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How far a protected area contributes to conserve habitat species composition and population structure of endangered African tree species (Benin, West Africa)

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... To establish the stem diameter structure of each plant community, all individuals were grouped into diameter classes of 10 cm in order to obtain enough diameter classes (at least 10). Size class distributions were adjusted to 3-parameters (a, b, c) Weibull theoretical distribution [24,29] because of its flexibility [30]. This theoretical distribution has the ability to describe a wide range of unimodal distributions including reversed-J-shaped, exponential and normal frequency distributions [31]. ...
... The protected gallery forests on the other hand have a similar floristic composition as the unprotected gallery forest. This suggests that human disturbance affects savanna species composition more than gallery forest [29]. This is in accordance with the theory saying that gallery forests are refuge areas for many plants and animals in dry regions [53]. ...
... This is in accordance with the theory saying that gallery forests are refuge areas for many plants and animals in dry regions [53]. If species composition of gallery forests is not significantly modified by human disturbance, this may suggest low human pressure on gallery forests in the study area or may depend on the accessibility or disturbance threshold in this habitat [29]. ...
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Aims: As a contribution to the sustainable management of protected areas in Togo, this study aims to analyze the impact of anthropogenic activities on plant communities in the wildlife reserve of Oti-Mandouri (North-Togo). Study Design: The study area is located in the Sudanian zone, in northeast Togo. Place and Duration of Study: The field work was carried out during April and June 2009, whilst processing data was done at Lab From July to October 2009. Methodology: Total height and stem diameter at breast height (dbh) greater than 10 cm of all trees species were measured in 126 plots. In each plot, ecological parameters were recorded and the seedling and suckers (dbh<10cm) of species were counted. Results: 116 woody species with dbh greater than 10 cm belonging to 33 families and 84 genera were listed. Presence/absence data of the overall species recorded in each plot was subjected to multidimensional scaling and results showed 4 types of woody vegetation: shrub savannas, tree savannas, wooded savannas and gallery forest. The most common families were Rubiaceae (14.28%), Mimosaceae (13.26%) and Combretaceae (11.22%). Species such as Combretum glutinosum (48.68%), Mitragyna inermis (36.84%), Acacia polyacantha (35.52%) and Piliostigma thonningii (35.52%) were relatively more frequent, but this potential floristic resource was almost threatened by human activities such as farming, grazing, burning, and tree cutting. The structure adjusted by 3-parameter Weibull showed reverse “J” shape for class diameter distribution with shape parameter varies between 1 and 3.6 showing a predominance of individuals with small diameter within the overall study area. Conclusion: The results showed that this protected area is subjected to much degradation, and its conservation is important in the process of biodiversity conservation varices grades.
... To establish the stem diameter structure of each plant community, all individuals were grouped into diameter classes of 10 cm in order to obtain enough diameter classes (at least 10). Size class distributions were adjusted to 3-parameters (a, b, c) Weibull theoretical distribution [24,29] because of its flexibility [30]. This theoretical distribution has the ability to describe a wide range of unimodal distributions including reversed-J-shaped, exponential and normal frequency distributions [31]. ...
... The protected gallery forests on the other hand have a similar floristic composition as the unprotected gallery forest. This suggests that human disturbance affects savanna species composition more than gallery forest [29]. This is in accordance with the theory saying that gallery forests are refuge areas for many plants and animals in dry regions [53]. ...
... This is in accordance with the theory saying that gallery forests are refuge areas for many plants and animals in dry regions [53]. If species composition of gallery forests is not significantly modified by human disturbance, this may suggest low human pressure on gallery forests in the study area or may depend on the accessibility or disturbance threshold in this habitat [29]. ...
... The role of protected areas in the prevention of extinction of species has been much debated (Bruner et al., 2001). Several studies focused on the effectiveness of the protected areas to ensure the representativeness and persistence of biodiversity components (Defries et al., 2005;Wittemyer et al., 2008;Houéhanou et al., 2011Houéhanou et al., , 2012Houéhanou et al., , 2013. Some of the studies (Djossa et al., 2008;Gouwakinnou et al., 2009;Schumann From the demographic explosion, correspondingly strong land modification was observed in West Africa (Wittig et al., 2007;Wittemyer et al., 2008). ...
... It conserves 28% of the total flora of Benin Republic (Assédé et al., 2012). Previous studies have highlighted the importance of this reserve in plant conservation (Gouwakinnou et al., 2009;Fandohan et al., 2011;Houéhanou et al., 2011Houéhanou et al., , 2013. Although the BRP is assumed to be the best way to conserve biodiversity of this area, its effectiveness in future conservation of several plant species is not always guaranteed (Houéhanou et al., 2013). ...
... Previous studies have highlighted the importance of this reserve in plant conservation (Gouwakinnou et al., 2009;Fandohan et al., 2011;Houéhanou et al., 2011Houéhanou et al., , 2013. Although the BRP is assumed to be the best way to conserve biodiversity of this area, its effectiveness in future conservation of several plant species is not always guaranteed (Houéhanou et al., 2013). Substantial representative gaps remain in its coverage of some plant taxa. ...
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The effectiveness of protected areas to guarantee future conservation of several plant species remains questionable. This study was carried out in the Biosphere Reserve of Pendjari (BRP) and surrounding unprotected areas to assess the efficiency of the reserve to conserve orchids. A total of 90 plots (52 in protected areas; 38 in unprotected areas) were sampled. The recorded data include: orchid species, number of individuals per species, the height and diameter at breast height of host trees. Diversity indices were used to assess the orchid diversity in the protected and unprotected areas. Preferred habitat conditions of orchid species were investigated using Constrained Correspondence Analysis. An independent t-test and two-way analysis of variance were performed to assess an existing combined effect of vegetation type and the conservation status on the density of orchid species. The Importance Value Index (IVI) was used to measure how dominant an orchid species is in a given zone according to the conservation status of the zone. Only three epiphytic orchids (Calyptrochilum christyanum, Cyrtorchis arcuata and Plectrelminthus caudatus) were recorded and all in gallery forest of unprotected areas. Indeed, 67% and 58% of the orchid species were only recorded in unprotected areas and in gallery forest, respectively. There was no significant difference between the density of all recorded orchids in protected and unprotected areas. The conservation status of the studied zone had a significant effect on the densities of Nervilia kotschyi and Eulophia guineensis (p < 0.0001). The highest IVI of N. kostchyi was observed in the protected area and of E. guineensis was in the unprotected area. This first effort to compile a reference list of the orchid species of the BRP showed that some orchid species were well represented within the protected area, but all of the epiphytic orchids were recorded from unprotected areas. A representative gap can be assumed to exist for most epiphytic orchids only recorded in the gallery forests of unprotected areas. Our results highlighted the need to redefine protective management strategies for orchid species in the BRP.
... The Pendjari Biosphere Reserve is a PA located in the Sudanian zone, which is the most managed PA in Benin (Delvingt, Heymans & Sinsin, 1989;Houehanou et al., 2013), maintaining natural ecological processes and native species (Hansen & Defries, 2007). Management strategies, such as the regular early bush fire, patrols against poaching and others, applied in this PA aim at conserving large and visible wild animals as these latter provide almost all financial resources obtained from the reserve valorization through tourism (Houehanou et al., 2013). ...
... The Pendjari Biosphere Reserve is a PA located in the Sudanian zone, which is the most managed PA in Benin (Delvingt, Heymans & Sinsin, 1989;Houehanou et al., 2013), maintaining natural ecological processes and native species (Hansen & Defries, 2007). Management strategies, such as the regular early bush fire, patrols against poaching and others, applied in this PA aim at conserving large and visible wild animals as these latter provide almost all financial resources obtained from the reserve valorization through tourism (Houehanou et al., 2013). In this PA dominated by savannah landscapes, the density of termite mounds is steadily increasing and needs to be integrated in the management strategies for savannahs, as they represent crucial habitats for both plant and animal species and provide essential contributions to spatial structure and complexity (Erpenbach, Wittig & Hahn, 2014). ...
... The study was undertaken in the UNESCO Man and Biosphere Reserve of Pendjari located within Atacora district (10°30 0 -11°30 0 N, 0°50 0 -2°00 0 E) ( Fig. 1) in North Benin, a West African country. It is one of the most important and better managed West African fauna reserves in term of plants and animals diversity conservation (Delvingt, Heymans & Sinsin, 1989;Houehanou et al., 2013). It covers an area of 4661 km 2 and is composed of the National Park of Pendjari (2660 km 2 ), the hunting zone of Pendjari (1750 km 2 ) and the hunting zone of Konkombri (251 km 2 ). ...
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Understanding the role of termite mounds in biodiversity and ecosystem functioning is a priority for the management of tropical terrestrial protected areas dominated by savannahs. This study aimed to assess the effects of termite mounds on the diversity of plant functional types (PFTs) and herbaceous' net aboveground primary productivity (NAPP) in plant communities (PCs) of the Pendjari Biosphere Reserve. PCs were identified through canonical correspondence analysis performed on 96 phytosociological 'relevés' realized in plots of 900 m². PFTs' diversity was compared between savannahs and mounds' plots using generalized linear models. In each plot, 7 m² subplots were harvested and NAPP was determined. Linear mixed models were performed to assess change in herbaceous NAPP regarding species richness, graminoids' richness, specific leaf area and termite mounds. There is no specific plant community related to mounds. However, the occurrence of termite mounds induced an increase of woody and forbs diversity while the diversity of legumes and graminoids decreased. These diversity patterns led to decreasing of PCs' NAPP. This study confirms that termite-induced resource heterogeneity supports niche differentiation theory and increased savannah encroachment by woody species.
... Among these species, A. africana is the most threatened species and is classified as endangered at country-scale (Adomou et al., 2009). There are regional scale studies (Sinsin et al., 2004;Bonou et al., 2009;Houehanou et al., 2013;Ouédraogo and Thiombiano, 2012) that elucidated the current traits of A. africana populations and reported a very weak potential of recruitment. Human disturbances and climate pejoration were documented to have a significant negative impact on A. africana regeneration (Ouédraogo and Thiombiano, 2012). ...
... In the Guinean zone, forests and fallow habitats shelter the species (Bonou et al., 2009), however, change in its population structure in relation with other climatic zones remains unclear. Additionally, many studies on A. africana were limited to a local scale (Bonou et al., 2009;Houehanou et al., 2013;Chabi et al., 2013) and missed linking the species' traits with its climatic environment (Sinsin et al., 2004). There is therefore the need to document knowledge on the species traits across climatic zones and determine the effects of South African Journal of Botany 95 (2014) [165][166][167][168][169][170][171][172][173] disturbance levels across these climatic gradients. ...
... The authors reported very rare saplings of A. africana with recruitment and growth difficulties in natural stands. Low regeneration density observed in the Sudanian zone (even in the protected area) suggests that, protection would not be always a sufficient action to conserve some threatened tree species; other factors like climate pejoration and occurrence of potential bush fires may also compromise the viability of the threatened tree species (Bognounou et al., 2009;Biaou, 2009;Nacoulma et al., 2011;Ouédraogo and Thiombiano, 2012;Houehanou et al., 2013). The effects of disturbances were also examined through the establishment of stand diameter structures. ...
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Anthropogenic disturbances and climatic variations are presumed to alter species population structures. In this study,we assessed the population structure of the endangered species, Afzelia africana across gradients of climate and human disturbances. Dendrometric variables such as regeneration and tree density, mean diameter, basal area and height and stem diameter distribution were recorded at national scale in forest reserves located in three different climatic zones in Bénin. A canonical discriminant analysiswas applied to describe the species' population structure across climatic zones and disturbance levels. Relationships between the principal components (structural parameters of A. africana stands) and climatic variables and disturbance levels were assessed using Pearson correlation. Significant differences were found in the structural parameters between the disturbance levels, mostly in the Guinean zone. Structural parameters also differed significantly across the three climatic zones, with the Guinean zone recording the highest values. The effects of disturbance levels on structural parameters depend on the climatic zone, and vice versa. The results imply an interaction between climatic zones and disturbance levels. In the Guinean zone, the tallest and biggest trees were found at the low disturbance level. However, along the climatic gradient (towards drier regions), trees were shorter and smaller irrespective of disturbance level. Further, the tallest and biggest trees were found at lower altitudes.
... To establish the stem diameter structure of each plant community, all individuals were grouped into diameter classes of 10 cm in order to obtain enough diameter classes (at least 10). Size class distributions were adjusted to 3-parameters (a, b, c) Weibull theoretical distribution [24,29] because of its flexibility [30]. This theoretical distribution has the ability to describe a wide range of unimodal distributions including reversed-J-shaped, exponential and normal frequency distributions [31]. ...
... The protected gallery forests on the other hand have a similar floristic composition as the unprotected gallery forest. This suggests that human disturbance affects savanna species composition more than gallery forest [29]. This is in accordance with the theory saying that gallery forests are refuge areas for many plants and animals in dry regions [53]. ...
... This is in accordance with the theory saying that gallery forests are refuge areas for many plants and animals in dry regions [53]. If species composition of gallery forests is not significantly modified by human disturbance, this may suggest low human pressure on gallery forests in the study area or may depend on the accessibility or disturbance threshold in this habitat [29]. ...
... To date, several studies discussed the impact of anthropogenic disturbance on tree population and how land use types or human disturbance can impact population patterns of tropical tree species (Assogbadjo, Mensah, & Glèlè Kakai, 2017;Fandohan, Assogbadjo, Glèlè Kakai, & Sinsin, 2010;Houehanou et al., 2013;Idohou, Assogbadjo, Azihou, Glèlè Kakai, & Adomou, 2016;Mensah, Houehanou, Sogbohossou, Assogbadjo, & Glèlè Kakaï, 2014;Nacoulma, Traoré, Hahn, & Thiombiano, 2011). These studies inferred negative effects of human disturbance on structural parameters such as life stage densities, height, diameter, size class distributions, diameter-height relations, etc. ...
... One of the direct consequences of international trade and local exploitation of the species organs is the severe decline of its populations. Hence, at the international level, populations of P. erinaceus are declining due to human pressure (Adomou, Sinsin, Akoegninou, & van der Maesen, 2009;Houehanou et al., 2013;IUCN, 2008;Lykke, 1998;Nacoulma et al., 2011). In West Africa, P. erinaceus populations are studied across climatic zones (Sègla et al., 2015(Sègla et al., , 2016 and in some natural forests (Glèlè Kakaï, Sinsin, & Palm, 2008;Glèlè Kakaï, Assogbadjo, Sinsin, & Pelz, 2009). ...
... In West Africa, P. erinaceus populations are studied across climatic zones (Sègla et al., 2015(Sègla et al., , 2016 and in some natural forests (Glèlè Kakaï, Sinsin, & Palm, 2008;Glèlè Kakaï, Assogbadjo, Sinsin, & Pelz, 2009). The effect of land use type or human disturbance has been evaluated on its populations in Benin (Houehanou et al., 2013) and Burkina Faso (Nacoulma et al., 2011). ...
Article
Human‐modified systems come as innovative ones necessary to be more understood to attain biodiversity conservation goals. This study aimed to assess the effect of human disturbance on the population structure of Pterocarpus erinaceus in different land use types (Highly protected area, Moderately protected area and Non‐protected area) in Sudanian savannahs of Togo. Data were collected in forty randomly set plots (50 m × 30 m) within each land use type. Population structure parameters and leaf and leaflet morphological traits were evaluated and compared among the land use types by performing different statistical analyses. Results showed an adverse effect of human disturbance on adult and juveniles densities as well as the total height (significant difference between highly protected and non‐protected areas; p < 0.001). Diameter class structures revealed in the three land use types an inverted J‐shape indicating the predominance of young individuals. Significantly greater (p < 0.001) values of leaflet length were observed in the non‐protected area compared to highly protected one. The human‐mediated area impacted the diameter‐height relation and the one among assessed leaf and leaflet traits. These findings are tools to be incorporated in new policy development for the future management of this tree species population. Résumé Les systèmes modifiés par les hommes sont des systèmes nouveaux qu'il faut mieux comprendre afin d'atteindre les objectifs de conservation de la biodiversité. Cette étude visait à évaluer l'effet de perturbations humaines sur la structure de populations de Pterocarpus erinaceus dans différents types d'utilisation des (zone très protégée, moyennement protégée et non protégée) dans des savanes soudaniennes du Togo. Des données furent récoltées dans des 40 parcelles de 50 m x 30 m installées de façon aléatoire dans chaque type d'utilisation des terres Les paramètres de la structure des populations et les caractéristiques morphologiques des feuilles et folioles ont été évalués et comparés selon les types d'utilisation des terres en faisant différentes analyses statistiques.Les résultats ont montré un effet négatif des perturbations humaines sur la densité des jeunes et des adultes ainsi que sur la hauteur totale (différence significative entre parcelle très protégée et non protégée : P<0,001). La structure des classes de diamètre a révélé dans les trois types d'utilisation des terres une forme en J renversé qui indique la prédominance de jeunes individus. Des valeurs significativement plus grandes (P<0,001) de la longueur des folioles ont été observées dans la zone non protégée que dans la zone très protégée. La zone impactée par les hommes influence la relation diamètre‐hauteur et celle entre les caractéristiques évaluées des feuilles petites et grandes. Ces résultats sont de nouveaux outils qu'il faut intégrer dans les nouvelles politiques de développpement pour la gestion future des populations de cette espèce d'arbre.
... Afzelia africana Sm. (Fabaceae, APG III) is among the most vulnerable tree species in West Africa because of its high exploitation by local communities due to its value in medicine or as fodder (Houehanou et al. 2011), and especially because of its significant economic role for timber manufacturers. Consequently, a severe decline of this tree species has already been reported in many places at local as well as regional level (Hahn-Hadjali and Thiombiano 2000;IUCN 2008;Adomou et al. 2009, Houehanou et al. 2013. Sustainable management and conservation of that tree species became necessary and thus, knowledge of how climatic condition and human disturbance can shift its morphological traits will help to design the related strategies. ...
... In Benin, as well as in other West Africa countries, human pressure has exacerbated many tree populations in their natural habitats, and the situation is often strengthened by an increase of human population and neglected protection of natural populations even within some protected sites. Thus, the long-term disturbance by human activities has been modified structure and demography of many tree species (Houehanou et al. 2013;Mensah et al. 2014;Gaoue and Ticktin 2010). Regarding such human disturbance, studies have been shown adverse effects on various populations' attributes of A. africana. ...
... Regarding such human disturbance, studies have been shown adverse effects on various populations' attributes of A. africana. Tree densities, mean diameters and basal areas of A. africana populations are proved to be negatively influenced by human disturbance (Mensah et al. 2014;Houehanou et al. 2013). The adverse effect of pruning on growth rates of A. africana and its relationships with woody density functional trait has also been assessed (Amahowe et al. 2018). ...
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Afzelia africana Sm. is a tree species found in different climatic conditions affected by chronic human disturbance. It is known that trees can respond to their environments by changing their morphological traits. Also, as plants store their reserves in fruits, seeds and leaves, long-lasting disturbance may impact morphological traits of fruits, seeds and leaves. Thus, in this study, we evaluated (1) the variation of morphological traits of A. africana according to climatic conditions and human disturbance, and (2) the relationships among morphological traits. Twelve morphological parameters based on fruits, seeds and leaflets were assessed across three climatic zones and compared for individuals in protected and disturbed landscapes. Univariate and multivariate analyses were used to evaluate the effects of climatic factors and disturbance. Highest values for fruit, seed and leaflet traits were observed in humid areas indicating for best performance under optimal conditions. Significant adverse effects of human disturbance were observed for traits in the humid and drier areas. The interaction between climatic conditions and disturbance was significant for most traits suggesting a climate-dependent effect of the disturbance on evaluated traits. Bioclimatic variables were thus identified as potential drivers of traits. Some significant and positive associations were observed among fruit and seed traits. These morphological trait variations are valuable insights to guide sustainable management and conservation of A. africana populations in different climatic zones and habitats types in Benin.
... However, less attention has been given to determine which of the climate or human disturbance has the stronger effects. For instance, the limited regeneration potential of A. africana (Houehanou et al. 2013;Mensah et al. 2014) can result either from weak reproductive performance due to foliage and bark harvest (Gaoue and Ticktin 2008) or from environmental constraints, such as water and nutrient stress. Mensah et al. (2014) found taller individuals of A. africana in less drier regions, and related this to water availability, but it remains a fact that these dry regions are the main transhumance areas, highly preferred by herders for tree logging and foliage harvesting, which could potentially modify the ecological processes by limiting regeneration and growth of the pioneer species. ...
... In addition, A. africana trees were generally of a lower density in the Guinean and Sudano-Guinean Zones, and of a much higher density in the Sudanian Zone (Mensah et al. 2014). The use of 0.09 ha plots in the Sudanian Zone was based on the earlier use of that plot size for characterising the populations of A. africana in the Sudanian Zone (Nacoulma et al. 2011;Houehanou et al. 2013). The difference in plot sizes was accounted for during the data analysis by weighting the studied parameters by the plot size. ...
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The study aimed to investigate the relative significance of effects of climatic variability and human disturbance on the population structure of the threatened species Afzelia africana Sm. ex Pers. in the Republic of Benin in West Africa. Forest inventory data such as regeneration density, tree diameter and total height were compiled from A. africana forest stands under different disturbance regimes in the three climatic zones of Benin. Multiple generalised linear models and non-linear diameter–height equations were fitted to contrast the individual effects of categorical variables, such as climatic zone and disturbance level. Results revealed significantly higher scaling coefficients in less drier regions and low-disturbance stands. The diameter–height relationship was more controlled by the climatic zone than by the disturbance level. Accordingly, the disturbance level contributed only to the intercept of the diameter–height model, whereas the climatic zone significantly influenced both intercept and slope. In addition, when climatic zone and disturbance level were considered as sources of variation in the diameter–height model, the former explained the greater marginal variance. It was concluded that climate has the greater effect on population structure of A. africana in natural stands.
... Because of these uses,A. africana is classified as endangered at country-scale (Adomou et al. 2009).The acknowledged utility of the species in tandem with its insistent harvesting has increased the investigations at local and regional scales (Sinsin et al. 2004, Bonou et al. 2009, Ouédraogo and Thiombiano 2012, Houehanou et al. 2013a). ...
... africana were limited to a local scale (Bonou et al. 2009, Houehanou et al. 2013a, Chabi et al. 2013) and missed linking the species traits with climatic conditions (Sinsin et al. 2004). ...
... (Fabaceae-Caesalpinioideae) is a widespread tree species found along the latitudinal gradient, from the northern Sahel to the Guinean littoral forest. Previous studies showed that populations of A. africana Sm. faced strong anthropogenic pressures (Houehanou et al. 2013;Nacoulma et al. 2011;Mensah et al. 2014). The species is harvested for timber mainly by indigenous communities and its foliage is important forage for livestock. ...
... The differences in plot sizes and plot densities are due to the change in the type of vegetation (Sudanian and Sahelo-Sudanian zones are essentially savannas, while woodland and dense forest characterized the vegetation of Sudano-Guinean and Guinean zones). The use of 0.09 ha as plot size in Sudanian and Sahelo-Sudanianwas justified by the fact thatprevious studies successfully used in these climatic zones (Nacoulma et al. 2011;Houehanou et al. 2013). Within each plot, presence or absence of A. africana was noted, only plots with A. africana recorded were considered for further analysis. ...
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This study assessed the woody flora composition of Afzelia africana Sm. habitats along a latitudinal gradient, from the northern limit of the species distribution to the Guinean littoral forest. Data were collected from 201 sample units located in different vegetation types that span four bioclimatic zones: Guinean, Sudano-Guinean, Sudanian and Sahelo-Sudanian zones. The woody flora diversity was described by computing the estimated species richness and the Shannon diversity index within EstimateS 9.1, based on the observed species richness. A sample-based randomization procedure with 95 % confidence intervals was used to compare the patterns of plant richness between vegetation stands. A Non-Metric Multidimensional Scaling was performed on presence-absence data matrix to explore the patterns of woody species composition in natural stands. A Canonical Correspondence Analysis was further applied to correlate the patterns of habitat differentiation with climatic variables (temperature, precipitation) and altitude. A total of 165 woody species were recorded, with the highest species richness in Sahelo-Sudanian zone. There was no significant difference in richness between samples from Guinean, Sudano-Guinean and Sudanian zones. Plots in the Sudanian and Sudano-Guinean zones were similar but distinct from those of Guinean and Sahelo-Sudanian zones, a pattern that is supported by precipitation and temperature distributions. Results also suggest important co-occurring species characteristic of each habitat as inferred from the Important Value Index (IVI). It is recommended that habitats of A. africana in Sudanian and Sudano-Guinean zones receive similar management and conservation plans while the Guinean and the Sahelo-Sudanian zones can be treated separately.
... Recent works from Yaoitcha et al. (2015) covering a single forest reserve, reported A. africana, K. senegalensis, M. excelsa, P. erinaceus, to be rare as perceived by local population around Wari-Maro forest reserve (Central Benin). Some other related works also revealed that prioritized species such as K. senegalensis, P. erinaceus and M. excelsa are threatened by overexploitation (Ouinsavi et al., 2005;Gaoué et al., 2007;Glèlè Kakaï et al., 2008;Bonou et al., 2009;Houehanou et al., 2013); which support their importance as priority species for active conservation. Three species (K. ...
... Three species (K. senegalensis, A. africana and P. erinaceus) identified as priority for conservation were reported to be threatened in both open access and protected areas of Pendjari Biosphere Reserve of Benin (Houehanou et al., 2013). Besides it being a good lumber species, M. excelsa is also believed to possess some diabolic powers, thus making it severely overexploited in Benin (Ouinsavi et al., 2005). ...
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Diverses essences forestières, dont cer-taines sont menacées, sont exploitées pour leur bois, légalement ou non. Les essences prioritaires pour la conservation à long terme doivent donc être défi-nies. La présente étude a permis de réali-ser un inventaire des essences exploitées au Bénin et d'identifier les essences prioritaires pour lesquelles des actions urgentes de conservation et de restau-ration sont nécessaires. Des recherches bibliographiques complétées par des entretiens avec différentes parties pre-nantes ont été menées afin de recueillir les données requises pour dresser une liste exhaustive des essences priori-taires. Dix critères et quatre méthodes de priorisation ont été utilisés. Au final, l'approche a retenu 10 essences parmi les 15 essences prioritaires définies par chacune des méthodes. Au total, 24 espèces végétales ont été identifiées, appartenant à 9 familles : Fabacées (25 %), Malvacées (20,83 %), Mélia-cées (16,67 %), Combrétacées (8,33 %), Moracées (8,33 %), Verbénacées (8,33 %), Ébénacées (4,17 %), Rutacées (4,17 %) et Myrtacées (4,17 %). Des mesures de conservation et de restaura-tion sont préconisées d'urgence pour les 10 essences prioritaires ainsi retenues.
... Species distribution modelling (SDM) allows the use of some known occurrences of the species with environmental and habitat variables to model the eco-geographic distribution of that species. SDM has frequently been used to assess the spreading ability of invasive alien species (Peterson, 2003;Fandohan et al., 2015), the conservation status of threatened species and underutilized agroforestry species (Bowe and Haq, 2010;Blach-Overgaad et al., 2010;Adjahossou et al., 2016), and the impact of climate change on species distribution and biodiversity of protected areas (Araújo et al., 2011;Houehanou et al., 2013). Using climatic scenarios and climate models with specific algorithms, these researchers have predicted the variation in species range due to global changes. ...
... Ecological niche modelling had largely been used to inform relevant policies for species of interest such as agroforestry species, threatened species, invasive species, and pests (Bowe and Haq, 2010;Blach-Overgaad et al., 2010) and the effectiveness of conservation through the network of protected areas. However, some protected areas are already threatened by unsustainable use of the existing resources (Houehanou et al., 2013;Adjahossou et al., 2016). The management of disturbed forests should consist of stopping the degradation in order to promote succession and to use ecological knowledge and practical experiences to rebuild forest ecosystems (Bongers et al., 2006). ...
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In this study, species distribution modelling (SDM) was applied to the management of secondary forests in Benin. This study aims at identifying suitable areas where the use of candidate pioneer species, such as Lonchocarpus sericeus and Anogeissus leiocarpa, could be targeted to ensure at low cost, currently and in the context of global climate change, fast reconstitution of secondary forests and disturbed ecosystems and the recovery of their biodiversity. Using occurrence records from the Global Biodiversity Information Facility (GBIF) website and current environmental data, the factors that affected the distribution of the species were assessed in West Africa. The models developed in MaxEnt and R software for West Africa only, for both species, showed good predictive power with AUC > 0.80 and AUC ratios well above 1.5. The results were projected in future climate at the horizon 2055, using AfriClim data under rcp4.5 and rcp8.5 and suggested a little reduction in the range of L. sericeus and any variation for A. leiocarpa. The potential distribution of the two species indicated that they could be used for vegetation restoration activities both now and in the mid-21st century. Improvement are needed through the use of complementary data, the extension to others species and the assessment of uncertainties related to these predictions.
... IVI is the sum of a species' relative abundance, relative density and relative frequency, and varies between zero and 300%. We considered IVI values ≥ 10% to indicate ecological importance (see Houehanou et al., 2013a). For relative abundance, allometric equations were used to estimate individuals' aboveground biomass from recorded biometric data. ...
... From the fourteen tree populations on fallows and fields where SCD regressions could be calculated, though, significant negative slopes indicated the occurrence of recruitment in thirteen cases; only A. polyacantha had an 'ageing' population on fallows. Our findings are also in striking contrast to studies from other protected areas in West Africa's Sudanian savannas, which conclude that protection is not effective in ensuring sufficient recruitment (Gouwakinnou et al., 2009;Houehanou et al., 2013a;Traoré et al., 2013). However, these studies only tested adults' size-classes distributions (usually dbh ≥ 5cm). ...
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Increasing land-use pressure threatens the persistence of tree populations in West Africa’s savannas. We do not fully understand yet why tree species respond differently to human disturbances, hampering the design of appropriate management strategies. To identify typical response pathways, we compared tree populations in three land-use types with increasing levels of human disturbance (protected forest, fallow and field). We analyzed size-class distributions (SCDs) of species and plant functional types, and compared the performance of juvenile and adult age-classes. Biomass was derived from biometric measurements via allometric equations. Higher land-use pressure increased juvenile proportions of plant functional types, but divergent responses were found for species: Juvenile proportions on fields were either very low (0%) or, in most cases, very high (>96%), leading to SCDs with significant negative slopes. While negative slopes are commonly interpreted as indicating populations with sufficient recruitment, they could also indicate growth suppression, particularly if size-classes are missing between juveniles and adults. This ‘juveniles get trapped’ pathway is well-recognized for near-natural savannas with a high incidence of fire (‘fire trap’) or wild browsers (‘browse trap’), and is attributed to a high resprouting ability of trees. As resprouting constitutes a pre-adaptation to human disturbances, the trap concept should be extended accordingly. Species dominating in highly disturbed environments are either characterized by trait combinations allowing them to persist in a ‘human disturbance trap’, or they are actively protected. Our results advocate for designing management strategies that take into account how species’ age-classes respond to disturbances. As the escape of juveniles to mature vegetation is a main demographic bottleneck for most Sudanian savanna species, it is essential to create escape opportunities.
... Benin, Burkina-Faso) (Adomou et al. 2011;Ouédraogo and Thiombiano 2012). The species undergoes anthropogenic and natural disturbances and shows very low potential of natural recruitment even in strictly protected areas (Bonou et al. 2009;Houehanou et al. 2013;Mensah et al. 2014;Atanasso et al. 2019). In natural habitats, the species regenerations are rare despite the presence of International Society for Tropical Ecology many adult trees within stands (Bationo et al. 2001;Sokpon and Biaou 2003;Sinsin et al. 2004;Bonou et al. 2009;Ouédraogo and Thiombiano 2012). ...
... More recently, Koutouan-Kontchoi et al. (2020) highlighted that major proportion of A. africana seeds from savanna forest of Ivory Coast have physical dormancy with small proportion of non-dormant seeds. As such, even if early loss of viability in non-dormant seeds in comparison to dormant seeds could cause low germination rate, and hence few initial seedlings in natural stands of the species (Padonou et al. 2013;Koutouan-Kontchoi et al. 2020), other biotic and abiotic factors play a prominent role in driving the low natural regeneration and recruitment in the species (Harper 1977;Ouédraogo and Thiombiano 2012). The relative importance of these factors often depends on the focal species but also the climatic context. ...
Article
Understanding abiotic and biotic factors affecting the survival of seedlings of threatened species such as Afzelia africana is fundamental for restoration and sustainable management purposes. This study used seedling individual-level morphological data and plot-level data to assess the effect of abiotic (season, elevation, soil type and terrain slope) and biotic (seedling initial density, basal diameter, height and number of leaves, insect and fungal infection, insect herbivory, mammal herbivory, vegetation type, adult conspecific density and diameter, and heterospecific density and diameter) factors on the survival probability (at individual level) and survival rate (at plot level) of seedlings of A. africana in the Pendjari Biosphere Reserve. Generalized Linear Mixed Models (GLMMs) were used for data analyses. At individual level, we found that the survival probability of A. africana seedlings increased with initial height, but decreased from wet to dry season. At plot level, the survival rate of A. africana seedlings also decreased from the wet season (0.72 ± 0.05) to the dry season (0.18 ± 0.04) and was inversely proportional to seedling basal diameter (P = 0.024) and density of conspecific adults (P = 0.016). There were also positive effects of seedling initial height (P = 0.026) and mean diameter of conspecific adults (P = 0.037) on survival rate. Among abiotic factors, only terrain slope showed significant and negative effect (P = 0.028) on the survival rate, suggesting higher survival rate on flat terrain. Our findings suggest that sustainably managing seedlings of A. africana would require accounting for conspecific neighboring effect, terrain slope and season-specific actions. Practical aspects of these factors were further discussed.
... Afzelia africana and Khaya senegalensis are two of these threatened (Adomou et al., 2006). In addition to these two species, which are well known for their usefulness as a source of fodder for livestock and as timber highly prized in the international timber trade, other species such as Daniellia oliveri and Anogeissus leiocarpa are proving to be very vulnerable to anthropogenic pressures and are becoming increasingly rare (Houehanou et al., 2013). Exploitation is therefore being shifted to other plant species, among which Detarium microcarpum, Prosopis africana and Burkea africana can be cited (Houehanou et al., 2013).According to Djègo-Djossou (2003), the Central Nucleus of the Lama Classified Forest, located in southern Benin, constitutes the last great remnant of the natural dense forest. ...
... In addition to these two species, which are well known for their usefulness as a source of fodder for livestock and as timber highly prized in the international timber trade, other species such as Daniellia oliveri and Anogeissus leiocarpa are proving to be very vulnerable to anthropogenic pressures and are becoming increasingly rare (Houehanou et al., 2013). Exploitation is therefore being shifted to other plant species, among which Detarium microcarpum, Prosopis africana and Burkea africana can be cited (Houehanou et al., 2013).According to Djègo-Djossou (2003), the Central Nucleus of the Lama Classified Forest, located in southern Benin, constitutes the last great remnant of the natural dense forest. Despite the monospecies nature of the plantations of the Office National du Bois du Bénin (ONAB) most of the time, they also shelter species of interest to the local population. ...
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The sustainable conservation of forest resources in a context of climate change and population growth would be compromised in their current form of exploitation by rural communities. The objective of this study is to assess the impact of climate change on the dynamics of habitats favorable to species of conservation priority in the forests under ONAB management as these species are heavily used by the populations living along the shores of these forests. The study will consist of: Khaya senegalensis, Afzelia africana, Khaya grandifoliola, Pterocarpus erinaceus, Anogeissus leiocarpa, Milicia excelsa, Albizia zygia, Vitex doniana, Antidesma laciniatum and Bombax costatum. Techniques based on the principle of maximum entropy (Maxent) combined with GIS were used to project the favorable habitats of these ten species under current and future climatic conditions (Horizon 2050). Species occurrence data were collected and combined with bioclimatic data derived from the Worldclim database and the edaphic (soil) variable. Two climate models were used for future projections (CNRM-CM5, HadGEM-ES models) under the IPCC A2 scenario, and the partial ROC approach was used for the evaluation of the predictions of ecological niche models. Variables such as cec2 (cation exchange capacity, horizon 5-15cm), bio17 (precipitation of the driest quarter), bio12 (annual precipitation), bio3 (isothermality), bio6 (minimum temperature of the coldest month) and bio7 (annual thermal amplitude) were found to be the most relevant respectively for the distribution of Khaya grandifoliola, Albizia zygia, Anogeissus leiocarpa, Antidesma laciniatum, Afzelia africana and Khaya senegalensis. Under current conditions, only 7% of the Beninese territory would be very favorable to the conservation of Khaya senegalensis and the CNRM-CM5 model predicts an increase of 27.5% and 13.2% respectively of these very favorable and moderately favorable areas by 2050 through conversion of unfavorable areas (7.4%). On the other hand, this model predicts an opposite trend at the level of Afzelia africana where it predicts a decrease of 8.1% and 1.8% respectively of the very favorable and moderately favorable areas and an increase of 5.1% of the unfavorable areas. Ecological niche modeling has basically revealed the conversion of some currently unfavorable habitats into very favorable habitats for conservation (this is the case of Khaya grandifoliola, Khaya senegalensis and Vitex doniana) and the extension of some habitats unfavorable to conservation (Anogeissus leiocarpa, Bombax costatum, and Pterocarpus erinaceus) by 2050. This study provides scientific support for planning and is a decision support tool for the conservation of these species at the socio-economic level.
... However, for most of sub-Saharan Africa, the future course climate change is still not fully understood, which could lead to further threats; sub-Saharan Africa has been cited as one of the most vulnerable area to the climate change (Boko et al. 2007). The protected areas are already threatened by human population expansion, illicit exploitation of resources, and fragmentation of the habitat as mentioned elsewhere (Houehanou et al. 2013;Clerici et al. 2007;Bruner et al. 2001), such that spatial footprints of protected areas are only part of the story. ...
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Sustainable conservation of tropical resources required understanding of their distribution for effective assessment and definition of conservation priorities. In tropical areas, wild palms are highly valued keystone resources with growing demand for both subsistence uses and commercial trade. Here we focused on eight such species (Borassus aethiopum Mart., Eremospatha macrocarpa (G.Mann & H.Wendl.) H.Wendl., Hyphaene thebaica Mart., Laccosperma opacum (G.Mann & H.Wendl.) Drude, Phoenix reclinata Jacq., Raphia hookeri G.Mann & H.Wendl., Raphia sudanica A. Chev., and Raphia vinifera P.Beauv.). This study tested (i) how those palms distributions may be affected under future climate scenarios, and (ii) if species are effectively conserved currently and under future forecasts for their native distributional areas. Finally, we defined spatial priorities for the species’ conservation. Available bioclimatic and soil data layers were used for the modelling with maximum entropy approaches, and resulting maps were overlaid on the existing protected areas network. Results showed that much of the distribution of the species will remain largely stable, albeit with some expansion and retraction in some species; relationships with protected areas networks suggest that protected portions of species distributions will also remain stable. The areas identified as highest conservation priority differ between models even though the highest-priority areas holding most palm species are located along the coast (from Guinea to Nigeria). Further development of these analyses could aid in forming a more complete picture of the distributions and populations of the species, which in turn could aid in developing effective conservation strategies for this botanically important family.
... In contrast, other useful woody species protected on fields such as Sclerocarya birrea and Tamarindus indica (Fandohan et al., 2010;Gouwakinnou et al., 2009) as well as several non-protected useful woody species (e.g. Afzelia africana, Khaya senegalenis, Pterocarpus erinaceus) are negatively affected by human activities and are therefore declining (Gaoue and Ticktin, 2007;Houehanou et al., 2013;Nacoulma et al., 2011b). In turn, other non-protected species (e.g. ...
... It has been adequately described in various studies that the diameter size class distribution of woody plants are affected by the types of conservation management regimes (Schumann et al., 2010;Fandohan et al., 2011;Houehanou et al., 2013). The diameter class size distribution (DBH) for the pooled tree species data revealed a decrease in stem density with increased DBH size classes in both studied sites (Figure 5). ...
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Serengeti is the largest ecosystem in Tanzania endowed with high level of biodiversity in protected and unprotected areas. Serengeti National Park is the only protected area in a matrix of unprotected areas characterized with a wide range of human activities which threaten biodiversity conservation. It was assessed plant species composition, diversity, distribution and vegetation structure in both the protected and unprotected areas of the ecosystem. Two transects with twenty plots each were established in each vegetation type in which data was collected. A significantly higher species composition (262) and diversity (2.39 ± 0.03) was observed in unprotected areas than in the protected area (163 and 2.06 ± 0.04 respectively). The DCA ordination of the species data from the two management regimes formed four clusters based on similarity in plant species composition, where three clusters were from unprotected areas and one from protected area. The variations in plant species composition ranged from 35.69% to 65.92% for the first four DCA axes. There was no significant difference in stem density between protected and unprotected areas of the ecosystem. Although high density of trees at 10 - 14 cm DBH sizes was observed in both sides of the conservation management regimes, individuals with DBH above 65 cm existed in the protected area but were absent in unprotected areas. It can be concluded that the decrease of plant species diversity and density in unprotected area is because of habitat degradation associated with exploitation pressure, livestock grazing and other forms of disturbance related with anthropogenic activities. Because of high demand for plant resources, the local community needs to establish woodlots to cater for wood resource needs outside the protected areas of Serengeti. Also, pastoralists need to diversify livestock keeping systems compatible with limited grazing land in unprotected area of the Serengeti ecosystem.
... Human pressure is known to have an impact on savanna habitats (e.g. Houehanou et al., 2013), and is thus a threat for this ecosystem. Understanding the dynamics of savannas and forests, and of the factors that determine their state and transition from one to the other is a burning issue (Hirota et al., 2011;Staver et al., 2011a;Staver et al., 2011b). ...
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Understanding the factors that determine vegetation nature and dynamics in Central Africa is an important issue given climatic changes and increasing human pressure. Forest and savanna are often considered as two alternative stable and highly contrasted states, driven by complex interactions between climate, soil and disturbances. The current relationships between tree cover and its determinants (annual water deficit, fire frequency, population density, intensity of land use and soil type) were characterized using remote sensing data and a statistical model. It has been shown that there is not one, but several savanna stable states. For savanna states of low tree cover (≤ 35%), it is mainly the soil type and the annual water deficit which determine their presence and the transition from one to another. The most wooded savannas (> 35%) and the forests seem to be the most sensitive to anthropogenic disturbances. However, this statistical model can only describe the contemporary relationships between vegetation structure and its determinants. Conversely, studying environmental bio-proxies preserved in natural archives, which constitutes the paleo-ecological approach, enables reconstructing long-term vegetation, disturbances and some climatic features, in order to obtain a dynamic view of their relationships. Paleo-sequences from three lakes, currently located in a forest, in a savanna-forest mosaic, and in a savanna, were investigated. On the one hand bio-proxies from recent lake sediments were compared to satellite images, and on the another hand a statistical model between bio-proxies from modern soils and vegetation surveys was calibrated. The results of these studies enabled to better understand the information carried by phytoliths and charcoals, and therefore to better estimate vegetation structure and fire history. Moreover, they emphasize the importance of precisely identifying taphonomic processes in order to accurately reconstruct paleo-environments. The preliminary results of a lacustrine paleo-sequence covering the last 3000 years are presented in discussion. Although the environment around the lake has remained a savanna, vegetation structure has undergone significant changes due to both climate change and modifications in fire regimes. Moreover, it seems that these structural changes were not gradual but happened abruptly, as it happens currently along the climatic gradient. This work therefore predicts a critical response of tropical biomes to global changes.
... Lumber species such as K. senegalensis, A. Africana, and P. erinaceus identified as priority species for conservation in this study were reported to be threatened in both open access and protected areas of Pendjari Biosphere Reserve of Benin (Houehanou et al., 2013). Elsewhere, M. excelsa has been subjected to people demonization that combined with other exploitation for timber resulted in its critical decline in the 1970s and 1980s nationwide in Benin (Ouinsavi et al., 2005). ...
... These results corroborate a study that showed the negative impact of human disturbance on adult densities of some valuable tree species such as Afzelia africana, Pterocarpus erinaceus and Khaya senegalensis. 52 However, according to other study, 53 tree abundance is not only the result of human disturbance but several others factors, such as climate or microclimate, soil properties, fire regimes and herbivory all have an effect. According to regeneration density, the same trend was found. ...
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This study assessed endogenous knowledge and impact of human disturbance on the abundance of two underutilized wild fruit tree species: Drypetes floribunda (Mu¨ll. Arg.) Hutch. (Euphorbiaceae) and Mimusops andongensis Hiern. (Sapotaceae) in the Lama Forest Reserve (LFR) in southern Benin. A survey was conducted with 145 randomly selected people amongst the surrounding communities of LFR in order to assess the endogenous knowledge of the species. One hundred square plots were established in the forest for characterizing species abundance in different habitats according to human disturbance degree. Results indicated that this species has multiple uses and either local knowledge on their uses or their organ plant uses depend on social factors. A densities assessment suggests a negative effect of human disturbance on the abundance of both species. Results support the need to envisage conservation and sustainable use strategies as perspective policies.
... Pterocarpus erinaceus Poir (Fabaceae), useful for its timber, is endemic to the arid Sahelian and semi-arid Sudanian tropical zones (Sylla et al., 2002;Ouedraogo et al., 2006Ouedraogo et al., , 2012. This species is sought-after, exploited and threatened in West Africa (Houehanou et al., 2013) for timber and is exported to Asian countries, mainly China (Adjonou et al., 2010). For example, between 2011 and 2012, the export of P. erinaceus from Togo increased to 9690 m 3 . ...
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Pterocarpus erinaceus Poir (Fabaceae) is an endemic, highly exploited and threatened plant species in arid and semi-arid zones of West Africa. This study was conducted at the sub-regional level across three countries, namely Burkina Faso, Niger and Togo. These countries represent a spatial ecological gradient of P. erinaceus distribution to collect information on population structure and silviculture operating standards that could guide the industry, ensure species regeneration and establish appropriate management strategies for the species. Data were collected in P. erinaceus populations by means of forest inventories. Results showed that the average tree density was 1.17 ± 0.75 trees/ha in the Sahelian zone, 49.20 ± 63.2 trees/ha in the Sudanian zone and 110.9 ± 1.15 trees/ha in the Guinean zone. The average stem diameter values were 26.63 ± 7.89 cm (Guinean zone), 29.02 ± 15.44 cm (Sudanian zone) and 49.63 ± 19.44 cm (Sahelian) with noticeable variability (CV = 53.6%). Significant differences for these parameters were noted between the zones (P < 0.001). The average total height in the populations of the Sudanian zone (9.51 ± 2.75 m) were significantly less (P < 0.001) than in the other two zones (10.18 ± 2.27 m for the Sahelian zone and 14.16 ± 2.88 m for the Guinean zone). The merchantable heights were between 4.08 ± 1.35 m (Sahelian zone) and 3.63 ± 2.63. m (Guinean zone) and varied significantly from one zone to another (P < 0.001). The distribution of trees in diameter classes varied depending on the climate zone: modal distribution with most classes ranging from 30-65 cm in the Sahelian zone and 15-45 cm in the Sudanian zone and an "L" model distribution in the Guinean zone (most classes ranging between 10 and 25 cm), while the distribution of height classes showed a modal form for all climate zones. Two minimum diameters of exploitation (MDEs) could be determined: 35 cm for the Guinean and Sudanian zones (P = 316.6% and P = 53.4%, respectively) and 65 cm for the Sahelian zone (P = 111.9%) for a rotation period estimated at 20 years for all the climate zones.
... However, with the increase in human population, intensification of agriculture and climate change, these plant species are now subjected to intense anthropogenic pressure, which compromises their sustainability (Banla et al., 2018;Pokhriyal et al., 2020). To date, several studies have reported the negative effects of anthropogenic disturbances and land-use types on the structural parameters of tropical tree species (Houehanou et al., 2013;Mensah et al., 2014;Idohou et al., 2016;Assogbadjo et al., 2017). However, literature is lacking on the assessment of the impacts of human activities on the structural characteristics of the native plant species preserved by local people in agroforestry systems of the Ouémé catchment area. ...
Article
Parkia biglobosa (Jacq.) G. Don, Pterocarpus erinaceus Poir, Milicia excelsa (Welw.) C. C. Berg, Prosopis africana (Guill., Perrot. and Rich.) Taub., Afzelia africana Sm. and Khaya senegalensis (Desv.) A. Juss. are the most highly valued indigenous tree species in the agroforestry systems of the Ouémé catchment area. However, information on the population structure of these species is lacking, thus limiting the development of their sustainable conservation, utilization and restoration strategies. This study addressed this gap. It assessed the population structures and regeneration status of the six species from Don, Tan-Houègbo, Atchabita, Bétékoukou, Glazoué, Tchaorou, Zagnanado, Tévèdji, Sinaou and Bétérou along the catchment. Data were collected from 78 permanent rectangular plots (50 × 30 m) randomly installed within 10 provenances. Dendrometric data including diameter at breast height (dbh) of adult trees (dbh ≥ 10 cm), collar diameter, total height of seedlings and saplings, number of individuals per species according to adult, sapling and seedling were recorded. The population structure was described using ecological and dendrometric parameters (relative frequency, importance value index (IVI), mean densities, basal area, mean height), and diameter size-class distributions. Seedling:sapling and sapling:adult ratios were also computed and analyzed for determining regeneration patterns. Based on IVI, Parkia biglobosa (95.85%) and Khaya senegalensis (65.92%) were the most represented species in the catchment area. The analysis of variances showed that dendrometric parameters of the six species varied significantly between provenances. Seedling:sapling and sapling:adult ratios were
... These species are endemic to the Sahelo-Sudanian and Sudano-Guinean zones (Ouedraogo et al., 2012;Ouédraogo et al., 2013;Segla et al., 2016). They are sought-after, exploited and threatened in West Africa (Houehanou et al., 2013) for timber, fodder and medicinal properties and are exported to Asian countries, mainly China (Adjonou et al., 2010). Moreover, individual trees of these species are repeatedly mutilated, which is causing serious damage to the natural tree stands (Rabiou et al., 2015). ...
Article
This study aims to assess population structure and ecological indicators of woodland vegetation dominated by Pterocarpus erinaceus and Anogeissus leiocarpa as a basis for sustainable management and conservation strategies. We sampled 34 plots each measuring 30 m × 30 m in W National Park in Niger and analyzed structural parameters (tree density, basal area, Lorey's mean height and size class distribution) and ecological indicators (species richness, Shannon diversity index, Pielou evenness index and Importance Value Index) of woodland in general and for the two key species. Mean tree density was 752.6 stems/ha and basal area was 24.5 m²/ha in woodlands including 145.4 stems/ha and 14.1 m²/ha for A. leiocarpa and 3.3 stems/ha and 0.7 m²/ha for P. erinaceus. The woodland was composed of 59 tree species belonging to 34 genera and 17 families. A. leiocarpa had the highest IVI value (0.93), whereas P. erinaceus was among the species with the lowest IVI value (0.03). The mean diameter of both species was higher (24 cm and 47 cm for A. leiocarpa and P. erinaceus respectively) than the mean diameter in woodlands (16 cm). A “reverse J” shape distribution was found for woodland in general and for A. leiocarpa, but P. erinaceus showed a left dissymmetric distribution. Findings of this study showed that urgent actions are needed for sustainable management and conservation of some key species especially P. erinaceus.
... This constitutes a threat for the species due to the expansion of human activities around the area. In addition, protected areas are themselves vulnerable to future climate (IPCC, 2007) and fragmentation (Houehanou et al., 2013). An alternative to be explored is the one of agroforestry systems. ...
Article
African baobab (Adansonia digitata) is an agroforestry species used by local people for many purposes such as food, medicine, craft, etc. It is uncertain how climate change will impact the suitability of the habitat for the species in Benin. This study aimed to assess the present-day distribution and forecast the probable impact of future climate, and provide sustainable management strategies for the species in Benin. Records of the species were gathered both from fieldwork and through available databases. Environmental data comprised both climatic and soil layers. We transferred the present-day models into future climates under two scenarios (RCP 4.5 and RCP 8.5) using Maxent software. Our results showed high suitability of the Benin territory for African baobab in the present. In addition, high stability of suitable areas was observed for the species in the future across Benin. However, some protected areas are predicted not to effectively conserve the species in the future. We believe that both ex-situ and in-situ conservation measures will help to maintain the African baobab population in the future.
... Thus, if PAs are well maintained, M. kummel could be well protected but this will require monitoring. However, this is not currently the case for many PAs in Benin (Houehanou et al., 2013) as most PAs are still accessed or exploited by local people, as also occurs in other countries around the world (Geldmann et al., 2014;Gray et al., 2016;Sarathchandra et al., 2018). This may undermine the effectiveness of PAs in their role of protection of threatened and important species. ...
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Understanding the niche and habitat requirements of useful and threatened species, their shifts under climate change and how well protected areas (PAs) preserve these habitats is relevant for guiding sustainable management actions. Here we assessed the ecological factors underlying the distribution of two multipurpose and threatened species, Mimusops andongensis and M. kummel, in Benin, and potential changes in the suitable habitats covered by PAs, under climate change scenarios. Fifty seven occurrence points were collected for M. andongensis and 81 for M. kummel. Associations with 19 bioclimatic (from WorldClim database) and six soil variables (from World Soil Information website) were analysed using Principal Components Analysis, niche modelling and gap analysis. M. andongensis occurrence is associated with high soil clay, silt, organic carbon and cation exchange capacity. Contrastingly, M. kummel occurrence is linked to high sand content and prolonged water holding capacity. Climatically, M. andongensis occurrence is positively related to mean annual temperature, while M. kummel occurrence is influenced by the seasonality of precipitation and precipitation of the wettest period. Predictions showed affinity of suitable areas with water lines, suggesting that components of soil texture and chemical properties should be considered during modelling. For M. andongensis suitable areas are confined to the Guineo-Congolian zone, while for M. kummel they are mostly located in the Guineo-Sudanian zone and absent from the driest part of the Sudanian zone. Under climate change, moderately to highly suitable areas (probability of occurrence of species > 20%) covered by PAs will decrease in the case of M. andongensis, but remain stable for M. kummel. In Benin, PAs are under threat from exploitation and uncontrolled bushfires, which may also affect populations of the two species. Consequently, additional actions are required, including the monitoring of species populations and the extent of different pressures, and the regularization of access to PAs. Populations of these species outside PAs should also be given consideration because of their very limited abundance.
... Currently, Park W and the Hunting Area of the National Park of Penjari are effectively managed because of their tourist interest for Benin. Indeed, human pressure, illicit exploitation of plant resources, and land fragmentation (Bruner et al. 2001;Clerici et al. 2007;Houehanou et al. 2013) induce an increasing conversion of protected areas into cultivable land, causing the depletion of plant species diversity , mainly wild edible plants such as Cochlospermum species. According to Issiaka et al. (2016), the Sudanian zone has been experiencing major disturbances through significant deforestation due to the high population growth and the increasing land conversion to agriculture. ...
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Cochlospermum tinctorium and Cochlospermum planchonii highly contribute to complementary diet, health care, monetary income, and livelihood security across rural communities of West African countries as Benin. Though, facing the environmental impacts of climate change, several plants species, of which Cochlospermum species population are expected to be threatened, losing their native habitats. Using Maximum Entropy (MaxEnt) algorithm, both Cochlospermum species were modeled to estimate their potential distribution pattern under current and future climate change scenarios in Benin under the scenarios RCP 4.5 and 8.5, by horizon-time 2055. Overall, 535 and 644 occurrence records were used to run the model using cross-validation method and Write background predictions with five replicated times. The performance and accuracy of the model were checked through an area under curve (AUC) which were around 0.86 and 0. 91 and TSS values about 0.6 and 0.53, respectively, for C. tinctorium and C. planchonii. Within the five bioclimatic variables retained for each species, the number of dry months (DM) with 51.3% and the annual moisture index (MI) with 46.3% contributed the most to the distribution modelling. Currently, about 66 and 36% of the area of Benin, 62 and 52% of the protected areas were of high suitability, respectively, for C. planchonii and C. tinctorium. RCPs 4.5 and 8.5 scenarios forecast an expansion in future distribution, respectively, for C. planchonii (7.91 and 10%) and C. tinctorium (2.49 and 4.81%). Though, these results highlight the climate change impacts on Cochlospermum species distribution in Benin, further studies are needed to assess their abundance, conservation status and threats.
... The main habitat of the African baobab is the savannah ecosystem, which has been affected by human activity (Lykke, 1998), possibly including the population structure of this valuable tree species. Tree harvesting, land clearing for agriculture and grazing have negatively impacted the composition of species and also its distribution and population status (Houéhanou et al., 2013). McNeely (1997) has mentioned that at the regional level, the extinction of the plant species is about 76% owing to the various disturbances of the habitats. ...
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Changes in land use type (LUT) are a major driver of biodiversity loss and species decline. Responses to changes in LUT are species-specific, which may in turn be context-dependent. Understanding such responses is essential for the management of socio-economically important wild tree species. The baobab, Adansonia digitata L., is an important traditional agroforestry tree species in Sub-Saharan Africa. This study assesses how LUT affects the demographic and spatial structure of baobab stands. Using data from a census and mapping of baobab trees in 12 plots of 250 m × 250 m each, the study compared baobab tree density, total height and diameter, diameter size-class distribution (SCD), stand stability, and spatial relationships in a strictly protected area (national park), a buffer zone and farmlands (Matéri and Boukombé) in the Pendjari Biosphere Reserve in Benin. The results show that the highest young and adult tree densities are in farmlands (particularly in Matéri), followed by the buffer zone and the national park. No significant differences in tree diameter and total height of baobab trees were found among the different LUT. The SCD had a reverse J-shape with a better negative slope and population stability metrics in farmlands (particularly in Matéri) but a flattened slope in the buffer zone. The spatial distributions of juvenile and adult baobab trees were random, and independent of each other. The spatial distribution of juvenile and adult baobabs was also independent of the other tree species, irrespective of LUT. It was concluded that baobab conservation is better in farmlands than in the national park but that the difference between park and farmlands may be context-dependent, probably linked to local environmental conditions, the socio-ecological context and interactions with baobab trees.
... The main habitat of the African baobab is the savannah ecosystem, which has been affected by human activity (Lykke, 1998), possibly including the population structure of this valuable tree species. Tree harvesting, land clearing for agriculture and grazing have negatively impacted the composition of species and also its distribution and population status (Houéhanou et al., 2013). McNeely (1997) has mentioned that at the regional level, the extinction of the plant species is about 76% owing to the various disturbances of the habitats. ...
Article
Full-text available
Changes in land use type (LUT) are a major driver of biodiversity loss and species decline. Responses to changes in LUT are species-specific, which may in turn be context-dependent. Understanding such responses is essential for the management of socio-economically important wild tree species. The baobab, Adansonia digitata L., is an important traditional agroforestry tree species in Sub-Saharan Africa. This study assesses how LUT affects the demographic and spatial structures of baobab stands. Using data from a census and mapping of baobab trees in 12 plots of 250 m × 250 m each, the study compared baobab tree density, total height and diameter, diameter size-class distribution (SCD), stand stability, and spatial relationships in a strictly protected area (national park), a buffer zone and farmlands (Matéri and Boukombé) in the Pendjari Biosphere Reserve in Benin. The results show that the highest young and adult tree densities are in farmlands (particularly in Matéri), followed by the buffer zone and the national park. No significant differences in tree diameter and total height of baobab trees were found among the different LUT. The SCD had a reverse J-shape with a better negative slope and population stability metrics in farmlands (particularly in Matéri) but a flattened slope in the buffer zone. The spatial distributions of juvenile and adult baobab trees were random, and independent of each other. The spatial distribution of juvenile and adult baobabs was also independent of the other tree species, irrespective of LUT. It was concluded that baobab conservation is better in farmlands than in the national park but that the difference between park and farmlands may be context-dependent, probably linked to local environmental conditions, the socio-ecological context and interactions with baobab trees.
... The main habitat of the African baobab is the savannah ecosystem, which has been affected by human activity (Lykke, 1998), possibly including the population structure of this valuable tree species. Tree harvesting, land clearing for agriculture and grazing have negatively impacted the composition of species and also its distribution and population status (Houéhanou et al., 2013). McNeely (1997) has mentioned that at the regional level, the extinction of the plant species is about 76% owing to the various disturbances of the habitats. ...
... The main habitat of the African baobab is the savannah ecosystem, which has been affected by human activity (Lykke, 1998), possibly including the population structure of this valuable tree species. Tree harvesting, land clearing for agriculture and grazing have negatively impacted the composition of species and also its distribution and population status (Houéhanou et al., 2013). McNeely (1997) has mentioned that at the regional level, the extinction of the plant species is about 76% owing to the various disturbances of the habitats. ...
Preprint
Changes in land use type (LUT) are a major driver of biodiversity loss and species decline. Responses to changes in LUT are species-specific, which may in turn be context-dependent. Understanding such responses is essential for the management of socio-economically important wild tree species. The baobab, Adansonia digitata L., is an important traditional agroforestry tree species in Sub-Saharan Africa. This study assesses how LUT affects the demographic and spatial structure of baobab stands. Using data from a census and mapping of baobab trees in 12 plots of 250 m × 250 m each, the study compared baobab tree density, total height and diameter, diameter size-class distribution (SCD), stand stability, and spatial relationships in a strictly protected area (national park), a buffer zone and farmlands (Matéri and Boukombé) in the Pendjari Biosphere Reserve in Benin. The results show that the highest young and adult tree densities are in farmlands (particularly in Matéri), followed by the buffer zone and the national park. No significant differences in tree diameter and total height of baobab trees were found among the different LUT. The SCD had a reverse J-shape with a better negative slope and population stability metrics in farmlands (particularly in Matéri) but a flattened slope in the buffer zone. The spatial distributions of juvenile and adult baobab trees were random, and independent of each other. The spatial distribution of juvenile and adult baobabs was also independent of the other tree species, irrespective of LUT. It was concluded that baobab conservation is better in farmlands than in the national park but that the difference between park and farmlands may be context-dependent, probably linked to local environmental conditions, the socio-ecological context and interactions with baobab trees.
... In the Sudanian zone of West Africa, the strong anthropogenic pressure, combined with climate change, slow growth of forest trees and their destruction by grazing, agriculture and wood energy needs means that naturally mixed forest formations are very rare and are only found in sites protected from fire, agriculture and/or pastoralism (Houehanou et al., 2013). Our results show the great potential of local species for plantations. ...
Article
The rapidly growing human population in sudanian West Africa has generated increasing demand for agricultural land and forest products so that most of the original vegetation cover has disappeared and the remainder is highly degraded, meaning that it is urgent to draw up a long-term assessment of the potential of local species to be promoted in pure and mixed plantings as contribution to global forest restoration efforts. We inventoried the survival and growth of 5817 trees belonging to 35 species planted more than 25 years ago in pure and mixed plantings. For a subset of individuals, we estimated heights and volumes of standing timber. We found that (i) the long-term 25 survival (from 50 to 99%.yr-1) and diameter growth (from 1 to 10mm.yr-1) are highly diverse between species and not correlated to each other, (ii) the annual increase in biomass per tree averages 2.22kg while the annual increase in stand biomass may be over 6 Mg. ha-1 for three highly-productive species (Khaya senegalensis, Pterocarpus erinaceus and Anogeissus leiocarpa) (iii) the effect of mixture on annual growth is significantly positive with an across-species gain of 0.7mm.yr-1 while there is no effect on the survival probability. Considering a potential volume productivity of 10m 3 per hectare at 30 years, 13 species have been retained in the list of woody species of interest for planting in the Sudanese zone of West Africa.
... Likewise, the bark, leaves and roots of the tree are used in pharmacopoeia to treat several illnesses including anemia, cough, dysentery, malaria and infant fever [5] [6] [7]. This species is sought-after, exploited and threatened in West Africa [8] for timber and is exported to Asian countries, mainly China. African teak provides a high-value timber for export used in cabinetmaking, building and armaments. ...
... Protected areas are expected to function as a single conservation strategy (Geldmann et al., 2013). However, with rapidly increasing world population, land shortage in rural areas and pressure from agricultural intensification (Hadush et al., 2019;Laurance et al., 2012;Tilman et al., 2001), the efficiency of protected areas in conserving biodiversity has been questioned (Chape et al., 2008;DeFries et al., 2005;Houehanou et al., 2013;Mora and Sale, 2011). For example, 55% of African protected areas are inefficient at biodiversity conservation (Muhumuza and Balkwill, 2013). ...
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Understanding the role of protected areas in conserving biodiversity is a central goal in conservation biology. Anthropogenic activities around and inside these protected areas and, in particular, roads can alter the spatiotemporal dynamics of biological diversity in protected areas. However, our understanding of how the presence and position of roads affect human attitude, subsequent agricultural practices and biodiversity conservation is limited. In this study, we tested the effects of the proximity of traditional agroforestry parklands to main roads used by park rangers for surveillance on the diversity and abundance of woody species in the Pendjari Biosphere reserve over 16 years (2000–2016). Tree density in agroforestry parklands decreased over time from an average of 20 trees/ha in 2000 to 7 trees/ha in 2016. Species such as Vitellaria paradoxa and Parkia biglobosa, which are economically important, experienced the largest density reduction Trees density was also significantly higher in farms close to the monitoring roads used by park rangers to patrol the park. Farms that are far from the roads were monitored less frequently given that the number of park rangers declined over time. However, there was no significant variation in species richness and diversity over time, perhaps because of the low tree diversity in these systems. This masks evidences of species local extinctions. For example, species such as Pterocarpus erinaceus, Anogeissus leiocarpa, and Burkea africana which were present in the traditional agroforestry parklands in 2000 disappeared by 2016. This is associated with important land-use changes including the conversion of gallery forests into cropland and wooded savannas indicating that human pressure not only affects species occurrence but also their habitats. Our study suggests that where land demand for agriculture is high, it is challenging for local people to maintain sustainable management practices in the absence of collective action. Keywords: Tree abundance, Traditional agroforestry parklands, Biodiversity conservation, Protected areas, Roads, Pendjari biosphere reserve
... So, just a part of protected areas can conserve a given species. This information is an addition to the conclusions ofHouehanou et al. (2013) andAdjahossou et al. (2016), who noted that some protected areas are threatened by unsustainable use of the existing resources. The use of the HCPA is means to keep at the lowest level as possible the prediction error, giving more confidence to the users of our results. ...
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Khaya senegalensis Desr & Juss and Garcinia kola Heckel are two medicinal forest trees species that provide as well lots of meaningful Non Timber Forest Products as Forest Timber Products. Those two species are undergoing many threats including climate change and forest pest attack. In order to provide forest resources managers and planted forest promoters with forest pest prevention means, forest species restoration and conservation strategies, this study was aimed at assessing the vulnerability of Khaya senegalensis to climate change and to the invasion of Hypsipyla robusta Moore in Benin over time and space; and analyzing how far climate changes can help to restore and conserve Garcinia kola, an extinct species in the wild in Benin. To this end, MaxEnt approach for Ecological Niche Modelling was used to compute suitable areas for target species under current, and future climates (RCP 4.5 and RCP 8.5 of AfriClim Ensemble mean,). Biodiversity presence data were gathered on the database of the Global Biodiversity Information Facility (GBIF). Gap analysis and Spatio-temporal Analysis were performed using Geographic Information System Tools. In the case of K. senegalensis, projections at horizon 2055 from AfriClim Ensemble mean showed that it can occur in the future with some areas left out and some gained. The loss was assessed at 15-16% of Benin superficies while the gain was 2-3% of the country’s total area. As for Hypsipyla robusta, climate change will provide only habitat loss of about 66% of the country’s total area. So, some plantation sites being currently exposed to biological attack from the pest could no more exist in the future, giving hope for Khaya senegalensis’ high quality wood production. Meanwhile, there will be an ecological imbalance due to the drastic potential habitat loss for the insect. It is worth that future investigations focus on the economics of attacks in plantations. As for Garcinia kola, results revealed that climate change proved to have only positive consequences on its distribution. Considering the High Confidence Projection Areas (HCPA), the percentage of municipalities predicted suitable for the species is far above the percentage of Protected Areas Network (PAN) predicted as such (7.44% versus 0.93%). RCP4.5 and RCP8.5 of AfriClim Ensemble mean indicated respectively 3.00% and 6.27% of PAN as positive climate change impact zones, predicted respectively 13.60% and 17.60% of the total municipalities’ areas as such. Therefore, it is worth relying not only on PAN but also and mainly on urban forestry and reforestation to restore and conserve the species. Further studies focusing on the introduction of Garcinia kola in urban areas, and its use for reforestation are compulsory. Key Words: Khaya senegalensis, Hypsipyla robusta, Garcinia kola, Ecological niche Modelling, Forest pest outbreak, Climate change.
... For instance, Piao, Comita, Jin, and Kim (2013) reported low recruitment potential, as a result of aged conspecific trees competition in a temperate old-growth forest of north east China. Previous studies in West Africa predicted that protected areas, although being good for conserving native biodiversity, may not fully facilitate the species regeneration process (Bonou et al., 2009;Houehanou, Assogbadjo, Gle`le`Kakaı¨, Kyndt, Houinato, & Sinsin, 2013;Oue´draogo & Thiombiano, 2012). Our results also suggest that, although A. africana populations can be conserved in protected areas, successful species recruitment across successive size classes is not guaranteed. ...
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Information on how abiotic and biotic factors affect species population structures and regeneration are critical for understanding plant growth in natural habitats. Here, we used data from three spatially distinct populations of Afzelia africana Sm. in the Pendjari Biosphere Reserve in Benin, to determine how the species population structures respond to abiotic and biotic factors. Afzelia africana population structures were studied using several parameters including basal area, tree height, density of successive diameter classes, and size class slope. We tested for individual effects of abiotic (mound density, soil type, terrain slope) and biotic (heterospecific tree density) factors on the species population structure. We also tested for similarity of species composition among studied A. africana population stands. Results revealed a tree density structure with mature individuals, and size class distribution indicating a recruitment bottleneck at the juvenile stage (10-20 cm diameter), possibly due to mammal browsing, natural and artificial fires. Heterospecific tree density was positively associated with A. africana adult density, but negatively related to the species growth parameters (mean diameter, basal area and tree height). These results indicate some degrees of niche overlap between A. africana and coexisting species, but also partly reflect A. africana tolerance and adaptation to limited resources environment. Soil type significantly influenced both basal area and regeneration density, greater values being observed on silt-sand-rocky soils. Basal area was higher on steeper slope, probably a result of species conservative strategies. These findings were discussed in line with management and restoration action needs in the Pendjari Biosphere Reserve.
... So, just a part of protected areas can conserve a given species. This information is an addition to the conclusions of Houehanou et al. (2013) and Adjahossou et al. (2016), who noted that some protected areas are threatened by unsustainable use of the existing resources. The use of the High Confidence Prediction Areas (HCPA) is a means to keep at the lowest level as possible the prediction error, giving more confidence to the users of the study results. ...
Article
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A study was conducted to assess how well climate changes can help to conserve and restore Garcinia kola Heckel in the Protected Area Network (PAN) and in urban areas in Benin. To achieve this, occurrence data from GBIF was used and the environmental data from AfriClim was used in order to model the species’ potential habitat under current and future climates. The maximum entropy modeling approach of MaxEnt was used with scenarios RCP4.5 and RCP8.5 for future predictions. Geographic information systems were used to establish the high confidence prediction areas (HCPA) for G. kola. Gap analysis was performed throughout PAN and municipalities with regard to the HCPA. Considering the climate envelop, results revealed that climate change proved to have only positive consequences on the distribution of the species. Moreover, considering the HCPA, the percentage of municipalities that were suitable for the species is far above the percentage of PAN that was predicted as suitable (7.44% versus 0.93%). RCP4.5 and RCP8.5 indicated respectively 3.00 and 6.27% of PAN as positive climate change impact zones. As for the municipalities, it was respectively 13.60 and 17.60% of the total municipalities areas. Therefore, it is not worth relying only on PAN to conserve and restore the species, rather urban forestry and reforestation in PAN may be key actions to save this genetic resource. Further studies with regard to introduction of G. kola in urban areas and its use for reforestation are compulsory. Key words: Garcinia kola, Urbanization, climate change, medicinal woody plants, biodiversity conservation.
... Desr & Juss is one of the species exposed to anthropic pressure (Houehanou et al., 2013) because of its multi-uses that benefit people (Sokpon and Ouinsavi, 2002). ...
Article
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Khaya senegalensis Desr & Juss is an urban tree species with high quality wood, unfortunately disturbed by Hypsipyla robusta Moore. However, how vulnerable this species is with regard to climate change and to Hypsipyla robusta over time and space is unknown. This study aimed at assessing as well the climate change impacts on both species as the overlapping extent of their suitable areas over time and space. To this end, the MaxEnt approach for Ecological Niche Modelling was used to compute suitable areas for both species under current and future climates (Africlim RCP 4.5 and RCP 8.5). Spatio-temporal Analysis was performed using Geographic Information System. Upon 2055, climate change will impact negatively 15-16% of Benin while the positive impacts will account only for 2-3%, and the stable areas will represent 74-75%. As for Hypsipyla robusta, climate change will provide only habitat loss of about 66% of the country. So, many plantation sites are exposed to biological attack from the pest, but wouldn"t be more in future, giving hope for Khaya senegalensis' high quality wood production. Meanwhile, there will be an ecological imbalance due to the drastic potential habitat loss for the insect.
... Protected areas (PAs) are core tools for global and local biodiversity conservation strategies. Well managed PAs have been shown to effectively reduce rates of habitat loss, although not in every case (Geldmann et al., 2013;Houehanou et al., 2013;Watson et al., 2014). PAs therefore play an important part in buffering negative anthropogenic effects on biodiversity. ...
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Although the palm flora of continental Africa totals just 66 species, they are amongst the most useful plants across the continent, providing many important resources for human populations. Studies have shown that African palms will likely be negatively affected by global change, leading to increased threats to their survival. Here we conduct the first full global conservation assessment for 61 continental African palm species following IUCN Red List Categories and Criteria. Our study revealed that fewer than 10% of the evaluated species were assessed as Threatened. Within the Threatened category, one species was assessed as Critically Endangered, three as Endangered and two as Vulnerable. These results underline an overall low extinction risk for African palms in the immediate future, which is substantially lower than the global estimate of 21% for all plants. These results could be linked to the generally large distribution patterns of African palm species, the broad ecological amplitudes of most species and their good representation inside the African protected areas network. However, a non-negligible number of species (~15%) lack sufficient data to be properly assessed. This highlights the importance of further studies to improve our basic understanding of their distribution and threats. Our study provides a rather optimistic view of this highly important African plant resource yet, some widespread species are becoming locally rare due to over-harvesting for human use. At a local level, palm resources are generally non-sustainably exploited, which, coupled with climate change, could lead to a rapid increase in threat status over time.
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Overexploitation is a main driver of biodiversity loss globally. Protected areas may have a key role in reducing overexploitation, yet their actual effectiveness in maintaining high-density and viable populations of overexploited species has rarely been evaluated. For overharvested plants, in particular, available information is extremely limited, making it unclear whether protected areas are indeed effective at protecting species. Here, we provide the first biome-wide assessment of the effectiveness of protected areas in maintaining populations of overexploited plants. We analyzed data from 50 populations of the overexploited and threatened palm Euterpe edulis, an ecologically and economically important species of the Atlantic Forest biodiversity hotspot. By integrating these data with species distribution modelling and matrix population modelling, we were able to evaluate the most likely causes and possible consequences of differences in population density inside and outside protected areas. Forest sites located inside protected areas had, on average, almost three times higher adult density of E. edulis than sites located outside protected areas, and a corresponding higher frequency of viable populations (≥60 adults/ha). Our analyses indicate that these differences are a direct consequence of the lower frequency of palm heart harvest inside protected areas, rather than differences in climatic suitability or forest cover. The matrix model showed that the higher density and lower harvest frequency inside protected areas may significantly increase long-term persistence of E. edulis populations, reducing their extinction risk. Our findings provide new and compelling evidence that terrestrial protected areas may be crucial for long-term conservation of overexploited plants.
Chapter
Over the world, one of perspective challenges in biodiversity conservation is how to meet effective conservation of threatened species. In this frame, endangered African tree species is becoming a priority that should attract development of conservation strategies. Since biotechnology is developing rapidly as conservation strategies of biodiversity targets these last decades, it has been questioned to know (i) the current situation concerning biotechnology and endangered African tree species, (ii) the problems that prevent using of biotechnology in conservation of endangered African tree species and (iii) perspectives to help biotechnology to conserve endangered African tree species. Thus an overview on these questions showed that endangered African tree species have not taken advantages of biotechnologies strategies yet. Few biotechnologies researches based on endangered African tree species have been undertaken until now. This state of knowledge is explained by some difficulties that have been highlighted. Those difficulties concerned mostly characteristics of seeds of endangered African tree species, cost of biotechnologies strategies and bad integration of biotechnology discipline with other ones. They are preventing wide use of biotechnology strategies to conserve endangered African tree species. Considering them, some recommendations have been addressed as perspectives of conservation of endangered African tree species by biotechnology.
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Forests are human-dominated ecosystems. Many of the seemingly lightly managed or unmanaged forests are actually in use for agroforestry or for hunting and gathering. Agroforestry does reduce biodiversity, but it can also act as an effective buffer to forest clearance and conversion to other land uses, which present the greatest threat to forested ecosystems. In forests used for logging, whole-landscape management is crucial. Here, emphasis is placed on areas of intensive use interspersed with areas for conservation and catchment purposes. Management strategies for sustainable forestry are being developed, but there is a need for further interaction among foresters, ecologists, community representatives, social scientists, and economists.
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Afzelia africana is a forest species used by local inhabitants for various purposes, especially as forage to feed cattle, as medicinal plant and its wood is used to make furniture or for cooking. Its utilisation in its current form constitutes a threat to this species. However, the lack of data on this species is a hindrance towards drawing up an efficient program for its sustainable management. In order to fill in some gaps in the knowledge of A. africana tree populations, dendrometric characteristics of this species were studied within different climatic zones where it occurs in Benin. Data collected on each of them included height and diameter, and with regard to the levels of pressure, five categories were defined namely: null, weak, moderate, severe and very severe. As far as diameter is concerned every size was taken into consideration in all the climatic zones. However, average diameter and height of the A. africana individuals varied significantly according to climatic zones. Anthropogenic pressure increased while moving from the humid zone towards the drier zone. Moreover, there was a noticeable significant change in the level and quality of pressure between trees found in the different climatic zones in the sense that the lower the height of the trees, the more severe the level of pressure exerted. Such a relationship was not significant when one considers tree diameter in accordance with the climatic zones in the country.
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L'aridité climatique et la pression anthropique sont à l'origine de la régression de nombreux ligneux en zone soudanienne. Afzelia africana, Bombax costatum, Boswellia dalzielii et Pterocarpus erinaceus sont des espèces multi-usages très appréciées, mais menacées de disparition dans la région est du Burkina Faso. Un diagnostic de l'état de leur population a été fait sur la base de l'analyse des classes de diamètre et du suivi de la régénération naturelle non assistée dans des placeaux permanents. Les quatre espèces montrent une déclinaison démographique caractéri-sée par le vieillissement des peuplements et des difficultés de régénération, aussi bien au niveau de l'établissement que du développement des jeunes plants. Des formes de régénération végétative par drageons et tubercules ligneux souterrains ont été mis en évidence respectivement chez B. costatum et B. dalzielii, d'une part, et chez A. afri-cana et P. erinaceus, d'autre part. La croissance lente des jeunes plants pourrait constituer la principale difficulté endogène de régénération de ces espèces en milieu naturel semi-aride perturbé.
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A wildlife survey was carried out in Pendjari National Park of Benin in April 2000. The park covers an area of 2,660 km(2). Larger mammals were censused along 97 parallel line transects. The transects lay 1 km apart and were 15 km long on the average. The total length of strips (effort) was 1,455 km. Count data were analysed with the "Distance" programme. Twenty species were recorded during the survey, including most of the larger mammals of West Africa, in particular bovids. The most abundant species were olive baboons (Papio anubis), western buffalo (Syncerus caffer brachyceros) and kob (Kobus kob), with respective densities of 3.06, 1.0 and 0.98 animals/km(2). The total biomass of larger mammals was 0.63 t/km(2) (elephants: Loxodonta africana excluded) and 1.12 t/km(2) (elephants included). The carrying capacity for herbivores was estimated at 2.8 t/km(2). Except for buffalo, roan antelope (Hippotragus equinus) and hartebeest (Alcelaphus buselaphus major), both species richness and abundance were lower than in a previous survey ten years earlier, and species such as topi (Damaliscus lunatus korrigum) and leopard (Panthera pardus) were no longer detected. The results signify the need to revise and improve current wildlife conservation and management strategies to assure long-term protection of larger mammals in Pendjari National Park.
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The structure, function, and ecosystem services of tropical forest depend on its species richness, diversity, dominance, and the patterns of changes in the assemblages of tree populations over time. Long-term data from permanent vegetation plots have yielded a wealth of data on the species diversity and dynamics of tree populations, but such studies have only rarely been undertaken in tropical forest landscapes that support large human populations. Thus, anthropogenic drivers and their impacts on species diversity and community structure of tropical forests are not well understood. Here we present data on species diversity, community composition, and regeneration status of tropical forests in a human-dominated landscape in the Western Ghats of southern India. Enumeration of 40 plots (50m×20m) results a total of 106 species of trees, 76 species of saplings and 79 species of seedlings. Detrended Correspondence Analysis ordination of the tree populations yielded five dominant groups, along disturbance and altitudinal gradients on the first and second axes respectively. Abundant species of the area such as Albizia amara, Nothopegia racemosa and Pleiospermum alatum had relatively few individuals in recruiting size classes. Our data indicate probable replacement of rare, localized, and old-growth ‘specialists’ by disturbance-adapted generalists, if the degradation is continuing at the present scale.
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Tree species richness, tree density, basal area, population structure and distribution pattern were investigated in undisturbed, mildly disturbed, moderately disturbed and highly disturbed stands of tropical wet evergreen forests of Arunachal Pradesh. The forest stands were selected based on the disturbance index (the basal area of the cut trees measured at ground level expressed as a fraction of the total basal area of all trees including felled ones): (i) undisturbed stand (0% disturbance index), (ii) mildly disturbed (20% disturbance index), (iii) moderately disturbed (40% disturbance index), and (iv) highly disturbed stand (70% disturbance index). Tree species richness varied along the disturbance gradient in different stands. The mildly disturbed stand showed the highest species richness (54 of 51 genera). Species richness was lowest (16 of 16 genera) in the highly disturbed stand. In the undisturbed stand, 47 species of 42 genera were recorded while in the moderately disturbed stand 42 species of 36 genera were found. The Shannon–Wiener diversity index for tree species ranged from 0.7 to 2.02 in all the stands. The highest tree diversity was recorded in the undisturbed stand and the lowest in the highly disturbed stand. The stands differed with respect to the tree species composition at the family and generic level. Fagaceae, Dipterocarpaceae and Clusiaceae dominated over other families and contributed 53% in the undisturbed, 51% in the mildly disturbed, 42% in the moderately disturbed and 49% in the highly disturbed forest stands to the total density of the respective stand. Stand density was highest (5452 stems ha-1) in the undisturbed stand, followed by the mildly disturbed stand (5014), intermediate (3656) in the moderately disturbed stand and lowest (338) in the highly disturbed stand. Dominance, calculated as the importance value index of different species, varied greatly across the stands. The highest stand density and species richness were represented in the medium girth class (51–110 cm) in all the stands. In the undisturbed stand, the highest density was found in the 111–140 cm girth class, while in the mildly disturbed stand the 51–80 cm girth range recorded the highest density. About 55, 68 and 52% species were found to be regenerating in the undisturbed, mildly disturbed and moderately disturbed stands, respectively. No regeneration was recorded in the highly disturbed stand. Variation in species richness, distribution pattern and regeneration potential is related to human interference and the need for forest conservation is emphasized.
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An tree-inventory of Isoberlinia natural mixed stands was carried out in the tree-savannas and woodlands of the Wari–Maro Forest Reserve (Republic of Benin) to serve as basis to improve existing management strategies. Measurements were done in 96 rectangular plots of 30 × 50 m with a cumulative area of 14.4 ha. The two vegetation types were mainly distinguished by the overall tree-density (225.2 stems/ha in tree-savannah against 202.8 stems/ha in woodland), the overall mean height of the stands (13.1 and 14.6 m, respectively) and the mean height of Isoberlinia trees (14.1 and 16.8 m respectively). The other parameters (mean diameter, basal area, basal area contribution of Isoberlinia trees, bark thickness, tree-density of Isoberlinia trees as well as the Shannon diversity index and Pielou evenness index) had essentially the same values for the two vegetation types. The stem diameter structure of Isoberlinia stands in the two vegetation types had an "inverse-J" shape for the whole stand and the "I" shape for Isoberlinia trees. The stem diameter of Isoberlinia decreased on average 1.9 cm/m tree-height. Isoberlinia seedlings were more abundant below the canopy of mature trees than further away. The main dispersal mode of the species consisted of dropping the seeds from pods under the mother tree, and suckering which resulted in the observed aggregated distribution of the trees. These results were used to propose management strategies for the two vegetation types.
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Forest ecologists often evaluate how well the species composition of saplings in the understory matches that of the canopy: absence of juveniles suggests that a tree species is suffering population decline. Here we offer a theoretical and empirical test of this assertion using data from a 50-ha census plot in Panama. Theory indicates that higher rates of population change, lambda, lead to more steeply declining size distributions (more juveniles relative to adults). But other parameters also affect the size distribution: lower growth rate of juveniles and lower survival at any size produce more steeply declining size distributions as well. Empirical evaluation of 216 tree populations showed that juvenile growth was the strongest predictor of size distribution, in the direction predicted by theory. Size distribution did correlate with population growth, but weakly and only in understory species, not canopy species. Size distribution did not correlate with the growth rate of larger individuals nor with survival. Results suggest that static in formation on the size distribution is not a good predictor of future population trends, while demographic information is. Fast-growing species will have fewer juveniles in the understory than slow growing species, even when population growth is equal.
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We assessed the impacts of anthropogenic threats on 93 protected areas in 22 tropical countries to test the hypothesis that parks are an effective means to protect tropical biodiversity. We found that the majority of parks are successful at stopping land clearing, and to a lesser degree effective at mitigating logging, hunting, fire, and grazing. Park effectiveness correlates with basic management activities such as enforcement, boundary demarcation, and direct compensation to local communities, suggesting that even modest increases in funding would directly increase the ability of parks to protect tropical biodiversity.
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Five caesalpinioid legumes, Afzelia africana, Afzelia bella, Anthonotha macrophylla, Cryptosepalum tetraphylum and Paramacrolobium coeruleum, and one Euphorbiaceae species, Uapaca somon, with a considerable range in seed sizes, exhibited different responses to inoculation by four species of ectomycorrhizal (ECM) fungi, Scleroderma dictyosporum, S. verrucosum, Pisolithus sp. and one thelephoroid sp. in greenhouse conditions. Thelephoroid sp. efficiently colonized seedlings of all of the five caesalpinioid legumes except U. somon, but provided no more growth benefit than the other fungi. Thelephoroid sp. and S. dictyosporum colonized seedlings of U. somon poorly, but stimulated plant growth more than the other fungi. The relative mycorrhizal dependency (RMD) values of the caesalpinioid legumes were never higher than 50%, whilst U. somon had RMD values ranging from 84.6 to 88.6%, irrespective of the fungal species. The RMD values were negatively related to seed mass for all plant species. Potassium concentrations in leaves were more closely related than phosphorus to the stimulation of seedling biomass production by the ECM fungi. Our data support the hypothesis that African caesalpinioid legumes and euphorbe tree species with smaller seeds show higher RMD values than those with the larger seeds.
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The viability of seeds and the survival of seedlings in natural conditions are key factors for sexual regeneration of woody species. The constraints of sexual regeneration of Afzelia africana were studied in laboratory, nursery and under natural conditions. The experiments consisted of germination tests in laboratory, monitoring of the seedling growth in rhizotron and assessment of the factors of mortality of seedlings under natural conditions. When seeds water content is about 8% (on the fresh weight basis), they can be stored in ambient conditions for at least 33 months after collection, without a significant reduction of the germination rate. The seedlings have a deep-root system with precocious lateral ramifications. However, the seedlings are still very sensitive to fire, browsing and drought. To grow well, the seedlings of A. africana need to be protected against these constraints.
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A study was carried out in the Lama forest reserve of Benin to characterize the habitat of Afzelia africana Sm., an endangered multipurpose tree species (found in African humid, dry forests and woodlands), in order to define a sustainable management strategy for its conservation. An estimation of species density was done on 100 square plots of 1 ha each, while tree height and dbh of all the species were measured on subplots of 50 m � 30 m within the 1 ha plots. The regenerations of A. africana (dbh < 10 cm) were counted in the diagonal quadrats of the principal plots. Presence–absence data of the species was subjected to multidimensional scaling and results showed four vegetation communities including: young fallow, old fallow, typical dense forest and degraded dense forest. Significant differences were noted between the four communities with respect to dendrometric parameters of the species. High values of these parameters were noted for the species in typical dense forest (5.2 stems/ha, 66.7 cm, 17.9 m, 7.9 m2/ha and 38.8% for the tree-density, the mean diameter, the mean height, basal area and basal area contribution of the species, respectively) whereas the lowest values were obtained for the old preforest fallow as far as the mean diameter (59.7 cm), the mean height (15.7 m) and the basal area contribution (27.7%) of the species were concerned. In general, the basal area of A. africana in the over vegetation types was less than 3 m2/ha. No A. africana tree was found in the young preforest fallow while more than 80% of A. africana trees were found in the typical dense forest community. Stem diameter and height structures of the species in all the four communities showed a left dissymmetric Gaussian shape and were well adjusted to Weibull distribution.
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This study reports results from the first explicit test of the ectomycorrhizal hypothesis for tropical monodominance in the Ituri Forest of the Democratic Republic of Congo (formerly Zaire), where the canopy tree Gilbertiodendron dewevrei forms large, monospecific stands. To test the hypothesis that ectomycorrhizae are important to the success of dominant species, we surveyed the mycorrhizal status of dominant species, as well as other common, but not dominant, species in the forest. The survey reveals that two dominant species, Gilbertiodendron dewevrei and Julbernardia seretii, form ectomycorrhizae and vesicular-arbuscular mycorrhizae, while Cynometra alexandri, another dominant, forms only vesicular-arbuscular mycorrhizae. These results, along with those of other species in this and other forests, are discussed within the context of the ectomycorrhizal hypothesis for tropical mondominance. This study demonstrates that the relationship between EM and tropical monodominance is more complex than has been previously recognized.