Increasing CO2 Concentration Research Articles

The Impact of CO2 Enrichment on Biomass, Carotenoids, Xanthophyll, and Mineral Content of Lettuce (Lactuca sativa L.)

Carbon dioxide (CO2) concentrations affect the growth rate of plants by increasing photosynthesis. Increasing CO2 in controlled environment agriculture (CEA) provides a means to boost yield or decrease daily light integral (DLI) requirements, potentially increasing profitability of growing operations. However, increases in carbon dioxide concentrations are often correlated with decreased nutritional content of crops. The objectives of this experiment were to quantify the effects of carbon dioxide on the growth, morphology, and nutritional content of two lettuce varieties, ‘Rex’ and ‘Rouxai’ under four CO2 concentrations. Applied CO2 treatments were 400, 800, 1200, and 1600 ppm in controlled environment chambers with identical DLI. Lettuce was germinated for eight days in a greenhouse, then transplanted into potting mix and placed in a growth chamber illuminated by fluorescent lights. After 21 days, lettuce was destructively harvested, and fresh weight and plant volume were measured. Anthocyanins, xanthophylls, chlorophyll, and mineral concentration were measured. The lettuce fresh and dry weight increased with increasing CO2 concentrations, with the greatest increases observed between 400 and 800 ppm, and diminishing increases as CO2 concentration further increased to 1200 and 1600 ppm. Violaxanthin was observed to decrease in ‘Rouxai’ with increasing CO2 concentration. Largely, no significant differences were observed in lutein, anthocyanins, and mineral content. Overall, increasing concentrations of carbon dioxide can significantly increase the yield for lettuce in controlled environments, while not significantly reducing many of the nutritional components.

Exploring the Individualized Effect of Climatic Drivers on MODIS Net Primary Productivity through an Explainable Machine Learning Framework

Along with the development of remote sensing technology, the spatial–temporal variability of vegetation productivity has been well observed. However, the drivers controlling the variation in vegetation under various climate gradients remain poorly understood. Identifying and quantifying the independent effects of driving factors on a natural process is challenging. In this study, we adopted a potent machine learning (ML) model and an ML interpretation technique with high fidelity to disentangle the effects of climatic variables on the long-term averaged net primary productivity (NPP) across the Amazon rainforests. Specifically, the eXtreme Gradient Boosting (XGBoost) model was employed to model the Moderate-resolution Imaging Spectroradiometer (MODIS) NPP data, and the Shapley addictive explanation (SHAP) method was introduced to account for nonlinear relationships between variables identified by the model. Results showed that the dominant driver of NPP across the Amazon forests varied in different regions, with temperature dominating the most considerable portion of the ecoregion with a high importance score. In addition, light augmentation, increased CO2 concentration, and decreased precipitation positively contributed to Amazonia NPP. The wind speed for most vegetated areas was under the optimum, which benefits NPP, while sustained high wind speed would bring substantial NPP loss. We also found a non-monotonic response of Amazonia NPP to VPD and attributed this relationship to the moisture load in Amazon forests. Our application of the explainable machine learning framework to identify the underlying physical mechanism behind NPP could be a reference for identifying relationships between components in natural processes.

Potentials of oxymethylene-dimethyl-ether in diesel engine combustion

The increasing CO2 concentration in the atmosphere and the resulting climate change require an immediate and efficient reduction of anthropogenic carbon-dioxide emission. This target can be achieved by the usage of CO2-neutral fuels even with current technologies (Schemme et al. in Int J Hydrogen Energy 45:5395–5414, 2020). Diesel engines in particular are amongst the most efficient prime movers. Using oxymethylene-dimethyl-ether (OME) it is possible to solve the hitherto existing Soot-NOx-Trade-off. OME has bounded oxygen in the molecular chain. This reduces the formation of soot, but equally the calorific value. But in considerance of the physical and chemical properties of OME, it could be useful to optimize the standard diesel engine into an OME engine. As a result, single-cylinder tests were performed to obtain a detailed analysis of the differences between OME3-5 and commercially available DIN EN 590 Diesel. Based on the fact that OME has gravimetrically less than half the calorific value of diesel, twice the fuel mass must be injected for the same energy release in the combustion chamber. Therefore, at the beginning of the investigations, a variation of the injector flow rate was carried out by means of different nozzle hole diameters. The evaluation of the results included the fundamental differences in the combustion characteristics of both fuels and the determination of efficiency-increasing potentials in the conversion of OME3-5. Due to the lower ignition delay and the shorter combustion time of OME, potentials in the optimisation of the injection setting became apparent. Higher energy flows over the combustion chamber wall were noticeable in operation with OME. To get to the bottom of this, the single-cylinder investigations were supported by tests on the optically accessible high-pressure chamber and the single-cylinder transparent engine. The optical images showed a narrower cone angle and greater penetration depth of the OME injection jet compared to the diesel injection jet. This confirmed the results from the single-cylinder tests. This provides further potential in the design of the injector nozzle to compensate for these deficits. Overall, this work shows that operation with OME in a classic diesel engine is possible without any significant loss in efficiency and with little effort in the hardware. However, it is also possible to achieve more efficient use of the synthetic fuel with minor adjustments.

Mechanisms for Zonal Mean Wind Responses in the Thermosphere to Doubled CO2 Concentration

AbstractWe explored mechanisms for the thermospheric zonal mean wind responses to doubled CO2 concentration through investigating the zonal mean momentum balance in the thermosphere using GAIA model simulations in June. The analysis shows that ion drag, molecular viscosity, and meridional pressure gradient force vary 3–20 times more than the other forces due to the doubled CO2 concentration. The three forces strongly attenuate each other; consequently, the increase in zonal mean zonal ion drag dominantly strengthens the southward wind (∼15 ms−1 at maximum) in the northern (summer) hemisphere and latitudes north of 35S. This strengthened ion drag was attributed to increased ion density/relative velocity between ions and neutral particles in the northern/southern hemisphere. Southward of 35, the zonal pressure gradient force and the meridional advection of zonal wind strengthen the southward wind by 4–12 ms−1 in total. On the other hand, the zonal wind is mainly altered by increased meridional pressure gradient force (∼15 ms−1 at maximum) caused by a latitudinally asymmetric response of the thermosphere density to increasing CO2 concentration. Our results suggest that the increased ion density in the northern hemisphere is the underlying trigger for the wind responses to increasing CO2 concentration. Furthermore, we show that the meridional advection was mainly (∼70%) due to that of the DW1 tidal component.

Effect of gradual increase of atmospheric CO2 concentration on nitrate-dependent anaerobic methane oxidation in paddy soils

Nitrate-dependent anaerobic oxidation of methane (AOM) is a new pathway to reduce methane emissions from paddy ecosystems. The elevated atmospheric CO2 concentration can affect methane emissions from paddy ecosystems, but its impact on the process of nitrate-dependent AOM is poorly known. Based on the automatic CO2 control platform with open top chambers and the 13CH4 stable isotope experiments, the responses of the activity of nitrate-dependent AOM, abundance and community composition of Candidatus Methanoperedens nitroreducens (M. nitroreducens)-like archaea to the gradual increase of CO2 concentration were investigated in paddy fields. We set up two CO2 concentration treatments, including an ambient CO2 and a gradual increase of CO2(increase of 40 μL·L-1 per year above ambient CO2 concentration until 160 μL·L-1). The results showed the nitrate-dependent AOM rate of 0.7-11.3 nmol CO2·g-1·d-1 in the studied paddy fields, and quantitative PCR showed the abundance of M. nitroreducens-like archaeal mcrA genes of 2.2×106-8.5×106 copies·g-1. Compared to the ambient CO2 treatment, the slow elevated CO2 treatment enhanced the nitrate-dependent AOM rate and stimulated the abundance of M. nitroreducens-like archaea, particularly in 5-10 cm soil layer. The gradual increased CO2 concentration treatment did not change the community composition of M. nitroreducens-like archaea, but significantly decreased their diversity. The soil organic carbon content was an important factor influencing the nitrate-dependent AOM process. Overall, our results showed that the gradual increase of CO2 concentration could promote the nitrate-dependent AOM, suggesting its positive role in mitigating methane emissions from paddy ecosystems under future climate change.

Warming Climate and Elevated CO2 Will Enhance Future Winter Wheat Yields in North China Region

The projected climate change substantially impacts agricultural productivity and global food security. The cropping system models (CSM) can help estimate the effects of the changing climate on current and future crop production. The current study evaluated the impact of a projected climate change under shared socioeconomic pathways (SSPs) scenarios (SSP2-4.5 and SSP5-8.5) on the grain yield of winter wheat in the North China Plain by adopting the CSM-DSSAT CERES-Wheat model. The model was calibrated and evaluated using observed data of winter wheat experiments from 2015 to 2017 in which nitrogen fertigation was applied to various growth stages of winter wheat. Under the near-term (2021–2040), mid-term (2041–2060), and long-term (2081–2100) SSP2-4.5 and SSP5-8.5 scenarios, the future climate projections were based on five global climate models (GCMs) of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The GCMs projected an increase in grain yield with increasing temperature and precipitation in the near-term, mid-term, and long-term projections. In the mid-term, 13% more winter wheat grain yield is predicted under 1.3 °C, and a 33 mm increase in temperature and precipitation, respectively, compared with the baseline period (1995–2014). The increasing CO2 concentration trends projected an increase in average grain yield from 4 to 6%, 4 to 14%, and 2 to 34% in the near-term, mid-term, and long-term projections, respectively, compared to the baseline. The adaptive strategies were also analyzed, including three irrigation levels (200, 260, and 320 mm), three nitrogen fertilizer rates (275, 330, and 385 kg ha−1), and four sowing times (September 13, September 23, October 3, and October 13). An adaptive strategy experiments indicated that sowing winter wheat on October 3 (traditional planting time) and applying 275 kg ha−1 nitrogen fertilizer and 260 mm irrigation water could positively affect the grain yield in the North China Plain. These findings are beneficial in decision making to adopt and implement the best management practices to mitigate future climate change impacts on wheat grain yields.

Effects of climate change on plant resource allocation and herbivore interactions in a Neotropical rainforest shrub

AbstractClimate change is a mounting global issue, but its consequences will be variable across regions. Tropical species are hypothesized to have reduced climatic adaptability and plasticity. Yet, relative to temperate species, less is understood about how they will respond to climate change. Rising temperature and atmospheric CO2 could impact plant–herbivore systems directly by altering species traits or abundances, or the effects could be indirect by altering the strength and direction of the relationships that govern organismal strategies and interactions. Using open‐top chambers in a Neotropical wet forest, we applied a full‐factorial combination of active warming and CO2 fertilization to investigate the above‐ground, short‐term effects of climate change on plant–herbivore interactions in a common Neotropical shrub, Piper generalense. We aimed to answer two main questions: (1) Could climate change alter plant–herbivore systems through direct effects on plant growth rate, chemical defense, and/or insect herbivore damage rate? and (2) Could climate change affect plant–herbivore systems indirectly by altering (a) the strength of plant resource allocation trade‐offs between growth and defense or (b) the effectiveness of plant chemical defense against herbivory? None of the microclimate treatments had direct effects on plant growth, chemical defense, or herbivore damage. However, we did observe a positive relationship between growth and chemical defense in treatments mimicking climate‐change conditions, which partially supports the growth–differentiation balance hypothesis. We did not detect any effects of treatments on the effectiveness of plant chemical defense against herbivory. It appears that, in this system, increased CO2 concentration and temperature may cause indirect, cascading consequences, even where direct effects are not observable. We recommend more climate‐change experiments addressing multi‐trophic interactions that focus not only on the direct responses of organisms but also on the ways in which climate change can restructure the relationships that govern complex biotic systems.

Weak Hadley cell intensity changes due to compensating effects of tropical and extratropical radiative forcing

The Hadley cell response to globally increasing CO2 concentrations is spatially complex, with an intensified rising branch and weakened descending branch. To better understand these changes, we examine the sensitivity of the Hadley cell to idealized radiative forcing in different latitude bands. The Hadley cell response is, to first order, governed by the latitudinal structure of the forcing. The strengthening of the upward branch is attributed to tropical forcing, whereas the weakening of the descending branch is attributed to extratropical forcing. These direct radiatively-forced Hadley cell responses are amplified by changes in atmospheric eddy heat transport while being partially offset by changes in gross moist stability and ocean heat uptake. The radiative feedbacks further modulate the Hadley cell response by altering the meridional atmospheric energy gradient. The Hadley cell projections under global warming are thus a result of opposing – and thus compensating – effects from tropical and extratropical radiative forcings.

Thermochemical study of CO2 capture by mesoporous silica gel loaded with the amino acid ionic liquid 1-ethyl-3-methylimidazolium glycinate

A series of composite CO2 sorbents were obtained by placing an amino acid ionic liquid (AAIL) 1-Ethyl-3-methylimidazolium glycine ([Emim][Gly]) into mesoporous silica gel using an impregnation method. The parameters of the porous structure for the silica support and composite sorbents were determined from nitrogen adsorption-desorption isotherms measured at 77 K. The morphology of the materials was studied using field-emission scanning electron microscopy. It was shown that at lower [Emim][Gly] loadings (<50 wt%), the sorption is fast and the dynamic CO2 sorption capacity of the material is proportional to the mass content of the AAIL. At higher [Emim][Gly] loadings (≥50 wt%), the rate of CO2 sorption by the AAIL decreases due to hindered mass transfer. An increase in CO2 concentration in the gas flow leads to a faster sorption and higher CO2 sorption capacity for the AAIL-containing composite. Meanwhile, the integral enthalpy of sorption decreases with increasing CO2 concentration, which can be explained by the greater contribution of physical adsorption/absorption processes to the total CO2 sorption capacity at higher CO2 concentrations. The most promising composite material (40 wt% [Emim][Gly]/SiO2) was tested in consecutive temperature-swing sorption-desorption cycles. It was demonstrated that lowering the regeneration temperature from 100 to 80 °C leads to a decrease in the dynamic sorption capacity of the material, but ensures its stability in the cyclic sorption-desorption process.

Effects of anthropogenic nitrogen additions and elevated CO2 on microbial community, carbon and nitrogen content in a replicated wetland.

Anthropogenic deposition of nitrogen (N) and elevated CO2 (eaCO2) are expected to increase continuously and rapidly in the near future and influence global carbon cycling. These parameters affect the ecosystem by regulating the microbial community and contribute to soil organic matter decomposition. The study was performed to understand the effects of N additions (4 and 6mgl-1) and eaCO2 (700ppm) on carbon (C)/nitrogen (N) content in the soil, microbial community, and plant biomass (Alternanthera philoxeroides species). The results showed that when the atmospheric CO2 concentration was raised, the total organic carbon (TOC) in the soil statistically increased (P < 0.05) by 4% and 3% under low and high N additions respectively, while the inorganic carbon content also increased by 1% and 3% (P > 0.05) under the same conditions. The increase in the soil TOC content was a result of the movement of carbon from water to the soil due to the presence of vascular tissues of plants in the water. The redundancy analysis (RDA) results revealed that the presence of plant species was responsible for the carbon content increment in the soil. The plant biomass content increased by 30.96% (P = 0.081) and 31.36%, (P = 0.002) under low and high N addition respectively due to the increment in atmospheric CO2. The nitrogen content in the plant species decreased (p > 0.05) by 8.62% and 6.25% at low and high N addition respectively when atmospheric CO2 was raised. This suggests that soil microbes competed with the plants for inorganic nitrogen in the soil and the microbes used up the inorganic nitrogen before it got to the plants. The gram-positive bacteria and fungi population decreased under high N addition and eaCO2 while gram-negative bacteria increased, suggesting that N additions and eaCO2 affected the microbial function and correlated with the nitrogen reduction in the soil. The results from this study serve as a guide to researchers and stakeholders in making policies with regard to the constant increasing CO2 concentration in the atmosphere.

Tailoring a Three-Phase Microenvironment for High-Performance CO2 Electroreduction

Modern industrialization is accompanied with the extensive usage of fossil fuels for energy demands and consequently, an excessive emission of CO2 into the atmosphere. To combat the injurious greenhouse effects, the CO2 electroreduction (CER) to feedstocks and fuels becomes an appealing approach to reducing CO2 emission and simultaneously producing useful products. It is generally recognized that the solid-catalyst/liquid-electrolyte/gaseous-CO2 triple-phase boundary is the key microstructure feature of CER, where CO2 molecules react with protons (H+) and e− and are reduced. Besides the intrinsic activity of catalyst itself and the accessibility of active sites, CER performance also strongly depends on the transport of H+ and CO2 molecules through electrolyte to catalyst surface. Apparently, the availability of H+ in aqueous solution can be readily achieved via H2O ionization, while the low solubility of CO2 limits the supply of CO2 to the catalyst surface. Moreover, previous study has demonstrated that complete depletion of CO2 on the catalyst surface can even occur when high overpotential is applied.1 In this regard, rationally designing the structure of catalyst to increase the concentration of CO2 at the triple-phase boundary is immensely significant for CER since this could overcome the limited diffusion of CO2 in aqueous medium.Recently, surface hydrophobicity engineering has been proved to be a wise tactic to increase the local CO2 concentration by trapping CO2 near the catalyst surface, thus improving CO2 electrolysis. For example, modification of the hydrophobic organics on catalyst surface could create triple-phase boundary and increase CO2 concentration on catalyst surface, these improved CER performance and simultaneously inhibited HER.2 Unfortunately, the insulative organics coated on the catalyst surface will sacrifice its activity, while some small pieces of organics may desorb from the surface or in the case of flow cell, these pieces can be flushed away by the fluid. Since most catalysts are in situ grown on carbon support with the advantages of rapid electron transfer and seamless contact,3, 4 it is possible to tailor the microenvironment around the catalyst through chemical modification of carbon support. For example, platinum-based catalysts supported on hydrophobic carbon with a desirable microenvironment display a state-of-the-art catalytic activity for oxygen reduction reaction.5 However, few studies have been conducted to investigate how the carbon support can be modified to create a favourable triple-phase boundary for CER.In this study, we have in situ grown Bi2O3 nanosheets (NSs) on two types of carbon materials, hydrophobic carbon nanofiber (Bi2O3@C/HB) and hydrophilic carbon nanofiber (Bi2O3@C/HL), respectively, and used them as the cathode catalysts for CER. Compared to Bi2O3@C/HL, the as-obtained Bi2O3@C/HB exhibits significantly boosted CER performances for formate formation with the high FEformate of ˃ 93% over an extremely wide potential window of 1000 mV, high formate partial current density (jformate ) of 102.1 mA cm−2 and high formate formation rate of 1905 μmol h−1 cm−2. Molecular dynamics (MD) simulations together with electrochemical measurements reveal that the hydrophobic carbon support can create a hydrophobic microenvironment by avoiding the formation of hydrogen bond. This increases the local CO2 concentration and pH, both contributing to the enhancement of the overall CER. We believe that the findings from this work can provide significant guidelines for designing highly active CER catalysts and showcase a promising approach to improving other types of electrolysis involving gas phase. Raciti, D.; Mao, M.; Park, J. H.; Wang, C., Mass transfer effects in CO2 reduction on Cu nanowire electrocatalysts. Catal. Sci. Technol. 2018, 8, 2364-2369.Wang, J.; Cheng, T.; Fenwick, A. Q.; Baroud, T. N.; Rosas-Hernández, A.; Ko, J. H.; Gan, Q.; Goddard Iii, W. A.; Grubbs, R. H., Selective CO2 Electrochemical Reduction Enabled by a Tricomponent Copolymer Modifier on a Copper Surface. J. Am. Chem. Soc. 2021, 143, 2857-2865.Liu, S.; Lu, X. F.; Xiao, J.; Wang, X.; Lou, X. W., Bi2O3 nanosheets grown on multi‐channel carbon matrix to catalyze efficient CO2 electroreduction to HCOOH. Angew. Chem., Int. Ed. 2019, 58, 13828-13833.Li, F.; Chen, L.; Knowles, G. P.; MacFarlane, D. R.; Zhang, J., Hierarchical mesoporous SnO2 nanosheets on carbon cloth: a robust and flexible electrocatalyst for CO2 reduction with high efficiency and selectivity. Angew. Chem., Int. Ed. 2017, 56, 505-509.Zhao, Z.; Hossain, M. D.; Xu, C.; Lu, Z.; Liu, Y.-S.; Hsieh, S.-H.; Lee, I.; Gao, W.; Yang, J.; Merinov, B. V., Tailoring a Three-Phase Microenvironment for High-Performance Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells. Matter 2020, 3, 1774-1790.

The role of mycorrhiza in food security and the challenge of climate change

Before the Industrial Revolution, the concentration of CO2 in the atmosphere was 280 ppm and in time increasing fossil fuels use increased CO2 concentration up to 416 ppm in a preset time. Meanwhile, increasing population growth (around 8 billion) has also started to put serious pressure on soil ecosystem for more food production demand. With the demand for more food production, intensive chemical inputs and soil cultivation practices applied to the soil has increased the amount of CO2 released to the atmosphere. Increasing CO2 concentration in the atmosphere triggers global warming and climate change which is negatively affect plant growth and consequently food security. In order to ensure food security under climate change conditions, it seems that the need to re-enact nature's own mechanisms has arisen. In this context, it is aimed to reduce the effect of climate changes by keeping more carbon as a sink by operating the effects of plant root mechanisms on the soil health according to ecological principles. Under long term filed conditions the effects of different soil-plant managements, especially mycorrhiza fungi, were investigated. Since 1996, several researches have been carried out under long-term field studies to see the effect of mycorrhizal fungi and other microorganisms on carbon sequestration, as well as the emission of CO2 from the greenhouse gases to the atmosphere. Regularly CO2 flux, emissions, photosynthesis rate, C, N sequestration and yield parameters are measured. Data are yearly evaluated. Results revealed that under long-term field conditions, organic fertilizers application and mycorrhizal inoculation sequestered more carbon in soil profile. It has been shown that, using animal manure, compost, biochar, nitrogen-fixing bacteria and mycorrhizal fungi significantly kept more carbon in plant tissue and soil. It is determined that there is an increase of 1.5 ppm CO2 concentration in atmosphere per year. It has been determined that especially long-term addition of organic matter and management of natural mycorrhizae increase soil organic carbon and accordingly soil quality and productivity increase. As the effect of climate change and population growth have significant negative impact on food security, definitely a new agriculture revelation is needed to overcome of climate and food security problem. Soil and plant management must be managed according to low-input ecological principles.

Effects of CO2 concentration and light intensity on macromolecules accumulation of Micractinium sp.

Economically efficient biomass production is crucial to lift the microalgal circular bioeconomy requiring low production cost with higher biomass and value-added products. In this study, Micractinium sp. YACCYB505 was cultured at different illuminations (1600, 2400, 3200 lux) and CO2 conditions (up to 10%) to evaluate biomass productivity and accumulation of macromolecules (lipid, carbohydrate and protein). The product optimization study was conducted to analyze individual variables of environmental factors by using a Box-Behnken design. Highlight intensity (3200 lux) and 5% CO2 aeration maximized biomass productivity on 11th day of microalgal harvest. Microalgal lipid accumulation indicated positive impact on increased CO2 aeration and light intensity treatment. Similarly, a considerable amount of protein content (9%) was increased at higher CO2 aeration but raised light intensity had a negative impact on protein biosynthesis. Significant carbohydrate content reduction was observed with increased light intensity and CO2 aeration. The overall results proved that increased CO2 concentration (10%) and light intensity (3200 lux) enhanced lipid accumulation (32%) and biomass productivity in Micractinium sp., which provides potential to achieve a sustainable, cost-effective biomass and value-added products.

Cropland Exposed to Drought Is Overestimated without Considering the CO2 Effect in the Arid Climatic Region of China

Drought seriously restricts people’s lives and social–economic development. An accurate understanding of the evolution of drought characteristics and future changes in cultivated land exposure can reduce the risk of drought. There is evidence that increased CO2 concentrations alter the physiological properties of vegetation and, thus, affect drought evolution. In this study, both changes and differences in drought (i.e., characteristics and cropland exposure) with and without the CO2 effect over the arid region of China are investigated, using seven CMIP6 outputs and land-use under seven shared-socioeconomic-pathway (SSP)-based scenarios. The results show that: (1) drier conditions will be more severe in 2015–2100 under SSP5-8.5, especially if the CO2 effect is neglected. Moreover, the CO2 effect will increase with increasing emission concentrations; (2) drought intensity will be greater than in the baseline period (1995–2014, approximately −1.45) but weaker than that without the CO2 effect under all scenarios; (3) drought frequency will decrease, and will generally decline faster if the CO2 effect is not considered; (4) drought duration will increase and the difference between the presence and absence of the CO2 effect will always be smallest under SSP1-1.9 and largest under SSP5-8.5; (5) drought acreage will also increase, and neglecting the CO2 effect is always higher than that considering CO2. The difference between the two algorithms will increase with time; and (6) cropland exposure to drought will increase, and can even reach 669,000 km2 and 524,000 km2 considering and ignoring the CO2 effect, respectively. Our findings suggest that ignoring CO2 in drought evaluations will result in significant overestimations of drought projections.

Access to Cleaning Services Alters Fish Physiology Under Parasite Infection and Ocean Acidification.

Cleaning symbioses are key mutualistic interactions where cleaners remove ectoparasites and tissues from client fishes. Such interactions elicit beneficial effects on clients’ ecophysiology, with cascading effects on fish diversity and abundance. Ocean acidification (OA), resulting from increasing CO2 concentrations, can affect the behavior of cleaner fishes making them less motivated to inspect their clients. This is especially important as gnathiid fish ectoparasites are tolerant to ocean acidification. Here, we investigated how access to cleaning services, performed by the cleaner wrasse Labroides dimidiatus, affect individual client’s (damselfish, Pomacentrus amboinensis) aerobic metabolism in response to both experimental parasite infection and OA. Access to cleaning services was modulated using a long-term removal experiment where cleaner wrasses were consistently removed from patch reefs around Lizard Island (Australia) for 17 years or left undisturbed. Only damselfish with access to cleaning stations had a negative metabolic response to parasite infection (maximum metabolic rate—ṀO2Max; and both factorial and absolute aerobic scope). Moreover, after an acclimation period of 10 days to high CO2 (∼1,000 µatm CO2), the fish showed a decrease in factorial aerobic scope, being the lowest in fish without the access to cleaners. We propose that stronger positive selection for parasite tolerance might be present in reef fishes without the access to cleaners, but this might come at a cost, as readiness to deal with parasites can impact their response to other stressors, such as OA.

A promising controllable CO2 capture and separation materials for CO2/CH4/H2 under electric field

As the greenhouse effect concerns increases, the development of new materials for the efficient capture and separation of CO2 gas from gas mixtures has become a matter of urgency. In this study, we performed density functional theory (DFT) calculations to investigate the adsorption and separation behavior of CO2/CH4/H2 on the surface of two-dimensional (2D) Al2C materials under positive/negative applied electric fields. In the absence of an electric field CO2 is weakly physisorbed on the Al2C surface, but with the application of an applied electric field, the adsorption state of CO2 gradually changes from physical to chemisorption (adsorption energy changes from −0.29 eV to −3.61 eV), while the negative electric field has little effect on the adsorption of CO2. We conclude that the C=O bond in adsorbed CO2 can be activated under an external electric field (maximum activation of 15% under an external electric field of 0–0.005 a.u.). Only in the presence of an applied electric field of 0.0033 a.u. and temperatures above 525 K/675 K can the adsorption/separation reaction of CO2 single adsorption and CO2/CH4/H2 mixture be spontaneous. The adsorption/desorption of CO2 on Al2C nanosheet in an electric field of 0.003–0.0033 a.u. is all exothermic, which can be easily controlled by switching on/off the electric field without any energy barriers. The capacity of Al2C to capture CO2 per unit electric field decreases with increasing CO2 concentration, but still has efficient gas separation properties for CO2/CH4/H2. Our theoretical results could provide guidance for designing high-capacity and high-selectivity CO2 capture materials.

Induced Genetic Variations in Stomatal Density and Size of Rice Strongly Affects Water Use Efficiency and Responses to Drought Stresses.

Rice (Oryza sativa L.) is an important food crop relied upon by billions of people worldwide. However, with increasing pressure from climate change and rapid population growth, cultivation is very water-intensive. Therefore, it is critical to produce rice that is high-yielding and genetically more water-use efficient. Here, using the stabilized fast-neutron mutagenized population of Jao Hom Nin (JHN) - a popular purple rice cultivar - we microscopically examined hundreds of flag leaves to identify four stomatal model mutants with either high density (HD) or low density (LD) stomata, and small-sized (SS) or large-sized (LS) stomata. With similar genetic background and uniformity, the stomatal model mutants were used to understand the role of stomatal variants on physiological responses to abiotic stress. Our results show that SS and HD respond better to increasing CO2 concentration and HD has higher stomatal conductance (gs) compared to the other stomatal model mutants, although the effects on gas exchange or overall plant performance were small under greenhouse conditions. In addition, the results of our drought experiments suggest that LD and SS can better adapt to restricted water conditions, and LD showed higher water use efficiency (WUE) and biomass/plant than other stomatal model mutants under long-term restricted water treatment. Finally, our study suggests that reducing stomata density and size may play a promising role for further work on developing a climate-ready rice variety to adapt to drought and heat stress. We propose that low stomata density and small size have high potential as genetic donors for improving WUE in climate-ready rice.

Diurnal Rainfall Response to the Physiological and Radiative Effects of CO2 in Tropical Forests in the Energy Exascale Earth System Model v1

AbstractUnderstanding how the connection between rainfall and tropical forests will respond to increasing CO2 concentrations is a key element in understanding how the tropical water cycle will respond to increasing CO2. The plant physiological and radiative impacts of CO2 on rainfall patterns over tropical forest regions are examined in the Energy Exascale Earth System Model version 1.1 (E3SMv1.1‐BGC) biogeochemistry experiments. Composite analysis reveals a dampening of the diurnal cycle of rainfall over the Amazon, Congo, and Maritime Continent in response to rising CO2 levels, regardless of the sign of total rainfall change. A full factorial model experiment confirms that the CO2 radiative and CO2 plant physiological effects can individually or jointly reduce the magnitude of the rainfall diurnal cycle, though the physical pathway giving rise to the reduction differs between the two effects. For the physiological response, stomatal closure reduces evapotranspiration, which dries the boundary layer and raises the lifting condensation level. These effects combine to reduce deep convective rainfall during its peak occurrence in the late daytime to early nighttime period. For the radiative response, a relative reduction in daytime Convective Available Potential Energy (consistent with a reduction in the diurnal temperature range) leads to less frequent triggering of deep convection and a reduction of rainfall diurnal amplitude. These diurnal rainfall changes are structurally similar across seasons, and show little sensitivity to representation of nutrient coupling for the land biogeochemistry. In agreement with previous findings, the physiological response has only minor impact on extreme rainfall relative to the radiative response.

Simulated global climate change benefits the nutritive value of oat grass.

Numerous data demonstrate that global climate change affects crop yield and quality. However, the effect of climate change on the nutritive value of forage crops remains unclear. Oat grass (Avena sativa L.) was used as a representative forage crop to understand changes in yield and chemical composition. The growth of oat grass under elevated temperature and CO2 conditions was simulated in a 51-day growth experiment inside OTCs. The oat grass was harvested during the heading period and yield, nutrient content, macro- and micro-mineral content and in vitro dry matter digestibility (IVDMD) determined. The fresh and dry yield, mineral P and Fe content and IVDMD of oat grass increased under increased CO2 concentrations (P < 0.05). As temperature increased, dry matter yield and soluble sugar content decreased and the content of Na, Mg, P, S, Ca, Mn, Fe, Cu and Zn increased (P < 0.05), while IVDMD was not significantly affected. Under the interaction of increasing CO2 and temperature, the content of Mg, P, S, Ca, Mn and IVDMD of oat grass increased (P < 0.05); however, there was no significant effect on yield. Climate change may result in oat grass containing more digestible nutrients and minerals for ruminants.

The Diel and Seasonal Heterogeneity of Carbonate Chemistry and Dissolved Oxygen in Three Types of Macroalgal Habitats

As concerns about ocean acidification continue to grow, the importance of macroalgal communities in buffering coastal seawater biogeochemistry through their metabolisms is gaining more attention. However, studies on diel and seasonal fluctuations in seawater chemistry within these communities are still rare. Here, we characterized the spatial and temporal heterogeneity in diel and seasonal dynamics of seawater carbonate chemistry and dissolved oxygen (DO) in three types of macroalgal habitats (UAM: ulvoid algal mat dominated, TAM: turf algal mat dominated, and SC: Sargassum horneri and coralline algae dominated). Our results show that diel fluctuations in carbonate parameters and DO varied significantly among habitat types and seasons due to differences in their biological metabolisms (photosynthesis and calcification) and each site’s hydrological characteristics. Specifically, carbonate parameters were most affected by biological metabolisms at the SC site, and by environmental variables at the UAM site. Also, we demonstrate that macroalgal communities reduced ocean acidification conditions when ocean temperatures supported photosynthesis and thereby the absorption of dissolved inorganic carbon. However, once temperatures exceeded the optimum ranges for macroalgae, respiration within these communities exceeded photosynthesis and increased CO2 concentrations, thereby exacerbating ocean acidification conditions. We conclude that the seawater carbonate chemistry is strongly influenced by the metabolisms of the dominant macroalgae within these different habitat types, which may, in turn, alter their buffering capacity against ocean acidification.