Canopy uptake dominates nighttime carbonyl sulfide fluxes in a boreal forest

Nighttime vegetative uptake of carbonyl sulfide (COS) can exist due to the incomplete closure of stomata and the light independence of the enzyme carbonic anhydrase, which complicates the use of COS as a tracer for gross primary productivity (GPP). In this study we derived nighttime COS fluxes in a boreal forest (the SMEAR II station in Hyytiälä, Finland; 61°51′ N, 24°17′ E; 181 m a.s.l.) from June to November 2015 using two different methods: eddy-covariance (EC) measurements (FCOS-EC) and the radon-tracer method (FCOS-Rn). The total nighttime COS fluxes averaged over the whole measurement period were −6.8 ± 2.2 and −7.9 ± 3.8 pmol m−2 s−1 for FCOS-Rn and FCOS-EC, respectively, which is 33–38 % of the average daytime fluxes and 21 % of the total daily COS uptake. The correlation of 222Rn (of which the source is the soil) with COS (average R2  =  0.58) was lower than with CO2 (0.70), suggesting that the main sink of COS is not located at the ground. These observations are supported by soil chamber measurements that show that soil contributes to only 34–40 % of the total nighttime COS uptake. We found a decrease in COS uptake with decreasing nighttime stomatal conductance and increasing vapor-pressure deficit and air temperature, driven by stomatal closure in response to a warm and dry period in August. We also discuss the effect that canopy layer mixing can have on the radon-tracer method and the sensitivity of (FCOS-EC) to atmospheric turbulence. Our results suggest that the nighttime uptake of COS is mainly driven by the tree foliage and is significant in a boreal forest, such that it needs to be taken into account when using COS as a tracer for GPP

Stock price reaction to profit warnings: The role of time-varying betas

This study investigates the role of time-varying betas, event-induced variance and conditional heteroskedasticity in the estimation of abnormal returns around important news announcements. Our analysis is based on the stock price reaction to profit warnings issued by a sample of firms listed on the Hong Kong Stock Exchange. The standard event study methodology indicates the presence of price reversal patterns following both positive and negative warnings. However, incorporating time-varying betas, event-induced variance and conditional heteroskedasticity in the modelling process results in post-negative-warning price patterns that are consistent with the predictions of the efficient market hypothesis. These adjustments also cause the statistical significance of some post-positive-warning cumulative abnormal returns to disappear and their magnitude to drop to an extent that minor transaction costs would eliminate the profitability of the contrarian strategy

Time trends in socioeconomic differences in incidence rates of cancers of gastro-intestinal tract in Finland

BACKGROUND: The magnitude of socioeconomic differences in health varies between societies, and over time within a given society. We studied the association between social class and incidence of cancers of the gastro-intestinal tract over time in a large cohort in Finland. METHODS: We studied social class variation among 45–69 year-old Finns during 1971–95 in incidence of cancers of the gastro-intestinal tract by means of a computerized record linkage of the Finnish Cancer Registry and the 1970 Population Census, which included social class data. RESULTS: There were 2.3 million individuals in the cohort under follow-up, with 1622 cases of cancer of the esophagus, 8069 stomach (non-cardia), 1116 cardia, 408 small intestine, 6361 colon, 5274 rectum, 1616 liver, 1756 gallbladder, and 5084 pancreas during 1971–1995. Cancers of the esophagus, stomach, cardia, gallbladder and pancreas were most common among persons belonging to a low social class. Cancers of the small intestine in males only, colon in both genders, and rectum in females were most common in the higher social classes. Incidence of stomach cancer decreased and incidence of colon cancer increased over time in both genders in all social classes, and the large differences between social classes remained unchanged over time. Incidence rates of cardia cancer did not change substantially over time. CONCLUSION: There is a large variation in incidence of cancer of the gastrointestinal tract by social class in Finland. Although much of the observed social class differences probably could be explained by known etiological factors such as diet, physical exercise, alcohol consumption, smoking and exogenous hormone use, part of the variation is apparently attributable to largely unknown factors

Deinococcus geothermalis: The Pool of Extreme Radiation Resistance Genes Shrinks

Bacteria of the genus Deinococcus are extremely resistant to ionizing radiation (IR), ultraviolet light (UV) and desiccation. The mesophile Deinococcus radiodurans was the first member of this group whose genome was completely sequenced. Analysis of the genome sequence of D. radiodurans, however, failed to identify unique DNA repair systems. To further delineate the genes underlying the resistance phenotypes, we report the whole-genome sequence of a second Deinococcus species, the thermophile Deinococcus geothermalis, which at its optimal growth temperature is as resistant to IR, UV and desiccation as D. radiodurans, and a comparative analysis of the two Deinococcus genomes. Many D. radiodurans genes previously implicated in resistance, but for which no sensitive phenotype was observed upon disruption, are absent in D. geothermalis. In contrast, most D. radiodurans genes whose mutants displayed a radiation-sensitive phenotype in D. radiodurans are conserved in D. geothermalis. Supporting the existence of a Deinococcus radiation response regulon, a common palindromic DNA motif was identified in a conserved set of genes associated with resistance, and a dedicated transcriptional regulator was predicted. We present the case that these two species evolved essentially the same diverse set of gene families, and that the extreme stress-resistance phenotypes of the Deinococcus lineage emerged progressively by amassing cell-cleaning systems from different sources, but not by acquisition of novel DNA repair systems. Our reconstruction of the genomic evolution of the Deinococcus-Thermus phylum indicates that the corresponding set of enzymes proliferated mainly in the common ancestor of Deinococcus. Results of the comparative analysis weaken the arguments for a role of higher-order chromosome alignment structures in resistance; more clearly define and substantially revise downward the number of uncharacterized genes that might participate in DNA repair and contribute to resistance; and strengthen the case for a role in survival of systems involved in manganese and iron homeostasis

On-line field measurements of monoterpene emissions from Scots pine by proton-transfer-reaction mass spectrometry

We measured the daily patterns of monoterpene emissions from Scots pine (Pinus sylvestris) trees in a boreal coniferous forest in August and September 2004, using an on-line chamber method combined with a proton-transfer-reaction mass spectrometry (PTR-MS) analyzer. The on-line measurements were made in two chambers with a one-year old shoot inside. Simultaneous measurements were performed for carbon dioxide (CO2) exchange, transpiration (H2O), exchange of trace gases (NOx, O3), photosynthetic photon flux density (PPFD), air temperature and relative humidity (RH). The composition of the monoterpene emission did not change during the measurement period, with [delta]3-carene and [alpha]-pinene being the dominant species. The total mono-terpene emission rate (per needle area) was on average 0.5 ng m–2 s–1, varied from non detectable to 2.1 ng m–2 s–1, and showed a typical diurnal pattern with afternoon maximum and nighttime minimum. The emission rates determined with this on-line chamber method were in agreement with results from a simultaneously used established adsorbent sampling technique with offline GC-MS analysis. The monoterpene emissions from the chamber walls were correlated with the chamber temperature and this measurement artifact was dominating at night. Emission rates normalized to 30 °C, using temperature regression coefficient of 0.09 °C–1, ranged from 2.1 µg g(dw)–1 h–1 to 4.4 µg g(dw)–1 h–1. Measurements of emission dynamics of biogenic volatile organic compounds (BVOCs) together with plant physiological activity are urgently needed for the development of mechanistic BVOC emission models in order to assess their regional and global influence

Biophysical controls on CO2 fluxes of three Northern forests based on long-term eddy covariance data

Abstract in Undetermined Six to nine years of net ecosystem carbon exchange (NEE) data from forests in Hyytiala in Finland, Soro in Denmark and Norunda in Sweden were used to evaluate the interannual variation in the carbon balance. For half-monthly periods, average NEE was calculated for the night-time data. For the daytime data parameters were extracted for the relationship to photosynthetic active radiation (PAR). The standard deviation of the parameters was highest for Norunda where it typically was around 25% of the mean, while it was ca. 15% for Hyytiala and Soro. Temperature was the main controller of respiration and photosynthetic capacity in autumn, winter and spring but explained very little of the interannual variation in summer. A strong correlation between respiration and photosynthesis was also revealed. The start, end and length of the growing season were estimated by four different criteria. The start date could explain some of the variation in yearly total NEE and gross primary productivity (GPP) in Hyytiala and Soro, but the average maximum photosynthetic capacity in summer explained more of the variation in annual GPP for all sites than start, end or length of the growing season