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Bremaud, I., Gril, J., & Thibaut, B. (2011). Anisotropy of wood vibrational properties: dependence on grain angle and review of literature data. Wood Sci. Technol., 45(4), 735–754.
Abstract: The anisotropy of vibrational properties influences the acoustic behaviour of wooden pieces and their dependence on grain angle (GA). As most pieces of wood include some GA, either for technological reasons or due to grain deviations inside trunks, predicting its repercussions would be useful. This paper aims at evaluating the variability in the anisotropy of wood vibrational properties and analysing resulting trends as a function of orientation. GA dependence is described by a model based on transformation formulas applied to complex compliances, and literature data on anisotropic vibrational properties are reviewed. Ranges of variability, as well as representative sets of viscoelastic anisotropic parameters, are defined for mean hardwoods and softwoods and for contrasted wood types. GA-dependence calculations are in close agreement with published experimental results and allow comparing the sensitivity of different woods to GA. Calculated trends in damping coefficient (tan delta) and in specific modulus of elasticity (E'/rho) allow reconstructing the general tan delta-E'/rho statistical relationships previously reported. Trends for woods with different mechanical parameters merge into a single curve if anisotropic ratios (both elastic and of damping) are correlated between them, and with axial properties, as is indicated by the collected data. On the other hand, varying damping coefficient independently results in parallel curves, which coincide with observations on chemically modified woods, either “artificially”, or by natural extractives.
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Lambs, L., Bompy, F., Imbert, D., Corenblit, D., & Dulormne, M. (2015). Seawater and freshwater circulations through coastal forested wetlands on a Caribbean Island. Water, 7(8), 4108–4128.
Abstract: Structure and composition of coastal forested wetlands are mainly controlled by local topography and soil salinity. Hydrology plays a major role in relation with tides, seaward, and freshwater inputs, landward. We report here the results of a two-year study undertaken in a coastal plain of the Guadeloupe archipelago (FWI). As elsewhere in the Caribbean islands, the study area is characterized by a micro-tidal regime and a highly seasonal climate. This work aimed at understanding groundwater dynamics and origin (seawater/freshwater) both at ecosystems and stand levels. These hydrological processes were assessed through 18O/16O and 2H/1H isotopic analyses, and from monthly monitoring of water level and soil salinity at five study sites located in mangrove (3) and swamp forest (2). Our results highlight the importance of freshwater budget imbalance during low rainfall periods. Sustained and/or delayed dry seasons cause soil salinity to rise at the mangrove/swamp forest ecotone. As current models on climate change project decreasing rainfall amounts over the inner Caribbean region, one may expect for this area an inland progression of the mangrove forest to the expense of the nearby swamp forest. © 2015 by the authors.
Keywords: 18O/2H stable isotope; Hydrology; Mangrove; Salinity; Swamp forest; Water level
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Cohen, M. C. L., Behling, H., Lara, R. J., Smith, C. B., Matos, H. R. S., & Vedel, V. (2009). Impact of sea-level and climatic changes on the Amazon coastal wetlands during the late Holocene. Veg. Hist. Archaeobot., 18(6), 425–439.
Abstract: Wetland dynamics in northern Brazil during the Holocene were studied by pollen analysis and AMS radiocarbon dating of three cores. Near the Amazon mouth region, covered mainly by primary Amazon coastal forest and herbaceous vegetation, the pollen record indicates the dominance of mangroves between 4800 and 1100 cal yr B.P. A contraction of the mangrove area and an expansion of herbaceous and fern vegetation occurred between 1100 and 750 cal yr B.P. The period between 750 and 200 cal yr B.P. is characterized by an expansion of mangrove and a decrease in herbaceous and fern vegetation. This trend continued until the present. On Atalaia Island, the sediment core indicates a period with poor pollen preservation between 830 and 630 cal yr B.P. Between 630 and 330 cal yr B.P., mangroves expanded. Later, up to 45 cal yr B.P., the mangrove area decreased and the herbaceous vegetation expanded. During the last hundred years, the relative sea-level rise most probably favored the mangrove expansion as far as the topographically highest sector on this island, while the herbaceous vegetation decreased. The pollen data from Agua Preta Lake indicate dry conditions, as reflected by the poor pollen preservation between 390 and 240 cal yr B.P. Between 240 and 60 cal yr B.P., restinga and Amazon coastal forest with palms dominated this region. For the last 120 years, the record indicates an expansion of the mangrove area. However, recent confinement of mangrove development to the topographically highest area, and the loss of mangrove areas on the lowest surfaces have led to a net loss of mangrove coverage during the last decades.
Keywords: Mangrove; Marajo Island; Pollen analysis; Sea-level
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Talaga, S., Dezerald, O., Carteron, A., Leroy, C., Carrias, J. - F., Céréghino, R., et al. (2017). Urbanization impacts the taxonomic and functional structure of aquatic macroinvertebrate communities in a small Neotropical city. Urban Ecosystems, 20(5), 1001–1009.
Abstract: Due to habitat fragmentation, resource disruption and pollution, urbanization is one of the most destructive forms of anthropization affecting ecosystems worldwide. Generally, human-mediated perturbations dramatically alter species diversity in urban sites compared to the surroundings, thus influencing the functioning of the entire ecosystem. We investigated the taxonomic and functional diversity patterns of the aquatic macroinvertebrate communities in tank bromeliads by comparing those found in a small Neotropical city with those from an adjacent rural site. Changes in the quality of detrital inputs in relation to lower tree diversity and the presence of synanthropic species are likely important driving forces behind the observed structural changes in the urban site. Leaf-litter processors (i.e., shredders, scrapers) were positively affected in the urban site, while filter-feeders that process smaller particles produced by the activity of the shredders were negatively affected. Because we cannot ascertain whether the decline in filter-feeders is related to food web-mediated effects or to competitive exclusion (Aedes aegypti mosquitoes were present in urban bromeliads only), further studies are necessary to account for the effects of intra-guild competition or inter-guild facilitation. © 2017, Springer Science+Business Media New York.
Keywords: Aedes aegypti; Bioindicator; Diversity; Functional traits; Tank bromeliads; Urban ecology
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Duplais, C., Papon, N., & Courdavault, V. (2020). Tracking the Origin and Evolution of Plant Metabolites. Trends Plant Sci., 25(12), 1182–1184.
Abstract: Iridoids are monoterpenes that are produced by various plants as chemical defense molecules. Lichman et al. recently described the timeline of molecular events that underpin the re-emergence of iridoid biosynthesis in an independent lineage of aromatic plants (catnip). This study represents a benchmark for studying enzyme and metabolite evolution in different clades across the tree of life. © 2020 Elsevier Ltd
Keywords: enzyme evolution; iridoids; Lamiaceae; nepetalactone; plant metabolites
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Christensen-Dalsgaard, K. K., Ennos, A. R., & Fournier, M. (2008). Are radial changes in vascular anatomy mechanically induced or an ageing process? Evidence from observations on buttressed tree root systems. Trees-Struct. Funct., 22(4), 543–550.
Abstract: To investigate the effect of changes in mechanical loading conditions on radial anatomical patterns, we here compare the trunk with the roots in two locations of three species of buttressed trees. The proximal part of the buttress roots is highly mechanically loaded throughout juvenile growth whereas the distal part of the buttresses is though to be mechanically unimportant at formation but become progressively more mechanically loaded during growth. We measured the frequency and diameter of the vessels and the vessel area fraction, and from this calculated the specific conductivity of tissue samples of the core-, intermediate- and outer wood. As in previous studies there was an increase in vessel size, vessel area fraction and specific conductivity from the pith to the bark in the trunk. In the proximal part of the buttress roots, however, there was no increase in vessel size and conductivity from core wood and out in agreement with the high mechanical loading found here throughout growth. There was instead a decrease in vessel size, vessel area fraction and specific conductivity from core- to outer wood in the distal part of the buttress roots in accordance with the increase in mechanical loading. Hence, it appears that the radial anatomical patterns are not a passive function of cambial ageing but may be modified in response to local mechanical loading.
Keywords: wood; anatomy; mechanical loading; tree development; vessels
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Ruelle, J., Yoshida, M., Clair, B., & Thibaut, B. (2007). Peculiar tension wood structure in Laetia procera (Poepp.) Eichl. (Flacourtiaceae). Trees-Struct. Funct., 21(3), 345–355.
Abstract: Tension wood of Laetia procera (Poepp.) Eichl. (Flacourtiaceae), a neo-tropical forest species, shows a peculiar secondary wall structure, with an alternance of thick and thin layers, while opposite wood of this species has a typical secondary wall structure (S1 + S2 + S3). Samples for the study of microstructural properties were collected upon the estimation of growth stresses in the living tree, in order to analyze the correlation of the former with the latter. Investigation using optical microscopy, scanning electron microscopy and UV microspectrophotometry allowed the description of the anatomy, ultra-structure and chemistry of this peculiar polylaminate secondary wall. In the thick layers, cellulose microfibril angle is very low (i.e., microfibril orientation is close to fibre axis) and cellulose microfibrils are well organized and parallel to each other. In the thin layers, microfibrils (only observable in the inner layer) are less organized and are oriented with a large angle relative to the axis of the cell. Thick layers are lightly lignified although thin layers show a higher content of lignin, close to that of opposite wood secondary wall. The more the wood was under tensile stress, the less the secondary wall was lignified, and lower the syringyl on guaiacyl lignin units' ratio was. The innermost layer of the secondary wall looks like a typical S3 layer with large microfibril angle and lignin occurrence. The interest of this kind of structure for the understanding of stress generation is discussed.
Keywords: tension wood; tropical rainforest species; UV microspectrophotometry; scanning electron microscopy; cellulose microfibril angle
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Leroy, C., Gueroult, M., Wahyuni, N. S., Escoute, J., Cereghino, R., Sabatier, S., et al. (2009). Morphogenetic trends in the morphological, optical and biochemical features of phyllodes in Acacia mangium Willd (Mimosaceae). Trees-Struct. Funct., 23(1), 37–49.
Abstract: Endogenous variations in the annual growth of trees suggest that similar trends would occur in phyllodes. In comparison to leaves, the characteristics of phyllodes are less well known, hence this study examines the effects of architectural position and age of tree on the phyllodes of Acacia mangium. Phyllodes were investigated on 1-, 2-, and 3-year-old trees from three axis positions within the crown. We focused on the morphological, optical and biochemical traits of the phyllodes. The increase in phyllode area and lamina thickness is more pronounced in the older trees. Leaf mass area (LMA), stomatal density, nitrogen and chlorophyll content increase with tree age. The values of these characteristics decrease from the main stem to the lower branches for the older trees. Phyllode light absorptance increased with tree age whereas reflectance was higher for the upper position compared to the lower position within the crown. Carotenoid content and chlorophyll a/b ratio were higher for the younger phyllodes of younger trees. Increasing tree size induced modifications in the phyllode characteristics which are influenced by both morphogenetic and light gradients within the crown. This study demonstrated pronounced changes in terms of morphological and functional indicators of photosynthetic capacity in relation to phyllode position within the crown and to tree age. These morphogenetic effects on the phyllode characteristics should be taken into account in studies on phenotypic plasticity.
Keywords: Chlorophyll; Phyllode morphology; Phyllode anatomy; Nitrogen; Optical properties; Plant architecture
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Almeras, T., Yoshida, M., & Okuyama, T. (2006). Strains inside xylem and inner bark of a stem submitted to a change in hydrostatic pressure. Trees-Struct. Funct., 20(4), 460–467.
Abstract: Tangential strains were measured with strain gauges at the surface of xylem and inner bark of saplings of Cryptomeria japonica D. Don. and Fagus silvatica L. during a pressurization test. The test consists in submitting the whole sapling to an artificially imposed hydrostatic pressure of increasing magnitude. The elastic response of the stems was found linear both at the surface of xylem and inner bark. A simple geometric model allows to compute radial strains in each tissue from tangential strain data. Inside inner bark, radial strains are much larger than tangential strains, because tangential strains are restrained by the core of wood. The material compliance of each tissue was computed as the ratio between the radial strain and the pressure that caused it. The material compliance of xylem is much lower than that of inner bark, but, as its thickness is much larger, its contribution to the apparent behavior of the stem is not negligible. Computation of material compliances by this pressurization test provides information about the specific behavior of each tissue in response to hydrostatic pressure. This can be used to estimate and interpret the calibration factor linking the water status of the plant to the apparent strain measured at its surface.
Keywords: diurnal strains; hydrostatic pressure; xylem; inner bark; mechanical properties
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Almeras, T., Thibaut, A., & Gril, J. (2005). Effect of circumferential heterogeneity of wood maturation strain, modulus of elasticity and radial growth on the regulation of stem orientation in trees. Trees-Struct. Funct., 19(4), 457–467.
Abstract: Active mechanisms of re-orientation are necessary to maintain the verticality of tree stems. They are achieved through the production of reaction wood, associated with circumferential variations of three factors related to cambial activity: maturation strain, longitudinal modulus of elasticity (MOE) and eccentric growth. These factors were measured on 17 mature trees from different botanical families and geographical locations. Various patterns of circumferential variation of these factors were identified. A biomechanical analysis based on beam theory was performed to quantify the individual impact of each factor. The main factor of re-orientation is the circumferential variation of maturation strains. However, this factor alone explains only 57% of the re-orientations. Other factors also have an effect through their interaction with maturation strains. Eccentric growth is generally associated with heterogeneity of maturation strains, and has an important complementary role, by increasing the width of wood with high maturation strain. Without this factor, the efficiency of re-orientations would be reduced by 31% for angiosperms and 26% for gymnosperms. In the case of angiosperms, MOE is often larger in tension wood than in normal wood. Without these variations, the efficiency of re-orientations would be reduced by 13%. In the case of gymnosperm trees, MOE of compression wood is lower than that of normal wood, so that re-orientation efficiency would be increased by 24% without this factor of variations.
Keywords: biomechanics; reaction wood; maturation strain; Young's modulus; eccentricity
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