the study area. The three most frequent management practices observed in the species included weeding, fertilization and pruning, which were applied by 75.66%, 27.33% and 16.66% of respondents, respectively. The management intensity index varied significantly across ecological zones, sociolinguistic groups, and instruction level ( p < 0.001) but was not affected by gender ( p > 0.05). General multigroup similarity indices ( $$ {\mathrm{C}}_{\mathrm{S}}^{\mathrm{T}} $$ C S T ) for farmer-desired traits, on one hand, and final consumer-desired traits, on the other hand, were high across ecological zones ( $$ {\mathrm{C}}_{\mathrm{S}}^{\mathrm{T}} $$ C S T ≥ 0.84) and sociolinguistic groups ( $$ {\mathrm{C}}_{\mathrm{S}}^{\mathrm{T}} $$ C S T > 0.83). Nevertheless, respondents from the Guineo-Congolian (Benin) and the Deciduous forest (Ghana) zones expressed higher agreement in the ranking of desired breeding traits. Preference for breeding traits was 60% similar among farmers, final consumers, and processors. The key breeding traits desired by these end-users included in descending order of importance big fruit size, early fruiting, high fruit yielding (for farmers); big fruit size, high fruit miraculin content, fruit freshness (for final consumers); and high fruit miraculin content, big fruit size, high fruit edible ratio (for processing companies). Conclusion This study revealed stronger variations in current management practices across ecological zones than across sociolinguistic groups. A high similarity was shown in end-users’ preferences for breeding traits across the study area. Top key traits to consider in breeding varieties of S. dulcificum to meet various end-users’ expectations in West Africa include fruit size and fruit miraculin content. These results constitute a strong signal for a region-wide promotion of the resource.
... In efforts to enhance the species' genetic resource conservation and utilization, it has recently been identified as one of the top ten agroforestry tree species to be prioritized for future crop diversification programs and development in sub-Saharan Africa. However, little scientific information is available on how ecological conditions locally influence its distribution, abundance and productivity in Africa (Fandohan et al. 2011). ...
Chapter
Full-text available
There are several evidences of the prominent roles that non-timber forest products (NTFPs), and particularly wild edible fruit (WEF) play for human food security and poverty alleviation. Although neglected in the past, there are increasing interest on WEF species, and evaluation of their fruit production has become essential. Quantifying the fruit production of WEF species is important to assess their contribution to food security and poverty alleviation but also to plan their sustainable exploitation. In the last three decades, several studies have investigated the productivity of some WEF species. However, the methodological approaches are diverse and there is a need to provide guidelines particularly for early researchers interested by this research field. This chapter provides a methodological synthesis to serve as guidelines for students and researchers for a better assessment of the fruit production of WEF species. The chapter focuses on techniques for sampling, data collection and data analysis. Overall, three main aspects are often investigated across studies. These include (i) potential in fruit production, (ii) effects of abiotic factors such as soil, and climate on fruit production, (iii) relationships between morphological parameters of trees (e.g. diameter and height) and fruit production. Three main methodological approaches are used by researchers: the integral counting of fruits, the collection and counting of fruits fallen under the tree, and the estimation by extrapolation. Each of these approaches was presented and illustrated through a case study.
... In the study region, annual rainfall ranged from 750 to 1150 mm (lower Eastern) and 900-1000 mm (Coastal region) (Jaetzold et al. 2009) and is therefore not limiting baobab distribution. A study on tree densities of Tamarindus indica L. across three ecological regions in Benin showed declining tree densities from the dry Sudanian zone to the wetter Guinea-Congolian zone (Fandohan et al. 2011), while Jama et al. (2008 reported a better establishment of the species in more humid zones and coastal regions. This indicates that additional factors other than rainfall influenced the distribution of T. indica. ...
Article
Baobab (Adansonia digitata L.) is a multipurpose wild fruit tree of sub- Saharan Africa with unknown population demographic stability. This study assessed the baobab population structure in two main growing regions of Kenya where thirty-five plots (0.5 × 3 km each) were set in two transects, along road C107 in the coastal region and B9 in the lower Eastern Kenya, covering different agro-ecological zones (AEZs). For all baobabs within a plot, position, height and diameter at breast height (DBH) were recorded, stem densities calculated and DBH size-class distribution (SCD) curves developed. In total, 599 and 1351 baobab trees were recorded in the 14 and 21 plots in the Coastal and lower Eastern regions, respectively with densities of 0.285 (±0.07 S.E.) and 0.429 (±0.07 S.E.) stems/ha, respectively. The rather dry AEZ “Lower Midland 5” had a significantly higher density of mature (p = .047) and total trees (p = .028) than the other zones. However, at regional level (coast versus eastern), there were no significant differences in the densities of juvenile, mature or total baobab trees. Negative SCD slopes obtained in the two regions indicated more trees in the smaller size classes and hence good recruitment. The results indicated stable populations in general, but local communities should be encouraged to maintain existing trees and promote the establishment of young baobabs.
Chapter
Full-text available
New initiatives in agroforestry are seeking to integrate into tropical farming systems indigenous trees whose products have traditionally been gathered from natural forests. This is being done in order to provide marketable products from farms that will generate cash for resource-poor rural and peri-urban households. This poverty-alleviating agroforestry strategy is at the same time linked to one in which perennial, biologically diverse and complex mature-stage agroecosystems are developed as sustainable alternatives to slash-and-burn agriculture. One important component of this approach is the domestication of the local tree species that have commercial potential in local, regional or even international markets. Because of the number of potential candidate species for domestication, one crucial first step is the identification of priority species and the formulation of a domestication strategy that is appropriate to the use, marketability and genetic potential of each species. For most of these hitherto wild species little or no formal research has been carried out to assess their food value, potential for genetic improvement or reproductive biology. To date their marketability can only be assessed by their position in the local rural and urban marketplaces, since few have attracted international commercial interest. To meet the objective of poverty alleviation, however, it is crucial that market expansion and creation are possible, hence for example it is important to determine which marketable traits are amenable to genetic improvement. While some traits that are relatively easy to identify do benefit the farmer, there are undoubtedly others that are important to the food, pharmaceutical or other industries that require more sophisticated evaluation. This paper presents the current thinking and strategies of ICRAF in this new area of work and draws on examples from our program.
Article
SUMMARY Distance estimators of density may exhibit serious bias unless the population under consideration forms a completely random spatial pattern, i.e. the estimators are not robust. In this paper some new estimators are proposed, and their robustness is assessed analytically against two stochastic models, which together embrace a continuous range of spatial pattern, from extreme regularity, through randomness, to extreme aggregation.
Article
1: Probability Distributions.- 2: Goodness-of-Fit Tests.- 3: Models and Sampling.- 4: Sequential Estimation.- 5: Sequential Hypothesis Testing.- 6: Sequentially Testing Three Hypotheses.- 7: Aggregation and Spatial Correlation.- 8: Spatial Point Patterns.- 9: Capture-Recapture: Closed Populations.- 10: Capture-Recapture: Open Populations.- 11: Transect Sampling.- 12: Degree-Day Models.- 13: Life-Stage Analysis.- 14: Probit and Survival Analysis.- 15: Chaos.- References.
Article
Various distance based methods of testing for randomness in a population of spatially distributed events are described. Special emphasis is placed upon preliminary analysis in which the complete enumeration of the events within the study area is not available. Analytical progress in assessing the power of the techniques against extremes of aggregation and regularity is reviewed and the results obtained from the Monte Carlo simulation of more realistic processes are presented. It is maintained that the method of T square sampling can help to provide quick and informative results and is especially suited to large populations. Some comments on contiguous quadrat methods are made.
Article
Introduction. Adansonia digitata L., Balanites aegyptiaca (L.) Del. et Tamarindus indica L. figurent parmi les especes fruitieres de cueillette les plus appreciees par les populations sahelo soudaniennes. Leur role sur le plan nutritionnel et sur la generation de revenus est important. La degradation des ecosystemes constitue une menace sur la ressource en fruits de cueillette et sur la diversite genetique de ces especes. La premiere etape du programme de domestication mis en œuvre au Senegal consiste a en caracteriser la variabilite naturelle, dans le cadre d'une demarche participative visant la selection d'accessions interessantes pour la qualite des fruits. L'objet de cette etude a ete de comparer, pour chacune des especes, les fruits de differentes accessions. Materiel et methodes. Les analyses ont porte sur une caracterisation biometrique des fruits, completee par une analyse chimique sommaire (eau, sucres solubles totaux, acidite libre totale). Resultats et discussion. Pour la totalite des criteres etudies, l'exploitation des donnees a montre des differences significatives entre les accessions au sein de chaque espece. Pour les caracteres biometriques, un gradient decroissant de variabilite apparait selon la sequence: Adansonia vers Tamarindus vers Balanites. Le critere de « valeur reelle de la pulpe » a permis de cibler des accessions plus interessantes que d'autres. Les caracteres chimiques ont presente une moindre variabilite. Conclusions. Les differentes accessions etudiees presentent une variabilite exploitable pour la diffusion aux populations locales de varietes performantes d'especes fruitieres repondant a leurs besoins et a leurs moyens.
Article
Introduction. Detarium microcarpum est une espece fruitiere importante au sud du Mali. L'objectif du present travail a ete la caracterisation morphologique de certaines populations de D. microcarpum, qui serait un prealable necessaire a l'etude de la structure genetique de l'espece. Materiel et methodes. Les observations morphologiques ont concerne vingt-trois caracteres agronomiques etudies sur 25 arbres par peuplement de dix populations reparties sur l'ensemble du sud du Mali. Resultats et discussion. L'etude a montre qu'il existait une variabilite entre les populations, qui a porte sur les caracteres mesures chez le fruit, la graine et la feuille. Trois formes de fruits a maturite et une forme de graines ont ete identifiees. Conclusion. Les resultats obtenus ne permettent pas d'affirmer l'existence de varietes differentes au sein de l'espece D. microcarpum. L'etude devra donc etre elargie a l'observation d'autres caracteres et porter sur l'ensemble de l'aire de repartition de l'espece au Sahel.
Article
The lake Barombi Mbo pollen record goes back to about 28,000 yr B.P. The pollen diagram based on 82 samples is subdivided into four main pollen zones. Zone I (ca. 28,000 to 20,000 yr B.P.) is characterized by relatively high frequencies of Caesalpiniaceae and also by a montane element with Olea capensis. The climate was cool and relatively wet. Zone II (ca. 20,000 to 10,000 yr B.P.). A sharp increase in Gramineae, the main non-arboreal land pollen taxon, began around 20,000 yr B.P. and lasted until 10,000 yr B.P. During this period the forest receded, giving way to a more open vegetation, but significant patches of forest (refuges) persisted in the area. This is confirmed by isotopic analyses (δ13C of sedimentary detritic organic matter from the catchment. Until ca. 13,000 yr B.P. Olea capensis was well represented indicating a relatively cool climate. Between 13,000 and 12,000 yr B.P. a warming trend associated with a strong increase in precipitation occurred. After this an abrupt reduction in precipitation linked to an increase in seasonality, but without temperature lowering, intervened between ca. 11,500 and 10,400 yr B.P. This last phase corresponds partly to the Younger Dryas time period. Zone III (ca. 10,000 to 2800 yr B.P.). After ca. 10,400 yr B.P. the climate became very wet until ca. 3000 yr B.P. A sharp decrease in the Gramineae intervened at ca. 10,000 yr B.P.; from ca. 9500 to 3000 yr B.P. they remained very low, between 0 and 3%, and the forest trees reached their maximum extension. Most of the trees exhibited large variations with quasi-periods of around 1000 to mainly 2000 yr (ca. 2200 calendar years), which could be related to large sylvigenetic or successional cycles. In this zone the Caesalpiniaceae were relatively well represented, with a maximum extension between 4500 and 3000 yr B.P. Podocarpus, a typical tree of the montane stratiform cloud forests, exhibited very low frequencies before 10,000 yr B.P. but their relative increase during the early and middle Holocene can only be explained by its growth on distant mountains. Its maximum extension phase was roughly synchronous with that of Caesalpiniaceae. The climate was warm and wet, but cooler on the mountains. Zone IV (ca. 2800 yr B.P. to present time). Around 2800 yr B.P. a sharp increase in the Gramineae, peaking at 30 to 40% of total pollen between ca. 2500 and 2000 yr B.P., indicates a sudden phase of vegetation opening and forest retreat, accompanied by severe erosion. Alchornea, a typical pioneer taxon, increased rapidly at the same time to large frequencies because it develops abundantly in all the openings. Elaeis guineensis, originally a pioneer palm tree, follows the same pattern. The climate was warm, relatively dry, and linked to an increase of seasonality. After 2000 yr B.P. the Gramineae returned to low frequencies, around 10%, associated with a strong increase in trees, indicating that the forest expanded again but not to the same extent as in the early and middle Holocene. The climate was warm and relatively wet, rather similar to the present-day climate.
Article
Distance estimators of density may exhibit serious bias unless the population under consideration forms a completely random spatial pattern, i.e. the estimators are not robust. In this paper some new estimators are proposed, and their robustness is assessed analytically against two stochastic models, which together embrace a continuous range of spatial pattern, from extreme regularity, through randomness, to extreme aggregation.