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Bosc, A., De Grandcourt, A., & Loustau, D. (2003). Variability of stem and branch maintenance respiration in a Pinus pinaster tree. Tree Physiol., 23(4), 227–236.
Abstract: The relationship between maintenance respiration (R.) of woody organs and their structural characteristics was explored in adult Pinus pinaster Ait. trees. We measured R-m on 75 stem and branch segments of different ages (from 3 to 24 years) and diameters (from 1 to 35 cm). The temperature response of R-m was derived from field measurements based on a classical exponential function with Q(10) = 2.13. Relationships between R-m and the dimensions of the woody organs were analyzed under controlled conditions in the laboratory. The surface area of a woody organ was a better predictor of R-m than volume, but surface area failed to account for the observed within-tree variability of R-m among stems, branches and twigs. Two simple models were proposed to predict the variability of R-m at 15 degreesC in an adult tree. Model 1, a linear function model based on the dry mass and nitrogen concentration of sapwood and phloem tissues, explained most of the variability of R-m in branches and stems (R-2 = 0.97). We concluded that the respective contributions of the phloem and sapwood depend on the location and diameter of the woody organ. Model 2, a power-law function model based on the length, diameter and age of the sample, explained the same variance of R-m as Model 1 and is appropriate for scaling R-m to the stand level. Models 1 and 2 appear to explain a larger variability of R-m than models based on stem area or sapwood mass.
Keywords: model; nitrogen; phloem; sapwood; temperature
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Degen, B., & Roubilk, D. W. (2004). Effects of animal pollination on pollen dispersal, selfing, and effective population size of tropical trees: A simulation study. Biotropica, 36(2), 165–179.
Abstract: Animals, especially insects, are principal pollen vectors of tropical trees and have behavior patterns that affect gene dispersal. Here, we explore complex pollination systems using a new simulation model Eco-Gene and considering, among other factors, flowering synchrony. spatial distribution of trees, degree of selfing, population densities, pollinator flight distances, pollen deposition, and pollinator response to floral display size. Sensitivity analyses using two contrasting tree data sets (Jacaranda copaia and Dipteryx odorata) determined the importance of each parameter on three response variables: the proportion of seeds from self-pollination, effective population size, and pollen dispersal. Spatial considerations and attractiveness of floral displays were prominent features determining the population genetic result of pollinators, and some biological implications of the results are discussed.
Keywords: Amazon; bees; Brazil; Dipteryx; Jacaranda; model; pollination; sensitivity analysis; trees
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Morel, H., Lehnebach, R., Cigna, J., Ruelle, J., Nicolini, É., & Beauchene, J. (2018). Basic wood density variations of Parkia velutina Benoist, a long-lived heliophilic Neotropical rainforest tree. Bois et Forets des Tropiques, 335, 59–69.
Abstract: Investigations of basic radial wood density (WD) in tropical trees revealed linear patterns and some curvilinear patterns. Studies usually disregard longitudinal variations, which are often considered to be similar to radial variations. This study aimed to show (1) a new radial curvilinear WD pattern, (2) differences in amplitude between radial and longitudinal gradients and (3) to partition WD variations according to different scales in Parkia velutina, an emergent tree found in Neotropical rain forests. We collected full discs from six felled trees and radial cores from 10 standing trees to check WD variability, plus one dominant axis per tree for analysis of height growth rates. This species showed very high growth rates indicative of heliophilic habits. WD varied from 0.194 to 0.642 g/cm3. Such amplitude is rarely observed within the same tree. Radial variation in WD was curvilinear, with an amplitude generally less than the longitudinal amplitude. Consequently, in mature trees, WD values in the crown were higher than those in the outer trunk. WD variations can be highly significant at different scales. The variance partitioning also revealed that the whole WD range of Parkia velutina is more accurately estimated intra-individually when both longitudinal and radial gradient are covered.
Keywords: Curvilinear pattern; French Guiana; Intra-tree; Tropical species
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Aubry-Kientz, M., Herault, B., Ayotte-Trépanier, C., Baraloto, C., & Rossi, V. (2013). Toward Trait-Based Mortality Models for Tropical Forests. PLoS ONE, 8(5), e63678.
Abstract: Tree mortality in tropical forests is a complex ecological process for which modelling approaches need to be improved to better understand, and then predict, the evolution of tree mortality in response to global change. The mortality model introduced here computes an individual probability of dying for each tree in a community. The mortality model uses the ontogenetic stage of the tree because youngest and oldest trees are more likely to die. Functional traits are integrated as proxies of the ecological strategies of the trees to permit generalization among all species in the community. Data used to parametrize the model were collected at Paracou study site, a tropical rain forest in French Guiana, where 20,408 trees have been censused for 18 years. A Bayesian framework was used to select useful covariates and to estimate the model parameters. This framework was developed to deal with sources of uncertainty, including the complexity of the mortality process itself and the field data, especially historical data for which taxonomic determinations were uncertain. Uncertainty about the functional traits was also considered, to maximize the information they contain. Four functional traits were strong predictors of tree mortality: wood density, maximum height, laminar toughness and stem and branch orientation, which together distinguished the light-demanding, fast-growing trees from slow-growing trees with lower mortality rates. Our modelling approach formalizes a complex ecological problem and offers a relevant mathematical framework for tropical ecologists to process similar uncertain data at the community level. © 2013 Aubry-Kientz et al.
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Wagner, F., Rossi, V., Stahl, C., Bonal, D., & Herault, B. (2012). Water availability is the main climate driver of neotropical tree growth. PLoS ONE, 7(4), e34074.
Abstract: Climate models for the coming century predict rainfall reduction in the Amazonian region, including change in water availability for tropical rainforests. Here, we test the extent to which climate variables related to water regime, temperature and irradiance shape the growth trajectories of neotropical trees. We developed a diameter growth model explicitly designed to work with asynchronous climate and growth data. Growth trajectories of 205 individual trees from 54 neotropical species censused every 2 months over a 4-year period were used to rank 9 climate variables and find the best predictive model. About 9% of the individual variation in tree growth was imputable to the seasonal variation of climate. Relative extractable water was the main predictor and alone explained more than 60% of the climate effect on tree growth, i.e. 5.4% of the individual variation in tree growth. Furthermore, the global annual tree growth was more dependent on the diameter increment at the onset of the rain season than on the duration of dry season. The best predictive model included 3 climate variables: relative extractable water, minimum temperature and irradiance. The root mean squared error of prediction (0.035 mm.d -1) was slightly above the mean value of the growth (0.026 mm.d -1). Amongst climate variables, we highlight the predominant role of water availability in determining seasonal variation in tree growth of neotropical forest trees and the need to include these relationships in forest simulators to test, in silico, the impact of different climate scenarios on the future dynamics of the rainforest. © 2012 Wagner et al.
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Stahl, C., Burban, B., Wagner, F., Goret, J. - Y., Bompy, F., & Bonal, D. (2013). Influence of Seasonal Variations in Soil Water Availability on Gas Exchange of Tropical Canopy Trees. Biotropica, 45(2), 155–164.
Abstract: Seasonal variations in environmental conditions influence the functioning of the whole ecosystem of tropical rain forests, but as yet little is known about how such variations directly influence the leaf gas exchange and transpiration of individual canopy tree species. We examined the influence of seasonal variations in relative extractable water in the upper soil layers on predawn leaf water potential, saturated net photosynthesis, leaf dark respiration, stomatal conductance, and tree transpiration of 13 tropical rain forest canopy trees (eight species) over 2 yr in French Guiana. The canopies were accessed by climbing ropes attached to the trees and to a tower. Our results indicate that a small proportion of the studied trees were unaffected by soil water depletion during seasonal dry periods, probably thanks to efficient deep root systems. The trees showing decreased tree water status (i.e., predawn leaf water potential) displayed a wide range of leaf gas exchange responses. Some trees strongly regulated photosynthesis and transpiration when relative extractable water decreased drastically. In contrast, other trees showed little variation, thus indicating good adaptation to soil drought conditions. These results have important applications to modeling approaches: indeed, precise evaluation and grouping of these response patterns are required before any tree-based functional models can efficiently describe the response of tropical rain forest ecosystems to future changes in environmental conditions. © 2012 by The Association for Tropical Biology and Conservation.
Keywords: French Guiana; Photosynthesis; Predawn leaf water potential; Rain forest; Relative extractable water; Respiration; Soil drought; Transpiration
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Marcon, E., Scotti, I., Herault, B., Rossi, V., & Lang, G. (2014). Generalization of the partitioning of Shannon diversity. PLoS ONE, 9(3), e90289.
Abstract: Traditional measures of diversity, namely the number of species as well as Simpson's and Shannon's indices, are particular cases of Tsallis entropy. Entropy decomposition, i.e. decomposing gamma entropy into alpha and beta components, has been previously derived in the literature. We propose a generalization of the additive decomposition of Shannon entropy applied to Tsallis entropy. We obtain a self-contained definition of beta entropy as the information gain brought by the knowledge of each community composition. We propose a correction of the estimation bias allowing to estimate alpha, beta and gamma entropy from the data and eventually convert them into true diversity. We advocate additive decomposition in complement of multiplicative partitioning to allow robust estimation of biodiversity. © 2014 Marcon et al.
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Fanin, N., Hättenschwiler, S., Schimann, H., & Fromin, N. (2015). Interactive effects of C, N and P fertilization on soil microbial community structure and function in an Amazonian rain forest. Funct. Ecol., 29(1), 140–150.
Abstract: Resource control over abundance, structure and functional diversity of soil microbial communities is a key determinant of soil processes and related ecosystem functioning. Copiotrophic organisms tend to be found in environments which are rich in nutrients, particularly carbon, in contrast to oligotrophs, which survive in much lower carbon concentrations. We hypothesized that microbial biomass, activity and community structure in nutrient-poor soils of an Amazonian rain forest are limited by multiple elements in interaction. We tested this hypothesis with a fertilization experiment by adding C (as cellulose), N (as urea) and P (as phosphate) in all possible combinations to a total of 40 plots of an undisturbed tropical forest in French Guiana. After 2 years of fertilization, we measured a 47% higher biomass, a 21% increase in substrate-induced respiration rate and a 5-fold higher rate of decomposition of cellulose paper discs of soil microbial communities that grew in P-fertilized plots compared to plots without P fertilization. These responses were amplified with a simultaneous C fertilization suggesting P and C colimitation of soil micro-organisms at our study site. Moreover, P fertilization modified microbial community structure (PLFAs) to a more copiotrophic bacterial community indicated by a significant decrease in the Gram-positive : Gram-negative ratio. The Fungi : Bacteria ratio increased in N fertilized plots, suggesting that fungi are relatively more limited by N than bacteria. Changes in microbial community structure did not affect rates of general processes such as glucose mineralization and cellulose paper decomposition. In contrast, community level physiological profiles under P fertilization combined with either C or N fertilization or both differed strongly from all other treatments, indicating functionally different microbial communities. While P appears to be the most critical from the three major elements we manipulated, the strongest effects were observed in combination with either supplementary C or N addition in support of multiple element control on soil microbial functioning and community structure. We conclude that the soil microbial community in the studied tropical rain forest and the processes it drives is finely tuned by the relative availability in C, N and P. Any shifts in the relative abundance of these key elements may affect spatial and temporal heterogeneity in microbial community structure, their associated functions and the dynamics of C and nutrients in tropical ecosystems.
Keywords: Ecosystem functioning; Functional significance; Microbial community structure; Multiple resource limitation; Phospholipid fatty acids (PLFA); Phosphorus; Soil functioning; Tropical forest
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Nicolini, E., Beauchene, J., De La Vallee, B. L., Ruelle, J., Mangenet, T., & Heuret, P. (2012). Dating branch growth units in a tropical tree using morphological and anatomical markers: The case of Parkia velutina Benoist (Mimosoïdeae). Ann. Forest Sci., 69(5), 543–555.
Abstract: • Context In tropical areas, studies based on the retrospective analysis of tree development have focused principally on growth ring research. The interpretation of primary growth markers is overlooked although it opens perspectives to provide long time-series on tree-crown development. • Aims This study focused on Parkia velutina, an emergent tree of neotropical rain forests. Our objectives were (1) to characterize the phenological cycle of this species, and (2) to identify temporally interpretable morphological and anatomical markers. • Methods We collected dominant branches in 14 adult trees and identified growth markers that limit longitudinal and radial increments. We coupled this approach with a 2-year phenological survey of 20 trees. • Results Leaf shedding, growth unit elongation and growth ring formation define the phenological cycle. At tree scale, this cycle is synchronous and affects all axes. At population scale, trees can be desynchronized. This cycle is annual despite some slight variability. Successive growth units and growth rings are easily identifiable. • Conclusion Dating a branch by counting the number of growth units or growth rings is possible in many years with a reasonable error. Nevertheless, estimating their precise month of formation in order to study climatic influences remains difficult. © INRA/Springer-Verlag France 2012.
Keywords: Crown development; Deciduousness; Dendrochronology; French Guiana; Growth ring; Phenology; Tree architecture; Wood anatomy
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Scotti-Saintagne, C., Bodenes, C., Barreneche, T., Pot, D., Plomion, C., & Kremer, A. (2004). Distribution of genomic regions differentiating oak species assessed by QTL detection. Heredity, 92(1), 20–30.
Abstract: Pedunculate oak and sessile oak are two sympatric inter-fertile species that exhibit leaf morphological differences. We aimed to detect quantitative trait loci (QTLs) of these traits in order to locate genomic regions involved in species differentiation. A total of 15 leaf morphological traits were assessed in a mixed forest stand composed of Quercus petraea and Q. robur and in a full-sib pedigree of Q. robur. The progeny of the full-sib family were vegetatively propagated in two successive experiments comprising 174 and 216 sibs, and assessments were made on two leaves collected on each of the 1080 and 1530 cuttings corresponding to the two experiments. Traits that exhibited strong species differences in the mixed stand tended also to have higher repeatability values in the mapping population, thus indicating higher genetic control. A genetic map was constructed for QTL detection. Composite interval mapping with the one QTL model was used for QTL detection. From one to three QTLs were detected for 13 traits. In-depth analysis of the QTLs, controlling the five morphological traits that exhibited the highest interspecific differences in the mixed stand, indicated that they were distributed on six linkage groups, with two clusters comprising QTLs of at least two discriminant traits. These results were reinforced when error 1 for QTL detection was set at 5% at the chromosome level, as up to nine clusters could be identified. In conclusion, traits involved in interspecific differentiation of oaks are under polygenic control and widespread in clusters across the genome.
Keywords: QTL; leaf morphology; repeatability; genetic map; Q. robur
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