Papers by Sylvanus Mensah
Scientific Reports, Dec 13, 2023
Trees-structure and Function, Feb 9, 2022
Key Message : Strychnos spinosa growth was less responsive than its fruit production, to tree siz... more Key Message : Strychnos spinosa growth was less responsive than its fruit production, to tree size, protection status and climate; its fruit production increased with tree size, and more so on protected sites.
Acta Botanica Gallica, Jan 2, 2015
A study was carried out in two phytodistricts (Ouémé-valley and Plateau) to assess the population... more A study was carried out in two phytodistricts (Ouémé-valley and Plateau) to assess the population structure of two bamboo species (Oxytenanthera abyssinica (A. Rich.) Munro and Bambusa vulgaris Schrad. ex J.C. Wendl. in two topographical units: plateau and wetlands. In each phytodistrict bamboo stands were randomly selected in each topographical unit for inventory using a 0.25-ha square plot. Structural parameters of bamboos were computed and compared using a Wilcoxon rank test. Spatial distribution of the two bamboos was also assessed using the method of neighbourhood density in relation to a focal point. The observed culm diameter distribution was established for each stand and adjusted to the two-parameter Weibull distribution. Oxytenanthera abyssinica showed the highest culm and clump density values in both wetlands and plateau whereas B. vulgaris showed greater values of mean diameter and dominant height whatever the habitat. Diameter structures of bamboo stands showed a right asymmetric distribution and bamboo spatial distribution was highly aggregative, especially in wetlands. No significant difference in mean relative neighbourhood density between species was noted. However, a significant difference was observed between wetlands and plateau (p < 0.001) indicating strong influence of the topographical units on the relative neighbourhood density of bamboo species. All of these findings are determinants in designing suitable management strategies for bamboo populations in Benin, particularly with the increasing demand to build fish-traps and shelter in the traditional fishing systems "Acadja".
Environment, Development and Sustainability, Mar 10, 2020
Afzelia africana Sm. is a highly valued multipurpose and overexploited tree species in Africa. Et... more Afzelia africana Sm. is a highly valued multipurpose and overexploited tree species in Africa. Ethnobotany of A. africana can guide its sustainable usage, yet there is limited information on such aspect for the species in Uganda. Here, we assessed use values of A. africana and users' traditional knowledge, and how they relate to plant parts and socioeconomic factors including ethnicity, gender, education, age, marital status, profession, household size, income, land size and livestock ownership. Two hundred face-to-face semi-structured interviews were conducted. Use values were assessed based on plant part value (PPV) and use value per use category (UV k), while users' traditional knowledge was compared using overall use value (OUV) and reported use value (RUV). All plant parts were used, with stem (PPV = 41.4%), seeds (19.6%) and leaves (19.3%) being the most important. Nine plant use categories were enumerated, with most dominant being material (UV k = 0.63), followed by social (0.49) and fuel wood (0.41). Bark and root were mostly used for medicinal purpose, and branch and stem for fuelwood and material, respectively. Men and youngsters had higher OUV than females and older people, respectively. In particular, men frequently mentioned the use in agriculture, for fuelwood, environment and medicine, while women reported social use. Although socio-cultural group did not influence significantly OUV and RUV, multivariate analyses revealed differentiation in use category according to socio-cultural group. Land size also predisposed informants to report more uses for the species. Taking these significant socioeconomic factors into account in participative forest management will facilitate A. africana sustainable use.
Forests, Feb 28, 2021
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Tropical Conservation Science, 2018
Exploring taxonomic, functional, and structural diversity can provide additional insights into ou... more Exploring taxonomic, functional, and structural diversity can provide additional insights into our understanding of diversity responses to environment. Using altitude, slope, and relative radiation index as well as floristic and functional data from a South Africa Afromontane forest, we examined how taxonomic, structural, and functional diversity varied with local environmental variation. Taxonomic and structural diversity were quantified through species richness-and diameter class-based Shannon index and evenness, respectively. Skewness and coefficient of variation of diameter distribution were additionally computed for structural diversity. As for functional diversity, we used functional richness, evenness, divergence, and dispersion based on functional traits. Data were analyzed using multimodel inference and subset regression. We found little evidence of environmental effects on local-scale taxonomic diversity patterns. In contrast, structural and functional diversity metrics varied significantly along environmental gradients. Accordingly, diameter class-based Shannon evenness declined with increasing slope while skewness and coefficient of variation of diameter distribution increased with increasing slope. Functional evenness and divergence decreased with increasing altitude and radiation, respectively, while functional richness and dispersion increased with increasing slope. The results showed that taxonomic diversity patterns were less responsive to local-scale topographical variation than structural and functional diversity. Lower functional diversity on lower slope sites suggests weak environmental filtering effect promoting competitive exclusion and dominance of species with acquisitive traits. On higher slope sites, environmental filtering associated with slope gradient seems to favor coexistence of species with conservative traits and adapted to harsh conditions.
Southern forests, Feb 21, 2017
The study aimed to investigate the relative significance of effects of climatic variability and h... more 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.
Ethnobotany Research and Applications, Mar 19, 2015
Global Change Biology, Jun 28, 2022
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Scientific Reports
Climatic and edaphic effects are increasingly being discussed in the context of biodiversity-ecos... more Climatic and edaphic effects are increasingly being discussed in the context of biodiversity-ecosystem functioning. Here we use data from West African semi-arid tree savannas and contrasting climatic conditions (lower vs. higher mean annual precipitation-MAP and mean annual temperature-MAT) to (1) determine how climate modulates the effects of species richness on aboveground carbon (AGC); (2) explore how species richness and AGC relate with soil variables in these contrasting climatic conditions; and (3) assess how climate and soil influence directly, and/or indirectly AGC through species richness and stand structural attributes such as tree density and size variation. We find that greater species richness is generally associated with higher AGC, but more strongly in areas with higher MAP, which also have greater stem density. There is a climate-related influence of soils on AGC, which decreases from lower to higher MAP conditions. Variance partitioning analyses and structural equat...
Journal of Arid Environments
Global Ecology and Conservation
Land, Feb 15, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Transforming tertiary agricultural education in Africa
Abstract This chapter explores the role of Africa's universities in facilitating the prolifer... more Abstract This chapter explores the role of Africa's universities in facilitating the proliferation and success of entrepreneurship as a development strategy. In particular, the discussion is intended to articulate how Africa's universities can support the generation of much-needed employment opportunities by providing education and training in entrepreneurship. The chapter first examines the prevailing entrepreneurial ecosystem, (i) by providing context from the available literature on the demographic challenge Africa faces in light of its rapidly-growing youth population and associated high unemployment rates and (ii) by exploring the means by which entrepreneurship can be fostered. Thereafter, the chapter focuses on working models of education and training in entrepreneurship, including intentions and adaptations, real-world successes, lessons learned and potential future directions.
Land
Understanding the evolution of land use/land cover change (LULCC) and how it shapes current and f... more Understanding the evolution of land use/land cover change (LULCC) and how it shapes current and future ecosystem services (ES) supply potential remains critical in sustainable natural resource management. Community perception of historic LULCC was reconciled with previous study via remote sensing/geographical information systems using recall data in the Budongo–Bugoma landscape in Uganda. Then, a CA-Markovian prediction model of a LULC situation in 2040 under business as usual (BAU) and forest restoration scenarios was constructed. Additionally, we assessed the perceived proximate and underlying drivers of LULCC, and how LULCC shapes ecosystem services potential using household surveys. The perceived LULCC trend for the past three decades (1990–2020) corresponded with previous studies showing grassland, bushland, tropical high forest, and wetland cover declined greatly, while subsistence farmland, commercial farmland, and built-up areas had a great increment. The predicted LULC unde...
Land
Grazing management strategies tend to have different effects on rangeland plant production. Chang... more Grazing management strategies tend to have different effects on rangeland plant production. Changes in grazing management can, therefore, affect the carbon stock potential of rangelands. Despite rangeland ecosystems being important global sinks for carbon, we know relatively little about the effect of traditional grazing management practices on their potential to store carbon. In this study, we evaluated the carbon stock and change rate of rangelands using three traditional grazing management practices in the semiarid pastoral ecosystem of eastern Ethiopia. By comparing data on vegetation and soil carbon stocks, we found that there was a strong significant difference (p < 0.001) between these different management practices. In particular, the establishment of enclosures was associated with an annual increase in carbon stocks of soil (3%) and woody (11.9%) and herbaceous (57.6%) biomass, when compared to communal open lands. Both enclosure and browsing management practices were fo...
Science of The Total Environment, 2021
Grazing exclosures have been promoted as an effective and low-cost land management strategy to re... more Grazing exclosures have been promoted as an effective and low-cost land management strategy to recover vegetation and associated functions in degraded landscapes in the tropics. While grazing exclosures can be important reservoirs of biodiversity and carbon, their potential in playing a dual role of conservation of biodiversity and mitigation of climate change effects is not yet established. To address this gap, we assessed the effect of diversity on aboveground carbon (AGC) and the relative importance of the driving biotic (functional diversity, functional composition and structural diversity) and abiotic (climate, topography and soil) mechanisms. We used a dataset from 133 inventory plots across three altitudinal zones, i.e., highland, midland and lowland, in northern Ethiopia, which allowed local- (within altitudinal zone) and broad- (across altitudinal zones) environmental scale analysis of diversity-AGC relationships. We found that species richness-AGC relationship shifted from neutral in highlands to positive in mid- and lowlands as well as across the altitudinal zones. Structural diversity was consistently the strongest mediator of the positive effects of species richness on AGC within and across altitudinal zones, whereas functional composition linked species richness to AGC at the broad environmental scale only. Abiotic factors had direct and indirect effects via biotic factors on AGC, but their relative importance varied with altitudinal zones. Our results indicate that the effect of species diversity on AGC was altitude-dependent and operated more strongly through structural diversity (representing niche complementarity effect) than functional composition (representing selection effect). Our study suggests that maintaining high structural diversity and managing functionally important species while promoting favourable climatic and soil conditions can enhance carbon storage in grazing exclosures.
Acta Botanica Gallica, 2015
A study was carried out in two phytodistricts (Ouémé-valley and Plateau) to assess the population... more A study was carried out in two phytodistricts (Ouémé-valley and Plateau) to assess the population structure of two bamboo species (Oxytenanthera abyssinica (A. Rich.) Munro and Bambusa vulgaris Schrad. ex J.C. Wendl. in two topographical units: plateau and wetlands. In each phytodistrict, bamboo stands were randomly selected in each topographical unit for inventory using a 0.25-ha square plot. Structural parameters of bamboos were computed and compared using a Wilcoxon rank test. Spatial distribution of the two bamboos was also assessed using the method of neighbourhood density in relation to a focal point. The observed culm diameter distribution was established for each stand and adjusted to the two-parameter Weibull distribution. Oxytenanthera abyssinica showed the highest culm and clump density values in both wetlands and plateau whereas B. vulgaris showed greater values of mean diameter and dominant height whatever the habitat. Diameter structures of bamboo stands showed a right asymmetric distribution and bamboo spatial distribution was highly aggregative, especially in wetlands. No significant difference in mean relative neighbourhood density between species was noted. However, a significant difference was observed between wetlands and plateau (p < 0.001) indicating strong influence of the topographical units on the relative neighbourhood density of bamboo species. All of these findings are determinants in designing suitable management strategies for bamboo populations in Benin, particularly with the increasing demand to build fish-traps and shelter in the traditional fishing systems "Acadja".
Wetlands Ecology and Management, 2021
Understanding the impacts of wood harvesting intensity on the diversity and structure of ecosyste... more Understanding the impacts of wood harvesting intensity on the diversity and structure of ecosystems such as mangroves is essential for defining actions for their sustainable management. We compared tree taxonomic diversity, structural diversity and dominance patterns, density, growth characteristics, size class distribution-SCD and stand stability in West African mangroves subject to low vs. high wood harvesting intensity. Data on tree species identity, total height, diameter (dbh), and conditions (logged, topped or pruned) were collected from ten mangrove sites per harvesting intensity. We found seven species of which two true mangroves species (Rhizophora racemosa and Avicennia germinans) that were dominant across all sites. As expected, there were significantly 3–4, 3–7, and 2–4 times more logged, topped and pruned trees respectively in high-harvesting sites than in low-harvesting sites. Taxonomic diversity was less affected than structural diversity (dbh and height-based diversity metrics). Tree density was significantly 1.3–5 times higher in low-harvesting sites than in high-harvesting sites for the whole stand and each of the dominant species. Total regeneration density was also low in high-harvesting sites. However, regeneration density was relatively higher in high-harvesting sites for R. racemosa contrary to A. germinans. Trees were also significantly smaller and shorter in high-harvesting sites. The SCD indicated inverse J-shaped distributions, irrespective of the harvesting intensity and showed that tree harvesting targeted mostly dbh classes 10–30 cm. The density of this class was 2.6–6.2 times lower in high-harvesting sites. This study provides important information on impacts of wood harvesting in a marginally studied mangroves’ area.
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Papers by Sylvanus Mensah