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| Van Langenhove, Leandro; Verryckt, Lore T.; Bréchet, Laëtitia; Courtois, Elodie A.; Stahl, Clement; Hofhansl, Florian; Bauters, Marijn; Sardans, Jordi; Boeckx, Pascal; Fransen, Erik; Peñuelas, Josep; Janssens, Ivan A.. |
| 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... |
| Tipo: Text |
Palavras-chave: Throughfall; Litterfall; Nutrient cycling; Nitrogen; Phosphorus; Potassium. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00629/74123/73572.pdf |
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| Courtois, Elodie Alice; Stahl, Clement; Burban, Benoit; Van Den Berge, Joke; Berveiller, Daniel; Brechet, Laetitia; Soong, Jennifer Larned; Arriga, Nicola; Penuelas, Josep; Janssens, Ivan August. |
| Measuring in situ soil fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) continuously at high frequency requires appropriate technology. We tested the combination of a commercial automated soil CO2 flux chamber system (LI-8100A) with a CH4 and N2O analyzer (Picarro G2308) in a tropical rainforest for 4 months. A chamber closure time of 2 min was sufficient for a reliable estimation of CO2 and CH4 fluxes (100% and 98.5% of fluxes were above minimum detectable flux - MDF, respectively). This closure time was generally not suitable for a reliable estimation of the low N2O fluxes in this ecosystem but was sufficient for detecting rare major peak events. A closure time of 25 min was more appropriate for reliable estimation of most N2O... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00482/59369/62475.pdf |
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| Aguilos, Maricar; Stahl, Clement; Burban, Benoit; Herault, Bruno; Courtois, Elodie; Coste, Sabrina; Wagner, Fabien; Ziegler, Camille; Takagi, Kentaro; Bonal, Damien. |
| Warmer and drier climates over Amazonia have been predicted for the next century with expected changes in regional water and carbon cycles. We examined the impact of interannual and seasonal variations in climate conditions on ecosystem-level evapotranspiration (ET) and water use efficiency (WUE) to determine key climatic drivers and anticipate the response of these ecosystems to climate change. We used daily climate and eddyflux data recorded at the Guyaflux site in French Guiana from 2004 to 2014. ET and WUE exhibited weak interannual variability. The main climatic driver of ET and WUE was global radiation (Rg), but relative extractable water (REW) and soil temperature (Ts) did also contribute. At the seasonal scale, ET and WUE showed a modal pattern... |
| Tipo: Text |
Palavras-chave: Tropical rainforest; Evapotranspiration; Water use efficiency; Drought; Radiation. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00484/59572/62542.pdf |
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| Van Langenhove, Leandro; Janssens, Ivan A.; Verryckt, Lore; Brechet, Laetitia; Hartley, Iain P.; Stahl, Clement; Courtois, Elodie; Urbina, Ifigenia; Grau, Oriol; Sardans, Jordi; Peguero, Guille; Gargallo-garriga, Albert; Peñuelas, Josep; Vicca, Sara. |
| Theory states that tree growth in lowland tropical forests on old, weathered soils is limited by low phosphorous (P) availability. However, evidence for P limitation from nutrient manipulation experiments remains unclear, which raises the question whether trees are taking up added P. In French Guianese lowland rainforest, we measured changes in nitrogen (N) and P availability before and up to two months after N and P addition. We measured in soils with intact root systems and soils excluding roots and mycorrhizal fungi with root exclusion cylinders. When the root system was excluded, P addition increased P availability to a much greater extent and for a longer time than where the roots remained undisturbed. N dynamics were unaffected by root... |
| Tipo: Text |
Palavras-chave: Tropical forest; Phosphorus; Nitrogen; Fertilization; Root system; Plant root simulator probes. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00589/70161/68163.pdf |
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| Van Langenhove, Leandro; Depaepe, Thomas; Vicca, Sara; Van Den Berge, Joke; Stahl, Clement; Courtois, Elodie; Weedon, James; Urbina, Ifigenia; Grau, Oriol; Asensio, Dolores; Peñuelas, Josep; Boeckx, Pascal; Richter, Andreas; Van Der Straeten, Dominique; Janssens, Ivan A.. |
| 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... |
| Tipo: Text |
Palavras-chave: Free-living nitrogen fixation; Tropical forest; French Guiana; Nutrients; Phosphorus; Molybdenum. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00487/59901/63083.pdf |
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