Current Ambient Conditions Research Articles

Novel data-driven optimal control methods for cost-effective brine treatment

This study presents a novel data-driven optimal control method to minimize the cost of Convection-Enhanced Evaporation (CEE) systems under time-varying weather conditions. CEE is the approach of evaporating water from saline films (brine) on packed evaporation surfaces by air convection. Here, operating variables (brine injection rate, brine temperature, and air speed) are actively controlled as a function of current ambient conditions and daily weather forecast. The controller optimizes the process operation variables based on a dataset consisting of Pareto fronts, obtained in advance by solving a set of optimization problems. Three optimal operation strategies are presented: (1) real-time selection of operating variables, (2) predictive scheduled operation, and (3) hybrid wind-fan operation. The effectiveness of the proposed strategies was assessed through two case studies with distinct geographical locations and weather conditions: Alamogordo, New Mexico, and Minneapolis, Minnesota. The results show significant cost-saving potential relative to static operation. Predictive scheduled operation resulted in an annual average operating costs of $0.91/m3 and $6.63/m3 in Alamogordo and Minneapolis, respectively, with the higher costs in Minneapolis a result of the added thermal energy required to prevent freezing in winter.

The Potential Impact of Oil Spills in Coastal Waters on Water Supply in Trinidad

Oil exploration poses an inherent risk to water resources and water quality, exemplified by oil spills resulting from broken pipelines, underwater blowouts and oil transport vessel accidents. In these instances, as vulnerable to spilled oil, water is usually the first casualty, resulting in oil contaminated water. In an effort to ensure the sustainability of freshwater resources resilience in Small Island Developing States, (SIDS), desalination is increasingly used to provide potable water. Thus, oceanic oil spills are of significant relevance to the provision of a guaranteed supply of potable water. Trinidad and Tobago, an oil-producing (SIDS), with considerable oil and gas activities on land and in shallow coastal waters; can become increasingly stressed from oil spills, possibly leading to halting seawater intakes in the desalination process. A real-life seawater surface oil spill in the Gulf of Paria, south-west coast of Trinidad, not far from the largest desalination plant in the Caribbean, is investigated using numerical mathematical modelling to model the spill’s movement underwater. The trajectory plots produced and analysed, indicated that depending on key parameters of the oil and the current ambient conditions, an oil plume can travel significantly long horizontal distances underwater before destabilising. Inferences suggested that oily underwater and existing ambient conditions can potentially affect the desalination equipment. Hence, oil spill modelling is necessary to determine oil trajectory and further inform the decision-making process in determining the best location for constructing desalination plants so as to minimise disruption to the island’s domestic freshwater supply in oil spill events.

Modeling Power Constraints Using Maps and Field Data in Optimization Problems for Gas Transportation Systems

Abstract Gas transmission networks have been and continue to be the most efficient method for transporting natural gas. As hydrogen begins to emerge as one possible solution of renewable energy and starts mixing into gas networks, now more than ever, efficient operation is paramount. Part of the efficient pipeline operation puzzle is knowing how much power is available at a given compressor station, which constrains the head and flow that can be produced. In the literature, the driver is often neglected in implementations of pipeline optimization problems. This paper derives and implements driver constraints relating to gas pipeline optimization problems such as throughput maximization and consumed fuel minimization at the pipeline level. The addition of these constraints ensures that solutions are not only bounded by surge and stonewall curves as well as compressor speed, but also by available power from the driver given current ambient conditions. The modified optimization problem results in more accurate solutions of pipeline optimization problems.

A Year at the Forefront of Engineering Photosynthesis.

ABSTRACTMultiple proof-of-principle experiments and successful field trials have demonstrated that engineering photosynthesis is a viable strategy for improving crop yields. Advances to engineering technologies have accelerated efforts to improve photosynthesis, generating a large volume of published literature: this Review therefore aims to highlight the most promising results from the period February 2021 to January 2022. Recent research has demonstrated the importance of understanding the impact of changing climates on photosynthesis to ensure that proposed engineering strategies are resilient to climate change. Encouragingly, there have been several reports of strategies that have benefits at temperatures higher than current ambient conditions. There has also been success in engineering synthetic bypass pathways, providing support for the feasibility of a synthetic biology approach. Continued developments in all areas of engineering photosynthesis will be necessary for sustainably securing sufficient crop yields for the future. This article has an associated First Person interview with the first author of the paper.

Species‐specific responses to warming alter community composition

Abstract Species are responding to global climate change in varied and nuanced ways. However, how species‐specific responses to climate change= affect interactions among species remains poorly understood. It is important to understand species interactions under potential climate change scenarios because those interactions can in turn alter community dynamics. In this study, we conducted two complementary experiments to examine how simulated warming might alter larval intraguild predation (IGP) rates and resulting adult assemblage composition in three species of North American dragonflies: Pachydiplax longipennis, Plathemis lydia and Libellula luctuosa. First, using both P. longipennis and L. luctuosa, we isolated interspecific and intraspecific pairs of larval dragonflies of different size differentials to determine how the size and species identity might influence IGP rates. In tandem, we conducted a year‐long mesocosm experiment with all three species to assess how simulated warming and heat waves influenced the resulting adult dragonfly assemblages. IGP trials revealed that P. longipennis individuals were much more likely to engage in IGP than L. luctuosa, regardless of size differential. In the mesocosm experiment, emerging adult assemblages were dominated by P. longipennis individuals, a pattern that was most pronounced in the control treatment. Our results indicate that while P. longipennis may be the competitively dominant species under current ambient conditions, warming may alter this dynamic and lessen the dominance of this species on the resulting assemblage composition.

A low-temperature, meteoric water-dominated origin for smectitic clay minerals in the Chicxulub impact crater upper peak ring, as inferred from their oxygen and hydrogen isotope compositions

The peak-ring of the 66 Ma, ~180 km Chicxulub impact structure in the northern Yucatán peninsula and southern Gulf of Mexico was sampled during the International Ocean Discovery Program and International Continental Scientific Drilling Program (IODP–ICDP) Expedition 364 at Site M0077 (21.45° N, 89.95° W). Secondary clay minerals are pervasive throughout the upper peak-ring lithologies as a product of ubiquitous altered glass present throughout the impact melt and melt-bearing breccia sequence. Here we present the first detailed study of the clay mineralogy (microprobe, pXRD, spectral reflectance from 350 to 2500 nm) and isotope geochemistry (δ2H and δ18O) of the <0.2 μm size-fraction from upper peak-ring lithologies. The clay mineralogy is dominated by smectitic clay minerals, whose composition varies with stratigraphic position. Trioctahedral MgFe smectite (var. saponite) is most common in Units or Subunits 2A, 2C, 3 and 4, while a section of Subunit 2B contains a more dioctahedral, Al-rich smectite. Higher porosity regions of the lower to mid, dioctahedral smectite-dominated intervals have higher δ18O (+14.2 to +18.6‰) whereas intervals dominated by trioctahedral smectite have lower δ18O (+10.4 to +14.1‰). The range of smectite δ2H (−105 to −87‰), in comparison to that of oxygen isotopes, is proportionally much less variable and unrelated to smectite mineralogy. When combined, the oxygen and hydrogen isotope compositions of the smectitic clay minerals suggest low temperature (~20 to 50 °C) formation from meteoric water-dominated fluids. The lower end of this temperature range is below current ambient conditions, which conceivably could suggest smectite formation before much of the overlying sedimentary rocks were deposited (~56 Ma?). Calculated temperatures are generally lower than those associated with impact-generated hydrothermal alteration.Calculated δ18O and δ2H of meteoric water-dominated fluids associated with low-temperature formation of these clay minerals are lower than known for modern meteoric water in the Yucatán region. The simplest explanation for the source of these ancient fluids is meteoric water-dominated Gulf Coast brines. A more remote possibility is orogenically-driven, long-distance transport of groundwater from highlands to the east via an artesian aquifer formed in part by fractured Mesozoic rocks extending laterally beneath the impact structure.

Contrasting Responses of Arbuscular Mycorrhizal Fungal Families to Simulated Climate Warming and Drying in a Semiarid Shrubland.

We carried out a 4-year manipulative field experiment in a semiarid shrubland in southeastern Spain to assess the impacts of experimental warming (W), rainfall reduction (RR), and their combination (W + RR) on the composition and diversity of arbuscular mycorrhizal fungal (AMF) communities in rhizosphere soil of H. syriacum and G. struthium shrubs using single-molecule real-time (SMRT) DNA sequencing. Across climate treatments, we encountered 109 AMF operational taxonomic units (OTUs) that were assigned to four families: Glomeraceae (93.94%), Gigasporaceae (2.19%), Claroideoglomeraceae (1.95%), and Diversisporaceae (1.92%). AMF community composition and diversity at OTU level were unaffected by the climate manipulation treatments, except for a significant decrease in AMF OTU richness in the W treatment relative to the control. However, we found a significant decrease of AMF family richness in all climate manipulation treatments relative to the control treatment. Members of the Gigasporaceae and Diversisporaceae families appeared to be highly vulnerable to intensification of heat and drought stress, as their abundances decreased by 67% and 77%, respectively, in the W + RR treatment relative to current ambient conditions. In contrast, the relative abundance and dominance of the Glomeraceae family within the AMF community increased significantly under the W + RR treatment, with Glomeraceae being the indicator family for the W + RR treatment. The interaction between warming and rainfall reduction had a significant effect on AMF community structure at family level. These findings provide new insights to help in the conservation of the soil biodiversity facing climate change in dryland ecosystems.

Probabilistic forecasting of dynamic thermal line rating with temporal correlations

Dynamic Thermal Line Rating is a technology that optimizes the utility of overhead power transmission lines by dynamically adjusting the rating according to current ambient conditions. It is often applied in discrete time intervals (i.e., the rating is updated hourly or daily) based on a rating forecast for the next period. This paper examines the effects of temporal discretization on rating prediction, discusses the importance of temporal correlations, and proposes an approach to include these correlations in a rating prediction system. It demonstrates that predictions may be biased towards extreme values if temporal correlation is not taken into account. The proposed solution to this problem is a sampling algorithm based on iterative sampling from a chain graphical model to emulate the correlations as observed in real data. This results in a set of time series samples with well-calibrated joint probability between neighbouring variables. Therefore, these samples are usable in a Monte Carlo optimization of an objective function and yield good calibration overall. The experimental evaluation shows that the dynamic rating calculated through this sampling method permits the usage of the result at its face value without the need for further calibration. It also increases the average daily rating compared to the basic quantile selection method.

Interdependence of Hygroscopic Polymer Characteristics and Drying Kinetics during Desiccant Drying and Microwave Supported Drying

Abstract Hygroscopic polymers absorb and bind water. If not dried properly, the residual moisture can cause major problems for converting and affect the product quality significantly. Therefore, an effective drying down to an acceptable moisture level is essential for a successful production. Though data sheets give recommendations for drying parameters, these do not consider the actual current moisture up-take of the plastic pellets or the current ambient conditions. This paper investigates the interdependencies of polymer characteristics, like thermal properties and molecular structure, and the drying kinetics of the respective polymers. Tests are carried out with five different polymers on a State-of-the-Art desiccant dryer. The results show that distinctive drying behaviors can be attributed to the molecular structure of the respective plastic. This is reflected by the activation energy according to Arrhenius, the diffusion coefficient and the Flory-Huggins-Parameter, all showing a positive correlation with drying speed and therefore can be used as indicators to estimate drying times. Also, an industrial scale prototype of a microwave enhanced drying system was used to investigate the effect of microwave application on the drying kinetics. Experimental results show potential for reducing the drying times needed, especially for lower temperatures of the drying air and highly hydrophilic plastics. For higher temperatures, however, the prototype could not compete with the state-of-the-art desiccant dryer, due to heat losses and inefficient tubing of the prototype. Considering this, the benefits of microwave application could be shown representatively for polyamide 6 also at higher temperatures.

Real-Time Prediction of Curing Processes using Model Order Reduction

Manifold engineering applications are directly affected by temperature. For rubber or composite curing processes, temperature distributions over time inside the compounds are crucial for chemical cross-linking reactions. Most of these reactions occur subsequently to a heating process during product cool down. Online prediction of cooling phases is performed during the actual heating process and hence, final cure status can be estimated before the actual process finishes. Therefore, mold temperatures and heating duration can be adapted in regard to current ambient conditions, and hence product quality is increased. In order to achieve longterm thermal predictions for complex product geometries, simulating nonlinear thermal finite element models is unfeasible, due to high computational effort. Hence, a prediction-model is derived from finite element analysis using matrix export, linearization, model order reduction algorithms such as rational Krylov or iterative rational Krylov and correction of operating point deviation. A special remark is given to temperature dependent boundary conditions, choice of time discretization and choice of solving algorithm, to address arising conflicting goals between execution time and simulation accuracy. Eventually, a complete process simulation is performed during the task-cycle time on a PLC control with a sufficiently high accuracy.

Do all leaf photosynthesis parameters of rice acclimate to elevated CO2, elevated temperature, and their combination, in FACE environments?

Leaf photosynthesis of crops acclimates to elevated CO2 and temperature, but studies quantifying responses of leaf photosynthetic parameters to combined CO2 and temperature increases under field conditions are scarce. We measured leaf photosynthesis of rice cultivars Changyou 5 and Nanjing 9108 grown in two free-air CO2 enrichment (FACE) systems, respectively, installed in paddy fields. Each FACE system had four combinations of two levels of CO2 (ambient and enriched) and two levels of canopy temperature (no warming and warmed by 1.0-2.0°C). Parameters of the C3 photosynthesis model of Farquhar, von Caemmerer and Berry (the FvCB model), and of a stomatal conductance (gs ) model were estimated for the four conditions. Most photosynthetic parameters acclimated to elevated CO2 , elevated temperature, and their combination. The combination of elevated CO2 and temperature changed the functional relationships between biochemical parameters and leaf nitrogen content for Changyou 5. The gs model significantly underestimated gs under the combination of elevated CO2 and temperature by 19% for Changyou 5 and by 10% for Nanjing 9108 if no acclimation was assumed. However, our further analysis applying the coupled gs -FvCB model to an independent, previously published FACE experiment showed that including such an acclimation response of gs hardly improved prediction of leaf photosynthesis under the four combinations of CO2 and temperature. Therefore, the typical procedure that crop models using the FvCB and gs models are parameterized from plants grown under current ambient conditions may not result in critical errors in projecting productivity of paddy rice under future global change.

Pre-project geoecological studies for clearing of the Tikhomandritsa riverbed (Tver Region, Russia)

Pre-project geoecological studies were carried out in autumn 2015 along the entire length of the Tikhomandritsa river, in Navolok lake waters near the river source and Udomlya lake near its mouth, as well as on the territory adjacent to the river, as part of the Comprehensive Engineering Surveys. The aim of the studies was to obtain initial data to assess the current ambient conditions of the study area, as well as to develop the project of cleaning the upper stretch of the Tikhomandritsa riverbed and spillway structure construction. Water, bottom sediments and soil contamination levels were identified. It is found that the water quality in the studied water bodies belongs to the contaminated category. Bottom sediments at the upper stretch of the river up to a distance of 2.5 km from its source are pure and can be used in agriculture without restrictions. Bottom sediments samples taken at a distance of 5.5 km from the river source and its mouth contain dangerous level of coliform bacteria. Basing on the territory survey a tree and shurberry felling plan was drawn up and the volume of works of the river purification was determined. The project implementation will help to increase the river flow in dry water years, increase its self-cleaning velocity and environmental improvement of the area. In addition, the increase of water flow into Udomlya lake will provide Kalinin NPP with additional water resources for its process water supply. The conceptual scheme of this study is largely applicable for the basins of other small rivers.

An analysis of offshore wind farm SCADA measurements to identify key parameters influencing the magnitude of wake effects

Atmospheric conditions have a clear influence on wake effects. Stability classification is usually based on wind speed, turbulence intensity, shear and temperature gradients measured partly at met masts, buoys or LiDARs. The objective of this paper is to find a classification for stability based on wind turbine Supervisory Control and Data Acquisition (SCADA) measurements in order to fit engineering wake models better to the current ambient conditions. Two offshore wind farms with met masts have been used to establish a correlation between met mast stability classification and new aggregated statistical signals based on multiple measurement devices. The significance of these new signals on power production is demonstrated for two wind farms with met masts and validated against data from one further wind farm without a met mast. We found a good correlation between the standard deviation of active power divided by the average power of wind turbines in free flow with the ambient turbulence intensity when the wind turbines were operating in partial load.

Façade-integrated Massive Solar-thermal Collectors Combined with Long-term Underground Heat Storage for Space Heating

This work shows how façades of industrial buildings can be used as a heat source for a heat pump heating system. Opaque sections of the building skin are formed by façade-integrated massive solar-thermal collectors (FMSC) in order to collect solar radiation and heat from the ambient air. By means of a building-integrated long-term storage (BLTS), the heat collected during the summer period is conserved for utilization during the heating season. Depending on the current ambient conditions and the actual heat demand, different operating modes are to be applied: In part load with favorable external conditions the space heating demand is covered by direct use of the FMSC heat output. With rising heat demand and lower heat gain from ambient, heating is accomplished by a heat pump with FMSC or BLTS as heat source. With regard to architectural restrictions, FMSC surfaces have to be operated at temperatures above the dew point, avoiding formation of condensate or frost at the building surface. The performance of the system is modeled by means of TRNSYS, relying to available model types for the system components. The model of the core component, i.e. the FMSC, has been validated by a laboratory measurement. A design study has been carried out for an industrial building with a foot print of 1,300 m2 and an annual heating demand of 82,000 kWh. Key aspect of the investigation is the identification of the most efficient system composition, characterized by the required size of collector area and heat storage volume.

Testing Antarctic resilience: the effects of elevated seawater temperature and decreased pH on two gastropod species

AbstractOcean acidification has been hypothesized to increase stress and decrease shell calcification in gastropods, particularly in cold water habitats like the western Antarctic Peninsula (WAP). There is limited information on how calcified marine benthic invertebrates in this region will respond to these rapidly changing conditions. The present study investigated the effects of elevated seawater temperature and decreased pH on growth (wet mass and shell morphometrics), net calcification, and proximate body composition (protein and lipid) of body tissues in two common benthic gastropods. Individuals of the limpet Nacella concinna and the snail Margarella antarctica collected from the WAP were exposed to seawater in one of four treatment combinations: current ambient conditions (1.5°C, pH 8.0), near-future decreased pH (1.5°C, pH 7.8), near-future elevated temperature (3.5°C, pH 8.0), or combination of decreased pH and elevated temperature (3.5°C, pH 7.8). Following a 6-week exposure, limpets showed no temperature or pH effects on whole body mass or net calcification. Despite no significant differences in whole body mass, the shell length and width of limpets at elevated temperature tended to grow less than those at ambient temperature. There was a significant interaction between the sex of limpets and pH. There were no significant temperature or pH effects on growth, net calcification, shell morphologies, or proximate body composition of snails. Our findings suggest that both gastropod species demonstrate resilience to initial exposure to temperature and pH changes predicted to occur over the next several hundred years globally and perhaps sooner along the WAP. Despite few significant impacts of elevated temperature or decreased pH, any response to either abiotic variable in species with relatively slow growth and long lifespan is of note. In particular, we detected modest impacts of reduced pH on lipid allocation in the reproductive organs of the limpet N. concinna that warrants further study.

Climate change (elevated CO2, elevated temperature and moderate drought) triggers the antioxidant enzymes' response of grapevine cv. Tempranillo, avoiding oxidative damage

Photosynthetic carbon fixation (A(N) ) and photosynthetic electron transport rate (ETR) are affected by different environmental stress factors, such as those associated with climate change. Under stress conditions, it can be generated an electron excess that cannot be consumed, which can react with O₂, producing reactive oxygen species. This work was aimed to evaluate the influence of climate change (elevated CO₂, elevated temperature and moderate drought) on the antioxidant status of grapevine (Vitis vinifera) cv. Tempranillo leaves, from veraison to ripeness. The lowest ratios between electrons generated (ETR) and consumed (A(N) + respiration + photorespiration) were observed in plants treated with elevated CO₂ and elevated temperature. In partially irrigated plants under current ambient conditions, electrons not consumed seemed to be diverted to alternative ways. Oxidative damage to chlorophylls and carotenoids was not observed. However, these plants had increases in thiobarbituric acid reacting substances, an indication of lipid peroxidation. These increases matched well with an early rise of H₂O₂ and antioxidant enzyme activities, superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and catalase (EC 1.11.1.6). Enzymatic activities were maintained high until ripeness. In conclusion, plants grown under current ambient conditions and moderate drought were less efficient to cope with oxidative damage than well-irrigated plants, and more interestingly, plants grown under moderate drought but treated with elevated CO₂ and elevated temperature were not affected by oxidative damage, mainly because of higher rates of electrons consumed in photosynthetic carbon fixation.

Higher growth temperatures decreased net carbon assimilation and biomass accumulation of northern red oak seedlings near the southern limit of the species range

If an increase in temperature will limit the growth of a species, it will be in the warmest portion of the species distribution. Therefore, in this study we examined the effects of elevated temperature on net carbon assimilation and biomass production of northern red oak (Quercus rubra L.) seedlings grown near the southern limit of the species distribution. Seedlings were grown in chambers in elevated CO(2) (700 µmol mol(-1)) at three temperature conditions, ambient (tracking diurnal and seasonal variation in outdoor temperature), ambient +3 °C and ambient +6 °C, which produced mean growing season temperatures of 23, 26 and 29 °C, respectively. A group of seedlings was also grown in ambient [CO(2)] and ambient temperature as a check of the growth response to elevated [CO(2)]. Net photosynthesis and leaf respiration, photosynthetic capacity (V(cmax), J(max) and triose phosphate utilization (TPU)) and chlorophyll fluorescence, as well as seedling height, diameter and biomass, were measured during one growing season. Higher growth temperatures reduced net photosynthesis, increased respiration and reduced height, diameter and biomass production. Maximum net photosynthesis at saturating [CO(2)] and maximum rate of electron transport (J(max)) were lowest throughout the growing season in seedlings grown in the highest temperature regime. These parameters were also lower in June, but not in July or September, in seedlings grown at +3 °C above ambient, compared with those grown in ambient temperature, indicating no impairment of photosynthetic capacity with a moderate increase in air temperature. An unusual and potentially important observation was that foliar respiration did not acclimate to growth temperature, resulting in substantially higher leaf respiration at the higher growth temperatures. Lower net carbon assimilation was correlated with lower growth at higher temperatures. Total biomass at the end of the growing season decreased in direct proportion to the increase in growth temperature, declining by 6% per 1 °C increase in mean growing season temperature. Our observations suggest that increases in air temperature above current ambient conditions will be detrimental to Q. rubra seedlings growing near the southern limit of the species range.

The impact of climate change on the growth of tropical agroforestry tree seedlings

Several studies have been conducted on the response of crops to greater concentrations of atmospheric CO2 (CO2 fertilization) as a result of climate change, but only few studies have evaluated this effect on multipurpose agroforestry tree species in tropical environments. The objectives of this study were to quantify differences in growth parameters and in leaf carbon (C) and nitrogen (N) concentrations of Cedrela odorata L. and Gliricidia sepium (Jacq.) Walp. seedlings under current ambient temperature (32°C daytime, 22°C night time) and CO2 (360 ppm) (AMB); CO2 fertilization (800 ppm, 32°C daytime, 22°C night time) (fCO2); elevated ambient temperature (360 ppm, 34°C daytime, 25°C night time) (TEMP); and a combination of elevated temperature (32°C daytime, 22°C night time) and CO2 fertilization (800 ppm) (TEMPxfCO2). Results showed significant differences (P < 0.05) in seedling growth parameters (seedling height, number of stem leaves, leaf area ratio, shoot and root biomass, and shoot/root ratio) between treatments for both tree species. The greatest increases in growth parameters occurred in the TEMP and TEMPxfCO2 treatments compared to the AMB treatment for both tree species. However, growth parameters were significantly lower (P < 0.05) in the fCO2 treatment compared to that of the AMB treatment. Leaf N concentration was 1.1 to 2.1 times lower (P < 0.05) in all treatments when compared to current ambient conditions (AMB) in both tree species, but no significant changes in leaf C concentrations were observed. Results from our study suggested that fCO2 had the greatest negative impact on tree growth parameters, and leaf N concentrations were affected negatively in all treatments compared to current ambient conditions. It is expected that such changes in growth parameters and plant N content may impact the long-term cycling of nutrients in agroforestry systems.

Protection of plants from ambient ozone by applications of ethylenediurea (EDU): A meta-analytic review

A meta-analysis was conducted to quantitatively assess the effects of ethylenediurea (EDU) on ozone (O 3) injury, growth, physiology and productivity of plants grown in ambient air conditions. Results indicated that EDU significantly reduced O 3-caused visible injury by 76%, and increased photosynthetic rate by 8%, above-ground biomass by 7% and crop yield by 15% in comparison with non-EDU treated plants, suggesting that ozone reduces growth and yield under current ambient conditions. EDU significantly ameliorated the biomass and yield of crops and grasses, but had no significant effect on tree growth with an exception of stem diameter. EDU applied as a soil drench at a concentration of 200–400 mg/L has the highest positive effect on crops grown in the field. Long-term research on full-grown tree species is needed. In conclusion, EDU is a powerful tool for assessing effects of ambient [O 3] on vegetation.

Near‐term impacts of elevated CO2, nitrogen and fungal endophyte‐infection on Lolium perenne L. growth, chemical composition and alkaloid production

ABSTRACTCarbon dioxide has been rapidly accumulating in the atmosphere and is expected to continue to do so. This accumulation is presumed to have important direct effects on plant growth. The interacting affects of a small increase in CO2 concentration (466 p.p.m., approximately 30% increase from current ambient conditions), nitrogen fertilization and fungal endophyte (Neotyphodium lolii) infection on the growth and chemical composition of perennial ryegrass (Lolium perenne) were investigated. It was found that dry mass production was approximately 50% greater under elevated CO2 than under ambient CO2, but only in conditions of high soil N. High molecular weight carbohydrates and total carbohydrates (LMW + HMW CHO) depended on an interaction between CO2 and endophyte infection. Infected plants contained significantly more carbohydrate than endophyte‐free plants, and the difference was greatest in ambient CO2 conditions. Protein concentrations were also influenced by the interaction between CO2 and endophyte‐infection. Endophyte‐free plants had 40% lower concentrations of soluble protein under elevated CO2 than under ambient CO2, but this CO2 effect on soluble protein was largely absent in endophyte‐infected plants. CO2, endophyte‐infection and nitrogen interacted to influence the total chlorophyll concentration of the grass such that chlorophyll concentration was always lower in elevated CO2 but this decline was much greater in endophyte‐free plants, particularly in conditions of high soil N. In the endophyte‐infected plants, the concentrations of the pyrrolopyrazine alkaloid peramine depended on the interaction between CO2 and N fertilization such that peramine concentrations declined with increasing N at ambient CO2 but remained roughly constant across N levels at elevated CO2. A similar pattern was seen for the ergot alkaloid ergovaline. The biochemical responses of perennial ryegrass to elevated CO2 are clearly modified by the presence of endophytic fungi.