1 ijfaf jan-2018-1-impact of wari-maro

International Journal of Forest, Animal and Fisheries Research (IJFAF) [Vol-2, Issue-1, Jan-Feb, 2018]
https://dx.doi.org/10.22161/ijfaf.2.1.1 ISSN: 2456-8791
www.aipublications.com Page | 1
Impact of Wari-Maro classified forest
management plan implementation on the
structure and specific diversity of vegetation
types in Benin (West Africa)
Gildas K. S. Mensah1
, Ousséni Arouna1&2*
, Ismaïla Toko Imorou1
, Omer A. B. Thomas1
,
Soufouyane Zakari1
1
Laboratory of Cartography, Department of Geography and Regional Planning, Faculty of Humanities and Social Sciences.
University of Abomey-Calavi. 01 BP 526 Cotonou, Benin, Email: mensahseverin1985@gmail.com
2
School of Sciences and Techniques of Building and Road (ESTBR), National University of Sciences, Technologies,
Engineering and Mathematics (UNSTIM), 03 BP 304 Abomey, Benin Abomey
Abstract— The participatory management plan is a
technical, legal and social device that joins the objectives
of biodiversity conservation and the socio-economic
needs of local populations. This research work aims to
evaluate the impact of Wari-Maro classified forest
management plan implementation on the structure and
specific diversity of vegetation types. The methodological
approach followed is based on the comparison of the
dendrometric parameters and plant diversity parameters
before and after the management plan implementation.
The phytosociological and dendrometric database before
the management plan was compiled with data from the
forest inventory conducted by PAMF project in 2004 and
others work. The forest and phytosociological inventories
were carried out on the plots (70) from the forest
inventory of PAMF project (2004) following the same
methodological principles. The Shannon diversity index
decreased from 3.35 ± 0.57 bits in 2004 to 1.98 ± 0.73
bits in 2014. The average density of dbh trees ≥ 10 cm
decreased from 740.37 ± 269 , 86 stems / ha in 2004 to
184 ± 100 stems / ha in 2014. The results of the 5%
sample matched t-test reveal a non-significant difference
between the Shannon Diversity Index of 2004 and of
2014. On the other hand, the results of the sample t-test
matched at the 5% threshold, reveal a significant
difference between the average density value of 2004 and
2014 for all vegetation types except shrub savannas,
fields and fallows. Most of the plant species found before
the management plan are still present despite the
decreased in individuals’ density.
Keywords— impact, inventories, management plan,
vegetation, Wari-Maro.
I. INTRODUCTION
Forests have ecological, environmental, socio-economic
and, of course, wood production functions, important not
only locally but also on a global scale (Djègo, 2006).
They cover 3.9 billion hectares or about one third of the
world's land area. Unfortunately, the forest ecosystems
are threatened by anthropogenic factors to meet the
population ever-increasing needs due to the population
growth (Fonton, 2006). For the conservation of the
world's forest heritage, the concept of sustainable
management was highlighted during the international
conferences in Strasbourg (1990), Rio de Janeiro (1992),
Helsinki (1993) and Kyoto (1996). Thus, sustainable
forest management is the stewardship and use of forests
and woodlands in a way and to an intensity so as to keep
their biological diversity, productivity, regenerative
capacity, vitality and ability to fulfill the current and
future ecological, economic and social functions at the
local, national and global levels, and that do not cause
prejudice to other ecosystems (Siry et al., 2005). This is
why the success and sustainability of forest management
cannot be achieved without the participation of the
population in the forest management process (Varughese
and Ostrom 2001; Chouinard and Perron 2002; Gareau
2005, Djogbenou 2005). The forest management plan is
the tool for operationalizing sustainable forest
management.
Benin has experienced several generations of forest
management plans. The Agoua, Monts Kouffé and Wari-
Maro Forest Management Project (PAMF) has drawn up
forest management plans especially the plans of the
Agoua classified forest and the complex of Monts Kouffé
-Wari - Maro classified forest. Several studies and
research focused on the effects and impacts of these

management plans. Djogbénou (2010) evaluated the
management plans of classified forests in Benin. This
evaluation highlights the quite mixed results. The
management plans carried out globally are those of the
classified forests of Pénéssoulou, Monts Kouffé, Wari-
Maro and Agoua. The assessment of the management
plans of the classified forests by Djogbénou (2010)
considered globally the socio-economic and governance
criteria and indicators (socio-economic benefits, the
financial profitability, the running of the village
committees for forests co-management, etc.). The state of
forest formations is not measured diachronically from the
indicators of species diversity and structure of forest
formations. It is therefore appropriate to analyze the
impact of successful management plans on the specific
diversity and structure of vegetation types. This research
has been undertaken in this perspective by considering the
Wari-Maro classified forest as survey field. The objective
of this research is to evaluate the impact of the
management plan on the diversity and the structure of the
vegetation types of Wari-Maro classified forest. The
hypothesis underlying the present research predicts that
the specific diversity and structure of the vegetation types
of Wari-Maro classified forest improved after the
implementation of the management plan.
Study area
The Wari-Maro classified forest covers an area of
111095.38 ha and is part of large protected areas in
Benin. Established by the order of classification
N°5194/SE of December 2nd, 1946 followed by a partial
downgrading by the decree N°9190/SE of November
25th, 1955, it is located in the center of Benin, in the
sudano-guinean transitional zone, between 8 ° 50 'and 9 °
10' north latitude and 1 ° 55 'and 2 ° 25' east longitude. It
is bounded on the north by the classified forest of Oueme
Superieur, on the south by the classified forest of Monst-
Kouffé, on the east by the national road Tchaourou-
Bétérou and on the west by the Wari-Maro-Igbèrè path
(Fig.1). The Wari-Maro classified forest is influenced by
the subhumid tropical climate (Arouna, 2005).
II. MATERIALS AND METHODS
2.1 Materials
The material used includes:
 GPS for the location of the sites;
 ribbon 50 m long and rope roll 100 m long for
the delimitation of plots;
 Forest and phytosociological inventories form ;
 SUUNTO clinometer for measuring trees height.
2.2 Phytosociological and forest inventories
Phytosociological and forest inventories were conducted
in the PAMF (2004) circular plots. The selected
phytosociological survey area has a radius of 5 m for the
herbaceous layer and 15 m radius for the shrub and tree
layers. For some particular stations such as riparian
forests, adjustments were made in the size of the plots
while respecting the survey area selected. These are
readjustments of 15 m x 47.1 m type in order to respect
the forest galleries shape. A total of 70 surveys were
inventoried (Table I). The phytosociological inventory
method used is the sigmatist method of Braun-Blanquet
(1932) already implemented by several authors (Sinsin,
1993, Djègo, 2006, Toko Imorou, 2008, Arouna, 2012).
Table.I: Number of phytosociological and forest
inventories plots by vegetation type
Vegetation types Number of plots
Riparian forests 10
Dry forest 11
Woodlands 12
Savanna woodlands 6
Tree savannas 23
Shrub savannas 3
Fields and fallows 3
Planting 2
Total 70
Species identification is made either directly on the field
or from specimens collected and compared with those of
the National herbarium of Benin or from flora (Arbonnier
2002, Akoegninouet al 2006, de Souza 2008).
The structural data collected are: the number of each
species individuals, the trees dbh ≥ 10 cm, the height of
the tallest tree and the degree of opening of the tree layer.
The trees dbh ≥ 10 cm is measured at 1.30 m above the
ground. The dendrometric data are collected in plots with
a radius of 15 m. The height of the largest tree is obtained
using the SUUNTO clinometer.
2.2 Treatment of phytosociological data
2.2.1 Specific diversity
Two parameters are studied at each level:
 The Shannon Diversity Index (H)
H = - Σ Pi log2Pi (1)
Pi = (ni/N) is the relative frequency of individuals of
species (i); (ni) is the number of individuals of the species
(i); (N) is the total number of individuals surveyed.
This index generally varies on average from 0 to 5 bits.
The high values of H reflect the favorable conditions of
the environment for the installation of many species. On
the other hand, low values of H reflect the adverse
environmental conditions for the establishment of the
species.

Fig.1: Geographical location of the Wari-Maro classified forest
The equitability of Pielou (E)
E = H / log2R (2)
H represents the Shannon diversity index;
log2R is the theoretical value of the maximum diversity
that can be achieved in each cluster; it corresponds to a
state of equal distribution of all individuals among all the
species of the group; R is the specific wealth.
This equitability varies from 0 to 1. Values close to 1
indicate a regular distribution of individuals between
species. On the other hand, values close to 0 correspond
to the presence of a large number of rare species or a
small number of dominant species.
2.3 Treatment of the dendrometric data
Two parameters are calculated: density and average basal
area.
 Density (D)
Density (D) is the number of standing trees per hectare. It
is calculated according to the formula:
D = N x 10000 / S (3)
D: number of stems / ha; N: number of stems with at least
2 m height; S: inventoried area reported to the sea.
 Average basal area (Gi)
The average basal area (Gi) is the area occupied by tree
trunks at breast height. It is calculated according to the
formula:
G = ΣΠd² / 4 (4)
Gi is in m2
/ ha; d = diameter at 1.30 m below the ground
(m); S: Inventoried area reported per hectare.
SPSS 21.0 and Minitab 14 software tested the results
obtained to ensure their significance.
III. RESULTS
3.1 Specific diversity of woody species before and after
the implementation of the management plan
Table II presents the diversity parameters of vegetation
types before and after the implementation of the
management plan of the classified forest.
From the review of Table II, it appears that the Shannon
diversity index calculated for dry forests, woodlands and
savannas in 2004 is higher than that recorded in 2014. On
the other hand, the riparian forests, the savanna
woodlands, shrub savannas and fields and fallows land
recorded the highest value of the Shannon Diversity Index
in 2014. The results of the paired sample t test for dry
forests, woodlands, riparian forests, savanna woodlands,
shrub savannas and fallow and fields at the 5% threshold,
reveal a nonsignificant difference between Shannon's
2004 diversity index and that of 2014. This means that,
Shannon's diversity index of these vegetation types
between these two dates is almost similar.
Whereas for the tree savannas, the results of the 5%
sample matched t-test reveal a significant difference
between the Shannon diversity index of 2004 and that of
2014. This means that, the Shannon Diversity Index of
tree savanna of 2004 is higher than that of 2014.

The Pielou equitability calculated for all vegetation types
in 2014 is greater than that of 2004. The results of the
sample t test matched at the 5% threshold, reveal an
insignificant difference between the 2004 Pielou
equitability and that of 2014 for all vegetation types
except woodlands and fields and fallow. This means that
the Pielou equitability of riparian forests, dry forests,
woodlands, tree savannas and shrub savannas between
these two dates is almost similar. On the other hand,
woodlands and fallow fields between these two dates
show a difference. It should be noted that there is an equal
distribution between the species in these vegetation types
because all the values of Pielou equitability turn around 1.
3.2 Structural parameters of woody species before and
after the implementation of the management plan
Table III presents structural parameters of vegetation
types before and after the implementation of the
management plan.
The examination of Table III shows that the average value
of dbh woody density ≥ 10 cm calculated in 2004 for
vegetation types such as riparian forests, dry forests,
woodlands, savanna woodlands and tree savannas is
higher than that obtained in 2014. On the other hand,
shrub savannas and fields and fallow land experienced
little change between these same dates. The results of the
5% matched sample t test show a significant difference
between the mean density value of 2004 and that of 2014
for all vegetation types except shrub savannas, fields and
fallows. This means that these vegetation types are under
strong pressure between 2004 and 2014. On the other
hand, shrub savannas and fields and fallows between
these two dates is almost similar according the density.
The basal area of vegetation types such as dry forest,
woodlands and savanna woodlands in 2004 is greater than
in 2014. The results of the 5% threshold matched sample t
test show a significant difference between the basal area
in 2004 and in 2014 for dry forests and not significant for
woodlands and savanna woddlands. This means that dry
forests have experienced the greatest decrease due to
logging. The basal area of woodlands and savanna
woodlands between these two dates is almost similar. On
the other hand, riparian forests, tree savannas, shrub
savannas, fields and fallow land recorded the highest
basal area values in 2014. The results of the 5% threshold
matched sample t test revealed a difference between the
Basal area of 2004 and that of 2014 for shrub savannas,
fields and fallows and not significant for riparian forests
and tree savannas. This means that the basal area of shrub
savannas and fields and fallow land has increased during
these years. The basal area of riparian forests and savanna
woodlands between these two dates is quite similar.
Table.II: Parameters of diversity of vegetation types before and after the implementation of the forest management plan
Vegetation types
Diversity parameters (2003) Diversity parameters (2013)
H' E H' E Test results
m σ m σ m σ m σ H' E
FG 2 0,65 0,76 0,07 2,46 0,87 0,8 0,19 0,44 0,09
FD 3 0,59 0,81 0,09 2,59 0,51 0,87 0,04 0,18 0,13
FC 3 0,36 0,82 0,05 3,05 0,48 0,9 0,05 0,099 0,0044*
SB 3 0,39 0,86 0,06 3,33 0,28 0,91 0,04 0,46 0,18
SA 3 0,57 0,85 0,02 2,74 0,56 0,87 0,07 0,004* 0,128
Sa 3 0,17 0,90 0,03 2,91 0,71 0,94 0,01 0,07 0,001*
CJ 2 0,73 0,68 0,22 2,6 1,17 0,9 0,07 0,213 0,01
FG: riparian forest; FD: Dry forest; FC: woodlands; SB: savanna woodlands; SA: tree savanna; Sa: shrub savanna; CJ:
Fields and fallows, * significance at the 5% threshold.
Table.III: Structural parameters of vegetation types before and after the implementation of the management plan
Vegetation types
Structural parameters (2004) Structural parameters (2014)
Density (N/ha) Basal area (m²/ha) Density (N/ha) Basal area (m²/ha) Test results
m σ m σ m σ m σ D (N/ha) G (m²/ha)
FG 689 285,00 25 12,70 545,85 152,91 28 10,7 0,03* 0,44
FD 657 312,02 34 22,09 317,53 160,66 18 10,84 0,003* 0,05*
FC 713 9,43 15 0,71 397,13 198,02 15 5,83 0,004* 0,93
SB 655 121,54 15 3,42 436,02 155,27 13 4,65 0,001* 0,12
SA 740 269,86 10 4,37 321,56 129,97 13 6,04 0,001* 0,08
Sa 193 42,00 4 0,62 183,83 99,99 8 0,29 0,2 0,001*
CJ 188 95,85 3 0,74 216,83 77,88 9 1,72 0,284 0,003*
FG: riparian forest; FD: Dry forest; FC: woodlands; SB: savanna woodlands; SA: tree savanna; Sa: shrub savanna; CJ:
Fields and fallows, * significance at the 5% threshold

IV. DISCUSSION
The Shannon diversity index between 2004 and 2014
varies from one vegetation type to another. The difference
in value of the Shannon diversity index was noted
especially in the savannas. Overall, the Shannon Diversity
Index values are similar in vegetation types regardless of
the year. The same is true of the values of Pielou's
equitability. This is confirmed by the paired sample t test
(p <0.05), which indicates significant differences in the
Shannon diversity index between the savanna woodlands
of 2004 and 2014. For Pielou's equitability, this
significant difference is noted at the level of woodlands,
shrub savannas and fields and fallows. This shows that
most of the plant species present in the different
vegetation types in 2004 were conserved in 2014 and that
the difference is more identifiable in the individuals of
these species. The calculated Shannon index values are
similar to those found by Biaou (1999) in the Bassila
forest and Sounon Bouko et al. (2007) in the Wari-Maro
classified forest. On the other hand, they are weaker than
those obtained by Toko Imorou (2008) in the upper
Ouémé catchment and Odjoubéré (2014) in the classified
forest of Monts Kouffé in west-central Benin.
The average density of dbh ≥ 10 cm was higher in natural
vegetation types in 2004 than in 2014. In fields and
fallow and shrub savannas, the reverse trend was
observed because the density passed respectfully from
188 stems / ha in 2004 to 217 stems / ha in 2014 and 193
stems / ha in 2004 to 183.83 stems / ha in 2014. These
results are confirmed by the paired sample t test (p <0.05)
which indicates significant differences in the density of
natural formations (riparian forests, dry forests,
woodlands, savanna woodlands and tree savannas)
between 2004 and 2014. The basal area of woodlands, dry
forests and savanna woodlands in 2004 is higher than in
2014. On the other hand, fields and fallows, riparian
forests, tree savannas and shrub savannas recorded higher
basal area values in 2014. In this case, only the basal area
of dry forests, shrub savannas and fields and fallows show
significant differences between 2004 and 2014 at the 5%
threshold of the matched sample t-test. The low density
and basal area values of ligneous trees in 2014 reflect the
impact of human activities on natural formations. These
density values are lower than the value obtained by Toko
Imorou (2008) in the upper Ouémé catchment. Values
closer to those of this study were obtained by Wala
(2004) in woodlands of northern Benin.
These analyzes indicate that logging increased after the
implementation of the management plan and especially at
the end of the PAMF project. This logging is practiced
mainly in dry forests, woodlands and savanna woodlands.
This indicates a low level of implementation of the
requirements of the management plan.
V. CONCLUSION
The assessment of the impact of the implementation of
the management plan is carried through the
phytosociological and forest inventories. The objectives
of the management plan are to significantly reduce the
anthropogenic pressures on the Wari-Maro classified
forest, to restore degraded areas, to contribute to the
maintenance of biodiversity while advocating the
sustainable exploitation of natural resources to favor local
development. The diachronic analysis of the specific
diversity parameters shows that the values of the Shannon
diversity index do not differ overall between 2004 and
2014. Most plant species inventoried in 2004 are present
in 2014.
On the other hand, Pielou's equitability shows that
individuals of different species are regularly distributed.
The diachronic analysis of dendrometric data revealed a
decrease in the density and basal area of trees from 2004
to 2014 despite the implementation of the Wari-Maro
Classified Forest Management Plan. The number of trees
has decreased even though most plant species are present.
The reconstitution of the Wari-Maro classified forest is
then possible if consequent measures are taken.
Let’s mention that the fight against deforestation will only
be effective if the living conditions of the neighboring
populations of the Wari-Maro classified forest are
improved.
ACKNOWLEDGEMENTS
At the end of this work, we express our deep gratitude to
the Program for strengthening capacity and access to
satellite data for monitoring forest in Central and West
Africa (GEOFORAFRI) of the Research Institute for
Development (IRD) which funded this research.
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