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Clair, B., Jaouen, G., Beauchene, J., & Fournier, M. (2003). Mapping radial, tangential and longitudinal shrinkages and relation to tension wood in discs of the tropical tree Symphonia globulifera. Holzforschung, 57(6), 665–671.
Abstract: A method for measuring shrinkage resulting from drying in the three anisotropic directions is developed and tested. Measurements are performed on sawn discs, a technique which simplifies preparation and enables large numbers of measurements. Shrinkage values can be represented as a map of the disc surface. The results indicate that comparisons between shrinkage distribution and tension wood distribution on the discs show a clear relationship and can be measured with relatively high accuracy in reference to the shrinkage map. In the long term, this method could be useful in the timber industry as a means for choosing the direction in which logs are cut depending on their type of wood composition.
Keywords: drying shrinkage; tension wood; Symphonia globulifera L. f.
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Dutech, C., Joly, H. I., & Jarne, P. (2004). Gene flow, historical population dynamics and genetic diversity within French Guianan populations of a rainforest tree species, Vouacapoua americana. Heredity, 92(2), 69–77.
Abstract: Both gene flow and historical events influence the genetic diversity of natural populations. One way to understand their respective impact is to analyze population genetic structure at large spatial scales. We studied the distribution of genetic diversity of 17 populations of Vouacapoua americana (Caesalpiniaceae) in French Guiana, using nine micro satellite loci. Low genetic diversity was observed within populations, with a mean allelic richness and gene diversity of 4.1 and 0.506, respectively, which could be due to low effective population size and/or past bottlenecks. Using the regression between F-st/(1-F-st), estimated between pairs of populations, and the logarithm of the geographical distance, the spatial genetic structure can partly be explained by isolation-by-distance and limited gene flow among populations. This result is in agreement with the species' biology, including seed and pollen dispersal by rodents and insects, respectively. In contrast, no clear genetic signal of historical events was found when examining genetic differentiation among populations in relation to biogeographical hypotheses or by testing for bottlenecks within populations. Our conclusion is that nuclear spatial genetic structure of V. americana, at the geographic scale of French Guiana, is better explained by gene flow rather than by historical events.
Keywords: bottleneck; climatic change; extinction-recolonization; microsatellite; neotropical rainforest; pollen and seed dispersal
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Gourlet-Fleury, S., Blanc, L., Picard, N., Sist, P., Dick, J., Nasi, R., et al. (2005). Grouping species for predicting mixed tropical forest dynamics: looking for a strategy. Ann. For. Sci., 62(8), 785–796.
Abstract: The high species diversity of mixed tropical forests hinders the development of forest dynamic models. A solution commonly adopted is to cluster species in groups. There are various methods for grouping species that can be linked to three strategies (i) the ecological subjective strategy, (ii) the ecological data-driven strategy, and (iii) the dynamic process strategy. In the first two strategies a species will be assigned to a single group while in the latter strategy, a specific grouping is defined for each process of population dynamics ( typically based on recruitment, growth, mortality). Little congruency or convergence is observed in the literature between any two classifications of species. This may be explained by the independence between the sets of tree characters used to build species groups, or by the intra-specific variability of these characters. We therefore recommend the dynamic process strategy as the most convenient strategy for building groups of species.
Keywords: cross-comparisons; functional groups; modelling strategy; species classifications
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Amusant, N., Beauchene, J., Fournier, M., Janin, G., & Thevenon, M. F. (2004). Decay resistance in Dicorynia guianensis Amsh.: analysis of inter-tree and intra-tree variability and relations with wood colour. Ann. For. Sci., 61(4), 373–380.
Abstract: Dicorynia guianensis Amsh. is very widespread in the forests of French Guiana and moreover is the leading species harvested in this area, but its main defect remains the great variability of wood durability, especially with respect to fungal decay. The aim of this work was to study this inter- and intra-tree variability in order to identify the parameters responsible for this variation (growth area, height and radial position) within the tree. The resistance decrease from the outer heartwood to the pith. Measurement of colour variation using the CIELAB (L*, a*, b*, C*, h*) system was performed at the intra-tree level to highlight the longitudinal and radial gradients of variation. Dicorynia guianensis becomes less red and dark from the outer to the inner heartwood and from the base to the top. Lastly, variations of colour and durability were correlated: the wood is less resistant the redder and darker it is.
Keywords: Dicorynia guianensis; Amazonian wood; wood colour/decay resistance; heartwood; variability
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Picard, N., Gourlet-Fleury, S., & Sist, P. (2003). Using process-dependent groups of species to model the dynamics of a tropical rainforest. Modelling Forest Systems, , 237–248.
Abstract: The high tree species diversity in tropical forests is difficult to take into account in models. The usual solution consists of defining groups of species and then adjusting a set of parameters for each group. In this study, we address this issue by allowing a species to move from one species group to another, depending on the biological process that is concerned. We developed this approach with a matrix model of forest dynamics, for a tropical rainforest in French Guiana, at Paracou, focusing on the methodological aspects. The forest dynamics is split into three components: recruitment, growth and mortality. We then built five recruitment groups, five growth groups and five mortality groups. One species is characterized by a combination of the three groups, thus yielding in total 5 X 5 X 5 = 125 possibilities, out of which 43 are actually observed. The resulting matrix model provides a better view of the floristic composition of the forest, and does not have more parameters than it would have with five global species groups. However, its predictions are no more precise than those of the matrix model based on five global groups.
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Dutech, C., Maggia, L., Tardy, C., Joly, H. I., & Jarne, P. (2003). Tracking a genetic signal of extinction-recolonization events in a neotropical tree species: Vouacapoua americana aublet in french guiana. Evolution, 57(12), 2753–2764.
Abstract: Drier periods from the late Pleistocene and early Holocene have been hypothesized to have caused the disappearance of various rainforest species over large geographical areas in South America and restricted the extant populations to mesic sites. Subsequent improvement in climatic conditions has been associated with recolonization. Changes in population size associated with these extinction-recolonization events should have affected genetic diversity within species. However, these historical hypotheses and their genetic consequences have rarely been tested in South America. Here, we examine the diversity of the chloroplast and nuclear genomes in a Neotropical rainforest tree species, Vouacapoua americana (Leguminosae, Caesalpinioideae) in French Guiana. The chloroplast diversity was analyzed using a polymerase chain reaction-restriction fragment length polymorphism method (six pairs of primers) in 29 populations distributed over most of French Guiana, and a subset of 17 populations was also analyzed at nine polymorphic microsatellite loci. To determine whether this species has experienced extinction-recolonization, we sampled populations in areas supposedly not or only slightly affected by climatic changes, where the populations would not have experienced frequent extinction, and in areas that appear to have been recently recolonized. In the putatively recolonized areas, we found patches of several thousands of hectares homogeneous for chloroplast variation that can be interpreted as the effect of recolonization processes from several geographical origins. In addition, we observed that, for both chloroplast and nuclear genomes, the populations in newly recolonized areas exhibited a significantly smaller allelic richness than others. Controlling for geographic distance, we also detected a significant correlation between chloroplast and nuclear population differentiation. This result indicates a cytonuclear disequilibrium that can be interpreted as a historical signal of a genetic divergence between fragmented populations. In conclusion, the spatial genetic structure of contemporary V. americana populations shows evidence that this species has experienced large extinction-recolonization events, which were possibly caused by past climatic change.
Keywords: allelic richness; caesalpinioideae; chloroplast DNA; climatic changes; cytonuclear disequilibrium; legummosae; microsatellite loci; tropical rainforest
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Tahiri, A., Amissa Adima, A., Adjé, F. A., & Amusant, N. (2011). Pesticide effects and screening of extracts of Azadirachta Indica (A.) Juss. on the Macrotermes bellicosus rambur termite. Effet pesticide et screening des extraits de Azadirachta indica (A.) Juss. sur le termite Macroterme, 65(310), 79–88.
Abstract: To recommend applications in the field of a naturally insecticide plant substance as an alternative to chemical control against termite attacks, several important prerequisites need to be satisfied to ensure its effectiveness. The toxicity, lethal dose, mode of action, persistence of insecticide effect and chemical composition of total aqueous, alcohol and hexane extracts of the leaves and seeds of the neem tree, Azadirachta indica, were tested with the Macrotermes bellicosus termite. The extracts were found to be highly toxic to termites on contact, killing the entire population tested. The insecticide effect of the extracts persisted from 2.4 to 4.2 days. The aqueous and hexane extracts were the most toxic (LD50 0.422±0.018 to 4,466±0,162 mg/l). Contact and inhalation were both essential to their effectiveness. The aqueous extract of seeds, which is the most active, is also capable of being transferred through the colony during social tasks. However, it seems to have an anti-appetent effect on termites and does not act by ingestion. It contains phenol compounds (tannins and flavonoids) and saponins. The hexane extract of seeds is oily and contains 11 fatty acids as well as terpenoids, flavonoids and saponins.
Keywords: Azadirachta indica; Pesticide properties; Phytochemical screening; Termite
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Zaremski, A., Gastonguay, L., Zaremski, C., Chaffanel, F., Le Floch, G., & Beauchene, J. (2013). Capacity of tropical forest soils of french guiana and réunion for depolluting the woods impregnated with biocides. Bois Forets Tropiques, 67(318), 51–58.
Abstract: Wood material for a long time was treated with fungicides or insecticides whose impact on the soil after leaching constitutes a real environmental problem. Nowadays, most of the studies on degradation of these toxic products was carried out with microorganisms which have been isolated in the laboratory. The present study sought to refine the knowledge vis-à-vis these microorganisms, especially wood-destroying fungi degrading pollutants in situ, from which few data are actually available. To decontaminate treated wood, the capacity of wooddestroying microorganisms from tropical forest soils of French Guiana and Reunion was evaluated to degrade toxic biocides. These are pentachlorophenol (PCP) and copper- chromium arsenic based compounds (CCA). Monitoring the degradation of samples of red pine, Pinus resinosa, shows that soils of French Guiana are more efficient than those of Reunion Island in terms of microbial activity vis-àvis these two biocides. A significant difference in loss of mass in specimens of red pine treated with CCA and PCP can range from single to double (respectively 18% and 30%). These findings confirm that CCA is less leacher and less degradable than the PCP by microorganisms in the soil. According to the scale of mass loss in laboratory tests, the wood so treated would be classified very not durable after three years of contact with soil, while the treatment is expected to be very durable.
Keywords: Bioremediation; Copper chromium arsenic(CCA) wood-destroying fungi; Depollution; Loss of mass; Pentachlorophenol(PCP); Treated timber; Tropical soil
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Gourlet-Fleury, S., Rossi, V., Rejou-Mechain, M., Freycon, V., Fayolle, A., Saint-André, L., et al. (2011). Environmental filtering of dense-wooded species controls above-ground biomass stored in African moist forests. J. Ecol., 99(4), 981–990.
Abstract: 1.Regional above-ground biomass estimates for tropical moist forests remain highly inaccurate mostly because they are based on extrapolations from a few plots scattered across a limited range of soils and other environmental conditions. When such conditions impact biomass, the estimation is biased. The effect of soil types on biomass has especially yielded controversial results. 2.We investigated the relationship between above-ground biomass and soil type in undisturbed moist forests in the Central African Republic. We tested the effects of soil texture, as a surrogate for soil resources availability and physical constraints (soil depth and hydromorphy) on biomass. Forest inventory data were collected for trees ≥20cm stem diameter in 2754 0.5ha plots scattered over 4888km2. The plots contained 224 taxons, of which 209 were identified to species. Soil types were characterized from a 1:1000000 scale soil map. Species-specific values for wood density were extracted from the CIRAD's data base of wood technological properties. 3.We found that basal area and biomass differ in their responses to soil type, ranging from 17.8m2ha-1 (217.5tha-1) to 22.3m2ha-1 (273.3tha-1). While shallow and hydromorphic soils support forests with both low stem basal area and low biomass, forests on deep resource-poor soils are typically low in basal area but as high in biomass as forests on deep resource-rich soils. We demonstrated that the environmental filtering of slow growing dense-wooded species on resource-poor soils compensates for the low basal area, and we discuss whether this filtering effect is due to low fertility or to low water reserve. 4.Synthesis. We showed that soil physical conditions constrained the amount of biomass stored in tropical moist forests. Contrary to previous reports, our results suggest that biomass is similar on resource-poor and resource-rich soils. This finding highlights both the importance of taking into account soil characteristics and species wood density when trying to predict regional patterns of biomass. Our findings have implications for the evaluation of biomass stocks in tropical forests, in the context of the international negotiations on climate change. © 2011 The Authors. Journal of Ecology © 2011 British Ecological Society.
Keywords: Basal area; Central African Republic; Determinants of plant community diversity and structure; Life-history strategy; Soil fertility; Species sorting; Vital rates; Water reserve; Wood density; aboveground biomass; basal area; climate change; data set; database; diameter; forest ecosystem; forest inventory; life history trait; nutrient availability; physical property; plant community; resource availability; soil fertility; soil nutrient; soil texture; soil type; stem; tropical forest; wood; Central African Republic
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Marcon, E., & Herault, B. (2015). entropart: An R package to measure and partition diversity. Journal of Statistical Software, 67(8), 1–26.
Abstract: entropart is a package for R designed to estimate diversity based on HCDT entropy or similarity-based entropy. It allows calculating species-neutral, phylogenetic and functional entropy and diversity, partitioning them and correcting them for estimation bias. © 2015, American Statistical Association. All rights reserved.
Keywords: Biodiversity; Entropy; Partitioning
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