(2022) 11:50
Kengne et al. Ecological Processes
https://doi.org/10.1186/s13717-022-00387-9
Open Access
RESEARCH
Floristic composition, growth temperament
and conservation status of woody plant species
in the Cameroonian tropical rainforests
Olivier Clovis Kengne1* , Samuel Severin Kenfack Feukeng2, Eric Tchatchouang Ngansop3,
Raissa Gwladys Daghela Meyan-ya4 and Louis Zapfack4
Abstract
Introduction: Cameroon’s tropical rainforests are nowadays strewn with rural forests maintained by local populations; however, these forests are not officially recognized in the non-permanent forest domain. Rural forests are
non-delimited riparian areas within the dense moist forest, reserved for rural housing, agricultural activities and
agroforestry practices, freely exploited by the local communities for their livelihood without them having any rights to
artisanal and commercial logging. This study aimed at contributing to the flora knowledge and the conservation state
of woody plant species in rainforests. The study was carried out in two rural forests located in the Eastern and Southern agroforestry zones of Cameroon.
Methods: The method adopted for floristic inventories combined a fixed area sampling unit and a variable area
sampling unit. Woody individuals with diameter at breast height (dbh) < 3.2 cm were counted and shrubs of
3.2 ≤ dbh < 10 cm were measured to analyse the understorey, while trees with dbh ≥ 10 cm were measured and
identified to characterize the canopy.
Results: In the Essiengbot-Mbankoho rural forest in Eastern Cameroon, 468 species belonging to 61 families were
recorded in the understory while 227 species belonging to 53 families were identified at the canopy level. A total
of 40 (7.68%) threatened species, 18 (3.45%) Near Threatened species and 408 (78.31%) Least Concern species were
recorded. In the Nbgwassa-Opkweng rural forest in Southern Cameroon, 534 species belonging to 64 families were
identified in the understory while 225 species belonging to 43 families were recorded in the canopy. A total of 54
(9.69%) threatened species, 25 (4.49%) Near Threatened species and 421 (75.58%) Least Concern species were identified in this forest. Shannon’s diversity indices were above five in the understories and canopies of both forests. Shadebearer species were the most represented in the understories while the non-pioneer light-demanding and shadebearer species were the most abundant in the canopies.
Conclusions: Despite the influence of slash-and-burn agriculture and subsistence farming practices, rural forests
managed by local populations provide opportunities for preserving plant biodiversity. However, the presence of
threatened species, pioneer species and non-pioneer light-demanding species in these forests is an indicator of moderate and man-induced disturbances that, in the absence of a forest management plan or sustainable management,
may threaten this biodiversity. Legal management of rural forests could help in limiting the anthropogenic activities
and pressures on community forests.
*Correspondence: kengneoc@yahoo.fr
1
Department of Life and Earth Sciences, Higher Teachers’ Training College,
University of Maroua, P.O. Box 55, Maroua, Cameroon
Full list of author information is available at the end of the article
© The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which
permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the
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Kengne et al. Ecological Processes
(2022) 11:50
Page 2 of 17
Keywords: Floristic composition, Rural forest, Growth temperament, Understory, Canopy, Conservation status
Introduction
The Congo Basin forests are sources of livelihood, essential for the well-being of humanity (FAO 2005). Their
immense biodiversity generates a variety of natural
resources, which help to sustain the livelihood of local
communities (Kumar et al. 2006). They produce goods
and services necessary for the population’s well-being
by providing food, medical products, construction
materials, wood energy and timber. Forests also serve
as habitat for many animal and plant species (Fraticelli
et al. 2013). Deforestation and forest degradation in
the Congo Basin have considerably increased in recent
years (Megevand 2013). The annual rate of forest degradation has been estimated to be 0.09% between 2000
and 2005 (Ernst et al. 2013), whereas the rate of deforestation increased to 0.23% per year within the period
of 2000–2010 (FAO 2011). The disappearance of forests
threatens the livelihoods of local populations, in particular those who obtain most of their income from forest
products (Oumba 2007). According to Danquah (2016),
deforestation on community land results from land insecurity and weak property rights. As a result, forest management and conservation policies have been adopted by
various countries in Central Africa to protect forests and
strengthen the rights of local peoples. In Cameroon, the
zoning plan has become a key tool of the management
model of forested areas (Karsenty 1999). Established
in 1995, the zoning plan defines multi-purposed zones
where population activities are allowed (Nguiffo 2001).
This multi-purposed zone is an unassessed agroforestry
territory that occupies most of the local land in dense
forests regions. The agroforestry zones are part of the
non-permanent forest estate that can be used for other
purposes than forestry (Tchouto 2004). Therefore, agroforestry zone includes areas of rural forestry intended for
agricultural activities for local communities, community
forests and possibly private forests (Dkamela 2011). Rural
forestry includes forestry, agroforestry and silvopastoral
practices linked to a family or village activities in rural
areas (Sonwa et al. 2001).
Rural forest is a non-delimited space located in the
non-permanent forest domain without being identified
as a community forest or a private forest. Still, it corresponds to forest land reserved for rural housing, agricultural activities and agroforestry practices, freely exploited
by the local communities as part of their livelihoods.
The main forestry activity in this rural space is subsistence agriculture, mainly for self-consumption and the
village household’s economy. Agricultural activities are
essentially based on the association of food crops and
perennial cash crops with forest trees to form forest-crop
mosaics. Agroforestry practices carried out by farmers aim to harmonize the intensification of agricultural
activities along with the conservation of natural species
(Michon and Bompard 1987). All the local communities freely exploit the rural forest, without any industrial
and commercial logging rights. Customary rights were
restricted to the subsistence use of forests and trade-in
forest products became no longer authorized without
an individual permit from the government (Lescuyer
2013). This forest is mostly managed according to traditional local rules without an explicit development plan
(Poissonnet 2005). Traditional rights are exercised freely
as long as the beneficiaries maintain their geographical
proximity to the forest, do not harm any protected species and only take the products necessary for their wellbeing (Topa et al. 2010). Rural forests constantly adapt
to local needs and global conditions and evolve according to the change in requirements without necessarily or
drastically changing their forest structures and functions
(Michon et al. 2013).
However, in addition to the practice of slash-and-burn
agriculture, local populations carry out hunting, fishing,
firewood extraction, and harvesting of non-timber forest products in rural forests. Reconciling these human
activities, vital for rural communities, and preserving
biodiversity, is one of the main challenges for the sustainable management of tropical rainforests today. The
ever-increasing needs of the populations living along the
forest margin are nowadays coupled with a strong external demand for land designated for large-scale agricultural plantations (Djiofack 2018). This part of the dense
forest is regularly subjected to human activities and presents secondary exploited formations with an influence
on woody species. The forested area that results from
rural practices is made up of secondary forests, fallows
of different ages, food-producing field’s plots, swampy
areas, cocoa and coffee plantations, all scattered within
the dense moist forest (Kengne 2019). Increases in agricultural plots coupled with repeated clearing and the
reduction of fallow periods in rural forests can lead to
changes in floristic composition and plant structure,
influence the growth status of the woody vegetation or
the growth behaviour of plants, and be a threat to the
existing plant resources. In settling this rural forest,
which combines the human-change effect of spaces by
repeated practices (Michon 2004), it is difficult to have a
clear idea of the plant species composition, the effective
Kengne et al. Ecological Processes
(2022) 11:50
growth temperament of woody plants and the number of
threatened plants in this environment.
Anthropogenic ecosystems can in some cases be considered analogous to natural habitats, and may present
opportunities for biodiversity conservation (Lundholm
and Richardson 2010). Biodiversity conservation efforts
have mainly focused on “natural” protected areas
(Lomolino 1994), while agricultural areas and locally
exploited forest areas, such as rural forests, harbour biodiversity that needs to be preserved for subsistence and
sustainable use. The biodiversity in agricultural areas
is not without value, it provides, among other things,
many agronomic services (Altieri 1999; Clergué 2008).
Therefore, the sustainable management of rural forests
represents a major concern, both for the local populations who withdraw most of the resources for their
survival from these forests, and for the authorities in
charge of forests whose priority is to preserve biodiversity. Research, development and teaching activities have
shown that it is possible to revitalize the management of
Page 3 of 17
these agroforestry systems at the farm and village community level (Smektala et al. 2005). This work is a contribution to the knowledge of the rural forests’ flora and the
conservation state of woody plant species in rainforests
to increase the sustainable management of plant biodiversity. More specifically, we: (i) determined the floristic
composition of rural forests; (ii) identified the dominant
plant groups according to their growth ratio with respect
to light; and (iii) assessed the conservation status of
woody plant species under human activities.
Materials and methods
Study area
The study was carried out in two rural forests sites
located in the agroforestry zone of the Eastern and Southern Regions of Cameroon (Fig. 1). The agroforestry zone
is approximately 10 km wide, with 5 km on either side of
the main road (Ngoufo et al. 2012). The rural forest in the
Eastern Region of Cameroon extends from the Essiengbot village to the Mbankoho village, at 28 km north of
Fig. 1 Map showing the location of the study areas in Cameroon: Essiengbot-Mbankoho rural forest in the East Region, Nbgwassa-Opkweng rural
forest in the South Region
Kengne et al. Ecological Processes
(2022) 11:50
the Dja Fauna Reserve (DFR). This study area is located
between latitudes 3°30′–3°35′ N and longitudes 12°45′–
13°22′ E. The climate on the northern periphery of the
DFR is an equatorial humid type, characterized by four
seasons, including two rainy seasons and two dry seasons (De Wachter 1995). The mean annual temperature is
23.5 °C, with minimum average monthly temperatures of
22.8 °C and maximum average monthly temperatures of
24.6 °C (Delving 2001) while the average annual rainfall
ranges from 1500 to 1700 mm (Suchel 1987). The relief
is based on the Precambrian formations of the lower Dja
series, made up of shallow valleys with hills whose average altitude varies between 500 and 700 m. The soils are
of red ferralitic type, strongly desaturated, with indurated and deep ferruginous concretions (Ekodeck 2002).
Due to their acidity and low mineral content, these are
not very fertile soils. However, the permeability of these
clay-sandy soils provides the necessary fertility for food
and cash crops. The Essiengbot, Kompia and Mbankoho
villages from the northern periphery of the Dja Fauna
Reserve fall in the transitional zone between the semideciduous rainforest with Sterculiaceae (now Malvaceae)
and Ulmaceae (Cannabaceae), and the evergreen moist
forest (Letouzey 1968). The current forest on the northern periphery of the Dja Fauna Reserve is being invaded
by species found in the semi-deciduous forest. Gregarious formations of Coula edulis (Coulaceae) or Gilbertiodendron dewevrei (Fabaceae) can be observed (MINFOF
2011). The detailed vegetation typology consists of forests on rocks (5%), forests on hydromorphic soils (20%)
and forests on firm land (75%) (Sonké 1998).
The second rural forest site located in the Southern
Region of Cameroon stretches from the Nbgwassa village
to the Opkweng village on the northern periphery of the
Kom National Park-Mengamé Gorilla Sanctuary complex
(Fig. 1). This study area is between latitudes 2°22′–2°28′
N and longitudes 12°30′–12°40′ E. The climate is an
equatorial Guinean type, characterized by four seasons,
including two dry and two rainy seasons that alternate
throughout the year. The average annual temperature is
24.9 °C, with minimum average monthly temperatures
of 23.6 °C and maximum average monthly temperatures
of 26.5 °C (Anonymous 2004; Sock and Soua 2004). The
average annual rainfall varies from 1500 to 1600 mm
(Suchel 1987). The low-marked relief is presented in an
indented plateau of valleys with several hills whose altitude ranges between 500 and 700 m. The ferralitic soils
are highly desaturated with yellow facies, indurated depth
and hydromorphic. The dominant soils of moist dense
forests are acidic, poor in nutrients and have low organic
matter content (Vallerie 1995). Under these conditions,
shifting slash-and-burn agriculture is widely practised.
The vegetation on the northern periphery of the Kom
Page 4 of 17
National Park-Mengamé Gorilla Sanctuary complex
belongs to the mixed forest. Plant formations encountered there consist of species from the semi-deciduous
and evergreen rainforests (Letouzey 1968, 1985). Logging
and slash-and-burn agriculture have degraded the forest. The main consequence of anthropogenic activities in
the area has been the transformation of forest landscapes
into secondary plant formations. Affected environments,
i.e. mosaics of crops, degraded forests, fallow lands and
forest recruits allowed the settling of some species of
semi-deciduous forest than those of evergreen rain forest (Letouzey 1985). The vegetation physiognomy of the
Nbgwassa, Nkolenyeng and Opkweng villages showcase
more of the elements of the semi-deciduous forest, even
though the evergreen forest is the primary formation of
the southern region.
Two main Bantu ethnic groups, who are sedentary and
traditional cultivators, are found in our study area. The
populations of the villages in the East Cameroon belong
to the Badjoués ethnic group, while those in the South
Cameroon villages belong to the Fangs ethnic group.
The Baka Pygmies are also present in the different villages, but are a minority. These rural populations live
mainly from shifting slash-and-burn agriculture, nontimber forest products, wild fruit gathering, hunting,
traditional fishing and artisanal logging (Gockowski et al.
2004). Their agricultural activities are based on food and
cash crops such as cocoa, coffee and to a lesser extent,
palm oil. In general, the population density is very low,
between 1.5 and 2.8 inhabitants/km2 (De Watcher 2001).
Data collection
Sampling procedure
The method adopted for the floristic inventories combines a fixed area sampling unit and a variable area
sampling unit laid out on the same 40-m-long transect.
The fixed area sampling method consisted of setting up
a 5 m × 40 m rectangular plot. The plot was then subdivided into ten 2.5 m × 4 m quadrats arranged in alternate rows around the 40 m central transect or baseline.
Within each quadrat, the woody species found were
recorded and identified. All woody individuals of diameter at breast height (dbh) < 3.2 cm and height ≥ 0.5 m
were counted while shrubs of 3.2 ≤ dbh < 10 cm were
measured. The variable area sampling method, developed and detailed by Sheil et al. (2003), consists of realizing a plot of 40 m in length and variable width. The plot
which represents a floristic survey was subdivided into
eight subplots of 10 m width each, but of variable length
and orthogonal to the 40 m central transect. The length
of each subplot was determined by the position of the
fifth-most distant tree from the baseline. If five trees were
identified within 20 m from the baseline, the subplot
Kengne et al. Ecological Processes
(2022) 11:50
length was the distance to the fifth tree, whereas if less
than five trees were encountered, the subplot length was
taken as 20 m (Nath et al. 2009). In each subplot, trees
with dbh ≥ 10 cm were measured at 1.3 m above ground.
The woody species inventory was carried out in randomly selected plots. A total of 80 plots covering 5.75 ha
were sampled. The distance between two plots was more
than 500 m. We considered understory species as all
those individuals < 10 cm in diameter and height ≤ 15 m,
completely overtopped by trees close to the canopy,
while canopy species were trees of dbh ≥ 10 cm and
height > 20 m, with crowns exposed to direct sunlight.
Species collected during floristic inventories were identified by comparison with specimens from the National
Herbarium of Cameroon. Taxonomic nomenclature
adopted for the flora was based on the families classification established by the Angiosperm Phylogeny Group
(APG III 2009).
Data analysis
Data processing and statistical analysis
Data were managed using Microsoft Excel and analysed
using SPSS 18.0 software. The floristic composition of
each studied forest was obtained by determining the total
number of species, genera and families. The Shannon
index and the Pielou’s evenness index were computed to
quantify the species diversity and assess the species distribution within the plant community. The Shannon
index (H′) was calculated using the formula:
s
Ni
Ni
H′ = −
N × log 2 N , where Ni is the number of
i=1
individuals of species i, and N the total number of individuals of all species. The evenness index (E) was
′
expressed by the equation: E = logH S with H′ = the Shan2
non index; S = the total number of species in all the plots
sampled. Stem density and the basal area were also calculated to compare the woody vegetation’s structure. The
density (D) was determined by the number of stems per
hectare according to the formula: D = N/S, where N is
the total number of stems counted and S is the total area
of the plots in ha. The basal area (BA) expressed in m2
ha−1, wascalculated
according to the formula:
πD2
BA = S 4 , where D is the diameter (m) of all individuals belonging to a particular species taken at 1.3 m from
the ground, and S in ha is the total area of all surveyed or
sampled plots.
The importance of each species within the sampled
forest was determined with the Importance Value Index
(IVI) of species of Curtis and McIntosh (1950). This
index expressed in percentage was calculated using the
following formula: IVI = Der + Dor + Fr, where Der is
the relative density, Dor the relative dominance, and
Fr the relative frequency of species. The importance
Page 5 of 17
of each family in the entire sampling unit was determined from the Family Importance Value index (FIV)
of Mori et al. (1983). The family importance index
expressed in percentage was calculated by the formula:
FIV = Dir + Der + Dor, where Dir is the relative diversity,
Der the relative density, and Dor the relative dominance
of each family. The relative values of frequency, density,
dominance and diversity were computed according to
the formulae of Cottam and Curtis (1956) and Mori et al.
(1983). The importance value indices allow us to identify dominant species and families with high ecological
value within the vegetation. We considered species with
IVI ≥ 10% and the families with FIV ≥ 10% as having
strong ecological importance in the environment.
All recorded woody plant species were classified
according to their ecological growth (with respect to light
requirement) into three distinct classes: shade-bearers,
non-pioneer light demanders and pioneers (Hawthorne
1993). Pioneers (P) are species requiring full light conditions throughout their life cycle; Non-pioneer light
demanders (NPLD) are species able to recruit in understories, but needing light to grow up to the canopy;
Shade-bearers (SB) are species able to recruit and grow
in shade conditions (Gourlet-Fleury et al. 2013), they are
shade-tolerant species. The different ecological growth
temperaments with respect to light have been attributed
to woody species based on the work of Hawthorne (1993,
1995, 1996), then completed by those of other authors
such as Tchouto (2004), Beina (2011) and Kengne (2019).
The numbers of pioneer, non-pioneer light-demanding
and shade-bearer/tolerant species were determined in
the overall species recorded and identified. The percentages of individuals of these three temperaments were calculated in relation to the total number of individuals. A
descriptive statistical analysis allowed us to compare the
different plant groups according to their light requirements. The Pearson’s Chi-square (χ2) test was performed
to compare the percentages and to determine the significance level of potential differences in light requirements.
We considered differences significant when P was less
than 0.05.
The management and conservation status of plant biodiversity in rural forests was assessed using the conservation status of plant species of the International Union for
Conservation of Nature (IUCN). The conservation status
has been assigned to each plant species based on information from the global threat assessments provided by
IUCN (2011), IUCN (2012a, 2012b). The species statuses
were obtained through the online consultation of the Red
List of Threatened Species published by IUCN (2021).
The works on the Red Lists of the plants of Cameroon
by authors such as Tchouto (2004), Onana (2011), Onana
and Cheek (2011), have also allowed us to determine the
Kengne et al. Ecological Processes
(2022) 11:50
conservation status of plant species and were used to calculate the percent of threatened species. The IUCN Red
List categories used in this study are: Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near
Threatened (NT), Least Concern (LC), Data Deficient
(DD) and Not Evaluated (NE). Critically Endangered
(CR), Endangered (EN) and Vulnerable (VU) species
are those listed as threatened in the IUCN Red List of
Threatened Species (IUCN 2021).
Results
Floristic composition, species diversity and vegetation
structure
A total of 468 species of dbh < 10 cm belonging to 226
genera and 61 families were identified in the understory
of the Essiengbot-Mbankoho rural forest. The Shannon
index was 6.98 with an evenness index of 0.79. The average density of woody individuals was 3452 stems ha−1
for an average basal area of 9.22 m2 ha−1. The Importance Value Index (IVI) of species in the understory
ranged from 0.05 to 8.85%. The species with the highest
Importance Value Index were Theobroma cacao (8.85%),
Albizia adianthifolia (7.08%), Coffea canephora (6.24%),
Tabernaemontana crassa (5.31%), Trichilia monadelpha
(5.30%), and Petersianthus macrocarpus (5.01%; Table 1).
The Family Importance Value (FIV) index ranged from
0.23 to 38.94%. Eight families with FIV > 10% account
for 146.29% of the total family importance value indices.
These were Rubiaceae (38.94%), Euphorbiaceae (19.15%),
Meliaceae (18.33%), Fabaceae-Mimosoideae (17.01%),
and Malvaceae (15.71%; Table 2).
In the canopy or arborescent strata of this forest, 227
species with dbh ≥ 10 cm comprising 153 genera and
53 families were recorded. The Shannon index reached
a value of 6.81 for an evenness index of 0.87. The average density of trees was 477 stems ha−1 for an average
basal area of 53.56 m2 ha−1. The Importance Value Index
of species ranged from 0.22 to 15.06% in the canopy.
The most important species with an IVI ≥ 10% were
Ricinodendron heudelotii (15.06%), Musanga cecropioides (13.15%) and Petersianthus macrocarpus (12.86%;
Table 1), which together accounted for 41.07% of the
total importance value. The Family Importance Value
index ranged from 0.51 to 25.31%. Thirteen families
with FIV > 10% were the most important. These families constituted 191.47% of the total family importance
value. They were the Euphorbiaceae (25.31%), Malvaceae
(19.62%), Phyllanthaceae (17.66%), Meliaceae (17.12%),
and Fabaceae-Mimosoideae (15.68%; Table 2).
In the Nbgwassa-Opkweng rural forest, a total of 534
species with dbh < 10 cm representing 263 genera and
64 families were identified in the understory. The Shannon index was 6.96 with an evenness index of 0.77. The
Page 6 of 17
average density of woody individuals was 3824 stems
ha−1 for an average basal area of 10.21 m2 ha−1. The
Importance Value Index (IVI) of species ranged from 0.03
to 22.18%. The most important species were Theobroma
cacao (22.18%) and Mallotus oppositifolius (11.11%;
Table 1). These two species with IVI ≥ 10% contributed
33.29% of the total of IVI. The Family Importance Value
(FIV) index ranged from 0.19 to 36.31% for the families
of the understory. Seven families with FIV > 10% represented 157.26% of the importance values of families.
These were the Rubiaceae (36.30%), Malvaceae (34.43%),
Euphorbiaceae
(33.05%),
Fabaceae-Papilionoideae
(15.78%), and Fabaceae-Mimosoideae (12.97%; Table 2).
In the canopy of this forest, 225 species of dbh ≥ 10 cm
belonging to 151 genera and 43 families were recorded.
The Shannon index reached a value of 6.55 for an evenness index of 0.84. The average density of trees was 371
trees ha−1 and an average basal area of 41.98 m2 ha−1. The
Importance Value Index of species ranged from 0.17 to
17.61%. The most important species with an IVI ≥ 10%
were Musanga cecropioides (17.61%) and Petersianthus
macrocarpus (10.65%; Table 1). These were the two ecologically important species in the upper strata which
together contributed to 28.26% of the total importance
value index. The Family Importance Value (FIV) index
ranged from 0.51 to 30.01% for the families of the canopy.
Fourteen families with FIV > 10% were the most important. These families constituted 211.49% of the families
importance values. They were the Malvaceae (30.01%),
Euphorbiaceae (23.59%), Urticaceae (19.23%), FabaceaeMimosoideae (18.00%), Fabaceae-Papilionoideae (14.51%;
Table 2).
Ecological growth temperament of woody plant species
The analysis of the growth temperament of species
with respect to light showed that out of 468 species
recorded in the understory of the Essiengbot-Mbankoho rural forest, the shade-bearer species were the
most represented with 244 species (52.14%). The pioneer and non-pioneer light-demanding species were
lower in number with 111 species (23.72%) and 97 species (20.73%), respectively. The percentages of the species showed a highly significant difference between the
growth temperaments in the understory (χ2 = 65.18;
df = 3; P < 0.001). On the other hand, there was no difference between the numbers of pioneer species and
non-pioneer light-demanding species (χ2 = 1.06; df = 1;
P = 0.373). In terms of individuals, pioneers and shadebearers were the most represented in the understory
with 40.45% and 39.27% of the total of individuals
(Table 3). The Chi-squared test showed a significant
difference of the percentages of individuals between
the guilds (χ2 = 57.35; df = 3; P < 0.001) but there was no
Kengne et al. Ecological Processes
(2022) 11:50
Page 7 of 17
Table 1 The 15 most important species in the understory and canopy in each rural forest according to decreasing order of
importance value index
Species
Understory
Fr (%)
Der (%)
Species
Dor (%)
IVI (%)
Canopy
Fr (%)
Der (%)
Dor (%)
IVI (%)
Essiengbot-Mbankoho rural forest
Theobroma cacao
0.17
1.02
7.66
8.85
Ricinodendron heudelotii
2.16
2.46
10.44
15.06
Albizia adianthifolia
0.95
4.56
1.58
7.08
Musanga cecropioides
1.89
5.61
5.65
13.15
Coffea canephora
0.26
1.28
4.70
6.24
Petersianthus macrocarpus
2.84
4.38
5.64
12.86
Tabernaemontana crassa
1.12
2.08
2.11
5.31
Albizia adianthifolia
2.16
2.61
1.76
6.54
Trichilia monadelpha
0.82
1.19
3.30
5.30
Triplochiton scleroxylon
0.54
0.54
5.38
6.46
Petersianthus macrocarpus
1.07
1.51
2.43
5.01
Distemonanthus benthamianus
2.03
1.46
2.68
6.17
Myrianthus arboreus
1.03
1.22
2.45
4.71
Theobroma cacao
0.27
4.84
0.64
5.75
Vernonia conferta
0.39
0.89
2.94
4.21
Uapaca guineensis
1.62
1.46
1.96
5.04
Microdesmis puberula
0.99
2.69
0.19
3.87
Sterculia tragacantha
1.76
1.54
1.60
4.89
Whitfieldia elongata
0.64
3.21
0.00
3.86
Heisteria trillesiana
1.22
1.77
1.76
4.75
Distemonanthus benthamianus
0.99
2.82
0.00
3.80
Pycnanthus angolensis
2.03
1.46
1.25
4.74
Alchornea floribunda
0.82
0.54
2.22
3.57
Alstonia boonei
1.35
0.92
2.40
4.67
Albizia glaberrima
0.86
2.60
0.00
3.46
Ficus mucoso
1.08
1.23
1.98
4.29
Uapaca paludosa
0.90
1.82
0.73
3.45
Persea americana
1.08
2.31
0.67
4.06
Pycnanthus angolensis
0.39
0.91
1.93
3.23
Macaranga barteri
1.08
1.84
0.70
3.63
Remains (453)
88.61
71.66
67.75
228.02
Remains (212)
76.89
65.56
55.49
197.95
Total
100.00
100.00
100.00
300.00
Total
100.00
100.00
100.00
300.00
Nbgwassa-Opkweng rural forest
Theobroma cacao
0.57
1.90
19.71
22.18
Musanga cecropioides
2.81
7.47
7.33
17.61
Mallotus oppositifolius
0.78
9.57
0.75
11.11
Petersianthus macrocarpus
1.98
3.71
4.97
10.65
Millettia sanagana
0.97
4.94
2.41
8.33
Terminalia superba
1.87
1.55
5.38
8.81
Myrianthus arboreus
1.03
1.33
5.36
7.72
Theobroma cacao
0.73
7.11
0.69
8.54
Desbordesia glaucescens
0.84
3.46
0.50
4.80
Coelocaryon preussii
2.39
3.41
1.77
7.57
Coelocaryon preussii
0.97
0.68
2.87
4.52
Distemonanthus benthamianus
2.29
1.85
3.30
7.44
Psychotria lastistipula
0.81
3.58
0.00
4.40
Triplochiton scleroxylon
0.83
0.96
5.51
7.30
Albizia adianthifolia
1.06
1.64
1.55
4.24
Dichostemma glaucescens
1.56
2.87
1.79
6.22
Tetrorchidium didymostemon
0.51
0.48
3.03
4.02
Pterocarpus soyauxii
1.14
0.96
3.97
6.07
Tabernaemontana crassa
0.97
1.76
1.28
4.01
Myrianthus arboreus
2.19
2.57
0.97
5.73
Microdesmis puberula
0.81
1.37
1.83
4.01
Pseudospondias microcarpa
2.08
1.79
1.76
5.63
Distemonanthus benthamianus
0.92
1.50
1.28
3.70
Margaritaria discoidea
1.87
2.03
1.54
5.44
Bridelia micrantha
0.81
0.98
1.55
3.34
Pycnanthus angolensis
1.56
1.32
2.52
5.40
Macaranga barteri
0.65
0.58
2.08
3.31
Celtis tessmannii
1.66
1.26
2.12
5.04
Vernonia conferta
1.27
2.03
0.00
3.30
Ricinodendron heudelotii
1.14
0.96
2.91
5.01
Remains (519)
87.01
64.18
55.80
206.99
Remains (210)
73.88
60.19
53.47
187.54
Total
100.00
100.00
100.00
300.00
Total
100.00
100.00
100.00
300.00
Fr relative frequency, Der relative density, Dor relative dominance, IVI importance value index
significant difference among pioneer and shade-bearer
individuals (χ2 = 2.35; df = 1; P = 0.226). In the canopy,
the number of non-pioneer light-demanding species was higher with 87 species (38.33%), followed by
shade-bearer species (78 species; 34.36%) and pioneer
species (55 species; 24.23%). The difference was highly
significant between the number of species of these
light requirement temperament (χ2 = 39.79; df = 3;
P < 0.001). However, there was no significant difference
between non-pioneer light-demanding species and
shade-bearer species (χ2 = 2.51; df = 1; P = 0.194). In
terms of individuals, the non-pioneer light-demanding
species were the most represented with 561 individuals (43.12%) followed by the pioneer species with 460
individuals (35.36%) (Table 3). The difference between
the percentages of individuals were highly significant
(χ2 = 55.85; df = 3; P < 0.001).
Kengne et al. Ecological Processes
(2022) 11:50
Page 8 of 17
Table 2 The 15 most important families (sub-families) in the understory and canopy in each rural forest according to decreasing order
of family importance value
Family
Understory
Dir (%)
Canopy
Der (%)
Dor (%)
FIV (%)
Family
Dir (%)
Der (%)
Dor (%)
FIV (%)
Essiengbot-Mbankoho rural forest
Rubiaceae
Euphorbiaceae
17.83
12.38
8.72
38.94
Euphorbiaceae
4.72
8.15
12.44
25.31
4.46
8.10
6.58
19.15
Malvaceae
3.86
7.61
8.14
19.62
Meliaceae
5.73
4.82
7.78
18.33
Phyllanthaceae
5.15
7.76
4.74
17.66
Mimosoideae
3.82
8.90
4.29
17.01
Meliaceae
7.30
6.76
3.06
17.12
Malvaceae
4.46
2.02
9.23
15.71
Mimosoideae
4.29
5.30
6.09
15.68
Apocynaceae
2.76
5.77
5.28
13.81
Moraceae
3.86
4.61
5.61
14.08
Phyllanthaceae
3.40
3.90
5.83
13.13
Caesalpinioideae
4.72
3.69
5.57
13.99
Caesalpinioideae
3.40
2.80
4.02
10.21
Urticaceae
0.86
6.53
5.83
13.22
Olacaceae
3.61
4.70
1.65
9.96
Olacaceae
3.43
4.46
4.51
12.40
Annonaceae
3.82
3.31
2.40
9.53
Apocynaceae
3.86
3.46
3.60
10.93
Papilionoideae
2.76
2.16
2.64
7.56
Annonaceae
4.29
3.84
2.45
10.58
Sapindaceae
4.25
1.53
1.53
7.30
Lecythidaceae
0.43
4.38
5.64
10.45
10.43
Myristicaceae
1.70
5.10
0.00
6.80
Rubiaceae
5.58
2.61
2.24
Acanthaceae
0.85
1.91
3.29
6.04
Cannabaceae
3.00
3.15
2.58
8.73
Urticaceae
0.64
5.35
0.00
5.99
Papilionoideae
2.58
3.69
2.35
8.61
Remains (46)
Total
36.52
27.26
36.75
100.53
Remains (49)
100.00
100.00
100.00
300.00
Total
42.06
23.98
25.15
91.19
100.00
100.00
100.00
300.00
Nbgwassa-Opkweng rural forest
Rubiaceae
19.48
13.34
3.49
36.30
Malvaceae
9.25
12.12
8.27
29.64
Malvaceae
6.18
4.68
23.57
34.43
Euphorbiaceae
4.41
11.64
7.52
23.57
Euphorbiaceae
4.31
19.03
9.71
33.05
Urticaceae
0.88
9.93
8.12
18.93
Papilionoideae
3.56
7.68
4.54
15.78
Mimosoideae
5.29
5.85
6.75
17.89
Mimosoideae
2.81
6.48
3.69
12.97
Papilionoideae
4.85
3.13
6.70
14.68
Meliaceae
4.12
2.74
5.88
12.74
Cannabaceae
2.64
5.02
6.17
13.84
Phyllanthaceae
3.75
2.91
5.34
12.00
Meliaceae
6.61
3.84
2.29
12.74
Apocynaceae
3.18
4.14
2.04
9.36
Moraceae
3.52
4.85
3.94
12.31
Urticaceae
0.37
1.70
7.06
9.13
Phyllanthaceae
4.85
4.43
2.91
12.19
Caesalpinioideae
3.93
2.20
2.70
8.84
Myristicaceae
1.76
5.50
4.57
11.83
Moraceae
1.69
2.56
3.22
7.47
Caesalpinioideae
4.41
2.42
4.72
11.55
Annonaceae
3.56
1.52
2.30
7.38
Rubiaceae
7.93
1.77
1.47
11.18
Myristicaceae
0.75
1.84
4.47
7.06
Apocynaceae
4.41
2.96
3.58
10.94
Cannabaceae
2.25
3.87
0.07
6.19
Annonaceae
4.85
2.90
2.42
10.17
Irvingiaceae
1.31
1.98
2.74
6.03
Remains (38)
38.76
23.32
19.18
81.27
100.00
100.00
100.00
300.00
Total
Combretaceae
Remains (28)
Total
1.32
2.07
6.18
9.57
33.04
21.57
24.37
78.98
100.00
100.00
100.00
300.00
Dir relative diversity, Der relative density, Dor relative dominance, FIV family importance value
Out of the 534 species recorded in the understory of the
Nbgwassa-Opkweng rural forest, the shade-bearer species were the most common with 284 species (53.18%).
Pioneer species and non-pioneer light-demanding species
were low in number with 119 and 113 species (22.29% vs.
21.16%), respectively (Table 3). The difference between
these two types of growth behaviour was not significant
(χ2 = 1.18; df = 1; P = 0.278). The individuals of pioneers
species were the most represented (44.69%) followed by
the individuals of shade-bearer species (33.63%). The differences observed between the percentages of individuals were highly significant (χ2 = 58.09; df = 3; P < 0.001).
The shade-bearer species with 83 species (36.89%) and
non-pioneer light-demanding species (79 species; 35.11%)
were the most dominant in the canopy. According to the
percentages of the species, the difference between these
Kengne et al. Ecological Processes
(2022) 11:50
Page 9 of 17
Table 3 Numbers of species and individuals by growth temperament category with respect to light in the understories and canopies
of the rural forests
Essiengbot-Mbankoho rural forest
Nbgwassa-Opkweng rural forest
No. of species (%)
No. of individuals (%)
No. of species (%)
No. of individuals (%)
4368 (40.45)a
119 (22.29)a
11,171 (44.69)a
b
a
5368 (21.47)b
b
8408 (33.63)c
Understory (individuals < 10 cm dbh)
P
NPLD
SB
111 (23.72)a
a
97 (20.73)
2151 (19.92)
b
244 (52.14)
c
a
4240 (39.27)
c
113 (21.16)
284 (53.18)
c
Unidentified
16 (3.42)
39 (0.36)
18 (3.37)
52 (0.21)d
Total
468 (100.00)
10,798 (100.00)
534 (100.00)
24,999 (100.00)
55 (24.23)a
460 (35.36)a
58 (25.78)a
554 (32.74)a
b
b
b
852 (50.36)b
b
276 (16.31)c
Canopy (trees ≥ 10 cm dbh)
P
NPLD
SB
87 (38.33)
b
78 (34.36)
c
561 (43.12)
c
272 (20.91)
d
79 (35.11)
83 (36.89)
c
Unidentified
7 (3.08)
8 (0.61)
5 (2.22)
10 (0.59)d
Total
227 (100.00)
1301(100.00)
225 (100.00)
1692 (100.00)
P pioneer, NPLD non-pioneer light-demanding, SB shade-bearer. Proportion (in %) of species and individuals are noted parenthetically. Values followed by different
letters (a, b, c, d) within a column indicate a significant difference between the growth temperament categories in relation to light (χ2-test, p < 0.05)
two dominant guilds was not significant (χ2 = 4.63; df = 1;
P = 0.311). The individuals of the non-pioneer lightdemanding species were the most represented with 852
individuals (50.35%) followed by the individuals of pioneer species (554 individuals; 32.74%) (Table 3). The percentages of individuals differed very significantly between
species groups (χ2 = 73.30; df = 3; P < 0.001).
Conservation status of woody plant species
A total of 521 plant species assessed in the EssiengbotMbankoho rural forest according to the IUCN Red
List Categories allowed us to identify 3 species (0.58%)
Critically Endangered (CR: Ardisia etindensis, Ardisia
schlechteri, Beilschmiedia preussi), 5 species (0.96%)
Endangered (EN: Autranella congolensis, Beilschmiedia letouzeyi, Placodiscus angustifolius, Pericopsis
elata and Tieghemella africana) and 32 species (6.14%)
Vulnerable (VU: e.g., Allanblackia gabonensis, Antrocaryon micraster, Baillonella toxisperma, Boutiquea
platypetala, Calpocalyx hertzii, Coffea mapiana, Cordia platythyrsa, Empogona talbotii, Entandrophragma
cylindricum, Entandrophragma utile, Garcinia kola,
Khaya grandifoliola, Leplaea cedrata, Macaranga
paxii, Memecylon candidum, Nesogordonia papaverifera, Pterygota macrocarpa, Terminalia ivorensis, Turraeanthus africanus). According to these results, 40
species (7.68%) of the flora are considered as threatened (i.e. Vulnerable, Endangered and Critically Endangered), and 18 species (3.45%) were assessed as Near
Threatened. In addition, 408 species (78.31%) were categorized as Least Concern (Fig. 2a). In this case, 81.77%
of plant species were considered as not threatened in
this forest.
In the Nbgwassa-Opkweng rural forest, the assessment carried out on 557 plant species showed that 4
species (0.72%) were Critically Endangered (CR: Ardisia
etindensis, Ardisia oligantha, Beilschmiedia preussii,
Plagiosiphon longitubus), 10 species (1.80%) were
Endangered (EN: Anisotes zenkeri, Autranella congolensis, Cola attiensis, Millettia laurentii, Pericopsis elata,
Placodiscus caudatus, Prioria balsamifera, Rhaptopetalum depressum, Tieghemella africana and Vitex lehmbachii) and 40 species (7.18%) were Vulnerable. Among
the species considered Vulnerable (VU), we found
Afzelia bipindensis, Baillonella toxisperma, Boutiquea
platypetala, Calpocalyx heitzii, Cola mahoundensis,
Cola nigerica, Cordia platythyrsa, Dacryodes buettneri,
Diospyros crassiflora, Drypetes molunduana, Entandrophragma angolense, Entandrophragma candollei, Garcinia kola, Khaya anthotheca, Leplaea thompsonii,
Neosogordonia papaverifera, Pterygota bequaertii, Sterculia oblonga, Tricalysia amplexicaulis, and Trichoscypha engong. It was shown that 54 species (9.69%) of
the flora in the forest are threatened (i.e. Vulnerable,
Endangered and Critically Endangered), and 25 species (4.49%) were listed as Near Threatened. Moreover,
421 species (75.58%) were classified as of Least Concern meaning that 80.07% of plant species were considered not threatened in this rural forest (Fig. 2b).
Distribution of species growth temperaments by IUCN Red
List categories
The distribution by IUCN threat category of species
growth temperaments in relation to light revealed that
Kengne et al. Ecological Processes
(2022) 11:50
Page 10 of 17
Fig. 2 Number and percentage of plant species in each IUCN Red List category of the Essiengbot-Mbankoho (a) and Nbgwassa-Opkweng (b) rural
forests. The number of species is given in parentheses. IUCN Red List Categories: CR Critically Endangered, EN Endangered, VU Vulnerable, NT Near
Threatened, LC Least Concern, DD Data Deficient, NE Not Evaluated
in the Essiengbot-Mbankoho rural forest, shade-bearer
species with 199 species (49.63%) were the most represented in the Least Concern (LC) category followed by
110 pioneer species (27.43%) and 92 non-pioneer lightdemanding species (22.94%) (Fig. 3a). The same trend
was observed in the Nbgwassa-Opkweng rural forest
where the Least Concern (LC) category was dominated
by 210 shade-bearer species (49.88%), 114 pioneer species (27.08%) and 97 non-pioneer light-demanding species (23.04%) (Fig. 3b). The other threat categories, with
very low numbers of shade-bearer, pioneer and nonpioneer light-demanding species were the less represented in the whole forests. In the Essiengbot-Mbankoho
rural forest, the densities of shrubs of 3.2–10 cm dbh
and trees ≥ 10 cm dbh showed that pioneer species and
shade-bearer species were the most represented with,
respectively, 1308 stems ha−1 (37.77% of the total density) and 1149 stems ha−1 (33.17%) in the Least Concern
category. In the same IUCN category, non-pioneer lightdemanding species had the lowest density of individuals
with 717 stems ha−1 (20.70%) (Fig. 3c). In the NbgwassaOpkweng rural forest, pioneer species with 2021 stems
ha−1 (43.47%) had the higher density in the Least Concern category followed by shade-bearer species with
1406 stems ha−1 (30.25%). However, non-pioneer lightdemanding species with 888 stems ha−1 (19.10%) had the
lowest density of individuals in this category (Fig. 3d).
Discussion
Floristic composition, species diversity, and vegetation
structure
The results of the floristic inventories showed that
the numbers of species, genera and families in both
understories and canopies of rural forests were higher
than many other forests. More than 400 species with
dbh < 10 cm in the understory have been reported by
many previous studies in tropical rainforests (Gentry
1990; Schmitt 1996; Turner et al. 1996; Losos and Leigh
2004; Tchouto et al. 2006; Berry et al. 2008; Beina 2011).
The high species richness in the understories of rural
forests could be due to the nature of the soil, presence of
nutrients, light intensity, canopy cover, species composition of the upper strata and the types of disturbances.
Wittmann and Junk (2003) in Amazonian várzea forests
in Brazil and Singh et al. (2014) in a tropical dry deciduous forest in India made similar observations. According
to these authors, species composition also depends on
the forest structure of the overstory and the amount of
radiation intake during the time of plant establishment.
Sporadic disturbances, whether natural or induced by
human activities, create favourable growing conditions
for the regeneration and the establishment of new species in the understory. The high numbers of species in the
understories would be also linked to the abundance of
different pioneer species and non-pioneer light-demanding species, due to the presence of gaps in the canopy
that favoured the entrance of light into the understory.
In tropical rain forests, high light availability in gaps
promotes seed germination and growth of seedlings of
most canopy and understorey species (Balderrama and
Chazdon 2005). The shade-bearer species that colonize
small windthrows also increase the number of species
in the understory. We can deduce from the results that
the understory is the forest stratum that participates the
most in the in situ conservation of species biodiversity.
(2022) 11:50
CR EN VU
NT
Number of species
P
NPLD
SB
240
210
180
150
120
90
60
30
0
(a)
Number of individuals/ha
Page 11 of 17
LC DD NE
P
NPLD
SB
1400
1200
1000
CR EN VU NT LC DD NE
(b)
IUCN Red List Category
800
600
400
200
0
CR EN VU NT LC DD NE
(c)
IUCN Red List Category
P
NPLD
SB
240
210
180
150
120
90
60
30
0
Number of individuals/ha
Number of species
Kengne et al. Ecological Processes
IUCN Red List Category
P
NPLD
SB
2400
2100
1800
1500
1200
900
600
300
0
CR EN VU NT LC DD NE
(d)
IUCN Red List Category
Fig. 3 Distribution of pioneer, non-pioneer light demanding, shade-bearer species and densities in different IUCN Red List categories in the rural
forests of Essiengbot-Mbankoho (a, c) and Nbgwassa-Opkweng (b, d). P pioneer, NPLD non-pioneer light demanding, SB shade-bearer. CR Critically
Endangered, EN Endangered, VU Vulnerable, NT Near Threatened, LC Least Concern, DD Data Deficient, NE Not Evaluated
In the canopies of rural forests, the number of species
was slightly more than 200 species. This species richness
in the upper strata is similar to that of other studies made
in tropical moist forests (van Germeden et al. 2003; Natta
2003; Barbar et al. 2011; Beina 2011; Fongnzossie et al.
2011; Lisingo 2015; Memiaghe et al. 2016; Sainge 2017).
The Shannon indices (H′) of the understories and the
canopies were very high in the two rural forests (6.55–
6.98). These diversity values were close to those between
4.39 and 7.04 reported in Cameroon by other researchers
(Zapfack et al. 2002; Sonké 2004; Fongnzossie et al. 2011;
Noiha et al. 2015; Kengne et al. 2018). In addition, many
other works in Africa and Asia reported Shannon indices
ranging from 5.51 to 7.89 (Babar et al. 2011; Beina 2011;
Kimpouni et al. 2013; Sajib et al. 2016). According to
Kent and Coker (1992), the Shannon diversity index (H′)
can reach a value ≥ 4.5 for the most diverse communities
in tropical forests. Our results showed that the diversity
index H′ can reach a value ≥ 6.0 for highly diverse and
less disturbed plant stands of dense tropical rainforests.
This very high value indicates the great floristic diversity of the forest milieu. The high diversity observed in
rural forests could be explained by the lack of dominant
species and the equitable distribution of woody plant
individuals within species at different levels of the forest. This allows to say that the high diversity is due to the
greater evenness. According to Ramade (2009), greater
diversity increases the stability of the system through the
interactions between the populations constituting the
vegetation. In the face of anthropogenic activities, rural
forests are subjected to fragmentation that generates a
mosaic of land-use types with a very heterogeneous flora
(primary forests relics, secondary forests, swamps, fallows, fields, cocoa and coffee plantations). The different
activities carried out by local populations in rural forests
would not have a negative effect on the floristic diversity
due to their periodicity and low intensity (Kengne 2019).
Dahan et al. (2018) estimated that the cropping system
based on fallow-crop rotation and the practice of agroforestry would favour species maintenance at the agricultural areas level.
The understories are characterized by high numbers
of species and individuals belonging to the Rubiaceae
family. The same observation was made by Lü and Tang
(2010) and Lü et al. (2011) in the understories of tropical seasonal rainforests in China. However, the presence
of Euphorbiaceae, Phyllanthaceae, Urticaceae and even
Fabaceae-Mimosoideae both in the understory and in the
Kengne et al. Ecological Processes
(2022) 11:50
canopy illustrates the secondary and non-climax character of these forest areas with farmers’ exploitation. The
ecological importance of these families is reflected by
the presence of colonizing species that participate in the
reconstitution of degraded areas (Kengne et al. 2018).
The average densities of individuals obtained in the
understories of the two rural forests were quite similar to
the mean values of 3914, 3068 and 3600 stems ha−1 found
in other understories of tropical rainforests, respectively, by Tchouto et al. (2006), Lü et al. (2011) and Sainge
(2017). However, the values recorded in rural forests
were higher than those obtained in other tropical forests (Wittmann and Junk 2003; Rasingam and Parthasarathy 2009; Lü and Tang 2010; Tiokeng et al. 2015). This
high density could be explained by the dynamics of forest regeneration and resilience after disturbance, which
would favour the development of young individuals of
different plant species in the understories. The high densities of small-diameter individuals (3–10 cm) prove that
the renewal of seed-bearing trees and the replacement
of cut down, felled or dead trees will be ensured in forest areas with farming activities. According to Memiaghe
et al. (2016), the diversity and abundance of the smalldiameter trees suggest that the forest could have the ability to respond to disturbances in general.
The average tree densities obtained in the canopies
of the two rural forests were lower than the densities of
more than 500 trees ha−1 found in tropical rainforests by
other authors (Tchouto et al. 2006; van Germeden et al.
2003; Sonké 2004; Sainge 2017; Tiokeng et al. 2015; Natta
2003; Beina 2011). The illegal exploitation of timber by
logging companies in previous years and the expansion
of slash-and-burn agriculture in the forest zone of eastern and southern Cameroon have led to a significant
reduction in tree density. The low densities observed in
the canopies would also be the result of the large spacing between individuals followed by the random dispersal
of large-diameter trees in forest areas. During the establishment of agricultural plots, some trees that can be
harmful to crops are cut down, which causes a considerable decrease in the density of the wooded cover. Indeed,
Gartlan (1989) reported that the felling of an individual
tree of a species increases the distance between breeding
individuals.
The mean basal areas of woody species obtained in
the understories of the two rural forests were higher
than those recorded in the lower strata of other tropical rainforests (Wittmann and Junk 2003; Enninful 2013;
Memiaghe et al. 2016; Sainge 2017). The higher values of
basal areas in the understories of these forests would be
related to the abundance of species with great capacities
to grow faster in diameter than in height. The large basal
areas were largely due to the abundance of shrubs and
Page 12 of 17
small trees with diameters between 5 and 10 cm in the
understories of secondary forests, fallow land and cash
crop plantations of the rural forests.
The mean values of tree basal areas in canopies were
higher compared to those reported in tropical forests by
previous studies (Zapfack et al. 2002; van Gemerden et al.
2003; Sonké 2004; Pappoe et al. 2010; Enninful 2013;
Lisingo 2015; Sainge 2017). The large basal areas in the
upper strata of rural forests would be explained by the
conservation of very large-diameter trees because of the
ban of artisanal and commercial logging activities.
Ecological growth temperament of woody plant species
The analysis of growth temperament of woody plants
with respect to light revealed that the understories of
the two rural forests were richer in shade-bearer species
(52.14–53.18%) than in pioneer species (22.29–23.72%)
and non-pioneer light-demanding species (20.73–
21.16%). However, there was no significant difference
between the number of pioneer species and the number of non-pioneer light-demanding species. Enninful
(2013) in Ghana reported similar results where indeed,
shade-bearer species constituted the highest proportion
of the understory layer (42.48%), followed by non-pioneer light-demanding species (28.32%) and pioneer species (19.47%). The great richness of shade-bearer species
could be explained by their facility to settle and develop
in the absence of light. According to Dreyer et al. (2005),
shade-bearer plants can survive at low light levels for
long periods and quickly resume active growth after reexposure to light. Saplings are able to survive understory
light conditions owing to low respiration rates and low
light requirements at saturation, but they are dependent on some canopy opening for substantive growth and
reproduction (Denslow 1987; McCarthy 2001). Gravel
et al. (2010) pointed out that shade-bearer species would
colonize small-sized windthrows, same as Delcamp
(2007) who found that environments with smaller openings favour the regeneration of a greater diversity of
shade-bearer species. When pioneer and non-pioneer
light-demanding species settle in the understory, light
conditions must be sufficient to ensure their growth and
survival.
On the other hand, pioneer species were the most
represented in individuals (40.45–44.69%) in the understory, followed by shade-bearer species (33.63–39.27%).
For species needing light to germinate and not being
able to grow under low light intensities, the effect of
light spots can lead to the massive survival of individuals
(Traissac 2003). Our results showed that pioneer species
poorly represented in the understory produce very large
numbers of individuals to colonize open surfaces and
degraded environments. This suggests that the number of
Kengne et al. Ecological Processes
(2022) 11:50
individuals produced by pioneer species depends on the
level of disturbance and the size of the windthrow to be
reconstituted. This finding corroborates with Thorsten
(2011) observations for whom the abundance of pioneers
increased with ascending gap size and was even significantly higher in medium and large size logging gaps
compared to undisturbed forest sites. Alexandre (1986)
estimated that the gaps are colonized by pioneer shrubs
that constitute a less diversified dense vegetation after a
disturbance phase. Several factors such as forest shade,
soil fertility, small gaps in the closed canopy, low level
of light, fast regeneration and gregarious distribution of
stems could explain the abundance of shade-bearing individuals in the understory. The abundance of shade-bearers species can be explained by the capability of those
species to accumulate under shaded conditions in the
forest understory (Mwavu and Witkowski 2009; Thorsten
2011). Vieilledent (2009) noted that under the canopy,
shade-bearer species more adapted to poor light conditions in young stages have a significantly higher probability of regeneration than non-pioneer light-demanding
species.
Analysis of the growth temperament with respect to
light of species with dhp ≥ 10 cm revealed that the numbers of non-pioneer light-demanding species (35.11–
38.33%) and shade-bearer species (34.36–36.89%) were
the most dominant in the canopies of the two rural
forests. Our results are close to those of Lisingo (2015)
who found in the DRC, 49.90% and 40.49% of shadebearer species, 36.40% and 49.15% of non-pioneer lightdemanding species, 10.90% and 5.80% of pioneer species
in the tree stand of mixed forests and in the stand of
monodominant forests, respectively. The number of longlived pioneer species generally important in the canopies
of intensely degraded or highly disturbed forests is low
in the upper strata of our study forests. This could be
explained by the fact that after canopy openings by slashand-burn agriculture and tree fall, the long-lived pioneer
species that first participate in the reconstitution of the
formed gaps, arrive very quickly in the canopy during forest succession, but will later be replaced by non-pioneer
light-demanding species and shade-bearer taller trees of
superior longevity, which will dominate in the canopy
affected by the past disturbances. Beina (2011) argued
that when disturbances are infrequent, the vegetation is
dominated by the most competitive, long-lived shadebearer species, with few pioneer species in the canopy. In
general, shade-bearer species or late-successional species
grew better in small or older gaps (Obiri and Lawes 2004;
Muscolo et al. 2014). Gillet (2013) estimated that the
plant formations with open canopies and/or dominated
by large non-pioneer light-demanding trees would reflect
past human disturbances. Non-pioneer light-demanding
Page 13 of 17
tree species and shade-bearing tree species would play a
major role in the stability of the forest, as they participate
in the canopy closure, set up the upper strata of the forest, maintain the height of the canopy, allow the reconstruction of the crown architecture and restructuring the
forest cover after any natural or anthropogenic disturbance. Cirimwami et al. (2017) noted that when the forest
tends to be stable it becomes more dominated by nonpioneer light-demanding and shade-bearer species. These
species have developed specific strategies with respect to
light, to grow as fast as possible. Their ability to quickly
cover the canopy would be bound to their temperament
(Oldeman 1974; Palla et al. 2011).
Nevertheless, individuals of non-pioneer lightdemanding species were the most represented in the canopies (43.12–50.36%), followed by individuals of pioneer
species (32.76–35.36%). A similar result was obtained in
the Kahuzi-Biega National Park in the DRC by Cirimwami et al. (2017) where non-pioneer light-demanding
individuals were most represented in the canopy layers (64.0%) followed by shade-bearer individuals (21.8%)
and pioneer individuals (13.3%). The abundance of nonpioneer light-demanding trees and the presence of many
long-lived pioneer individuals in the arborescent strata
would be linked to the canopy reconstitution process
due to the past degradation of the upper strata of rural
forests by former logging companies, illegal selective logging and slash-and-burn agriculture. Doucet (2003) also
found that only a regular burning of the forest in particular for agricultural purposes, could have modelled forest
composition by increasing the amount of light-demanding species. The openings closure created in the canopy
would be done by the tree stands mainly constituted by
individuals of non-pioneer light-demanding species. Tree
species that have a high demand for light are at larger
proportion of the flora in such forests (Whitmore 1985;
Denslow 1987).
Conservation status of woody plant species
The assessment of the threat level of woody plant species according to the IUCN Red List showed that the
vascular flora of the two rural forests had high percentages (75.58% and 78.31%) of plant species of Least Concern (LC), but low percentages (7.68% and 9.69%) of
threatened species (CR, EN, VU). Our results are similar to those reported for vascular flora in the regions of
France. Noble et al. (2015) found for the vascular flora
of Provence-Alpes-Côte d’Azur 71.30% species of Least
Concern and 10.80% of threatened species, Delage and
Hugot (2015) for the flora of Corsica reported 69.56%
species of Least Concern and 9.70% of threatened species, Quéré et al. (2015) recorded 68.56% species of
Least Concern and 15.10% of threatened species. This
Kengne et al. Ecological Processes
(2022) 11:50
Page 14 of 17
observation on the conservation status of plant species
would reveal a non-worrying threat situation for the flora
of forest areas used by the local populations. Rural forests are subjected to slash-and-burn agriculture, hunting, and exploiting non-timber forest products by local
populations. However, these anthropogenic exploitation
activities are regulated by conservation and sustainable management practices such as agroforestry, seasonal
clearing, use of traditional preservation knowledge and
the prohibition of artisanal and/or commercial timber
exploitation. It is the farmers’ respect for these principles
of preservation and sustainable use of plant resources
that had reduced the threats to the vascular flora of rural
forests. De Watcher (2001) noted that the low population
density and the cyclic nature of shifting agriculture do
not threaten the forests. Bohoussou (2014) pointed out
that the success of the conservation of a site depends on
the local population’s involvement because they constitute the first threat.
The distribution of species growth temperaments
according to IUCN Red List categories in rural forests
showed that shade-bearer species dominated in the Least
Concern (LC) category. This category also had high densities of individuals in pioneer and shade-bearer species.
This could be due to the effects of human activities over
the last decades, which have created gaps in the canopies and induced slight disturbances in the forests. Plant
species classified as threatened should benefit from prioritized follow-up actions and regulated protection,
even though efforts still have to be made to eradicate
the threats on plant biodiversity in all the Cameroon’s
rainforest.
light-demanding species and shade-bearer species,
whose roles are to maintain and restore the forest’s
maturity. The assessment of the conservation status and
threats of species in rural forests unveiled a large dominance of woody plant species with Least Concern status and a low presence of threatened species. Indeed,
no major threats were identified on plant species in
rural forests. Despite their slight degradation, the ban
on commercial logging, the practice of agroforestry
and the seasonal agricultural activities carried out by
local populations, they allowed the good conservation
of plant biodiversity. It would be desirable that forestry
law considers the role of rural forests in the well-being
of local communities and the preservation of plant species. For a more efficient sustainable management of
those rural forests, effective development and management plans should be put in place to reduce the pressures of anthropogenic activities, the multiplicity of
land-use types and eliminate species threats in these
forest areas. The planning of forest areas reserved for
exploitation by rural populations would improve local
conservation techniques and perpetuate the sustainable
management of forest biodiversity. In addition, legal
management of the rural forests could help to limit the
anthropogenic activities and pressures on community
forests.
Conclusions
This study has shown that the rural forests are rich in
species and have very diversified floras in the understories and canopies. The important floristic composition
observed resulted from slight or moderate induced disturbances, which are responsible for the species diversity within the land-use types of these forests. However,
rural forests have shown a reduction in species richness and a decrease in tree density in the canopies due
to slash-and-burn agriculture, illegal logging and tree
mortality through senescence. Analysing the growth
temperament of the species with respect to light has
revealed that the understories were richer in shadebearer species and abundant in pioneer species individuals. Furthermore, non-pioneer light-demanding
species and shade-bearer species dominated the canopies. Rural forests in the face of past anthropogenic
disturbances and the current subsistence activities
of local populations show an important successional
dynamic marked by the strong presence of non-pioneer
Acknowledgements
This research was carried out by CIRAD (Centre de Coopération Internationale
en Recherche Agronomique pour le Développement) as part of the ‘Popular’
project under the Agriculture and Sustainable Development Program. The
study was partially supported by the International Foundation for Science
(Sweden) through the research grant number D/5123-1 awarded to Dr
Kengne Olivier Clovis. The authors of this work are grateful to all the village
chiefs who allowed us to carry out the researches on their lands. We would
like to acknowledge Dr Lescuyer Guillaume for making this research possible
and Dr Garcia Claude for his help in applying the floristic inventory methodology on the field. Our special thanks go to all the guides and prospectors who
assisted us in the data collection during the field work. We are also grateful
to the National Herbarium of Cameroon (Yaoundé) for plant identification.
Finally, the authors are greatly indebted to the anonymous reviewers for their
constructive suggestions and helpful comments on the manuscript.
Abbreviations
APG: Angiosperm Phylogeny Group; CIRAD: French Agricultural Research
Centre for International Development; dbh: Diameter at breast height; DRC:
Democratic Republic of the Congo; DFR: Dja Fauna Reserve; FAO: Food and
Agriculture Organization of the United Nations; IUCN: International Union
for Conservation of Nature; MINFOF: Ministry of Forestry and Wildlife; SPSS:
Statistical Package for the Social Sciences.
Author contributions
The first author (OCK) collected the data, analysed it and wrote the manuscript. The fourth author (RGDM) revised the manuscript. The fifth (LZ) supervised the work. All authors read and approved the final manuscript.
Funding
The study was supported by CIRAD and the International Foundation for
Science (IFS).
Kengne et al. Ecological Processes
(2022) 11:50
Availability of data and materials
The data generated and analysed during the present study are available from
the corresponding author.
Declarations
Ethics approval and consent to participate
Not applicable.
Consent for publication
All authors have agreed to publish this manuscript.
Competing interests
The authors declare that they have no conflicts of interest.
Author details
1
Department of Life and Earth Sciences, Higher Teachers’ Training College,
University of Maroua, P.O. Box 55, Maroua, Cameroon. 2 Department of Plant
Biology, University of Dschang, P.O. Box 67, Dschang, Cameroon. 3 Institute
of Agricultural Research for Development (IRAD), National Herbarium of Cameroon, P.O. Box 1601, Yaoundé, Cameroon. 4 Department of Plant Biology,
University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon.
Received: 21 January 2022 Accepted: 15 June 2022
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