Carbon Dioxide Exchange Research Articles

Deep and unbiased proteomics, pathway enrichment analysis, and protein-protein interaction of biomarker signatures in migraine.

Currently, there are no biomarkers for migraine. We aimed to identify proteomic biomarker signatures for diagnosing, subclassifying, and predicting treatment response in migraine. This is a cross-sectional and longitudinal study of untargeted serum and cerebrospinal fluid (CSF) proteomics in episodic migraine (EM; n = 26), chronic migraine (CM; n = 26), and healthy controls (HC; n = 26). We developed classification models for biomarker identification and natural clusters through unsupervised classification using agglomerative hierarchical clustering (AHC). Pathway analysis of differentially expressed proteins was performed. Of 405 CSF proteins, the top five proteins that discriminated between migraine patients and HC were angiotensinogen, cell adhesion molecule 3, immunoglobulin heavy variable (IGHV) V-III region JON, insulin-like growth factor binding protein 6 (IGFBP-6), and IGFBP-7. The top-performing classifier demonstrated 100% sensitivity and 75% specificity in differentiating the two groups. Of 229 serum proteins, the top five proteins in classifying patients with migraine were immunoglobulin heavy variable 3-74 (IGHV 3-74), proteoglycan 4, immunoglobulin kappa variable 3D-15, zinc finger protein (ZFP)-814, and mediator of RNA polymerase II transcription subunit 12. The best-performing classifier exhibited 94% sensitivity and 92% specificity. AHC separated EM, CM, and HC into distinct clusters with 90% success. Migraine patients exhibited increased ZFP-814 and calcium voltage-gated channel subunit alpha 1F (CACNA1F) levels, while IGHV 3-74 levels decreased in both cross-sectional and longitudinal serum analyses. ZFP-814 remained upregulated during the CM-to-EM reversion but was suppressed when CM persisted. CACNA1F was pronounced in CM persistence. Pathway analysis revealed immune, coagulation, glucose metabolism, erythrocyte oxygen and carbon dioxide exchange, and insulin-like growth factor regulation pathways. Our data-driven study provides evidence for identifying novel proteomic biomarker signatures to diagnose, subclassify, and predict treatment responses for migraine. The dysregulated biomolecules affect multiple pathways, leading to cortical spreading depression, trigeminal nociceptor sensitization, oxidative stress, blood-brain barrier disruption, immune response, and coagulation cascades. NCT03231241, ClincialTrials.gov.

РАСЧЕТ ЗАПАСА УГЛЕРОДА В БИОМАССЕ ДРЕВОСТОЕВ ЗАЩИТНЫХ ЛЕСНЫХ НАСАЖДЕНИЙ ПО ГРУППАМ ВОЗРАСТА ПРЕОБЛАДАЮЩИХ ПОРОД

Increasing the productivity and efficiency of protective forest plantations, taking into account their impact on solving the carbon neutrality of regions, is an urgent problem of modern agroforestry science. Based on the importance of solving the problem of reducing the volume of carbon dioxide, the purpose of the research is to assess the net ecosystem exchange of carbon dioxide in protective forest plantations (HLN) in the forest-steppe zone of the Volga upland. The paper uses methods for calculating the regional estimate of the carbon budget. The formation of a functionally targeted "carbon fiber" system of WLD facilities is carried out using a systematic priority-target method based on the basic forestry classification of protective forest plantations by age groups and breed composition. The distribution of protective forest stands by age group and breed composition made it possible to calculate the carbon reserve in the biomass of stands of protective forest stands. The calculation of the biomass of stands of coniferous and hardwoods made it possible to identify and establish for each age group the potential ability to effectively deposit carbon in the soil. Based on the carbon reserves established for each age structure and rock composition in the biomass pool of coniferous and hard-leaved stands by soil and climatic subdistricts, it becomes possible to regulate the carbon balance at the level of a separate region, a separate forestry enterprise. Taking into account the agroecological conditions of the sites – objects of protective afforestation, their main purpose, it is possible to use ZLN to include them in the long-term target "carbon" system of the region, with the development of measures for the regime of their use and increase their protective functions.. The accumulation of biomass of stands of different age groups depends on the soil and climatic disparity of slopes of different exposures and different agro-climatic subdistricts. Losses of carbon reserves in pools of protective forest plantations due to external influences as a result of economic activity or lack of care for these plantations reduce their protective effectiveness and productivity. Carbon reserves in the biomass of a stand of coniferous and hardwoods depend on their age structure.

The impact of drying on the structure and photosynthesis of boreal peatland vegetation

Boreal peatlands harbour large stores of carbon as peat below their surfaces. Climate change is expected to cause drying in northern peatlands, which will in turn impact the carbon balance of these ecosystems that is maintained by high water tables and the hydrologically sensitive plants growing there. This study aims to quantify how vegetation will be structured (I) and photosynthesize (II, III) in a future climate as emulated by long-term water level drawdown (WLD). To do this, changes in the vegetation and its photosynthesis after WLD are linked, and the response of Sphagnum mosses to periodic drought is investigated. Field measurements were done at a long-term WLD field experiment that contained a rich (mesotrophic) fen, a poor (oligotrophic) fen and a bog (ombrotrophic) site. Measurements included vegetation surveys from existing permanent sample plots and leaf-level carbon dioxide exchange measurements. For an experiment in controlled conditions peatland surface cores from this field experiment were transported to a greenhouse where the photosynthesis of lawn Sphagna during and after an experimental periodic drought was measured. The field study revealed that the response of peatland vegetation to WLD depend on peatland type. The species composition in the rich fen was the most impacted by WLD, while the bog vegetation demonstrated stability. Similarly, large increases in photosynthesis occurred following WLD on the vascular plant-covered rich fen, while changes were negligible on the Sphagnum-carpeted bog. The vegetation on the two fens shifted from an open sedge-, or sedge and Sphagnum-dominated ecosystem, to a tree-dominated ecosystem. Canopy development following WLD further accelerated vegetation changes by shading and sheltering the understorey vegetation. Vascular plants were the most likely to increase productivity from WLD as they are best suited to utilize the nutrients made available by peat mineralization, while Sphagnum moss photosynthesis was impacted little. The greenhouse study revealed that lawn Sphagnum mosses exposed to long-term WLD were more vulnerable to drought compared to those from wet sites. Large capitula typical to fen Sphagnum species appeared to be beneficial for surviving periodic drought. This work demonstrated that climate change as emulated by long-term WLD will have a large impact on the vegetation composition of northern peatlands and increase photosynthetic function of these ecosystems, fens in particular. To better predict climate feedbacks from these changes, carbon dynamics including peatland vegetation dynamics should be updated in global process models. Future research to better understand the tipping point of different peatland types after WLD in different climatic regions will help us to predict changes in these diverse and globally important systems.

Root and rhizosphere contribution to the net soil COS exchange

Background and aimsPartitioning the measured net ecosystem carbon dioxide (CO2) exchange into gross primary productivity (GPP) and ecosystem respiration remains a challenge, which scientists try to tackle by using the properties of the trace gas carbonyl sulfide (COS). Its similar pathway into and within the leaf makes it a potential photosynthesis proxy. The application of COS as an effective proxy depends, among other things, on a robust inventory of potential COS sinks and sources within ecosystems. While the soil received some attention during the last couple of years, the role of plant roots is mostly unknown. In our study, we investigated the effects of live roots on the soil COS exchange.MethodsAn experimental setup was devised to measure the soil and the belowground plant parts of young beech trees observed over the course of 9 months.ResultsDuring the growing season, COS emissions were significantly lower when roots were present compared to chambers only containing soil, while prior to the growing season, with photosynthetically inactive trees, the presence of roots increased COS emissions. The difference in the COS flux between root-influenced and uninfluenced soil was fairly constant within each month, with diurnal variations in the COS flux driven primarily by soil temperature changes rather than the presence or absence of roots.ConclusionWhile the mechanisms by which roots influence the COS exchange are largely unknown, their contribution to the overall ground surface COS exchange should not be neglected when quantifying the soil COS exchange.

Long‐term changes in the daytime growing season carbon dioxide exchange following increased temperature and snow cover in arctic tundra

AbstractIncreasing temperatures and winter precipitation can influence the carbon (C) exchange rates in arctic ecosystems. Feedbacks can be both positive and negative, but the net effects are unclear and expected to vary strongly across the Arctic. There is a lack of understanding of the combined effects of increased summer warming and winter precipitation on the C balance in these ecosystems. Here we assess the short‐term (1–3 years) and long‐term (5–8 years) effects of increased snow depth (snow fences) (on average + 70 cm) and warming (open top chambers; 1–3°C increase) and the combination in a factorial design on all key components of the daytime carbon dioxide (CO2) fluxes in a wide‐spread heath tundra ecosystem in West Greenland. The warming treatment increased ecosystem respiration (ER) on a short‐ and long‐term basis, while gross ecosystem photosynthesis (GEP) was only increased in the long term. Despite the difference in the timing of responses of ER and GEP to the warming treatment, the net ecosystem exchange (NEE) of CO2 was unaffected in the short term and in the long term. Although the structural equation model (SEM) indicates a direct relationship between seasonal accumulated snow depth and ER and GEP, there were no significant effects of the snow addition treatment on ER or GEP measured over the summer period. The combination of warming and snow addition turned the plots into net daytime CO2 sources during the growing season. Interestingly, despite no significant changes in air temperature during the snow‐free time during the experiment, control plots as well as warming plots revealed significantly higher ER and GEP in the long term compared to the short term. This was in line with the satellite‐derived time‐integrated normalized difference vegetation index of the study area, suggesting that more factors than air temperature are drivers for changes in arctic tundra ecosystems.

Spatial variation characteristics and influencing factors of CO2 partial pressure in the middle reaches of the Yellow River during summer

AbstractThe partial pressure of CO2 in rivers regulates the intensity and direction of carbon dioxide (CO2) exchange at the water–air interface. Environmental, nutrient factors, and their stoichiometric ratios within the watershed may affect the level of carbon dioxide partial pressure in rivers. However, the relationship between pCO2 responses to the environment, nutrient factors, and their stoichiometric ratios at a large watershed scale was not well understood. In this study, water samples from 20 locations in the mainstream and 16 tributaries of the middle reaches of the Yellow River were collected to study the spatial characteristics of pCO2 and its influencing factors. pCO2 vales showed spatial heterogeneity ranging from 45.57 to 3631.48 μatm, and an average of 1341.87 μatm. Relative to the atmospheric equilibrium value (415 μatm), 90% of the samples were supersaturated. During the study period, higher pCO2 appeared in the Wanjiazhai Reservoir at the northernmost part of the mainstream in the middle reaches, and in the tributaries of the Fen, Wei, and Beiluo Rivers. Overall, the transition from carbon sink to carbon source was experienced in the middle reaches of the Yellow River from north to south. River pCO2 exhibited a significant correlation with phosphorus concentrations and their associated stoichiometric ratio, suggesting that microbial metabolism drove CO2 saturation in rivers. In addition, different land use proportions contributed significantly to changes in river pCO2.

Effects of complete slip conditions on the peristaltic pumping of a Casson nanofluid with suction and injection in a vertical channel

This study investigates the effects of complete slip conditions on the peristaltic pumping of a Casson nanofluid with suction and injection in a vertical due to the crucial role that nano liquids play in a variety of technological and medical fields, particularly in peristalsis, a mechanism that transports liquids. The Casson fluid belongs to a class of non-Newtonian fluids that, through a particular stress threshold magnitude, exhibit elastic solid behavior before changing to liquid behavior. These fluids have several uses in engineering, food preparation, drilling and other fields. After establishing the governing conservation equations, the resulting flow model is effectively simulated using the realistic assumptions of a long wavelength and a low Reynolds number. The temperature distributions, velocity, pressure rate per wavelength and nanoparticle concentration of the resulting flow problem have been solved analytically. The effects of all physical factors on temperature, velocity, concentration fields, pressure rate, frictional force and pressure gradient are graphically examined using Wolfram MATHEMATICA software. There are a variety of biofluids that cannot be classified as liquids. For example, blood contains WBC, RBC and plasma. It is essential to model biofluids (blood) as nanofluids given the physical properties of these biofluids. According to reports, one of the finest yield stress models is the Casson model, and blood exhibits a similar behavior. We took these facts into consideration when thinking about Casson nanofluid flow in a vertical layer under peristalsis. Additionally, the suction and injection mechanisms can be used to represent the exchange of carbon dioxide in bold. In order to understand how blood flows through small blood vessels, this model must be examined. The obtained results show that the Newtonian case and those found in the literature have a very good agreement. Since the liquid moves faster and more effectively when the value is increased, it becomes clear that this increases the strength of the velocity. In other words, nanoperistaltic pumps can maintain a pressure differential that increases or decreases at all operating flow rates with an increasing thermophoresis effect. Furthermore, it is obvious that the pressure reduction in a Casson fluid is greater than in a Newtonian fluid.

Water Stress Dominates 21st‐Century Tropical Land Carbon Uptake

AbstractWater stress regulates land‐atmosphere carbon dioxide (CO2) exchanges in the tropics; however, its role remains poorly characterized due to the confounding roles of radiation, temperature and canopy dynamics. In particular, uncertainty stems from the relative roles of plant‐available water (supply) and atmospheric water vapor deficit (demand) as mechanistic drivers of photosynthetic carbon (C) uptake variability. Using satellite measurements of gravity, CO2 and fluorescence to constrain a mechanistic carbon‐water cycle model from 2001 to 2018, we found that the interannual variability (IAV) of water stress on photosynthetic C uptake was 52% greater than the combined effects of other factors. Surprisingly, the dominance of water stress on C uptake IAV was greater in the wet tropics (94%) than in the dry tropics (26%). Plant‐available water supply and atmospheric demand both contributed to the IAV of water stress on photosynthetic C uptake across the tropics, but the IAV of demand effects was 21% greater than the IAV of supply effects (33% greater in the wet tropics and 6% greater in the dry tropics). We found that the IAV of water stress on C uptake was 24% greater than the IAV of the combination of other factors in the net land‐atmosphere C sink in the whole tropics, 26% greater in the wet tropics, and 7% greater in the dry tropics. Given the recent trends in tropical precipitation and atmospheric humidity, our findings indicate that water stress——from both supply and demand——will likely dominate the climate response of land C sink across tropical ecosystems in the coming decades.

Long-term summer warming reduces post-fire carbon dioxide losses in an arctic heath tundra

The frequency and extent of wildfires in the Arctic has been increasing due to climate change. However, there is a lack of understanding about long-term impacts of climate warming on post-fire carbon dioxide (CO2) exchange in arctic tundra ecosystems. To investigate this, we conducted an experimental low-intensity fire in combination with summer warming (using open top chambers) in a dry heath tundra ecosystem in West Greenland. We report here on the impact four and five years after the fire. We also examined immediate effects of soil heating to three temperature levels (35, 55 and 80 °C), as a simulation of heat transfer during a typical tundra fire. Fire increased soil organic phosphorus concentrations up to at least four years after the burning. The burned areas remained a net CO2 source five years after the fire, mainly due to the lower aboveground vegetation biomass and reduced gross ecosystem production (GEP). However, with four to five years of summer warming, the GEP, ecosystem respiration and soil respiration significantly increased, and burned areas turned into a net CO2 sink. Ex-situ soil heating to the temperature of 55 °C, reaching the heat load comparable with in-situ burning, had minor effects on soil GHG fluxes. This suggests that soil GHG activities are not immediately affected by heat transfer and associated soil temperature increases during a typical low-intensity wildfire in arctic dry tundra. Overall, our results reveal that in a future warmer climate, vegetation is likely to recover more quickly from fires, resulting in a reduction in post-fire CO2 losses.

Livestock grazing and biodiversity: Effects on CO2 exchange in semi-arid Karoo ecosystems, South Africa

Livestock use in semi-arid South African ecosystems has not been extensively studied in relation to the Net Ecosystem Exchange (NEE) of carbon dioxide (CO2). We present four years of measurements from twinned eddy-covariance towers in Nama-Karoo, South Africa, to investigate the carbon fluxes and the impact of grazing intensity on NEE. The design contrasted NEE at a long-term site grazed at recommended levels (LG) with a long-term heavily grazed (EG) site that had been rested for 10 years, and was monitored for two years after which intensive grazing was reintroduced for this experiment. This allowed for the quantification of long-term NEE trends on “recovering” vegetations (years I, II) and short-term responses to an intensified land use (years III, IV). The results showed that the net release of CO2 was slightly higher at LG than on “recovering” vegetation at the EG site, where near-neutral exchange was observed during years I and II. However, after grazing was reintroduced to the EG site, differences between sites was reduced but not eliminated. These findings suggest that there is a somewhat higher carbon sequestration potential at the resting EG site than at the LG site, apparently associated with the dominance of unpalatable drought-tolerant grass species and local elimination of many palatable shrubs. Reduction of this sink potential by reintroduction of high-intensity grazing indicates the sensitivity of C-sequestration in this “recovering” system to heavy grazing, but underlines continued resilience of NEE under far heavier grazing than in the LG system. These data suggest notable trade-offs in these ecosystems between carbon storage, biodiversity, and livestock production with rainfall variability being a critical inter-annual driver. Plain language summaryThis study suggests that long-term resting of previously over-utilized southern African semi-arid vegetation supports enhanced carbon sequestration potential, even if over-utilization has transformed vegetation composition (i.e. has caused degradation through reduced plant species richness). However, this enhanced carbon sequestration potential can be quickly negated by the reintroduction of grazing, even after 10 years of resting. Achievement of carbon sequestration is dependent on average to above-average precipitation and its distribution throughout the year, with sink activity evident mainly after seasonal rains during the warm season.

Leaf-cutter ants - mycorrhizal fungi: observations and research questions from an unexpected mutualism.

Leaf-cutter ants (LCAs) are widely distributed and alter the physical and biotic architecture above and below ground. In neotropical rainforests, they create aboveground and belowground disturbance gaps that facilitate oxygen and carbon dioxide exchange. Within the hyperdiverse neotropical rainforests, arbuscular mycorrhizal (AM) fungi occupy nearly all of the forest floor. Nearly every cubic centimeter of soil contains a network of hyphae of Glomeromycotina, fungi that form arbuscular mycorrhizae. Our broad question is as follows: how can alternative mycorrhizae, which are-especially ectomycorrhizae-essential for the survival of some plant species, become established? Specifically, is there an ant-mycorrhizal fungus interaction that facilitates their establishment in these hyperdiverse ecosystems? In one lowland Costa Rican rainforest, nests of the LCA Atta cephalotes cover approximately 1.2% of the land surface that is broadly scattered throughout the forest. On sequencing the DNA from soil organisms, we found the inocula of many AM fungi in their nests, but the nests also contained the inocula of ectomycorrhizal, orchid mycorrhizal, and ericoid mycorrhizal fungi, including Scleroderma sinnamariense, a fungus critical to Gnetum leyboldii, an obligate ectomycorrhizal plant. When the nests were abandoned, new root growth into the nest offered opportunities for new mycorrhizal associations to develop. Thus, the patches created by LCAs appear to be crucial sites for the establishment and survival of shifting mycorrhizal plant-fungal associations, in turn facilitating the high diversity of these communities. A better understanding of the interactions of organisms, including cross-kingdom and ant-mycorrhizal fungal interactions, would improve our understanding of how these ecosystems might tolerate environmental change.

Carbon dioxide exchange in an idealized valley

On a global scale the budget of carbon dioxide (CO2) bears a substantial uncertainty, which is commonly understood to be mainly due to land-surface exchange processes. In this paper it is examined to what extent mountainous model topography can amplify these land-surface exchange processes. The underlying hypothesis is that, on the meso-scale, topography adds additional atmospheric mechanisms that drive the exchange of CO2 at the surface.This model sensitivity study represents an advancement in model development through the implementation of a pioneering combination of the Weather Research and Forecasting (WRF) model, coupled with the Community Land Model (CLM4) to account for photosynthesis, and the semi-empirical TPGPP-LAI model to address ecosystem respiration. An idealized sine-shaped valley is investigated to examine the effect of complex topography on the CO2 budget compared to flat terrain. The systematic variation of meteorological initial conditions and plant functional types create an ensemble that unveils the fundamental factors which dominate the differences of CO2 fluxes between simulations with topography compared to a flat reference surface.During daytime, when there is photosynthesis, the vegetation temperature of the hypothetical sub-grid scale valley is on average 0.7 K colder and its vapor pressure deficit is 0.8 hPa lower which results in stronger net ecosystem exchange. During nighttime the valley is 0.6 K warmer than the plain, which increases ecosystem respiration compared to the plain. Over 24 h the valley is 0.1 K colder, but it acts as a sink of CO2 as the two opposing processes, during daytime and at night, result in 0.2 gC m−2 d−1 stronger net ecosystem exchange in the valley. During daytime differences are caused implicitly by meso-scale circulations through a secondary effect, as slope-winds shape the vertical temperature and humidity profiles, whereas at night the larger surface area of the valley is the prime cause for the differences. In contrast, the effect of differences in ambient CO2 on the ecosystem exchange is negligible.

MixNet-LD: An Automated Classification System for Multiple Lung Diseases Using Modified MixNet Model.

The lungs are critical components of the respiratory system because they allow for the exchange of oxygen and carbon dioxide within our bodies. However, a variety of conditions can affect the lungs, resulting in serious health consequences. Lung disease treatment aims to control its severity, which is usually irrevocable. The fundamental objective of this endeavor is to build a consistent and automated approach for establishing the intensity of lung illness. This paper describes MixNet-LD, a unique automated approach aimed at identifying and categorizing the severity of lung illnesses using an upgraded pre-trained MixNet model. One of the first steps in developing the MixNet-LD system was to build a pre-processing strategy that uses Grad-Cam to decrease noise, highlight irregularities, and eventually improve the classification performance of lung illnesses. Data augmentation strategies were used to rectify the dataset's unbalanced distribution of classes and prevent overfitting. Furthermore, dense blocks were used to improve classification outcomes across the four severity categories of lung disorders. In practice, the MixNet-LD model achieves cutting-edge performance while maintaining model size and manageable complexity. The proposed approach was tested using a variety of datasets gathered from credible internet sources as well as a novel private dataset known as Pak-Lungs. A pre-trained model was used on the dataset to obtain important characteristics from lung disease images. The pictures were then categorized into categories such as normal, COVID-19, pneumonia, tuberculosis, and lung cancer using a linear layer of the SVM classifier with a linear activation function. The MixNet-LD system underwent testing in four distinct tests and achieved a remarkable accuracy of 98.5% on the difficult lung disease dataset. The acquired findings and comparisons demonstrate the MixNet-LD system's improved performance and learning capabilities. These findings show that the proposed approach may effectively increase the accuracy of classification models in medicinal image investigations. This research helps to develop new strategies for effective medical image processing in clinical settings.

El Niño-Southern Oscillation forcing on carbon and water cycling in a Bornean tropical rainforest

Carbon dioxide and water vapor exchanges between tropical forest canopies and the atmosphere through photosynthesis, respiration, and evapotranspiration (ET) influence carbon and water cycling at the regional and global scales. Their inter- and intra-annual variations are sensitive to seasonal rhythms and longer-timescale tropical climatic events. In the present study, we assessed the El Niño-Southern Oscillation (ENSO) influence on ET and on the net ecosystem exchange (NEE), using eddy-covariance flux observations in a Bornean rainforest over a 10-y period (2010-2019) that included several El Niño and La Niña events. From flux model inversions, we inferred ecophysiological properties, notably the canopy stomatal conductance and "big-leaf" maximum carboxylation rate (Vcmax25_BL). Mean ET values were similar between ENSO phases (El Niño, La Niña, and neutral conditions). Conversely, the mean net ecosystem productivity was highest during La Niña events and lowest during El Niño events. Combining Shapley additive explanation calculations for nine controlling factors with a machine-learning algorithm, we determined that the primary factors for ET and NEE in the La Niña and neutral phases were incoming shortwave solar radiation and Vcmax25_BL, respectively, but that canopy stomatal conductance was the most significant factor for both ET and NEE in the El Niño phase. A combined stomatal-photosynthesis model approach further indicated that Vcmax25_BL differences between ENSO phases were the most significant controlling factor for canopy photosynthesis, emphasizing the strong need to account for ENSO-induced ecophysiological factor variations in model projections of the long-term carbon balance in Southeast Asian tropical rainforests.

A dataset of water, heat, and carbon fluxes of an oasis agroecosystem in the middle areas of the Hexi Corridor (2012–2015)

The exchange of water, heat, and carbon dioxide between the terrestrial ecosystems and the atmosphere is a fundamental process that underlies mass and energy transfer at the Earth’s surface. The eddy covariance technique has become one of the preferred and state-of-the-art approaches for measuring and calculating the exchange of water, heat, and carbon between the land surface and the atmosphere. This dataset covers the fluxes of water, heat, and carbon dioxide in an oasis agroecosystem, as well as the auxiliary micrometeorological variables in the middle areas of the Hexi Corridor during 2012–2015. The experimental observation campaign was carried out by the Linze Inland River Basin Research Station, a member station of the China Flux Observation and Research Network (ChinaFLUX). The dataset serves as a fundamental source of data, enabling in-depth comprehension water transfer, energy exchange, carbon cycle processes in the oasis agroecosystem in arid regions, and even their environmental and vegetation controlling mechanisms. It offers valuable insights into better understanding hydrological processes, ecosystem-hydrology reaction and discovering the coupling between carbon, water and heat in the context of climate change. Furthermore, the dataset holds significant scientific value in addressing chronic practical challenges related to fragile environment and shortage of water resource, such as water and land resources management, the preservation of oasis stability and sustainable development, the conservation of oasis ecosystems, etc.

Air‐Sea CO2 Fluxes Localized by Topography in a Southern Ocean Channel

AbstractAir‐sea exchange of carbon dioxide (CO2) in the Southern Ocean plays an important role in the global carbon budget. Previous studies have suggested that flow around topographic features of the Southern Ocean enhances the upward supply of carbon from the deep to the surface, influencing air‐sea CO2 exchange. Here, we investigate the role of seafloor topography on the transport of carbon and associated air‐sea CO2 flux in an idealized channel model. We find elevated CO2 outgassing upstream of a seafloor ridge, driven by anomalous advection of dissolved inorganic carbon. Argo‐like Lagrangian particles in our channel model sample heterogeneously in the vicinity of the seafloor ridge, which could impact float‐based estimates of CO2 flux.

Widespread use of proton-pumping rhodopsin in Antarctic phytoplankton

Photosynthetic carbon (C) fixation by phytoplankton in the Southern Ocean (SO) plays a critical role in regulating air-sea exchange of carbon dioxide and thus global climate. In the SO, photosynthesis (PS) is often constrained by low iron, low temperatures, and low but highly variable light intensities. Recently, proton-pumping rhodopsins (PPRs) were identified in marine phytoplankton, providing an alternate iron-free, light-driven source of cellular energy. These proteins pump protons across cellular membranes through light absorption by the chromophore retinal, and the resulting pH energy gradient can then be used for active membrane transport or for synthesis of adenosine triphosphate. Here, we show that PPR is pervasive in Antarctic phytoplankton, especially in iron-limited regions. In a model SO diatom, we found that it was localized to the vacuolar membrane, making the vacuole a putative alternative phototrophic organelle for light-driven production of cellular energy. Unlike photosynthetic C fixation, which decreases substantially at colder temperatures, the proton transport activity of PPR was unaffected by decreasing temperature. Cellular PPR levels in cultured SO diatoms increased with decreasing iron concentrations and energy production from PPR photochemistry could substantially augment that of PS, especially under high light intensities, where PS is often photoinhibited. PPR gene expression and high retinal concentrations in phytoplankton in SO waters support its widespread use in polar environments. PPRs are an important adaptation of SO phytoplankton to growth and survival in their cold, iron-limited, and variable light environment.

Coupling the CSM-CROPGRO-Soybean crop model with the ECOSMOS Ecosystem Model – An evaluation with data from an AmeriFlux site

Process-based simulation models, such as land surface (LSM) and crop models, are useful tools for studying the impacts of the environment, management and genotype on agricultural production. LSM are capable of simulating crop development and growth, but not in as much detail as the processes embedded in crop models. Crop models, on the other hand, do not usually have the ability to solve the surface water, energy and carbon balances, which can help to assess the feedbacks between climate and agricultural systems. The goals of this study were first to implement the well-known Cropping System Model (CSM)-CROPGRO-Soybean model of the Decision Support System for Agrotechnology Transfer (DSSAT) into the Ecosystem Model Simulator (ECOSMOS) LSM and then to evaluate this coupling to simulate surface fluxes and crop performance of irrigated and rainfed soybean agroecosystems with comprehensive data from an AmeriFlux site. After model coupling, simulations were benchmarked against multiple flux (carbon dioxide, energy, and water), phenology, growth, and yield observations obtained from field scale experiments across 14 seasons from irrigated and rainfed fields near Mead, Nebraska. Calibration of the physiological parameters of ECOSMOS and of the CROPGRO-Soybean genetic coefficients was conducted. Common metrics were employed to assess model performance. Overall, the coupled model reproduced both the magnitude and seasonal patterns of the energy balance, carbon dioxide exchange, evapotranspiration and soil water balance. The crop model coupling into ECOSMOS preserves the known high skill of the CROPGRO-Soybean model in simulating soybean phenology and growth dynamics. The simulated yields were consistent with the observations at field level. Although the ECOSMOS-CROPGRO-Soybean model is sufficiently robust to simulate surface fluxes and crop performance of soybean agroecosystems at field scale for the environments of eastern Nebraska, further evaluation for a wide range of climatic and soil conditions and management practices is warranted.

Monitoring of carbon-water fluxes at Eurasian meteorological stations using random forest and remote sensing

Simulating the carbon-water fluxes at more widely distributed meteorological stations based on the sparsely and unevenly distributed eddy covariance flux stations is needed to accurately understand the carbon-water cycle of terrestrial ecosystems. We established a new framework consisting of machine learning, determination coefficient (R2), Euclidean distance, and remote sensing (RS), to simulate the daily net ecosystem carbon dioxide exchange (NEE) and water flux (WF) of the Eurasian meteorological stations using a random forest model or/and RS. The daily NEE and WF datasets with RS-based information (NEE-RS and WF-RS) for 3774 and 4427 meteorological stations during 2002–2020 were produced, respectively. And the daily NEE and WF datasets without RS-based information (NEE-WRS and WF-WRS) for 4667 and 6763 meteorological stations during 1983–2018 were generated, respectively. For each meteorological station, the carbon-water fluxes meet accuracy requirements and have quasi-observational properties. These four carbon-water flux datasets have great potential to improve the assessments of the ecosystem carbon-water dynamics.

Changes in CO2 concentration and degassing of eutrophic urban lakes associated with algal growth and decline

Urban lakes are numerous in the world, but their role in carbon storage and emission is not well understood. This study aimed to answer the critical questions: How does algal growing season influence carbon dioxide concentration (cCO2) and exchange flux (FCO2) in eutrophic urban lakes? We investigated trophic state, seasonality of algal productivity, and their association with CO2 dynamics in four urban lakes in Central China. We found that these lightly-to moderately-eutrophic urban lakes showed a shifting pattern of CO2 source-sink dynamics. In the non-algal bloom phase, the moderately-eutrophic lakes outgassed on average of 12.18 ± 24.37 mmol m−2 d−1 CO2; but, during the algal bloom phase, the lakes sequestered an average 1.07 ± 6.22 mmol m−2 d−1 CO2. The lightly-eutrophic lakes exhibited lower CO2 emission in the algal bloom (0.60 ± 10.24 mmol m−2 d−1) compared to the non-algal bloom (3.84 ± 12.38 mmol m−2 d−1). Biological factors such as Chl-a (chlorophyll a) and AOU (apparent oxygen utilization), were found to be important factors to potentially affect the shifting pattern of lake CO2 source-sink dynamics in moderately-eutrophic lakes, explaining 48% and 34% of the CO2 variation in the non-algal and algal bloom phases, respectively. Moreover, CO2 showed positive correlations with AOU, and negative correlations with Chl-a in both phases. In the lightly-eutrophic lakes, biological factors explained a higher proportion of CO2 variations (29%) in the non-algal bloom phase, with AOU accounting for 19%. Our results indicate that algal growth and decline phases largely affect dissolved CO2 level and exchange flux by regulating in-lake respiration and photosynthesis. Based on the findings, we conclude that shallow urban lakes can act as both sources and sinks of CO2, with algal growth seasonality and trophic state playing pivotal roles in controlling their carbon dynamics.