Abstract: Water stress affecting long-lived trees is an important challenge in forestry. Due to global climate change, forest trees will be threatened by extreme conditions like flooding or drought. It is necessary to understand differences in stress tolerance within certain species and to investigate putative relations on genomic level. In this study, osmotic stress induced genes of Quercus ssp. were positioned on two genetic linkage maps of oak. An intra-specific cross 3P*A4 of Quercus robur consisting of 88 offspring and an inter-specific cross 11P*QS29 of Q. robur and Q. petraea comprising 72 full-sibs were analyzed for the inheritance of 14 loci represented by 34 individual single nucleotide polymorphisms. Seven genes in the intra-cross, as well as other six genes in the inter-cross could be mapped and one gene could not be localised due to the severe distortion of the segregation. The collection of expressed sequences involved ribosomal proteins, members of the oxylase/oxygenase gene family, betaine aldehyde dehydrogenase, Dc3 promoter-binding factor, a putative member of the nodulin family, glutathione-S-transferase and proteins with unknown functions. In the inter-cross, two linked markers exhibited 89% deficiency of heterozygosity. Thirteen genes were positioned on ten different oak chromosomes and can serve as orthologous markers in comparative mapping studies within Fagaceae. © Springer-Verlag 2005.

Abstract: Wasp nests range from simple to complex structures made of paper or mud. Here, we show that a Neotropical wasp of the genus Nitela builds its nest entirely by weaving endophytic fungal hyphae and spider silk harvested from the leaves growing in the understory of the rain forest in French Guiana.

Abstract: Wallaba (Eperua falcata) is a tropical wood that is known to have naturally high moisture related dimensional stability. Samples of wallaba heartwood were subjected to differential solvent extraction. Wood pieces that were extracted with methanol showed significantly greater swelling following rehydration from oven dry to 96% relative humidity than non- extracted samples and samples extracted with other solvents. Methanol soluble wallaba heartwood extract was purified by HPLC and the compounds present were characterized by NMR spectroscopy. The structure of 13 compounds in methanol extract was identified. The relative proportion of polar compounds in methanol extract was found to be high. The compounds identified are proposed to bind to the polymeric cell wall by means of multiple hydrogen bonds restricting the association of water and therefore act as natural anti-swelling agents.

Abstract: Volatile organic compounds (VOCs) are produced by a broad range of organisms, from bacteria to mammals, and they represent a vast chemical diversity. In plants, one of the preeminent roles of VOCs is their repellent or cytotoxic activity, which helps the plant deter its predators. Most studies on VOCs emitted by vegetative parts have been conducted in model plant species, and little is known about patterns of VOC emissions in diverse plant communities. We conducted a survey of the VOCs released immediately after mechanical damage of the bark and the leaves of 195 individual trees belonging to 55 tropical tree species in a lowland rainforest of French Guiana. We discovered a remarkably high chemical diversity, with 264 distinct VOCs and a mean of 37 compounds per species. Two monoterpenes (alpha-pinene and limonene) and two sesquiterpenes (beta-caryophyllene and alpha-copaene), which are known to have cytotoxic and deterrent effects, were the most frequent compounds in the sampled species. As has been established for floral scents, the blend of VOCs is largely species-specific and could be used to discriminate among 43 of the 55 sampled species. The species with the most diverse blends were found in the Sapindales, Laurales, and Magnoliales, indicating that VOC diversity is not uniformly distributed among tropical species. Interspecific variation in chemical diversity was caused mostly by variation in sesquiterpenes. This study emphasizes three aspects of VOC emission by tropical tree species: the species-specificity of the mixtures, the importance of sesquiterpenes, and the wide-ranging complexity of the mixtures.

Abstract: Very high spatial resolution (VHSR) optical satellite imagery has shown good potential to provide non-saturating proxies of tropical forest aboveground biomass (AGB) from the analysis of canopy texture, for instance through the Fourier Transform Textural Ordination method. Empirical case studies however showed that the relationship between Fourier texture features and forest AGB varies across forest types and regions of the world, limiting model transferability. A better understanding of the biophysical mechanisms on which canopy texture – forest AGB relation relies is a prerequisite to move toward broad scale applications. Here we simulated VHSR optical canopy scenes in identical sun-sensor geometry for 279 1-ha tropical forest inventory plots distributed across the tropics. Our aim was to assess the respective merits and complementarity of two types of texture analysis techniques (i.e. Fourier and lacunarity) on a set of forests with contrasted structure and geographical origin, and develop a general texture-based approach for tropical forest AGB mapping. Across forests, Fourier texture captured a gradient of stands mean crown size reflecting well the progressive changes in stand structure throughout forest aggradation phase (e.g. Pearson's r = − 0.42 with basal area) while lacunarity texture captured a gradient of canopy openness (, i.e. Pearson's r = − 0.57 with stand gap fraction). Both types of texture indices were highly complementary for predicting forest AGB at the global level (so-called FL-model). The residual error of the FL-model was structured across sites and could be partially captured with a bioclimatic proxy, further improving the performance of the global model (so-called FLE-model) and reducing site-level biases. The FLE model was tested on a set of real Pleiades images covering a mosaic of high-biomass forests in the Congo basin (mean AGB over 49 field plots: 359 ± 98 Mg ha− 1), leading to a significant relationship (R2 = 0.47 on validation data) with reasonable error levels (< 25% rRMSE). The increasing availability of VHSR optical sensors (such as from constellations of small satellite platforms) raises the possibility of routine repeated imaging of the world's tropical forests and suggests that texture-based analyses could become an essential tool in international efforts to monitor carbon emissions from deforestation and forest degradations (REDD +). © 2017 Elsevier Inc.