Bois et forêts des tropiques

Abstracts & articles: n° 332
(2nd quarter 2017)

All abstracts
(In French, English and Spanish)

New issue

Issue 332



A. Adugna, A. Abegaz, A. Legass, D. L. Antille

Africa has seen significant changes in land cover at different spatial scales. Changes in Land Use and Land Cover (LULC) include deforestation and subsequent use of the land for arable cropping, conversion to grassland or urbanization. The work reported in this article was conducted to examine land cover transitions in north-eastern Wollega (Ethiopia) between 2005 and 2015. The analysis focused on land cover transitions that occurred systematically or randomly, and identified the main drivers for these changes. Landsat data from 2005 and 2015 were examined to better understand the various dimensions of land cover transitions, namely: swaps, losses, gains, persistency and vulnerability. Results showed that shrubland exhibited the largest gain (22%), with a 63% gainto- loss ratio, a 47% gain-to-persistence ratio and a positive net change-to-persistence ratio of 46%. Cropland showed the largest loss (19%) while grassland was the most stable type of land cover despite some fluctuation (˜10%) observed during the 10-year period. The land cover transition was dominated by systematic processes, with few random processes of change. Systematic land cover transitions such as agricultural abandonment and vegetation re-growth were attributed to regular or common processes of change. This study suggests that the implementation of practices conducive to sustainable intensification of existing agricultural land, supported by policies that promote increased diversification of Ethiopian agriculture, would mitigate pressure on forests by avoiding their future conversion to cropland.

Keywords: cropland abandonment, deforestation, forest re-growth, soil security, sustainable intensification, Ethiopia.

the article


A. B. Fandohan, F. J. Chadare, G. N. Gouwakinnou, C. F. Tovissode, A. Bonou, S. F. B. Djonlonkou, L. F. H. Houndelo, C. L. B. Sinsin, A. E. Assogbadjo

Synsepalum dulcificum (Schumach. & Thonn. Daniell) is a West African shrub which is listed as vulnerable by the IUCN. Its importance for local people in Benin has been little documented. This study takes up this issue and was carried out to assess local knowledge, use value and the economic importance of the species for local people. Ethnobotanical and economic surveys were conducted with 606 respondents from 13 socio-cultural groups in southern Benin. Ethnobotanical and economic indices (citation frequency, ethnobotanical use value and mean income generated) were computed and their significance tested using generalized linear models and Kruskal and Wallis tests. The results showed that S. dulcificum was well known to local people in southern Benin (100% of respondents), who mostly grew it in their home gardens. All parts of the plant were used, mostly for medicinal, food and spiritual purposes. Knowledge of the shrub and its use value varied among the socio-cultural groups, decreasing along a gradient from south- east to south-west. Knowledge and use value were also dependent on gender, age and activity, and concentrated among men, adults, elderly people and traditional healers. Economic data showed a short marketing chain. The low average income generated by selling the fruit (about US$ 28 yearly per seller) reveals the low economic value of the species, which is a declining subsistence resource. Optimising the conservation and uses of the species would require (i) nutritional, phyto-chemical, pharmaceutical, phenological, morphological and genetic investigations, (ii) the development of sylvicultural method, (iii) inclusion of the species in formal conservation policies and (iv) development of a value chain by establishing a structured production channel.

Keywords: Synsepalum dulcificum, miracle fruit, ethnobotanical survey, socio-cultural group, phytotherapy, use value, Republic of Benin.

the article


C. Fargeot, N. Drouet-Hoguet, S. Le Bel

In the Congo Forest Basin, hunting provides a major source of protein for rural household consumption. In the context of increasing urbanisation, an understanding of bushmeat consumption in urban settings is needed to both address food security issues and design biodiversity conservation strategies. This paper provides insights into bushmeat consumption patterns in Bangui, the capital of the Central African Republic, through an analysis of household expenditures and market prices. A survey of approximately 4,000 households combined with 3 years (2005-2008) of market price monitoring was used to estimate the consumption of bushmeat and alternative proteins. The results showed the presence of a diverse range of animal proteins on the Bangui market, including meat from domestic and wild animals. The taxonomic composition of the bushmeat mainly included common, sedentary wildlife species that are highly resilient to hunting pressure, while protected species were rarely observed. The household consumption survey showed that 54% of daily meals contained beef, 35% contained fish and 19% contained bushmeat. Fish and bushmeat consumption decreased in the rainy season, and caterpillar consumption increased. Smoked proteins (bushmeat, fish), were cheaper than all fresh meat except for caterpillars. The consumption of proteins and bushmeat increased with wealth; fresh proteins were consumed more by wealthy consumers, while smoked bushmeat was consumed by the poorest. Total consumption of protein and bushmeat was highest in rich households, but the relative proportion of bushmeat in the total protein intake was highest for poor households. Overall, the results confirm the importance of bushmeat in the diet of urban consumers, especially in poor households. However, the patterns of consumption suggest that bushmeat is less popular than alternatives, which may potentially limit an increase in bushmeat consumption, particularly if cheaper, alternative meat can be made available.

Keywords: bushmeat trade, bushmeat consumption, food security, Bangui, Central African Republic.

the article


A. J. Gbètoho, A. K. N. Aoudji, L. Roxburgh, J. C. Ganglo

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.

Keywords: Lonchocarpus sericeus, Anogeissus leiocarpa, species distribution modelling, maximum entropy, generalized linear model, favourable area, ecology.

the article


A. Masson, O. Monteuuis

The forest tree species Hevea brasiliensis is extensively planted in the humid tropics to meet the increasing demand for natural rubber. Huge quantities of planting stock are therefore needed. The seed option remains the easiest and cheapest way to establish plantations of rubber trees but those show a great variability for vigor and also for latex yield. The rationale of producing clones for overcoming this variability was already obvious in the early 1910’s but due to the difficulties encountered at that time for rooting shoots, grafting was used as an alternative cloning method. The striking increase in yield noticed from the graft-derived clonal plantations warranted their large scale development. Eventually, the budded clones by virtue of their much higher and uniform productivity supplanted the seedlings in most industrial plantations. However, grafting is also associated with drawbacks and for decades efforts aiming at mass producing selected rubber tree clones on their own roots by rooted cuttings have been pursued. However, this approach was progressively abandoned due to disappointing rooting results and, from the 70’s onwards, priority has been given to in vitro methods which were booming during this period. But despite 40 years of heavy investments, industrial H. brasiliensis clones could still not be mass micropropagated in vitro efficiently enough to meet the requirements of large scale production. The situation may change radically soon, however, due to the development of new nursery techniques adapted to the mass clonal production by rooted cuttings of any H. brasiliensis selected genotype. Efforts to improve the techniques as well as the establishment of new field trials are underway in order to determine if self-rooted rubber tree clones are more productive than grafted ones. This old issue is becoming of overriding importance considering the increasing pressure on land availability reducing thereby the prospects for expanding rubber tree plantations.

Keywords: clonal propagation, cuttings, grafts, Hevea brasiliensis, planting stock, roots, seeds, tissue culture.

the article


I. Zerbo, K. Hahn, M. Bernhardt-Römermann, O. Ouédraogo, A. Thiombiano

According to environmental predictions, West Africa is becoming vulnerable to the adverse effects of climate change and land use disturbance. Herbaceous vegetation is the most sensitive to these effects. To assess the potential of species to cope with these changes, this study investigated the dispersal potential of different herbaceous species. Data on herbaceous plant composition and environmental parameters were collected along climate, land use and habitat gradients in West African savannah areas, as well as the diaspores of all herbaceous species encountered. Their traits were described in order to document the diversity of diaspore categories in herbaceous savannah vegetation. Based on an occurrence diagram, variations in dissemination patterns within families were identified. The dispersal potential of each species was determined on the basis of their patterns of dispersal. A hierarchical classification method was used to establish a dispersal typology, and principal component analysis was applied to identify the environmental conditions that account for their patterns of dispersal. The results show that the diaspores of herbaceous species can be classified according to fruit type, diaspore type, presence of heterodiaspory, exposure of diaspores, number of seeds per diaspore, diaspore morphology, shape of diaspores and pattern of dispersal. Poaceae, the most abundant family in savannah areas, have six patterns of dispersal. Most species have more than one pattern, and species with high dispersal potential (85.43%) dominate the herbaceous vegetation. Four groups of herbaceous species were identified according to their dispersal patterns. Potentially epizoochorous and anemochorous species (39.25% of the flora) were more related to village areas independently of climatic conditions and habitat types. Potentially endozoochorous and dysozoochorous species (31.06% of the flora) were more related to fresh and dry habitats in protected areas of the North and South Sudanian zones. Potentially hydrochorous species (12.63% of the flora) were related to wet habitats but were more prominent in the Sahel, and potentially autochorous species (17.06% of the flora) were more related to bowé habitats in the southern Sudanian zone. Our study showed that all herbaceous species have good dispersal potential, which might enable them to persist in West African savannahs despite the severe climatic changes predicted.

Keywords: diaspore traits, dispersal group, disturbance, diversity, Climate change, West Africa.

the article


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