Asensio D., Peñuelas J., Filella I., Llusià J. (2007) On-line screening of soil VOCs exchange responses to moisture, temperature and root presence. Plant and Soil. 291: 249-261.LinkDoi: 10.1007/s11104-006-9190-4
The exchanges of volatile organic compounds (VOCs) between soils and the atmosphere are poorly known. We investigated VOC exchange rates and how they were influenced by soil moisture, temperature and the presence of plant roots in a Mediterranean forest soil. We measured VOC exchange rates along a soil moisture gradient (5%-12.5%-20%-27.5% v/v) and a temperature gradient (10°C-15°C-25°C-35°C) using PTR-MS. Monoterpenes were identified with GC-MS. Soils were a sink rather than a source of VOCs in both soil moisture and temperature treatments (-2.16 ± 0.35 nmol m-2 s-1 and -4.90 ± 1.24 nmol m-2 s-1 respectively). Most compounds observed were oxygenated VOCs like alcohols, aldehydes and ketones and aromatic hydrocarbons. Other volatiles such as acetic acid and ethyl acetate were also observed. All those compounds had very low exchange rates (maximum uptake rates from -0.8 nmol m-2 s -1 to -0.6 nmol m-2 s-1 for methanol and acetic acid). Monoterpene exchange ranged only from -0.004 nmol m-2 s -1 to 0.004 nmol m-2 s-1 and limonene and α-pinene were the most abundant compounds. Increasing soil moisture resulted in higher soil sink activity possibly due to increases in microbial VOCs uptake activity. No general pattern of response was found in the temperature gradient for total VOCs. Roots decreased the emission of many compounds under increasing soil moisture and under increasing soil temperature. While our results showed that emission of some soil VOCs might be enhanced by the increases in soil temperature and that the uptake of most soil VOCs uptake might be reduced by the decreases of soil water availability, the low exchange rates measured indicated that soil-atmosphere VOC exchange in this system are unlikely to play an important role in atmospheric chemistry. © 2007 Springer Science+Business Media B.V.
Asensio D., Peñuelas J., Llusià J., Ogaya R., Filella I. (2007) Interannual and interseasonal soil CO2 efflux and VOC exchange rates in a Mediterranean holm oak forest in response to experimental drought. Soil Biology and Biochemistry. 39: 2471-2484.LinkDoi: 10.1016/j.soilbio.2007.04.019
Climate models predict drier conditions in the next decades in the Mediterranean basin. Given the importance of soil CO2 efflux in the global carbon balance and the important role of soil monoterpene and volatile organic compounds (VOCs) in soil ecology, we aimed to study the effects of the predicted drought on soil CO2, monoterpenes and other VOC exchange rates and their seasonal and interannual variations. We decreased soil water availability in a Mediterranean holm oak forest soil by means of an experimental drought system performed since 1999 to the present. Measurements of soil gas exchange were carried out with IRGA, GC and PTR-MS techniques during two annual campaigns of contrasting precipitation. Soil respiration was twice higher the wet year than the dry year (2.27±0.26 and 1.05±0.15, respectively), and varied seasonally from 3.76±0.85 μmol m-2 s-1 in spring, to 0.13±0.01 μmol m-2 s-1 in summer. These results highlight the strong interannual and interseasonal variation in CO2 efflux in Mediterranean ecosystems. The drought treatment produced a significant soil respiration reduction in drought plots in the wet sampling period. This reduction was even higher in wet springs (43% average reduction). These results show (1) that soil moisture is the main factor driving seasonal and interannual variations in soil respiration and (2) that the response of soil respiration to increased temperature is constrained by soil moisture. The results also show an additional control of soil CO2 efflux by physiology and phenology of trees and animals. Soil monoterpene exchange rates ranged from -0.01 to 0.004 nmol m-2 s-1, thus the contribution of this Mediterranean holm oak forest soil to the total monoterpenes atmospheric budget seems to be very low. Responses of individual monoterpenes and VOCs to the drought treatment were different depending on the compound. This suggests that the effect of soil moisture reduction in the monoterpenes and VOC exchange rates seems to be dependent on monoterpene and VOC type. In general, soil monoterpene and other VOC exchange rates were not correlated with soil CO2 efflux. In all cases, only a low proportion of variance was explained by the soil moisture changes, since almost all VOCs increased their emission rates in summer 2005, probably due to the effect of high soil temperature. Results indicate thus that physical and biological processes in soil are controlling soil VOC exchange but further research is needed on how these factors interact to produce the observed VOCs exchange responses. © 2007 Elsevier Ltd. All rights reserved.
Filella I., Wilkinson M.J., Llusià J., Hewitt C.N., Peñuelas J. (2007) Volatile organic compounds emissions in Norway spruce (Picea abies) in response to temperature changes. Physiologia Plantarum. 130: 58-66.LinkDoi: 10.1111/j.1399-3054.2007.00881.x
Volatile organic compound (VOC) emissions from Norway spruce (Picea abies) saplings were monitored in response to a temperature ramp. Online measurements were made with a proton transfer reaction - mass spectrometer under controlled conditions, together with plant physiological variables. Masses corresponding to acetic acid and acetone were the most emitted VOCs. The emission rates of m137 (monoterpenes), m59 (acetone), m33 (methanol), m83 (hexanal, hexenals), m85 (hexanol) and m153 (methyl salicylate, MeSa) increased exponentially with temperature. The emission of m61 (acetic acid) and m45 (acetaldehyde), however, increased with temperature only until saturation around 30°C, closely following the pattern of transpiration rates. These results indicate that algorithms that use only incident irradiance and leaf temperature as drivers to predict VOC emission rates may be inadequate for VOCs with lower H, and consequently higher sensitivity to stomatal conductance. © Physiologia Plantarum 2007.
Bartolome J, Peñuelas J, Filella I, Llusià J, Broncano MJ, Plaixats J (2007) Mass scans from a proton transfer mass spectrometry analysis of air over Mediterranean shrubland browsed by horses. Journal Environmental Biologi 28: 697-700
Peñuelas J, Sardans J, Stefanescu C, Parella T, Filella I (2007) Transferencia de defenses de les plantes als herbívors. UAB DIVULGA 05/2007.
Peñuelas J., Estiarte M, Ogaya R, Filella I, Jump A, Garbulsky M, Sardans J., Llusià J, Seco R, Alessio G., Hunt J, Owen S, Asensio D, Prieto P, Ribas A, Carrillo B, Blanch S, Coll M, Kefauer S, Stefanescu C, Lloret F, Terradas J (2007) Climate change effects on Mediterranean forests: from observations to experimentation, from genetics to remote sensing. Afforestation and sustainable forests as means to combat desertification. 16-19 April Jerusalem, Israel, p. 50.
Peñuelas J., Llusià J., Filella I. (2007) Methyl salicylate fumigation increases monoterpene emission rates. Biologia Plantarum. 51: 372-376.LinkDoi: 10.1007/s10535-007-0078-9
We aimed to assess the potential effects of fumigation by methyl salicylate (MeSA) on plant monoterpene production and emissions. We evaluated monoterpene production and emissions both by chromatographic and proton transfer reaction mass spectrometry at the whole plant-and leaf-scales, in MeSa-fumigated (ca. 60 mm3 m-3 in air) and control (without MeSa fumigation) holm oak (Quercus ilex L.) plants exposed to temperatures ranging from 25 to 50 °C. The MeSa-fumigated plants showed ca. 3-4-fold greater leaf monoterpene concentrations and emission rates than the control plants between the temperatures of 25 to 45 °C. © 2007 Institute of Experimental Botany, ASCR.
Seco R., Peñuelas J., Filella I. (2007) Short-chain oxygenated VOCs: Emission and uptake by plants and atmospheric sources, sinks, and concentrations. Atmospheric Environment. 41: 2477-2499.LinkDoi: 10.1016/j.atmosenv.2006.11.029
Emissions of volatile organic compounds (VOCs) have multiple atmospheric implications and play many roles in plant physiology and ecology. Among these VOCs, growing interest is being devoted to a group of short-chain oxygenated VOCs (oxVOCs). Technology improvements such as proton transfer reaction-mass spectrometry are facilitating the study of these hydrocarbons and new data regarding these compounds is continuously appearing. Here we review current knowledge of the emissions of these oxVOCs by plants and the factors that control them, and also provide an overview of sources, sinks, and concentrations found in the atmosphere. The oxVOCs reviewed here are formic and acetic acids, acetone, formaldehyde, acetaldehyde, methanol, and ethanol. In general, because of their water solubility (low gas-liquid partitioning coefficient), the plant-atmosphere exchange is stomatal-dependent, although it can also take place via the cuticle. This exchange is also determined by atmospheric mixing ratios. These compounds have relatively long atmospheric half-lives and reach considerable concentrations in the atmosphere in the range of ppbv. Likewise, under non-stressed conditions plants can emit all of these oxVOCs together at fluxes ranging from 0.2 up to 4.8 μg(C)g-1(leaf dry weight)h-1 and at rates that increase several-fold when under stress. Gaps in our knowledge regarding the processes involved in the synthesis, emission, uptake, and atmospheric reactivity of oxVOCs precludes the clarification of exactly what is conditioning plant-atmosphere exchange-and also when, how, and why this occurs-and these lacunae therefore warrant further research in this field. © 2006 Elsevier Ltd. All rights reserved.
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