Bois et forêts des tropiques

Abstracts & articles: n° 333
(3rd quarter 2017)


All abstracts
(In French, English and Spanish)

New issue

Issue 333


 

INVENTORY AND MULTICRITERIA APPROACH TO IDENTIFY PRIORITY COMMERCIAL TIMBER SPECIES FOR CONSERVATION IN BENIN

J. D. T. Akpona, A. E. Assogbadjo, A. B. Fandohan, R. Glèlè Kakaï

A variety of timber species, some of which are under threat, are targets for both legal and illegal logging. Priority timber species for long-term conservation therefore need to be defined. This study produced an inventory of timber species logged in Benin and defined priority Timber Species (TS) requiring urgent conservation and restoration measures. Data to establish an exhaustive list of TS in Benin were collected through a review of the literature and interviews with different stakeholders. Ten criteria were applied to four different prioritization methods. The top 15 species obtained with each of these methods were identified and the top 10 were shortlisted. A total of 24 plant species belonging to nine families were identified. Those most represented were: Fabaceae (25%), Malvaceae (20.83%), Meliaceae (16.67%), Combretaceae (8.33%), Moraceae (8.33%), Verbenaceae (8.33%), Ebenaceae (4.17%), Rutaceae (4.17%) and Myrtaceae (4.17%). The ten top species deserve urgent conservation and restoration measures.

Keywords: timber species, conservation, prioritization methods, West Africa.


Download
the article

USES OF BOMBAX COSTATUM (MALVACEAE) IN LANDS ADJACENT TO THE PENDJARI BIOSPHERE RESERVE IN THE REPUBLIC OF BENIN

G. A. Assogba, A. B. Fandohan, V. K. Salako, A. E. Assogbadjo

Bombax costatum (the red kapok tree) is native to Africa’s Sudanian zone. It has rarely been studied and is most certainly under-used. Our study assessed traditional knowledge on uses of B. costatum and its cultural importance in different socio-cultural groups and according to age categories and gender around the Pendjari Biosphere Reserve in the Republic of Benin. We conducted 118 individual semi-structured interviews to make the assessment. Ethnobotanical indices such relative frequency of citation, reported use value and the cultural importance index were applied in order to assess traditional knowledge and the cultural importance of B. costatum. A total of 46 uses were identified and grouped into 8 categories. The most frequently cited and most culturally important uses of the species were for food and medicinal purposes. The calyx was the plant part most frequently used, especially for food, while medicinal uses involved several plant parts including the calyx, leaf, bark, seed and root. The calyx is also sold on local markets. Knowledge on the uses of B. costatum varied significantly between socio-cultural groups but not according to gender or age categories. Respondents from the Berba and Gourmantché socio-cultural groups were more knowledgeable than the Waama, Natimba and Peulh groups, and also used B. costatum for food most frequently. Promoting the food uses of this species could be considered as a starting point for broadening its use as a resource. However, future studies would need to explore other areas where the species occurs and focus additionally on its nutritional value and potential contribution to household income, as well as on efficient propagation methods to ensure that the species can be used sustainably.

Keywords: Bombax costatum, traditional knowledge, ethnobotanical use value, Pendjari Biosphere Reserve, Republic of Benin.


Download
the article

MORPHO-PHYSIOLOGICAL QUALITY OF QUERCUS SUBER L. CORK OAK SEEDLINGS PRODUCED IN MOROCCAN FOREST NURSERIES

M. Bouderrah, A. Zine El Abidine, A. Bounakhla, M. S. Lamhamedi, A. Zouahri, F. Mounir

Natural regeneration in Moroccan cork oak forests (Quercus suber L.) is very rare as a result of both human and environmental factors. Plantations using nursery seedlings have had little success in achieving the objectives of reforestation programs. Plantation failures are due to unfavourable environmental variables, inappropriate preparation techniques for reforestation sites and the poor morpho- physiological quality of seedlings produced in nurseries. This study aimed to assess the technical management sequences and the quality of the cork oak seedlings produced in four forestry nurseries according to Moroccan and Spanish standards. The technical sequences specified in the Moroccan standards (SPC) for the production of cork oak seedlings are not very elaborate and sometimes not properly followed. Methods of fertilization are not defined and are applied with no analysis of the specific needs of seedlings. The pH of the culture medium in which the seedlings are grown is higher than 7. Most of the cork oak seedlings produced in the four nurseries do not comply with at least one of the criteria set by established standards. Sub-standard production is generally above 10%. The proportion of seedlings with root defects varies from 10 to 48%. 10 to 36.5% of the root systems are pot-bound. To improve reforestation success rates, the production techniques for cork oak seedlings and the cultivation standards set out in the current Moroccan SPC need to be revised in order to produce seedlings of better quality.

Keywords: Quercus suber, cork oak, nursery, technical procedures, quality standards, Morocco.


Download
the article

EFFECTS OF MAJOR WOODY SPECIES OF THE SENEGALESE GREAT GREEN WALL ON N MINERALIZATION AND MICROBIAL BIOMASS IN SOILS

M. D. Diallo, T. Goalbaye, M. Mahamat- Saleh, P. S. Sarr, D. Masse, S. A. Wood, L. Diop, R. P. Dick, A. Diop, A. Guisse

An experiment was conducted over nine months in a field system in northern Senegal in order to determine the effects on soil nitrogen (N) cycling and the microbial biomass-C properties of five plant species proposed for the Senegalese Great Green Wall (GGW): Acacia senegal (L.) Willd., Acacia tortilis var. raddiana (Savi) Brenan, Balanites aegyptiaca (L.) Del., Boscia senegalensis (Pers.) Lam. ex Poir., and Sclerocarya birrea (A. Rich.) Hochst. Soil samples were collected to a depth of 0-10 cm, outside (control) and beneath tree canopies. Microbial biomass, inorganic N content and net mineralization of organic N were determined for the soil samples collected under trees, and compared to soils collected outside tree canopies. The results showed that concentrations of inorganic N and soil microbial biomass-C were generally higher under canopy cover and differed according to species. In May 2014 (end of the dry season), microbial biomass-C was higher under A. senegal (31.8 mg C/ kg soil) and lower under B. senegalensis and in the control sample from outside the canopy (17 mg C/kg soil). A higher microbial biomass-C content was found under A. senegal (49 mg C/kg soil) and B. aegyptiaca (53.7 mg C/kg soil) in October 2014 (end of the rainy season) and in January 2015 (middle of the dry season). In May 2014, the concentration of ammonium was significantly higher under B. senegalensis (11.17 µg/g soil), while the control sample (outside the canopy) had the lowest concentration (4.93 µg/g soil). For nitrates, there was no significant difference between canopy species (P = 0.05). These results can provide guidance for selecting tree species for the GGW according to their functioning and their effects on soil quality.

Keywords: nitrogen dynamics, nitrification, Great Green Wall, Sahelian agro-ecosystem, Ferlo, Senegal.


Download
the article

POPULATION STRUCTURE AND SPATIAL DISTRIBUTION OF SCLEROCARYA BIRREA (A. RICH.) HOCHST. STANDS IN NIGER’S SAHEL REGION

H. Abdourhamane, H. Rabiou, A. Diouf, B. Morou, A. Mahamane, R. Bellefontaine

The main purpose of this study was to analyse the population structure and spatial distribution of Sclerocarya birrea stands in the protected forests of Dan Kada Dodo and Dan Gado and their peripheral areas. These parameters have to be known to ensure that the stands are managed sustainably. Sample inventory plots measuring 50 x 20 m were identified by random stratified sampling in the three land use units identified (tree steppe, agroforestry sector, adjacent agricultural zones). Tree diameter at 1.30 m above the ground, total height and the two diameters perpendicular to the crown of S. birrea were measured. To define spatial distribution, S. birrea individuals were mapped in two 1.96 ha plots (140 x 140 m) in the “tree steppe” and “agroforestry sector” units. The results show that S. birrea individuals are distributed in random aggregates of varying sizes (about 7 m and 25 m), which is consistent with their zoochorous and barochorous fruit dispersal pattern and the capacity of the species for vegetative propagation. The highest densities (25.2 individuals/ha), basal areas (1.6 m2/ha) and average heights (6.9 m) were in the protected forest sectors. The bell-shaped distribution curve for stand height and diameter classes reflects the better representation of intermediate classes than extremes. However, the erratic structure observed in the “adjacent agricultural zones” indicates a highly irregular distribution of diameter classes. We conclude that S. birrea populations require more effective conservation, with more appropriate restoration strategies to be developed.

Keywords: Sclerocarya birrea, spatial structure, protected forests, land use, Niger.


Download
the article

HOW EVOLVING HOLOCENE LANDSCAPES ARE FILLING IN THE VALLEY BOTTOMS OF GABON’S LOPÉ NATIONAL PARK IN THE MID OGOOUÉ VALLEY

V. Nfoumou Obame, Makaya M’Voubou, D. Sebag, R. Oslisly, L. Bremond, M. Mbina Mounguengui, P. Giresse

Sedimentological and geochemical analyses and 14C dating were performed for a sedimentary core sample from the Lopé 2 marsh in the northern zone of Gabon’s Lopé National Park. The results produced a division of the core sample into three main units. The basal part of the core sample was dated to 2,320 years cal BP. At this time, the Lopé 2 marsh was a topographic hollow that flooded sporadically during the rainy season. This unit corresponds to a soil formation of clay, quartz and highly decomposed organic matter. The upper boundary of this unit corresponds to the end of the climatic deterioration that affected central Africa around 2,500 years BP. The second unit represents the period from 2,320 to 585 years cal BP. This shows a gradual decrease in the flow of quartz that reflects the increasing relative density of the marsh vegetation as the climate became more humid. The organic matter in this unit is of mixed origin, relatively abundant and with a high content of refractory material. The third unit, representing the period from 585 years cal BP to the present, shows plant cover associated with developing marshland (which began in unit 2) that was sustained by the humid climate. The organic matter here is rich in biological material.

Keywords: sedimentology, organic matter, geochemistry, marsh, recent Holocene, landscape, Gabon.


Download
the article



AGRICULTURAL RESEARCH FOR DEVELOPMENT

Legal information - Last update: October 2017
© CIRAD 2001 - Contact: bft@cirad.fr