5th iLEAPS Science Conference Abstracts - B1

Abstracts – Session B1

Ozone-vegetation interactions and effects on ecosystems, agriculture and climate

B101ORAL-0069: Isoprene and acetaldehyde dominate VOC OH reactivities and Ozone production potentials in all seasons in the N.W. IGP

Vinod Kumar1, Vinayak Sinha1, Abhishek Kumar Mishra1

1Indian Institute of Science Education and Research Mohali, Mohali, Punjab, India

High surface ozone is a critical environmental issue in the Indo-Gangetic Plain (IGP) due to frequent exceedance events (> 60% annually) for the 8h average national ambient air quality standard. The reactive VOC precursors of ozone are poorly understood due to absence of their measurements covering seasonality and diel variability over the Indian region. We report the first year-long high temporal resolution dataset of 23 rarely quantified VOCs measured with a PTR-MS at a regionally representative suburban site in the IGP. The measurements were used to characterize the diel and seasonal variability, OH reactivity and ozone formation potential (OFP). Top seven VOCs in terms of their annual average measured concentrations are methanol (32.2 ppb), acetaldehyde (5.9 ppb), acetone (5.6 ppb), toluene (2.3 ppb), C-8 aromatics (1.7 ppb), benzene (1.6 ppb) and isoprene (1.5 ppb). High mixing ratio of isoprene is observed throughout the year with the maximum during clean post monsoon (2.3 ppb) and minimum during winter (1.1 ppb). The maximum calculated OH concentration ranges from 2.7×106 molecules cm-3 (winter) to 6.6×106 molecules cm-3 (summer) and were used for calculation of OFP. The average of peak daytime (11:00 - 14:00 L.T.) OFP for different seasons ranges between 10.2 ppb h-1 in winter and 31.3 ppb h-1 in the clean post monsoon. Crop residue fires cause an enhancement of 7.5 ppb h-1 in the summertime OFP. Isoprene and acetaldehyde are the most important VOCs contributing towards the daytime VOC OH reactivity and ozone formation potential, together accounting for > 38% of the total throughout the year. Ozone production regime is not always limited by availability of NOx but varies in response to seasonal emissions and meteorology. Isoprene and acetaldehyde are rarely quantified over Indian region and their measurements should be made a priority for robust ozone mitigation efforts.

B102 -ORAL-0319: Ozone desposition and reactivity on soil surfaces

Raluca Ciuraru, Florence Lafouge, Céline Decuq, Brigitte Durand, Olivier Fanucci, Jean-Christophe Gueudet, Sophie Genermont, Benjamin Loubet

Agricultural lands occupy about 40-50% of the Earth’s land surface. In order to assess the potential of agricultural ecosystems acting as a source or sink for ozone and biogenic volatile organic compounds (BVOC), it is necessary to determine the emissions and deposition at soil-atmosphere interface.
Although the role of the vegetation in these processes has been extensively studied, the role of soil and soil organic matter content has been less studied. BVOCs play a key role in tropospheric chemistry contributing to the formation of secondary pollutants like ozone. Ozone is of major importance in tropospheric chemistry, at high concentrations near the surface being harmful to humans and vegetation. Understanding the interactions of ozone at soil surfaces will then improve our knowledge of the ozone budget. Generally, the ozone deposition is quantified via above-canopy measurements but such observations provide little information concerning the underlying sources and sinks. Stomatal fluxes generally account for 30–70% of the observed above-canopy ozone flux while the “non-stomatal” ozone budget has been assigned to physical and chemical processes, i.e. surface reactions or gas-phase reactions with BVOCs1.
This study investigates the ozone uptake and deposition on soil surfaces using a soil chambers method and a high sensitivity proton transfer reaction mass spectrometer. Preliminary results showed that the reactions of ozone at this interface occur via two simultaneous mechanisms: a heterogeneous reaction strictly on the surface and a homogeneous reaction occurring in the gas phase. The relative rates of these two processes will be presented and discussed. The impact of cattle slurry spreading on soil surface will also be presented and discussed.

B103ORAL-0101: Ozone-vegetation interactions in the Earth system: implications for air quality and climate

Mehliyar Sadiq1, Amos P. K. Tai1, Danica Lombardozzi2, Maria Val Martin3

1Earth System Science Programme, Faculty of Science, The Chinese University of Hong Kong, Shatin, Hong Kong 2Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, Colorado, The United States of America 3Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, United Kingdom

As a harmful air pollutant, surface ozone has damaging effects not only on human health, but also on vegetation growth. Changes in plant activities (e.g., photosynthesis and stomatal conductance) in response to rising ozone damage would in turn modify many land-atmosphere processes (e.g., evapotranspiration, dry deposition, biogenic emissions), with ramifications for ozone air quality and climate. Here we present results regarding ozone-vegetation interactions in a coupled atmosphere-ecosystem modelling framework. By integrating a parameterization of ozone damage on vegetation into the Community Earth System Model, we find that ozone-vegetation coupling leads to significant increases (up to 4-6 ppbv) in simulated ozone concentrations over Europe, North America and China. Reduced dry deposition velocity following ozone damage contributes to most of these increases, constituting a major positive biogeochemical feedback on ozone air quality. Enhanced isoprene emission is found to contribute to most of the remaining increases, which is mainly driven by higher vegetation temperature that results from lower transpiration. We also find that ozone-vegetation coupling modifies boundary-layer meteorology including changes in surface temperature, precipitation and humidity. Our results show that a more in depth understanding of ozone-vegetation coupling is needed to better simulate present-day and future air quality, ecosystem productivity and climate, and thereby to formulate optimal strategies to better future air quality and safeguard public health.

B104ORAL-0284: European carbon sink strength reduced by plant ozone damage

Rebecca Oliver1, Lina Mercado2, Stephen Sitch, David Simpson, Belinda Medlyn, Yan-Shih Lin, Gerd Folberth

1CEH, Wallingford, United Kingdom 2University of Exeter, Exeter, United Kingdom

The capacity of the terrestrial biosphere to sequester carbon and mitigate climate warming is governed by the ability of vegetation to remove emissions of CO2 through the process of photosynthesis. Tropospheric O3, a globally abundant and potent greenhouse gas, is however, known to damage plants, causing reductions in primary productivity, yet the impact of this gas on European vegetation and the land carbon sink is largely unknown. Despite emission control policies across Europe, background concentrations of tropospheric O3 continue to rise as a result of hemispheric transport of O3 and its precursors. We use the JULES land-surface model recalibrated for O3 impacts on European vegetation together with an improved stomatal conductance parameterization to quantify the impact of tropospheric O3, and its interaction with CO2, on gross primary productivity (GPP) and land carbon storage across Europe. We use a factorial suit of modelling experiments in scenarios run out to 2050 and show that tropospheric O3 can significantly suppress terrestrial carbon uptake across Europe over this period. The beneficial effect of increased CO2 on stomatal closure reduces O3 uptake and damage, however GPP is still reduced by 2050. Regional variations are identified with larger impacts shown for temperate Europe compared to boreal regions. These results highlight that the effects of O3 on plant physiology significantly add to the uncertainty of future trends in the land carbon sink and climate-carbon feedbacks.

B105 - ORAL-0194: Impacts of economic sector emission reductions on ozone vegetation damage, ecosystem health, and the carbon cycle

Nadine Unger1

1University of Exeter, Exeter, United Kingdom

Ozone pollution damages photosynthesis, reduces plant growth and biomass accumulation, and limits crop yields. We apply the NASA ModelE2-YIBs global chemistry-carbon-climate model to quantify the impacts of a wide range of selective emissions controls on regional land ecosystem health. The model includes a flux-based ozone plant damage scheme and the fully dynamic methane cycle. We employ anthropogenic emissions from the IIASA Greenhouse Gas and Air Pollution Interactions and Synergies (GAINS) integrated assessment model for year 2010. To inform the design of optimized air pollution-climate change policy strategies, we assess emission mitigation in different economic sectors and by individual ozone precursor type. The largest ozone vegetation damage today occurs in summer in China, the eastern U.S. and Europe, with losses in seasonal and regional NPP of up to 20%. Our new results reveal substantial differences in the impacts of emission reductions by sector and species, and the attribution of ozone vegetation damage to source emissions, across these regions.

B106ORAL-0392: From controlled exposures of crops to ozone to global predictions of impacts on food security

Gina Mills1, Katrina Sharps1, Felicity Hayes1, Harry Harmens1, David Simpson2, Hakan Pleijel3

1Centre for Ecology & Hydrology, Bangor, United Kingdom 2Chalmers University, Gothenburg, Sweden 3Gothenburg University, Gothenburg, Sweden

The air pollutant, ozone, is increasing in concentration globally, especially in rapidly developing countries, and has been predicted to pose as big a threat to food security as climate change by 2030.  Several of the world’s most important crops such as wheat, soybean, maize and rice respond to ozone pollution by decreasing vegetative growth, seed production and root growth leading to reductions in both quantity and quality of yield.  These effects are already happening at current ozone pollution levels and are a contributing factor in reducing our ability to close the “yield gap”.   For example, our controlled exposure experiments have confirmed that current African cultivars of key staple food and feed crops are sensitive to ozone concentrations found in African countries.   We have developed response functions relating crop yield and associated key crop processes to the cumulative stomatal uptake (“flux”) of ozone modelled from plant, soil and climate factors and applied these models on a global scale to predict impacts of ozone on food security.  We show that ozone is currently reducing wheat yield by 9% globally and causes a total of 49 million tonnes (Tg) of lost grain in the five biggest producing countries (China, India, USA, Russia and France).  Ozone impacts are particularly large in moist rain-fed or irrigated soils of major wheat-producing countries (e.g. USA, France, India, China and Russia). Our modelling indicates that current irrigation usage in dry climates is inadvertently compromising UN Food Security goals by increasing ozone uptake by leaf pores and exacerbating yield losses.  We also show the regions of the world where other crops such as soybean, maize and rice are being impacted by ozone.  Ways of reducing ozone effects on crops in the future are also considered, including by crop management, plant breeding and reduction in precursor emissions.

B107 ORAL-0189: Measuring and modelling ozone stomatal flux for irrigated winter wheat in the NW-Indo Gangetic Plain

Baerbel Sinha, Sukhwinder Singh, Mehrban Singh Meena, Ram Kishore Yadav

Stomatal flux based modelling of the ozone uptake followed by comparison with the established phytotoxic dose for Triticum aestivum is the most accurate way to assess ozone related crop yield losses. In this context, it is crucial to correctly estimate leaf-level stomatal conductance and evaluate the gsto model parameterization originally developed in Europe for cultivars adapted to different climatic regions.
Previous studies in the NW-Indo Gangetic Plain have estimated ozone related crop yield losses based on atmospheric ozone concentration metrics such as the average daytime ozone (M7) or the accumulated exposure over a threshold of 40 ppb (AOT40) not based on ozone stomatal fluxes and reported that Indian cultivars are more sensitive to ozone and have steeper dose-response relationships compared to European or American cultivars.
Here we present gsto field measurements from nine triticum aestivum cultivars grown as irrigated winter wheat in the state of Punjab, in the NW-IGP. All cultivars show extremely high maximum stomatal conductance. Maximum stomatal conductance (gsto max) varied between 800 mmol m-2s-1 and 1300 mmol m-2s-1 in between different cultivars and was much higher than the maximum stomatal conductance typically reported for most European wheat cultivars (typically<450 mmol m-2s-1 for winter wheat and <600 mmol m-2s-1 for spring wheat). We find that as a consequence of regular irrigation, soil water content typically remains above 15% and most cultivars maintain full stomatal opening throughout the day irrespective of the ambient water vapour pressure deficit.
Based on our field observations we conclude, that Indian triticum aestivum cultivars are not necessarily more sensitive to ozone. Under the prevalent agricultural practises (irrigation agriculture) their stomatal ozone flux is higher compared to fluxes typically seen in rain fed agriculture. As a consequence, in a fixed time window for the same AOT40 value, they reach a higher phytotoxic ozone dose POD.

B108 ORAL-0165: Screening of Egyptian wheat (Triticum Aestivum). Genotypes for tolerance against Ozone injury 

Samia Madkour1

1Damanhour University, Damanhour, Egypt

The present study was initiated as an attempt to screen commonly cultivated Egyptian wheat (Triticum aestivum) cultivars for sensitivity to O3. Screening tests yielded two sensitive genotypes: Gemeiza 11 and Sakha 93; three intermediate: Sids 12, Sids 13 and Giza 171; and two tolerant candidates: Misr 1 and Misr 2, Electrolyte leakage from leaf discs of control and O3-stressed plants was used to study the extent of membrane damage sustained by plants (5 weeks old) as a result of ozone exposure (120-150ppb) for 3 days (6h/d) in controlled environment chambers. All the cultivars studied sustained some degree of membrane damage due to O3 exposure, but membrane leakiness was more significant in the susceptible cultivars (Gemeiza 11 and Sakha 93). A close relationship was established between the intensity of visible symptoms and degradation of plant leaf chlorophyll. All the tested cultivars showed a continuous decrease in chlorophyll content throughout the course of the experiment. Chlorophyll degradation became more pronounced after the second O3 fumigation session in all the genotypes studied. Damage in the sensitive genotypes (Gemeiza 11 and Sakha 93) could be linked to an increase in stomatal apertures and extensive ozone absorbance into the leaf chamber. Those genotypes exhibited an increase in Pn throughout the experiment. On the other hand, the tolerant genotypes (Misr 1 and 2) appeared to mitigate ozone damage via an effective stomatal closure. Those genotypes showed a trend of decrease in net photosynthesis during O3 exposure sessions and a recovery of Pn levels in the absence of O3 during the time of O3 cessation. The level of net photosynthesis and the degree of stomatal opening correlated closely in these cultivars. The intermediate cultivars ( Sids13 and Giza 171) followed the trend exhibited by the sensitive genotypes, while (Sids 12) responded more like the tolerant genotypes.

B109ORAL-0252: Ozone Bioindicator Gardens: a Citizen Science project to raise awareness about ozone pollution and its effects on living systems

Danica Lombardozzi1

1National Center for Atmospheric Research, Boulder, CO, The United States of America

Unlike the protective ozone layer in the stratosphere, ground level ozone is a toxic air pollutant that impacts all living organisms. Most people – children and adults alike – do not know the different functions of ozone in the stratosphere and at ground-level. To raise public awareness of air quality concerns, we established a network of ozone bioindicator gardens at museums and other visitor centers in the U.S. Ozone bioindicator gardens contain ozone-sensitive plants that develop a characteristic visible ozone injury when exposed to high levels of ozone, which provides the general public with a real-life demonstration of the negative effects of ozone pollution through observable plant damage. We engage the public in collecting data to document the severity of visible ozone damage on the plants and teach high school students data analysis techniques to analyze the data collected from the gardens. These activities teach people about biological processes, air quality and its impacts, and data analysis techniques in an engaging manner.

B110ORAL-0274: Relationships between ozone and stomatal conductance: implications for surface ozone air quality as simulated by in a chemical transport model

Shi Han SUN1, Amos P. K. Tai2, 1

1Graduate Division of Earth and Atmospheric Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong, Hong Kong 2Earth System Science Programme, Faculty of Science, The Chinese University of Hong Kong, Shatin, Hong Kong

Surface ozone is a major secondary air pollutant that has various adverse impacts on human health and vegetation. In particular, long-term exposure to elevated ozone can induce stomatal closure, thereby causing changes in stomatal and canopy conductance (Ainsworth et al., 2012), with ramifications for both hydrometeorology and atmospheric composition. For instance, vegetation affects ozone concentration itself through dry deposition, which is controlled by stomatal conductance (Fowler et al., 2001; Wild, 2007). The Farquhar-Ball-Berry model has been widely used to compute photosynthesis and stomatal conductance in many ecosystem and atmospheric models (Ran et al., 2017). Responses of stomatal conductance to cumulative ozone uptake (CUO) has also been recently incorporated into such models as the Community Land Model (CLM) (Lombardozzi et al., 2015). In this study, we use an asynchronous coupling framework using CLM and the Global Earth Observing System CHEMistry (GEOS-Chem) global 3-D model to evaluate how ozone-stomata interaction could impact GEOS-Chem simulated ozone. Damage of CUO on stomata is evaluated using CLM with the ozone damage scheme implemented in CLM by Lombardozzi et al. (2015). The Plant Functional Type (PFT) specific Leaf Area Index (LAI) is used as a linkage between CLM and GEOS-Chem. CLM simulated land surface datasets including PFT-Specific LAI and land types with and without ozone damage scheme are imported into GEOS-Chem for ozone simulations. With the ozone damage scheme implemented in CLM, ozone simulated by GEOS-Chem is about 5%-10% higher than previously in summer (JJA). High ozone increases appear in the tropics and high latitudes, mainly due to ozone damage on vegetation, especially for evergreen trees, grasses and crops. The results indicate considerable impacts of ozone-vegetation interactions on both surface ozone concentrations and vegetation, suggesting the need to consider ozone-vegetation interactions in climate models and implement an accurate ozone damage scheme in current GEOS-Chem.

B111POSTER-0078: Quantify the impact of ozone on crops productivity using land surface model

Felix Leung1

1University of Exeter, Exeter, United Kingdom

Tropospheric ozone (O3) is the third most important anthropogenic Greenhouse Gas and is detrimental to plant productivity. Ozone already causes significant crop production losses (5 Billion $ per year in US, similar in EU) with concentrations increasing in South Asia and South East Asia, which have significant agricultural areas and large, growing populations. The aim of this research is to quantify the impacts of present-day and future tropospheric O3 on crop production at the regional scale until 2100, using the Joint UK Land Environment Simulator adapted to include the major global crop types (JULES-crop). JULES forms the land surface component of the latest generation Earth System Model (ESM) at the Hadley Centre. Partnership with the Met Office allow me to consider the impacts of tropospheric O3 on crop production, land biogeochemistry and biophysics in an Earth System context, in a fully consistent manner.
A major focus of this research will be to further develop and apply JULES-crop to include O3 impacts on crops. JULES-crop will be extensively evaluated against the Soybean Free-Air-Concentration-Enrichment experiment (http://soyface.illinois.edu/ ). JULES-crop will be applied in a coupled ESM to quantify feedbacks between coupled climate-crops and atmospheric chemistry. The project will thus help to build a state-of-the-art impact assessment model, and contribute to a more complete understanding of the impacts of climate change on food production.

B112POSTER-0221: How carbon dioxide can offset ozone-induced crop reduction under future climate?

Yat Sing Pang1, Amos P. K. Tai2, 1

1Graduate Division of Earth and Atmospheric Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong, China 2Earth System Science Programme, Faculty of Science, The Chinese University of Hong Kong, Shatin, Hong Kong

World population is expected to increase by about 40 % to 9.7 billion by 2050 and food production must be increased by 70% in order to fulfill future food demand. However, food security is threatened by worsening ozone (O3) pollution problem under future climate scenarios. Ozone is a strong oxidizing gas that has adverse impacts on photosynthesis and crop growth. Reduction of crop yields depends on how much ozone is taken up, which is determined by the openness of leaf pores called stomata, as measured by the stomatal conductance (gs). Rising CO2 concentration under future climate can help offset crop damage from ozone both by increasing photosynthetic rate, and by decreasing stomatal conductance to reduce water loss and thus reducing ozone uptake as a result. Rising CO2 can hence substantially ozone-crop interactions. It is important to have a more realistic crop production projection by considering how CO2 can modify crop physiology in order to understand how food security is threatened under future climate change. In this study, we implement a semi-empirical parameterization of ozone damage in a mechanistic crop growth model in the Community Earth System Model to examine the interactive effects of ozone and CO2 on crop production. We first simulate crop production under near-present-day 370 ppm CO2 concentration and year-2000 ozone concentration as the baseline scenarios. By perturbing ozone concentration, the relationship of crop with different ozone concentrations (e.g., +20%, +40% of year-2000 concentration) is obtained. The relationship is then reevaluated with different CO2 concentration (e.g. 420 ppm, 525 ppm) and find that higher CO2 concentration generally reduces ozone-induced crop damage by 0.08% to 0.11% for the major staple crops.

B113POSTER-0397: Modelling combined effects of ozone and climate stresses on Arctic and boreal species

Frode Stordal1, Hui Tang1, Terje K Berntsen1, Patrick Büker2, Ane V Vollsnes1

1Department of Geosciences, University of Oslo, Oslo, Norway 2Stockholm Environmental Institute, York University, York, United Kingdom

The project, OzoNorClim will investigate combined effects of ozone and climate stresses on Arctic and boreal species. Interdisciplinary research questions are addressed, combining plant ecophysiology and atmospheric physics methods. The work consists of plant physiological and mycological experiments to quantify the effects of ozone polluted air under the particular conditions in Northern areas, and feeding the new information into widely used climate and tropospheric ozone injury models. The improved models will give a better representation of the interactions between tropospheric ozone, vegetation and climate in Arctic and tundra areas, and therefore a better foundation for political decisions.
In this poster we focus on the modelling efforts in OzoNorClim. Dynamical vegetation experiments will be made globally with the Norwegian Earth System model (NorESM), with the Community Land Model (CLM) land surface scheme and regionally with WRF-CLM. Focus is on expansion of shrubs into the Arctic and boreal zone and biophysical (albedo, surface energy and moisture fluxes) and biochemical (canopy and below ground carbon budget) feedbacks, in particular their role in Arctic amplification. Next, output from the climate simulations will be used as input to DO3SE to calculate the ozone uptake in plants under future climate conditions. The resulting ozone impacts on different types of vegetation will be mapped on the vegetation changes due to climate change alone. Finally, we will include a coupled version of DO3SE and CLM in the NorESM model. We will perform experiments with the NorESM with nudging, for current climate and for future climate. This will allow us to quantify the effects on surface fluxes of energy, moisture and carbon due to the combined effect of ozone and climate change on vegetation. The simulations will provide a first order estimate of the importance of the coupled effects of ozone and climate driven vegetation changes.