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Background Indirect calorimetry (IC) measurement is considered the gold standard for the assessment of resting energy expenditure (REE). It is based on the measurement of oxygen and carbon dioxide consumption (VO 2 and VCO 2 , respectively). However, its use is limited by cost and technical issues. It has been proposed that, in critically ill patients, the analysis of VCO 2 obtained from the ventilator alone may be used as an accurate method to assess REE in ventilated patients. This retrospective study aimed to assess the accuracy of VCO 2 measurement alone in the determination of REE. Methods This was a retrospective study conducted at the general intensive care unit of a single university-affiliated tertiary medical center. Patients included were invasively ventilated and their REE was measured by using IC. The respiratory quotients (RQs) were set at 0.8, 0.85, and 0.89. Data were collected from computerized patient files. REE obtained from the ventilator by using VCO 2 (REE-VCO 2 ) alone was compared with REE obtained from IC (REE-IC). Results Measurements were obtained for 80 patients, and 497 REE-IC measurements were compared with REE-VCO 2 obtained at the same time. The mean REE-IC was 2059.5 ± 491.7 kcal/d. The mean REE-RQs corresponding to RQs of 0.80, 0.85, and 0.89 were 1936.8 ± 680.0, 2017.8 ± 708.8, and 2122.1 ± 745.4 kcal/d, respectively. REE-VCO 2 derived from an RQ of 0.85 had the lowest mean difference from REE-IC. Whereas accuracy was higher using an RQ of 0.85, agreement (between 85% and 115%) was highest using an RQ of 0.89. Conclusions The level of agreement of REE obtained from VCO 2 readings with REE obtained from IC was generally low. IC continues to be the recommended method for REE assessment.

Indonesia contributes significantly to deforestation in Southeast Asia. However, much uncertainty remains over the relative contributions of various forest‐exploiting sectors to forest losses in the country. Here, we compare the magnitudes of forest and carbon loss, and forest and carbon stocks remaining within oil palm plantation, logging, fiber plantation (pulp and paper), and coal mining concessions in Indonesia. Forest loss in all industrial concessions, including logging concessions, relate to the conversion of forest to nonforest land cover. We found that the four industries accounted for ∼44.7% (∼6.6 Mha) of forest loss in Kalimantan, Sumatra, Papua, Sulawesi, and Moluccas between 2000 and 2010. Fiber plantation and logging concessions accounted for the largest forest loss (∼1.9 Mha and ∼1.8 Mha, respectively). Although the oil palm industry is often highlighted as a major driver of deforestation, it was ranked third in terms of deforestation (∼1 Mha), and second in terms of carbon dioxide emissions (∼1,300–2,350 Mt CO2). Crucially, ∼34.6% (∼26.8 Mha) of Indonesia's remaining forests is located within industrial concessions, the majority of which is found within logging concessions (∼18.8 Mha). Hence, future development plans within Indonesia's industrial sectors weigh heavily on the fate of Southeast Asia's remaining forests and carbon stocks.

Net photosynthetic assimilation in C₃ plants is mostly viewed as a simple balance between CO₂ fixation by Rubisco-catalyzed carboxylation and CO₂ production by photorespiration (and to a lower extent, by day respiration) that can be easily manipulated during gas exchange experiments using the CO₂ : O₂ ratio of the environment. However, it now becomes clear that it is not so simple, because the photosynthetic response to gaseous conditions involves ‘ancillary’ metabolisms, even in the short-term. That is, carbon and nitrogen utilization by pathways other than the Calvin cycle and the photorespiratory cycle, as well as rapid signaling events, can influence the observed rate of net photosynthesis. The potential impact of such ancillary metabolisms is assessed as well as how it must be taken into account to avoid misinterpretation of photosynthetic CO₂ response curves or low O₂ effects in C₃ leaves.

The rapid increase in microbial activity that occurs when a dry soil is rewetted has been well documented and is of great interest due to implications of changing precipitation patterns on soil C dynamics. Several studies have shown minor net changes in microbial population diversity or abundance following wet-up, but the gross population dynamics of bacteria and fungi resulting from soil wet-up are virtually unknown. Here we applied DNA stable isotope probing with H 2 18 O coupled with quantitative PCR to characterize new growth, survival, and mortality of bacteria and fungi following the rewetting of a seasonally dried California annual grassland soil. Microbial activity, as determined by CO 2 production, increased significantly within three hours of wet-up, yet new growth was not detected until after three hours, suggesting a pulse of nongrowth activity immediately following wet-up, likely due to osmo-regulation and resuscitation from dormancy in response to the rapid change in water potential. Total microbial abundance revealed little change throughout the seven-day post-wet incubation, but there was substantial turnover of both bacterial and fungal populations (49% and 52%, respectively). New growth was linear between 24 and 168 hours for both bacteria and fungi, with average growth rates of 2.3 × 10 8 bacterial 16S rRNA gene copies·[g dry mass] −1 ·h −1 and 4.3 × 10 7 fungal ITS copies·[g dry mass] −1 ·h −1 . While bacteria and fungi differed in their mortality and survival characteristics during the seven-day incubation, mortality that occurred within the first three hours was similar, with 25% and 27% of bacterial and fungal gene copies disappearing from the pre-wet community, respectively. The rapid disappearance of gene copies indicates that cell death, occurring either during the extreme dry down period (preceding five months) or during the rapid change in water potential due to wet-up, generates a significant pool of available C that likely contributes to the large pulse in CO 2 associated with wet-up. A dynamic assemblage of growing and dying organisms controlled the CO 2 pulse, but the balance between death and growth resulted in relatively stable total population abundances, even after a profound and sudden change in environment.

Aims Peat is used as a major ingredient of growing media in horticulture. Peat extracted from bogs can be acidic and low in nutrient availability and is therefore mixed with liming agents, nutrients, surfactants, perlite and so on. This study aims to estimate the rates at which raw peat and the modified peat (‘growing media’) decompose to release carbon dioxide (CO 2 ), to estimate the release of carbon (C) from liming agents and to estimate how peat biogeochemistry is changed. Methods We obtained 28 and 24 samples of raw peat and 24 growing media from four peat extraction companies in Canada. Growing media were treated with horticultural additives. We incubated the samples under laboratory conditions, measuring CO 2 production, tracer using δ 13 C - CO 2 , pH, C, nitrogen (N) content and humification indices (HIs) from infrared technology called Fourier transform-mid infrared (FT-MIR). Results C:N ratio, pH, dissolved organic carbon, bulk density and C content differed significantly ( P  < 0.05) between raw peats and growing media. There was more than a doubling of total CO 2 production from growing media compared to raw peat. HIs show higher values for the growing media, which could result from spectral band shifts in the growing media because of increased cation availability. δ 13 C - CO 2 as a tracer showed an average 22% of the total CO 2 production orginated from added carbonate materials. Conclusion Our results provide the rates (0.15 ± 0.017mgCO 2 -Cg −1 d −1 ) at which horticultural peat decomposes and on the source of emitted CO 2 . This will improve current estimates CO 2 emissions from horticultural peat.

Root-mediated CO2 uptake, O2 release and their effects on O2 and CO2 dynamics in the rhizosphere of Lobelia dortmanna were investigated. Novel planar optode technology, imaging CO2 and O2 distribution around single roots, provided insights into the spatiotemporal patterns of gas exchange between roots, sediment and microbial community. In light, O2 release and CO2 uptake were pronounced, resulting in a distinct oxygenated zone (radius: c. 3 mm) and a CO2-depleted zone (radius: c. 2 mm) around roots. Simultaneously, however, microbial CO2 production was stimulated within a larger zone around the roots (radius: c. 10 mm). This gave rise to a distinct pattern with a CO2 minimum at the root surface and a CO2 maximum c. 2mm away from the root. In darkness, CO2 uptake ceased, and the CO2-depleted zone disappeared within 2 h. By contrast, the oxygenated root zone remained even after 8 h, but diminished markedly over time. A tight coupling between photosynthetic processes and the spatiotemporal dynamics of O2 and CO2 in the rhizosphere of Lobelia was demonstrated, and we suggest that O2-induced stimulation of the microbial community in the sediment increases the supply of inorganic carbon for photosynthesis by building up a CO2 reservoir in the rhizosphere.

Lignin is a main component of plant litter. Its degradation is thought to be critical for litter decomposition rates and the build-up of soil organic matter. We studied the relationships between lignin degradation and the production of dissolved organic carbon (DOC) and of CO 2 during litter decomposition. Needle or leaf litter of five species (Norway spruce, Scots pine, mountain ash, European beech, sycamore maple) and of different decomposition stage (freshly fallen and up to 27 months of field exposure) was incubated in the laboratory for two years. Lignin degradation was followed with the CuO method. Strong lignin degradation occurred during the first 200 incubation days, as revealed by decreasing yields of lignin-derived phenols. Thereafter lignin degradation leveled off. This pattern was similar for fresh and decomposed litter, and it stands in contrast to the common view of limited lignin degradation in fresh litter. Dissolved organic carbon and CO 2 also peaked in the first period of the incubation but were not interrelated. In the later phase of incubation, CO 2 production was positively correlated with DOC amounts, suggesting that bioavailable, soluble compounds became a limiting factor for CO 2 production. Lignin degradation occurred only when CO 2 production was high, and not limited by bioavailable carbon. Thus carbon availability was the most important control on lignin degradation. In turn, lignin degradation could not explain differences in DOC and CO 2 production over the study period. Our results challenge the traditional view regarding the fate and role of lignin during litter decomposition. Lignin degradation is controlled by the availability of easily decomposable carbon sources. Consequently, it occurs particularly in the initial phase of litter decomposition and is hampered at later stages if easily decomposable resources decline.

The doubly labelled water method for the assessment of energy expenditure was first published in 1955, application in humans started in 1982, and it has become the gold standard for human energy requirement under daily living conditions. The method involves enriching the body water of a subject with heavy hydrogen ( 2 H) and heavy oxygen ( 18 O), and then determining the difference in washout kinetics between both isotopes, being a function of carbon dioxide production. In practice, subjects get a measured amount of doubly labelled water ( 2 H 2 18 O) to increase background enrichment of body water for 18 O of 2000 ppm with at least 180 ppm and background enrichment of body water for 2 H of 150 ppm with 120 ppm. Subsequently, the difference between the apparent turnover rates of the hydrogen and oxygen of body water is assessed from blood-, saliva-, or urine samples, collected at the start and end of the observation interval of 1–3 weeks. Samples are analyzed for 18 O and 2 H with isotope ratio mass spectrometry. The doubly labelled water method is the indicated method to measure energy expenditure in any environment, especially with regard to activity energy expenditure, without interference with the behavior of the subjects. Applications include the assessment of energy requirement from total energy expenditure, validation of dietary assessment methods and validation of physical activity assessment methods with doubly labelled water measured energy expenditure as reference, and studies on body mass regulation with energy expenditure as a determinant of energy balance.

In terms of today, one may argue, throughout observations from energy literature papers, that (i) one of the main contributors of the global warming is carbon dioxide emissions, (ii) the fossil fuel energy usage greatly contributes to the carbon dioxide emissions, and (iii) the simulations from energy models attract the attention of policy makers to renewable energy as alternative energy source to mitigate the carbon dioxide emissions. Although there appears to be intensive renewable energy works in the related literature regarding renewables’ efficiency/impact on environmental quality, a researcher might still need to follow further studies to review the significance of renewables in the environment since (i) the existing seminal papers employ time series models and/or panel data models or some other statistical observation to detect the role of renewables in the environment and (ii) existing papers consider mostly aggregated renewable energy source rather than examining the major component(s) of aggregated renewables. This paper attempted to examine clearly the impact of biomass on carbon dioxide emissions in detail through time series and frequency analyses. Hence, the paper follows wavelet coherence analyses. The data covers the US monthly observations ranging from 1984:1 to 2015 for the variables of total energy carbon dioxide emissions, biomass energy consumption, coal consumption, petroleum consumption, and natural gas consumption. The paper thus, throughout wavelet coherence and wavelet partial coherence analyses, observes frequency properties as well as time series properties of relevant variables to reveal the possible significant influence of biomass usage on the emissions in the USA in both the short-term and the long-term cycles. The paper also reveals, finally, that the biomass consumption mitigates CO 2 emissions in the long run cycles after the year 2005 in the USA.

Lakes process a disproportionately large fraction of carbon relative to their size and spatial extent, representing an important component of the global carbon cycle. Alterations of ecosystem function via eutrophication change the balance of greenhouse gas flux in these systems. Without eutrophication, lakes are net sources of CO₂ to the atmosphere, but in eutrophic lakes this function may be amplified or reversed due to cycling of abundant autochthonous carbon. Using a combination of high-frequency and discrete sensor measurements, we calculated continuous CO₂ flux during the ice-free season in 15 eutrophic lakes. We found net CO₂ influx over our sampling period in 5 lakes (– 47 to – 1865 mmol m⁻²) and net efflux in 10 lakes (328 to 11,755 mmol m⁻²). Across sites, predictive models indicated that the highest efflux rates were driven by nitrogen enrichment, and influx was best predicted by chlorophyll a concentration. Regardless of whether CO₂ flux was positive or negative, stable isotope analyses indicated that the dissolved inorganic carbon pool was not derived from heterotrophic degradation of terrestrial organic carbon, but from degradation of autochthonous organic carbon, mineral dissolution, and atmospheric uptake. Optical characterization of dissolved organic matter revealed an autochthonous organic matter pool. CO₂ influx was correlated with autochthony, while efflux was correlated with total nitrogen and watershed wetland cover. Our findings suggest that CO₂ uptake by primary producers during blooms can contribute to continuous CO₂ influx for days to months. Conversely, eutrophic lakes in our study that were net sources of CO₂ to the atmosphere showed among the highest rates reported in the literature. These findings suggest that anthropogenic eutrophication has substantially altered biogeochemical processing of carbon on Earth.