Atmospheric Carbon Dioxide Concentration Research Articles

Examining the sensitivity of the terrestrial carbon cycle to the expression of El Niño

Abstract. The El Niño‐-Southern Oscillation (ENSO) influences the global climate and the variability in the terrestrial carbon cycle on interannual timescales. Two different expressions of El Niño have recently been identified: (i) central Pacific (CP) and (ii) eastern Pacific (EP). Both types of El Niño are characterised by above-average sea surface temperature anomalies at the respective locations. Studies exploring the impact of these expressions of El Niño on the carbon cycle have identified changes in the amplitude of the concentration of interannual atmospheric carbon dioxide (CO2) variability following increased tropical near-surface air temperature and decreased precipitation. We employ the dynamic global vegetation model LPJ-GUESS (Lund–Potsdam–Jena General Ecosystem Simulator) within a synthetic experimental framework to examine the sensitivity and potential long-term impacts of these two expressions of El Niño on the terrestrial carbon cycle. We manipulated the occurrence of CP and EP events in two climate reanalysis datasets during the latter half of the 20th and early 21st century by replacing all EP with CP and separately all CP with EP El Niño events. We found that the different expressions of El Niño affect interannual variability in the terrestrial carbon cycle. However, the effect on longer timescales was small for both climate reanalysis datasets. We conclude that capturing any future trends in the relative frequency of CP and EP El Niño events may not be critical for robust simulations of the terrestrial carbon cycle.

Does Elevated [CO2] Only Increase Root Growth in the Topsoil? A FACE Study with Lentil in a Semi-Arid Environment.

Atmospheric carbon dioxide concentrations [CO2] are increasing steadily. Some reports have shown that root growth in grain crops is mostly stimulated in the topsoil rather than evenly throughout the soil profile by e[CO2], which is not optimal for crops grown in semi-arid environments with strong reliance on stored water. An experiment was conducted during the 2014 and 2015 growing seasons with two lentil (Lens culinaris) genotypes grown under Free Air CO2 Enrichment (FACE) in which root growth was observed non-destructively with mini-rhizotrons approximately every 2–3 weeks. Root growth was not always statistically increased by e[CO2] and not consistently between depths and genotypes. In 2014, root growth in the top 15 cm of the soil profile (topsoil) was indeed increased by e[CO2], but increases at lower depths (30–45 cm) later in the season were greater than in the topsoil. In 2015, e[CO2] only increased root length in the topsoil for one genotype, potentially reflecting the lack of plant available soil water between 30–60 cm until recharged by irrigation during grain filling. Our limited data to compare responses to e[CO2] showed that root length increases in the topsoil were correlated with a lower yield response to e[CO2]. The increase in yield response was rather correlated with increases in root growth below 30 cm depth.

Impacts of climate change and increasing carbon dioxide levels on yield changes of major crops in suitable planting areas in China by the 2050s

Maize, rice, and wheat are the major staple food crops in China and are crucial components of national food security and economic development. The cultivation and production of these crops are expected to be affected by climate change and elevated atmospheric carbon dioxide (CO2) concentration, and have drawn considerable public attention. The objective of this experiment was to understand the impact of future climate change (including increased temperature and changed precipitation patterns) and elevated CO2 concentration on variations of crop yields in their suitable planting areas. We conducted a spatial grid-based analysis of maize, rice, and wheat yields using projections of future climate generated by a multi-model ensemble of global climate models for three representative concentration pathway scenarios (RCP2.6, RCP4.5, and RCP8.5) in suitable planting areas in China for the 2030s (2021–2040) and the 2050s (2041–2060). Suitable areas for the planting of maize, rice, and wheat under the high-emission scenarios migrated slightly northward over time. Yield of all three crops would be expected to remain stable or to slightly increase across China in the future. A possible reason for this result may be because the positive effects of increased precipitation and CO2 offset the negative effect of increased temperature on crop yields, resulting in a much more appropriate growth environment and increased biomass accumulation and crop yield. In addition, this study also indicated that changes in crop yields were mainly driven by temperature and CO2 factors. The potential effects of climate change and elevated CO2 concentration on migration of planting areas and yield fluctuations for crops should be given greater attention in the future.

Anthropogenic CO2 and ocean acidification in Argentine Basin Water Masses over almost five decades of observations.

The chemical conditions of the Argentine Basin (western South Atlantic Ocean) water masses are evaluated with measurements from eleven hydrographic cruises to detect and quantify anthropogenic and natural stressors in the ocean carbon system. The database covers almost half-century (1972-2019), a time-span where the mean annual atmospheric carbon dioxide concentration (CO2atm) increased from 325 to 408ppm of volume (ppm). This increase of atmospheric CO2 (83ppm, the 64% of the total anthropogenic signal in the atmosphere) leads to an increase in anthropogenic carbon (Cant) across all the water column and the consequent ocean acidification: a decrease in excess carbonate that is unequivocal in the upper (South Atlantic Central Water, SACW) and intermediate water masses (Sub Antarctic Mode Water, SAMW and Antarctic Intermediate Water, AAIW). For each additional ppm in CO2atm the water masses SACW, SAMW and AAIW lose excess carbonate at a rate of 0.39±0.04, 0.47±0.05 and 0.23±0.03μmol·kg-1·ppm-1 respectively. Modal and intermediate water masses in the Argentine Basin are very sensitive to carbon increases due low buffering capacity. The large rate of AAIW acidification is the synergic effect of carbon uptake combined with deoxygenation and increased remineralization of organic matter. If CO2 emissions follows the path of business-as-usual emissions (SSP 5.85), SACW would become undersaturated with respect to aragonite at the end of the century. The undersaturation in AAIW is virtually unavoidable.

Elevated temperature and low nitrogen partially offset the yield, evapotranspiration, and water use efficiency of winter wheat under carbon dioxide enrichment

Atmospheric carbon dioxide (CO2) concentration, temperature and nitrogen (N) are the key regulators of productivity and water use of plants under the changing climate. However, field scale studies on the interactive effect of the three above critical inputs are limited. Hence, this field study was conducted with three climate treatments (ambient (AC), elevated CO2 (eC, ~550 µmol mol−1) and co-elevation of both CO2 and temperature (eCeT, ~550 µmol mol−1 and temperature ~2 °C above ambient)) and four N treatments (0%, 50%, 100% and 150% of recommended N dose of 120 kg N ha−1). The experiment was carried out in open top field chambers to study the effects of climate and N application on grain yield, evapotranspiration (ET) and water use efficiency (WUE) in wheat crop. Crop ET was estimated by field water balance method and WUE by taking the ratio of grain yield to crop ET. Elevation of CO2 showed 9% yield gain over ambient (averaged across N levels), whereas, co-elevation of temperature reduced the yield gain to 4%. Further, N application significantly altered the level of CO2 response. Under CO2 enriched environment, the yield gain was 15% with N100 as compared to 2% and 4% under N0 and N50, respectively, indicating CO2 enrichment benefits in grain yield was N dependent. The three years’ pooled data showed significant effect of climate, N and their interaction on profile water storage, evapotranspiration and WUE. Elevation of CO2 alone or with co-elevation of temperature resulted in significant decline in crop ET by 4–11 mm and significant increase in profile soil moisture and WUE. The WUE improved significantly, by 12% under eC and by 4% under eCeT, respectively, with the increase, more attributed to gain in grain yield. Quantitative derivation from the three years’ field experimentation could establish that under elevated CO2 scenario (550 µmol mol−1), an additional 1 °C rise in temperature would result in enhanced crop ET by 5 mm and yield loss of about 4%. This study thus revealed that limited N and increased temperature would potentially restrict the CO2 mediated benefits in wheat yield and water use under the changing climate.

Mechanisms influencing physically sequestered soil carbon in temperate restored grasslands in South Africa and North America

Sequestering carbon (C) into stable soil pools has potential to mitigate increasing atmospheric carbon dioxide concentrations. Carbon accrues in grassland soil restored from cultivation, but the amount of physically protected C (here measured as microaggregate-within-macroaggregate C) and predominant mechanisms of accrual are not well understood. We modeled the rate of physically protected carbon accrued in three mesic temperate perennial restored grasslands from cross-continental regions using datasets with a wide range of restoration ages from northeast Kansas, USA; southeast Nebraska, USA; and northeast Free State, South Africa. Further, we investigated major controls on the amount of physically protected C in each site using structural equation modeling. Variables in the structural equation model were root biomass, root C:N ratio, soil structure (indicated by bulk density, percent of macroaggregates on a per whole soil mass basis, and percent of microaggregate-within-macroaggregates on a per macroaggregate mass basis), microbial composition (indicated by microbial biomass C, total phospholipid fatty acid [PLFA] biomass, and PLFA biomass of arbuscular mycorrhizae fungi [AMF] biomass), and microaggregate-within-macroaggregate C on a per whole soil mass basis. Across all sites, physically protected C accrued at a rate of 16 ± 5 g m−2 year−1. Data from South Africa fit an a priori metamodel developed for northeast KS that hypothesized physically protected C could be explained as a function of microbial composition, soil structure, root C:N ratio, and root biomass (listed in order of strength of direct effect on physically protected C). In contrast to the model-based hypothesis, root C:N ratio was the strongest influence (negative) on physically protected C in South Africa. The lesser effect of AMF on physically protected C in South Africa was consistent with lower AMF biomass in arid environments. The hypothesized model did not fit southeast Nebraska data possibly due to high (~ 30%) clay content. Overall, these results suggest that physically protected C in soil with moderate amounts of clay (more than 10% and less than 30%) can be predicted with knowledge of roots (biomass and C:N ratio), microbial biomass, and soil aggregation.

Differences in carbon isotope discrimination between angiosperm and gymnosperm woody plants, and their geological significance

For most of the Phanerozoic Eon, Earth’s woody vegetation has been dominated by C3 plants - predominantly gymnosperms - with angiosperms only emerging as the dominant plant group as CO2 declined during the Cenozoic (66 Ma onward). At present, differences in carbon isotope discrimination (Δ13C) between angiosperm and gymnosperm plants are relatively small (2–3 ‰), but an increasing body of evidence points to larger differences across geological times (up to 6–7 ‰), potentially associated with varying environmental conditions and atmospheres (i.e. concentrations of atmospheric carbon dioxide, [CO2], and oxygen, [O2] could have ranged from ∼180 to 1100 ppm, and ∼15 to 25%, respectively, across the past 250 Ma). Yet, differences in Δ13C between the two plant groups, and their potential link to climatic and environmental changes, have not yet been fully explored and understood. Here, we combine a comprehensive ab initio model of discrimination, with a recent model of plant eco-physiology based on least-cost optimality theory, to show how differences in Δ13C between angiosperms and gymnosperms arise. We train the comprehensive model using a very large (n>7000) database of leaf and tree ring data spanning the past 110 years. We find that averaged differences in Δ13C between angiosperm and gymnosperms decrease modestly with atmospheric [O2]:[CO2] ratios, and increase strongly with vapor pressure deficit (D). These relationships can be explained by three key physiological differences: (1) the ratio of cost factors for transpiration to carboxylation (higher in angiosperms); (2) the ratio of mesophyll to stomatal conductances of CO2 (lower in gymnosperms); and (3) differences in photorespiration. In particular, the amount of CO2 released from photorespiration per oxygenation reaction, λ, is generally lower in gymnosperms than in angiosperms. As a result of these factors, Δ13C is more sensitive to [CO2] in angiosperms, and to D in gymnosperms. We propose a simplified empirical model to account for this behaviour, and test it against isotopic data from leaves, tree rings and previously-published plant chamber experiments, along with geological data from the Cenozoic. Overall, these data agree with our model over a range of [O2]:[CO2] ratios from 100 to 650 mol mol−1 (equivalent to a CO2 range around 323–2100 ppm at 21% O2), and D levels between 0.45 and 1.1 kPa (R2 = 0.51, RMSE = 1.49 ‰). Our simplified empirical model offers a new explanation for secular trends in the geological record, and suggests a way forward to improve paleo-[CO2] proxies based on terrestrial discrimination models by incorporating the effects of [O2], phylogeny, and photorespiration. Lastly, the framework predicts that the average difference in Δ13C between woody C3 plant groups will increase in the future if both [CO2] and global D continue to rise as suggested by projections.

Ammonium application mitigates the effects of elevated carbon dioxide on the carbon/nitrogen balance of Phoebe bournei seedlings.

The study of plant responses to increases in atmospheric carbon dioxide (CO2) concentration is crucial to understand and to predict the effect of future global climate change on plant adaptation and evolution. Increasing amount of nitrogen (N) can promote the positive effect of CO2, while how N forms would modify the degree of CO2 effect is rarely studied. The aim of this study was to determine whether the amount and form of nitrogen (N) could mitigate the effects of elevated CO2 (eCO2) on enzyme activities related to carbon (C) and N metabolism, the C/N ratio, and growth of Phoebe bournei (Hemsl.) Y.C. Yang. One-year-old P. bournei seedlings were grown in an open-top air chamber under either an ambient CO2 (aCO2) (350±70μmol•mol-1) or an eCO2 (700±10μmol•mol-1) concentration and cultivated in soil treated with either moderate (0.8g per seedling) or high applications (1.2g per seedling) of nitrate or ammonium. In seedlings treated with a moderate level of nitrate, the activities of key enzymes involved in C and N metabolism (i.e., Rubisco, Rubisco activase and glutamine synthetase) were lower under eCO2 than under aCO2. By contrast, key enzyme activities (except GS) in seedlings treated with high nitrate or ammonium were not significantly different between aCO2 and eCO2 or higher under eCO2 than under aCO2. The C/N ratio of seedlings treated with moderate or high nitrate under eCO2was significantly changed compared with the seedlings grown under aCO2, whereas the C/N ratio of seedlings treated with ammonium was not significantly different between aCO2 and eCO2. Therefore, under eCO2, application of ammonium can be beneficial C and N metabolism and mitigate effects on the C/N ratio.

Hybrid Pd50-Ru50/MXene (Ti3C2Tx) nanocatalyst for effective hydrogenation of CO2 to methanol toward climate change control

Increase in atmospheric carbon dioxide (CO2) concentration has motivated researchers to develop large-scale CO2 sequestration and subsequent fuel conversion processes using various nanocatalysts. Herein, a 2D alloyed Pd50-Ru50 nanoparticles decorated MXene (Pd50-Ru50/MXene) nanocatalyst for efficient hydrogenation of CO2 into selective production of methanol is successfully fabricated and analyzed for its performance. HR-TEM and BET studies showed that hexagonal close-packed Pd50-Ru50 was formed with an average size of 3.2 nm and grown on the MXene nanosheets resulting in a higher specific surface area of 120 m2 g−1. Among the various catalysts studied, Pd50-Ru50/MXene showed a superior catalytic activity for hydrogenation of CO2 into selective production of CH3OH. The CO2 hydrogenation process involved the hydrolysis of NaBH4 (H2 facilitator) with ethylene glycol as CO2 capture agent. The Pd50-Ru50/MXene catalyst produced a higher CO2 conversion efficiency of 78% with a CH3OH yield of 76% (total turnover number based on Pd50-Ru50 = 2932) under mild conditions (pCO2 = 10 bar; T = 150 °C; t = 12 h). The recyclability test and morphological analysis of the spent Pd50-Ru50/MXene catalyst demonstrated its chemical stability even after prolonged usage for several hours indicating its promise for commercial-scale CO2 capture and renewable liquid fuel production.

Monitoring Australian Monsoon variability over the past four glacial cycles

We analyse changes in terrigenous sedimentation along the northwestern Australian margin to monitor the latitudinal migration of the Intertropical Convergence Zone (ITCZ) and the shifting boundaries of climatic belts during the last four glacial cycles. We integrate high-resolution X-ray fluorescence (XRF) scanning elemental records from Core SO257–18548 and International Ocean Discovery Program Site U1482, situated southwest of the Scott Plateau at the southern edge of the present-day monsoonal belt, and from Core SO257–18571, located within the dust-cyclone belt offshore Northwest Cape south of the Exmouth Plateau. The chronology of these sediment successions is based on 14C dating over the last glacial termination and on correlation of the benthic oxygen isotope record to the LR04 stack (Lisiecki and Raymo, 200) and Antarctic ice core chronology. Our XRF derived records of riverine terrigenous run-off and aeolian dust input reveal rapid intensification of monsoonal precipitation and reduction of atmospheric dust during the Younger Dryas and early Holocene as well as during the terminal phase of other major deglaciations. Short-lived monsoonal maxima in the early Holocene (~10 ka), MIS 5e (~130 ka), MIS 7 (~200, ~220 and ~ 240 ka), and MIS 9 (~280, ~305 and ~ 330 ka) coincide with maxima in atmospheric carbon dioxide and methane concentrations. Monsoon intensification occurs during maxima in Southern Hemisphere spring (September) insolation, when intense heat low pressure cells over the Pilbara region trigger the southward shift of the ITCZ. Within the dust-cyclone belt, riverine sediment discharge was restricted to intervals of high atmospheric CO2 concentrations, when sea surface temperature thresholds promoted cyclone formation in the tropical Indian Ocean. Northwestern Australia remained dry and arid during MIS 5a-d, when the ITCZ was locked in a more northerly position and temperature thresholds were not attained.

The Evaluation of Ecological Service Value of Liaohe River Estuary Wetland

Taking the wetland of the Liaohe River Estuary as the research object and combined with the emergy theory, aquatic product supply service, plant resource supply service, atmospheric oxygen content regulation service, atmospheric carbon dioxide content regulation service, water regulation service, biological habitat regulation service, scientific research culture service value, leisure and entertainment service value are chosen to evaluate the ecological service value of the Liaohe Estuary wetland in 2019. The results of the study show that the total emergy value of the wetland at the mouth of the Liaohe River is 59.931 billion yuan. Among them, the value of supply services is 2.057 billion yuan. The value of regulation services is 53.508 billion yuan, and the value of cultural services is 4.366 billion yuan. In the entire value of Liaohe estuary wetland, regulation service value>cultural entertainment value>supply service value. Among them, the ecological service value of Liaohe estuary wetland mainly comes from water resource regulation service value and biological habitat regulation service value. Therefore, the ecological service value Research is of great significance to the development and utilization of water resources.

Increased precipitation differentially changed soil CO2 efflux in arid and humid areas

It has been well acknowledged that a continuous increase in atmospheric carbon dioxide (CO2) concentration will lead to climate warming. Numerous experiments have found that increased precipitation could promote soil CO2 emissions into the atmosphere, but there is great uncertainty in the magnitude of increased precipitation of this feedback. Here, we assessed the influences of different durations and magnitudes of increased precipitation on soil CO2 efflux across biomes through a meta-analysis. Humid (extremely wet, moderately wet, and slightly wet), temperate, and arid (slight drought, moderate drought and extreme drought) areas were classified according to the Palmer drought severity index (PDSI). Overall, the average experimentally applied precipitation increases of 31.81%, 19.14% and 37.68% significantly stimulated soil CO2 efflux by 12.74%, 13.10% and 14.71%, respectively for experiments from all areas, humid areas, and arid areas. No significant effects were found for temperate areas. Increased precipitation stimulated large soil CO2 efflux in extreme drought areas (PDSI > −3) by 38.09%. Moreover, soil CO2 efflux increased with increasing precipitation intensity but decreased with increasing precipitation duration regardless of the area with different PDSIs. Our results highlight the positive feedback between soil CO2 efflux and increased precipitation in both humid and arid terrestrial ecosystems, which improves our understanding in possible climate change effects on the global carbon cycle. Further efforts should assess the differential effects of various durations and magnitudes of increased precipitation in ecosystems with different wetness conditions.

Warming and elevated CO2 induces changes in the reproductive dynamics of a tropical plant species

Tropical plant species are vulnerable to climate change and global warming. Since flowering is a critical factor for plant reproduction and seed-set, warming and elevated atmospheric carbon dioxide concentrations (eCO2) are crucial climate change factors that can affect plant reproductive dynamics and flowering related events in the tropics. Using a combined free-air CO2 enrichment and a free-air temperature-controlled enhancement system, we investigate how warming (+2 °C above ambient, eT) and elevated [CO2] (~600 ppm, eCO2) affect the phenological pattern, plant-insect interactions, and outcrossing rates in the tropical legume forage species Stylosanthes capitata Vogel (Fabaceae). In comparison to the control, a significantly greater number of flowers (NF) per plot (+62%) were observed in eT. Furthermore, in warmed plots flowers began opening approximately 1 h earlier (~09:05), with a canopy temperature of ~23 °C, than the control (~09:59) and eCO2 (~09:55) treatments. Flower closure occurred about 3 h later in eT (~11:57) and control (~13:13), with a canopy temperature of ~27 °C. These changes in flower phenology increased the availability of floral resources and attractiveness for pollinators such as Apis mellifera L. and visitors such as Paratrigona lineata L., with significant interactions between eT treatments and insect visitation per hour/day, especially between 09:00–10:40. In comparison to the control, the additive effects of combined eCO2 + eT enhanced the NF by 137%, while the number of A. mellifera floral visits per plot/week increased by 83% during the period of greatest flower production. Although we found no significant effect of treatments on mating system parameters, the overall mean multilocus outcrossing rate (tm = 0.53 ± 0.03) did confirm that S. capitata has a mixed mating system. The effects of elevated [CO2] and warming on plant-pollinator relationships observed here may have important implications for seed production of tropical forage species in future climate scenarios.

Implications of rising atmospheric carbon dioxide concentration on seed quality.

Regeneration of plants through seed is governed by the ability and rate to germinate, which largely depends on the climatic variables prevailing during pre-harvest (mother plant growth) and post-harvest (processing and storage) stages. Atmospheric carbon dioxide concentration [CO2] is increasing rapidly and is expected to surpass 550 ppm within this century. Elevated CO2 (e[CO2]) is reported to influence the mother plant at morphological, phenological, physiological and biochemical levels across the species. Such changes are expected to alter the quality components of the progeny seeds, which has received very little research attention. This review discusses about the possible implications of e[CO2] on quality attributes of seed affecting its planting value with much emphasis on seed weight, germination, vigour and its biochemical constituents. Research indicates that the effect of e[CO2] on seed weight is variable and influenced by the availability of nutrients particularly nitrogen. Likewise, seed germination shows a divergent effect, whereas seed vigour that indicates the strength of a seed usually is compromised under e[CO2]. It generally alters the balance between tissue carbon and nitrogen content, thus impairs the normal C:N ratio in progeny seed, which eventually impacts the next generation crop. For mitigation, while global breeding efforts focused on elite but narrow gene pool across the crop species shredded some of the ecologically important seed traits, such as thick and dark seed coat in legumes, such traits must be considered in designing breeding programs as they provide resilience to various stresses. We have suggested additional potential mitigation strategies and areas for future research.

Mesopelagic microbial carbon production correlates with diversity across different marine particle fractions

The vertical flux of marine snow particles significantly reduces atmospheric carbon dioxide concentration. In the mesopelagic zone, a large proportion of the organic carbon carried by sinking particles dissipates thereby escaping long term sequestration. Particle associated prokaryotes are largely responsible for such organic carbon loss. However, links between this important ecosystem flux and ecological processes such as community development of prokaryotes on different particle fractions (sinking vs. non-sinking) are yet virtually unknown. This prevents accurate predictions of mesopelagic organic carbon loss in response to changing ocean dynamics. Using combined measurements of prokaryotic heterotrophic production rates and species richness in the North Atlantic, we reveal that carbon loss rates and associated microbial richness are drastically different with particle fractions. Our results demonstrate a strong negative correlation between prokaryotic carbon losses and species richness. Such a trend may be related to prokaryotes detaching from fast-sinking particles constantly enriching non-sinking associated communities in the mesopelagic zone. Existing global scale data suggest this negative correlation is a widespread feature of mesopelagic microbes.

Spatial variation of East Asian winter monsoon evolution between northern and southern China since the last glacial maximum

AbstractThe East Asian winter monsoon (EAWM) is one of the most dynamic components of the global climate system. Although poorly understood, knowledge of long-term spatial differences in EAWM variability during the glacial–interglacial cycles is important for understanding the dynamic processes of the EAWM. We reconstructed the spatiotemporal characteristics of the EAWM since the last glacial maximum (LGM) using a comparison of proxy records and long-term transient simulations. A loess grain-size record from northern China (a sensitive EAWM proxy) and the sea surface temperature gradient of an EAWM index in sediments of the southern South China Sea were compared. The data–model comparison indicates pronounced spatial differences in EAWM evolution, with a weakened EAWM since the LGM in northern China but a strengthened EAWM from the LGM to the early Holocene, followed by a weakening trend, in southern China. The model results suggest that variations in the EAWM in northern China were driven mainly by changes in atmospheric carbon dioxide (CO2) concentration and Northern Hemisphere ice sheets, whereas orbital insolation and ice sheets were important drivers in southern China. We propose that the relative importance of insolation, ice sheets, and atmospheric CO2for EAWM evolution varied spatially within East Asia.

Effects of climate change and local environmental factors on long-term tree water-use efficiency and growth of Pseudolarix amabilis and Cryptomeria japonica in subtropical China

It has been well reported in many studies globally that the increased atmospheric carbon dioxide (CO2) concentration has positively influenced plant growth in the past century. However, it is crucial to understand how long the tree growth trend will remain alongside the rising CO2 concentration before it is tipped over. In this study, we focused on studying the long-term tree growth responses to the rising CO2 concentration, in combination with other environmental factors, and its feedback to the changing climate. This study has reported two tree species, Pseudolarix amabilis (P. amabilis) and Cryptomeria japonica (C. japonica), sampled from a subtropical monsoon forest located in eastern China, and established the long-term tree ring chronologies by applying tree ring width measurement and cross dating, and then, basal area increment (BAI) was calculated. Meanwhile, intrinsic water-use efficiency (iWUE) was calculated through the measurement of carbon isotope composition (δ13C) in tree ring samples, and its relationships with BAI and atmospheric CO2 concentration were also quantified. BAI values continuously increased in both P. amabilis and C. japonica with the rising of CO2 concentration until the atmospheric CO2 concentration tipping points were reached, after which tree growth started to decline with the rising CO2, while iWUE exerted a continuous increase trend with the increasing CO2 concentration. Tree growth of both species was more photosynthesis driven before reaching the maximum BAI points, once the tipping points of atmospheric CO2 were passed, leading to the positive feed of forest carbon cycling to climate change and global warming. Therefore, tree growth was more water limitation driven in the last 20 years.

Combined effects of elevated CO2 and temperature on multitrophic interactions involving a parasitoid of plant virus vectors

Atmospheric concentration of carbon dioxide (CO2) is predicted to double by late twenty-first century, likely increasing global temperature by 2.2 °C. Elevated CO2 (eCO2) and temperature (eT) affect agricultural crops as well as pests and their natural enemies. Changes in any part of multitrophic systems due to environmental factors can affect pest infestation and disease dynamics, as well as the effectiveness of biological control programs. Our study evaluated the effects of eCO2 and eT combined on the performance of the parasitoid Aphidius colemani Vierick (Hymenoptera: Braconidae) when its aphid host Rhopalosiphum padi L. (Hemiptera: Aphididae) was exposed to non-infected or Barley yellow dwarf virus (BYDV–PAV) infected wheat (Triticum aestivum L., Poaceae). Using controlled environment chambers, plant physiology and parasitoid performance were examined under ambient (aCO2a aCO2 = 400 ppm, aT = 20 °C) and elevated (eCO2e eCO2 = 800 ppm, eT = 22 °C) conditions. Virus infection reduced plant biomass and chlorophyll content more pronouncedly under eCO2&eT. Developmental time from oviposition to adult emergence of A. colemani significantly decreased under eCO2&eT, on virus-infected and non-infected plants. However, parasitism rate, sex ratio and pupal survivorship remained unchanged under eCO2&eT, regardless of virus infection. Therefore, we incline to suggest that the biocontrol of R. padi by A. colemani will continue being effective in a future climate with similar conditions as studied here. This study provides empirical data on a particular tritrophic system (plant-pest-parasitoid) affected by plant virus and eCO2&eT, essential to complement scientific knowledge about the impact of climate change on complex interactions of agro-ecosystems.

Chemically modified carbonaceous adsorbents for enhanced CO2 capture: A review

The rapidly-increasing concentration of atmospheric carbon dioxide (CO 2 ) gas has become one of the most pressing environmental concerns in recent years. CO 2 capture has become a vital technical solution to minimize environmental CO 2 emissions from various sources. The development of advanced adsorbents for effective CO 2 adsorption is a growing area that has gained significant attention in the materials science field. Hence, in this review we systematically discuss carbonaceous materials including carbon allotropes (carbon nanotubes (CNTs) and graphene oxide (GO)), carbon aerogels (CAs), biochar, polymer-derived carbons, microporous carbons, and mesoporous carbons that are extensively utilized for CO 2 uptakes. The functionalization of carbon materials that have also been reviewed here involved physical/chemical activations using activating agents (KOH, NaOH, K 2 CO 3 , and ZnCl 2 ), doping (N, O, and S), amine modification, carboxylation (-COOH), hybrid/composites formation, and metal oxide impregnation. Studies demonstrated that these all modifications play a very essential role in enhancing the CO 2 adsorption performance as compared to pristine carbons. It is well-acknowledged that the existence of extremely microporous network with ultra-high specific surface area exhibits a dominant role in enhanced CO 2 capture. Among various functionalized carbon-based adsorbents, modified porous activated carbons proved an excellent adsorbent for efficient CO 2 uptakes because of their brilliant textural properties and economical nature. Additionally, modified carbonaceous adsorbents possessed feasible isosteric heat of adsorption, excellent regeneration ability, and shows efficient selective CO 2 adsorption over N 2 . Besides, these studies also summarize future challenges and prospective research pathway that could be commenced for developing effectual adsorbent for an efficient CO 2 storage application by considering various factors. • Carbonaceous materials as adsorbents for CO 2 capture are highlighted. • Functionalization of carbon-based adsorbents for CO 2 capture has been studied. • Recyclability and selective CO 2 adsorption capacities are also discussed. • Chemical modification extensively enhanced the CO 2 adsorption capacities.

Understanding the opportunities of metal–organic frameworks (MOFs) for CO2capture and gas-phase CO2conversion processes: a comprehensive overview

The rapid increase in the concentration of atmospheric carbon dioxide is one of the most pressing problems facing our planet.