Rising air temperatures and changes in precipitation patterns in boreal ecosystems are changing the fire occurrence regimes (intervals, severity, intensity, etc.). The main impacts of fires are reported to be changes in soil physical and chemical characteristics, vegetation stress, degradation of permafrost, and increased depth of the active layer. Changes in these characteristics influence the dynamics of carbon dioxide (CO2) and methane (CH4) fluxes. We have studied the changes in CO2 and CH4 fluxes from the soil in boreal forest areas in central Siberia underlain by continuous permafrost and the possible impacts of the aforementioned environmental factors on the emissions of these greenhouse gases. We have used a fire chronosequence of areas, with the last fire occurring 1, 23, 56, and more than 100 years ago. The soils in our study acted as a source of CO2. Emissions of CO2 were lowest at the most recently burned area and increased with forest age throughout the fire chronosequence. The CO2 flux was influenced by the pH of the top 5cm of the soil, the biomass of the birch (Betula) and alder (Duschekia) trees, and by the biomass of vascular plants in the ground vegetation. Soils were found to be a CH4 sink in all our study areas. The uptake of CH4 was highest in the most recently burned area (forest fire one year ago) and the lowest in the area burned 56 years ago, but the difference between fire chronosequence areas was not significant. According to the linear mixed effect model, none of the tested factors explained the CH4 flux. The results confirm that the impact of a forest fire on CO2 flux is long-lasting in Siberian boreal forests, continuing for more than 50 years, but the impact of forest fire on CH4 flux is minimal.

Factors limiting the production of the greenhouse gases nitrous oxide (N2O) and carbon dioxide (CO2) were investigated in three incubation experiments conducted with soil from top- and subsoil horizons of a peatland which had an acid sulphate mineral subsoil derived from black schists. The effect of moisture was investigated by equilibrating undisturbed soil samples from three horizons (H-2, Cg and Cr) at -10, -60 or -100 cm matric potential and measuring the gas production. In the second experiment, the effects of temperature and various substrates were studied by incubating disturbed soil samples in aerobic conditions at 5 or 20 degrees C, and measuring basal respiration and N2O production before and after adding water, glucose or ammonium into the soil. In the third experiment, the effects of added glucose and/or nitrate on the denitrification in soil samples from four horizons (H1, H2, Cg and Cr were investigated by acetylene inhibition and monitoring of N2O production during a 48-h anaerobic incubation. The production of CO2 in the topmost peat horizon was largest at -10 cm matric potential, and it was larger than those in the mineral subsoil also at -60 and -100 cm potentials. In contrast, drainage seemed to increase N2O production, whereas in the wettest condition the production of N2O in the mineral subsoil was small and the peat horizon was a sink of N2O. Lowering of temperature (from 20 degrees C to 5 degrees C) decreased CO2 production, as expected, but it had almost no role in the production of N2O in aerobic conditions. Glucose addition increased the aerobic production of CO2 in peat, but it had a minor effect in the mineral horizons. Lack of C source (glucose) was limiting anaerobic N2O production in the uppermost peat horizon, while in all other horizons, nitrate proved to be the most limiting factor. It is concluded that peatlands with black schist derived acid sulphate subsoil horizons, such as in this study, have high microbial activity in the peaty topsoil horizons but little microbial activity in the mineral subsoil. These findings are contrary to previous results obtained in sediment-derived acid sulphate soils.

Drainage of peatlands for forestry often leads to carbon dioxide (CO2) net emission from soil due to loss of peat. This emission can be compensated for by the increased tree growth. Hovewer, many drained peatlands have low tree growth due to nutrient limitations. Tree growth at these peatlands can be effectively increased by fertilization, but fertilization has been also found to increase decomposition rates. We studied the long-term effect of fertilization of low-productive forestry-drained peatlands on the complete ecosystem greenhouse gas exchange, including both soil and tree component, and accounting for CO2, methane and nitrous oxide. Five N-rich study sites (flark fens and a rich fen) and one N-poor ombrotrophic site were established. Fertilization had started at the study sites 16-67 years before our measurements. Fertilization considerably increased tree stand CO2 sink ( + 248-1013 g CO2 m(-2) year(-1)). Decomposition increased on average by 45% ( + 431 g CO2 m(-2) year(-1)) and litter production by 38% ( + 360 g CO2 m(-2) year(-1)). Thus, on average 84% of the increased decomposition could be attributed to increased litter production and 16% to increased soil CO 2 net emission due to increased loss of peat. Soil CO2 net emission correlated positively with water table depth and top soil N concentration. Fertilization increased soil CO2 net emission at the drained flark fens on average by 187 g CO2 m(-2) year(-1). At the rich fen, net emission decreased. The N-poor bog exhibited soil CO2 sink both with and without fertilization. Effects on methane and nitrous oxide emissions were small at most sites. The increase in tree stand CO2 sink was higher than the increase in soil CO2 net emission, indicating that fertilization has a climate cooling effect in the decadal time scale. Yet, as the fertilized plots at N-rich sites exhibited soil CO2 source or zero balance, continuation of fertilization-based forestry over several rotations would lead to progressive loss of ecosystem C. At the N-poor bog, fertilization-based forestry may have a climate-cooling effect also in the centennial time scale.

Terrestrial export of dissolved organic carbon (DOC) to watercourses has increased in boreal zone. Effect of decomposing material and soil food webs on the release rate and quality of DOC are poorly known. We quantified carbon (C) release in CO2, and DOC in different molecular weights from the most common organic soils in boreal zone; and explored the effect of soil type and enchytraeid worms on the release rates. Two types of mor and four types of peat were incubated in laboratory with and without enchytraeid worms for 154 days at + 15 A degrees C. Carbon was mostly released as CO2; DOC contributed to 2-9% of C release. The share of DOC was higher in peat than in mor. The release rate of CO2 was three times higher in mor than in highly decomposed peat. Enchytraeids enhanced the release of CO2 by 31-43% and of DOC by 46-77% in mor. High molecular weight fraction dominated the DOC release. Upscaling the laboratory results into catchment level allowed us to conclude that peatlands are the main source of DOC, low molecular weight DOC originates close to watercourse, and that enchytraeids substantially influence DOC leaching to watercourse and ultimately to aquatic CO2 emissions.

Background: Arterial carbon dioxide tension (PaCO2), oxygen tension (PaO2), and mean arterial pressure (MAP) are modifiable factors that affect cerebral blood flow (CBF), cerebral oxygen delivery, and potentially the course of brain injury after cardiac arrest. No evidence regarding optimal treatment targets exists. Methods: The Carbon dioxide, Oxygen, and Mean arterial pressure After Cardiac Arrest and REsuscitation (COMACARE) trial is a pilot multi-center randomized controlled trial (RCT) assessing the feasibility of targeting low-or high-normal PaCO2, PaO2, and MAP in comatose, mechanically ventilated patients after out-of-hospital cardiac arrest (OHCA), as well as its effect on brain injury markers. Using a 23 factorial design, participants are randomized upon admission to an intensive care unit into one of eight groups with various combinations of PaCO2, PaO2, and MAP target levels for 36 h after admission. The primary outcome is neuron-specific enolase (NSE) serum concentration at 48 h after cardiac arrest. The main feasibility outcome is the between-group differences in PaCO2, PaO2, and MAP during the 36 h after ICU admission. Secondary outcomes include serum concentrations of NSE, S100 protein, and cardiac troponin at 24, 48, and 72 h after cardiac arrest; cerebral oxygenation, measured with near-infrared spectroscopy (NIRS); potential differences in epileptic activity, monitored via continuous electroencephalogram (EEG); and neurological outcomes at six months after cardiac arrest. Discussion: The trial began in March 2016 and participant recruitment has begun in all seven study sites as of March 2017. Currently, 115 of the total of 120 patients have been included. When completed, the results of this trial will provide preliminary clinical evidence regarding the feasibility of targeting low-or high-normal PaCO2, PaO2, and MAP values and its effect on developing brain injury, brain oxygenation, and epileptic seizures after cardiac arrest. The results of this trial will be used to evaluate whether a larger RCT on this subject is justified.

The off-site effects of agricultural organic soils include the leaching of N, P, and organic carbon (OC) to watercourses and CO2, CH4, and N2O emissions into the atmosphere. The aim of this study was to quantify how the thickness of organic layers affects these loads. A 19.56-ha experimental field drained by subsurface pipes was established in Ruukki, northwestern Finland. Three plots had a 60–80 cm-thick sedge peat layer and three others had a thickness of 20 cm or less. The drainage pipes lie in mineral soil that, in this field, contains sulfidic material. This study documents the experimental settings and reports on the leaching of substances in the first two years, as well as CO2, CH4 and N2O emissions during eight weeks in one summer. Total N (TN) and OC loads were higher from the thicker peat plots. The mean TN loads during a hydrological year were 15.4 and 9.2 kg ha-1 from the thicker and thinner peat plots, respectively, with organic N representing 36% of TN load. Total P (TP) load averaged 0.27 kg ha-1 yr-1. Dissolved P load represented 63 and 36% of TP in the thicker peat area and only 23 and 13% in the thinner peat area, and was thus increased upon peat thickness. These N and P loads through the subsurface drainage system represented roughly 83% of TN and 64% of TP loads from this field. There were no clear differences in greenhouse gas emissions among the plots during the eight-week monitoring period. Slowly oxidizing sulfide in the subsoil resulted in annual leaching of 147 kg S ha-1, almost ten times that of non-sulfidic soils. Our first results emphasize the effect of the peat thickness on the leaching of substances and warn about considering all organic soils as a single group in environmental assessments.