Ollivier, M., Baraloto, C., & Marcon, E. (2007). A trait database for Guianan rain forest trees permits intra- and inter-specific contrasts. Ann. For. Sci., 64(7), 781–786.
Abstract: We present a plant trait database covering autecology for rain forest trees of French Guiana. The database comprises more than thirty traits including autecology (e. g., habitat associations and reproductive phenology), wood structure (e. g., density and tension characteristics) and physiology at the whole plant (e. g., carbon and nitrogen isotopes) and leaf level (e. g., specific leaf area, photosynthetic capacity). The current database describes traits for about nine hundred species from three hundred genera in one hundred families. For more than sixty species, data on twelve morphological and ecophysiological traits are provided for individual plants under different environmental conditions and at different ontogenetic stages. The database is thus unique in permitting intraspecific analyses, such as the effects of ontogenetic stages or environmental conditions on trait values and their relationships.
Keywords: plant traits; tropical forest; French Guiana; functional groups; plasticity; ontogeny
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Ruelle, J., Beauchene, J., Thibaut, A., & Thibaut, B. (2007). Comparison of physical and mechanical properties of tension and opposite wood from ten tropical rainforest trees from different species. Ann. For. Sci., 64(5), 503–510.
Abstract: On 10 trees from 10 species of French Guyana tropical rainforest in a clear active process of restoring verticality growth strains were measured in situ in order to determine the occurrence of tension wood within samples. Wood specimens were cut in the vicinity of the growth strains measurements in order to measure some mechanical and physical properties. As suspected, tensile growth strains was very much higher in tension wood zone, because longitudinal modulus of elasticity was slightly higher. Longitudinal shrinkage was also much higher in tension wood than in opposite wood.
Keywords: tension wood; opposite wood; tropical rainforest; physical and mechanical properties
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Bonal, D., Born, C., Brechet, C., Coste, S., Marcon, E., Roggy, J. C., et al. (2007). The successional status of tropical rainforest tree species is associated with differences in leaf carbon isotope discrimination and functional traits. Ann. For. Sci., 64(2), 169–176.
Abstract: We characterised the among species variability in leaf gas exchange and morphological traits under controlled conditions of seedlings of 22 tropical rainforest canopy species to understand the origin of the variability in leaf carbon isotope discrimination (Delta) among species with different growth and dynamic characteristics (successional gradient). Our results first suggest that these species pursue a consistent strategy in terms of. throughout their ontogeny (juveniles grown here versus canopy adult trees from the natural forest). Second, leaf Delta was negatively correlated with WUE and N, and positively correlated with g(s), but among species differences in Delta were mainly explained by differences in WUE. Finally, species belonging to different successional groups display distinct leaf functional and morphological traits. We confirmed that fast growing early successional species maximise carbon assimilation with high stomatal conductance. In contrast, fast and slow growing late successional species are both characterised by low carbon assimilation values, but by distinct stomatal conductance and leaf morphological features. Along the successional gradient, these differences result in much lower Delta for the intermediate species (i.e. fast growing late successional) as compared to the two other groups.
Keywords: C-13; functional diversity; leaf gas exchange; species grouping; tropical rainforest
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Fournier, M., Dlouhá, J., Jaouen, G., & Almeras, T. (2013). Integrative biomechanics for tree ecology: Beyond wood density and strength. J. Exp. Bot., 64(15), 4793–4815.
Abstract: Functional ecology has long considered the support function as important, but its biomechanical complexity is only just being elucidated. We show here that it can be described on the basis of four biomechanical traits, two safety traits against winds and self-buckling, and two motricity traits involved in sustaining an upright position, tropic motion velocity (MV) and posture control (PC). All these traits are integrated at the tree scale, combining tree size and shape together with wood properties. The assumption of trait constancy has been used to derive allometric scaling laws, but it was more recently found that observing their variations among environments and functional groups, or during ontogeny, provides more insights into adaptive syndromes of tree shape and wood properties. However, oversimpli-fed expressions have often been used, possibly concealing key adaptive drivers. An extreme case of oversimplification is the use of wood basic density as a proxy for safety. Actually, as wood density is involved in stiffiness, loads, and construction costs, the impact of its variations on safety is non-trivial. Moreover, other wood features, especially the microfibril angle (MFA), are also involved. Furthermore, wood is not only stiff and strong, but it also acts as a motor for MV and PC. The relevant wood trait for this is maturation strain asymmetry. Maturation strains vary with cell-wall characteristics such as MFA, rather than with wood density. Finally, the need for further studies about the ecological relevance of branching patterns, motricity traits, and growth responses to mechanical loads is discussed. © The Author 2013.
Keywords: Biomechanics; Ecological strategy; Gravitropism; Shape; Size; Trees; Wood
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Mayer, V. E., Lauth, J., & Orivel, J. (2017). Convergent structure and function of mycelial galleries in two unrelated Neotropical plant-ants. Insectes Sociaux, 64(3), 365–371.
Abstract: The construction process and use of galleries by Azteca brevis (Myrmicinae: Dolichoderinae) inhabiting Tetrathylacium macrophyllum (Salicaceae) were compared with Allomerus decemarticulatus (Myrmicinae: Solenopsidini) galleries on Hirtella physophora (Chrysobalanaceae). Though the two ant species are phylogenetically distant, the gallery structure seems to be surprisingly similar and structurally convergent: both are pierced with numerous holes and both ant species use Chaetothyrialean fungi to strengthen the gallery walls. Al. decemarticulatus is known to use the galleries for prey capture and whether this is also the case for Az. brevis was tested in field experiments. We placed Atta workers as potential prey/threat on the galleries and recorded the behaviour of both ant species. We found considerable behavioural differences between them: Al. decemarticulatus was quicker and more efficient at capture than was Az. brevis. While most Atta workers were captured after the first 5 min by Al. decemarticulatus, significantly fewer were captured by Az. brevis even after 20 min. Moreover, the captured Atta were sometimes simply discarded and not taken to the nest by Az. brevis. As a consequence, the major function of the galleries built by Az. brevis may, therefore, be defense against intruders in contrast to Al. decemarticulatus which uses them mainly for prey capture. This may be due to a higher need for protein in Al. decemarticulatus compared to coccid-raising Az. brevis.
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Lang, G., Marcon, E., & Puech, F. (2020). Distance-based measures of spatial concentration: introducing a relative density function. Ann. Reg. Sci., 64(2), 243–265.
Abstract: For more than a decade, distance-based methods have been widely employed and constantly improved in spatial economics. These methods are a very useful tool for accurately evaluating the spatial distribution of economic activity. We introduce a new distance-based statistical measure for evaluating the spatial concentration of industries. The m function is the first relative density function to be proposed in economics. This tool supplements the typology of distance-based methods recently drawn up by Marcon and Puech (J Econ Geogr 3(4):409–428, 2003). By considering several simulated and real examples, we show the advantages and the limits of the m function for detecting spatial structures in economics. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
Keywords: Agglomeration; Aggregation; Economic geography; Point patterns; Spatial concentration; accuracy assessment; econometrics; economic activity; economic geography; industrial agglomeration; industrial location; location decision; spatial analysis; spatial distribution
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Amusant, N., Fournier, M., & Beauchene, J. (2008). Colour and decay resistance and its relationships in Eperua grandiflora. Ann. For. Sci., 65(8), 806.
Abstract: Eperua grandiflora, which is widely distributed in the French Guiana forest region, shows high variability in decay resistance. Further information concerning this wood quality parameter is necessary, but standard testing methods are complex and time-consuming. We assessed the use of colorimetry to determine durability in heartwood samples from a range of trees. Eperua grandiflora colour parameters were measured using a CIELAB system, revealing that the tree effect was greater than the radial position and height effects. The wood samples were exposed to Coriolus versicolor and Antrodia sp. according to two European standards (En 350-1 and XP CEN TS 15083-1). Eperua grandiflora is more susceptible to brown rot. These two standards did not give the same durability classes. The high variation in natural durability was due to the tree effect. These two properties were found to be correlated and the assessment also distinguished the extreme durability classes but they are not sufficient to classify the class of durability of this species.
Keywords: natural durability; colour; decay resistance; variability; heartwood; tropical wood
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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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Coste, S., Roggy, J. C., Garraud, L., Heuret, P., Nicolini, E., & Dreyer, E. (2009). Does ontogeny modulate irradiance-elicited plasticity of leaf traits in saplings of rain-forest tree species? A test with Dicorynia guianensis and Tachigali melinonii (Fabaceae, Caesalpinioideae). Ann. For. Sci., 66(7), 701–709.
Abstract: Irradiance elicits a large plasticity in leaf traits, but little is known about the modulation of this plasticity by ontogeny. Interactive effects of relative irradiance and ontogeny were assessed on leaf traits for two tropical rainforest tree species: Dicorynia guianensis Amshoff and Tachigali melinonii (Harms) Barneby (Fabaceae, Caesalpinioideae). Eleven morphological and physiological leaf traits, relative to photosynthetic performance, were measured on saplings at three different architectural development stages (ASD 1, 2 and 3) and used to derive composite traits like photosynthetic N-use efficiency. Measurements were made along a natural irradiance gradient. The effect of ASD was very visible and differed between the two species. For Dicorynia guianensis, only leaf mass-per-area (LMA) significantly increased with ASDs whereas for Tachigali melinonii, almost all traits were affected by ASD: LMA, leaf N content and photosynthetic capacity increased from ASD 1 to ASD 3. Photosynthetic N-use-efficiency was not affected by ASD in any species. Leaf traits were severely modulated by irradiance, whereas the degree of plasticity was very similar among ASDs. Only few interactions were detected between irradiance and ASD, for leaf thickness, carbon content, and the ratio Chl/N in T. melinonii and for photosynthetic capacity in D. guianensis. We conclude that ontogenic development and irradiance-elicited plasticity modulated leaf traits, with almost no interaction, i.e., the degree of irradiance-elicited plasticity was stable across development stages and independent of ontogeny in these two species, at least in the early stages of development assessed here.
Keywords: plant architecture; phenotypic plasticity; photosynthetic capacity; leaf structure; tropical rain forest
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Tritsch, I., Gond, V., Oszwald, J., Davy, D., & Grenand, P. (2012). Territorial dynamics in the wayãpi and teko amerindian communities of the middle oyapock, camopi, French Guiana. Bois Forets Tropiques, 66(311), 49–61.
Abstract: Amerindian populations have been experiencing major socio-economic changes for several decades, in a context of rapid demographic growth. This article addresses the ways in which the Amerindian populations of French Guiana have adapted their land use and natural resource management systems to cope with the pressures exerted on their lands and lifestyles. The aim was to investigate the resilience of their systems for land and natural resource use. The concentration of Amerindian habitats around the town of Camopi, which is linked to the availability of health and school infrastructure and to efforts to promote a sedentary lifestyle, is a factor of increasing natural resource scarcity and social alienation. The system is adapting by fragmenting the Amerindian habitat into peripheral villages and extending farmlands along rivers to access to more space. These villages replicate patterns of spatial organisation that are similar to those found in traditional Wayãpi and Teko villages, except that habitation is sedentary, as families hope to have their villages equipped with at lEast drinking water and electrification. Habitat fragmentation is spatially limited by the time taken for daily journeys to school, and therefore by school bus services (dugout), which means that land use is effectively conditioned by services and infrasrtucture. Other living quarters are maintained at a distance from the village, so that the habitat is bi-local: families have a main home where services and infrastructure are available, and a secondary itinerant home further away, which is chosen according to the quality of farmland, the hunting yield of hunting resources, the history of the location and family networks. These distant homes are kept up by spending income from social assistance on transport. It's thus shown that these Amerindian systems for land and natural resource uses are highly adaptable, in that their sustainability is guaranteed by the reconstruction of a circular pattern of mobility in accordance with the intensity of resource use.
Keywords: Amerindian populations; French Guiana; Protected area; Slash-and-burn cultivation; System of natural resource use; Territorial management
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