Bois et forêts des tropiques

Abstracts & articles: n° 334
(4th quarter 2017)


All abstracts
(In French, English and Spanish)

New issue

Issue 334


 

EFFECTS OF DIFFERENT NANOCLAY
LOADINGS ON THE PHYSICAL
AND MECHANICAL PROPERTIES
OF MELIA COMPOSITA PARTICLE BOARD

N. Ismita, C. Lokesh

This study investigated the effects of adding a filler of nano-sized particles of Cloisite Na+ (nanoclay) to urea-formaldehyde resin on the physical and mechanical properties of particle boards made with this resin. Cloisite Na+ was introduced at rates of 2%, 4% and 6% of the dry mass of the resin. Density, water absorption (WA), thickness swelling (TS), modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond strength (IB) were measured to evaluate the performance of the boards. Significant improvements were observed for TS, MOR and MOE when Cloisite Na+ was added to the resin. More specifically, in samples bonded with UF resin and 6% nanoclay, 34% and 65% increases were observed in MOR and MOE respectively compared to the control boards.

Keywords: Melia composita, mechanical properties, nanoclay, particle board, physical properties, urea-formaldehyde.


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IMPACT OF TREE SHADING ON THE MICROCLIMATE OF A COFFEE PLANTATION: A CASE STUDY FROM THE PERUVIAN AMAZON

L. Ehrenbergerová, M. Šenfeldr, H. Habrová

Agroforestry is considered to be one of the agricultural strategies that could help to adapt crops to climate change. As a case study, we compared the microclimatic conditions at a location where Coffea arabica was shaded mainly by Inga spp. with the conditions in an unshaded C. arabica monoculture in the same coffee plantation in the Pasco region in Peru. Air temperature, air humidity, soil temperature and soil water availability were measured over three years. The results indicate that tree shading reduced the mean air temperature by 0.4 ± 0.04 °C and soil temperature by 1.7 ± 0.3 °C, and increased air humidity by 3.9 ± 0.4% compared to the unshaded area. However, the monthly average air temperature and even the monthly maximum in the unshaded area did not greatly exceed the limits for photosynthesis (upper limit 34 °C). Moreover, the minimum monthly air temperatures were similar in the shaded and unshaded areas. The soil temperatures did, however, fluctuate more markedly in the unshaded area. One of the main findings of this case study was that soil conditions were drier in the shaded area, especially at the beginning and end of the dry season. This was probably due to increased total transpiration resulting from that contributed by the shade trees. Thus, higher water uptake in agroforestry systems might have a negative impact on the growth of coffee plants where water availability is a limiting factor.

Keywords: agroforestry system, air humidity, Coffea arabica, soil temperature, soil water availability, Peru, Amazonia.


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ACACIA AURICULIFORMIS PRODUCTION IN THE MAMPU AGROFORESTRY ZONE ON THE BATÉKÉ PLATEAU, DEMOCRATIC REPUBLIC OF CONGO

P. Proces, E. Dubiez, F. Bisiaux, A. Péroches, A. Fayolle

The Mampu agroforestry zone on the Batéké plateau in the Democratic Republic of Congo, which has been managed with Acacia auriculiformis shade trees for over twenty years by local communities, supplies subsistence products and fuel wood to Kinshasa. Thanks to international grant funding, this agroforestry system, which integrates traditional slashand- burn cultivation, has been replicated in many places across the RDC, but its performance has never been assessed. The aim of this study was to estimate Acacia auriculiformis production in terms of total biomass and usable biomass for charcoal (stems and branches more than 4 cm in diameter) as part of the agroforestry system. To do so, two local allometric equations for total and usable biomass were adjusted from destructive testing data. Using existing inventory data (n = 112 plots), we identified significant structural heterogeneity throughout the rotation period (8-10 years) but also among plots of the same age. Despite this heterogeneity, which may be accounted for by environmental conditions on site and/or by differences in the handling of plot management techniques, production is comparable to that observed at other sites, averaging 145 tonnes per hectare over 10 years. The Mampu agroforestry system has many advantages, including direct services creating rural employment and combined production of subsistence goods and charcoal, but also indirect services such as avoided deforestation and carbon sequestration. The system’s sustainability and dissemination should nevertheless be discussed.

Keywords: Acacia auriculiformis, biomass allocation, allometric equation, biomass expansion factor, forest inventory, volume table, short rotation, Democratic Republic of Congo.


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PRODUCTION OF ARGANIA SPINOSA SEEDLINGS IN MOROCCO: CHOOSING THE RIGHT CONTAINER AND SUBSTRATE

A. Ferradous, M. Hafidi, M. Alifriqui, A. Ouhammou

To obtain high quality argan seedlings (Argania spinosa L. Skeels) in the nursery, eight types of containers and three different substrates for off-ground cultivation (shredded composted branches of Acacia cyanophylla, composted hulls of Tetraclinis articulata seeds, commercial peat) mixed with leaf mould in different proportions were tested. Physico-chemical analysis of the substrates showed that the two locally produced types of compost were better indicated for the production of high quality argan seedlings. These substrates could be an alternative to costly, imported peat-based substrates. Compost can be produced satisfactorily from shredded Acacia cyanophylla branches to meet the needs of local tree nurseries. Changes in morphological parameters and analyses of the seedlings after seven months in the nursery showed that a 400 ml container is suitable for the production of argan seedlings of similar quality to that obtained with 800 ml polythene bags. These results are a first step towards mastering techniques for off-ground production of argan seedlings and other indigenous Moroccan tree species. Further study would be needed on other aspects of seedling production in Moroccan nurseries, such as irrigation, fertilisation and mycorhization. Trial plantations are under consideration to confirm the results of this study.

Keywords: argan tree, Argania spinosa, seedling, container, substrate, nursery, compost, peat, Morocco.


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ETHNIC AND GENERATIONAL DIFFERENCES IN TRADITIONAL KNOWLEDGE AND CULTURAL IMPORTANCE OF LANNEA MICROCARPA ENGL. & K. KRAUSE IN BENIN’S SUDANIAN SAVANNAH

E. O. A. Goudégnon, F. G. Vodouhê, G. N. Gouwakinnou, V. K. Salako, M. Oumorou

Understanding the socio-cultural importance of indigenous fruit trees (IFT) and its determining factors is a prerequisite for developing their value and making management decisions. This study documented traditional knowledge (TK) and the cultural importance (CI) of Lannea microcarpa, a neglected and underused indigenous fruit tree found in Benin’s Sudanian region. The study further tested whether TK and CI varied according to ethnic groups and generations. We collected data on the uses and importance of the species from 262 informants who were randomly selected within its zone of occurrence, using free lists and scoring, respectively. Twenty-eight specific usages divided in eigth categories of uses were reported, of which 21 were medicinal, 2 were commercial, and 1 each was for human food, fodder, firewood, construction, packaging and toothpicks. Contrary to the other use categories, traditional knowledge on food uses did not vary either between generations or among ethnic groups. In addition, food use was culturally the most important, followed by medicinal uses. Overall, the fruit was the most preferred and most frequently commercialised part of the plant. Medical conditions treated with L. microcarpa include anaemia, diarrhoea, coughs, ulcers, stomach aches and blood evacuation after childbirth. Our findings suggest that domestication of L. microcarpa should prioritise the fruit, which is the most valued part of the plant. Further studies should therefore focus on the domestication potential of L. microcarpa for its fruit traits and on how to improve fruit production.

Keywords: Lannea microcarpa, folk knowledge, development of fruit species, Sudanian zone, Benin.


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QUALITY AND USES OF TIMBER FROM FIVE FOREST SPECIES SUITED TO PLANTATION MANAGEMENT AND TESTED IN FRENCH GUIANA

H. Morel, E. Nicolini, J. Bossu, L. Blanc, J. Beauchêne

Forest plantation trials have been conducted in French Guiana since the early 1960s with over 138 tree species (70 native and 68 exotic). A recent study on their productivity in plantations (ForesTreeCulture project, 2013-2015) showed the high potential of three native species (Simarouba amara Aubl., Vochysia tomentosa (G. Mey.) DC., Bagassa guianensis (Aubl.)) and one West African species (Tarrietia utilis Sprague), all of which produced timber volumes in excess of 20 m3/ha/year. However, the properties of these as commercial species are known only from trees that have grown in their natural forest environment. This article describes the properties of their timber when produced in plantation conditions – density, shrinkage, elasticity, angle of the grain, durability – and discusses the future potential and uses of each. A fourth species, Cordia alliodora ((Ruiz & Pavon) Oken), was also selected for study although it has not yet been planted in French Guiana. This species is native to French Guiana and well known across Latin America for its timber and high potential for growth in managed environments.

Keywords: technical properties, timber quality, plantation, French Guiana.


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ACADEMIC THESIS ABSTRACT
Drivers of fungal community composition in Corsican forests: role of disturbance and plant composition

Adrien Taudière

ABSTRACT
Studies of the ecology of micro-organisms began only recently despite their intrinsic importance — both practical and theoretical — and their central role in forming the niche habitats of macro-organisms. Plant-fungi interactions offer a relevant model for studies of the ecology of micro-organisms interacting with macro-organisms because of their considerable ecological and economic value as well as their high taxonomic and ecological diversity. Using next-generation sequencing (NGS) and network analysis, we explored some of the drivers of fungal community composition in Corsica, at various scales and in three ecological guilds: ectomycorrhizal, endophytic and saprotrophic fungi. We investigated the effects on fungal communities of disturbance (e.g. fire and treefall), environmental variables (e.g. soil depth), constraints due to interactions with host plants (e.g. taxonomy) and dispersion. Some patterns of community assembly are similar across guilds and may be governed by the same mechanisms. We found wide variations in fungal communities at the micro-regional scale among the guilds studied and between forests with a different history of wildfires. However, the relative importance of assembly processes and the spatial scales at which they occur vary across guilds. In Corsican pine forests, fifteen years after a fire, the diversity of soil fungus is close to the diversity in unburned stands. Despite the absence of effects on diversity, fire produces clear shifts in the composition of soil fungus communities, in particular for saprobic fungi. We discuss the implications of these findings for plant and fungal community ecologists and for managers of natural areas.

Keywords: fungi, mycorrhiza, fire regime, community ecology, canopy gaps, decomposition, Pinus nigra subsp. laricio, mixed forest, Corsica, Mediterranean, France.


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ACADEMIC THESIS ABSTRACT
Evolutionary history of the Afzelia Smith (Leguminosae - Caesalpinioideae) complex in forest and savannah ecosystems of tropical Africa

Segbedji Armel Loïc Donkpegan

ABSTRACT
The genus Afzelia Smith includes seven African tree species: two are found in the Zambezi region, one in the Sudanian region and four in the Guinea-Congo region. These taxa are commercially valuable but because they are difficult to distinguish, they are marketed under the same commercial name, either “doussié” or “afzelia”, which complicates sustainable management of their populations. The aim of this PhD thesis is to characterize the evolutionary history of the Afzelia genus. More specifically, our study aims to: (i) assess the extent of morphological divergence within the Afzelia genus and describe the phylogenetic relationships in order to quantify the reproductive isolation of the different taxa by identifying the role of past climate change and / or ecological gradients in the speciation of the genus; (ii) analyze the spatial genetic diversity and structure of Afzelia spp.; (iii) identify and describe the ecological, biotic and abiotic factors that may influence population-level gene flows in an Afzelia species (A. bipindensis). Our morpho-genetic analysis of the different species confirmed the strong botanical resemblance between the taxa. The savannah species are diploid and their genome is half the size of the forest species, which are tetraploid. The phylogenies of the genes, nuclear and chloroplastic, are not the same. The differences observed could have been generated by ancient hybridization between species, which would have occurred between the forest lineages and those of A. quanzensis, a Zambezi savannah species. Polyploidy probably emerged during the evolutionary history of the genus between 7 and 9.4 million years ago. Bayesian assignment and reproductive isolation analyses also suggested interspecies crossing, but only among forest species distributed sympatrically. On a more limited spatial scale, two well differentiated genetic groups of A. bipindensis were observed to be sympatric. These show differences in their morphology and flowering phenology that could contribute to their reproductive isolation. This study made several important findings: discovery of a polyploid complex within the Afzelia genus, confirmation of the boundaries of diploid savannah species and the need to revise the taxonomy of tetraploid forest species.

Keywords: Afzelia spp., phylogeny, phylogeography, genetic diversity, polyploidy, gene flow, phenology, savannah, tropical forests, tropical Africa.


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