Elevated Atmospheric CO2 Research Articles

Elevated atmospheric CO2 suppresses silicon accumulation and exacerbates endophyte reductions in plant phosphorus

Abstract Many temperate grasses are both hyper‐accumulators of silicon (Si) and hosts of Epichloë fungal endophytes, functional traits which may alleviate environmental stresses such as herbivore attack. Si accumulation and endophyte infection may operate synergistically, but this has not been tested in a field setting, nor in the context of changing environmental conditions. Predicted increases in atmospheric CO2 concentrations can affect both Si accumulation and endophyte function, but these have not been studied in combination. We investigated how elevated atmospheric CO2 (eCO2), Si supplementation, endophyte‐presence and insect herbivory impacted plant growth, stoichiometry (C, N, P and Si), leaf gas exchange (rates of photosynthesis, stomatal conductance, transpiration rates) and endophyte production of anti‐herbivore defences (alkaloids) of an important pasture grass (tall fescue; Lolium arundinaceum) in the field. eCO2 and Si supplementation increased shoot biomass (+52% and +31%, respectively), whereas herbivory reduced shoot biomass by at least 35% and induced Si accumulation by 24%. Shoot Si concentrations, in contrast, decreased by 17%–21% under eCO2. Si supplementation and herbivory reduced shoot C concentrations. eCO2 reduced shoot N concentrations which led to increased shoot C:N ratios. Overall, shoot P concentrations were 26% lower in endophytic plants compared to non‐endophytic plants, potentially due to decreased mass flow (i.e. observed reductions in stomatal conductance and transpiration). Alkaloid production was not discernibly affected by any experimental treatment. The negative impacts of endophytes on P uptake were particularly strong under eCO2. We show that eCO2 and insect herbivory reduce and promote Si accumulation, respectively, incorporating some field conditions for the first time. This indicates that these drivers operate in a more realistic ecological context than previously demonstrated. Reduced uptake of P in endophytic plants may adversely affect plant productivity in the future, particularly if increased demand for P due to improved plant growth under eCO2 cannot be met. Read the free Plain Language Summary for this article on the Journal blog.

A meta-analysis suggests climate change shifts structure of regional communities of soil invertebrates

Soil animals perform a range of essential ecosystem functions and can modify the effects of global change on terrestrial ecosystems. We evaluated responses of six major groups of soil animals (Acari (all groups), Oribatida, Collembola, Insecta, Nematoda, and Oligochaeta) to controlled changes in air temperature, precipitation level or carbon dioxide concentration by using random-effects modelling and mixed-effects meta-regression modelling. Along with the three global change factors, sixteen local climatic characteristics (such as mean annual temperature, Köppen climate classification, vegetation type) were tested. Overall, 86 studies comprising 236 observations with mean duration of 51 months were selected as relevant for the analysis. Quantitative links between global change factors, local climate characteristics and changes in abundance of four taxonomic groups of soil animals were revealed. Warming and precipitation level were associated most strongly with population dynamics of soil invertebrates compared to elevated atmospheric CO2. Each 1 °C increase in air temperature was correlated with a mean of 12.5% (95% CI: 2.5%–22.6%) increase in Acari abundance, while populations of Collembola were declined by 9.6% (95% CI: −17.8% to −1.4%). Meanwhile, each 10% increase in precipitation level was correlated with the increase in the abundance of Nematoda by 1.4% (95% CI: −7.6% to 10.4%) and Oligochaeta by 34.7% (95% CI: 8.1%–61.2%). Considering IPCC estimates (SSP3-7.0 Scenario) of an average climate warming by 3.6 °C and a substantial variation in local precipitation levels (up to ±20%) by the end of the 21st century, strong local changes in the structure of detrital food webs are predicted by meta-regression models. In regions with decreased precipitation, the formation of soil food webs promoting carbon mineralization may be expected, while in regions with increased precipitation, the changes in detrital food web structure can contribute to the accumulation of carbon in the soil.

Exploring reaction and carbonation products of calcium silicate cement

Calcium silicate cement (CSC) can be a promising cementitious binder for its reduced CO2 footprint in comparison with ordinary Portland cement, while its detailed chemical information remains undisclosed. Herein, we present thermodynamic calculation results that illustrate the effect of reaction and carbonation degrees on the reaction products of CSC that undergoes the hardening process at an elevated atmospheric CO2 concentration. The obtained simulation results are discussed in relation to stability of phases. It is revealed that C-S-H can be a stable and strength-giving phase when the carbonation degree is less than one-third of the reaction degree. Amorphous aluminosilicate and calcite become the main binding phases at higher carbonation degrees when C-S-H is depleted.

MORE PANICLES 3, a natural allele of OsTB1/FC1, impacts rice yield in paddy fields at elevated CO2 levels

Improving crop yield potential through an enhanced response to rising atmospheric CO2 levels is an effective strategy for sustainable crop production in the face of climate change. Large-sized panicles (containing many spikelets per panicle) have been a recent ideal plant architecture (IPA) for high-yield rice breeding. However, few breeding programs have proposed an IPA under the projected climate change. Here, we demonstrate through the cloning of the rice (Oryza sativa) quantitative trait locus for MORE PANICLES 3 (MP3) that the improvement in panicle number increases grain yield at elevated atmospheric CO2 levels. MP3 is a natural allele of OsTB1/FC1, previously reported as a negative regulator of tiller bud outgrowth. The temperate japonica allele advanced the developmental process in axillary buds, moderately promoted tillering, and increased the panicle number without negative effects on the panicle size or culm thickness in a high-yielding indica cultivar with large-sized panicles. The MP3 allele, containing three exonic polymorphisms, was observed in most accessions in the temperate japonica subgroups but was rarely observed in the indica subgroup. No selective sweep at MP3 in either the temperate japonica or indica subgroups suggested that MP3 has not been involved and utilized in artificial selection during domestication or breeding. A free-air CO2 enrichment experiment revealed a clear increase of grain yield associated with the temperate japonica allele at elevated atmospheric CO2 levels. Our findings show that the moderately increased panicle number combined with large-sized panicles using MP3 could be a novel IPA and contribute to an increase in rice production under climate change with rising atmospheric CO2 levels.

Warm acidified seawater: a dolomite solution

ABSTRACTThe “dolomite problem” is the product of two distinct observations. First, there are massive amounts of ancient marine limestone (CaCO3) deposits that have been replaced by the mineral dolomite (MgCa(CO3)2). However, recent (Holocene and Pleistocene) marine deposits contain relatively minuscule amounts of dolomite, although the occurrence of small quantities of dolomite is observed in many modern settings, from deep marine to supratidal. Second, low-temperature synthesis of dolomite in laboratory settings has been elusive, particularly in comparison to the ease with which common marine calcium carbonate minerals (aragonite and calcite) can be synthesized. Since low-temperature solid-state diffusion can be discounted as a method for Mg incorporation into calcium carbonate (as it operates on time scales too long to matter), the replacement of CaCO3 by dolomite is one of dissolution followed by precipitation. Therefore, an often overlooked but required factor in the replacement of limestone by dolomite is that of undersaturation regarding the original calcium carbonate mineral during replacement. Such conditions could conceivably be caused by rapid dolomite growth relative to aragonite and calcite dissolution–precipitation reactions, but laboratory studies, modern systems analyses, and observations of ancient deposits all point to this possibility being uncommon because dolomite growth is kinetically inhibited at low temperature. Pressure solution by force of dolomite crystallization is a second possible driver for CaCO3 undersaturation, but requires a confining stress most likely attained through burial. However, based on petrographic observations, significant amounts of ancient dolomite replaced limestone before burial (synsedimentary dolomite), and many such platforms have not suffered any significant burial. Because these possibilities of undersaturation caused by dolomite precipitation and crystal growth can be largely discounted, the undersaturation required for “dolomitization” to proceed is most likely to be externally forced. In modern natural systems, undersaturation and selective CaCO3 dissolution in marine porewaters is very common, even in warm-water environments, being forced by the breakdown of organic matter. Such dissolution is frequently attended, to varying degrees, by precipitation of a kinetically-less-favored but thermodynamically more stable phase of CaCO3. Laboratory studies as well as observations of modern systems show that when undersaturation is reached with respect to all common marine CaCO3 phases, dolomite assumes the role of this kinetically-less-favored precipitate. This degree of undersaturation is uncommon in modern shallow marine pore systems in warm-water settings, but it was more common during times of elevated atmospheric CO2, and ocean acidification. Furthermore, because oxidation of organic matter drives dolomite formation, near-surface organic-rich deposits such as the remains of microbial mat communities, were more predisposed to dolomite replacement in the acidified oceans of the ancient past relative to contemporaneous deposits that contained less organic matter. These observations lend to a more harmonious explanation for the abundance and occurrence of dolomite through time.

Grain Quality and Improvement in Wheat and Some Quality Aspect of Pasta Industries in Ethiopia: A Review

Depending on the intended use, quality can relate to a variety of physical and chemical characteristics of the product. Additionally, the standards for judging wheat grain quality attributes are as varied as their various applications. The impacts of some important genes for grain hardness, genes that code for storage proteins, etc., have been well documented. The development of DNA-based markers for desirable qualities is now possible because to the development of molecular biology. Therefore, DNA markers complement traditional breeding techniques, allowing for the quicker development of novel cultivars with desirable traits. Due to the low volume of durum wheat grain, Ethiopian pasta businesses still augment bread wheat flour with colorants and pasta zymes and are negatively impacted by the high import costs. Local farmers are increasing their durum wheat production and supplying high-quality durum wheat grain. Maintaining the grain quality of wheat under climate change is essential for human nutrition, end-use functional qualities, as well as commodity value, but the weak supply chain from the producer to the manufacturer is affecting both. Wheat yield can rise by up to 36% under conditions of high CO₂, however grain protein concentrations often decline and a change in composition results in fewer useful qualities. Crops that are post-anthesis can have a step-change drop in grain-set, grain size, and milling yield due to high temperatures. Wheat dough has lower viscoelasticity qualities because high temperature stress affects the glutenin/gliadin ratio and restricts the synthesis of the bigger sodium dodecyl sulfate (SDS)-insoluble glutenin polymers. The current understanding of the effects of high temperatures and elevated atmospheric CO₂on the whole-grain and functional properties of wheat, as well as the recent development of molecular markers and their use in breeding programs, particularly to improve traits relating to wheat grain, are reviewed in this paper. Finally, a few aspects of the Ethiopian pasta industry are discussed.

Legacy Effect of Long-Term Elevated CO2 and Warming on Soil Properties Controls Soil Organic Matter Decomposition

Plant litter quality is one of the key factors that control soil organic matter (SOM) decomposition. Under climate change, although significant change in litter quality has been intensively reported, the effect of litter quality change on SOM decomposition is poorly understood. This limits our ability to model the dynamics of soil carbon under climate change. To determine the effect of litter quality and soil property change on SOM decomposition, we performed a controlled, reciprocal transplant and litter decomposition experiments. The soils and plant litters were collected from a long-term field experiment, where four treatments were designed, including: (1) the control without warming at ambient CO2; (2) elevated atmospheric CO2 up to 500 ppm (C); (3) warming plant canopy by 2 °C (T); (4) elevated CO2 plus warming (CT). We found that elevated CO2 and warming altered the litter quality significantly in terms of macronutrients’ content and their stoichiometry. Elevated CO2 decreased the concentration of N in rice and wheat straw, while warming decreased the concentration of N and K in wheat straw. However, the change in plant litter quality did not lead to a shift in SOM decomposition. On the contrary, the legacy effect of long-term elevated CO2 and warming on soil properties dominated the decomposition rate of SOM. Elevated atmospheric CO2 suppressed SOM decomposition mainly by increasing phosphorous availability and lowering the soil C/N, fungi/bacteria ratio, and N-acetyl-glucosaminidase activity, while warming or elevated CO2 plus warming had no effect on SOM decomposition. Our results demonstrated that the changes in soil property other than litter quality control the decomposition of SOM under climate change, and soil property change in respond to climate change should be considered in model developing to predict terrestrial soil carbon dynamics under elevated atmospheric CO2 and warming.

Nitrogen availability mediates soil carbon cycling response to climate warming: A meta-analysis.

Global climate warming may induce a positive feedback through increasing soil carbon (C) release to the atmosphere. Although warming can affect both C input to and output from soil, direct and convincing evidence illustrating that warming induces a net change in soil C is still lacking. We synthesized the results from field warming experimentsat165sites across the globe and found that climate warming had no significant effect on soil C stock. On average, warming significantly increased root biomass and soil respiration, but warming effects on root biomass and soil respiration strongly depended on soil nitrogen (N) availability. Under high N availability (soil C:N ratio < 15), warming had no significant effect on root biomass, but promoted the coupling between effect sizes of root biomass and soil C stock. Under relative N limitation (soil C:N ratio > 15), warming significantly enhanced root biomass. However, the enhancement of root biomass did not induce a corresponding C accumulation in soil, possibly because warming promoted microbial CO2 release that offset the increased root C input. Also, reactive N input alleviated warming-induced C loss from soil, but elevated atmospheric CO2 or precipitation increase/reduction did not. Together, our findings indicate that the relative availability of soil C to N (i.e., soil C:N ratio) critically mediates warming effects on soil C dynamics, suggesting that its incorporation into C-climate models may improve the prediction of soil C cycling under future global warming scenarios.

Elevated atmospheric CO2 concentrations caused a shift of the metabolically active microbiome in vineyard soil

BackgroundElevated carbon dioxide concentrations (eCO2), one of the main causes of climate change, have several consequences for both vine and cover crops in vineyards and potentially also for the soil microbiome. Hence soil samples were taken from a vineyard free-air CO2 enrichment (VineyardFACE) study in Geisenheim and examined for possible changes in the soil active bacterial composition (cDNA of 16S rRNA) using a metabarcoding approach. Soil samples were taken from the areas between the rows of vines with and without cover cropping from plots exposed to either eCO2 or ambient CO2 (aCO2).ResultsDiversity indices and redundancy analysis (RDA) demonstrated that eCO2 changed the active soil bacterial diversity in grapevine soil with cover crops (p-value 0.007). In contrast, the bacterial composition in bare soil was unaffected. In addition, the microbial soil respiration (p-values 0.04—0.003) and the ammonium concentration (p-value 0.003) were significantly different in the samples where cover crops were present and exposed to eCO2. Moreover, under eCO2 conditions, qPCR results showed a significant decrease in 16S rRNA copy numbers and transcripts for enzymes involved in N2 fixation and NO2− reduction were observed using qPCR. Co-occurrence analysis revealed a shift in the number, strength, and patterns of microbial interactions under eCO2 conditions, mainly represented by a reduction in the number of interacting ASVs and the number of interactions.ConclusionsThe results of this study demonstrate that eCO2 concentrations changed the active soil bacterial composition, which could have future influence on both soil properties and wine quality.

Growth Response of Wheat and Maize to Different Nitrogen Supply Forms under the Enrichment of Atmospheric CO2 Concentrations

Elevated atmospheric CO2 concentrations (eCO2) has become the main feature and cause of global change that could affect crop growth in many aspects, including physiological processes and morphological development in plants and nutrient cycling and nutrient uptake from the soil. Studying the responses of crop growth to different nitrogen (N) supply forms under elevated atmospheric CO2 concentrations can guide nutrient management strategies for agricultural production under future climate change scenarios. Few studies addressed the effect of eCO2 on N uptake and morphological development for plants. This study was conducted in the CO2-controlled light incubators based on the sand-pot incubation using wheat and maize as experimental plants. Six treatments were set with two different environmental CO2 concentrations (aCO2, 390 µmol mol−1; eCO2, 690 µmol mol−1) and three different N supply forms, including ammonium−N, nitrate−N and ammonium-nitrate with 1:1 ratio. The following results were obtained: (i) Wheat and maize seedlings, as nitrate-preferring crops, grew better under mixed N forms than under single N forms. For the single N supply treatment, seedlings with nitrate−N supply showed better growth than with ammonium. (ii) For wheat plants, seedlings with a single ammonium−N supply showed slender height and fewer tillers; seedlings with a single nitrate−N supply were characterized by slightly shorter plant height, more tillers, and higher aboveground biomass. (iii) Compared to the aCO2 group, wheat seedlings with the ammonium−N supply showed an increased maximum root length and a decreased carbon concentration in root exudates; wheat seedlings with a single nitrate−N supply under eCO2 showed a significant increase in biomass and a decreased carbon concentration in root exudates; wheat seedlings with a mixed N supply under eCO2 explored a significant increase in carbon concentration in root exudate and a relatively lower N concentration. (iv) For maize plants, seedlings with either single ammonium−N or nitrate−N supply did not show significant differences in most growing indices. Maize seedlings with a mixed N supply exhibited an increase in aboveground biomass and N concentration in root exudates compared to those with a single N supply. (v) Compared with the aCO2 group, maize seedlings with mixed N supply under eCO2 conditions exhibited significant increases in plant height, aboveground biomass, and N concentration in root exudates. Single ammonium−N supply was toxic to wheat and maize plants under eCO2 conditions. We recommend raising the ratio of ammonium-to-nitrate under mixed N supply to improve the coordination of carbon and N metabolism for efficient crop growth under climatic change conditions of elevated atmospheric CO2 concentration.

Competition between biogeochemical drivers and land-cover changes determines urban greening or browning

Urban vegetation, a harbinger of future global vegetation change, is controlled by complex urban environments. The urban-rural gradient in vegetation greenness trends and their responses to biogeochemical drivers (e.g. elevated atmospheric CO2 concentration and climate warming) and land-cover changes, however, remain unclear. Here we used satellite-derived enhanced vegetation index to examine the greenness trends for 1500-plus cities in China for 2000–2019. We developed a conceptual framework to differentiate between the contributions of four key drivers to the greenness trends: two biogeochemical drivers, a background biogeochemical driver (BBD) and an urban biogeochemical driver (UBD), and two drivers of land-cover changes, urban expansion or densification (UED) and urban green recovery (UGR). We find that the greening trends gradually decreased from urban cores to urban new towns and then to browning trends in urban fringes. The significant greening in urban cores was mainly contributed by BBD (25.6%) and UBD (52.3%). While the minor greening in urban new towns was contributed by both BBD (33.1%) and UBD (24.1%) and weakened by UED (−39.7%). The UED (−64.4%) dominated the browning in urban fringes. These results suggest that biogeochemical drivers and land-cover changes jointly regulated the urban-rural gradient in greenness trends, which contributes to the assessment of future global vegetation change driven by complex environmental changes.

Altered volatile emission of pear trees under elevated atmospheric CO2 levels has no relevance to pear psyllid host choice

The impact of climate change drivers on cultivated plants and pest insects has come into research focus. One of the most significant drivers is atmospheric carbon dioxide, which is converted into primary plant metabolites by photosynthesis. Increased atmospheric CO2 concentrations therefore affect plant chemistry. The chemical composition of non-volatile and volatile organic compounds of plants is used by insects to locate and identify suitable host plants for feeding and reproduction. We investigated whether elevated CO2 concentrations in the atmosphere affect the plant-pest interaction in a fruit crop of high economic importance in Europe. Therefore, potted pear trees were cultivated under specified CO2 conditions in a Free-Air Carbon dioxide Enrichment (FACE) facility at Geisenheim University in Germany for up to 14 weeks, beginning from bud swelling. We compared emitted volatiles from these pear trees cultivated for 7 and 14 weeks under two different CO2 levels (ambient: ca. 400 ppm and elevated: ca. 450 ppm CO2) and their impact on pest insect behavior. In total, we detected and analyzed 76 VOCs from pear trees. While we did not detect an overall change in VOC compositions, the relative release of single compounds changed in response to CO2 increase. Differences in VOC release were inconsistent over time (phenology stages) and between study years, indicating interactions with other climate parameters, such as temperature. Even though insect-plant interaction can rely on specific volatile compounds and specific mixtures of compounds, respectively, the changes of VOC patterns in our field study did not impact the host choice behavior of C. pyri females. In olfactometer trials, 64% and 60% of the females preferred the odor of pear trees cultivated under elevated CO2 for 7 and 14 weeks, respectively, over the odor from pear trees cultivated under ambient CO2. In binary-choice oviposition assays, C. pyri females laid most eggs on pears during April 2020; on average, 51.9 (± 51.3) eggs were laid on pears cultivated under eCO2 and 60.3 (± 48.7) eggs on aCO2.

Photosynthetic Gains in Super-Nodulating Mutants of Medicago truncatula under Elevated Atmospheric CO2 Conditions.

Legumes are generally considered to be more responsive to elevated CO2 (eCO2) conditions due to the benefits provided by symbiotic nitrogen fixation. In response to high carbohydrate demand from nodules, legumes display autoregulation of nodulation (AON) to restrict nodules to the minimum number necessary to sustain nitrogen supply under current photosynthetic levels. AON mutants super-nodulate and typically grow smaller than wild-type plants under ambient CO2. Here, we show that AON super-nodulating mutants have substantially higher biomass under eCO2 conditions, which is sustained through increased photosynthetic investment. We examined photosynthetic and physiological traits across super-nodulating rdn1-1 (Root Determined Nodulation) and sunn4 (Super Numeric Nodules) and non-nodulating nfp1 (Nod Factor Perception) Medicago truncatula mutants. Under eCO2 conditions, super-nodulating plants exhibited increased rates of carboxylation (Vcmax) and electron transport (J) relative to wild-type and non-nodulating counterparts. The substantially higher rate of CO2 assimilation in eCO2-grown sunn4 super-nodulating plants was sustained through increased production of key photosynthetic enzymes, including Rieske FeS. We hypothesize that AON mutants are carbon-limited and can perform better at eCO2 through improved photosynthesis. Nodulating legumes, especially those with higher nitrogen fixation capability, are likely to out-perform non-nodulating plants under future CO2 conditions and will be important tools for understanding carbon and nitrogen partitioning under eCO2 conditions and future crop improvements.

High-resolution dynamics of available N in a grassland ecosystem under a multiple climate manipulation experiment

Nitrogen (N) is the most important limiting nutrient for plants and soil microorganisms in almost all ecosystems. Global environmental changes significantly affect the terrestrial N cycle but implications for plant available N in-situ remain unclear. Here, we investigated the simultaneous effect of elevated atmospheric CO2, an increase in temperature and a drying-rewetting event on diffusive N fluxes in soil of a managed permanent grassland at the multifactor climate manipulation experimental site ClimGrass (Austria) using microdialysis. Rewetting caused a significant, but short-lived increase in diffusive NH4+ and NO3− fluxes, which subsequently dropped until the end of the experiment. Harvesting induced a significant increase in diffusive NH4+ fluxes in the drying-rewetting treatments. However, elevated CO2 and soil warming had little effect on diffusive N fluxes. Our study suggests that more frequent soil drying-rewetting cycles associated with increased extreme weather events are uppermost among the climate change drivers affecting soil N availability.

Elevated CO2 increases soil redox potential by promoting root radial oxygen loss in paddy field

Soil redox potential (Eh) plays an important role in the biogeochemical cycling of soil nutrients. Whereas its effect soil process and nutrients’ availability under elevated atmospheric CO2 concentration and warming has seldom been investigated. Thus, in this study, a field experiment was used to elucidate the effect of elevated CO2 concentration and warming on soil Eh, redox-sensitive elements and root radial oxygen loss (ROL). We hypothesized elevated CO2 and warming could alter soil Eh by promoting or inhibiting ROL. We found that soil Eh in the rhizosphere was significantly higher than that of non-rhizosphere. Elevated CO2 enhanced soil Eh by 11.5%, which corresponded to a significant decrease in soil Fe2+ and Mn2+concentration. Under elevated CO2, the concentration of Fe2+ and Mn2+ decreased by 14.7% and 13.7%, respectively. We also found that elevated CO2 altered rice root aerenchyma structure and promoted rice root ROL. Under elevated CO2, rice root ROL increased by 79.5% and 112.2% for Yangdao 6 and Changyou 5, respectively. Warming had no effect on soil Eh and rice root ROL. While warming increased the concentration of Mn2+ and SO42− by 4.9% and 19.3%, respectively. There was a significant interaction between elevated CO2 and warming on Fe2+ and Mn2+. Under elevated CO2, warming had no effect on the concentration of Fe2+ but decreased Mn2+ concentration significantly. Our study demonstrated that elevated atmospheric CO2 in the future could increase soil Eh by promoting rice root ROL, which will alter some soil nutrients’ availability, such as Fe2+ and Mn2+.

Visualized analysis of amino acids and organic acids in wheat caryopsis in response to multigenerational effects of elevated atmospheric CO2 concentration

The response of wheat to elevated atmospheric CO2 concentration (e[CO2]) within a single generation is being cumulatively studied, but multigenerational effects of e[CO2] on wheat is largely unknown. In this study, the emerging spatially resolved metabolomics was used to visualize the spatial distributions of amino acids and organic acids in wheat caryopsis exposed to multigenerational e[CO2]. These results showed that nine kinds of amino acids and three kinds of organic acids exhibited embryo-distribution pattern in wheat caryopsis under sequential atmospheric CO2 concentration (a[CO2]). Additionally, e[CO2] can induce nonuniformly spatial distribution of amino acids and organic acids. Further inspection of the differential accumulation of amino acids in embryo/endosperm under multigenerational e[CO2] exposure indicated that the abundance of valine, glutamine, glutamic acid and histidine in embryo was decreased by multigenerational e[CO2] exposure, whereas abundance of lysine, aspartic acid and glutamic acid in endosperm showed different trends. Multigenerational e[CO2] exposure decreased the abundance of ascorbic acid and cis-aconitic acid, regardless of regions, while increased the abundance of malic acid in endosperm. It was suggested that the long-term e[CO2] cause inconsistent changes in embryo and endosperm, which may lead to potential impacts on human dietary health and crop offspring vigor.

Meeting the heavy-metal safety requirements for food crops by using biochar: An investigation using sunflower as a representative plant under different atmospheric CO2 concentrations

Global warming impacts on plant growth and food safety are emerging topics of concern, while biochar as a soil additive benefits plants. This study investigates (1) sunflower plant growth at various biochar concentrations in a soil-compost growing substrate under both ambient (420 ppm) and elevated (740 ppm) atmospheric CO2 concentrations, and (2) concentrations of heavy metals in the growing substrates and organs of the plants. The elevated CO2 concentration benefits the vegetative parts but harms the reproductive parts of the plants. Additionally, the elevated CO2 concentration inhibits the beneficial effects that biochar confers on the plants at the ambient concentration. The optimum biochar concentration at both CO2 levels was found to be 15%. At the time of harvest, most of the heavy-metal concentrations in the growing substrate increased. It was demonstrated that biochar can reduce the amount of heavy metals that accumulate in the roots and seeds whose heavy-metal concentrations complied with Singapore food safety regulations, while those for the biochar met the proposed Singapore biochar standard's thresholds. Our results show that the proposed Singapore biochar standard is practical and sound.

Changes in Mangrove Blue Carbon under Elevated Atmospheric CO 2

While there is consensus that blue carbon ecosystems, such as mangroves, have an important role in mitigating some aspects of global climate change, little is known about mangrove carbon cycling under elevated atmospheric CO 2 concentrations ( e CO 2 ). Here, we review studies in order to identify pathways for how e CO 2 might influence mangrove ecosystem carbon cycling. In general, e CO 2 alters plant productivity, species community composition, carbon fluxes, and carbon deposition in ways that enhance mangrove carbon storage with e CO 2 . As a result, a negative feedback to climate change exists whereby e CO 2 adds to mangrove’s ability to sequester additional carbon, which in turn reduces the rate by which CO 2 builds. Furthermore, e CO 2 affects warming and sea-level rise (SLR) through alternate pathways, which coinfluence the mangrove response in both antagonistic (i.e., warming = greater carbon loss to decomposition) and synergistic (i.e., SLR = greater soil carbon burial) ways. e CO 2 is projected to become a more prominent driver in the future before reaching a steady state. However, given the complexity of the interactions of biological and environmental factors with e CO 2 , long-term field observations and in situ simulation experiments can help to better understand the mechanisms for proper model initialization to predict future changes in mangrove carbon sequestration.

Early Pliocene (Zanclean) stratigraphic framework for PRISM5/PlioMIP3 time slices

Global reconstructions of Pliocene climate provide important insights into how the climate system operates under elevated temperatures and atmospheric CO2 levels. These reconstructions have been used extensively in paleoclimate modeling experiments for comparison to simulated conditions, and as boundary conditions. Most previous work focused on the Late Pliocene interval known as the mid Piacenzian Warm Period (mPWP), the interval originally identified by the U.S. Geological Survey Pliocene Research, Interpretation and Synoptic Mapping Project (PRISM) as the PRISM interval or Mid Pliocene Warm Period. The term Mid Pliocene Warm Period is a misnomer due to changes to the geological time scale, and its use should be discontinued. The Pliocene Model Intercomparison Project (PlioMIP), now in its third phase, is expanding to include a focus on the Early Pliocene (Zanclean). PlioMIP3 experiments will allow comparison of environmental and climatic conditions before and after closure of the Central American Seaway (CAS). PlioMIP3 used the annual insolation pattern at the top of the atmosphere to determine time slices in the Zanclean that have orbital configurations that are most similar to modern. Two have been selected by PlioMIP and adopted by PRISM for inclusion in future studies: PRISM5.1 (4.474 Ma) and PRISM5.2 (4.870 Ma). Here we establish the stratigraphic framework for these Early Pliocene time slices and furnish information to help locate these intervals in proxy records of paleoenvironmental data using oxygen isotope stratigraphy, paleomagnetic stratigraphy, biostratigraphy, and biochronology (calibrated planktic foraminifer and calcareous nannofossil events).

Water use dynamics of dryland wheat grown under elevated CO2 with supplemental nitrogen

Context Elevated atmospheric CO2 (e[CO2]) and nitrogen (N) fertilisation stimulate biomass and yield of crops. However, their interactions depend on crop growth stages and may affect water use dynamics. Aims and methods This study investigated the interactive effects of two N rates, 0 and 100 kg N ha−1, and two CO2 concentrations, ambient (a[CO2], ~400 μmol mol−1) and e[CO2] (~550 μmol mol−1), on biomass, yield and water use of two wheat cultivars, Wyalkatchem (N-use efficient) and Yitpi (local), using a free air CO2 enrichment facility. Key results Elevated [CO2] stimulated leaf area (10%, P = 0.003) and aboveground biomass (11%, P = 0.03). In addition, e[CO2] reduced stomatal conductance (25%, P &lt; 0.001) and increased net assimilation rates (12%, P &lt; 0.001), resulting in greater (40%, P &lt; 0.001) intrinsic water use efficiency. During early growth stages, e[CO2] resulted in higher water use than a[CO2]; however, this difference disappeared later in the season, resulting in similar cumulative water use under both CO2 concentrations. Supplemental N stimulated grain yield of Yitpi by 14% while decreasing that of Wyalkatchem by 7% (N × cultivar, P = 0.063). With supplemental N, Yitpi maintained greater post-anthesis leaf N, chlorophyll content, canopy cover and net assimilation rate than Wyalkatchem. Conclusions During early growth stages, the e[CO2]-induced stimulation of leaf-level water use efficiency was offset by greater biomass, resulting in higher water use. By the end of the season, similar cumulative water use under both CO2 concentrations indicates the dominating effect of the prevailing seasonal conditions in the study area. Observed yield responses of the studied cultivars to supplemental N were associated with their ability to maintain post-anthesis photosynthetic capabilities. Implications Our findings suggest that N-use efficiency traits and responsiveness need to be considered independently to optimise benefits from the ‘CO2 fertilisation effect’ through breeding.