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Bremaud, I.; Gril, J.; Thibaut, B. |
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Title |
Anisotropy of wood vibrational properties: dependence on grain angle and review of literature data |
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Journal Article |
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Year |
2011 |
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Wood Science and Technology |
Abbreviated Journal |
Wood Sci. Technol. |
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45 |
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4 |
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735-754 |
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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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[Bremaud, I; Gril, J] Univ Montpellier 2, Lab Mecan & Genie Civil, CNRS, CC048, F-34095 Montpellier 5, France, Email: iris_bremaud@hotmail.com |
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English |
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0043-7719 |
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WOS:000296006000009 |
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EcoFoG @ webmaster @ |
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369 |
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Ghislain, B.; Alméras, T.; Prunier, J.; Clair, B. |
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Title |
Contributions of bark and tension wood and role of the G-layer lignification in the gravitropic movements of 21 tropical tree species |
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Journal Article |
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Year |
2019 |
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Annals of Forest Science |
Abbreviated Journal |
Ann. Forest Sci. |
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76 |
Issue |
4 |
Pages |
107 |
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Bark; Biomechanics; G-layer; Lignification; Tension wood; Tropical rainforest; Magnoliophyta |
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Key message: Gravitropic movements in angiosperm woody stems are achieved through the action of bark and/or wood motor, depending on the bark and wood fibre anatomy (with trellis structure or not; with G-layers or not). Bark motor is as efficient as wood motor to recover from tilting in young trees of 21 tropical species. Context: Angiosperm trees produce tension wood to control their orientation through changes in stem curvature. Tension wood is classified into 3 anatomical groups: with unlignified G-layer, with lignified G-layer and without G-layer. Aims: This study aimed at assessing whether this anatomical diversity reflects a diversity in efficiency of gravitropic movement. Methods: The study was conducted on tropical seedling from the three anatomical groups. Seedlings were staked and grown tilted. At the end of the experiment, changes in curvature when releasing the stem from the stake and when removing bark were measured. Three parameters were computed to compare the global efficiency of gravitropism (stem gravitropic efficiency) and the specific efficiency of motor mechanism based on wood (maturation strain of tension wood) and bark (standardized debarking curvature). Results: The maturation strain of tension wood was similar between species with unlignified and lignified G-layer. Species without G-layer exhibited low maturation strain and large debarking curvature, showing they rely on bark for gravitropism. Bark and wood achieved similar motor efficiency. Conclusion: Lignin does not affect the generation of tensile stress in the G-layer. Bark can be as efficient as wood as a motor of gravitropic movements. © 2019, The Author(s). |
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Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier, CNRS, Montpellier, 34095, France |
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12864560 (Issn) |
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EcoFoG @ webmaster @ |
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900 |
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Ziegler, C.; Coste, S.; Stahl, C.; Delzon, S.; Levionnois, S.; Cazal, J.; Cochard, H.; Esquivel-Muelbert, A.; Goret, J.-Y.; Heuret, P.; Jaouen, G.; Santiago, L.S.; Bonal, D. |
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Title |
Large hydraulic safety margins protect Neotropical canopy rainforest tree species against hydraulic failure during drought |
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Journal Article |
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Year |
2019 |
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Annals of Forest Science |
Abbreviated Journal |
Ann. Forest Sci. |
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76 |
Issue |
4 |
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115 |
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Keywords |
Amazon rainforest; Embolism resistance; Hydraulic safety margins; Turgor loss point; Water potential |
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Key message: Abundant Neotropical canopy-tree species are more resistant to drought-induced branch embolism than what is currently admitted. Large hydraulic safety margins protect them from hydraulic failure under actual drought conditions. Context: Xylem vulnerability to embolism, which is associated to survival under extreme drought conditions, is being increasingly studied in the tropics, but data on the risk of hydraulic failure for lowland Neotropical rainforest canopy-tree species, thought to be highly vulnerable, are lacking. Aims: The purpose of this study was to gain more knowledge on species drought-resistance characteristics in branches and leaves and the risk of hydraulic failure of abundant rainforest canopy-tree species during the dry season. Methods: We first assessed the range of branch xylem vulnerability to embolism using the flow-centrifuge technique on 1-m-long sun-exposed branches and evaluated hydraulic safety margins with leaf turgor loss point and midday water potential during normal- and severe-intensity dry seasons for a large set of Amazonian rainforest canopy-tree species. Results: Tree species exhibited a broad range of embolism resistance, with the pressure threshold inducing 50% loss of branch hydraulic conductivity varying from − 1.86 to − 7.63 MPa. Conversely, we found low variability in leaf turgor loss point and dry season midday leaf water potential, and mostly large, positive hydraulic safety margins. Conclusions: Rainforest canopy-tree species growing under elevated mean annual precipitation can have high resistance to embolism and are more resistant than what was previously thought. Thanks to early leaf turgor loss and high embolism resistance, most species have a low risk of hydraulic failure and are well able to withstand normal and even severe dry seasons. © 2019, The Author(s). |
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Smithsonian Tropical Research Institute, Balboa, Ancon, Panama |
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12864560 (Issn) |
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EcoFoG @ webmaster @ |
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901 |
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Baudrimont, M.; Arini, A.; Guégan, C.; Venel, Z.; Gigault, J.; Pedrono, B.; Prunier, J.; Maurice, L.; Ter Halle, A.; Feurtet-Mazel, A. |
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Ecotoxicity of polyethylene nanoplastics from the North Atlantic oceanic gyre on freshwater and marine organisms (microalgae and filter-feeding bivalves) |
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Journal Article |
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2020 |
Publication |
Environmental Science and Pollution Research |
Abbreviated Journal |
Environ. Sci. Pollut. Res. |
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Volume |
27 |
Issue |
4 |
Pages |
3746-3755 |
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Keywords |
Cordicula fluminea; Ecotoxicity; Nanoplastics; Polyethylene; Scenedesmus subspicatus; Thalassiosira weissiflogii; bivalve; concentration (composition); ecotoxicology; filter feeder; gyre; microalga; nanoparticle; plastic waste; pollution exposure; polymer; Atlantic Ocean; Atlantic Ocean (North); Bivalvia; Chlorophyta; Corbicula fluminea; Desmodesmus subspicatus; Nitzschia alba; Thalassiosira |
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Each year, 5 to 10 million tons of plastic waste is dumped in the oceans via freshwaters and accumulated in huge oceanic gyres. Under the effect of several abiotic factors, macro plastic wastes (or plastic wastes with macro sizes) are fractionated into microplastics (MP) and finally reach the nanometric size (nanoplastic NP). To reveal potential toxic impacts of these NPs, two microalgae, Scenedemus subspicatus (freshwater green algae), and Thalassiosira weissiflogii (marine diatom) were exposed for up to 48 h at 1, 10, 100, 1000, and 10,000 μg/L to reference polyethylene NPs (PER) or NPs made from polyethylene collected in the North Atlantic gyre (PEN, 7th continent expedition in 2015). Freshwater filter-feeding bivalves, Corbicula fluminea, were exposed to 1000 μg/L of PER and PEN for 48 h to study a possible modification of their filtration or digestion capacity. The results show that PER and PEN do not influence the cell growth of T. weissiflogii, but the PEN exposure causes growth inhibition of S. subspicatus for all exposure concentrations tested. This growth inhibition is enhanced for a higher concentration of PER or PEN (10,000 μg/L) in S. subspicatus. The marine diatom T. weissiflogii appears to be less impacted by plastic pollution than the green algae S. subspicatus for the exposure time. Exposure to NPs does not lead to any alteration of bivalve filtration; however, fecal and pseudo-fecal production increased after PEN exposure, suggesting the implementation of rejection mechanisms for inedible particles. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature. |
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UMR IMRCP 5623, Université Paul Sabatier, CNRS, 118, route de Narbonne, Toulouse, 31062, France |
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09441344 (Issn) |
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Cited By :1; Export Date: 23 March 2020; Coden: Esple; Correspondence Address: Baudrimont, M.; UMR EPOC 5805, Université de Bordeaux—CNRS, Place du Dr Peyneau, France; email: magalie.baudrimont@u-bordeaux.fr |
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EcoFoG @ webmaster @ |
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925 |
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Dejean, A.; Petitclerc, F.; Azémar, F. |
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Seasonality influences ant-mediated nutrient acquisition (myrmecotrophy) by a Neotropical myrmecophyte |
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Journal Article |
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2020 |
Publication |
Evolutionary Ecology |
Abbreviated Journal |
Evol. Ecol. |
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Volume |
34 |
Issue |
4 |
Pages |
645-657 |
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Keywords |
Ant-plant relationships; Mutualism; Myrmecophyte; Myrmecotrophy; Phenology; Stable isotopes; ant; herb; host plant; life cycle; myrmecochory; myrmecophyte; Neotropical Region; phenology; seasonality; stable isotope; understory; Gentianaceae; Tachia; Tachia guianensis |
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Tachia guianensis (Gentianaceae), a Neotropical understory myrmecophyte, shelters ant colonies in its hollow trunks and branches (domatia). In turn, it is protected from defoliators and obtains nutrients from ant-produced wastes (myrmecotrophy). Aiming to verify if seasonality influences nitrogen assimilation via ant wastes using the stable isotope nitrogen-15, we first studied Tachia’s phenology and its seasonal leaf production, and then the life cycle of its two more frequent guest ant species. We found that leaf production was much higher during the rainy than the dry season. Mature guest ant colonies produced sexuals regardless of the season and the net weight of the waste piles inside the domatia did not vary between seasons, so that the availability of nutrients to their host plant is steady year-long. By providing the two most frequent mutualistic guest ant species with food enriched with nitrogen-15, we showed that Tachia individuals assimilate more nitrogen from ant wastes during the rainy season, when the plant is physiologically active, compared to the dry season. Thus, one can deduce that the increase in nitrogen assimilation during the rainy season is determined by the increase in Tachia’s physiological activity during that season. Information gathered through a bibliographic compilation confirms that none of the 15 ant species known to be associated with myrmecophytes for which the life cycle was studied is characterized by seasonal reproduction (which would result in fluctuating waste production). The same is true for 49.7% of 167 tropical ant species (seasonal production for the remaining species). We concluded that, in contrast to the non-seasonal ant colony reproductive cycle, Tachia’s phenology determines the myrmecotrophic assimilation rate. © 2020, Springer Nature Switzerland AG. |
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CNRS, UMR EcoFoG, AgroParisTech, CIRAD, INRAE, Université des Antilles, Université de Guyane, Kourou, 97310, France |
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02697653 (Issn) |
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EcoFoG @ webmaster @ |
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956 |
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Talaga, S.; Dejean, A.; Azémar, F.; Dumont, Y.; Leroy, C. |
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Impacts of biotic and abiotic parameters on immature populations of Aedes aegypti |
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Journal Article |
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2020 |
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Journal of Pest Science |
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J. Pest Sci. |
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93 |
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3 |
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941-952 |
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Biocontrol agents; Competition; Ecosystem services; Mosquito control; Mosquito management; Predation; abiotic factor; biotic factor; competitive displacement; disease vector; maturation; mosquito; pest control; Aedes aegypti; Hexapoda; Zika virus |
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In recent centuries, the mosquito Aedes aegypti has spread into most urban areas throughout the tropics. This species is considered the main vector of the chikungunya, dengue, yellow fever and Zika viruses and causes major public health issues. The aim of this study is to investigate the relative influence of biotic and abiotic parameters on immature populations of Ae. aegypti. During a one-year-long field experiment, we monitored 108 macroinvertebrate aquatic communities inhabiting four types of water containers across three different urbanized sites in a Neotropical city. A multimodel inference approach revealed that, in addition to abiotic parameters, biotic interactions with aquatic organisms had an important influence on the abundance of Ae. aegypti and that the urbanized site considered influences the outcomes of the interactions. Controphic species other than mosquitoes aided Ae. aegypti development, suggesting a mechanism of facilitation through a chain of processes. However, the abundance of Ae. aegypti was lowered by competition with native mosquito species in the slightly urbanized area and by predation in more urbanized areas. Competitive displacement and reduction, as well as predation by native aquatic organisms, can be considered a form of ecosystem service. The conservation and/or augmentation of natural enemies should improve the short- and long-term success of incompatible and/or sterile insect techniques, thus opening up perspectives for the future of mosquito management. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature. |
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University of Pretoria, Department of Mathematics and Applied Mathematics, Pretoria, South Africa |
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16124758 (Issn) |
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EcoFoG @ webmaster @ |
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962 |
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Van Langenhove, L.; Verryckt, L.T.; Bréchet, L.; Courtois, E.A.; Stahl, C.; Hofhansl, F.; Bauters, M.; Sardans, J.; Boeckx, P.; Fransen, E.; Peñuelas, J.; Janssens, I.A. |
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Title |
Atmospheric deposition of elements and its relevance for nutrient budgets of tropical forests |
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Journal Article |
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2020 |
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Biogeochemistry |
Abbreviated Journal |
Biogeochemistry |
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149 |
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2 |
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175-193 |
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Litterfall; Nitrogen; Nutrient cycling; Phosphorus; Potassium; Throughfall; atmospheric deposition; canopy exchange; field method; forest floor; leaching; litterfall; nutrient cycling; phosphorus; potassium; precipitation (climatology); rainforest; tropical forest; French Guiana |
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Atmospheric deposition is an important component of the nutrient cycles of terrestrial ecosystems, but field measurements are especially scarce in tropical regions. In this study we analysed 15 months of precipitation chemistry collected in an old growth tropical forest located in French Guiana. We measured nutrient inputs via bulk precipitation and throughfall and used the canopy budget model to estimate nutrient fluxes via canopy exchange and dry deposition. Based on this method we quantified net fluxes of macronutrients and compared their contribution to internal cycling rates via litterfall. Our results suggest that while atmospheric deposition of nitrogen was relatively high (13 kg ha−1 year−1), and mainly in organic forms, the N inputs via litterfall were an order of magnitude higher. In contrast to nitrogen, we found that atmospheric deposition of phosphorus (0.5 kg ha−1 year−1) supplied up to one third of the annual litterfall input to the forest floor. Most strikingly, combined annual inputs of potassium via atmospheric deposition (14 kg ha−1 year−1) and canopy leaching (22 kg ha−1 year−1) were three times larger than internal nutrient recycling via litterfall (11 kg ha−1 year−1). We conclude that atmospheric deposition of phosphorus and especially potassium may play an important role in sustaining the productivity of this old-growth tropical rainforest. © 2020, Springer Nature Switzerland AG. |
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StatUa Center for Statistics, University of Antwerp, Prinsstraat 13, Antwerp, 2000, Belgium |
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01682563 (Issn) |
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EcoFoG @ webmaster @ |
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964 |
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Van Langenhove, L.; Depaepe, T.; Vicca, S.; van den Berge, J.; Stahl, C.; Courtois, E.; Weedon, J.; Urbina, I.; Grau, O.; Asensio, D.; Peñuelas, J.; Boeckx, P.; Richter, A.; Van Der Straeten, D.; Janssens, I.A. |
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Regulation of nitrogen fixation from free-living organisms in soil and leaf litter of two tropical forests of the Guiana shield |
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Journal Article |
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2020 |
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Plant and Soil |
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Plant Soil |
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450 |
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1-2 |
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93-110 |
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Free-living nitrogen fixation; French Guiana; Molybdenum; Nutrients; Phosphorus; Tropical forest; acetylene; leaf litter; molybdenum; nitrogen fixation; nutrient cycling; phosphorus; rainforest; reduction; soil biota; soil carbon; soil nitrogen; soil water; topographic effect; tropical forest; French Guiana |
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Background and aims: Biological fixation of atmospheric nitrogen (N2) is the main pathway for introducing N into unmanaged ecosystems. While recent estimates suggest that free-living N fixation (FLNF) accounts for the majority of N fixed in mature tropical forests, the controls governing this process are not completely understood. The aim of this study was to quantify FLNF rates and determine its drivers in two tropical pristine forests of French Guiana. Methods: We used the acetylene reduction assay to measure FLNF rates at two sites, in two seasons and along three topographical positions, and used regression analyses to identify which edaphic explanatory variables, including carbon (C), nitrogen (N), phosphorus (P) and molybdenum (Mo) content, pH, water and available N and P, explained most of the variation in FLNF rates. Results: Overall, FLNF rates were lower than measured in tropical systems elsewhere. In soils seasonal variability was small and FLNF rates differed among topographies at only one site. Water, P and pH explained 24% of the variation. In leaf litter, FLNF rates differed seasonally, without site or topographical differences. Water, C, N and P explained 46% of the observed variation. We found no regulatory role of Mo at our sites. Conclusions: Rates of FLNF were low in primary rainforest on poor soils on the Guiana shield. Water was the most important rate-regulating factor and FLNF increased with increasing P, but decreased with increasing N. Our results support the general assumption that N fixation in tropical lowland forests is limited by P availability. © 2019, The Author(s). |
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Department of Microbiology and Ecosystem Science, University of Vienna, Althanstr. 14, Vienna, 1090, Austria |
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0032079x (Issn) |
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EcoFoG @ webmaster @ |
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971 |
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Lang, G.; Marcon, E.; Puech, F. |
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Distance-based measures of spatial concentration: introducing a relative density function |
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Journal Article |
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2020 |
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Annals of Regional Science |
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Ann. Reg. Sci. |
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64 |
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2 |
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243-265 |
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Agglomeration; Aggregation; Economic geography; Point patterns; Spatial concentration; accuracy assessment; econometrics; economic activity; economic geography; industrial agglomeration; industrial location; location decision; spatial analysis; spatial distribution |
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For more than a decade, distance-based methods have been widely employed and constantly improved in spatial economics. These methods are a very useful tool for accurately evaluating the spatial distribution of economic activity. We introduce a new distance-based statistical measure for evaluating the spatial concentration of industries. The m function is the first relative density function to be proposed in economics. This tool supplements the typology of distance-based methods recently drawn up by Marcon and Puech (J Econ Geogr 3(4):409–428, 2003). By considering several simulated and real examples, we show the advantages and the limits of the m function for detecting spatial structures in economics. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature. |
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RITM, Univ. Paris-Sud, Université Paris-Saclay and CREST, Sceaux, France |
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EcoFoG @ webmaster @ |
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976 |
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Author |
Urbina, I.; Grau, O.; Sardans, J.; Ninot, J.M.; Peñuelas, J. |
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Title |
Encroachment of shrubs into subalpine grasslands in the Pyrenees changes the plant-soil stoichiometry spectrum |
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Journal Article |
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2020 |
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Plant and Soil |
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Plant Soil |
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448 |
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1-2 |
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37-53 |
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Keywords |
Nutrient stocks; Plant strategy; Plant-soil stoichiometry; Shrub encroachment; Subalpine grassland succession; aboveground biomass; biogeochemical cycle; carbon sequestration; ectomycorrhiza; fungus; grass; nitrogen; nutrient uptake; shrub; soil-vegetation interaction; stoichiometry; subalpine environment; succession; Europe; Pyrenees; Fungi |
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Abstract |
Aims: Shrub encroachment has been reported over a large proportion of the subalpine grasslands across Europe and is expected to have an important impact on the biogeochemical cycle of these ecosystems. We investigated the stoichiometric changes in the plant-soil system along the succession (e.g. increase in encroachment from unencroached grassland to mature shrubland) at two contrasting sites in the Pyrenees. Methods: We analyzed the chemical composition (C, N,15N, P, K, Ca, Mg and Fe) in the soil and in the aboveground plant compartments (leaves, leaf-litter and stems) of the main herbaceous species and shrubs at three contrasting stages of the succession: unencroached grassland, young shrubland and mature shrubland. Results: The plant-soil stoichiometry spectrum differed between the successional stages. Shrub encroachment generally increased the concentration of C and Ca and the C:N ratio and often reduced to concentrations of N, P and K in the leaves and leaf-litter, while several soil nutrient concentrations (N, P, K Ca and Mg) decreased. The stocks of C, N, P, Ca, and Mg in the total aboveground biomass increased with encroachment. Conclusions: Shrub encroachment favored the dominance of long-lived species with low concentrations of N and P in the plant-soil compartments, high C:nutrient ratios in the aboveground biomass and increase the uptake of N through ericoid or ectomycorrhizal fungi. We highlight the role of shrubs in the sequestration of C and nutrients through the allocation to the aboveground biomass. The changes in plant-soil elemental composition and stocks suggest a slowdown of the biogeochemical cycles in the subalpine mountain areas where shrub encroachment occurred. © 2020, Springer Nature Switzerland AG. |
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Biodiversity Research Institute (IRBio) and Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, Barcelona, Catalonia, Spain |
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Springer |
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0032079x (Issn) |
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EcoFoG @ webmaster @ |
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983 |
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