New ozone-nitrogen model shows early senescence onset is the primary cause of ozone-induced reduction in grain quality of wheat

Ozone (O3) air pollution is well known to adversely affect both the grain and protein yield of wheat, an important staple crop. This study aims to identify and model the key plant processes influencing the effect of O3 on wheat protein. We modified the DO3SE-Crop model to incorporate nitrogen (N) processes, and parameterised the O3 effect on stem, leaf and grain N using O3 fumigation datasets spanning 3 years and 4 O3 treatments. Our results show the new model captures the O3 effect on grain N concentrations, and anthesis leaf and stem concentration, well. However, the O3 effect on harvest leaf and stem N is exaggerated. Further, a sensitivity analysis revealed that, irrespective of O3 treatment, accelerated senescence onset was the primary plant process affecting grain N. This modelling study therefore demonstrates the capability of the DO3SE-CropN model to simulate processes by which O3 affects N content, and thereby determines that senescence onset is the main driver of O3 reductions in grain protein yield. The implication of the sensitivity analysis is that breeders should focus their efforts on stay-green cultivars that do not experience a protein penalty when developing O3 tolerant lines, to maintain both wheat yield and nutritional quality under O3 exposure

The vulnerability of northern European vegetation to ozone damage in a changing climate. An assessment based on current knowledge

The potential vulnerability of vegetation at northern latitudes to ozone damage was assessed based on current knowledge with regard to air ozone concentrations and leaf ozone uptake as well as to plant traits affecting ozone tolerance. The focus was on the northern European arctic, alpine and northern boreal vegetation zones, with a special focus on high-altitude vegetation. In particular, we analysed if there are increasing risks for ozone impacts on northern vegetation due to high spring ozone concentrations in relation to climate change induced shifts such as e.g. an earlier start of the growing season. The current state of knowledge implies that ecosystems in the far north are not more susceptible to ozone than vegetation in other parts of Europe. Hence, we cannot advocate for a stronger reduction of ozone precursors emissions based exclusively on the ozone sensitivity of vegetation in the far north. Thus, policies designed to reduce emissions of ozone precursors to protect vegetation in other parts of Europe as well as in the entire northern hemisphere are likely to suffice to protect vegetation in northern Fennoscandia.The report describes an assessment of the potential vulnerability of far northern European vegetation to ozone damage in a changing climate. Scientists from Sweden, Norway and Finland have joined in and the assessments rely on the experience and expertise of the authors. We could not find evidence that expected changes in ozone concentrations and climate would make the northern arctic, alpine and subalpine vegetation substantially more vulnerable to ozone than other types of European vegetation

New ozone-nitrogen model shows early senescence onset is the primary cause of ozone-induced reduction in grain quality of wheat

Ozone (O3) air pollution is well known to adversely affect both the grain and protein yield of wheat, an important staple crop. This study aims to identify and model the key plant processes influencing the effect of O3 on wheat protein. We modified the DO3SE-Crop model to incorporate nitrogen (N) processes, and parameterised the O3 effect on stem, leaf and grain N using O3 fumigation datasets spanning 3 years and 4 O3 treatments. Our results show the new model captures the O3 effect on grain N concentrations, and anthesis leaf and stem concentration, well. However, the O3 effect on harvest leaf and stem N is exaggerated. Further, a sensitivity analysis revealed that, irrespective of O3 treatment, accelerated senescence onset was the primary plant process affecting grain N. This modelling study therefore demonstrates the capability of the DO3SE-CropN model to simulate processes by which O3 affects N content, and thereby determines that senescence onset is the main driver of O3 reductions in grain protein yield. The implication of the sensitivity analysis is that breeders should focus their efforts on stay-green cultivars that do not experience a protein penalty when developing O3 tolerant lines, to maintain both wheat yield and nutritional quality under O3 exposure

Tropospheric Ozone Assessment Report: present-day tropospheric ozone distribution and trends relevant to vegetation

This Tropospheric Ozone Assessment Report (TOAR) on the current state of knowledge of ozone metrics of relevance to vegetation (TOAR-Vegetation) reports on present-day global distribution of ozone at over 3300 vegetated sites and the long-term trends at nearly 1200 sites. TOAR-Vegetation focusses on three metrics over vegetation-relevant time-periods across major world climatic zones: M12, the mean ozone during 08:00–19:59; AOT40, the accumulation of hourly mean ozone values over 40 ppb during daylight hours, and W126 with stronger weighting to higher hourly mean values, accumulated during 08:00–19:59. Although the density of measurement stations is highly variable across regions, in general, the highest ozone values (mean, 2010–14) are in mid-latitudes of the northern hemisphere, including southern USA, the Mediterranean basin, northern India, north, north-west and east China, the Republic of Korea and Japan. The lowest metric values reported are in Australia, New Zealand, southern parts of South America and some northern parts of Europe, Canada and the USA. Regional-scale assessments showed, for example, significantly higher AOT40 and W126 values in East Asia (EAS) than Europe (EUR) in wheat growing areas (p < 0.05), but not in rice growing areas. In NAM, the dominant trend during 1995–2014 was a significant decrease in ozone, whilst in EUR it was no change and in EAS it was a significant increase. TOAR-Vegetation provides recommendations to facilitate a more complete global assessment of ozone impacts on vegetation in the future, including: an increase in monitoring of ozone and collation of field evidence of the damaging effects on vegetation; an investigation of the effects on peri-urban agriculture and in mountain/upland areas; inclusion of additional pollutant, meteorological and inlet height data in the TOAR dataset; where not already in existence, establishing new region-specific thresholds for vegetation damage and an innovative integration of observations and modelling including stomatal uptake of the pollutant

Concentration gradients of ozone and other trace gases in and above cereal canopies

The concentration of ozone (O3) above and within a barley canopy and a wheat canopy was studied. Compared to the concentration at 1.1 m above the ground (0.1 m above the 1 m tall canopy), the concentration within the canopy (0.3 m above ground) was typically reduced by approximately 20 % during the day and 40 % during the night for both barley and wheat, reflecting the slower mixing of air in the lower wind speeds of the night. The variation in ozone reduction in the canopy during the hours with the highest average wind speeds (11:00-16:00) could partly be explained by the effect of vapour pressure deficit on stomatal conductance. The concentration gradients of nitrogen dioxide (NO2) above and into the canopy were weaker but similar to that of O3, while the measurements suggested emission of nitric oxide (NO). During the day the carbon dioxide (CO2) concentration had a local minimum at the top of the canopy reflecting the photosynthesis activity of the sunlit, non-senescent part of the canopy, while during the night very high concentrations of CO2 were observed within and immediately above the canopy as a result of respiration in combination with limited air mixing. Inside open-top chambers no concentration gradients of O3 into the canopy or horizontally above the canopy could be detected

Air Pollution Dynamics and the Need for Temporally Differentiated Road Pricing

In this paper we investigate the effects of the temporal variation of pollution dispersion, traffic flows and vehicular emissions on pollution concentration and illustrate the need for temporally differentiated road pricing through an application to the case of the congestion charge in Stockholm, Sweden. By accounting explicitly for the role of pollution dispersion on optimal road pricing, we allow for a more comprehensive view of the economy-ecology interactions at stake, showing that price differentiation is an optimal response to the physical environment. Most congestion charges in place incorporate price bans to mitigate congestion. Our analysis indicates that, to ensure compliance with air quality standards, such price variations should also be a response to limited pollution dispersion