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Thomas Holst
Department of Physical Geography and Ecosystem Science Lund University Lund Sweden

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Primary research articles
Published: 24 May 2021 in Global Change Biology
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The extreme 2018 hot drought that affected central and northern Europe led to the worst wildfire season in Sweden in over a century. The Ljusdal fire complex, the largest area burnt that year (8995 ha), offered the rare opportunity to quantify the combined impacts of wildfire and post-fire management on Scandinavian boreal forests. We present chamber measurements of soil CO2 and CH4 fluxes, soil microclimate and nutrient content from five Pinus sylvestris sites in this area for the first growing season after the fire. We analysed the effects of three factors on forest soils: burn severity, salvage-logging and stand age. None of these caused significant differences in soil CH4 uptake. Soil respiration, however, declined significantly after a high severity fire (complete tree mortality) but not after a low severity fire (no tree mortality), despite substantial losses of the soil organic layer. Tree root respiration is thus key in determining post-fire soil CO2 emissions and may benefit, along with heterotrophic respiration, from the nutrient pulse after a low severity fire. Salvage-logging after a high severity fire had no significant effects on soil carbon fluxes, microclimate or nutrient content compared to leaving the dead trees standing, although differences are expected to emerge in the long-term. In contrast, the impact of stand age was substantial: a young burnt stand experienced more extreme microclimate, lower soil nutrient supply and significantly lower soil respiration than a mature burnt stand, due to a thinner organic layer and the decade-long effects of a previous clear-cut and soil scarification. Disturbance history and burn severity are therefore important factors for predicting changes in the boreal forest carbon sink after wildfires. The presented short-term effects and ongoing monitoring will provide essential information for sustainable management strategies in response to the increasing risk of wildfire.

ACS Style

Julia Kelly; Theresa S. Ibáñez; Cristina Santín; Stefan H. Doerr; Marie‐Charlotte Nilsson; Thomas Holst; Anders Lindroth; Natascha Kljun. Boreal forest soil carbon fluxes one year after a wildfire: Effects of burn severity and management. Global Change Biology 2021, 27, 4181 -4195.

AMA Style

Julia Kelly, Theresa S. Ibáñez, Cristina Santín, Stefan H. Doerr, Marie‐Charlotte Nilsson, Thomas Holst, Anders Lindroth, Natascha Kljun. Boreal forest soil carbon fluxes one year after a wildfire: Effects of burn severity and management. Global Change Biology. 2021; 27 (17):4181-4195.

Chicago/Turabian Style

Julia Kelly; Theresa S. Ibáñez; Cristina Santín; Stefan H. Doerr; Marie‐Charlotte Nilsson; Thomas Holst; Anders Lindroth; Natascha Kljun. 2021. "Boreal forest soil carbon fluxes one year after a wildfire: Effects of burn severity and management." Global Change Biology 27, no. 17: 4181-4195.

Primary research article
Published: 11 March 2021 in Global Change Biology
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Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long‐term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem‐level net BVOC fluxes were measured in the experimental plots using proton‐transfer‐reaction time‐of‐flight mass spectrometry (PTR–ToF–MS). The warming treatment increased monoterpene and isoprene emissions by ≈ 50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~ 50‐75 %) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene, and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interacts and influences BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not only a response to changes in temperature and light intensity, as the circadian clock also affects emission rates.

ACS Style

Nanna Baggesen; Tao Li; Roger Seco; Thomas Holst; Anders Michelsen; Riikka Rinnan. Phenological stage of tundra vegetation controls bidirectional exchange of BVOCs in a climate change experiment on a subarctic heath. Global Change Biology 2021, 27, 2928 -2944.

AMA Style

Nanna Baggesen, Tao Li, Roger Seco, Thomas Holst, Anders Michelsen, Riikka Rinnan. Phenological stage of tundra vegetation controls bidirectional exchange of BVOCs in a climate change experiment on a subarctic heath. Global Change Biology. 2021; 27 (12):2928-2944.

Chicago/Turabian Style

Nanna Baggesen; Tao Li; Roger Seco; Thomas Holst; Anders Michelsen; Riikka Rinnan. 2021. "Phenological stage of tundra vegetation controls bidirectional exchange of BVOCs in a climate change experiment on a subarctic heath." Global Change Biology 27, no. 12: 2928-2944.

Journal article
Published: 12 January 2021 in Environmental and Experimental Botany
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Temperature is one of the key abiotic factors during the life of plants, especially in the Arctic region which is currently experiencing rapid climate change. We evaluated plant traits and environmental variables determining leaf temperature in tundra shrubs and volatile organic compound (VOC) emissions with field measurements on deciduous tundra shrubs, Salix myrsinites and Betula nana, and evergreen Cassiope tetragona and Rhododendron lapponicum. Higher leaf-to-air temperature difference was observed in evergreen, compared to deciduous shrubs. Evergreen shrubs also showed continuously increasing photosynthesis with increasing temperature, suggesting high thermal tolerance. For the deciduous species, the optimum temperature for net photosynthesis was between our measurement temperatures of 24 °C and 38 °C. Air temperature and vapor pressure deficit were the most important variables influencing leaf temperature and VOC emissions in all the studied plants, along with stomatal density and specific leaf area in the deciduous shrubs. Using climate data and emission factors from our measurements, we modelled total seasonal tundra shrub VOC emissions of 0.3–2.3 g m−2 over the main growing season. Our results showed higher-than-expected temperature optima for photosynthesis and VOC emission and demonstrated the relative importance of plant traits and local environments in determining leaf temperature and VOC emissions in a subarctic tundra.

ACS Style

Tihomir Simin; Jing Tang; Thomas Holst; Riikka Rinnan. Volatile organic compound emission in tundra shrubs – Dependence on species characteristics and the near-surface environment. Environmental and Experimental Botany 2021, 184, 104387 .

AMA Style

Tihomir Simin, Jing Tang, Thomas Holst, Riikka Rinnan. Volatile organic compound emission in tundra shrubs – Dependence on species characteristics and the near-surface environment. Environmental and Experimental Botany. 2021; 184 ():104387.

Chicago/Turabian Style

Tihomir Simin; Jing Tang; Thomas Holst; Riikka Rinnan. 2021. "Volatile organic compound emission in tundra shrubs – Dependence on species characteristics and the near-surface environment." Environmental and Experimental Botany 184, no. : 104387.

Research article
Published: 11 November 2020 in Atmospheric Chemistry and Physics
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Ecosystems exchange climate-relevant trace gases with the atmosphere, including volatile organic compounds (VOCs) that are a small but highly reactive part of the carbon cycle. VOCs have important ecological functions and implications for atmospheric chemistry and climate. We measured the ecosystem-level surface–atmosphere VOC fluxes using the eddy covariance technique at a shallow subarctic lake and an adjacent graminoid-dominated fen in northern Sweden during two contrasting periods: the peak growing season (mid-July) and the senescent period post-growing season (September–October). In July, the fen was a net source of methanol, acetaldehyde, acetone, dimethyl sulfide, isoprene, and monoterpenes. All of these VOCs showed a diel cycle of emission with maxima around noon and isoprene dominated the fluxes (93±22 µmol m−2 d−1, mean ± SE). Isoprene emission was strongly stimulated by temperature and presented a steeper response to temperature (Q10=14.5) than that typically assumed in biogenic emission models, supporting the high temperature sensitivity of arctic vegetation. In September, net emissions of methanol and isoprene were drastically reduced, while acetaldehyde and acetone were deposited to the fen, with rates of up to -6.7±2.8 µmol m−2 d−1 for acetaldehyde. Remarkably, the lake was a sink for acetaldehyde and acetone during both periods, with average fluxes up to -19±1.3 µmol m−2 d−1 of acetone in July and up to -8.5±2.3 µmol m−2 d−1 of acetaldehyde in September. The deposition of both carbonyl compounds correlated with their atmospheric mixing ratios, with deposition velocities of -0.23±0.01 and -0.68±0.03 cm s−1 for acetone and acetaldehyde, respectively. Even though these VOC fluxes represented less than 0.5 % and less than 5 % of the CO2 and CH4 net carbon ecosystem exchange, respectively, VOCs alter the oxidation capacity of the atmosphere. Thus, understanding the response of their emissions to climate change is important for accurate prediction of the future climatic conditions in this rapidly warming area of the planet.

ACS Style

Roger Seco; Thomas Holst; Mikkel Sillesen Matzen; Andreas Westergaard-Nielsen; Tao Li; Tihomir Simin; Joachim Jansen; Patrick Crill; Thomas Friborg; Janne Rinne; Riikka Rinnan. Volatile organic compound fluxes in a subarctic peatland and lake. Atmospheric Chemistry and Physics 2020, 20, 13399 -13416.

AMA Style

Roger Seco, Thomas Holst, Mikkel Sillesen Matzen, Andreas Westergaard-Nielsen, Tao Li, Tihomir Simin, Joachim Jansen, Patrick Crill, Thomas Friborg, Janne Rinne, Riikka Rinnan. Volatile organic compound fluxes in a subarctic peatland and lake. Atmospheric Chemistry and Physics. 2020; 20 (21):13399-13416.

Chicago/Turabian Style

Roger Seco; Thomas Holst; Mikkel Sillesen Matzen; Andreas Westergaard-Nielsen; Tao Li; Tihomir Simin; Joachim Jansen; Patrick Crill; Thomas Friborg; Janne Rinne; Riikka Rinnan. 2020. "Volatile organic compound fluxes in a subarctic peatland and lake." Atmospheric Chemistry and Physics 20, no. 21: 13399-13416.

Journal article
Published: 07 April 2020 in Atmosphere
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Willow (Salix spp.) trees are commonly used in short rotation coppices (SRC) to produce renewable energy. However, these plants are also known to emit high concentrations of biogenic volatile organic compounds (BVOCs), which have a large influence on air quality. Many different clones of commercially used Salix varieties exist today, but only a few studies have focused on BVOC emissions from these newer varieties. In this study, four varieties commercially propagated for biofuel production have been studied on a leaf-scale in the southern part of Sweden. The trees had either their first or second growing season, and measurements on BVOC emissions were done during the growing season in 2017 from the end of May to the beginning of September. Isoprene was the dominant emitted compound for all varieties but the average emission amongst varieties varied from 4.00 to 12.66 µg gdw−1 h−1. Average monoterpene (MT) (0.78–1.87 µg gdw−1 h−1) and sesquiterpene (SQT) emission rates (0.22–0.57 µg gdw−1 h−1) differed as well among the varieties. Besides isoprene, other compounds like ocimene, linalool and caryophyllene also showed a response to light but not for all varieties. Younger plants had several times higher emissions of non-isoprenoids (other VOCs) than the corresponding 1-year-old trees. The conclusions from this study show that the choice of variety can have a large impact on the regional BVOC emission budget. Genetics, together with stand age, should be taken into account when modelling BVOC emissions on a regional scale, for example, for air quality assessments.

ACS Style

Tomas Karlsson; Riikka Rinnan; Thomas Holst. Variability of BVOC Emissions from Commercially Used Willow (Salix spp.) Varieties. Atmosphere 2020, 11, 356 .

AMA Style

Tomas Karlsson, Riikka Rinnan, Thomas Holst. Variability of BVOC Emissions from Commercially Used Willow (Salix spp.) Varieties. Atmosphere. 2020; 11 (4):356.

Chicago/Turabian Style

Tomas Karlsson; Riikka Rinnan; Thomas Holst. 2020. "Variability of BVOC Emissions from Commercially Used Willow (Salix spp.) Varieties." Atmosphere 11, no. 4: 356.

Journal article
Published: 17 July 2019 in Atmosphere
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A large portion of atmospheric aerosol particles consists of secondary material produced by oxidation reactions. The relative importance of secondary organic aerosol (SOA) can increase with improved emission regulations. A relatively simple way to study potential particle formation in the atmosphere is by using oxidation flow reactors (OFRs) which simulate atmospheric ageing. Here we report on the first ambient OFR ageing experiment in Europe, coupled with scanning mobility particle sizer (SMPS), aerosol mass spectrometer (AMS) and proton transfer reaction (PTR)-MS measurements. We found that the simulated ageing did not produce any measurable increases in particle mass or number concentrations during the two months of the campaign due to low concentrations of precursors. Losses in the reactor increased with hydroxyl radical (OH) exposure and with increasing difference between ambient and reactor temperatures, indicating fragmentation and evaporation of semivolatile material.

ACS Style

Erik Ahlberg; Stina Ausmeel; Axel Eriksson; Thomas Holst; Tomas Karlsson; William H. Brune; Göran Frank; Pontus Roldin; Adam Kristensson; Birgitta Svenningsson. No Particle Mass Enhancement from Induced Atmospheric Ageing at a Rural Site in Northern Europe. Atmosphere 2019, 10, 408 .

AMA Style

Erik Ahlberg, Stina Ausmeel, Axel Eriksson, Thomas Holst, Tomas Karlsson, William H. Brune, Göran Frank, Pontus Roldin, Adam Kristensson, Birgitta Svenningsson. No Particle Mass Enhancement from Induced Atmospheric Ageing at a Rural Site in Northern Europe. Atmosphere. 2019; 10 (7):408.

Chicago/Turabian Style

Erik Ahlberg; Stina Ausmeel; Axel Eriksson; Thomas Holst; Tomas Karlsson; William H. Brune; Göran Frank; Pontus Roldin; Adam Kristensson; Birgitta Svenningsson. 2019. "No Particle Mass Enhancement from Induced Atmospheric Ageing at a Rural Site in Northern Europe." Atmosphere 10, no. 7: 408.

Letter
Published: 10 June 2019 in Nature Plants
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Plant-emitted volatile organic compounds (VOCs) play fundamental roles in atmospheric chemistry and ecological processes by contributing to aerosol formation1 and mediating species interactions2. Rising temperatures and the associated shifts in vegetation composition have been shown to be the primary drivers of plant VOC emissions in Arctic ecosystems3. Although herbivorous insects also strongly alter plant VOC emissions2, no studies have addressed the impact of herbivory on plant VOC emissions in the Arctic. Here we show that warming dramatically increases the amount, and alters the blend, of VOCs released in response to herbivory. We observed that a tundra ecosystem subjected to warming, by open-top chambers, for 8 or 18 years showed a fourfold increase in leaf area eaten by insect herbivores. Herbivory by autumnal moth (Epirrita autumnata) larvae, and herbivory-mimicking methyl jasmonate application, on the widespread circumpolar dwarf birch (Betula nana) both substantially increased emissions of terpenoids. The long-term warming treatments and mimicked herbivory caused, on average, a two- and fourfold increase in monoterpene emissions, respectively. When combined, emissions increased 11-fold, revealing a strong synergy between warming and herbivory. The synergistic effect was even more pronounced for homoterpene emissions. These findings suggest that, in the rapidly warming Arctic, insect herbivory may be a primary determinant of VOC emissions during periods of active herbivore feeding.

ACS Style

Tao Li; Thomas Holst; Anders Michelsen; Riikka Rinnan. Amplification of plant volatile defence against insect herbivory in a warming Arctic tundra. Nature Plants 2019, 5, 568 -574.

AMA Style

Tao Li, Thomas Holst, Anders Michelsen, Riikka Rinnan. Amplification of plant volatile defence against insect herbivory in a warming Arctic tundra. Nature Plants. 2019; 5 (6):568-574.

Chicago/Turabian Style

Tao Li; Thomas Holst; Anders Michelsen; Riikka Rinnan. 2019. "Amplification of plant volatile defence against insect herbivory in a warming Arctic tundra." Nature Plants 5, no. 6: 568-574.

Journal article
Published: 24 August 2018 in Nature Communications
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Warming in the Arctic accelerates thawing of permafrost-affected soils, which leads to a release of greenhouse gases to the atmosphere. We do not know whether permafrost thaw also releases non-methane volatile organic compounds that can contribute to both negative and positive radiative forcing on climate. Here we show using proton transfer reaction–time of flight–mass spectrometry that substantial amounts of ethanol and methanol and in total 316 organic ions were released from Greenlandic permafrost soils upon thaw in laboratory incubations. We demonstrate that the majority of this release is taken up in the active layer above. In an experiment using 14C-labeled ethanol and methanol, we demonstrate that these compounds are consumed by microorganisms. Our findings highlight that the thawing permafrost soils are not only a considerable source of volatile organic compounds but also that the active layer regulates their release into the atmosphere.

ACS Style

Magnus Kramshøj; Christian Albers; Thomas Holst; Rupert Holzinger; Bo Elberling; Riikka Rinnan. Biogenic volatile release from permafrost thaw is determined by the soil microbial sink. Nature Communications 2018, 9, 3412 .

AMA Style

Magnus Kramshøj, Christian Albers, Thomas Holst, Rupert Holzinger, Bo Elberling, Riikka Rinnan. Biogenic volatile release from permafrost thaw is determined by the soil microbial sink. Nature Communications. 2018; 9 (1):3412.

Chicago/Turabian Style

Magnus Kramshøj; Christian Albers; Thomas Holst; Rupert Holzinger; Bo Elberling; Riikka Rinnan. 2018. "Biogenic volatile release from permafrost thaw is determined by the soil microbial sink." Nature Communications 9, no. 1: 3412.

Research article
Published: 11 July 2018 in PLOS ONE
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Satellite derived normalized difference vegetation index (NDVI) is a common data source for monitoring regional and global ecosystem properties. In dry lands it has contributed to estimation of inter-annual and seasonal vegetation dynamics and phenology. However, due to the spectral properties of NDVI it can be affected by clouds which can introduce missing data in the time series. Remotely sensed soil moisture has in contrast to NDVI the benefit of being unaffected by clouds due to the measurements being made in the microwave domain. There is therefore a potential in combining the remotely sensed NDVI with remotely sensed soil moisture to enhance the quality and estimate the missing data. We present a step towards the usage of remotely sensed soil moisture for estimation of savannah NDVI. This was done by evaluating the European Space Agency (ESA) Climate Change Initiative (CCI) soil moisture and three of its individual products with respect to their relative performance. The individual products are from the advance scatterometer (ASCAT), Soil Moisture and Ocean Salinity (SMOS), and the Land Parameter Retrieval Model-Advanced Microwave Scanning Radiometer-Earth Observing System (LPRM-AMSR-E). Each dataset was used to simulate NDVI, which was subsequently compared to remotely sensed NDVI from MODIS. Differences in their ability to estimate NDVI indicated that, on average, CCI soil moisture differs from its individual products by showing a higher average correlation with measured NDVI. Overall NDVI modelled from CCI soil moisture gave an average correlation of 0.81 to remotely sensed NDVI which indicates its potential to be used to estimate seasonal variations in savannah NDVI. Our result shows promise for further development in using CCI soil moisture to estimate NDVI. The modelled NDVI can potentially be used together with other remotely sensed vegetation datasets to enhance the phenological information that can be acquired, thereby, improving the estimates of savannah vegetation phenology.

ACS Style

Niklas Boke-Olén; Jonas Ardö; Lars Eklundh; Thomas Holst; Veiko Lehsten. Remotely sensed soil moisture to estimate savannah NDVI. PLOS ONE 2018, 13, e0200328 .

AMA Style

Niklas Boke-Olén, Jonas Ardö, Lars Eklundh, Thomas Holst, Veiko Lehsten. Remotely sensed soil moisture to estimate savannah NDVI. PLOS ONE. 2018; 13 (7):e0200328.

Chicago/Turabian Style

Niklas Boke-Olén; Jonas Ardö; Lars Eklundh; Thomas Holst; Veiko Lehsten. 2018. "Remotely sensed soil moisture to estimate savannah NDVI." PLOS ONE 13, no. 7: e0200328.

Journal article
Published: 19 June 2018 in Biogeosciences
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Isoprene is a highly reactive volatile organic compound emitted by vegetation, known to be a precursor of secondary organic aerosols and to enhance tropospheric ozone formation under polluted conditions. Isoprene emissions respond strongly to changes in meteorological parameters such as temperature and solar radiation. In addition, the increasing CO2 concentration has a dual effect, as it causes both a direct emission inhibition as well as an increase in biomass through fertilization. In this study we used the MEGAN (Model of Emissions of Gases and Aerosols from Nature) emission model coupled with the MOHYCAN (Model of HYdrocarbon emissions by the CANopy) canopy model to calculate the isoprene fluxes emitted by vegetation in the recent past (1979–2014) and in the future (2070–2099) over Europe at a resolution of 0.1∘×0.1∘. As a result of the changing climate, modeled isoprene fluxes increased by 1.1 % yr−1 on average in Europe over 1979–2014, with the strongest trends found over eastern Europe and European Russia, whereas accounting for the CO2 inhibition effect led to reduced emission trends (0.76 % yr−1). Comparisons with field campaign measurements at seven European sites suggest that the MEGAN–MOHYCAN model provides a reliable representation of the temporal variability of the isoprene fluxes over timescales between 1 h and several months. For the 1979–2014 period the model was driven by the ECMWF ERA-Interim reanalysis fields, whereas for the comparison of current with projected future emissions, we used meteorology simulated with the ALARO regional climate model. Depending on the representative concentration pathway (RCP) scenarios for greenhouse gas concentration trajectories driving the climate projections, isoprene emissions were found to increase by +7 % (RCP2.6), +33 % (RCP4.5), and +83 % (RCP8.5), compared to the control simulation, and even stronger increases were found when considering the potential impact of CO2 fertilization: +15 % (RCP2.6), +52 % (RCP4.5), and +141 % (RCP8.5). However, the inhibitory CO2 effect goes a long way towards canceling these increases. Based on two distinct parameterizations, representing strong or moderate inhibition, the projected emissions accounting for all effects were estimated to be 0–17 % (strong inhibition) and 11–65 % (moderate inhibition) higher than in the control simulation. The difference obtained using the two CO2 parameterizations underscores the large uncertainty associated to this effect.

ACS Style

Maite Bauwens; Trissevgeni Stavrakou; Jean-François Müller; Bert Van Schaeybroeck; Lesley De Cruz; Rozemien De Troch; Olivier Giot; Rafiq Hamdi; Piet Termonia; Quentin Laffineur; Crist Amelynck; Niels Schoon; Bernard Heinesch; Thomas Holst; Almut Arneth; Reinhart Ceulemans; Arturo Sanchez-Lorenzo; Alex Guenther. Recent past (1979–2014) and future (2070–2099) isoprene fluxes over Europe simulated with the MEGAN–MOHYCAN model. Biogeosciences 2018, 15, 3673 -3690.

AMA Style

Maite Bauwens, Trissevgeni Stavrakou, Jean-François Müller, Bert Van Schaeybroeck, Lesley De Cruz, Rozemien De Troch, Olivier Giot, Rafiq Hamdi, Piet Termonia, Quentin Laffineur, Crist Amelynck, Niels Schoon, Bernard Heinesch, Thomas Holst, Almut Arneth, Reinhart Ceulemans, Arturo Sanchez-Lorenzo, Alex Guenther. Recent past (1979–2014) and future (2070–2099) isoprene fluxes over Europe simulated with the MEGAN–MOHYCAN model. Biogeosciences. 2018; 15 (12):3673-3690.

Chicago/Turabian Style

Maite Bauwens; Trissevgeni Stavrakou; Jean-François Müller; Bert Van Schaeybroeck; Lesley De Cruz; Rozemien De Troch; Olivier Giot; Rafiq Hamdi; Piet Termonia; Quentin Laffineur; Crist Amelynck; Niels Schoon; Bernard Heinesch; Thomas Holst; Almut Arneth; Reinhart Ceulemans; Arturo Sanchez-Lorenzo; Alex Guenther. 2018. "Recent past (1979–2014) and future (2070–2099) isoprene fluxes over Europe simulated with the MEGAN–MOHYCAN model." Biogeosciences 15, no. 12: 3673-3690.

Journal article
Published: 01 December 2017 in Atmospheric Environment
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Norway spruce (Picea abies) is one of the dominant tree species in the European boreal zone with the capacity to grow over large areas within Europe. It is an important emitter of biogenic volatile organic compounds (BVOCs), which can act as precursors of photochemical smog and ozone and contribute to the formation and growth of secondary organic aerosols (SOA) in the atmosphere.Isoprenoid emissions were measured from Norway spruce trees at seven different sites, distributed from Ljubljana in Slovenia to Piikkiö in Finland. Four of the sites were part of a network of genetically identical spruce trees and contained two separate provenances. The remaining three sites were part of other networks which have been used to conduct studies in the European boreal zone.There were minimal differences in the standardized emission rates between sites and across latitudes. The emission profile differed between provenances and sites, but there were not any distinct patterns which could be connected to a change in latitude. By using genetically identical trees and comparing the emission rates between sites and with genetically different trees, it was observed that the emission patterns were mostly influenced by genetics. But in order to confirm this possible stability of the relative emission profile based on genetics, more studies need to be performed.The effects of branch height, season and variation between years on observed emission pattern variations were also investigated. There were indications of potential influences of all three factors. However, due to different experimental setups between measurement campaigns, it is difficult to draw any robust conclusions

ACS Style

Ylva van Meeningen; Min Wang; Tomas Karlsson; Ana Seifert; Guy Schurgers; Riikka Rinnan; Thomas Holst. Isoprenoid emission variation of Norway spruce across a European latitudinal transect. Atmospheric Environment 2017, 170, 45 -57.

AMA Style

Ylva van Meeningen, Min Wang, Tomas Karlsson, Ana Seifert, Guy Schurgers, Riikka Rinnan, Thomas Holst. Isoprenoid emission variation of Norway spruce across a European latitudinal transect. Atmospheric Environment. 2017; 170 ():45-57.

Chicago/Turabian Style

Ylva van Meeningen; Min Wang; Tomas Karlsson; Ana Seifert; Guy Schurgers; Riikka Rinnan; Thomas Holst. 2017. "Isoprenoid emission variation of Norway spruce across a European latitudinal transect." Atmospheric Environment 170, no. : 45-57.

Journal article
Published: 15 September 2017 in Biogeosciences
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Light is an important environmental factor controlling biogenic volatile organic compound (BVOC) emissions, but in natural conditions its impact is hard to separate from other influential factors such as temperature. We studied the light response of foliar BVOC emissions, photosynthesis and stomatal conductance on three common European tree species, namely English oak (Quercus robur), European beech (Fagus sylvatica) and two provenances of Norway spruce (Picea abies) in Taastrup, Denmark. Leaf scale measurements were performed on the lowest positioned branches of the tree in July 2015. Light intensity was increased in four steps (0, 500, 1000 and 1500 µmol m−2 s−1), whilst other chamber conditions such as temperature, humidity and CO2 levels were fixed. Whereas the emission rate differed between individuals of the same species, the relative contributions of compounds to the total isoprenoid emission remained similar. Whilst some compounds were species specific, the compounds α-pinene, camphene, 3-carene, limonene and eucalyptol were emitted by all of the measured tree species. Some compounds, like isoprene and sabinene, showed an increasing emission response with increasing light intensity, whereas other compounds, like camphene, had no significant emission response to light for most of the measured trees. English oak and European beech showed high light-dependent emission fractions from isoprene and sabinene, but other emitted compounds were light independent. For the two provenances of Norway spruce, the compounds α-pinene, 3-carene and eucalyptol showed high light-dependent fractions for many of the measured trees. This study highlights differences between compound emissions in their response to a change in light and a possible light independence for certain compounds, which might be valid for a wider range of tree species. This information could be of importance when improving emission models and to further emphasize the discussion regarding light or temperature dependencies for individual compounds across species.

ACS Style

Ylva van Meeningen; Guy Schurgers; Riikka Rinnan; Thomas Holst. Isoprenoid emission response to changing light conditions of English oak, European beech and Norway spruce. Biogeosciences 2017, 14, 4045 -4060.

AMA Style

Ylva van Meeningen, Guy Schurgers, Riikka Rinnan, Thomas Holst. Isoprenoid emission response to changing light conditions of English oak, European beech and Norway spruce. Biogeosciences. 2017; 14 (18):4045-4060.

Chicago/Turabian Style

Ylva van Meeningen; Guy Schurgers; Riikka Rinnan; Thomas Holst. 2017. "Isoprenoid emission response to changing light conditions of English oak, European beech and Norway spruce." Biogeosciences 14, no. 18: 4045-4060.

Journal article
Published: 01 July 2017 in Atmospheric Environment
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The atmospheric organic aerosol is a tremendously complex system in terms of chemical content. Models generally treat the mixtures as ideal, something which has been questioned owing to model-measurement discrepancies. We used an oxidation flow reactor to produce secondary organic aerosol (SOA) mixtures containing oxidation products of biogenic (α-pinene, myrcene and isoprene) and anthropogenic (m-xylene) volatile organic compounds (VOCs). The resulting volume concentration and chemical composition was measured using a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), respectively. The SOA mass yield of the mixtures was compared to a partitioning model constructed from single VOC experiments. The single VOC SOA mass yields with no wall-loss correction applied are comparable to previous experiments. In the mixtures containing myrcene a higher yield than expected was produced. We attribute this to an increased condensation sink, arising from myrcene producing a significantly higher number of nucleation particles compared to the other precursors. Isoprene did not produce much mass in single VOC experiments but contributed to the mass of the mixtures. The effect of high concentrations of isoprene on the OH exposure was found to be small, even at OH reactivities that previously have been reported to significantly suppress OH exposures in oxidation flow reactors. Furthermore, isoprene shifted the particle size distribution of mixtures towards larger sizes, which could be due to a change in oxidant dynamics inside the reactor

ACS Style

Erik Ahlberg; John Falk; Axel Eriksson; Thomas Holst; William H. Brune; Adam Kristensson; Pontus Roldin; Birgitta Svenningsson. Secondary organic aerosol from VOC mixtures in an oxidation flow reactor. Atmospheric Environment 2017, 161, 210 -220.

AMA Style

Erik Ahlberg, John Falk, Axel Eriksson, Thomas Holst, William H. Brune, Adam Kristensson, Pontus Roldin, Birgitta Svenningsson. Secondary organic aerosol from VOC mixtures in an oxidation flow reactor. Atmospheric Environment. 2017; 161 ():210-220.

Chicago/Turabian Style

Erik Ahlberg; John Falk; Axel Eriksson; Thomas Holst; William H. Brune; Adam Kristensson; Pontus Roldin; Birgitta Svenningsson. 2017. "Secondary organic aerosol from VOC mixtures in an oxidation flow reactor." Atmospheric Environment 161, no. : 210-220.

Journal article
Published: 04 November 2016 in Biogeosciences
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English oak (Quercus robur) and European beech (Fagus sylvatica) are amongst the most common tree species growing in Europe, influencing the annual biogenic volatile organic compound (BVOC) budget in this region. Studies have shown great variability in the emissions from these tree species, originating from both genetic variability and differences in climatic conditions between study sites. In this study, we examine the emission patterns for English oak and European beech in genetically identical individuals and the potential variation within and between sites. Leaf scale BVOC emissions, net assimilation rates and stomatal conductance were measured at the International Phenological Garden sites of Ljubljana (Slovenia), Grafrath (Germany) and Taastrup (Denmark). Sampling was conducted during three campaigns between May and July 2014. Our results show that English oak mainly emitted isoprene whilst European beech released monoterpenes. The relative contribution of the most emitted compounds from the two species remained stable across latitudes. The contribution of isoprene for English oak from Grafrath and Taastrup ranged between 92 and 97 % of the total BVOC emissions, whilst sabinene and limonene for European beech ranged from 30.5 to 40.5 and 9 to 15 % respectively for all three sites. The relative contribution of isoprene for English oak at Ljubljana was lower (78 %) in comparison to the other sites, most likely caused by frost damage in early spring. The variability in total leaf-level emission rates from the same site was small, whereas there were greater differences between sites. These differences were probably caused by short-term weather events and plant stress. A difference in age did not seem to affect the emission patterns for the selected trees. This study highlights the significance of within-genotypic variation of BVOC emission capacities for English oak and European beech, the influence of climatic variables such as temperature and light on emission intensities and the potential stability in relative compound contribution across a latitudinal gradient.

ACS Style

Ylva van Meeningen; Guy Schurgers; Riikka Rinnan; Thomas Holst. BVOC emissions from English oak (Quercus robur) and European beech (Fagus sylvatica) along a latitudinal gradient. Biogeosciences 2016, 13, 6067 -6080.

AMA Style

Ylva van Meeningen, Guy Schurgers, Riikka Rinnan, Thomas Holst. BVOC emissions from English oak (Quercus robur) and European beech (Fagus sylvatica) along a latitudinal gradient. Biogeosciences. 2016; 13 (21):6067-6080.

Chicago/Turabian Style

Ylva van Meeningen; Guy Schurgers; Riikka Rinnan; Thomas Holst. 2016. "BVOC emissions from English oak (Quercus robur) and European beech (Fagus sylvatica) along a latitudinal gradient." Biogeosciences 13, no. 21: 6067-6080.

Journal article
Published: 05 September 2016 in Meteorologische Zeitschrift
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ACS Style

Ylva Persson; Guy Schurgers; Anna Ekberg; Thomas Holst. Effects of intra-genotypic variation, variance with height and time of season on BVOC emissions. Meteorologische Zeitschrift 2016, 25, 377 -388.

AMA Style

Ylva Persson, Guy Schurgers, Anna Ekberg, Thomas Holst. Effects of intra-genotypic variation, variance with height and time of season on BVOC emissions. Meteorologische Zeitschrift. 2016; 25 (4):377-388.

Chicago/Turabian Style

Ylva Persson; Guy Schurgers; Anna Ekberg; Thomas Holst. 2016. "Effects of intra-genotypic variation, variance with height and time of season on BVOC emissions." Meteorologische Zeitschrift 25, no. 4: 377-388.

Research article
Published: 29 April 2016 in PLOS ONE
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Savannah regions are predicted to undergo changes in precipitation patterns according to current climate change projections. This change will affect leaf phenology, which controls net primary productivity. It is of importance to study this since savannahs play an important role in the global carbon cycle due to their areal coverage and can have an effect on the food security in regions that depend on subsistence farming. In this study we investigate how soil moisture, mean annual precipitation, and day length control savannah phenology by developing a lagged time series model. The model uses climate data for 15 flux tower sites across four continents, and normalized difference vegetation index from satellite to optimize a statistical phenological model. We show that all three variables can be used to estimate savannah phenology on a global scale. However, it was not possible to create a simplified savannah model that works equally well for all sites on the global scale without inclusion of more site specific parameters. The simplified model showed no bias towards tree cover or between continents and resulted in a cross-validated r2 of 0.6 and root mean squared error of 0.1. We therefore expect similar average results when applying the model to other savannah areas and further expect that it could be used to estimate the productivity of savannah regions.

ACS Style

Niklas Boke-Olén; Veiko Lehsten; Jonas Ardö; Jason Beringer; Lars Eklundh; Thomas Holst; Elmar Veenendaal; Torbern Tagesson. Estimating and Analyzing Savannah Phenology with a Lagged Time Series Model. PLOS ONE 2016, 11, e0154615 .

AMA Style

Niklas Boke-Olén, Veiko Lehsten, Jonas Ardö, Jason Beringer, Lars Eklundh, Thomas Holst, Elmar Veenendaal, Torbern Tagesson. Estimating and Analyzing Savannah Phenology with a Lagged Time Series Model. PLOS ONE. 2016; 11 (4):e0154615.

Chicago/Turabian Style

Niklas Boke-Olén; Veiko Lehsten; Jonas Ardö; Jason Beringer; Lars Eklundh; Thomas Holst; Elmar Veenendaal; Torbern Tagesson. 2016. "Estimating and Analyzing Savannah Phenology with a Lagged Time Series Model." PLOS ONE 11, no. 4: e0154615.

Journal article
Published: 27 April 2016 in Atmospheric Chemistry and Physics
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Disproportional warming in the northern high latitudes and large carbon stocks in boreal and (sub)arctic ecosystems have raised concerns as to whether substantial positive climate feedbacks from biogeochemical process responses should be expected. Such feedbacks occur when increasing temperatures lead, for example, to a net release of CO2 or CH4. However, temperature-enhanced emissions of biogenic volatile organic compounds (BVOCs) have been shown to contribute to the growth of secondary organic aerosol (SOA), which is known to have a negative radiative climate effect. Combining measurements in Eastern Siberia with model-based estimates of vegetation and permafrost dynamics, BVOC emissions, and aerosol growth, we assess here possible future changes in ecosystem CO2 balance and BVOC–SOA interactions and discuss these changes in terms of possible climate effects. Globally, the effects of changes in Siberian ecosystem CO2 balance and SOA formation are small, but when concentrating on Siberia and the Northern Hemisphere the negative forcing from changed aerosol direct and indirect effects become notable – even though the associated temperature response would not necessarily follow a similar spatial pattern. While our analysis does not include other important processes that are of relevance for the climate system, the CO2 and BVOC–SOA interplay serves as an example for the complexity of the interactions between emissions and vegetation dynamics that underlie individual terrestrial processes and highlights the importance of addressing ecosystem–climate feedbacks in consistent, process-based model frameworks.

ACS Style

Almut Arneth; Risto Makkonen; Stefan Olin; Pauli Paasonen; Thomas Holst; Maija K. Kajos; Markku Kulmala; Trofim Maximov; Paul A. Miller; Guy Schurgers. Future vegetation–climate interactions in Eastern Siberia: an assessment of the competing effects of CO2 and secondary organic aerosols. Atmospheric Chemistry and Physics 2016, 16, 5243 -5262.

AMA Style

Almut Arneth, Risto Makkonen, Stefan Olin, Pauli Paasonen, Thomas Holst, Maija K. Kajos, Markku Kulmala, Trofim Maximov, Paul A. Miller, Guy Schurgers. Future vegetation–climate interactions in Eastern Siberia: an assessment of the competing effects of CO2 and secondary organic aerosols. Atmospheric Chemistry and Physics. 2016; 16 (8):5243-5262.

Chicago/Turabian Style

Almut Arneth; Risto Makkonen; Stefan Olin; Pauli Paasonen; Thomas Holst; Maija K. Kajos; Markku Kulmala; Trofim Maximov; Paul A. Miller; Guy Schurgers. 2016. "Future vegetation–climate interactions in Eastern Siberia: an assessment of the competing effects of CO2 and secondary organic aerosols." Atmospheric Chemistry and Physics 16, no. 8: 5243-5262.

Research article
Published: 09 July 2015 in Atmospheric Chemistry and Physics
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Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be taken of the rich information content of micrometeorological flux measurements.

ACS Style

G. Wohlfahrt; C. Amelynck; Christof Ammann; A. Arneth; I. Bamberger; A. H. Goldstein; Lianhong Gu; A. Guenther; A. Hansel; B. Heinesch; Thomas Holst; L. Hörtnagl; T. Karl; Q. Laffineur; A. Neftel; K. McKinney; J. W. Munger; S. G. Pallardy; Gunnar Schade; R. Seco; N. Schoon. An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements. Atmospheric Chemistry and Physics 2015, 15, 7413 -7427.

AMA Style

G. Wohlfahrt, C. Amelynck, Christof Ammann, A. Arneth, I. Bamberger, A. H. Goldstein, Lianhong Gu, A. Guenther, A. Hansel, B. Heinesch, Thomas Holst, L. Hörtnagl, T. Karl, Q. Laffineur, A. Neftel, K. McKinney, J. W. Munger, S. G. Pallardy, Gunnar Schade, R. Seco, N. Schoon. An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements. Atmospheric Chemistry and Physics. 2015; 15 (13):7413-7427.

Chicago/Turabian Style

G. Wohlfahrt; C. Amelynck; Christof Ammann; A. Arneth; I. Bamberger; A. H. Goldstein; Lianhong Gu; A. Guenther; A. Hansel; B. Heinesch; Thomas Holst; L. Hörtnagl; T. Karl; Q. Laffineur; A. Neftel; K. McKinney; J. W. Munger; S. G. Pallardy; Gunnar Schade; R. Seco; N. Schoon. 2015. "An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements." Atmospheric Chemistry and Physics 15, no. 13: 7413-7427.

Journal article
Published: 09 December 2013 in Atmospheric Chemistry and Physics
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We investigated atmospheric aerosol particle dynamics in a boreal forest zone in northern Scandinavia. We used aerosol number size distribution data measured with either a differential mobility particle sizer (DMPS) or scanning mobility particle sizer (SMPS) at three stations (Värriö, Pallas and Abisko), and combined these data with the HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) air mass trajectory analysis. We compared three approaches: analysis of new particle formation events, investigation of aerosol particle number size distributions during the air mass transport from the ocean to individual stations with different overland transport times, and analysis of changes in aerosol particle number size distributions during the air mass transport from one measurement station to another. Aitken-mode particles were found to have apparent average growth rates of 0.6–0.7 nm h−1 when the air masses traveled over land. Particle growth rates during the new particle formation (NPF) events were 3–6 times higher than the apparent particle growth during the summer period. When comparing aerosol dynamics for different overland transport times between the different stations, no major differences were found, except that in Abisko the NPF events were observed to take place in air masses with shorter overland times than at the other stations. We speculate that this is related to the meteorological differences along the paths of air masses caused by the land surface topology. When comparing air masses traveling in an east-to-west direction with those traveling in a west-to-east direction, clear differences in the aerosol dynamics were seen. Our results suggest that the condensation growth has an important role in aerosol dynamics even when NPF is not evident.

ACS Style

R. Väänänen; E.-M. Kyrö; T. Nieminen; N. Kivekäs; H. Junninen; A. Virkkula; M. Dal Maso; H. Lihavainen; Y. Viisanen; B. Svenningsson; T. Holst; A. Arneth; P. P. Aalto; M. Kulmala; V.-M. Kerminen. Analysis of particle size distribution changes between three measurement sites in northern Scandinavia. Atmospheric Chemistry and Physics 2013, 13, 11887 -11903.

AMA Style

R. Väänänen, E.-M. Kyrö, T. Nieminen, N. Kivekäs, H. Junninen, A. Virkkula, M. Dal Maso, H. Lihavainen, Y. Viisanen, B. Svenningsson, T. Holst, A. Arneth, P. P. Aalto, M. Kulmala, V.-M. Kerminen. Analysis of particle size distribution changes between three measurement sites in northern Scandinavia. Atmospheric Chemistry and Physics. 2013; 13 (23):11887-11903.

Chicago/Turabian Style

R. Väänänen; E.-M. Kyrö; T. Nieminen; N. Kivekäs; H. Junninen; A. Virkkula; M. Dal Maso; H. Lihavainen; Y. Viisanen; B. Svenningsson; T. Holst; A. Arneth; P. P. Aalto; M. Kulmala; V.-M. Kerminen. 2013. "Analysis of particle size distribution changes between three measurement sites in northern Scandinavia." Atmospheric Chemistry and Physics 13, no. 23: 11887-11903.

Journal article
Published: 15 July 2013 in Biogeosciences
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While emissions of many biogenic volatile organic compounds (BVOCs), such as terpenoids, have been studied quite intensively in North American and Scandinavian boreal forests, the vast Siberian boreal forests have remained largely unexplored by experimental emission studies. In this study the shoot-scale terpenoid emission rates from two mature Larix cajanderi trees growing in their natural habitat in eastern Siberia were measured at the Spasskaya Pad flux measurement site (62°15´18.4" N, 129°37´07.9" E) located on the western bank of the Lena river. The measurements were conducted during three campaigns: 3–24 June, 8–26 July, and 14–30 August, in the summer of 2009. A dynamic flow-through enclosure technique was applied for adsorbent sampling, and the samples were analysed offline with a gas chromatograph. Between 29 and 45 samples were taken from each shoot during all three campaigns. Seven different monoterpenes, six different sesquiterpenes, linalool isoprene, and 2-methyl-3-buten-2-ol (MBO) were identified. The monthly median value of the total terpenoid emissions varied between 0.006 and 10.6 μg gdw−1 h−1. The emissions were dominated by monoterpenes, which constituted between 61 and 92% of the total emissions. About half of the monoterpene emissions were comprised of Δ 3-carene; α- and β-pinene had significant emissions as well. Linalool emissions were also substantial, comprising 3–37% of the total emissions, especially in June. Sesquiterpenes accounted for less than 3% and isoprene less than 1% of the total emissions. Based on the measured emission rates, the relative atmospheric concentration of each compound was estimated. Monoterpenes were the species with the highest relative concentration, while linalool and sesquiterpenes had a notably smaller contribution to the estimated atmospheric concentration than to the emission rates. A temperature-dependent pool algorithm with a constant β (0.09 °C−1 for monoterpenes and 0.143 °C−1 for sesquiterpenes) was used to normalize the measured emission data. For monoterpenes the emission potential varied between 0.5 and 18.5 μg gdw−1 h−1 and for sesquiterpenes between 0.02 and 0.4 μg gdw−1 h−1.

ACS Style

M. K. Kajos; H. Hakola; Thomas Holst; T. Nieminen; V. Tarvainen; T. Maximov; T. Petäjä; A. Arneth; J. Rinne. Terpenoid emissions from fully grown east Siberian Larix cajanderi trees. Biogeosciences 2013, 10, 4705 -4719.

AMA Style

M. K. Kajos, H. Hakola, Thomas Holst, T. Nieminen, V. Tarvainen, T. Maximov, T. Petäjä, A. Arneth, J. Rinne. Terpenoid emissions from fully grown east Siberian Larix cajanderi trees. Biogeosciences. 2013; 10 (7):4705-4719.

Chicago/Turabian Style

M. K. Kajos; H. Hakola; Thomas Holst; T. Nieminen; V. Tarvainen; T. Maximov; T. Petäjä; A. Arneth; J. Rinne. 2013. "Terpenoid emissions from fully grown east Siberian Larix cajanderi trees." Biogeosciences 10, no. 7: 4705-4719.