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Biogenic volatile organic compound (BVOC) emissions from trees subjected to biotic stress are higher compared to healthy trees, and they may also have a different compound composition. This in turn affects atmospheric chemistry and can lead to either positive or negative feedback to the climate. Climate change favors the abundance of the European spruce bark beetle (Ips typographus) which attacks the bark of Norway spruce (Picea abies) trees, causing induced BVOC emissions from the trees as a response to the insect stress. Here, results are reported from a study analyzing the difference in emission rates between healthy and bark-beetle-infested Norway spruce trees, changes in emission rates over time since the infestation started, and differences in emission rates from bark-beetle-drilled entry and exit holes. Bark chamber measurements on both healthy and infested trees were performed during the summer of 2019 at Hyltemossa and Norunda research stations in Sweden. The measurements showed that induced BVOC emissions following the bark beetle infestation were dominated by entry hole emissions in the early growing season and exit hole emissions in the later season. The results showed a significant difference in emission rates between healthy and infested trees during both seasons. The seasonal average standardized BVOC emission rate of healthy trees was 32 ± 52 µg m−2 h−1 (mean ± standard deviation), while the average standardized BVOC emission rates of infested trees were 6700 ± 6900 and 2000 ± 1300 µg m−2 h−1 during the early and late season respectively. BVOC emission rates were highest at the start of the infestation and decreased exponentially with time, showing induced emission rates for up to 1 year after which the emission rates were similar to those from healthy bark. Constitutive needle emission rates from healthy trees were found to be 11 times higher than bark emissions from healthy trees. However, when Norway spruce trees were infested, the bark emission rates were instead 6 to 20 times higher than the needle emissions, causing substantial increases in the total tree BVOC emission rate. This could lead to high impacts on atmospheric processes, specifically the formation of secondary organic aerosols, which have a higher yield from some monoterpene compounds, which increased from infested trees.

The ecosystem-atmosphere flux of biogenic volatile organic compounds (BVOCs) has important impacts on tropospheric oxidative capacity and the formation of secondary organic aerosols, influencing air quality and climate. Here we present within-canopy measurements of a set of dominant BVOCs in a managed spruce- and pine-dominated boreal forest located at the ICOS station Norunda in Sweden, collected using proton transfer reaction mass spectrometry (PTR-MS) during 2014–2016, and vertical emission profiles derived from these data. Ozone concentrations were simultaneously measured in conjunction with these PTR-MS measurements. The main BVOCs investigated with the PTR-MS were isoprene, monoterpenes, methanol, acetaldehyde, and acetone. The distribution of BVOC sources and sinks in the forest canopy was explored using Lagrangian dispersion matrix methods, in particular continuous near-field theory. The forest canopy was found to contribute ca. 86 % to the total monoterpene emission in summertime, whereas the below-canopy and canopy emission was comparable (ca. 42 % and 58 % respectively) during the autumn period. This result indicates that boreal forest litter and other below-canopy emitters are a principle source for total forest monoterpene emissions during autumn months. During night, our results for methanol, acetone, and acetaldehyde seasonally present strong sinks in the forest canopy, especially in the autumn, likely due to the nighttime formation of dew on vegetation surfaces.

Wildfires have been effectively suppressed in the managed boreal forests of Fennoscandia for over a century. However, recent extremely hot and dry summers have highlighted the vulnerability of these forests to increasing wildfire frequency as a result of climate change. The carbon stored by managed forests plays a key role in many national climate mitigation strategies and more data is needed to assess how forest management shapes the carbon balance of these forests, including those recovering from wildfire. We established two eddy covariance towers in the area burnt by the Ljusdal fire, which affected over 9000 ha during the extreme 2018 wildfire season in Sweden. The two towers measured CO2 fluxes during the first four growing seasons after the fire at two Pinus sylvestris stands with contrasting fire impacts and forest management schemes. At one site, a mature stand had survived low severity fire but was then salvage-logged and reseeded (6 months after the fire), whilst the other site represented a young stand that was killed by high severity fire and replanted with Pinus sylvestris seedlings (2 years after the fire). After the fire, both sites were net CO2 sources at the annual scale. However, the site with dead young trees and replanted seedlings showed a faster recovery towards becoming a CO2 sink, with days of net CO2 uptake during the peak of the growing season three years after the fire. Preliminary results suggest that similar magnitudes of carbon were emitted as CO2 in the first 4 years after the fire compared to the carbon emitted during the fire itself, underlining the importance of monitoring forest CO2 fluxes and the impacts of management decisions during the initial post-fire years.

AIMS: Clinicians and regulatory authorities are placing increasing emphasis on health-related quality of life (HRQoL) and health utilities when evaluating therapeutic efficacy of new agents. We assessed health utility values in the Semaglutide Treatment Effect in People with obesity (STEP) trials.MATERIALS AND METHODS: The STEP 1-4 phase 3a, 68-week, double-blind randomized controlled trials assessed the efficacy and safety of semaglutide 2.4 mg versus placebo in individuals with BMI ≥30 kg/m2 or BMI ≥27 kg/m2 and ≥1 co-morbidity (STEP 1, 3 and 4), or BMI ≥27 kg/m2 and type 2 diabetes (STEP 2). Patients received lifestyle intervention plus intensive behavioural therapy in STEP 3. HRQoL was assessed using the Short Form 36-item Health Survey version 2 (SF-36v2) at baseline and week 68. Scores were converted into Short Form Six-Dimension version 2 (SF-6Dv2) utility scores or mapped onto the European Quality of Life Five-Dimension Three-Level (EQ-5D-3L) utility index using UK health utility weights.RESULTS: At week 68, semaglutide 2.4 mg was associated with minor health utility score improvements from baseline (all trials), while scores for placebo typically decreased. SF-6Dv2 treatment differences by week 68 for semaglutide versus placebo were significant in STEP 1 and 4 (p≤0.001), but not STEP 2 or 3. EQ-5D-3L treatment differences by week 68 for semaglutide versus placebo were significant in STEP 1, 2 and 4 (pCONCLUSIONS: Semaglutide 2.4 mg was associated with improvement in health utility scores compared with placebo, reaching statistical significance in STEP 1, 2 and 4. This article is protected by copyright. All rights reserved.

Purpose The correlation between body mass index (BMI) and utility in patients with overweight or obesity was assessed using health-related quality of life (HRQoL) data collected in two weight-loss interventional studies, SCALE and STEP 1. Methods Short-Form Health Survey 36-Item (SF-36) scores from SCALE and STEP 1 were mapped to EuroQoL-5 dimensions-3 levels (EQ-5D-3L) using an established algorithm to derive utilities for the UK. SF-36 scores from STEP 1 were converted into Short-Form six-dimensions (SF-6D) utilities for Portugal, using the tool developed by the University of Sheffield. Correlations between utility scores and BMI at baseline were assessed by multiple linear regression analyses, controlling for demographic and clinical parameters. Results Higher baseline BMI was correlated with lower EQ-5D-3L/SF-6D utilities in all analyses, although the correlation was nonsignificant. Assuming linearity between BMI ranges 30–40 kg/m2, a unit increase predicted a utility loss of − 0.0041 and − 0.0031 on EQ-5D-3L for males and females, respectively, in SCALE, − 0.0039 and − 0.0047 in STEP 1, and − 0.0027 and − 0.002 on SF-6D males and females, respectively. Presence of hypertension and older age were significantly negatively correlated with SCALE EQ-5D-3L. Age, presence of coronary artery diseases (CADs) and previous smoking were significantly negatively correlated with STEP 1 EQ-5D-3L. Only presence of CADs was significantly negatively correlated with STEP 1 SF-6D. Males had significantly higher utilities compared with females in the UK analyses. Conclusion These findings are useful to inform cost-effectiveness analyses in obesity whereby multiple factors, along with BMI, are used to calculate quality-adjusted life-years.

Emissions of biogenic volatile organic compound (BVOC) from the bark of Norway spruce (Picea abies) trees can be affected by stress, such as infestation of spruce bark beetles (Ips typographus). We studied the difference in emission rates from healthy spruce bark and infested spruce bark, the influence of time since spruce bark beetle infestation started and the difference in emission rates from bark beetle drilled entry holes and exit holes. Bark chamber measurements on both healthy trees and infested trees were performed during the summer of 2019 at two sites in Sweden. To consider the seasonal pattern of the spruce bark beetle, we divided the emission rates from infested trees into two seasons, an early season dominated by entry holes and a late season with mainly exit holes. Our findings show a significant difference in emission rates from healthy and infested trees, independent of season. The seasonal average standardized emission rate from healthy trees was 31.89 ± 51.67 μg m-2 h-1 (mean ± standard deviation), while the average standardized emission rates from infested trees were 6385 μg m-2 h-1 and 2102 μg m-2 h-1 during early and late season respectively. We also found an exponentially decreasing relationship with BVOC emission rates and time since infestation started where the emission rates reached the same level as the constitutive BVOC emission rates from bark after around one year. When comparing bark monoterpene BVOC emission rates with emission rates from needles, we found that the constitutive needle emission rates were 11 times higher than the constitutive bark emissions. However, the emission rates from infested Norway spruce tree bark were instead 6 to 20 times higher than the constitutive needle emissions, causing substantial increases in the total tree BVOC emission rate (550 % to 1900 % increase). This study adds evidence that spruce bark beetle induced bark BVOC emissions are higher than previously thought and highlights the need for further research with more samples more frequently throughout the season to fully understand the impact, which is required to quantify spruce bark beetle infestations impacts on the atmospheric chemistry and climate change.

The effect of once-weekly s.c. semaglutide 2.4 mg (sema) on the risk of developing T2D in people with obesity is unknown. Weight management with sema vs. PBO plus diet/exercise was assessed in participants (pts) with overweight/obesity in STEP 1 (68 wks) and STEP 4 (20-wk run-in on sema, 48-wk randomized withdrawal) . The 10-yr T2D risk was calculated post hoc using Cardiometabolic Disease Staging (CMDS) , a validated Bayesian logistic regression of T2D risk factors. Risk scores decreased after 68 wks from 18% to 7% with sema, and 18% to 16% with PBO (61% vs. 13% reduction [p In summary, treatment with sema reduces the 10-yr risk of T2D by ∼60% regardless of initial glycemic status, with sustained treatment required to maintain this benefit. These data suggest sema could help prevent T2D in people with obesity. Disclosure W. Garvey: Other Relationship; Boehringer Ingelheim International GmbH, Eli Lilly and Company, Epitomee, JAZZ Pharmaceuticals, Novo Nordisk, Novo Nordisk, Pfizer Inc., Pfizer Inc. T. Holst-hansen: Employee; Novo Nordisk A/S, Stock/Shareholder; Novo Nordisk A/S. P. N. Laursen: Employee; Novo Nordisk A/S. A. R. Rinnov: Employee; Novo Nordisk. L. J. Wilkinson: Employee; Novo Nordisk. Funding Novo Nordisk A/S

Infected cells communicate through secreted signaling molecules like cytokines, which carry information about pathogens. How differences in cytokine secretion affect inflammatory signaling over space and how responding cells decode information from propagating cytokines are not understood. By computationally and experimentally studying NF-κB dynamics in cocultures of signal-sending cells (macrophages) and signal-receiving cells (fibroblasts), we find that cytokine signals are transmitted by wave-like propagation of NF-κB activity and create well-defined activation zones in responding cells. NF-κB dynamics in responding cells can simultaneously encode information about cytokine dose, duration, and distance to the cytokine source. Spatially resolved transcriptional analysis reveals that responding cells transmit local cytokine information to distance-specific proinflammatory gene expression patterns, creating "gene expression zones." Despite single-cell variability, the size and duration of the signaling zone are tightly controlled by the macrophage secretion profile. Our results highlight how macrophages tune cytokine secretion to control signal transmission distance and how inflammatory signaling interprets these signals in space and time., Science Advances, 8 (35), ISSN:2375-2548

Tree killing by spruce bark beetles (Ips typographus) is one of the main disturbances to Norway spruce (Picea abies) forests in Europe and the risk of outbreaks is amplified by climate change with effects such as increased risk of storm felling, tree drought stress and an additional generation of spruce bark beetles per year[1]. The warm and dry summer of 2018 triggered large outbreaks in Sweden, the increased outbreaks are still ongoing and affected about 8 million m3 forest in 2020[2]. This is the so far highest record of trees killed by the spruce bark beetle in a single year in Sweden[2]. In 1990-2010, the spruce bark beetle killed on average 150 000 m3 forest per year in southern Sweden[3]. Bark beetles normally seek and attack Norway spruces with lowered defense, i.e. trees that are wind-felled or experience prolonged drought stress[4]. However, as the number of bark beetle outbreaks increase, the risk of attacks on healthy trees also increase[5]. This causes a higher threat to forest industry, and lowers the possibilities to mitigate climate change in terms of potential decreases in carbon uptake if the forests die[4,5]. Norway spruce trees normally defend themselves by drenching the beetles in resin[6]. The resin in turn contains different biogenic volatile organic compounds (BVOCs), which can vary if the spruce is attacked by bark beetles or not [4,6]. The most abundant group of terpenoids (isoprene, monoterpenes and sesquiterpenes), is most commonly emitted from conifers, such as Norway spruce[7,8]. The aim of this study was to enable a better understanding of the direct defense mechanisms of spruce trees by quantifying BVOC emissions and its composition from individual trees under attackTo analyze the bark beetles’ impact on Norway spruce trees a method was developed using tree trunk chambers and adsorbent tubes. This enables direct measurements of the production of BVOCs from individual trees. Three different sites in Sweden, with different environmental conditions were used for the study and samples were collected throughout the growing season of 2019. After sampling, the tubes were analyzed in a lab using automated thermal desorption coupled to a gas chromatograph and a mass spectrometer to identify BVOC species and their quantity.The preliminary results show a strong increase in BVOC emissions from a healthy tree that became infested during the data collection. The finalized results expect to enable better understanding of how spruce trees are affected by insect stress from bark beetles, and if bark beetle infestation will potentially result in increased carbon emission in the form of BVOCs.References[1] Jönsson et al. (2012). Agricultural and Forest Meteorology 166: 188–200[2] Skogsstyrelsen, (2020). https://via.tt.se/pressmeddelande/miljontals-granar-dodades-av-granbarkborren-2020?publisherId=415163&releaseId=3288473[3] Marini et al. (2017). Ecography, 40(12), 1426–1435.[4] Raffa (1991). Photochemical induction by herbivores. pp. 245-276[5] Seidl, et al. (2014). Nature Climate Change, 4(9), 806-810. [6] Ghimire, et al. (2016). Atmospheric Environment, 126, 145-152.[7] Niinemets, U. and Monson, R. (2013). ISBN 978-94-007-6606-8[8] Kesselmeier, J. and Staudt, M. (1999). Journal of Atmospheric Chemistry, 33(1), pp.23-88

The ecosystem-atmosphere flux of biogenic volatile organic compounds (BVOCs) has important impacts on tropospheric oxidative capacity and the formation of secondary organic aerosols, influencing air quality and climate. In particular, this is true in managed boreal forests in the Northern Hemisphere, where BVOC emissions often dominate over anthropogenic sources of VOC.Here we present measurements of BVOCs in a managed boreal forest located at the ICOS station Norunda in Sweden, collected using proton transfer reaction mass spectrometry (PTR-MS). This managed forest consists of a mix of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). These long-term PTR-MS measurements were collected at six heights (4m, 8.5m, 13.5m, 19m, 24.5m, and 33.5m) in the forest canopy over several periods during 2014 to 2016. Ozone concentrations were simultaneously measured in conjunction with these PTR-MS measurements. The main BVOCs investigated with the PTR-MS were isoprene, monoterpenes, methanol, acetaldehyde, and acetone. The distribution of BVOC sources and sinks in the forest canopy was explored using several Lagrangian dispersion matrix methods, including localized and continuous near-field theory. The canopy resistance and deposition velocities for ozone and the BVOCs were investigated, and the results for isoprene and monoterpene emissions were found to agree well with several standard BVOC emission algorithms. These results will have importance for constraining BVOC emission estimates from managed boreal forests in the future.

In 2018, an extreme drought affected large parts of Europe and led to the worst fire season in over a century in Sweden. We investigated the impacts of the Ljusdal fire, the largest fire complex that year, on soil CO2 and CH4 fluxes, nutrient concentrations and microclimate in a Scots pine forest. The measurements were conducted during the first growing season after the fire. In three separate analyses, we compared stands that differed in terms of burn severity (unburnt, low and high burn severity), salvage-logging (logged or unlogged) and stand age (young: 12 years old or mature: ~100 years old at the time of the fire). A mature stand affected by a high severity burn (100% tree mortality) had significantly lower soil respiration compared to a stand affected by a low severity burn (nearly 100% tree survival), but there was no difference in soil respiration between the low burn severity and unburn stands. These results indicate that autotrophic respiration plays a key role in determining post-fire soil respiration. After a high severity burn, salvage logging had no significant effects on forest soils compared to a stand where the dead trees had been left standing, although differences between these two stands are likely to become significant in the future. Stand age had a clear impact on most of the soil properties tested. Despite mean soil temperature being 5 °C warmer at a young site compared to a mature site after a high severity burn, soil respiration was lower at the young site. The young site had been clear-cut and undergone soil scarification and replanting 12 years before the fire, which is likely to have contributed to the lower nutrient availability and thinner soil organic layer there compared to the mature site. Short return intervals between disturbances such as harvesting and wildfire that remove part of the soil organic layer can thus have significant and long-term impacts on nutrient cycling and carbon exchange in the boreal forest. The boreal forest is thus vulnerable to becoming a carbon source, especially in regions where climate change is increasing the frequency of high severity wildfire and commercial timber production is expanding.

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 a 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 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 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 with 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., This project has been funded by Swedish Research Council Formas grants 2018-02700, 2019-00836, the strategic research program of the Crafoord Foundation grant 20190763, and the Swedish Strategic Research Area BECC (Biodiversity and Ecosystem Services in a Changing Climate). C.S. also received funding from the Spanish ‘Ramon y Cajal’ programme, Ref. N. RYC2018-025797-I.

Highlights • Vapor pressure deficit strongly influenced VOC emission of tundra shrubs. • Evergreens had a higher leaf-to-air temperature difference than deciduous shrubs. • Leaf traits affected VOC emission of deciduous tundra shrubs. • All shrubs had a higher temperature optimum for photosynthesis than expected., 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.

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.

Approximately 16 % of adult onset asthma is caused by occupational exposure. The need for early detection of irritant caused asthma is key in treating and preventing the progression of the disease. The aim of the work was to investigate if exposure to irritants cause change in gas composition in exhaled breath, the “exhalome”. We studied 15 female hairdressers exposed to a controlled dose of aerosolized bleach powder in a sealed climate chamber. The subjects’ self-reported symptoms, spirometry and gas components were monitored. The exhalome was collected for breath holding times of 2 and 10 seconds from central (400 ml) and peripheral lung (1500 ml), once prior to and twice after exposure. Thus, subjects were their own controls. The composition of the gas was analyzed using a Proton Transfer Reaction – Time of Flight – Mass Spectrometer (PTR-ToF-MS) where volatile organic compounds of mass up to 253 atomic mass units are identified with high time resolution. Preliminary analysis of the data shows a variation of the concentrations of the different gases in exhalome over the course of the day and that levels of isoprene and acetone are higher for longer breath holding time. More analysis is needed to evaluate if the technique is able to detect differences in the exhalome caused by the exposure. Detailed information on the relationships between the exhalome and inflammation processes in the respiratory tract induced by irritants is also required. This may contribute to a deeper understanding of asthma. In the future a PTR-ToF-MS could potentially be used as a real-time non-invasive tool for early detection asthma in exposed workers.

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.

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.

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., Permafrost thaw allows biological activity in previously frozen ground, leading to a potential release of climate-relevant gases. Here the authors show that thawing permafrost emits volatile organic compounds but that their release to the atmosphere is limited by microbial consumption in the overlaying soil.

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 ?molm2 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 -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 -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. 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 ?molm-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 -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 -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. 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 ?molm-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 -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 -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.

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 Piikkio 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.

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 (alpha-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. (C) 2017 The Authors. Published by Elsevier Ltd.

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.

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.

Allele number, or zygosity, is a clear determinant of gene expression in diploid cells. But the relationship between the number of copies of a gene and its expression can be hard to anticipate, especially when the gene in question is embedded in a regulatory circuit that contains feedbacks. Here we study this question making use of the natural genetic variability of human populations, which allows us to compare the expression profiles of a receptor protein in natural killer cells between donors infected with human cytomegalovirus (HCMV) with one or two copies of the allele. Crucially, the distribution of gene expression in many of the donors is bimodal, indicative of the presence of a positive feedback somewhere in the regulatory environment of the gene. Three separate gene-circuit models differing in the location of the positive feedback with respect to the gene can all reproduce well the homozygous data. However, when the resulting fitted models are applied to the hemizygous donors, only one model (the one with the positive feedback located at the level of gene transcription) reproduces the experimentally observed gene-expression profile. In that way, our work shows that zygosity can help us relate structure and function of gene regulatory networks.Author SummaryNearly all mammalian cells, including human cells, have two copies of each chromosome, and thus possess two potentially different copies of each gene (which might be in some cases non-functional or even absent). Naïively one might expect that two identical copies of the gene would lead to the protein being expressed at twice the rate, but many factors can alter this simple calculation. One of these factors is the existence of feedback mechanisms affecting in one way or another the regulatory circuit in which our gene of interest is embedded. Here we study the relationship between the number of gene copies and the expression of a receptor protein that plays a crucial role in the recognition of pathogens by natural killer cells, which are important elements of the innate immune system. Experimental data of virus-infected donors reveals a bimodal expression profile of this receptor, typical of a positive feedback, and a clear difference between donors with one or two copies of the gene. Mathematical modeling allows us to find the likely location of the feedback loop within the gene’s regulatory circuit, by requiring the correct model to reproduce the expression profiles of both types of donors.

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 92–97 % of the total BVOC emissions, whilst sabinene and limonene for European beech ranged between 30.5–40.5 % and 9–15 % 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.

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.Figures

In this study, we present summertime concentrationsand fluxes of biogenic volatile organic compounds(BVOCs) measured at a sub-arctic wetland in northern Swedenusing a disjunct eddy-covariance (DEC) technique basedon a proton transfer reaction mass spectrometer (PTR-MS).The vegetation at the site was dominated by Sphagnum,Carex and Eriophorum spp. The measurements reportedhere cover a period of 50 days (1 August to 19 September2006), approximately one half of the growing season at thesite, and allowed to investigate the effect of day-to-day variationin weather as well as of vegetation senescence on dailyBVOC fluxes, and on their temperature and light responses.The sensitivity drift of the DEC system was assessed bycomparing H3O+-ion cluster formed with water molecules(H3O+(H2O) at m37) with water vapour concentration measurementsmade using an adjacent humidity sensor, and theapplicability of the DEC method was analysed by a comparisonof sensible heat fluxes for high frequency and DEC dataobtained from the sonic anemometer. These analyses showedno significant PTR-MS sensor drift over a period of severalweeks and only a small flux-loss due to high-frequency spectrumomissions. This loss was within the range expectedfrom other studies and the theoretical considerations. In this study, we present summertime concentrations and fluxes of biogenic volatile organic compounds (BVOCs) measured at a sub-arctic wetland in northern Sweden using a disjunct eddy-covariance (DEC) technique based on a proton transfer reaction mass spectrometer (PTR-MS). The vegetation at the site was dominated by Sphagnum, Carex and \textit{Eriophorum} spp. The measurements reported here cover a period of 50 days (1 August to 19 September 2006), approximately one half of the growing season at the site, and allowed to investigate the effect of day-to-day variation in weather as well as of vegetation senescence on daily BVOC fluxes, and on their temperature and light responses. The sensitivity drift of the DEC system was assessed by comparing H3O+-ion cluster formed with water molecules (H3O+(H2O) at m37) with water vapour concentration measurements made using an adjacent humidity sensor, and the applicability of the DEC method was analysed by a comparison of sensible heat fluxes for high frequency and DEC data obtained from the sonic anemometer. These analyses showed no significant PTR-MS sensor drift over a period of several weeks and only a small flux-loss due to high-frequency spectrum omissions. This loss was within the range expected from other studies and the theoretical considerations.Standardised (20 °C and 1000 μmol m−2 s−1 PAR) summer isoprene emission rates found in this study of 329 μg C m−2 (ground area) h−1 were comparable with findings from more southern boreal forests, and fen-like ecosystems. On a diel scale, measured fluxes indicated a stronger temperature dependence than emissions from temperate or (sub)tropical ecosystems. For the first time, to our knowledge, we report ecosystem methanol fluxes from a sub-arctic ecosystem. Maximum daytime emission fluxes were around 270 μg m−2 h−1 (ca. 100 μg C m−2 h−1), and during most nights small negative fluxes directed from the atmosphere to the surface were observed.

High latitude wetlands play an important role for the surface-atmosphere exchange of carbon dioxide (CO2) and methane (CH4), but fluxes of biogenic volatile organic compounds (BVOC) in these ecosystems have to date not been extensively studied. This is despite BVOC representing a measurable proportion of the total gaseous C fluxes at northern locations and in the face of the high temperature sensitivity of these systems that requires a much improved process understanding to interpret and project possible changes in response to climate warming. We measured emission of isoprene and photosynthetic gas exchange over two growing seasons (2005–2006) in a subarctic wetland in northern Sweden with the objective to identify the physiological and environmental controls of these fluxes on the leaf scale. The sedge species Eriophorum angustifolium and Carex rostrata were both emitters of isoprene. Springtime emissions were first detected after an accumulated diurnal mean temperature above 0°C of about 100 degree days. Maximum measured growing season standardized (basal) emission rates (20°C, 1000 μmol m−2 s−1) were 1075 (2005) and 1118 (2006) μg C m−2 (leaf area) h−1 in E. angustifolium, and 489 (2005) and 396 (2006) μg C m−2 h−1 in C. rostrata. Over the growing season, basal isoprene emission varied in response to the temperature history of the last 48 h. Seasonal basal isoprene emission rates decreased with leaf nitrogen (N), which may be explained by the typical growth and resource allocation pattern of clonal sedges as the leaves age. The observations were used to model emissions over the growing season, accounting for effects of temperature history, links to leaf assimilation rate and the light and temperature dependencies of the cold-adapted sedges.

The short-term limit value for PM10 having become effective in January 2005 was exceeded in many regions within the EU in 2005 and 2006. Therefore, strategies, particularly with respect to traffic control, are discussed, which could cause reduced PM10 concentrations leading to a more effective compliance with the short-term PM10 limit value. These strategies are often justified on PM10 differences between a roadside and an adjacent urban background station. As PM10 is a complex mixture of species originating from different sources, the working hypothesis has been posted that the meteorological exchange conditions strongly affect the PM10 concentration. Therefore, the role of the meteorological exchange conditions with respect to different PM10 patterns, like cycles and PM10 episodes, was investigated on the basis of mean daily PM10 values from air pollution monitoring stations in Baden-Wurttemberg (SW Germany) in the period January 2001 to February 2006. To characterise the meteorological exchange conditions in a spatial resolution, different meteorological variables were used. Partly, they are directly measured at the air pollution monitoring stations or, as for the height of the mixing-layer (MLH) and the stagnation index (SI), they were derived from results of the local model (LM) of the German Weather Service. For periods without precipitation, the results show a statistically significant relationship between PM10 and MLH as well as SI. PM10 increased with decreasing MLH and increasing SI. During periods with precipitation, these relationships were very weak and had no statistical significance. The analysis of the influence of precipitation performed on a daily basis revealed a distinct reduction of PM10 on the first day with precipitation after a period without precipitation. On following days without precipitation, PM10 increased again. Characteristic of the PM10 episodes analysed were remarkably reduced meteorological exchange conditions described by MLH, near-surface wind speed and precipitation. As a case study, two extreme PM10 episodes in January/February 2006 were investigated in detail. As expected, the station-specific variability of the mean daily PM10 values correlated well with daily values of MLH and SI reflecting the pattern of the regional meteorological exchange conditions. Altogether, all results of this investigation point out the main significance of the meteorological exchange conditions on the PM10 level, which is particularly dominant during PM10 episodes. (Less)

The effect of forest management (thinning) on in situ carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) trace gas exchange between soil and atmosphere was studied in three consecutive years at three beech forest sites, which differ in aspect [southwest (SW), northeast (NE), northwest (NW)]. At all sites adjacent thinning plots (“T”) and untreated control plots (“C”) were established. Measurements at the SW and NE sites covered the years 4–6 after thinning while at the NW site measurements covered the year before and the first 2 years after thinning. Mean N2O fluxes were

Increased renewable electricity production, coupled with emerging sectors of electricity consumption such as electric vehicles, has led to the desire to shift the times of the day electricity is consumed to better match generation. Different methods have been proposed to shift residential electricity use from the less desirable times to more desirable times, including: feedback technology, pricing incentives, smart appliances, and energy storage. Based on our experience in this area, we present three challenges for residential shifting: getting users to understand the concept of shifting, determining when to shift and communicating that to users, and accounting for the dynamic nature of shifting. We argue that encouraging residential electricity shifting is much more challenging than electricity curtailment, and suggest an increased focus on understanding the everyday practices of users, which are crucial in order to shift electricity use.