Elevated Atmospheric Temperature Research Articles

Microcystin removal by microbial communities from a coastal lagoon: Influence of abiotic factors, bacterioplankton composition and estimated functions

Toxic cyanobacterial blooms present a substantial risk to public health due to the production of secondary metabolites, notably microcystins (MCs). Microcystin-LR (MC-LR) is the most prevalent and toxic variant in freshwater. MCs resist conventional water treatment methods, persistently impacting water quality. This study focused on an oligohaline shallow lagoon historically affected by MC-producing cyanobacteria, aiming to identify bacteria capable of degrading MC and investigating the influence of environmental factors on this process. While isolated strains did not exhibit MC degradation, microbial assemblages directly sourced from lagoon water removed MC-LR within seven days at 25 ºC and pH 8.0. The associated bacterial community demonstrated an increased abundance of bacterial taxa assigned to Methylophilales, and also Rhodospirillales and Rhodocyclales to a lesser extent. However, elevated atmospheric temperatures (45 ºC) and acidification (pH 5.0 and 3.0) hindered MC-LR removal, indicating that extreme environmental changes could contribute to prolonged MC persistence in the water column. This study highlights the importance of considering environmental conditions in order to develop strategies to mitigate cyanotoxin contamination in aquatic ecosystems.

Interactions between elevated atmospheric CO2 and temperature on rice yield are highly dependent on growth season temperature

The projected increase in atmospheric CO2 concentration (CO2) is expected to enhance rice yield, while the temperature increase lowers it. However, how air temperature increase modifies this effect of CO2 fertilization is still unclear, particularly across different ambient temperatures. To investigate this phenomenon, a temperature-free air CO2 enrichment experiment in paddy field was conducted in 2013 and 2014. An japonica rice (Oryza sativa L.) Wuyunjing 23 was exposed to two levels of CO2 (ambient and elevated by 200 μmol mol−1 during daytime) in combination with two temperature regimes (ambient and elevated by ca. 1 ℃ during daytime). Elevated CO2 significantly increased grain yield in both seasons, but temperature impacts on the magnitude of CO2 responses differed between two seasons: a significant CO2 × temperature interaction was detected in 2013 (mean air temperature 26.6 ℃), with 24 % increase in grain yield under ambient temperature vs 8 % under elevated temperature; while in 2014 (mean air temperature 23.6 ℃), a similar CO2-induced increase under ambient (+12 %) and elevated temperature (+16 %) was detected. Plant height significantly increased upon CO2 elevation in 2014 at various growth stages but not in 2013. The effects of CO2 × temperature interaction on grain yield were primarily attributed to variations in panicle (or tiller) numbers, with negligible effects on other yield components. The aboveground biomass patterns mirrored those of grain yield in the responses to CO2, temperature and their interaction, while less effect of CO2 or temperature treatment was found on harvest index. The results demonstrate that interactions between CO2 and temperature on rice are dependent on growth season temperature: high daytime temperature stress during the early growth period of rice can interfere with tillering formation and lead to less yield gain from CO2 enrichment.

Potential reduction in carbon fixation capacity under climate change in a Pinus koraiensis forest

There has been an increasing recognition of the crucial role of forests, responsible for sequestering atmospheric CO2, as a moral imperative for mitigating the pace of climate change. The complexity of evaluating climate change impacts on forest carbon and water dynamics lies in the diverse acclimations of forests to changing environments. In this study, we assessed two of the most common acclimation traits, namely leaf area index and the maximum rate of carboxylation (Vcmax), to explore the potential acclimation pathways of Pinus koraiensis under climate change. We used a mechanistic and process-based ecohydrological model applied to a P. koraiensis forest in Mt. Taehwa, South Korea. We conducted numerical investigations into the impacts of (i) Shared Socioeconomic Pathways 2–4.5 (SSP2-4.5) and 5–8.5 (SSP5-8.5), (ii) elevated atmospheric CO2 and temperature, and (iii) acclimations of leaf area index and Vcmax on the carbon and water dynamics of P. koraiensis. We found that there was a reduction in net primary productivity (NPP) under the SSP2-4.5 scenario, but not under SSP5-8.5, compared to the baseline, due to an imbalance between increases in atmospheric CO2 and temperature. A decrease in leaf area index and an increase in Vcmax of P. koraiensis were expected if acclimations were made to reduce its leaf temperature. Under such acclimation pathways, it would be expected that the well-known CO2 fertilizer effects on NPP would be attenuated.

Environmental and Health Impacts of Crude Oil Exploration in the Niger Delta

Purpose: This research aims to assess the environmental and health consequences of crude oil exploration in the Niger Delta, focusing on the emission of greenhouse gases and air pollutants and their impacts on public health. Methodology: Literature search was done independently by the authors. After searching for articles on the identified databases, other sources of available and useful data on the subject such as the print press, student’s thesis and dissertation among others were sourced by hand search to augmented resources from the electronic databases.The Literature search was based on the careful evaluation of key words in the title and abstract of identified studies. Findings: The synthesis of available literature revealed significant insights into the environmental and health repercussions of crude oil exploration in the Niger Delta. The impact of gas flaring emerged as a major concern, leading to the release of pollutants like carbon dioxide, methane, and volatile organic compounds. These emissions contribute to elevated atmospheric temperatures, greenhouse gas concentrations, and the formation of acid rain, exacerbating global warming and disease transmission. The exposed population experiences a range of health problems including chronic respiratory diseases, cardiovascular abnormalities, altered blood parameters, and an increased risk of non-communicable diseases such as hypertension and diabetes. Prolonged exposure to pollutants from oil exploration is linked to disrupted sleep patterns, elevated stress levels, and neurophysiological disturbances, further contributing to adverse health outcomes. Unique contribution to theory, practice, and policy: This study advances existing knowledge by providing a comprehensive analysis of the multifaceted interplay between crude oil exploration, environmental degradation, and human health in the Niger Delta region. The research offers a substantial contribution to theoretical understanding by illuminating the intricate relationship between anthropogenic activities, environmental factors, and health outcomes. Moreover, the study provides practical implications by proposing a series of recommendations aimed at mitigating the negative impacts of oil exploration. These recommendations advocate for stricter regulations on emissions, increased monitoring and enforcement, adoption of cleaner technologies, community engagement, and investment in healthcare and environmental remediation. The findings inform policy formulation by supplying evidence-based insights to develop robust regulations and interventions that promote sustainable development, protect public health, and safeguard the environment for future generations.

Response of rice resistance based on the validation of rice blast to elevated CO2 concentration and temperature.

Rice (Oryza sativa) resistance is its ability to resist various stresses, the changes of which have important impacts on O. sativa yield security. However, the responses of O. sativa stress resistance to elevated atmospheric CO2 concentration and temperature are poorly understood. We conducted a field open top-chamber experiment with O. sativa (Nanjing 9108 and Jinxiangyu I) based on the CO2 and temperature automatic control platform. The experimental treatments included ambient CO2 concentration and temperature treatment (CK, control), elevated CO2 concentration treatment (C, CO2 concentration increase of 200 μmol·mol-1 above CK), elevated temperature treatment (T, temperature increase of 2 ℃ above CK) and elevated CO2 concentration and temperature (CT, CO2 concentration increase of 200 μmol·mol-1 and temperature increase of 2 ℃ above CK). At the critical growth stages of O. sativa, we measured superoxide dismutase activity, silica content, total flavanol content, malondialdehyde content, soluble sugar content, proline content, and soluble protein content by cutting the uppermost functional leaves. We obtained the rice stress resistance index (RSRI) by principal component analysis to analyze the differences in the composition of stress resistance indicators under different treatments. Considering the disease resistance of O. sativa, the spike neck blast disease was counted to verify the expression level of RSRI for O. sativa stress resistance at maturity stage. Results showed that at the elongation-booting stage, C and CT treatments significantly reduced the RSRI of Jinxiangyu I by 36.5% and 41.1%, respectively, compared with CK. T treatment significantly decreased the RSRI of the two varieties by 44.9% and 33.8%, respectively. The RSRI explained 71.9%-74.3% of the variation in the spike neck blast disease. Overall, the stress resistance of two O. sativa varieties were adversely affected by elevated temperature at the elongation-booting stage. There was an interactive effect of CO2 concentration and temperature on O. sativa stress resistance. Compared with Nanjing 9108, the stress resistance of Jinxiangyu I was more sensitive to elevated CO2 concentration.

Irrigated Agriculture as an Adaptation Strategy Against Climate Change: A Review

Agriculture evolved to increase crop productivity and diminish plague effects. As a negative outcome of the human footprint by agriculture and industrialization, overall economic practices have led to substantial alterations in the environment (i.e., greenhouse gas production, elevated atmospheric temperature, more extreme climatic events), collectively known as climate change. The fast-changing environment due to climate change is most common in the tropics, the impacts of this phenomenon are perceived in different regions of the world, where most agricultural activity occurs. These facts reinforce the requirement for diminishing climate change producing activities and implementation of adaptive practices for long-term agricultural productivity and sustainability. Albeit may sound counter-intuitive, agroecological systems and traditional knowledge may provide alternatives to mitigate climate change effects in the context of agriculture. This review comprehensively describes the development of irrigated agriculture, major effects of climate change on irrigation, and further explores alternative practices stemming from agroecological systems or traditional knowledge, which could improve agricultural productivity and sustainability. Among some strategies, it is proposed to establish climate risk planning, agricultural producers must modify the application of their inputs to adjust to the new water and thermal requirements; implement conservation techniques to reduce the loss of soil moisture and thus ensure the development of crops in a drier and warmer environment as indicated by climate change projections. Likewise, the implementation of varieties tolerant to water stress is one more adaptation action that would allow continuing cultivating in lower regions, where the largest irrigated area is concentrated and which would receive the greatest impact from an increase in temperature. In this way, it will be necessary to implement new approaches, technologies and policies to learn from the past, following the new climate scenarios, conserving and making rational use of natural resources.

Effect of elevated atmospheric CO2 concentration and temperature on volatile halogenated organic compound content in soils of Schima superba and Cunninghamia lanceolata seedlings.

Global changes caused by the increases of atmospheric CO2 concentration and temperature have important effects on soil biogeochemical processes. The synthesis and release of volatile halogenated organic compounds (VOXs) is an important pathway for soil to participate in the global material cycle and energy flow. In this study, Schima superba and Cunninghamia lanceolata seedlings in the southern subtropics were selected as the research objects. Four treatments, including control (CK), elevated CO2 concentration (EC), elevated temperature (ET) and elevated both factors (EC+ET) were set up. The effects of EC and ET on soil VOXs formation were studied by an open-top chamber system coupled with a purging and trapping gas chromatography/mass spectrometry. The results showed that VOXs content in the soil of S. superba seedlings was 0.065-0.252 ng·g-1, which was higher than that of C. lanceolata (0.038-0.136 ng·g-1). At the EC, ET and EC+ET treatments, VOXs contents were reduced in soils of both species. The effect of ET was the most significant, with the decrease rates of 74.2% and 72.1% in both soils, respectively. The change of VOXs content with increasing temperature mainly attributed to the changes of soil moisture and nitrogen content. The content of VOXs in the soils of S. superba seedlings decreased more than that of C. lanceolata under different treatments. In CK, EC, ET and EC+ET treatment, bromodichloromethane (BDCM) (27.5%, 36.7%, 32.9%, 32.6%) and tetrachloromethane (TCM) (9.0%, 16.8%, 22.7%, 15.8%) were the main VOXs in the soil of S. superba seedlings, respectively, while BDCM and dibromomethane (DBM) were the main VOXs in the soil of C. lanceolata seedlings. BDCM accounted for 31.9%, 38.2%, 40.9% and 37.2% of the VOXs content in each treatment, and DBM accounted for 17.9%, 16.5%, 19.2% and 16.0% of the VOXs content, respectively. Simulating elevated atmospheric CO2 concentration and temperature was conducive to more comprehensive reflection of the ecological effect of global climate change, and it could provide data support for improving the VOCs flux model.

Nitrogen addition exerts a stronger effect than elevated temperature on soil available nitrogen and relation to soil microbial properties in the rhizosphere of Camellia sinensis L. seedlings.

As the global climate changes, elevated atmospheric temperature and nitrogen (N) deposition co-occur in natural ecosystems, which affects rhizosphere soil nutrient by altering allocation of roots and its availability to soil microorganism. Elevated temperature in combination with N deposition is expected to affect soil available N and its relation to microbial properties, but this issue has not been extensively examined. Here, we investigated soil available N and its relation to microbial properties in rhizosphere of Camellia sinensis L. seedlings exposed to elevated temperature using a passive warming device in combination with N-added soil. Elevated temperature did not significantly affect soil pH, total organic carbon (TOC), total nitrogen (TN), the ratio of carbon and nitrogen (C:N ratio), total phosphorus (TP), available N ((N in ammonium (NH4+-N) and N in nitrate (NO3--N)) (NH4+-N + NO3--N)/TN, α-glucosidase (αG), β-glucosidase (βG), cellobiohydrolase (CBH), N-acetyl-glucosaminidase (NAG), and phenol oxidase (PPO) activities, while significantly stimulated root total length of tea seedlings (3.9%), root dry biomass (10.2%), soil microbial biomass carbon (MBC) (7.4%), microbial biomass nitrogen (MBN) (8.6%), and acid phosphatase (ACP) (8.8%). While N addition significantly (p < 0.05) stimulated root dry biomass of tea seedlings (14.1%), root total length (6.2%), root average diameter (6.7%), soil TN, available N, (NH4+-N + NO3--N)/TN, and MBN under elevated temperature. Soil aG, βG, CBH, and ACP activity increase significantly (p < 0.05) under elevated temperature + N relative to elevated temperature alone. Generally, N addition led to increased available nitrogen and microbial properties in rhizosphere soil of tea seedlings exposed to elevated temperature by stimulating root properties, soil nitrogen, microbial biomass N, and enzyme activity. Redundancy analysis and Pearson correlation analysis suggested that N addition lead to higher correlation between soil available N and microbial properties exposed to elevated temperature. Our results indicated nitrogen addition exerts a stronger effect than elevated temperature on soil fertility and microbiological cycle in the rhizosphere of Camellia sinensis L. seedlings. The conclusion helps us understand the response mechanism of soil rhizosphere microenvironment to N deposition under global warming scenarios.

XFEM simulation of dislocation in SixGe1-x alloy under thermal loads

SixGe1-x is an alloy made of two semiconductor materials from group Ⅳ-A of the periodic table. The performance of semiconductors results in higher temperatures due to electric field formation and also they are exposed to elevated atmospheric temperatures. Here, the SixGe1-x domain with one free surface at the left is considered under thermal loads at different compositions when the edge dislocation is present in the domain. The Extended Finite Element Method (XFEM) is used for numerical modeling of the problem. The lattice constant, thermal conductivity, electrical conductivity and thermal expansion coefficient are functions of the amount of Si (xSi) in the alloy. The dislocation Burgers vector is also dependent on the Si concentration as its magnitude is defined in terms of the lattice constant. The XFEM formulation introduces the Volterra type edge dislocation through the enrichment functions. Firstly, the discrete heat equilibrium equation is solved and then considering the thermal strains, the discrete force equilibrium equation is solved. The two cases of the heat flux acting normal to the glide plane and along the glide plane of the dislocation are considered for different temperatures. The results indicate an increase in the Peach-Koehler force with the increase in ‘xSi’ greater than 0.2 for both the cases of the heat flux application at all temperatures. However, at the lower concentration of Si i.e. below 0.2, the Peach-Koehler force is affected differently.

Climate change regulated abiotic stress mechanisms in plants: a comprehensive review.

Global climate change is identified as a major threat to survival of natural ecosystems. Climate change is a dynamic, multifaceted system of alterations in environmental conditions that affect abiotic and biotic components of the world. It results in alteration in environmental conditions such as heat waves, intensity of rainfall, CO2 concentration and temperature that lead to rise in new pests, weeds and pathogens. Climate change is one of the major constraints limiting plant growth and development worldwide. It impairs growth, disturbs photosynthesis, and reduces physiological responses in plants. The variations in global climate have gained the attention of researchers worldwide, as these changes negatively affect the agriculture by reducing crop productivity and food security.With this background, this review focuses on the effects of elevated atmospheric CO2 concentration, temperature, drought and salinity on the morphology, physiology and biochemistry of plants. Furthermore, this paper outlines an overview on the reactive oxygen species (ROS) production and their impact on the biochemical and molecular status of plants with increased climatic variations. Also additionally, different tolerance strategies adopted by plants to combat environmental adversities have been discussed.

A meta-analysis of the possible impact of climate change on global cotton yield based on crop simulation approaches

CONTEXT:Cotton is one of the most widely planted fiber crops in the world. Its growth, development, and yield are influenced by elevated atmospheric CO2 concentrations, temperature increases, and seasonal rainfall patterns. However, due to differences in research methods (such as crop models, climate models, and climate scenarios), there are uncertainties in the magnitude and direction of the impact of future climate change on cotton yields in existing studies. OBJECTIVETo comprehensively assess the potential impact of climate change and adaptation on yieldand analyze the associated uncertainties, 27 published studies (including 1353 samples) were used to establish a meta database of changes in future cotton yield. METHODSThe responses of cotton relative yield change to changes in mean temperature, minimum temperature, maximum temperature, precipitation, and CO2 concentration were studied using local polynomial (Loess) regression in a full dataset. A linear mixed-effect model was then used to explore the quantitative relationship between them in a restricted dataset. RESULTS AND CONCLUSIONSUsing the established full dataset, we found that when the average temperature exceeded 4.3 °C, or the average precipitation decreased or increased too much (>200%), the simulated cotton yield decreased. Elevated CO2 concentrations and appropriate management measures could alleviate the negative impact of climate change. By establishing a linear mixed-effect model, we found that temperature, precipitation, CO2 concentration changes, adaptive measures, study area, climate models, and climate scenarios had significant impacts on cotton yield change. For every 1 °C increase in average temperature, the cotton yield decreased by 1.64%. For every 1% increase in precipitation and 1 ppm increase in CO2 concentration, cotton yield increased by 0.09% and 0.05%, respectively. Cotton yield under adaptation measures was 8.97% higher than without any adaptation. SIGNIFICANCEThe first systematic meta-analysis of the impact of climate change on cotton yield in major cotton-planting regionswas conducted herein. The findings provide new information for policies related to the impact of climate change and enhance our understanding of the future resilience of the cotton system.

Interactive Influences of Elevated Atmospheric CO2 and Temperature on Phosphorus Acquisition of Crops and its Availability in Soil: A Review

Interactive Influences of Elevated Atmospheric CO2 and Temperature on Phosphorus Acquisition of Crops and its Availability in Soil: A Review

Voltine Ecotypes of the Asian Corn Borer and Their Response to Climate Warming.

Simple SummaryThe Asian corn borer (ACB), Ostrinia furnacalis, is an important economic pest of corn and other crops, and is widely distributed in China. Depending on the climate, ACB may have one or up to seven generations each year, from north to south, respectively. The degree of crop damage is closely related to its phenology and number of generations per year (voltinism). Climate warming may result in an alternation of voltinism in the ACB. In the present study, we investigated the voltinism of different populations under different simulated environments. From the diapause response, both the uni- and multivoltine ecotypes were coexisting in the Harbin (H) population collected from action sites of ACB moths in Harbin, Heilongjiang Province, China. Diapause incidence declined given the climate-warming scenario, which was temporally specific and could be overridden by significantly low daily average temperatures. Elevated CO2 did not directly impact voltinism. On the basis of voltinism, the H population reflected sympatric uni- and multivoltine ecotypes, with multivoltinism being dominant. The univoltinism trait was recessive. Climate warming could significantly override photoperiod effects. Warmer temperatures and declining latitude (reduced daylength), and their interaction, are estimated to drive ACB evolution to increased homogeneity and multivoltinism.In the Asian corn borer (ACB), Ostrinia furnacalis (Guenée), diapause is governed by a multigenetic constitution that responds to daylength and temperature with seasonality. The ACB displays uni- or multivoltinism, depending on its geographic specificity. Hence, warmer temperatures may result in alternation of voltinism in the ACB, which will help in understanding the ecological consequences of climate warming on insects. In the present study, we investigated the voltinism in two natural populations from Harbin (H) and Gongzhuling (G) as well as a laboratory (L) population (established from the H population in 2017) of the ACB, at ambient and elevated atmospheric CO2 (aCO2 390 μL/L and eCO2 750 μL/L) and temperature (aT and Et = At + 2 °C). From the diapause response, both the uni- and multivoltine ecotypes were coexisting in the H population. The neonate occurrence date of 50% individuals that induced diapause was ca. 10 days later in the G population than in the H population, but it was about 10 days earlier than in the L population. Comparing to the dates of onset and the peak of diapause induction, the G and L populations were less variable than the H population in response to a short and/or shortening daylength in the field. The univoltine individuals could not be eliminated completely after 19 generations of selection. Diapause incidence decreased with a climate-warming scenario, which was temporally specific and could be overridden by significantly low daily average temperatures. The eCO2 did not directly impact the voltinism. On the basis of voltinism, the H population was sympatric for uni- and multivoltine ecotypes, with multivoltinism being dominant. The univoltinism trait was recessive. Climate warming could significantly override the effect of photoperiod, which was yearly dependent. Warmer temperatures and a decreased latitude (shortened daylength), and their interaction, would drive ACB evolution toward diapause homogeneity for multivoltinism.

Food safety in the face of climate change

Food safety encompasses the elimination of biological, chemical, and physical hazards along the food chain; however, climate change, an abnormal change in weather conditions, is a threat to food safety due to irregularities in the elements of weather essential for food production. Such factors include elevated atmospheric carbon (IV) oxide (CO2), precipitation, rainfall, and temperature. Considering that the aim of food safety is to eliminate food hazards along the food chain, it is threatened by climate change in several ways, resulting in adverse effects such as severe consequences for livestock production, harmful algal bloom, mycotoxins (produced by mycotoxigenic fungi on crops), residues of pesticides and tenacious contaminants, and pathogenic microorganisms from contaminated water. These climate changes include landslides and avalanches, drought and extreme heat waves, drought, heavy precipitation, flooding and tropical storms, ocean warming, climate change related acidification, and changes in ocean salinity. Therefore, there is a great need to employ adaptive strategies such as the establishment of a food safety management programme which would expound on the need to detect food hazards in food as a result of climate change. This programme should include setting up awareness for consumers, the improvement of epidemiological surveillance, improved co-ordination among food safety organizations, public health officials, and veterinary officials, amongst others. Thus, to achieve the sustainable development goal two, of eradicating hunger, it is imperative to harness the strategies for reducing the food safety hazards associated with climate change.

How do elevated atmosphere CO2 and temperature alter the physiochemical properties of starch granules and rice taste?

Elevated atmospheric CO2 (EC) and temperature (ET) strongly affect agricultural production, but the mechanism through which EC and/or ET influence starch granules and their relationship to cooked rice taste remain largely unknown. Therefore, a field experiment using a popular japonica cultivar grown in a temperature/free-air CO2 enrichment environment was conducted to investigate the responses of volume and fine structure of starch granules and their formation physiology to EC (+200 ppm) and/or ET (+1 °C) in 2015–2016. EC markedly enhanced the activity of soluble-starch synthase and granule-bound starch synthase by 28.0% and 27.9% respectively, thereby increasing the long chains and the volume of starch granules. However, EC decreased the activity of starch-branch enzyme by 7.5% possibly via the pathway of ethylene signalling (EC prominently decreased the ethylene evolution rate of rice grains by 28.8%), resulting in a remarkable decrease in α-1′6 glucosidic bonds and significant increase in the iodine-binding capacity and double helix in starch molecules. These EC-induced changes in morphology and fine structure of starch granules synergistically altered the thermal properties of rice flour and eventually improved the cohesiveness and taste of cooked rice, as suggested by the significant relationships between them. ET partially offset the beneficial EC effects in most cases. However, few remarkable CO2 × temperature or CO2 × year effects were detected, indicating that the effects of EC on starch granules and rice taste less varied with meteorological conditions. These findings have important implications on rice palatability and for the development of adaptive strategies in the starch industry in future environment.

Effects of elevated temperature and drought stress on fruit coloration in the jujube variety ‘Lingwuchangzao’ (Ziziphus jujube cv. Lingwuchangzao)

Fruit color of jujube is an important horticultural trait contributing to nutritional components, market value and consumer preference. The objective of this investigation was to gain insight into the influences of elevated atmospheric temperature and drought stress on the coloration of jujube fruits. The fruit skin color, as well as the content of anthocyanins, carotenoids and chlorophyll under different atmospheric temperature and drought stress treatments were analyzed for a traditional jujube cultivar ‘Linwuchangzao’. The elevated temperature (1.5–2.5 ℃) significantly increased the fruit redness and the content of anthocyanins and carotenoids by 21.02 %, 13.20 % and 30.90 %, respectively, in three different stages of fruit ripening. The drought stress, with soil moisture at 30 %–50 % of the field capacity, significantly decreased the fruit redness and the content of anthocyanins and carotenoids but increased the content of chlorophyll under the same temperature. Significant temperature x drought interactions were observed for fruit color and pigments, showing that the positive effect from the elevated temperature was reduced as the drought stress intensified. The present results suggest that under the scenario of a 2 ℃ increase in atmospheric temperature, fruit coloration of jujube cultivar ‘Lingwuchangzao’ can be enhanced. However, drought stress negatively affected fruit coloration and reduced the positive effects resulting from the elevated temperature. This study, therefore, provides novel information for understanding environmental effects on fruit quality attributes of jujube. This knowledge will be useful for developing appropriate crop management practices for jujube production in the arid and semiarid regions in northwest China.

Air warming and CO2 enrichment cause more ammonia volatilization from rice paddies: An OTC field study

Ammonia (NH3) volatilization in rice paddies may be affected by elevated atmospheric CO2 concentration ([CO2]) and temperature due to changes in plant and soil nitrogen (N) metabolism. At present, little is known about the individual and combined effects of CO2 enrichment and warming on NH3 volatilization under field conditions. An experiment was conducted in a rice paddy in Central China, after 4 years of warming and CO2 enrichment using open-top chamber (OTC) devices. Compared with ambient conditions, elevated [CO2] had no significant effects on NH3 volatilization, although increases in soil pH and urease activity were observed. The stimulation on plant N assimilation under CO2 enrichment might offset the possible enhancement on NH3 volatilization, as more soil N was absorbed by plant thus reducing NH3 loss potential. Elevated temperature increased NH3 volatilization significantly, which could be attributed to increased soil ammonium nitrogen (NH4+-N) concentration, pH, and urease activity. Combination of CO2 enrichment and warming caused the highest cumulative NH3 loss, which increased by 26.5% compared with ambient conditions, but the interaction was not significant. Higher plant N uptake, soil NH4+-N concentration, pH and urease activity were also observed with co-elevation of [CO2] and temperature, but the combined effects were variable and not synergistic. Our findings confirm that field warming and CO2 enrichment cause more NH3 volatilization in rice paddies, among which warming effects are dominant, and suggest that improved N management or field practices are required to reduce NH3 losses under future climate change.

Composition and activity of nitrifier communities in soil are unresponsive to elevated temperature and CO2, but strongly affected by drought

Nitrification is a fundamental process in terrestrial nitrogen cycling. However, detailed information on how climate change affects the structure of nitrifier communities is lacking, specifically from experiments in which multiple climate change factors are manipulated simultaneously. Consequently, our ability to predict how soil nitrogen (N) cycling will change in a future climate is limited. We conducted a field experiment in a managed grassland and simultaneously tested the effects of elevated atmospheric CO2, temperature, and drought on the abundance of active ammonia-oxidizing bacteria (AOB) and archaea (AOA), comammox (CMX) Nitrospira, and nitrite-oxidizing bacteria (NOB), and on gross mineralization and nitrification rates. We found that N transformation processes, as well as gene and transcript abundances, and nitrifier community composition were remarkably resistant to individual and interactive effects of elevated CO2 and temperature. During drought however, process rates were increased or at least maintained. At the same time, the abundance of active AOB increased probably due to higher NH4+ availability. Both, AOA and comammox Nitrospira decreased in response to drought and the active community composition of AOA and NOB was also significantly affected. In summary, our findings suggest that warming and elevated CO2 have only minor effects on nitrifier communities and soil biogeochemical variables in managed grasslands, whereas drought favors AOB and increases nitrification rates. This highlights the overriding importance of drought as a global change driver impacting on soil microbial community structure and its consequences for N cycling.

Five years’ exposure of elevated atmospheric CO2 and temperature enriched recalcitrant carbon in soil of subtropical humid climate

Atmospheric CO2 and temperature levels are predicted to increase to 550 μmol mol−1 and by 2.0–4.5 °C higher than the present, respectively, by the middle of the 21st century. Our experiment was focused to study the impact of elevated atmospheric carbon dioxide (CO2) (500 ± 20 ppm) and temperature (> 2 °C than ambient) and their association on soil respiration and total organic carbon (TOC) along with its different pools such as: active pool (AP), passive pool (PP), particulate organic carbon (POC) and mineral-associated organic carbon (MOC) in 0−30 cm soil depth under field based open-top chambers for 5years (2011–2016). Elevated CO2 (eCO2), elevated temperature (eTemp) and their association (eCO2+eTemp) resulted in significant 3.09, 11.1 and 2.76 % reduction in TOC, respectively, in 0−30 cm soil depth over ambient condition. In all predicted climatic conditions, depletion of AP and POC were observed. Conversely, carbon enriched in PP and MOC. The outcome of the soil respiration study revealed that even though cumulative carbon mineralization values were lower in soil exposed to eCO2 and eTemp, under carbon depleted condition, the carbon mineralization efficiencies were higher. So, it can be concluded that in future climate scenario soil will act as a net source to atmospheric CO2 in subtropical humid climatic regions.

Responses of net assimilation rate to elevated atmospheric CO2and temperature at different growth stages in a double rice cropping system

Effects of elevated atmospheric CO2 concentration and temperature on rice dry matter accumulation vary in planting regions and cropping systems. It remains unclear how dry matter productivity responds to factorial combination of elevated CO2 and temperature in the double rice cropping system of China. Field experiments were conducted using open-top chambers (OTC) to simulate different scenarios of elevated CO2 and/or temperature for three rotations of double rice in Jingzhou, Hubei Province. Liangyou 287 and Xiangfengyou 9 were used as rice cultivar for early rice and late rice, respectively. There were five treatments: UC, paddy field without OTC covering; CK, OTC with the similar temperature and CO2 concentration to field environment; ET, OTC with 2 ℃ temperature elevation; EC, OTC with 60 μmol·mol-1 CO2 elevation; ETEC, OTC with simu-ltaneous 2 ℃ temperature elevation and 60 μmol·mol-1 CO2 elevation. We measured aboveground biomass, leaf area index (LAI) and net assimilation rate (NAR) of dry matter under different treatments. Our results showed that elevated CO2 and/or temperature had no significant effects on NAR from transplanting to jointing, increased NAR from jointing to heading, but decreased NAR from heading to maturity (except for EC treatment in early rice). Elevated CO2 and/or temperature promoted leaf area development at all growth stages, with ETEC showing the highest increase in LAI except at maturity. Warming and CO2 enrichment jointly promoted dry matter accumulation at heading, with ETEC increasing aboveground biomass by 10.3%-39.8% and 23.6%-34.4% compared with CK in early rice and late rice, respectively. At maturity of early rice, elevated temperature partly offset the positive effects of elevated CO2 on aboveground biomass, as shown by a reduction of 3.2%-14.1% under ETEC compared with EC. Contrarily at maturity of late rice, co-elevation of CO2 and temperature further increased aboveground biomass, showing a synergistic interaction. Results from regression analysis showed that warming and CO2 enrichment had positive effects on NAR at vegetative stages of double rice, while warming showed negative effects on NAR at reproductive stages. Considering the dissimilarities in growth characteristics, growing periods and ambient temperature, elevated CO2 and temperature might increase dry matter production in the Chinese double rice cropping system.