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Flores, O., Herault, B., Delcamp, M., Garnier, É., & Gourlet-Fleury, S. (2014). Functional traits help predict post-disturbance demography of tropical trees. PLoS ONE, 9(9), e105022.
Abstract: How tropical tree species respond to disturbance is a central issue of forest ecology, conservation and resource management. We define a hierarchical model to investigate how functional traits measured in control plots relate to the population change rate and to demographic rates for recruitment and mortality after disturbance by logging operations. Population change and demographic rates were quantified on a 12-year period after disturbance and related to seven functional traits measured in control plots. The model was calibrated using a Bayesian Network approach on 53 species surveyed in permanent forest plots (37.5 ha) at Paracou in French Guiana. The network analysis allowed us to highlight both direct and indirect relationships among predictive variables. Overall, 89% of interspecific variability in the population change rate after disturbance were explained by the two demographic rates, the recruitment rate being the most explicative variable. Three direct drivers explained 45% of the variability in recruitment rates, including leaf phosphorus concentration, with a positive effect, and seed size and wood density with negative effects. Mortality rates were explained by interspecific variability in maximum diameter only (25%). Wood density, leaf nitrogen concentration, maximum diameter and seed size were not explained by variables in the analysis and thus appear as independent drivers of post-disturbance demography. Relationships between functional traits and demographic parameters were consistent with results found in undisturbed forests. Functional traits measured in control conditions can thus help predict the fate of tropical tree species after disturbance. Indirect relationships also suggest how different processes interact to mediate species demographic response.
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Laurans, M., Martin, O., Nicolini, E., & Vincent, G. (2012). Functional traits and their plasticity predict tropical trees regeneration niche even among species with intermediate light requirements. J. Ecol., 100(6), 1440–1452.
Abstract: Niche differentiation is a key issue in the current debate on community assembly mechanisms. In highly diverse moist tropical forests, tree species sensitivity to canopy openness is thought to be a major axis in niche differentiation. In the past, the syndrome of traits driving the demographic trade-off involved in the niche-based theory of coexistence has always been established among species situated at the two extremities of the shade-tolerance gradient, even though most tropical tree species have intermediate light requirements. In addition, trait plasticity has seldom been linked to tropical tree species distribution along environmental gradients. This article examines covariations between leaf traits, whole-plant traits and niche parameters among 14 tree species with intermediate light requirements in French Guiana and across a range of canopy openness. Each functional trait measured under field conditions was characterized by a median value and a degree of plasticity expressed under contrasting light regimes. Niche differentiation was characterized in terms of spatial light gradient. We first examined covariations between functional traits then explored to what degree the median value and plasticity in functional traits could predict light niche characteristics at the sapling stage and the ontogenetic change in light availability estimated by adult stature. Leaf mass per area (LMA) was positively correlated with leaf life span (LLS); species with higher LMA and higher LLS displayed lower diameter growth rates (GRs) and lower responsiveness to canopy gap at both whole-plant and population levels. This proved that the relationships previously established over a broader range of species held true within the narrow range of the light requirements covered. Height GR plasticity accounted for 49% of the variation in light niche optimum. LMA plasticity, unlike LLS plasticity, was significantly correlated with light niche breadth and adult stature. Synthesis. This study demonstrates the relevance of considering the phenotypic plasticity in functional traits in community ecology, particularly for quantifying breadth of species distribution over environmental gradients. Our findings did not support Hubbell's hypothesis of functional equivalence and suggest that even a rather subtle variation in forest canopy disturbance promotes the coexistence of tropical tree species. © 2012 The Authors. Journal of Ecology © 2012 British Ecological Society.
Keywords: Canopy disturbance; Determinants of plant community diversity and structure; Growth rate; Irradiance; Leaf life span; Leaf mass per area; Niche differentiation; Phenotypic plasticity; Shade tolerance; Tropical moist forest
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Marcon, E., Puech, F., & Traissac, S. (2012). Characterizing the relative spatial structure of point patterns. Int. J. Ecol., 2012(Article ID 619281), 11.
Abstract: We generalize Ripley's K function to get a new function, M, to characterize the spatial structure of a point pattern relatively to another one. We show that this new approach is pertinent in ecology when space is not homogenous and the size of objects matters. We present how to use the function and test the data against the null hypothesis of independence between points. In a tropical tree data set we detect intraspecific aggregation and interspecific competition. © 2012 Eric Marcon et al.
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Ogeron, C., Odonne, G., Cristinoi, A., Engel, J., Grenand, P., Beauchene, J., et al. (2018). Palikur traditional roundwood construction in eastern French Guiana: Ethnobotanical and cultural perspectives. Journal of Ethnobiology and Ethnomedicine, 14(28).
Abstract: Background: Palikur Amerindians live in the eastern part of French Guiana which is undergoing deep-seated changes due to the geographical and economic opening of the region. So far, Palikur's traditional ecological knowledge is poorly documented, apart from medicinal plants. The aim of this study was to document ethnobotanical practices related to traditional construction in the region. Methods: A combination of qualitative and quantitative methods was used. Thirty-nine Palikur men were interviewed in three localities (Saint-Georges de l'Oyapock, Regina and Trois-Palétuviers) between December 2013 and July 2014. Twenty-four inventories of wood species used in traditional buildings were conducted in the villages, as well as ethnobotanical walks in the neighboring forests, to complete data about usable species and to determine Linnaean names. Results: After an ethnographic description of roundwood Palikur habitat, the in situ wood selection process of Palikur is precisely described. A total of 960 roundwood pieces were inventoried in situ according to Palikur taxonomy, of which 860 were beams and rafters, and 100 posts in 20 permanent and 4 temporary buildings. Twenty-seven folk species were identified. Sixty-three folk species used in construction were recorded during ethnobotanical walks. They correspond to 263 botanical species belonging to 25 families. Posts in permanent buildings were made of yawu (Minquartia guianensis) (51%) and wakap (Vouacapoua americana) (14%). Beams and rafters were made of wood from Annonaceae (79%) and Lecythidaceae (13%) families. The most frequently used species were kuukumwi priye (Oxandra asbeckii), kuukumwi seyne (Pseudoxandra cuspidata), and pukuu (Xylopia nitida and X. cayennensis). Conclusions: Although the Palikur's relationship with their habitat is undergoing significant changes, knowledge about construction wood is still very much alive in the Oyapock basin. Many people continue to construct traditional buildings alongside modern houses, using a wide array of species described here for the first time, along with the techniques used.
Keywords: Amazonia; Annonaceae; Architecture; Non-timber forest products; Oyapock; Palikur; Sapotaceae; Traditional technological knowledge
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Petit, M., Denis, T., Rux, O., Richard-Hansen, C., & Berzins, R. (2018). Estimating jaguar (Panthera onca) density in a preserved coastal area of French Guiana. Mammalia, 82(2), 188–192.
Abstract: Knowledge of the jaguar population is needed in French Guiana that faces an increase of human-jaguar conflicts. We carried out a camera trap survey to assess jaguar local density and home range size in a preserved coastal area of French Guiana. We ran spatially explicit capture recapture (SECR) models. In our model, the scale parameter σ, that is linked to the home range size, was larger for males (σ=3.87±0.59 SE km) than for females (σ=2.33±0.30 SE km). The assessed jaguar density was 3.22±0.87 SE ind. 100 km â '2, which should be considered as an optimal density in a French Guiana coastal area.
Keywords: camera trapping; density; French Guiana; home range; Panthera onca; spatially explicit capture recapture
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Leitão, R. P., Zuanon, J., Villéger, S., Williams, S. E., Baraloto, C., Fortunel, C., et al. (2016). Rare species contribute disproportionately to the functional structure of species assemblages. Proceedings of the Royal Society B: Biological Sciences, 283(1828).
Abstract: There is broad consensus that the diversity of functional traits within species assemblages drives several ecological processes. It is also widely recognized that rare species are the first to become extinct following human-induced disturbances. Surprisingly, however, the functional importance of rare species is still poorly understood, particularly in tropical species-rich assemblages where the majority of species are rare, and the rate of species extinction can be high. Here, we investigated the consequences of local and regional extinctions on the functional structure of species assemblages. We used three extensive datasets (stream fish from the Brazilian Amazon, rainforest trees from French Guiana, and birds from the Australian Wet Tropics) and built an integrative measure of species rarity versuscommonness, combining local abundance, geographical range, andhabitat breadth. Using different scenarios of species loss, we found a disproportionate impact of rare species extinction for the three groups, with significant reductions in levels of functional richness, specialization, and originality of assemblages, which may severely undermine the integrity of ecological processes. The whole breadth of functional abilities within species assemblages, which is disproportionately supported by rare species, is certainly critical in maintaining ecosystems particularly under the ongoing rapid environmental transitions. © 2016 The Author(s) Published by the Royal Society. All rights reserved.
Keywords: Conservation; Extinction; Functional diversity; Null models; Rarity index; Tropical biodiversity
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Scotti, I., González-Martínez, S. C., Budde, K. B., & Lalague, H. (2016). Fifty years of genetic studies: what to make of the large amounts of variation found within populations? Annals of Forest Science, 73(1), 69–75.
Keywords: Intra-specific variation; Microgeography; Natural selection; Population genomics
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Thibaut, B., Denaud, L., Collet, R., Marchal, R., Beauchene, J., Mothe, F., et al. (2016). Wood machining with a focus on French research in the last 50 years. Annals of Forest Science, 73(1), 163–184.
Abstract: Key message: Wood machining is compulsory both for timber separation and the surfacing of wooden objects. The anisotropy, cellular nature and multi-scale level organisation of wood make its cutting complicated to study. During the last 50 years, most of the wood machining subjects were covered by French teams. Context: Woodcutting is a very old technology but scientific research is scarce on the subject. In the last 50 years, much work on basic mechanisms as well as on industrial processes has been done in France. Aims: The specific nature of wood introduces strong differences between wood and metal cutting processes. The paper focuses on French teams’ contributions. Results: The basic aspects of the tool–material interaction for different basic modes in woodcutting are highlighted. In primary conversion such as sawing, veneer cutting or green wood chipping, huge progress comes from automation and the possibility of linking the process to log and product quality through new sensors. In secondary processing, much has been done on the links between the cutting process, surface qualification and the properties of these surfaces for further processing, such as gluing or coating. Tool wear depends on the cutting process, timber quality and species. Trade-offs are required in tool technology and coating technologies may improve tool life. Conclusion: A large amount of knowledge and innovation has come from 50 years of worldwide research effort, with France being particularly active in this period. The transfer of skills from metals cutting industry was often a key, but much is needed to move closer to both metal cutting sector and woodcutting skills among craftsmen. © 2015, INRA and Springer-Verlag France.
Keywords: Primary conversion; Secondary processing; Surface quality; Tool wear
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Bonal, D., Burban, B., Stahl, C., Wagner, F., & Herault, B. (2016). The response of tropical rainforests to drought—lessons from recent research and future prospects. Annals of Forest Science, 73(1), 27–44.
Abstract: Key message: We review the recent findings on the influence of drought on tree mortality, growth or ecosystem functioning in tropical rainforests. Drought plays a major role in shaping tropical rainforests and the response mechanisms are highly diverse and complex. The numerous gaps identified here require the international scientific community to combine efforts in order to conduct comprehensive studies in tropical rainforests on the three continents. These results are essential to simulate the future of these ecosystems under diverse climate scenarios and to predict the future of the global earth carbon balance. Context: Tropical rainforest ecosystems are characterized by high annual rainfall. Nevertheless, rainfall regularly fluctuates during the year and seasonal soil droughts do occur. Over the past decades, a number of extreme droughts have hit tropical rainforests, not only in Amazonia but also in Asia and Africa. The influence of drought events on tree mortality and growth or on ecosystem functioning (carbon and water fluxes) in tropical rainforest ecosystems has been studied intensively, but the response mechanisms are complex. Aims: Herein, we review the recent findings related to the response of tropical forest ecosystems to seasonal and extreme droughts and the current knowledge about the future of these ecosystems. Results: This review emphasizes the progress made over recent years and the importance of the studies conducted under extreme drought conditions or in through-fall exclusion experiments in understanding the response of these ecosystems. It also points to the great diversity and complexity of the response of tropical rainforest ecosystems to drought. Conclusion: The numerous gaps identified here require the international scientific community to combine efforts in order to conduct comprehensive studies in tropical forest regions. These results are essential to simulate the future of these ecosystems under diverse climate scenarios and to predict the future of the global earth carbon balance. © 2015, INRA and Springer-Verlag France.
Keywords: Carbon; Climate; Drought; Global change; Growth; Mortality; Soil; Tropical; Water
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Amusant, N., Digeon, A., Descroix, L., Bruneau, O., Bezard, V., & Beauchene, J. (2015). Planting rosewood for sustainable essential oil production: Influence of surrounding forest and seed provenance on tree growth and essential oil yields. Bois et Forets des Tropiques, 326(4), 57–65.
Abstract: Essential oil from the Amazonian rosewood tree (Aniba rosaeodora Ducke) is valued as an important aromatic ingredient in luxury perfumes. Due to over-harvesting in recent decades, rosewood is now listed as an endangered species. Rosewood tree planting is now considered a viable alternative to logging as it can support both reforestation and sustainable agriculture thanks to sales of the essential oil extracted. We planted 605 rosewood trees in French Guiana from two seeds of local provenance, in a 5 445 m2 plot surrounded by primary forest. Nine years after planting, we assessed the effect of the position of the tree relative to the surrounding forest and of the seed provenance on dendrometric traits (height, circumference, above ground woody biomass) and hence on the yield of essential oil. Measurements were made on 99 trees. Average growth rates for the young trees were 0.7 m/year in height, 2.5 cm/year in stem circumference and 990.5 kg dry mass/ha/year in aboveground biomass, while essential oil yields ranged from 0.6% to 3.6% with a mean of 2.1%. The position of the tree relative to the surrounding forest was the main factor affecting tree growth and essential oil production: trees located close to the surrounding forest were significantly smaller and accumulated less essential oil due to the reduced availability of light. Seed provenance had less effect on dendrometric traits and essential oil yields. In conclusion, although planting practices will need to be adapted to avoid the edge effects of proximity to the forest, short-rotation cultivation of rosewood trees could be the optimum and most economically attractive system for the production of essential oil.
Keywords: Aniba rosaeodora Ducke; Dendrometric traits; Essential oil yield; French Guiana; Light effect; Plantation; Rosewood; Seed provenance
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