Interpreting eddy covariance data from heterogeneous Siberian tundra : land-cover-specific methane fluxes and spatial representativeness

The non-uniform spatial integration, an inherent feature of the eddy covariance (EC) method, creates a challenge for flux data interpretation in a heterogeneous environment, where the contribution of different land cover types varies with flow conditions, potentially resulting in biased estimates in comparison to the areally averaged fluxes and land cover attributes. We modelled flux footprints and characterized the spatial scale of our EC measurements in Tiksi, a tundra site in northern Siberia. We used leaf area index (LAI) and land cover class (LCC) data, derived from very-high-spatial-resolution satellite imagery and field surveys, and quantified the sensor location bias. We found that methane (CH4) fluxes varied strongly with wind direction (-0.09 to 0.59 mu gCH(4)m(-2) s(-1) on average) during summer 2014, reflecting the distribution of different LCCs. Other environmental factors had only a minor effect on short-term flux variations but influenced the seasonal trend. Using footprint weights of grouped LCCs as explanatory variables for the measured CH4 flux, we developed a multiple regression model to estimate LCC group-specific fluxes. This model showed that wet fen and graminoid tundra patches in locations with topography-enhanced wetness acted as strong sources (1.0 mu gCH(4) m(-2) s(-1) during the peak emission period), while mineral soils were significant sinks (-0.13 mu gCH(4) m(-2) s(-1)). To assess the representativeness of measurements, we upscaled the LCC group-specific fluxes to different spatial scales. Despite the landscape heterogeneity and rather poor representativeness of EC data with respect to the areally averaged LAI and coverage of some LCCs, the mean flux was close to the CH4 balance upscaled to an area of 6.3 km(2), with a location bias of 14 %. We recommend that EC site descriptions in a heterogeneous environment should be complemented with footprint-weighted high-resolution data on vegetation and other site characteristics.Peer reviewe

Intratonsillar detection of 27 distinct viruses: A cross-sectional study

Palatine tonsils have been observed to harbor several distinct respiratory and herpesviruses in separate studies. In this study, the presence of these viruses in palatine tonsils was comprehensively studied in both children and adults. A cross-sectional analysis of 181 patients (median age 22 years; range, 2.6-66) operated for a benign tonsillar disease was conducted. Real-time polymerase chain reaction was performed to detect 27 distinct viruses in all: eight human herpesviruses, 16 respiratory viruses, parvo B19, and polyoma BK/JC viruses. Clinical characteristics of the patients and underlying conditions were evaluated. In total, 92% of patients had virus detected in tonsils (Epstein-Barr virus 72%, human herpesvirus 7, and 6B 54% and 16%, respectively, enterovirus 18%, parvovirus B19 7% and the rest <4%). No herpes simplex virus 2, varicella zoster virus, polyoma JC virus, parainfluenza-, metapneumo-, or coronaviruses were found. Enterovirus was more common in children and was frequently observed in the presence of HHV6B. None of the viruses showed a positive association to the tonsillar disease. Respiratory symptoms were not associated with the prevalence of viruses. This study comprehensively reports a cross-sectional view of intratonsillar virus infections in elective tonsillectomy patients in a wide age range cohort. Tonsils are a major virus reservoir for distinct herpes and respiratory viruses without a positive association with tonsillar disease or respiratory symptoms

Ideal cardiovascular health in childhood-Longitudinal associations with cardiac structure and function : The Special Turku Coronary Risk Factor Intervention Project (STRIP) and the Cardiovascular Risk in Young Finns Study (YFS)

Background: Ideal cardiovascular health (CVH), defined by the American Heart Association, is associated with incident cardiovascular disease in adults. However, association of the ideal CVH in childhood with current and future cardiac structure and function has not been studied. Methods and results: The sample comprised 827 children participating in the longitudinal Special Turku Coronary Risk Factor Intervention Project (STRIP) and The Cardiovascular Risk in Young Finns Study (YFS). In STRIP, complete data on the seven ideal CVH metrics and left ventricular (LV) mass measured with echocardiography were available at the age of 15 (n= 321), 17 (n= 309) and 19 (n= 283) years. In YFS, the cohort comprised children aged 12-18 years (n = 506) with complete ideal CVH metrics data from childhood and 25 years later in adulthood, and echocardiography performed in adulthood. In STRIP, ideal CVH score was inversely associated with LV mass during childhood (P = 0.036). In YFS, childhood ideal CVH score was inversely associated with LV mass, LV end-diastolic volume, E/e' ratio, and left atrium end-systolic volume in adulthood (all P <0.01). In addition, improvement of the ideal CVH score between childhood and adulthood was inversely associated with LV mass, LV end-diastolic volume, E/e' ratio, and left atrium end-systolic volume (all P Conclusions: Childhood ideal CVH score has a long-lasting effect on cardiac structure and function, and the association is evident already in childhood. Our findings support targeting the ideal CVHmetrics as part of primordial prevention of cardiovascular diseases. (C) 2016 Elsevier Ireland Ltd. All rights reserved.Peer reviewe

Insect herbivory dampens Subarctic birch forest C sink response to warming

Climate warming is anticipated to make high latitude ecosystems stronger C sinks through increasing plant production. This effect might, however, be dampened by insect herbivores whose damage to plants at their background, non-outbreak densities may more than double under climate warming. Here, using an open-air warming experiment among Subarctic birch forest field layer vegetation, supplemented with birch plantlets, we show that a 2.3 degrees C air and 1.2 degrees C soil temperature increase can advance the growing season by 1-4 days, enhance soil N availability, leaf chlorophyll concentrations and plant growth up to 400%, 160% and 50% respectively, and lead up to 122% greater ecosystem CO2 uptake potential. However, comparable positive effects are also found when insect herbivory is reduced, and the effect of warming on C sink potential is intensified under reduced herbivory. Our results confirm the expected warming-induced increase in high latitude plant growth and CO2 uptake, but also reveal that herbivorous insects may significantly dampen the strengthening of the CO2 sink under climate warming. Warming is expected to increase C sink capacity in high-latitude ecosystems, but plant-herbivore interactions could moderate or offset this effect. Here, Silfver and colleagues test individual and interactive effects of warming and insect herbivory in a field experiment in Subarctic forest, showing that even low intensity insect herbivory strongly reduces C sink potential

Tonsillar cytokine expression between patients with tonsillar hypertrophy and recurrent tonsillitis

Background: Tonsils provide an innovative in vivo model for investigating immune response to infections and allergens. However, data are scarce on the differences in tonsillar virus infections and immune responses between patients with tonsillar hypertrophy or recurrent tonsillitis. We investigated the differences in virus detection and T cell and interferon gene expression in patients undergoing tonsillectomy due to tonsillar hypertrophy or recurrent tonsillitis.Methods: Tonsils of 89 surgical patients with tonsillar hypertrophy (n = 47) or recurrent tonsillitis (n = 42) were analysed. Patients were carefully characterized clinically. Standard questionnaire was used to asses preceding and allergy symptoms. Respiratory viruses were analysed in tonsils and nasopharynx by PCR. Quantitative real-time PCR was used to analyse intratonsillar gene expressions of IFN-alpha, IFN-beta, IFN-gamma, IL-10, IL-13, IL-17, IL-28, IL-29, IL-37, TGF-beta, FOXP3, GATA3, RORC2 and Tbet.Results: Median age of the subjects was 15 years (range 2-60). Patients with tonsillar hypertrophy were younger, smoked less often, had less pollen allergy and had more adenovirus, bocavirus-1, coronavirus and rhinovirus in nasopharynx (all P < 0.05). Only bocavirus-1 was more often detected in hypertrophic tonsils (P < 0.05). In age-adjusted analysis, tonsillar hypertrophy was associated with higher mRNA expressions of IL-37 (P < 0.05).Conclusions: Intratonsillar T cell and interferon gene expressions appeared to be relatively stable for both tonsillar hypertrophy and recurrent tonsillitis. Of the studied cytokines, only newly discovered anti-inflammatory cytokine IL-37, was independently associated with tonsillar hypertrophy showing slightly stronger anti-inflammatory response in these patients

Spatial variation and linkages of soil and vegetation in the Siberian Arctic tundra - coupling field observations with remote sensing data

Arctic tundra ecosystems will play a key role in future climate change due to intensifying permafrost thawing, plant growth and ecosystem carbon exchange, but monitoring these changes may be challenging due to the heterogeneity of Arctic landscapes. We examined spatial variation and linkages of soil and plant attributes in a site of Siberian Arctic tundra in Tiksi, northeast Russia, and evaluated possibilities to capture this variation by remote sensing for the benefit of carbon exchange measurements and landscape extrapolation. We distinguished nine land cover types (LCTs) and to characterize them, sampled 92 study plots for plant and soil attributes in 2014. Moreover, to test if variation in plant and soil attributes can be detected using remote sensing, we produced a normalized difference vegetation index (NDVI) and topographical parameters for each study plot using three very high spatial resolution multispectral satellite images. We found that soils ranged from mineral soils in bare soil and lichen tundra LCTs to soils of high percentage of organic matter (OM) in graminoid tundra, bog, dry fen and wet fen. OM content of the top soil was on average 14 g dm(-3) in bare soil and lichen tundra and 89 g dm(-3) in other LCTs. Total moss biomass varied from 0 to 820 gm(-2), total vascular shoot mass from 7 to 112 gm(-2) and vascular leaf area index (LAI) from 0.04 to 0.95 among LCTs. In late summer, soil temperatures at 15 cm depth were on average 14 degrees C in bare soil and lichen tundra, and varied from 5 to 9 degrees C in other LCTs. On average, depth of the biologically active, unfrozen soil layer doubled from early July to mid-August. When contrasted across study plots, moss biomass was positively associated with soil OM % and OM content and negatively associated with soil temperature, explaining 14-34% of variation. Vascular shoot mass and LAI were also positively associated with soil OM content, and LAI with active layer depth, but only explained 6-15% of variation. NDVI captured variation in vascular LAI better than in moss biomass, but while this difference was significant with late season NDVI, it was minimal with early season NDVI. For this reason, soil attributes associated with moss mass were better captured by early season NDVI. Topographic attributes were related to LAI and many soil attributes, but not to moss biomass and could not increase the amount of spatial variation explained in plant and soil attributes above that achieved by NDVI. The LCT map we produced had low to moderate uncertainty in predictions for plant and soil properties except for moss biomass and bare soil and lichen tundra LCTs. Our results illustrate a typical tundra ecosystem with great fine-scale spatial variation in both plant and soil attributes. Mosses dominate plant biomass and control many soil attributes, including OM % and temperature, but variation in moss biomass is difficult to capture by remote sensing reflectance, topography or a LCT map. Despite the general accuracy of landscape level predictions in our LCT approach, this indicates challenges in the spatial extrapolation of some of those vegetation and soil attributes that are relevant for the regional ecosystem and global climate models.Peer reviewe

A new method for estimating carbon dioxide emissions from drained peatland forest soils for the greenhouse gas inventory of Finland

In peatlands drained for forestry, the soil carbon (C) or carbon dioxide (CO2) balance is affected by both (i) higher heterotrophic CO2-C release from faster decomposing soil organic matter (SOM) and (ii) higher plant litter C input from more vigorously growing forests. This balance and other greenhouse gas (GHG) sinks and sources in managed lands are annually reported by national GHG inventories to the United Nations Climate Change Convention. In this paper, we present a revised, fully dynamic method for reporting the CO2 balance of drained peatland forest soils in Finland. Our method can follow temporal changes in tree biomass growth, tree harvesting and climatic parameters, and it is built on empirical regression models of SOM decomposition and litter input in drained peatland forests. All major components of aboveground and belowground litter input from ground vegetation as well as live trees and trees that died naturally are included, supplemented by newly acquired turnover rates of woody plant fine roots. Annual litter input from harvesting residues is calculated using national statistics of logging and energy use of trees. Leaching, which also exports dissolved C from drained peatlands, is not included. The results are reported as time series from 1990–2021 following the practice in the GHG inventory. Our revised method produces an increasing trend of annual emissions from 0.2 to 2.1 t CO2 ha−1 yr−1 for the period 1990–2021 in Finland (equal to a trend from 1.4 to 7.9 Mt CO2 yr−1 for the entire 4.3 Mha of drained peatland forests), with a statistically significant difference between the years 1990 and 2021. Across the period 1990–2021, annual emissions are on average 1.5 t CO2 ha−1 yr−1 (3.4 Mt CO2 yr−1 for 2.2 Mha area) in warmer southern Finland and −0.14 t CO2 ha−1 yr−1 (−0.3 Mt CO2 yr−1 for 2.1 Mha area) in cooler northern Finland. When combined with data on the CO2 sink created by the growing tree stock, in 2021 the drained peatland forest ecosystems were a source of 1.0 t CO2 ha−1 yr−1 (2.3 Mt CO2 yr−1) in southern Finland and a sink of 1.2 t CO2 ha−1 yr−1 (2.5 Mt CO2 yr−1) in northern Finland. We compare these results to those produced by the semi-dynamic method used earlier in the Finnish GHG inventory and discuss the strengths and vulnerabilities of the new revised method in comparison to more static emission factors.</p