  Abiotic and biotic control of methanol exchanges in a temperate mixed forestLaffineur, Quentin  ; Aubinet, Marc ; et alin Atmospheric Chemistry and Physics (2012), 12 Methanol exchanges over a mixed temperate forest in the Belgian Ardennes were measured for more than one vegetation season using disjunct eddy-covariance by a mass scanning technique and Proton Transfer ... [more ▼] Methanol exchanges over a mixed temperate forest in the Belgian Ardennes were measured for more than one vegetation season using disjunct eddy-covariance by a mass scanning technique and Proton Transfer Reaction Mass Spectrometry (PTR-MS). Half-hourly methanol fluxes were measured in the range of −0.6 μgm−2 s−1 to 0.6 μgm−2 s−1, and net daily methanol fluxes were generally negative in summer and autumn and positive in spring. On average, the negative fluxes dominated (i.e. the site behaved as a net sink), in contrast to what had been found in previous studies. An original model describing the adsorption/desorption of methanol in water films present in the forest ecosystem and the methanol degradation process was developed. Its calibration, based on field measurements, predicted a mean methanol degradation rate of −0.0074 μgm−2 s−1 and a half lifetime for methanol in water films of 57.4 h. Biogenic emissions dominated the exchange only in spring, with a standard emission factor of 0.76 μgm−2 s−1. The great ability of the model to reproduce the long-term evolution, as well as the diurnal variation of the fluxes, suggests that the adsorption/desorption and degradation processes play an important role in the global methanol budget. This result underlines the need to conduct long-term measurements in order to accurately capture these processes and to better estimate methanol fluxes at the ecosystem scale. [less ▲] Detailed reference viewed: 20 (8 ULg)Clear link between drought stress, photosynthesis and biogenic volatile organic compounds in Fagus sylvatica L.; ; et al in Atmospheric Environment (2011), 45(30), 5254-5259 Direct plant stress sensing is the key for a quantitative understanding of drought stress effects on biogenic volatile organic compound (BVOC) emissions. A given level of drought stress might have a ... [more ▼] Direct plant stress sensing is the key for a quantitative understanding of drought stress effects on biogenic volatile organic compound (BVOC) emissions. A given level of drought stress might have a fundamentally different effect on the BVOC emissions of different plants. For the first time, we continuously quantified the level of drought stress in a young potted beech (Fagus sylvatica L.) with a linear variable displacement transducer (LVDT) installed at stem level in combination with simultaneous measurements of BVOC emissions and photosynthesis rates at leaf level. This continuous set of measurements allowed us to examine how beech alters its pattern of photosynthesis and carbon allocation to BVOC emissions (mainly monoterpenes, MTs) and radial stem growth during the development of drought stress. We observed an increasing-decreasing trend in the MT emissions as well as in the fraction of assimilated carbon re-emitted back into the atmosphere (ranging between 0.14 and 0.01%). We were able to link these dynamics to pronounced changes in radial stem growth, which served as a direct plant stress indicator. Interestingly, we detected a sudden burst in emission of a non-identified, non-MT BVOC species when drought stress was acute (i.e. pronounced negative stem growth). This burst might have been caused by a certain stress-related green leaf volatile, which disappeared immediately upon re-watering and thus the alleviation of drought stress. These results highlight that direct plant stress sensing creates opportunities to understand the overall complexity of stress-related BVOC emissions. [less ▲] Detailed reference viewed: 5 (0 ULg)Constitutive versus heat and biotic stress induced BVOC emissions in Pseudotsuga menziesii; ; et al in Atmospheric Environment (2011), 45(22), 3655-3662 Induced volatiles have been a focus of recent research, as not much is known of their emission behavior or atmospheric contribution. BVOC emissions were measured from Pseudotsuga menziesii saplings under ... [more ▼] Induced volatiles have been a focus of recent research, as not much is known of their emission behavior or atmospheric contribution. BVOC emissions were measured from Pseudotsuga menziesii saplings under natural environmental conditions, using a dynamic branch enclosure system and GC-MS for their analysis. We determined temperature and light dependency of the individual compounds, studied seasonality of the emissions and discuss the effect of heat stress in comparison with two specific biotic stresses that occurred naturally on the trees. A standardized emission rate of 6.8 μg g (dw) -1 h -1 for monoterpenes under stressed conditions was almost a magnitude higher than that obtained for healthy trees (0.8 ± 0.2 μg g (dw) -1 h -1), with higher beta factors characterizing the stressed trees. The response of the emissions to light intensity was different for the individual compounds, suggesting a distinct minimum light intensity to reach saturation. Heat stress changed the relative contribution of specific volatiles, with larger extent of increase of sesquiterpenes, methyl salicylate and linalool emissions compared to monoterpenes. Biotic stress kept low the emissions of sesquiterpenes, (E)-4,8-dimethyl-1,3,7-nonatriene and methylbutenol isomers, and increased the level of methyl salicylate and monoterpenes. The ratio of β-pinene/α-pinene was also found to be significantly enhanced from 1.3 to 2.4 and 3.2 for non-stressed, heat stressed and combined biotic and heat stressed, respectively. [less ▲] Detailed reference viewed: 3 (1 ULg)Comparing monoterpenoid emissions and net photosynthesis of beech (Fagus sylvatica L.) in controlled and natural conditions; ; et al in Atmospheric Environment (2011), 45(17), 2922-2928 Although biogenic volatile organic compounds (BVOCs) only represent a very limited fraction of the plant's carbon (C) budget, they play an important role in atmospheric chemistry for example as a ... [more ▼] Although biogenic volatile organic compounds (BVOCs) only represent a very limited fraction of the plant's carbon (C) budget, they play an important role in atmospheric chemistry for example as a precursor of tropospheric ozone. We performed a study comparing BVOC emissions of European beech (Fagus sylvatica L.) in controlled and natural environmental conditions. A young and adult beech tree was exposed to short-term temperature variations in growth room conditions and in an experimental forest, respectively. This study attempts to clarify how short-term temperature variations between days influenced the ratio between monoterpenoid (MT) emissions and net photosynthesis (Pn). Within a temperature range of 17-27 °C and 13-23 °C, the MT/Pn carbon ratio increased 10-30 fold for the growth room and forest, respectively. An exponential increasing trend between MT/Pn C ratio and air temperature was observed in both conditions. Beech trees re-emitted a low fraction of the assimilated C back into the atmosphere as MT: 0.01-0.12% and 0.01-0.30% with a temperature rise from 17 to 27 °C and 13-23 °C in growth room and forest conditions, respectively. However, the data showed that the MT/Pn C ratio of young and adult beech trees responded significantly to changes in temperature. [less ▲] Detailed reference viewed: 4 (1 ULg) Disjunct eddy-covariance as a tool for biogenic volatile organic compounds flux estimation at the ecosystemscale.Heinesch, Bernard ; Laffineur, Quentin ; et alScientific conference (2011, May 12) Detailed reference viewed: 26 (8 ULg)First space-based derivation of the global atmospheric methanol emission fluxes; ; et al in Atmospheric Chemistry and Physics (2011), 11 Detailed reference viewed: 8 (4 ULg)Isoprene and monoterpene emissions from a mixed temperate forestLaffineur, Quentin ; Aubinet, Marc ; et alin Atmospheric Environment (2011), 45 Detailed reference viewed: 15 (2 ULg)History effect of light and temperature on monoterpenoid emissions from Fagus sylvatica L.; ; et al in Atmospheric Environment (2010), 44(27), 3261-3268 Monoterpenoid emissions from Fagus sylvatica L trees have been measured at light- and temperature-controlled conditions in a growth chamber, using Proton Transfer Reaction Mass Spectrometry (PTR-MS) and ... [more ▼] Monoterpenoid emissions from Fagus sylvatica L trees have been measured at light- and temperature-controlled conditions in a growth chamber, using Proton Transfer Reaction Mass Spectrometry (PTR-MS) and the dynamic branch enclosure technique. De novo synthesized monoterpenoid Standard Emission Factors, obtained by applying the G97 algorithm (Guenther, 1997), varied between 2 and 32 mu g g(-1)DW h(-1) and showed a strong decline in late August and September, probably due to senescence. The response of monoterpenoid emissions to temperature variations at a constant daily light pattern could be well reproduced with a modified version of the MEGAN algorithm (Guenther et al., 2006), with a typical dependence on the average temperature over the past five days. The diurnal emissions at constant temperature showed a typical hysteretic behaviour, which could also be adequately described with the modified MEGAN algorithm by taking into account a dependence on the average light levels experienced by the trees during the past 10-13 h. The impact of the past light and temperature conditions on the monoterpenoid emissions from E sylvatica L was found to be much stronger than assumed in previous algorithms. Since our experiments were conducted under low light intensity, future studies should aim at confirming and completing the proposed algorithm updates in sunny conditions and natural environments. (C) 2010 Elsevier Ltd. All rights reserved. [less ▲] Detailed reference viewed: 8 (3 ULg) |
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