Introduction of high-performing crop cultivars and crop/soil water management practices that increase the stomatal uptake of carbon dioxide and photosynthesis will be instrumental in realizing the United Nations Sustainable Development Goal (SDG) of achieving food security. To date, however, global assessments of how to increase crop yield have failed to consider the negative effects of tropospheric ozone, a gaseous pollutant that enters the leaf stomatal pores of plants along with carbon dioxide, and is increasing in concentration globally, particularly in rapidly developing countries. Earlier studies have simply estimated that the largest effects are in the areas with the highest ozone concentrations. Using a modelling method that accounts for the effects of soil moisture deficit and meteorological factors on the stomatal uptake of ozone, we show for the first time that ozone impacts on wheat yield are particularly large in humid rain-fed and irrigated areas of major wheat-producing countries (e.g. United States, France, India, China and Russia). Averaged over 2010-2012, we estimate that ozone reduces wheat yields by a mean 9.9% in the northern hemisphere and 6.2% in the southern hemisphere, corresponding to some 85 Tg (million tonnes) of lost grain. Total production losses in developing countries receiving Official Development Assistance are 50% higher than those in developed countries, potentially reducing the possibility of achieving UN SDG2. Crucially, our analysis shows that ozone could reduce the potential yield benefits of increasing irrigation usage in response to climate change because added irrigation increases the uptake and subsequent negative effects of the pollutant. We show that mitigation of air pollution in a changing climate could play a vital role in achieving the above-mentioned UN SDG, while also contributing to other SDGs related to human health and well-being, ecosystems and climate change.
Page S1.Maps of hotspots 2 S2.LPJ-Guess parameters tuned for the IBS plant functional type 3 S3.Description of the reindeer grazing, browsing and trampling implementation 4-5 S4.Climate-change signal in the climate scenario 6 S5.Description of conversion of PFT LAI to vegetation classes 7-8 S6.Validation results 9-11 S7.Confusion matrixes for simulated and satellite-based vegetation classes: a. Abisko 12 b.Vindeln 13 c.Helags 14 d.Fulu 15 e.Muddus 16 f.Björnlandet 17 S8.Simulated potential reindeer consumption in Swedish reindeer-herding communities 18-19
Formation and evolution of secondary organic aerosols (SOA) from biogenic VOCs influences the Earth's radiative balance. We have examined the photo-oxidation and aging of boreal terpene mixtures in the SAPHIR simulation chamber. Changes in thermal properties and chemical composition, deduced from mass spectrometric measurements, were providing information on the aging of biogenic SOA produced under ambient solar conditions. Effects of precursor mixture, concentration, and photochemical oxidation levels (OH exposure) were evaluated. OH exposure was found to be the major driver in the long term photochemical transformations, i.e., reaction times of several hours up to days, of SOA and its thermal properties, whereas the initial concentrations and terpenoid mixtures had only minor influence. The volatility distributions were parametrized using a sigmoidal function to determine TVFR0.5 (the temperature yielding a 50% particle volume fraction remaining) and the steepness of the volatility distribution. TVFR0.5 increased by 0.3 ± 0.1% (ca. 1 K), while the steepness increased by 0.9 ± 0.3% per hour of 1 × 106 cm–3 OH exposure. Thus, aging reduces volatility and increases homogeneity of the vapor pressure distribution, presumably because highly volatile fractions become increasingly susceptible to gas phase oxidation, while less volatile fractions are less reactive with gas phase OH.
Abstract. 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. The DO3SE-Crop model was modified in this work to incorporate nitrogen (N) processes, and we parameterised the O3 effect on stem, leaf, and grain N using O3 fumigation datasets spanning 3 years and four O3 treatments. These modifications mean that the newly developed DO3SE-CropN model is the first crop model to include O3 effects on N processes, making it a valuable tool for understanding O3 effects on wheat quality. Our results show that the new model captures the O3 effect on grain N concentrations and the anthesis leaf and stem concentrations well, with an R2 of 0.6 for the increase in grain N concentration and an R2 of 0.3 for the decrease in grain N content under O3 exposure. However, the O3 effect on harvest leaf and stem N is exaggerated. Overestimations of harvest leaf N range from ∼20 % to 120 %, while overestimations of harvest stem N range from ∼40 % to 120 %. Further, a sensitivity analysis revealed that, irrespective of O3 treatment, early senescence onset (simulated as being ∼13 d earlier in the treatment with very high O3 vs. the low-O3 treatment) was the primary plant process affecting grain N. This finding has implications for the breeding of stay-green cultivars for maintaining yield, as well as quality, under O3 exposure. 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. This work supports the second phase of the Tropospheric Ozone Assessment Report (TOAR) by investigating the impacts of tropospheric O3 on wheat, with a focus on wheat quality impacts that will subsequently affect human nutrition.
Utvecklingen vad galler halterna av marknara ozon i norra Europa under de senaste drygt tjugo aren karakteriseras av att de hogsta halterna har minskat medan de lagsta och medelhoga halterna har okat. Stigande hemisfariska bakgrundshalter forklarar troligen de stigande laga till mattliga ozonhalterna.Arsmaximum av glidande 8 timmars ozonmedelhalt minskar pa ett statistiskt sakerstallt satt i sodra Sverige, men forandras ej i norra Sverige. Modellberakningar saval som trender beraknade fran observationer tyder dock pa att malvardet for det maximala 8-timmarsmedelvardet av ozonhalten, som anvands for att skydda manniskors halsa inom miljokvalitetsmalet Frisk Luft, fortsatt kommer att overskridas ar 2050.Det finns ingen statistiskt sakerstalld forandring over tid vad galler inverkan pa vaxtligheten baserat pa AOT40. AOT40 overskrider malvardet som galler preciseringen inom Frisk Luft, i sodra men inte i norra Sverige. Om de Europeiska utslappen av ozonbildande amnen till ar 2050 minskar i enlighet med framtida utslappsscenarier kommer dock malvardet till skydd for vaxtligheten baserat pa AOT40 inte langre overskridas i Sverige och inte heller i stora delar av norra Europa. Dessa scenarie-berakningar utgar dock fran att de hemisfariska bakgrundhalterna inte andras namnvart. Ozonexponeringen av vaxtligheten beraknat som ozonflux kommer i sodra Sverige dock inte att underskrida det malvarde som anvands inom LRTAP-konventionen till ar 2050. (Less)
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