Ozone stress response of leaf BVOC emission and photosynthesis in mountain birch (Betula pubescens spp. czerepanovii) depends on leaf age.

Oxidative stress from ozone (O3) causes plants to alter their emission of biogenic volatile organic compounds (BVOC) and their photosynthetic rate. Stress reactions from O3 on birch trees can result in prohibited plant growth and lead to increased BVOC emission rates as well as changes in their compound blend to emit more monoterpenes (MT) and sesquiterpenes (SQT). BVOCs take part in atmospheric reactions such as enhancing the production of secondary organic aerosols (SOA). As the compound blend and emission rate change with O3 stress, this can influence the atmospheric conditions by affecting the production of SOA. Studying the stress responses of plants provides important information on how these reactions might change, which is vital to making better predictions of the future climate. In this study, measurements were taken to find out how the leaves of mature mountain birch trees (Betula pubescens ssp. czerepanovii) respond to different levels of elevated O3 exposure in situ depending on leaf age. We found that leaves from both early and late summers responded with induced SQT emission after exposure to 120 ppb O3. Early leaves were, however, more sensitive to increased O3 concentrations, with enhanced emission of green leaf volatiles (GLV) and tendencies of both induced leaf senescence as well as poor recovery in the photosynthetic rate between exposures. Late leaves had more stable photosynthetic rates throughout the experiment and responded less to exposure at different O3 levels.

Strong isoprene emission response to temperature in tundra vegetation.

Emissions of biogenic volatile organic compounds (BVOCs) are a crucial component of biosphere-atmosphere interactions. In northern latitudes, climate change is amplified by feedback processes in which BVOCs have a recognized, yet poorly quantified role, mainly due to a lack of measurements and concomitant modeling gaps. Hence, current Earth system models mostly rely on temperature responses measured on vegetation from lower latitudes, rendering their predictions highly uncertain. Here, we show how tundra isoprene emissions respond vigorously to temperature increases, compared to model results. Our unique dataset of direct eddy covariance ecosystem-level isoprene measurements in two contrasting ecosystems exhibited Q10 (the factor by which the emission rate increases with a 10 °C rise in temperature) temperature coefficients of up to 20.8, that is, 3.5 times the Q10 of 5.9 derived from the equivalent model calculations. Crude estimates using the observed temperature responses indicate that tundra vegetation could enhance their isoprene emissions by up to 41% (87%)-that is, 46% (55%) more than estimated by models-with a 2 °C (4 °C) warming. Our results demonstrate that tundra vegetation possesses the potential to substantially boost its isoprene emissions in response to future rising temperatures, at rates that exceed the current Earth system model predictions.

Bidirectional Exchange of Biogenic Volatile Organic Compounds in Subarctic Heath Mesocosms During Autumn Climate Scenarios.

Biogenic volatile organic compound (BVOC) flux dynamics during the subarctic autumn are largely unexplored and have been considered insignificant due to the relatively low biological activity expected during autumn. Here, we exposed subarctic heath ecosystems to predicted future autumn climate scenarios (ambient, warming, and colder, dark conditions), changes in light availability, and flooding, to mimic the more extreme rainfall or snowmelt events expected in the future. We used climate chambers to measure the net ecosystem fluxes and bidirectional exchange of BVOCs from intact heath mesocosms using a dynamic enclosure technique coupled to a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS). We focused on six BVOCs (methanol, acetic acid, acetaldehyde, acetone, isoprene, and monoterpenes) that were among the most dominant and that were previously identified in arctic tundra ecosystems. Warming increased ecosystem respiration and resulted in either net BVOC release or increased uptake compared to the ambient scenario. None of the targeted BVOCs showed net release in the cold and dark scenario. Acetic acid exhibited significantly lower net uptake in the cold and dark scenario than in the ambient scenario, which suggests reduced microbial activity. Flooding was characterized by net uptake of the targeted BVOCs and overruled any temperature effects conferred by the climate scenarios. Monoterpenes were mainly taken up by the mesocosms and their fluxes were not affected by the climate scenarios or flooding. This study shows that although autumn BVOC fluxes on a subarctic heath are generally low, changes in future climate may strongly modify them.

Boreal forest soil carbon fluxes one year after a wildfire: Effects of burn severity and management.

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.

Volatile organic compound emission in tundra shrubs - Dependence on species characteristics and the near-surface environment.

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.

Phenological stage of tundra vegetation controls bidirectional exchange of BVOCs in a climate change experiment on a subarctic heath.

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 interact and influence 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.

Amplification of plant volatile defence against insect herbivory in a warming Arctic tundra.

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.

Biogenic volatile release from permafrost thaw is determined by the soil microbial sink.

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.

Remotely sensed soil moisture to estimate savannah NDVI.

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.

Estimating and Analyzing Savannah Phenology with a Lagged Time Series Model.

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.

Reduced incidence of distant metastases and lower mortality in 1072 patients with breast cancer with a history of hormone replacement therapy.

OBJECTIVE: Substitution of estrogens (hormone replacement therapy [HRT]) is the most common therapy and prophylaxis of postmenopausal complaints. However, in most studies, long-term HRT has been associated with an increased risk for breast cancer, but the influence on a prognosis of breast cancer has been examined rarely. STUDY DESIGN: For further investigation, we analyzed 1072 patients aged 45-70 years at the time of first diagnosis of breast cancer with and without preoperative HRT with regard to the incidence of distant metastases and overall survival. Of these, 279 women were premenopausal (mean, 47.8 +/- 3.2 years); 793 women were postmenopausal (mean, 54.5 +/- 3.5 years); 320 women had received HRT over a minimum of 1 year (mean, 5.5 +/- 4.0 years; group HRT+); and 473 women had not received HRT (group HRT-). The median follow-up time was 73.2 months. RESULTS: Although body mass index, tumor size, and grading of group HRT- were significantly higher than in group HRT+, nodal status, S-phase fraction, hormone-receptor status, and local recurrence showed no significant differences. In regard to the incidence of distant metastases, women without HRT have significantly (P < .001) more metastases to bone (68 vs 20 women), lung (47:13 women), and liver (47:13 women). Overall survival was significantly lower in the HRT- group. CONCLUSION: We were able to show that the use of HRT before the diagnosis of breast cancer results in more favorable primary tumors, with a lower incidence of recurrences and a better overall survival rate. This might be due to normalized bone metabolism by the use of HRT, which may lower the conditions of tumor cell seeding.

Influence of different HRT regimens on mammographic density.

OBJECTIVES: A prospective, randomized, open-label study was conducted to evaluate effects on mammographic density in postmenopausal and late perimenopausal women receiving continuous combined or sequential combined hormone replacement therapy (HRT). METHODS: The subjects were randomized to treatment with low-dose continuous combined HRT containing 1 mg 17beta-estradiol plus 0.5 mg norethisterone acetate (Activelle) or a sequential combined HRT regimen consisting of 0.625 mg conjugated equine estrogens for 28 days plus 5 mg medrogestone for 14 days (Presomen). Mammograms were obtained at baseline and after 9 cycles (each 28 days) of treatment. RESULTS: The majority of women (approximately two-thirds in each treatment group) had no changes in mammographic breast density between baseline and the final study visit. There were no marked differences between treatment groups. Approximately 20% of women in both groups had a slight increase in mammographic density. Only 10-14% of women in both groups had a pronounced increase in mammographic density. The analyses of the degree of change showed no remarkable differences between treatments. CONCLUSION: These results indicate that the increase in mammographic density with a low-dose continuous combined HRT regimen is no greater than that with a sequential combined HRT regimen. The type of progestogen does not have an impact on the extent of mammographic density changes.

Degradation of microcystin in sediments at oxic and anoxic, denitrifying conditions.

The potent toxin microcystin is frequently released during cyanobacterial blooms in eutrophic waters and may impose a risk to human health, when surface water is used for drinking water. For removal of microcystin in surface waters, infiltration through sediment is commonly used. In the present study, mineralization of 14C-labelled microcystin (accumulation of 14CO(2)) and concentration changes (protein phosphatase inhibition assay) demonstrated that indigenous microorganisms in the sediment of a water recharge facility were capable of degrading microcystin. At oxic or microaerophilic (<2% O(2)) conditions, microcystin added to sediment slurries at 70 microg l(-1) was reduced to <20 microg l(-1) in 1-2 weeks, and less than 3 microg l(-1) after 7 weeks. At anoxic conditions (<0.3% O(2)) and with addition of nitrate, the degradation was significantly stimulated, reducing microcystin from 100 to <20 microg l(-1) within 1 day. The simultaneous production of N(2)O in the samples suggests that the microcystin degradation was coupled to dissimilative nitrate reduction (denitrification). Since aquifers and sediments beneath drinking water reservoirs often are anoxic, nitrate respiration may be an important process in removal and detoxification of microcystin.

Carbon isotope composition of various tissues of beech (Fagus sylvatica) regeneration is indicative of recent environmental conditions within the forest understorey.

• Here, the effects were assessed of local climate and canopy thinning on the carbon isotope composition (δ13 C) signatures of different plant groups in the understorey of a beech (Fagus sylvatica) forest in southern Germany. The relationship between δ13 C and environmental parameters, within different time integrals, was also studied. • δ13 C was analysed in different tissues of beech regeneration, and herbaceous and woody understorey vegetation, in thinned and untreated control stands differing in aspect and, hence, local climate, on three dates during the growing season. • Generally, tissues were 13 C-depleted on the north-east, compared with the south-west aspect. Thinning had variable effects on δ13 C, depending on plant group and sampling date. δ13 C in beech leaves and roots in control stands was mostly influenced by mean soil water potential in 4- and 8-wk integrals before sampling, respectively, and in leaves, additionally, by mean radiation in a 4-wk time integral. Shoot water potential and transpiration influenced foliar δ13 C of beech whereas δ13 C in the beech wood was modulated by soil temperature integrated over a 4-wk period before sampling. Above-ground tissues of woody and herbaceous plants were 13 C-enriched in mid-summer; their δ13 C was poorly related to environmental factors. • δ13 C of various tissues of beech regeneration appears to be indicative of recent environmental conditions within the forest understorey and, consequently, this easy-to-determine physiological parameter could be used widely to assess effects of silvicultural treatments.

Bleeding patterns in peri and postmenopausal women taking a continuous combined regimen of estradiol with norethisterone acetate or a conventional sequential regimen of conjugated equine estrogens with medrogestone.

OBJECTIVES: The aim of this study was to compare the incidence of women presenting irregular bleeding episodes following 9 months of treatment with a low dose continuous combined hormone replacement therapy consisting of estradiol (E(2)) and norethisterone acetate (NETA) versus a sequential hormone replacement therapy consisting of conjugated equine estrogens (CEE) and medrogestone (MG). Secondary aims were to establish the relationship between menopausal age and the occurrence of irregular bleeding for both therapies and to assess the efficacy of both therapies in alleviating menopausal symptoms. METHODS: This was a stratified and randomised, open label study conducted with late peri and postmenopausal women at 35 sites in Austria and Germany. A total of 446 women were randomly allocated into two cohorts based on time since last bleeding and then stratified to either a low dose continuous combined therapy consisting of 1 mg E(2) and 0.5 mg NETA for 28 days or a sequential therapy consisting of 0.625 mg CEE for 28 days and 5 mg MG for the final 14 days. Bleeding and menopausal complaints were continuously assessed. Treatments were administered for 9 lunar months. RESULTS: The incidence rate of women presenting irregular bleeding episodes including spotting during cycle 9 was 12.2% with 1mgE(2)/0.5mgNETA and 25.8% with 0.625mgCEE/5mgMG (P = 0.0014). In the group of postmenopausal women (time since last bleeding > or = 12 months) the incidence of irregular bleeding during cycle 9 was 11.0% for 1mgE(2)/0.5mgNETA and 25.0% for 0.625mgCEE/5mgMG). In the group of late perimenopausal women (time since last bleeding 6-11 months) the incidence of irregular bleeding was similar for both treatments at cycle 3, but markedly less in patients with 1mgE(2)/0.5mgNETA at cycle 6 and 9, being significantly different compared to patients with 0.625mgCEE/5mgMG at cycle 6 (P < 0.05). The cumulative rate of amenorrhea (no bleeding or spotting) achieved with 1mgE(2)/0.5mgNETA was 89% for the postmenopausal women and 83.7% for the late perimenopausal women. Both treatments relieved menopausal complaints equally effective. CONCLUSIONS: Regarding the occurrence of irregular bleeding, the low dose continuous combined therapy was superior to the sequential therapy (0.625mgCEE/5mgMG). The low dose continuous combined E(2)/NETA regimen is also suitable for late perimenopausal women since more than 80% of the women had no bleeding or spotting after 9 months of treatment.

Efficacy of a new 7-day transdermal sequential estradiol/levonorgestrel patch in women.

OBJECTIVE: To investigate the efficacy and tolerability of a new 7-day transdermal sequential estradiol/levonorgestrel patch (Fem7 Combi; Merck KGaA; Germany), versus placebo, as hormone replacement therapy in menopausal women. METHODS: A multicentre, randomized, clinical study consisting of a 3-week screening phase, a 12-week double-blind, placebo-controlled treatment phase, and a 12-week open, follow-up phase. Women aged 40-65 years with an intact uterus and menopausal complaints were randomized to either 2 weeks of an estradiol mono patch (50 microg per 24 h) followed by 2 weeks of an estradiol/levonorgestrel combination patch (50 microg/10 microg per 24 h), or a placebo patch, for three 28-day cycles. Changes in the Kupperman Index and the frequency of hot flushes were assessed. RESULTS: The sequential use of a 7-day estradiol patch and a 7-day estradiol/levonorgestrel patch was superior to placebo in reducing menopausal symptoms, and was well tolerated. At the end of the treatment phase, there was a statistically significant reduction in the Kupperman Index score versus placebo (P<0.0001), and a statistically significant difference between groups in the proportion of patients with a reduction in the number of hot flushes (at least 50% versus baseline). During the open follow-up phase, there was a marked reduction in the Kupperman Index score and the number of hot flushes for patients switched from placebo to active study medication. The active medication was effective throughout the 1-week application period. CONCLUSIONS: The new 7-day transdermal sequential estradiol/levonorgestrel patch was well tolerated, providing rapid and effective relief of menopausal symptoms. The addition of low-dose levonorgestrel did not influence the beneficial effects of estradiol.