Home | [21–30] << 31 32 33 34 35 36 37 38 39 40 >> [41–50] |
Fu, Z., Gerken, T., Bromley, G., Araújo, A., Bonal, D., Burban, B., et al. (2018). The surface-atmosphere exchange of carbon dioxide in tropical rainforests: Sensitivity to environmental drivers and flux measurement methodology. Agric. For. Meterol., 263, 292–307.
Abstract: Tropical rainforests play a central role in the Earth system by regulating climate, maintaining biodiversity, and sequestering carbon. They are under threat by direct anthropogenic impacts like deforestation and the indirect anthropogenic impacts of climate change. A synthesis of the factors that determine the net ecosystem exchange of carbon dioxide (NEE) at the site scale across different forests in the tropical rainforest biome has not been undertaken to date. Here, we study NEE and its components, gross ecosystem productivity (GEP) and ecosystem respiration (RE), across thirteen natural and managed forests within the tropical rainforest biome with 63 total site-years of eddy covariance data. Our results reveal that the five ecosystems with the largest annual gross carbon uptake by photosynthesis (i.e. GEP > 3000 g C m−2 y-1) have the lowest net carbon uptake – or even carbon losses – versus other study ecosystems because RE is of a similar magnitude. Sites that provided subcanopy CO2 storage observations had higher average magnitudes of GEP and RE and lower average magnitudes of NEE, highlighting the importance of measurement methodology for understanding carbon dynamics in ecosystems with characteristically tall and dense vegetation. A path analysis revealed that vapor pressure deficit (VPD) played a greater role than soil moisture or air temperature in constraining GEP under light saturated conditions across most study sites, but to differing degrees from -0.31 to -0.87 μmol CO2 m−2 s-1 hPa-1. Climate projections from 13 general circulation models (CMIP5) under the representative concentration pathway that generates 8.5 W m−2 of radiative forcing suggest that many current tropical rainforest sites on the lower end of the current temperature range are likely to reach a climate space similar to present-day warmer sites by the year 2050, warmer sites will reach a climate not currently experienced, and all forests are likely to experience higher VPD. Results demonstrate the need to quantify if and how mature tropical trees acclimate to heat and water stress, and to further develop flux-partitioning and gap-filling algorithms for defensible estimates of carbon exchange in tropical rainforests. © 2018 Elsevier B.V.
Keywords: Climate variability; Ecosystem respiration; Eddy covariance; Gross primary productivity; Net ecosystem carbon dioxide exchange; Tropical rainforest; acclimation; air temperature; anthropogenic effect; atmosphere-biosphere interaction; biodiversity; carbon flux; climate change; Cmip; eddy covariance; environmental change; flux measurement; methodology; net ecosystem exchange; net ecosystem production; radiative forcing; rainforest; sensitivity analysis; tropical environment
|
Zalamea, P. C., Munoz, F., Stevenson, P. R., Paine, C. E. T., Sarmiento, C., Sabatier, D., et al. (2011). Continental-scale patterns of Cecropia reproductive phenology: evidence from herbarium specimens. Proc. R. Soc. B-Biol. Sci., 278(1717), 2437–2445.
Abstract: Plant phenology is concerned with the timing of recurring biological events. Though phenology has traditionally been studied using intensive surveys of a local flora, results from such surveys are difficult to generalize to broader spatial scales. In this study, contrastingly, we assembled a continental-scale dataset of herbarium specimens for the emblematic genus of Neotropical pioneer trees, Cecropia, and applied Fourier spectral and cospectral analyses to investigate the reproductive phenology of 35 species. We detected significant annual, sub-annual and continuous patterns, and discuss the variation in patterns within and among climatic regions. Although previous studies have suggested that pioneer species generally produce flowers continually throughout the year, we found that at least one third of Cecropia species are characterized by clear annual flowering behaviour. We further investigated the relationships between phenology and climate seasonality, showing strong associations between phenology and seasonal variations in precipitation and temperature. We also verified our results against field survey data gathered from the literature. Our findings indicate that herbarium material is a reliable resource for use in the investigation of large-scale patterns in plant phenology, offering a promising complement to local intensive field studies.
Keywords: climate seasonality; reproductive patterns; Fourier spectral and cospectral analyses; herbarium collections; Neotropics; pioneer plants
|
Fargeon, H., Aubry-Kientz, M., Brunaux, O., Descroix, L., Gaspard, R., Guitet, S., et al. (2016). Vulnerability of commercial tree species to water stress in logged forests of the Guiana shield. Forests, 7(5).
Abstract: The future of tropical managed forests is threatened by climate change. In anticipation of the increase in the frequency of drought episodes predicted by climatic models for intertropical regions, it is essential to study commercial trees' resilience and vulnerability to water stress by identifying potential interaction effects between selective logging and stress due to a lack of water. Focusing on 14 species representing a potential or acknowledged commercial interest for wood production in the Guiana Shield, a joint model coupling growth and mortality for each species was parametrized, including a climatic variable related to water stress and the quantity of aboveground biomass lost after logging. For the vast majority of the species, water stress had a negative impact on growth rate, while the impact of logging was positive. The opposite results were observed for the mortality. Combining results from growth and mortality models, we generate vulnerability profiles and ranking from species apparently quite resistant to water stress (Chrysophyllum spp., Goupia glabra Aubl., Qualea rosea Aubl.), even under logging pressure, to highly vulnerable species (Sterculia spp.). In light of our results, forest managers in the Guiana Shield may want to conduct (i) a conservation strategy of the most vulnerable species and (ii) a diversification of the logged species. Conservation of the already-adapted species may also be considered as the most certain way to protect the tropical forests under future climates. © 2016 by the authors.
Keywords: Climate change; Growth rates; Mortality rates; Paracou; Selective logging
|
Céréghino, R., Françoise, L., Bonhomme, C., Carrias, J. - F., Compin, A., Corbara, B., et al. (2020). Desiccation resistance traits predict freshwater invertebrate survival and community response to drought scenarios in a Neotropical ecosystem. Ecol. Indic., 119(106839).
Abstract: The intensification of dry seasons is a major threat to freshwater biodiversity in Neotropical regions. Little is known about resistance to drying stress and the underpinning traits in Neotropical freshwater species, so we don't know whether desiccation resistance allows to anticipate shifts in biological diversity under future climate scenarios. Here, we used the aquatic invertebrates that live in the rainwater-filled leaves of tank bromeliads, to examine the extent to which desiccation resistance of species measured in the laboratory predicts community response to drought intensification in nature. We measured desiccation resistance in 17 invertebrate species (>90% of the biomass usually found in bromeliads of French Guiana) by recording the median lethal time (LT50) of experimental populations exposed to controlled conditions of residual moisture. In the field, we placed rainshelters above tank bromeliads to emulate drought scenarios ranging from the ambient norm to IPCC scenarios and extreme events, and we recorded the response of functional community structure. LT50 ranged from 4.18 to 19.06 days, and was related to cuticle content and dry body mass. Among other functional indicators that represent strategies to optimize resource use under stressful conditions (e.g., habitat use, trophic specialization), LT50 was the best predictor of community structure responses along a gradient of emulated drought intensities. Therefore, species’ LT50s measured under laboratory conditions can be used to forecast aquatic community response to drying stress in nature. Anticipating how species will cope with drought has never been more important for environmental managers to support climate change adaptation. We show that desiccation resistance in freshwater invertebrates is a key indicator of potential population size and local–global range shifts, and this could be especially true in the Neotropics where species have narrow physiological tolerances for climatic variation. © 2020 Elsevier Ltd
Keywords: Climate change; Functional traits; Lt50; Macroinvertebrates; Rainforests; Biodiversity; Climate change; Driers (materials); Drought; Environmental management; Population statistics; Tanks (containers); Water; Aquatic invertebrates; Climate change adaptation; Controlled conditions; Environmental managers; Freshwater biodiversity; Freshwater invertebrates; Future climate scenarios; Laboratory conditions; Aquatic organisms; aquatic community; biodiversity; climate change; cuticle; desiccation; drought stress; invertebrate; Neotropical Region; population size; survival; French Guiana; Invertebrata
|
Maréchaux, I., Bartlett, M. K., Sack, L., Baraloto, C., Engel, J., Joetzjer, E., et al. (2015). Drought tolerance as predicted by leaf water potential at turgor loss point varies strongly across species within an Amazonian forest. Functional Ecology, 29(10), 1268–1277.
Abstract: Amazonian droughts are predicted to become increasingly frequent and intense, and the vulnerability of Amazonian trees has become increasingly documented. However, little is known about the physiological mechanisms and the diversity of drought tolerance of tropical trees due to the lack of quantitative measurements. Leaf water potential at wilting or turgor loss point (π<inf>tlp</inf>) is a determinant of the tolerance of leaves to drought stress and contributes to plant-level physiological drought tolerance. Recently, it has been demonstrated that leaf osmotic water potential at full hydration (π<inf>o</inf>) is tightly correlated with π<inf>tlp</inf>. Estimating π<inf>tlp</inf> from osmometer measurements of π<inf>o</inf> is much faster than the standard pressure-volume curve approach of π<inf>tlp</inf> determination. We used this technique to estimate π<inf>tlp</inf> for 165 trees of 71 species, at three sites within forests in French Guiana. Our data set represents a significant increase in available data for this trait for tropical tree species. Tropical trees showed a wider range of drought tolerance than previously found in the literature, π<inf>tlp</inf> ranging from -1·4 to -3·2 MPa. This range likely corresponds in part to adaptation and acclimation to occasionally extreme droughts during the dry season. Leaf-level drought tolerance varied across species, in agreement with the available published observations of species variation in drought-induced mortality. On average, species with a more negative π<inf>tlp</inf> (i.e. with greater leaf-level drought tolerance) occurred less frequently across the region than drought-sensitive species. Across individuals, π<inf>tlp</inf> correlated positively but weakly with leaf toughness (R2 = 0·22, P = 0·04) and leaf thickness (R2 = 0·03, P = 0·03). No correlation was detected with other functional traits (leaf mass per area, leaf area, nitrogen or carbon concentrations, carbon isotope ratio, sapwood density or bark thickness). The variability in π<inf>tlp</inf> among species indicates a potential for highly diverse species responses to drought within given forest communities. Given the weak correlations between π<inf>tlp</inf> and traditionally measured plant functional traits, vegetation models seeking to predict forest response to drought should integrate improved quantification of comparative drought tolerance among tree species. © 2015 British Ecological Society.
Keywords: Climate change; French Guiana; Functional traits; Plant-water relations; Tropical trees; Wilting
|
Le Lann, C., Roux, O., Serain, N., Van Alphen, J. J. M., Vernon, P., & Van Baaren, J. (2011). Thermal tolerance of sympatric hymenopteran parasitoid species: does it match seasonal activity? Physiol. Entomol., 36(1), 21–28.
Abstract: Climatic changes result in an increased in mean temperature and in a higher incidence of extreme weather events such as heat and cold waves. For ectotherms, such as insect parasitoids, the ability to remain active under extreme climatic conditions is a significant key to fitness. The body size of individuals, and in particular their surface to volume ratio, may play a role in their resistance to thermal conditions. The thermal tolerances are investigated of two closely-related sympatric parasitoid species [Aphidius avenae Haliday and Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Aphidiinae)] that have a similar ecology but differ in body size and phenologies. The critical thermal limits of individuals are assessed in both sexes of each parasitoid species and the influence of surface volume ratios on their thermal tolerances. Aphidius avenae is less resistant to low temperatures and more resistant to high temperatures than A. rhopalosiphi. The lower surface to volume ratio of A. avenae individuals may help them to remain active in summer when experiencing heat waves. However, body size is not the sole factor that plays a role in differences of thermal tolerance between species and body size may not be an adaptation to extreme temperatures but rather a by-product of developmental regulation. Closely-related sympatric species from the same ecological guild can have different thermal tolerances that may allow them to occur within the same habitat. The present study also highlights the importance of clearly defining how to measure critical thermal limits to determine the thermal tolerance of a species.
Keywords: Climate change; critical thermal limits; CTmax; CTmin; dry mass; guild; hind tibia length; seasonal activities; surface to volume ratio
|
Lalague, H., Csilléry, K., Oddou-Muratorio, S., Safrana, J., de Quattro, C., Fady, B., et al. (2014). Nucleotide diversity and linkage disequilibrium at 58 stress response and phenology candidate genes in a European beech (Fagus sylvatica L.) population from southeastern France. Tree Genetics and Genomes, 10(1), 15–26.
Abstract: European beech (Fagus sylvatica L.) is one of the most economically and ecologically important deciduous trees in Europe, yet little is known about its genomic diversity and its adaptive potential. Here, we detail the discovery and analysis of 573 single nucleotide polymorphisms (SNPs) from 58 candidate gene fragments that are potentially involved in abiotic stress response and budburst phenology using a panel of 96 individuals from southeastern France. The mean nucleotide diversity was low (θ π = 2.2 × 10-3) but extremely variable among gene fragments (range from 0.02 to 10), with genes carrying insertion/deletion mutations exhibiting significantly higher diversity. The decay of linkage disequilibrium (LD) measured at gene fragments >800 base pairs was moderate (the half distance of r 2 was 154 bp), consistent with the low average population-scaled recombination rate (ρ = 5.4 × 10-3). Overall, the population-scaled recombination rate estimated in F. sylvatica was lower than for other angiosperm tree genera (such as Quercus or Populus) and similar to conifers. As a methodological perspective, we explored the effect of minimum allele frequency (MAF) on LD and showed that higher MAF resulted in slower decay of LD. It is thus essential that the same MAF is used when comparing the decay of LD among different studies and species. Our results suggest that genome-wide association mapping can be a potentially efficient approach in F. sylvatica, which has a relatively small genome size. © 2013 Springer-Verlag Berlin Heidelberg.
Keywords: Climate adaptation; Effective population size; Forest tree; Genomic diversity; Minor allele frequency (MAF); Recombination rate; Single nucleotide polymorphism (SNP)
|
LaPierre, L., Hespenheide, H., & Dejean, A. (2007). Wasps robbing food from ants: a frequent behavior? Naturwissenschaften, 94(12), 997–1001.
Abstract: Food robbing, or cleptobiosis, has been well documented throughout the animal kingdom. For insects, intrafamilial food robbing is known among ants, but social wasps (Vespidae; Polistinae) taking food from ants has, to the best of our knowledge, never been reported. In this paper, we present two cases involving social wasps robbing food from ants associated with myrmecophytes. (1) Polybioides tabida F. (Ropalidiini) rob pieces of prey from Tetraponera aethiops Smith (Formicidae; Pseudomyrmecinae) specifically associated with Barteria fistulosa Mast. (Passifloraceae). (2) Charterginus spp. (Epiponini) rob food bodies from myrmecophytic Cecropia (Cecropiaceae) exploited by their Azteca mutualists (Formicidae; Dolichoderinae) or by opportunistic ants (that also attack cleptobiotic wasps). We note here that wasps gather food bodies (1) when ants are not yet active; (2) when ants are active, but avoiding any contact with them by flying off when attacked; and (3) through the coordinated efforts of two to five wasps, wherein one of them prevents the ants from leaving their nest, while the other wasps freely gather the food bodies. We suggest that these interactions are more common than previously thought.
Keywords: cleptobiosis; social wasps; charterginus; polybioides; plant-ants
|
Vedel, V., & Scotti, I. (2011). Promoting the promoter. Plant Sci., 180(2), 182–189.
Abstract: Recent evolutionary studies clearly indicate that evolution is mainly driven by changes in the complex mechanisms of gene regulation and not solely by polymorphism in protein-encoding genes themselves. After a short description of the cis-regulatory mechanism, we intend in this review to argue that by applying newly available technologies and by merging research areas such as evolutionary and developmental biology, population genetics, ecology and molecular cell biology it is now possible to study evolution in an integrative way. We contend that, by analysing the effects of promoter sequence variation on phenotypic diversity in natural populations, we will soon be able to break the barrier between the study of extant genetic variability and the study of major developmental changes. This will lead to an integrative view of evolution at different scales. Because of their sessile nature and their continuous development, plants must permanently regulate their gene expression to react to their environment, and can, therefore, be considered as a remarkable model for these types of studies. (C) 2010 Elsevier Ireland Ltd. All rights reserved.
Keywords: cis-Regulation; Evolutionary and developmental biology; Integrative evolution; Plant development; Population genetics; Transcription
|
Fontaine, S., Stahl, C., Klumpp, K., Picon-Cochard, C., Grise, M. M., Dezécache, C., et al. (2018). Response to Editor to the comment by Schipper and Smith to our paper entitled 'Continuous soil carbon storage of old permanent pastures in Amazonia'. Global Change Biology, 24(3), e732–e733.
Keywords: chronosequence study; continuous C accumulation; deep soil C; eddy covariance; grassland
|