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Cabanillas, B. J., Le Lamer, A. C., Castillo, D., Arevalo, J., Rojas, R., Odonne, G., et al. (2010). Caffeic Acid Esters and Lignans from Piper sanguineispicum. J. Nat. Prod., 73(11), 1884–1890.
Abstract: Three new caffeic acid esters (1-3), four new lignans (4-7), and the known compounds (7'S)-parabenzlactone (8), dihydrocubebin (9), and justiflorinol (10) have been isolated from leaves of Piper sanguineispicum. Their structures were determined by spectroscopic methods, including 1D and 2D NMR, HRCIMS, CD experiments, and chemical methods. Compounds 1-10 were assessed for their antileishmanial potential against axenic amastigote forms of Leishmania amazonensis. Caffeic acid esters 1 and 3 exhibited the best antileishmanial activity (IC50 2.0 and 1.8 μM, respectively) with moderate cytotoxicity on murine macrophages.
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Stahl, C., Herault, B., Rossi, V., Burban, B., Bréchet, C., & Bonal, D. (2013). Depth of soil water uptake by tropical rainforest trees during dry periods: Does tree dimension matter? Oecologia, 173(4), 1191–1201.
Abstract: Though the root biomass of tropical rainforest trees is concentrated in the upper soil layers, soil water uptake by deep roots has been shown to contribute to tree transpiration. A precise evaluation of the relationship between tree dimensions and depth of water uptake would be useful in tree-based modelling approaches designed to anticipate the response of tropical rainforest ecosystems to future changes in environmental conditions. We used an innovative dual-isotope labelling approach (deuterium in surface soil and oxygen at 120-cm depth) coupled with a modelling approach to investigate the role of tree dimensions in soil water uptake in a tropical rainforest exposed to seasonal drought. We studied 65 trees of varying diameter and height and with a wide range of predawn leaf water potential (Ψpd) values. We confirmed that about half of the studied trees relied on soil water below 100-cm depth during dry periods. Ψpd was negatively correlated with depth of water extraction and can be taken as a rough proxy of this depth. Some trees showed considerable plasticity in their depth of water uptake, exhibiting an efficient adaptive strategy for water and nutrient resource acquisition. We did not find a strong relationship between tree dimensions and depth of water uptake. While tall trees preferentially extract water from layers below 100-cm depth, shorter trees show broad variations in mean depth of water uptake. This precludes the use of tree dimensions to parameterize functional models. © 2013 Springer-Verlag Berlin Heidelberg.
Keywords: Deuterium; Oxygen; Root; Soil water; Tropical rainforest
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Paine, C. E. T., & Harms, K. E. (2009). Quantifying the effects of seed arrival and environmental conditions on tropical seedling community structure. Oecologia, 160(1), 139–150.
Abstract: Though it is recognized that both stochastic and deterministic processes structure all communities, empirical assessments of their relative importance are rare, particularly within any single community. In this paper, we quantify the dynamic effects of dispersal assembly and niche assembly on the seedling layer in a diverse neotropical rain forest. The two theories make divergent predictions regarding the roles of seed arrival and environmental heterogeneity in generating community structure. Put simply, dispersal assembly posits that the stochasticity inherent to seed arrival structures communities, whereas niche assembly suggests that heterogeneity in post-dispersal environmental conditions is more important. We experimentally sowed 15,132 seeds of eight tree species at varying levels of density and diversity. Every six months we censused the seedlings that germinated and assessed the abiotic and biotic conditions of each plot. We assessed the density, diversity, and species composition of three nested subsets of the seedling layer: seedlings germinated from sown seeds, all seedlings germinated between July 2003 and 2004, and all woody seedlings. We partitioned the variance in density and diversity of each subset of the seedling layer into components representing seed-addition treatments and environmental conditions at 6- to 12-month intervals. Seed additions initially explained more variance in the density and diversity than did environmental heterogeneity for seven of eight sown species, but explained little variance in the density or diversity of the entire seedling layer. Species composition was better explained by seed-addition treatments than by environmental heterogeneity for all three subsets and in all time periods. Nevertheless, the variance in community structure explained by seed-addition treatments declined over the two years following germination, presaging shifts in the relative importance of dispersal assembly and niche assembly. Our study quantifies how dispersal assembly and niche assembly may vary among the components of an ecological community and shift dynamically through time.
Keywords: Community assembly; Dispersal; Niche differentiation; Seed addition; Variance partitioning
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de Grandcourt, A., Epron, D., Montpied, P., Louisanna, E., Bereau, M., Garbaye, J., et al. (2004). Contrasting responses to mycorrhizal inoculation and phosphorus availability in seedlings of two tropical rainforest tree species. New Phytol., 161(3), 865–875.
Abstract: This work aimed at understanding the role of mycorrhizal status in phosphorus efficiency of tree seedlings in the tropical rainforest of French Guyana. Mycorrhizal colonization, growth, phosphorus content, net photosynthesis and root respiration were determined on three occasions during a 9-month growth period for seedlings of two co-occurring species (Dicorynia guianensis and Eperua falcata) grown at three soil phosphorus concentrations, with or without inoculation with arbuscular mycorrhizas. Seedlings of both species were unable to absorb phosphorus in the absence of mycorrhizal association. Mycorrhizal seedlings exhibited coils that are specific of Paris-type mycorrhizae. Both species benefited from the mycorrhizal symbiosis in terms of phosphorus acquisition but the growth of E. falcata seedlings was unresponsive to this mycorrhizal improvement of phosphorus status, probably because of the combination of high seed mass and P reserves, with low growth rate. The two species belong to two different functional groups regarding phosphorus acquisition, D. guianensis being an obligate mycotrophic species.
Keywords: phosphorus; growth; efficiency; Paris-type arbuscular mycorrhizas; tropical rainforest; seedlings; Dicorynia guianensis; Eperua falcata
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Wagner, F., Rutishauser, E., Blanc, L., & Herault, B. (2010). Effects of Plot Size and Census Interval on Descriptors of Forest Structure and Dynamics. Biotropica, 42(6), 664–671.
Abstract: This study was designed to explicitly formulate the effect of census interval and plot size on the variability of descriptors of tropical forest structure (stand density, basal area, aboveground biomass [AGB]) and dynamic (tree growth, mortality and recruitment rates, biomass fluxes). A unique dataset from a broad plot network (37.5 ha) surveyed every 2 yr over a 16-yr period was used to develop and parameterize a new statistical model predicting the coefficients of variation for each forest descriptor. More than 90 percent of the inherent variability of these coefficients was predicted using a simple model including plot size and census interval in a Bayesian modeling framework. All descriptors of forest structure varied by <10 percent for plot sizes 42 ha. Among the descriptors of forest dynamics, AGB loss was the most variable. The number of 6.25 ha plots required to estimate its mean, over a 16-yr period, within a 20 percent error of the mean remains above four. This contrasts with a relative constant flux of biomass entering the plot through tree growth and tree recruitment. Tree growth was remarkably well estimated with <15 percent variability for a 2-yr census in a plot of 2 ha. This study provides an easy method to assess dataset limitations in efforts to estimate descriptors of forest structure and dynamic, which is of primary importance to decipher any clear consequences of global change in tropical forests.
Keywords: Amazonia; biomass fluxes; coefficient of variation; forest permanent plots; turnover rates; WinBUGS
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McClure, M., Chouteau, M., & Dejean, A. (2008). Territorial aggressiveness on the arboreal ant Azteca alfari by Camponotus blandus in French Guiana due to behavioural constraints. C. R. Biol., 331(9), 663–667.
Abstract: This study reports new information on interactions between two sympatric ant species, the plant-ant Azteca alfari (Dolichoderinae) living in association with the myrmecophyte Cecropia obtusa (Cecropiaceae) and Camponotus blandus (Formicinae), a ground-nesting, arboreal-foraging species. Workers of A. alfari forage only on the foliage and the tipper parts of the trunk of their host Cecropia, while C. blandus nests in the ground but frequently forages and patrols pioneer tree foliage, including Cecropia. The activity pattern of A. alfari and the number of C. blandus on Cecropia obtusa was monitored hourly during a two-day period in a disturbed area in French Guiana. The maximum activity of C. blandus occurred between 8:30 and 12:30, at which time A. alfari had retreated within the domatia and were least present on the trunks. Even though aggressive confrontations were observed, C. blandus workers often initiate confrontations but do not prey on A. alfari nor exploit food bodies produced by Cecropia, the principal food source of A. alfari. Hence hostility appears to be the result of territoriality. Differences in their foraging rhythms are proposed as promoting resource and territory partitioning in this ant assemblage.
Keywords: Azteca alfari (Dolichoderinae); Camponotus blandus (Formicinae); foraging; rhythm of activity; territorial aggressiveness
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Roggy, J. C., Nicolini, E., Imbert, P., Caraglio, Y., Bosc, A., & Heuret, P. (2005). Links between tree structure and functional leaf traits in the tropical forest tree Dicorynia guianensis Amshoff (Caesalpiniaceae). Ann. For. Sci., 62(6), 553–564.
Abstract: This study looked at the interactive effects of tree architectural stage of development (ASD) and light availability on different plant traits (growth parameters, leaf morpho-anatomy and photosynthetic capacities) in the tropical species Dicorynia guianensis. A qualitative architectural analysis was used to categorize tree individuals sampled along a natural light gradient. The results show that some traits could have an ASD-dependence at the whole plant and leaf level without control of light. The changes observed relate to vigour thresholds the plant has to reach to shift from one ASD to another (i.e., the number of nodes and the internodes length per Growth Unit). Light conditions do not modify these thresholds but may modify the time they are crossed. Tree height was found strongly modulated by light conditions; hence, at a similar height, individuals may belong to different ASD. At the functional level, a decrease in N-m, and A(maxm) was observed with increasing light availability, while N-a increased and A(maxa) remained unaffected. An ASD effect was also observed on Amaxa and LMA but not on Amaxm. These results demonstrated a weak ability of photosynthetic plasticity in response to light conditions, and that variations of leaf photosynthetic variables according to ASD can be explained by modifications in leaf nitrogen and LMA. Questions on the reliability of a height-based sampling strategy for evaluating the phenotypic plasticity of trees in relation to light conditions are raised.
Keywords: Dicorynia guianensis; leaf structure; functional leaf traits; plasticity; tree structure
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Gond, V., & Guitet, S. (2009). Remote Sensing in Post-Logging Diagnoses for Forest Management in French Guiana. Bois For. Trop., 63(299), 5–13.
Abstract: This study is part of the activities carried out to monitor tow-impact logging operations in humid tropical forests. The sustainability of these activities is highly dependent on the scale of logging damage, and managers therefore need to carry out effective checks on the quality of forestry work. In this study, remote sensing was used to track the extension of logging operations and to assess damage, through images acquired during and after logging in each parcel. Analysis of the high-resolution images (10 m) clearly identifies logged-over clearings and some skidding tracks, allowing assessments of gaps opening up in the canopy. Several parcels were monitored in this French Guiana study. A simple diagnostic procedure was established for each parcel to assess logging intensity and identify new logging tracks and timber losses. The remote sensing toot thus helps to make more accurate assessments of logging quality and to draw relevant conclusions for the logging company. The study has demonstrated the usefulness of remote sensing to identify damage after logging. The quality of restitution of the damage was validated by means of a database on the logging terrain and through field missions. This post-logging inspection tool can now be automated for fully operational use by forest managers.
Keywords: selective logging; logging impact inspections; French Guiana; remote sensing; forest management
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Khia, A., Ghanmi, M., Satrani, B., Aafi, A., Aberchane, M., Quaboul, B., et al. (2014). Effect of provenance on the chemical and microbiological quality of essential oils of Rosmarinus officinalis L. in Morocco. Phytotherapie, 12(6), 341–347.
Abstract: This study is an assessment of the chemical quality and evaluation of antibacterial and antifungal activity of rosemary’s essential oils from three regions of Morocco (Rchida and Berkine/Eastern Morocco and Aknoul/North East of Morocco. The essential oils obtained by hydrodistillation of the leaves and young twigs of rosemary, were analyzed by GC / FID and GC/ MS. These essential oils are characterized by the presence of α and β-pinene, camphene, 1,8-cineole and camphor compounds. The quality of these essential oils met the AFNOR NF ISO 4730 rosemary Morocco kind (1,8-cineole). The evaluation of the antimicrobial activity of essential oils of Rosmarinus officinalis showed low efficacy against microorganisms tested which were all inhibited from 1/100 v/v except for Penicillium expansum whose growth was stopped at the concentration 1/250 v/v.
Keywords: Antibacterial; Antifungal activity; Chemical composition; Essential Oil; Provenance; Rosmarinus officinalis
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Lamarre, G. P. A., Decaëns, T., Rougerie, R., Barbut, J., Dewaard, J. R., Hebert, P. D. N., et al. (2016). An integrative taxonomy approach unveils unknown and threatened moth species in Amazonian rainforest fragments. Insect Conserv Divers, 9(5), 475–479.
Abstract: This study focuses on the importance in hyperdiverse regions, such as the Amazonian forest, of accelerating and optimising the census of invertebrate communities.
We carried out low-intensity sampling of tropical moth (Lepidoptera) assemblages in disturbed forest fragments in Brazil.
We combined DNA barcoding and taxonomists’ expertise to produce fast and accurate surveys of local diversity, including the recognition and census of undescribed and endemic species.
Integrating expert knowledge of species distributions, we show that despite limited sampling effort, our approach revealed an unexpectedly high number of new and endemic species in severely threatened tropical forest fragments.
These results highlight the risk of silent centinelan extinctions and emphasise the urgent need for accelerated invertebrate surveys in high-endemism and human-impacted tropical forests.
Keywords: Amazonian forest; Belém center of endemism; centinelan extinction; conservation; DNA barcoding; Lepidoptera; species discovery
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